CU Energy Initiative/NREL Symposium

About Us

Themes

Links for CU Energy Initiative/NREL Symposium:

Location: Energy Initiative > Events > CU Energy Initiative/NREL Symposium > Homepage

CU Energy Initiative/NREL Symposium
Abstracts

Abstracts in PDF format

PicoScale Catalyst for Hyrogen Generation from NaBH4 for MicroFuel Cells
Raquel Peña-Alonso, Shelly Arreguin, Julia Fletcher, Giovanni Carturan, and Rishi Raj

NaBH4, a safe and high energy density source of H2 for proton-exchange-membrane fuel cell, requires a catalyst for predictable rate of hydrogen production. The catalyst often consists of clusters of a noble metal dispersed on a substrate. The surface to volume ratio of the cluster is an important parameter in the assessing catalytic efficiency, since only the atoms on the surface of the cluster are likely to be active. In this paper we show that atomic scale dispersion of Pt and Pd atoms on carbon nanotubes (CNT), functionalized with a monolayer of silicon based polymer derived ceramic, leads to the highest value for the figure of merit (~5000 L min-1 gmetal-1 MNaBH4-1) reported so far in the literature. This result was achieved with a 150 m thick CNT paper. Thinner paper produces higher rates of hydrogen generation since the CNT network traps the hydrogen bubbles generated at nanotube surfaces lying within the paper. Ultimately, thin CNT paper is expected to further increase the figure of merit by two orders of magnitude. The catalyst is robust, continuing to operate without degradation in performance for more than twenty cycles. The kinetic data are analyzed in terms of a combination of first order and zero order reactions (the slower one being rate controlling). In the present work, the first order reaction is rate controlling. The analysis provides a framework for careful analysis of hydrogen generation data, which is needed for controlling and predicting the performance of the catalyst for micro-fuel cell applications.

Development of Miniaturized Sensors for Air Pollution Components
Lars E. Kalnajs and Linnea M. Avallone
Laboratory for Atmospheric and Space Physics, UCB

Most gaseous and particulate components of air pollution are the direct or indirect result of fossil fuel burning. As the mix of energy sources changes, it will continue to be important to monitor the production, transport, and fate of pollutants such as nitrogen oxides and ozone. At present, monitoring strategies are often limited by the size, weight, and power consumption of commercially available sensors. We are undertaking a development project to miniaturize a sensor for the quantification of ambient ozone. We expect this project will lead to the creation of a device that is sufficiently lightweight and efficient that it can serve as a personal ozone exposure monitor. In this presentation, we will describe existing techniques and technologies for the measurement of ambient ozone, discuss the principle of operation for the sensor under development, and show data from some preliminary testing.

Chemical Characterization and Modeling of Advanced Materials Deposition Processes
Teresa M. Barnes, Mark R. Nimlos, Craig L. Perkins, and Sally E. Asher

Significant breakthroughs in photovoltaic technology will require the deployment of new materials and new processing techniques to make them on a large scale. NREL is beginning a collaborative effort to better understand deposition chemistry by combining the capabilities of the National Center for Photovoltaics (NCPV) and the National Bioenergy Center (NBC). The NCPV has strengths in both materials growth and characterization, while the NBC has experience with gas phase chemical analysis, thermochemical calculations, and reactive flow modeling. We are particularly interested in improving our understanding the vapor phase deposition of binary and ternary metal-oxides, II-VI semiconductors, and chalcogenides. We plan to combine chemical characterization data, theoretical calculations, in-situ process observations, and ex-situ materials characterization to create robust process models for use in scale-up and process optimization. We have several different deposition platforms including chemical vapor deposition (CVD) and reactive sputtering currently, and we plan to expand this to include liquid phase deposition techniques and UHV compatible deposition in the future. Our chemical characterization techniques include X-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), secondary Ion mass spectrometry (SIMS, ToF-SIMS), photo-ionization mass spectrometry, matrix-isolation FTIR, and in-situ optical emission spectroscopy and mass spectrometry. We also have extensive electrical and optical materials characterization facilities.

Novel Solar Photon Conversion Processes Investigated by THz Spectroscopy
Matthew C. Beard, Joseph Luther, Xin Ai, Kelly Knustsen, Randy Ellingson Garry Rumbles, and Arthur J. Nozik
Chemical and Biosciences Center, National Renewable Energy Laboratory

THz spectroscopy is a unique experimental approach that can measure the conductivity in a sample without the need to attach wires. Time-resolved THz spectroscopy (TRTS) involves photoexciting a sample to create charge carriers and subsequently probing them with a THz pulse; the temporal resolution of a TRTS experiment is ~ 0.2 ps. Thus, TRTS is a direct probe of the charge carrier production on a sub-picosecond timescale. In addition, due to the nature of pulsed THz spectroscopy both the carrier density and mobility can be extracted simultaneously. TRTS is a unique probe of the initial (ultrafast) photon-to-carrier conversion process. We have applied TRTS to two novel approaches to solar energy conversion; three-dimensional arrays of electronically coupled semiconductor nanocrystals, and ultrafast photoinduced charge separation processes in varying compositions of poly (3-hexylthiophene) (P3HT) blended with the electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM).

Metabolic Modifications in Plants as a Mechanism for Increasing Plant-derived Ethanol or Oil for Fuel Production
Sandy Berry-Lowe and M. Karen Newell
Department of Biology, UCCS, and CU Institute of Bioenergetics

Here we demonstrate a novel biological approach to increase the production of plant-derived oils or sugars (as a primary ingredient in successful ethanol production), by metabolic modifications of candidate algae or plants. This work is the result of over seven years of collaborative efforts between a plant molecular biologist and a cell biologist studying ways to promote distinct fuel production and consumption strategies that are conserved between most organisms. The fruits of these efforts are illustrated by the issuance of U.S. Patent No. 7105718 on September 12, 2006. The patent describes methods of modifying fuel metabolism in plants that increase the selective storage of oils in the plants. In our work, we used a model organism, Chlamydomonas reinhardtii, and more recently various seeds, including cucumber, soybeans, and corn, to demonstrate that distinct metabolic modifying agents can delay or promote germination in these model systems. The purpose of our work has been to increase the efficiency of production of biofuels from a broad range of algae and plants. This work has the additional advantage of stimulating the local economies as a result of increased demand for a diversity of crops that can be used as biofuels.

Atomistic Calculations of the Electronic and Optical Properties of Nanostructures
G. Bester, A. Franceschetti, A. Zunger

We calculate the electronic and the optical properties of semiconductor nanostructures such as self-assembled quantum dots or wires, colloidal quantum dots or rods, and quantum wells. Our method is atomistic, hence the nanostructures are constructed as clusters of thousands up to a few million atoms. This is different from the conventional theories that simulate the nanostructure using an effective smooth potential of high symmetry. Our method treats accurately spin-orbit coupling, band coupling (heavy-light hole), inter-valley coupling (Gamma-L-X, in k-space) and correlations through a configuration interaction treatment. It can be applied to practically any system of less than a few million atoms and has the capability to calculate the Photoluminescence spectra including polarization, Radiative lifetimes, Fine-Structure effects, Charging Energies under the influence of pressure, electric-, magnetic- or piezoelectric-fields.

Mechanistic aspects of water oxidation: towards improved solar energy conversion in photoelectrochemical cells
Roberto Bianco and James T. Hynes
Department of Chemistry and Biochemistry, University of Colorado-Boulder

The detailed mechanisms of water oxidation
2H2O --> O2 + 4H+ + 4e-

A key step in solar energy conversion in both photoelectrochemical cells and photosynthesis, are still unknown, despite considerable and continuing progress. Current understanding of the water oxidation mechanism at a Pt electrode and in Photosystem II is reviewed. Using established mechanistic features as guidance, a mechanistic hypothesis for water oxidation at a Pt electrode in aqueous solution is proposed for theoretical investigation via electronic structure methods. Extension to alternative metallic substrates in photoelectrochemical cells is sketched and the implications for their use in photoelectrochemical cells used in solar energy conversion are highlighted.

Materials based on carbon single-wall nanotubes for energy storage and conversion applications: synthesis, doping, and characterization
Jeff Blackburn, Thomas Gennett, Chaiwat Engtrakul, Timothy McDonald, Lin Simpson, Phil Parilla, Yanfa Yan, Kim Jones, Erin Whitney, Rohit Deshpande, Anne Dillon, Michael Heben

Carbon single-wall nanotubes (SWNTs) are unique one-dimensional materials with optical, electronic, and vibrational properties that depend on the nanotube diameter and chiral angle. The tunable electronic properties of SWNTs make them ideal candidates for a variety of applications including field-effect transistors, chemical sensors, photovoltaic (PV) materials, organic light-emitting diodes (OLEDs), and energy storage media. We produce SWNTs through a variety of different synthetic methods, including laser ablation, arc discharge, chemical vapor deposition (CVD), and hot-wire chemical vapor deposition (HWCVD). The chemical and structural properties of these materials may be modified by doping (e.g. with substitutional B atoms) or by decoration with metal atoms or clusters, either directly within the growth environment or after synthesis. These modifications, coupled with the choice of either semiconducting or metallic SWNTs of specific diameters and chiralities, afford nano-materials with properties that are highly tunable according to the desired application.

We have synthesized a variety of SWNT-based nano-materials, including boron-doped SWNTs and metal-SWNT nano-hybrids. These materials are characterized by a variety of spectroscopic, structural, and adsorption techniques for their suitability for energy conversion and storage applications. In particular, we will illustrate our capabilities for measuring the hydrogen storage capacities of our nano-materials with high precision and reproducibility. These measurements are essential for addressing the potential of SWNT-based materials for on-board hydrogen storage for fuel cell vehicles. We will also illustrate the characterization of boron-doped SWNTs by a variety of structural, spectroscopic, adsorption, and electrochemical techniques. These measeurements yield valuable information on the control of the opto-electronic properties of SWNTs for potential use in photovoltaics, lithium ion batteries, organic light-emitting diodes, and hydrogen storage media.

Modeling of Performance, Cost, and Financing of Concentrating Solar, Photovoltaic, and Solar Heat Systems
Nate Blair, Mark Mehos, Craig Christensen, David Mooney of NREL
Possible Collaborators: Profs. Brandemuehl and Krarti of CU Building Systems Program
View Poster

A comprehensive solar technology systems analysis model is being developed to support program planning for the U.S. Department of Energy’s Solar Energy Technologies Program (SETP) by staff at NREL. This new model will calculate the costs, finances and performance of current solar technologies including solar heat (typically solar domestic hot water), concentrating solar power, photovoltaics (PV). The primary function of the model is to allow users to investigate the impact of variations in physical, cost, and financial parameters to better understand their impact on key figures of merit. Although a variety of models already exist to examine various issues with each individual technology, this model, when fully implemented in the future, will have the capability to analyze different solar technologies (utility-scale PV vs. CSP for example) within the same interface while making use of similar cost and finance assumptions.

A central idea for this model is to have a user-friendly interface while at the same time having a detailed, accurate analysis for each of the technologies available. The underlying performance engine, which is hidden from the user, is TRNSYS, which already contains an extensive library of solar technology models. There are simple, built-in cost models or the user can access their own spreadsheet-based cost model. The financial model is an extension of an existing validated finance model.

This poster will discuss the goals and implementation of the model and present several sample results for interesting sensitivities.

Mechanical and Transport Behavior of PBI Dense Films Used for Elevated Temperature Gas Separation
Sudhir Brahmandam, Vivek P. Khare and Alan R. Greenberg
View Poster

The cost-effective application of polymeric membranes for industrial gas-separation applications require membrane materials that can operate under quite extreme environmental conditions for extended periods while providing an acceptable level of performance. New generation polymers such as polyimide and polybenzimidazole (PBI) can meet these demanding requirements. An important aspect of our development work is the recognition that polymers used in gas separation applications at elevated temperature are often subjected to the simultaneous and competing effects of compaction and plasticization, which are generally associated with a significant decline in membrane performance over time. Consequently, the overall objective of this study is to develop an appropriate methodology for making simultaneous mechanical and transport measurements in order to study compaction and plasticization. In this presentation, we report the successful development of a methodology for making such simultaneous measurements and describe initial results of systematic experiments that were conducted using PBI dense films under pressurized (3.1 MPa) N2, CO2 and He feed streams at temperatures up to 450°C. Overall, the results provide an improved understanding of the general relationship between mechanical and transport behavior at elevated temperature and provide an improved basis for materials modification strategies that optimize the long-term mechanical stability and permselectivity of polymeric membranes.

Advancement of Solar Thermal Technology
Jay Burch, NREL Center for Buildings and Thermal Systems
Michael Brandemuehl, CU Civil, Environmental, and Architectural Engineering
Moncef Krarti, CU Civil, Environmental, and Architectural Engineering

Major barriers to solar thermal applications in buildings include the high initial cost of solar thermal technology and lack of cost-effective solutions for space heating and cooling applications. The CU Civil Architectural and Environmental Engineering Department has collaborated with the NREL’s Buildings and Thermal Systems Center over the past six years, with one PhD and six MS students devoted to basic studies enabling lower-cost solar water heaters (SWH). Studies to date include: overheating protection to enable lower-cost polymer-based SWH; test-and-rate methods for innovative thermosiphon and integrated collector-storage systems; materials and systems studies for pipe freeze protection in northern climates; and systems analysis to establish the best opportunities for reducing SWH costs. In the future, CU and NREL will be collaborating on space conditioning systems, including innovative approaches to desiccant-based space cooling and annual heat energy storage that will enable systems with 100% solar fraction for water heating, space heating, and space cooling. The work will include: i) basic systems analyses to optimize/compare alternative configurations and establish the potential cost of saved energy; ii) investigation of fundamental properties of alternative liquid desiccant candidates; and iii) study and development of thin-film, vapor-permeable membranes for use in the winter heat regeneration process.

Exposure to Air Pollution from Fossil and Biomass Sources
Gregory L Brinkman, Michael P Hannigan, Jana B Milford

Studies have shown a correlation between ambient fine particulate matter (PM2.5) concentrations and both daily and long-term mortality. Fine particles are emitted by motor vehicles, power plants, biomass combustion, cooking, and other sources. Personal exposure to PM2.5 can differ significantly from ambient PM2.5. An increased understanding of the sources of PM2.5 exposure would help future researchers and policy makers estimate the benefits of reducing emissions – e.g. through use of renewable energy sources. Knowledge on the sources of PM2.5 will also help calculate intake fractions. Intake fraction is the fraction of material released from a source that is eventually inhaled. The research in this poster describes a pilot study to measure total mass, trace organics, elements, and ions in PM2.5 exposure. A receptor model will be applied to the data to estimate the sources of exposure. To qualify some uncertainties in the process, a synthetic data set was created using hypothetical subjects and published estimates of source contributions to PM2.5 exposure, and properties of the samplers and analysis techniques used to measure PM2.5 exposure. The receptor model was applied to the synthetic dataset to help understand the accuracy of determining the sources of PM2.5 exposure. Future work described in the poster includes microenvironment exposure modeling, which is another method that can be used to estimate sources of PM2.5 and intake fractions. Exposure modeling is estimating source contributions in different microenvironments and then computing overall source contributions to exposure based on time spent in each microenvironment.

Best Practices in Determining the Impacts of Municipal Programs on Energy Use, Air Quality, and Other Ancillary Costs and Benefits
Elizabeth Brown and Gail Mosey, NREL
View Poster

The National Renewable Energy Laboratory (NREL) seeks collaboration for a project to identify best practices for municipal and other local programs that result in direct and indirect impacts on energy use. This includes a wide variety of programs, including transportation demand management, residential and commercial/industrial energy demand management, green power, and air quality improvements. NREL’s Strategic Energy Analysis Center evaluates and works to understand best practices in energy program development and evaluation in a wide range of sectors and levels of government.

At the municipal scale, an example of this type of work is the evaluation and improvements associated with the City of Burbank transportation demand management program. NREL developed metrics based on extremely limited data and measured the impacts of the program in terms of offsetting gasoline use, air quality, and employee productivity resulting from the program. NREL also proposed low cost recommendations to improve data collection to measure important energy and environmental metrics for city level programs. As a next step, NREL would like to answer the following questions in collaboration with the universities, such as:

What is the overall energy and environmental benefit of municipal energy related programs?
Where is the largest potential for these programs?
Can a best practices guide for developing municipal program metrics be created and implemented for better understanding of program development and impacts?

Parabolic Trough Testing and Development
Chuck Kutscher, Judy Netter, and Hank Price, NREL
Michael Brandemuehl and Frank Burkholder, CU-Boulder

Parabolic trough collectors consist of a tracking, parabolic mirror that focuses direct solar radiation onto a receiver tube, or heat collection element (HCE). The efficiency of the collector is comprised of two parts: the optical efficiency, which indicates how much of the solar radiation striking the mirror is absorbed by the HCE and a thermal component, which represents how much heat is lost from the HCE by radiation and convection to the ambient environment. This work seeks to quantify the performance of parabolic trough collectors, with special attention paid to the HCE, and investigate higher-performance designs.

Interaction between Carbon Markets and Renewable Energy Markets
Ghita Levenstein Carroll, Ph.D. Candidate, Department of Environmental Studies
Lori Bird, Senior Energy Analyst, National Renewable Energy Laboratory
Dr. Jana Milford, Professor, Department of Mechanical Engineering
View Poster

A number of states and regions in the United States have begun to regulate carbon emissions (such as California and the states participating in the Regional Greenhouse Gas Initiative “RGGI” in New England) and are considering cap and trade programs. More than half of the states are implementing Renewable Portfolio Standards to increase the use of renewable energy. There is also a robust voluntary market for renewable energy. These programs and markets are being defined through separate and evolving policy debates, however the way each is structured directly impacts the others because of overlapping goals with respect to reducing carbon dioxide emissions. For example, the treatment of renewable energy sources under cap and trade programs for carbon may impact what claims renewable energy marketers and purchasers will be able to make about offsetting carbon dioxide emissions. Without a better understanding of the roles, limitations, and interactions of these markets and specifically renewable energy credits “RECs” and carbon credits “CCs”-the two policy tools they employ, the larger environmental and economic societal goals that these markets and tools are meant to achieve may not be fully realized. The goal of this research is to determine how these policies could be implemented to maximize societal benefits. A framework for making these decisions is being developed through a literature review and an examination of carbon regulations emerging in New England and California, the European Union, and voluntary carbon markets under the Chicago Climate Exchange.

Sustainable Energy in West Bengal, India: Achieving Social Progress through Sustainable Energy Services
Dipankar Chakravarti

Access to modern, sustainable energy services has the power to lift billions of people in the developing world out of poverty, improve health, education, and environmental sustainability, and positively impact such key issues as gender equality and infant mortality. Despite this fact, throughout the developing world a wide array of non-trivial barriers impede the deployment of renewable energy technologies. Issues such as human capacity and capital costs, commercial, regulatory and institutional environments, and sociopolitical factors frequently present significant barriers to the market uptake of such technologies. This project will use an action-orientated, interdisciplinary research program to assist poor, rural areas in West Bengal, India, in developing and deploying village-scale renewable electricity systems; and will utilize collaborative relationships already established with key Indian partners, such as the Indian Institute of Technology, Kharagpur.

The project will consist of three interrelated research modules—which will also serve as the conceptual structure of an action program: engineering; deployment; and impacts. The engineering module will develop technical innovations that reduce the capital costs and maintenance requirements associated with renewable technologies. Working in conjunction with NREL’s International Applications Center, the deployment module will analyze and develop solutions to commercial, regulatory, institutional and sociopolitical constrains to the local market uptake of the technologies produced in the engineering module. The impacts module will analyze the social impacts and indirect consequences of market uptake scenarios, with a view toward optimizing relational dynamics.

U.S. partners for this project include Leeds, College of Engineering, National Renewable Energy Laboratory, and EESI.

Optimizing Building Designs on the Path to Zero Energy

NREL: Center for Buildings and Thermal Systems
Craig Christensen, Shanti Pless, Nicholas Long, Brent Griffith, Paul Torcellini

CU: Building Systems Program
Mike Brandemuehl, Moncef Krarti, Scott Horowitz, Justin Spencer

Past experiences have shown that truly exceptional building energy performance can be achieved with integrated, whole-building design. The highest levels of performance, embodied in the Zero Energy Building (ZEB) goal, require extensive use of modeling until such building practices become commonplace. Optimization methods are needed for the next generation of analysis techniques to efficiently develop performance-based solutions to complicated system-integration design problems.
Over the past five years, researchers at CU and NREL have collaborated in developing a multi-variate, multi-objective Optimization Methodology to evaluate multiple building energy design options. This software employs a computationally efficient search technique to identify economical combinations of energy conservation strategies. Features of this approach include:

Optimal designs based on simulated energy performance and economics,
A pathway of optimal designs, ranging from current standard practice through ZEB,
Additional near-optimal solutions, to provide a set of choices rather than a single design.

The software finds these optimal designs based on discrete building options reflecting realistic construction options. For robustness, the software handles special situations involving positive or negative interactions between options. Work is underway to improve the optimization efficiency by various means.
Residential and non-residential buildings versions of software have been developed. Applications to date include program planning for the U.S. Department of Energy, assessments of the technical potential for ZEBs over a range of building types in different climates, technical support for production homebuilders and national retail chains, and design of a zero energy home for Denver Habitat for Humanity. This poster describes ongoing research efforts to develop such a tool for use in actual low-energy building projects.

Impacts of Renewable Fuel and Electricity Standards on State Economies
Karlynn Cory, Lori Bird, Elizabeth Brown, and John Brown – NREL
View Poster

The National Renewable Energy Laboratory (NREL) seeks opportunities to team with University researchers to further explore market, policy and economic analysis questions on state renewable portfolio standard (RPS) and renewable fuel standards (RFS). Markets for renewable electricity and fuel sources are expanding rapidly due to a number of state-level initiatives, including mandatory RPS and RFS policies. NREL has lead efforts supported by DOE, EPA and USDA in helping states understand renewable policy design and implementation issues. As an example, NREL provided technical and analytical support to the Western Governor’s Association (WGA) Clean and Diversified Energy Advisory Committee (CDEAC), which contributed to the Western Governors adopting a policy resolution to bring 30,000 Megawatts of clean energy on-line by 2015, increase energy efficiency 20 percent by 2020, and provide adequate transmission for the region. NREL has provided analytical and technical support to states considering RPS policies including New Mexico, Iowa, Hawaii and Pennsylvania. On the renewable fuels side, RFS policies are being adopted and/or considered across U.S. states. While only two states had RFS policies in place in 2004, 2006 has seen five additional states enacting policies and a further fourteen proposing RFS legislation. Lessons learned from RPS design and implementation will help streamline, strengthen and inform RFS policy design and implementation. NREL is interested in partnering with universities to address the following types of questions: What implementation challenges are states facing with respect to RPS requirements? Will 2% biodiesel standard have any impact, considering current ultra-low sulfur diesel requirements? What are the potential emission impacts of RFS standards and is more testing on biofuel emissions needed? Will RFS standards create market activity without penalty provisions?

A Systems Engineering Approach to Designing a Renewable Energy Power Source in Space
Presenter: Bruce Davis
Non-Presenter: Lee Peterson and Jason Hinkle

Solar space power (SSP) is a concept created in the late 1970’s to use solar panel satellites to supply energy to the ground and other spacecraft through wireless power transmission. Once implemented, this system would have the capability to provide a clean, safe and renewable energy source to supplement growing needs. In a report from the National Research Council entitled: Laying the Foundation for Space Solar Power: An Assessment of NASA's Space Solar Power Investment Strategy (2001), found that recent developments in technology have matured the SSP concept to a level where significant funding is justified for further development. The recommendations of the report were to focus existing SSP allocated funds on research the development of management processes, investing/demonstrating in key engineering challenges, and the integration of existing technologies.

The Aerospace Department, at the University of Colorado has a strong knowledge base in the areas of orbit determination, large spacecraft structures, and systems engineering. To progress the SSP concept, a model needs to be created which merges the engineering requirements of the spacecraft with a realistic management plan to focus resources and to keep the project development on a realistic timescale. From the knowledgebase within existing research at the University of Colorado, it is proposed that a study be performed which will analyze and improve the current systems engineering methods for the SSP application. These findings will better focus the engineering and development of a large scale, power generating satellite to improve the program feasibility.

Applications of pyrolysis molecular beam mass spectrometry to plant and soil science
Mark Davis, Robert Sykes, and Kim Magrini-Bair
National Renewable Energy Laboratory

Analytical pyrolysis using a combination of pyrolysis, molecular beam mass spectrometry and multivariate statistics can be a powerful method for analyzing plant cell wall composition and organic carbon in soils. NREL has developed a novel high-throughput method of screening plant cell wall chemistry using a combination of analytical pyrolysis and multivariate statistics that can be used to accurately assess plant cell wall chemistry traits. The method has also been demonstrated to provide detailed information that can be used to determine changes caused by transgenic modification, identify cell wall chemistry quantitative trait loci (QTLs), and to perform functional genomics. Results will be shown for transgenic poplar wood in which the lignin biosynthetic pathway has been altered to produce changes in lignin content and structure. The application of high throughput screening experiments to determine cell wall chemistry QTLs and unintended effects of genetic modification will be demonstrated.

Multivariate statistical analysis of the mass spectral and associated characterization data of agricultural soils from eleven Midwestern states demonstrates that carbon contained in the particulate organic matter, mineral associated, and microbial biomass soil fractions can be measured as a metric expressed as ug-g fraction/g soil. We have used this technique to assess impacts on soil organic matter (SOM)_accumulation in agricultural soils under the USDA’s Conservation Reserve Program (CRP) management and clearly show that eighteen-year old CRP soils have not yet reached native SOM or total carbon content. Additional work with forest soils subjected to periodic disturbance shows that soil chemistry, depths, and location can easily be distinguished based on mass spectral signatures.

This work has been authored by an employee or employees of the Midwest Research Institute under Contract No. DE-AC36-99GO10337 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States Government purposes.

Biomass Thermochemical Conversion Research
David C. Dayton, Thermochemical Platform Area Leader
National Bioenergy Center, National Renewable Energy Laboratory

Thermochemical conversion technology options include gasification and pyrolysis to maximize biomass resource utilization for biofuels production. The role of thermochemical conversion in future lignocellulose biorefineries is to convert low-carbohydrate or “non-fermentable” biomass resources that are not well suited to biochemical conversion.

Gasification can effectively convert a heterogeneous supply of biomass feedstock into a consistent gaseous intermediate that can be reliably converted to liquid fuels via commercially available or developing fuel synthesis processes. Biomass gasification product gas (syngas) consists mainly of CO, H2, CO2, H2O, N2, and hydrocarbons. Moderate to trace levels of minor syngas components including tars, sulfur and nitrogen species, alkali metals, and particulates influence the performance of downstream syngas conversion.

Gas cleanup and conditioning prior to fuel synthesis involves an integrated, multi-step procedure to remove unwanted impurities and adjust the syngas composition to specified level depending on the end use of the product gas. Gas cleanup usually involves removing or eliminating tars, acid gas removal, ammonia scrubbing, alkali metal capture, and particulate removal. Gas conditioning involves fine-tuning the cleaned syngas composition prior to fuel synthesis.

NREL thermochemical research funded by DOE’s Office of the Biomass Program includes studies to investigate: 1) biomass gasification and pyrolysis thermal decomposition kinetic mechanisms, 2) catalysts for gas clean up, especially for hydrocarbon and tar reforming, 3) fuels synthesis from thermochemical intermediates (syngas and pyrolysis oil), 4) pilot-scale testing and demonstration of integrated thermochemical conversion processes, and 5) process modeling and techno-economic analysis.

Recycling and Sustainable Energy
Dave Newport and Jack DeBell
Environmental Center, University of Colorado – Boulder

This poster will present research methods to evaluate recycling’s correlation to sustainable energy.

In a relatively short time period, recycling has become an established industry. Today, more paper is recycled in the U.S. than is landfilled or incinerated. Recent reports indicate competitive advantages over virgin material manufacturing throughout the supply chain.

There have also been recent efforts to quantify impacts of waste reduction and recycling on energy use and greenhouse gas (GHG) emissions. With few exceptions however, linkages between waste reduction, recycling, and GHG emissions are not readily understood by solid waste managers or officials responsible for developing Climate Change Action Plans (CCAPs). In fact, most CCAPs do not consider the climate impacts of solid waste practices.

This poster will describe the process, techniques, and data used to evaluate GHG impacts (methane emissions, energy use, and forest carbon sequestration), associated with fourteen waste reduction and disposal options. An extensive literature review and an analysis of the U.S. EPA’s Waste Reduction Model will be employed.

The results of this research could be significant. If correlations between emissions reductions and various waste management practices can be verified, decision-makers could more reliably prioritize those practices best suited for sustainable energy and climate protection. This is especially important in Colorado, whose recycling rate is among the lowest in the country.

Colorado’s health department (CDPHE), the Colorado Commission on Higher Education (CCHE), and the U.S. EPA have expressed interest in this project and, at a minimum, will contribute technical and promotional support to subsequent research.

Silicon oxynitride thin film barriers for PV packaging
Joseph A. del Cueto, Stephen H. Glick, Kent M. Terwilliger, Gary J. Jorgensen, Joel W. Pankow, Brian M. Keyes, Lynn M. Gedvilas, and F. J. Pern
National Renewable Energy Laboratory

Dielectric, adhesion-promoting, moisture barriers comprised of silicon oxynitride thin film materials (SiOxNy with various material stoichiometric compositions x, y) were applied t 1) bare and pre-coated soda-lime silicate glass (coated with transparent conductive oxide SnO2:F and/or aluminum), and polymer substrates (polyethylene terephthalate, PET, or polyethylene napthalate, PEN); plus 2) pre-deposited photovoltaic (PV) cells and mini-modules consisting of amorphous silicon (a-Si) and copper indium gallium diselenide (CIGS) thin-film PV technologies. We used plasma enhanced chemical vapor deposition (PECVD) process with dilute silane, nitrogen, and nitrous oxide/oxygen gas mixtures in a low-power (< 10 milliWatts per cm2) RF discharge at ~ 0.2 Torr pressure, and low substrate temperatures < 100°C, over deposition areas ~1000 cm2. Barrier properties of the resulting PV cells and coated-glass packaging structures were studied with subsequent stressing in damp-heat exposure at 85°C/85% RH. Preliminary results on PV cells and coated glass indicate the palpable benefits of the barriers in mitigating moisture intrusion and degradation of the underlying structures using SiOxNy coatings with thickness in the range of 100-200 nm.

New Directions in Photoprotection
Barbara Demmig-Adams, Amy M. Watson, Matthew R. Dumlao, and William W. Adams III
View Poster

Natural photosynthetic systems employ photoprotection to prevent damage from intense solar irradiation, yet some aspects of photoprotection lower the efficiency of solar energy conversion. We aim to optimize photoprotection in H2-producing microorganisms to occur at low or no cost to solar energy collection and electron transport, thereby allowing high rates of both electron transport and photoprotection for the maximization and long-term sustainability of H2 production.

The carotenoid pigment zeaxanthin can harmlessly remove all potentially hazardous reactive species generated during solar energy absorption and utilization in natural systems. We propose that different proteins (PsbS and the PsbS-related, Elip-like protein family) can direct zeaxanthin to different parts of photosynthetic membranes. We will show that different plant species vary in how much zeaxanthin (and PsbS) they accumulate under high irradiance. Furthermore, some plants employ a specialized version of photoprotection with higher and persistently maintained zeaxanthin levels and accumulation of specific PsbS-related proteins. Moreover, zeaxanthin-deficient mutants generate elevated levels of a lipid peroxidation-derived messenger that can induce e.g. programmed cell death.

We wish to explore optical assessment of zeaxanthin content in single algal cells, such as reflectance measurements currently used to assess leaf zeaxanthin content. Furthermore, we hope to evaluate the use of Elip-like proteins, of which the green algal model for H2 production, Chlamydomonas, possesses seven, to direct zeaxanthin away from the photosystem cores (where photoprotective thermal energy dissipation can lower charge separation/electron transport rates) and towards the membrane matrix to scavenge destructive reactive species (with no cost to H2 production).

Creating Baseload Wind Power Systems Using Advanced Compressed Air Energy Storage Concepts
Paul Denholm - NREL
View Poster

Electricity generation from wind is now among the lowest cost energy resource in much of the Midwestern and Western U.S. Development of very large-scale wind energy resources may require many large, long-distance transmission lines connecting remote wind energy resources to major load centers. At very large penetration, this type of development may also require utility-scale energy storage to increase the capacity factor of wind energy systems, improve the economics of long-distance transmission, and increase overall system reliability. Among the more promising sources of very large (GW scale) storage in the U.S. is compressed air energy storage (CAES). A number of studies have examined the concept of creating “baseload” wind power plants, which are functionally equivalent to a baseload fossil or nuclear plant. These baseload wind plants combine wind energy generation with a CAES system to create a power plant with a reliable capacity factor of up to 90%. The use of CAES requires both a relatively large underground storage vessel, and source of combustible fuel, typically natural gas. NREL is interested in examining the technical, economic and environmental aspects of combining wind energy with a variety of CAES concepts, including advanced fuel pathways using synfuels derived from coal or biomass, as well as non-combustion CAES technologies. Additional understanding of geologic constraints of CAES is also required.

Electronic structure characterization of materials for advanced energy needs
Dan Dessau, Fraser Douglas, and Kyle McElroy
Department of Physics, University of Colorado, Boulder
View Poster

The Dessau group focuses on direct electronic structure characterization of advanced electronic materials, using advanced synchrotron and lab-based spectroscopies including angle-resolved photoemission (ARPES) for band mapping, x-ray photoelectron spectroscopy (XPS) for elemental and core level analysis, and X-ray absorption (XAS) for the study of unoccupied states. We are also expert in ultrafast laser techniques and have laser systems spanning from the deep UV (177.5 nm) to the mid-IR (out to 18 microns in the future).

The McElroy group focuses on scan-probe microscopies to characterize the real space, electronic structure of materials, such as spectroscopic imaging Scanning Tunneling Microscopy (SI-STM), spin polarized STM, Atomic Force Microscopy (AFM) and Magnetic Force Microscopy (MFM). We are developing extensive capabilities such studies with extreme resolution and extensions to time domain studies.

Both our groups have extensive experience in the study of the electronic structure of superconductors and metal oxides, where electronic correlation effects make typical theories of the solid state less applicable. We also have experience in the study of low dimensional materials and the surfaces of solids but are interested in any collaborations where our background or experimental capabilities can make an impact.

Sunlight, Water, and III-V Nitrides for Fueling the Future
Todd Deutsch, John A. Turner, and Carl A. Koval
View Poster

The thermodynamic potential necessary to split water into hydrogen and oxygen at 25C is 1.23V. Photons with wavelengths below 1000nm can generate excited electrons and holes that have this potential difference when absorbed by a semiconductor. This means visible light (sunlight) is energetic enough to electrolyze water.

Three configurations of single-crystal III-V nitride semiconductor samples were characterized to determine their potential for photoelectrolysis.

The material criteria necessary for photoelectrochemical (PEC) hydrogen production fall into three categories. First, the band gap of the semiconductor must be able to generate the potential difference necessary to electrolyze water. Second, the valence and conduction band edges at the interface have to encompass the hydrogen and oxygen redox potentials. For these p-type samples the flatband potential must be more positive of the potential for the oxygen couple. Finally, the semiconductor must be stable in the aqueous environment in which it operates.

The first semiconductor characterized was GaAs1-x-yPyNx deposited on a GaP substrate. This material met the band gap requirement but the flatband potentials were too negative. It was also prone to corrosion. The second material, GaP1-xNx grown on GaP, also had a sufficient band gap and insufficient valence band edge energy. This material was more stable than GaAs1-x-yPyNx. The last sample set, GaP1-xNx grown on Si, demonstrated unbiased water splitting. The efficiency was low due to the inability of the nitride layer to sustain large short circuit currents. Nitrogen enhanced stability in these materials but it did not eliminate corrosion.

Water Fracture
Nate DeVault and Jack Burns

Water Fracturing Technology is the green fuel of our vehicular future. It has the potential to move the market away from a fossil-fuel based economy and lower pollution emissions from vehicles. Further applications of this equipment could be used to retrofit existing consumer vehicles as they do with LPG (liquid petroleum gas) to encourage consumers to adopt the technology rather than reject it as they have electric cars.

This highly efficient technology is a better method for extracting hydrogen from ordinary tap water than conventional electrolysis. Using this process to break apart molecules yields a higher output of thermal explosive energy. By electromagnetically priming the combustible gas ions, this small apparatus accelerates gas production and allows highly energized ions to combine during thermal ignition. This procedure prevents the formation of water molecules and releases high amounts of energy in a controlled state that's environmentally safe.

Novel Nanostructured Materials for Renewable Energy Applications
A.C. Dillon, E.S. Whitney, C.J. Curtis, C. Engtrakul, M.R. Davis, T. Su, P.A. Parilla, L.J. Simpson, J.L. Blackburn, Y. Zhao, Y-H. Kim, S.B. Zhang, M.J. Heben, R. Deshpande, A.H. Mahan and S-H. Lee
National Renewable Energy Laboratory

Nanostructured materials hold tremendous potential for next-generation renewable energy applications. For example, none of the current vehicular storage methods meet both the Department of Energy’s volumetric and gravimetric targets. Recent theoretical studies have shown that by complexing fullerenes with a transition metal, H2 (dihydrogen) ligands may be bound with binding energies appropriate for on-board vehicular storage. Experimental wet chemical approaches to complex an iron atom with two C60 fullerenes, representing a new molecule, have been demonstrated. The structure of this molecule has been determined by 13C solid-state nuclear magnetic resonance and electron paramagnetic spin resonance. The novel complex has been shown to have a unique binding site for dihydrogen molecules with the technique of temperature programmed desorption. In addition, hot-wire chemical vapor deposition (HWCVD) has been employed as an economically scalable method for deposition of crystalline tungsten oxide nanoparticles. The incorporation of these particles into porous films led to profound advancement in state-of-the–art electrochromic technologies. HWCVD has also been utilized to produce crystalline molybdenum oxide nanoparticles at high density. It is possible to fabricate large area porous films containing these MoOx nanostructures. Furthermore, these films have been tested as the negative electrode in lithium-ion batteries, and a surprisingly high and reversible capacity ranging from ~ 900 and up to 1300 mAh/g has been observed for several different films comprised of crystalline MoOx nanoparticles with slightly different morphologies. The synthesis of these novel nanostructured materials and their potential for improving hydrogen storage, EC and battery technologies will be presented.

Single Molecule Approaches to Bioenergy
Shi-You Ding, John O. Baker and Michael E. Himmel
Chemical and Biosciences Center, NREL

The major technical barrier to the commercial success of an advanced biorefinery is biomass recalcitrance, or the resistance of biomass feedstocks to the conversion of all polymers in the plant material into fermentable sugars and bioproducts. The current literature addressing the issue of biomass recalcitrance is often empirical, and does not specifically address the root causes of biomass recalcitrance at the molecular level. A systematic research strategy that integrates chemical and enzymatic engineering with advanced ultrastructure imaging technologies at the molecular level is therefore crucial to understanding the role that the structural and chemical heterogeneity of plant cell walls plays in the processes of pretreatment and subsequent enzymic hydrolysis of biomass.

It is a great challenge in general to measure behavior of individual molecules in biological systems. Recently, tremendous technical developments have made it possible to detect, identify, track, and manipulate single biomolecules in an ambient environment or even in a live cell. Single molecule approaches provide a potentially powerful way to study the variety of individual molecular processes involved in the chemical and enzymatic deconstruction of plant cell walls.

We have recently focused on developing the methodologies for the molecular-level characterization and imaging of biomass and biomass-degrading enzymes during the critical steps of pretreatment and enzyme hydrolysis. Our goal is to increase our understanding of the cell wall ultrastructure and the molecular mechanisms of the deconstructing enzymes. To this end, NREL has set up a state-of-the-art biomass surface characterization laboratory, which houses cutting edge microscopes including atomic force (AFM), total internal reflection fluorescence (TIRF), near-field scanning optical (NSOM), confocal laser scanning (CFM), environmental scanning electron (eSEM), and transmission electron (TEM) microscopy systems. These microscopy systems allow us to characterize native and thermochemically pretreated biomass materials, as well as to image biomass at high spatial and temporal resolution during the progress of enzymatic digestion. In this poster, we demonstrate high-resolution imaging of field-senesced and dilute acid treated corn stover cell walls using AFM. We also demonstrate single molecule imaging of individual T. reesei CBH I enzyme and carbohydrate-binding modules interacting with cellulose substrate. These preliminary results represent a long-term research commitment at NREL towards understanding the molecular causes of biomass recalcitrance, and then proposing ways to overcome the recalcitrance in service of bioenergy applications.

Monitoring cellulase penetration through biomass cell walls by Immuno-EM and Electron Tomography
Bryon S. Donohoe, Sridhar Viamajala, Todd B. Vinzant, and Michael E. Himmel
Chemical and Biosciences Center, National Renewable Energy Laboratory

Efficient conversion of lignocellulosic biomass into ethanol requires the complete digestion of cellulose and hemicellulose into simple sugars by cellulases and accessory enzymes. In order to afford these enzymes better access to the cellulose microfibrils within the plant cell walls, a variety of pretreatments schemes have been employed. The major goal of pretreatment is to loosen the plant cell wall matrix and enable better penetration and digestion by enzymes. We have monitored how well the major enzyme components of a biomass degrading enzyme cocktail penetrate the cell wall matrix following pretreatments of varying severity by immuno-electron microscopy. Here we demonstrate the dramatic effect pretreatment has on preparing biomass to be digested by cellulases. Dilute acid pretreatment at 100°C enabled < 3% enzyme penetration, pretreatment at 120°C allowed the enzymes to penetrate ~ 20% of the cell wall, and pretreatment at 150°C allowed 100% penetration of even thickest cell walls. We have also used electron tomography to visualize loosening of the cell wall ultrastructure in 3D and plan to eventually image the cellulases interacting with the cellulose substrate directly. Directly visualizing the penetration of enzymes into cell walls will help to fine tune existing pretreatments and develop new pretreatment strategies to overcome biomass recalcitrance to degradation.

Building a Sustainable Colorado Energy Future: Using Quality Data to Inform Strategic Energy Analysis
Kevin Doran

Colorado confronts the reality that its socioeconomic future is inextricably linked to sound sustainable energy policies. Decision-makers in Colorado—ranging from ordinary citizens, commuters, farmers, legislators, business people, and public servants—face important questions. Should we promote the development of Colorado’s oil shale resources? Should we continue to promote conventional coal-fired power plants over such alternatives as IGCC facilities? How do we formulate energy strategies that meet the targets set by Amendment 37, while simultaneously creating the foundations for moving toward more ambitious standards? As a joint effort by the Energy and Environmental Security Initiative of the University of Colorado Law School and the National Renewable Energy Laboratory, this project seeks to provide a framework of data and analysis that will guide and facilitate informed answers to such questions. The project will consist of two parts: a Colorado Energy Profile and a Draft Colorado Strategic Energy Plan.

The Profile will provide detailed energy statistics, projections and analysis for Colorado focused on renewable energy and fossil fuels; energy efficiency; energy markets and infrastructure; environmental statistics; transportation; and projections about energy supply and demand. Developed in coordination with broad stakeholder input, the Plan will provide a heuristic starting point for establishing a clear vision for Colorado’s energy future with detailed goals, objectives and near-, mid-, and long-term strategies for making that vision a reality.

Together, and as individual entities, the Profile and Plan will enable Colorado to utilize its natural resources in a way that is both economically and environmentally sustainable.

Efficient Solar Photon Conversion Based on Multiple Exciton Generation in Semiconductor Nanocrystals
Randy Ellingson

Recent experimental demonstrations of very efficient Multiple Exciton Generation (MEG) by absorption of a single photon, a process observed in colloidal semiconductor nanocrystals (NCs), open a route to enhance the efficiency of solar cells for the production of solar fuels and electricity by circumventing the normal relaxation process of phonon scattering. MEG has been observed in spherical nanocrystals (quantum dots (QDs)) of PbSe, PbS, PbTe, and CdSe, resulting in exciton quantum yields of as many as 7 excitons per absorbed photon. While a critical first step, the MEG discovery brings fundamental issues into focus as the subject of this research. This project seeks to understand the MEG mechanism, to characterize MEG in a wide variety of nanostructures, and to achieve control over efficient interfacial charge transfer and collection of photocurrent extracted from MEG-active nanocrystals. An array of ultrafast laser spectroscopy techniques are applied to understand MEG in detail and determine the influence on MEG efficiency of such parameters as electronic structure, surface chemistry, and dielectric environment. Theoretical work is also underway to explain and predict the ultra-efficient nature of the process. To understand the central problems of efficient extraction of single and multiple excitons from the NCs, this program studies exciton dissociation, charge separation, and interfacial charge transfer from NCs to adjacent electron and hole-conducting phases. By conducting these basic science investigations of the unique size-dependent properties of semiconductor NCs, we hope to underpin potential applications of nanostructured absorbers for highly efficient conversion of solar energy to chemical fuels and electricity.

Oxidation of Organic Films by OH Radicals
Tim D'Andrea, Xu Zhang, Evan Jochnowitz, Don David, Barney Ellison
Department of Chemistry & Biochemistry, University of Colorado-Boulder

We have produced beams of oOH X 2 radicals and studied the reactive scattering with hydrocarbon films. Reflection absorption infrared spectroscopy (RAIRS) is used to monitor the oxidation state of the film. Films of alkanes and alkenes are observed to react with beams OH radicals.

Molecular Structure at the Interfaces within Nanostructured Carbon Materials
Chaiwat Engtrakul, Jeff L. Blackburn, Calvin J. Curtis, Mark F. Davis, Anne C. Dillon, and Michael J. Heben
Materials Science Center, National Renewable Energy Laboratory
View Poster

We are conducting basic studies of the noncovalent bonding interactions between neat carbon single-walled nanotubes (SWNTs) and polymers or surfactants. These studies seek to provide the scientific principles for designing systems that can efficiently convert sunlight into electricity and fuels. An understanding of the interaction between carbon nanotubes and their surrounding medium is essential in order to effectively manipulate and control the degree of electronic coupling in these hybrid systems. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for analyzing molecular structure and dynamics. We determined that both high-resolution solid-state 13C and 1H-13C cross polarization (CP) NMR spectroscopies with magic-angle spinning (MAS) are efficient techniques for probing “soft interactions” with SWNTs. The local structure within the interfaces of SWNT/polymer composites and SWNT/surfactant powders was inferred from chemical shift data obtained from CP-NMR experiments. In addition, we have also used NMR to study the subsitutional boron doping of sp2 carbon sites in SWNTs and novel transition metal C60 fullerene derivatives. The results from these measurements are essential for improving renewable energy applications.

Increased Hydrogenase Activity in Green Algae using a cDNA Library Overexpression Screen
Richard Erickson

The use of hydrogen to displace nonrenewable hydrocarbon energy sources is attractive on several levels. Promising technologies are being developed that use hydrogen as an energy source for both transportation and electrical distribution purposes. Since concentrated natural reserves of hydrogen gas do not exist, most hydrogen is currently produced from hydrocarbon sources and hence, continues to contribute to greenhouse gas emissions and offers limited potential to decrease dependence on fossil fuel sources. Hydrogen production in green algae by photosynthetic oxidation of H2O under anaerobic conditions was initially described by Gaffron et.al. in the 1940’s, and has been suggested as a non-fossil fuel-dependent alternative for hydrogen production. Although key enzymes associated with algal hydrogen evolution have since been discovered, it is likely that many gene products involved in regulating this alternative metabolic pathway remain unidentified. To further elucidate details of hydrogen production in green algae, a cDNA library overexpression screen is proposed using Clamydomonas reinhardtii. Specifically, a C. reinhardtii cDNA library would be cloned in tandem with an IRES (internal ribosome entry sight)/Arg7 expression vector that is then stably expressed in the CC425 arginine auxotrophic strain. Mutants demonstrating viability in arginine deficient media will be isolated and screened for increased hydrogen production using chemochromic H2-sensor films. cDNAs from mutants demonstrating increased hydrogen production can then be identified by reverse transcriptase of the expressed mRNA, PCR amplification and DNA sequencing techniques. Results of this research will potentially identify previously unknown genes that, when overexpressed, lead to increased hydrogen production in C. reinhardtii.

Modular power electronics for renewable energy applications
Robert Erickson, Dragan Maksimovic, and Regan Zane
Department of Electrical and Computer Engineering, Colorado Power Electronics Center, University of Colorado at Boulder

Integration of power conversion electronics directly into thin-film photovoltaic panels is proposed. This would enable the development of smart residential PV roof tiles that can maximize energy capture in a multi-faceted roof structure with varied shading throughout the day,

Technical barriers include: (1) development of the necessary reactive energy storage elements that can be fabricated on a thin film panel, (2) advancement of a highly modular converter theory and technology that integrates modularity of both power conversion and control, and (3) reduction of converter capital cost per watt to the sub $0.10/watt level.

To address the technical barriers, we propose (1) to investigate ink-jet-printable electronics for fabrication of suitable energy storage reactive elements, (2) to demonstrate a new modular power conversion approach whose complexity of control scales linearly with the number of modules, and (3) to develop and integrated circuit solution to integrated thin-film PV power converters.

Our previous research results position us well for this work. We have now demonstrated a new modular power converter system for wind power applications, as well as a new power converter digital control paradigm and application-specific integrated circuit controllers for power converters, which have led to major advances in performance and reductions of cost.

Temperature Dependence of Gas Solubility Selectivity in Ionic Liquids
Alexia Finotello, Dean Camper, Jason Bara, and Richard Noble
Department of Chemical and Biological Engineering, University of Colorado at Boulder
View Poster

Ionic Liquids (ILs) are molten organic salts that posses a number of desirable properties. Negligible vapor pressures, high thermal and chemical stability, and tailored chemistry make them candidates to replace less environmentally friendly materials in a variety of applications. The versatile functionality of ILs allows for their potential usage in bulk fluid gas separation, supported liquid membranes, or polymerization into films for separations. The implementation of ionic liquid membranes could lead to improved separation of carbon dioxide from nitrogen (air) and various hydrocarbons and reduction of volatile organic compounds pollution. Results to date indicate that solubility, rather than diffusion selectivity, drives gas separations in these materials. Consequently, much attention has been given to understanding the influence of temperature on gas solubility in ILs, but perhaps the more important topic is how temperature affects solubility selectivity (mole fraction ratio of two gases). This study focused on bulk fluid solubility of carbon dioxide (CO2), methane (CH4), and nitrogen (N2) gases in [emim][Tf2N], [emim][BF4], [hmim][Tf2N], and [mmim][MeSO4] as a function of temperature. The experimental behaviors are explained in terms of a thermodynamic model that accounts for the negligible vapor of the IL as well as the low solubility of H2 and N2. The results show that solubility of CO2 decreases in all ILs, the solubility of CH4 remained constant in [emim][Tf2N] and [hmim][Tf2N] but increased in [mmim][MeSO4] and [emim][BF4], and the solubility of N2 and H2 increases as temperature increases. Also, solubility selectivity increases as temperature decreases for CO2/N2, CO2/CH4 and CO2/H2 systems.

Oriented TiO2 Nanotube Arrays for Sensitized Solar Cells: Effect of Nanostructure Order on Transport, Recombination, and Light Harvesting
Arthur J. Frank, Nathan R. Neale, and Kai Zhu
Chemical and Biosciences Center, National Renewable Energy Laboratory

In traditional dye-sensitized TiO2 solar cells (DSSCs or Grätzel cells), photoinjected electrons percolate through a random nanoparticle (NP) network before reaching the charge-collecting electrode. This tortuous conducting pathway leads to slow electron transport. Because the collection of electrons competes with their loss via recombination, high charge-collection efficiencies ( h cc ) require that transport is significantly faster than recombination. Films constructed of oriented one-dimensional nanostructures could potentially improve h cc by promoting faster transport and/or slower recombination. In this presentation, we describe the results of our study of the microstructure and the electron dynamics in DSSCs incorporating oriented TiO2 nanotube (NT) arrays prepared from electrochemically anodizing Ti foils. The anatase NTs were arranged in an approximately hexagonal closely packed array with wall thicknesses and inter-tube spacings of about 10 nm and pore diameters of about 30 nm. Although the transport times in the NT and NP films were similar, recombination was 10 times slower in the NT films, indicating that the charge-collection efficiency of the NT photoelectrodes was markedly enhanced. It was also found that the NT-based DSSCs displayed higher light-harvesting efficiencies than their NP counterparts due to stronger light-scattering effects. The solar cell properties of NT- and NP-based DSSCs were also compared.

With respect to collaborative opportunities, similar types of materials and measurements could be used for PEC hydrogen production (e.g., see poster by J. Johnson et al.), PEC electricity/storage (e.g., see posters by N. Neale et al and K. Zhu, et al.), etc.

Unique High-Resolution Measurements of Wind, Temperature, and Turbulence for Wind Energy Research
Yannick P. Meillier, Ben B. Balsley, Rod G. Frehlich, Michael L. Jensen
View Poster

Recent publications of technical reports from the Department of Energy, (DOE), the European Wind Energy Association (EWEA), as well as other studies (conference posters and presentations, journal publications) presented by independent research groups at major wind energy conferences (the European Wind energy Conference & Exhibition 2006, WindPower 2006) have identified the current Research & Development (R&D) challenges wind energy is facing and report the current progresses that have been achieved to date.

R&D priorities focus on three areas: 1) Fundamental atmospheric research (turbulence, low-level jets, boundary layer structure and dynamics) which provides the critical atmospheric inputs to calculations of structural loads for wind turbine engineering, 2) Offshore Wind Resource Assessment, 3) Efficient development of offshore windfarms.
These areas require increased efforts in fundamental research (better understanding and documentations of the marine boundary layer structure and dynamics, the origin, properties, and predictions of coherent turbulent structures such as those generated by low-level jets, gravity waves, and extreme shear. However progresses in these areas are hampered by the limitations of current technology which fails to provide high-resolution measurements of temperature and especially turbulence.

The CIRES Tethered Lifting System (TLS) provides high-resolution in situ measurements of wind, temperature, and turbulence with none of the height, resolution, and mobility restrictions of met-towers. Advanced Doppler lidar techniques provide high resolution profiles of horizontal wind and critical statistics of velocity turbulence (length scales, energy dissipation rate, true wind variance) that have the added advantage of a larger spatial average which produces the most accurate estimates.

High Resolution Numerical Wind Forecasting for Optimal Control of Wind Energy Conversion Systems
Professor Albin J. Gasiewski (CU ECE-CET), Professor Lucy Pao (CU ECE), Dr. Ed. R. Westwater (CU ECE and CIRES), and Dr. Jian-Wen Bao (NOAA/ESRL/PSD)
View Poster

Optimal control of wind turbines has been shown to be facilitated by accurate and timely forecasts of wind fields on hourly time scales. However, additional gains are possible using forecasts at spatial scales of the turbine and on time scales of the short term gust spectrum of wind. Improvements in the energy conversion rate of even a few percent by fine optimal control of turbine parameters could lead to significant economic benefits. To achieve optimal conversion we propose to investigate the extension of a state-of-the-art NOAA meso-γ scale numerical weather prediction (NWP) model to wind turbine space and time. Specifically, we will demonstrate key components of an NWP-based prediction and control system that would be updated using both global operational data and high-resolution wind measurements from a local wind profiling system. The model will account for boundary layer wind variations at subgrid scales using turbulence closure and ultimately be useable in real time at turbine sites. Assimilation of in situ, lidar-, acoustic, and radar-derived wind profiles peripheral to a turbine farm and will be studied to provide critical local model updates. Application of the system for real time wind forecasting over a ~10 km region at ~50 m horizontal, ~10 m vertical, and ~1 second model update rates is envisioned, along with optimal control of turbine azimuth, blade pitch, and torque. The project will utilize key expertise in controls, remote sensing, and numerical forecasting provided by the CU Department of Electrical and Computer Engineering, NOAA-CU Center for Environmental Technology, and NOAA Earth Systems Research Laboratory.

GIS Analysis for Renewable Energy
Ray George, Donna Heimiller, Anelia Milbrandt, Pamela Gray-Hann, Thomas Stoffel, Lan Nguyen

The NREL Geographic Information Systems (GIS) team is involved with multiple functions and projects that support the NREL mission. Among these are:

Spatial analysis of meteorological and land use data in support of renewable resource modeling (solar radiation, wind power resource, etc.)
Mapping and geospatial calculation of resource and spatial analysis of results for siting or analytical studies (e.g. Solar PV market penetration, wind energy loading of utility transmission lines).
Economic and infrastructure studies (e.g. siting of hydrogen fueling stations, considering pipeline locations, highways, etc.)
Data and product dissemination and outreach (e.g. web-based mapping tools, on-line solar and wind energy tools for residential applications)

Our biggest challenges include:

Prediction of the detailed spatial and temporal pattern of wind energy for all locations in the country;
Prediction of utility loads at high resolution corresponding to the patterns of renewable energy production
Creation of supply curves of solar, wind, and biomass energy representing current and future costs;
Dissemination of our products across the web in easy-to-use interactive applications.

We are open to collaboration with many different disciplines, including meteorology,GIS and natural resources, economics, policy analysis, engineering, and computer science.

Atomic Layer Deposition of Thin Films for Nanostructure Fabrication and Engineering
Steven M. George
Dept. of Chemistry & Dept. of Chemical Engineering, University of Colorado-Boulder

Thin films can be deposited with atomic layer control using atomic layer deposition (ALD) techniques based on sequential, self-limiting surface reactions. ALD films are remarkably conformal to the original substrate and very continuous and pinhole-free. The excellent control over film thickness and the extremely smooth and continuous film properties yield a variety of applications for nanostructure fabrication and engineering. ALD can be used to fabricate unique nanostructures such as nanolaminates. We have fabricated Al2O3/W nanolaminates using Al2O3 ALD and W ALD. We have grown various Al2O3/W nanolaminates and have examined their thermal and optical properties. We have achieved thermal conductivity values less than the minimum value of ~1 Wm-1K-1 for the best metal oxide thermal barrier coatings. We have also obtained a record x-ray reflectivity of 96.5% at λ=1.54Å.

The results indicate that Al2O3/W nanolaminates have great potential as thermal barrier coatings and x-ray mirrors. ALD can also be used in a variety of other applications such as coating particles and depositing gas diffusion barriers on polymers. We have demonstrated the fabrication of carbon nanotube coaxial cables by depositing Al2O3/W/Al2O3 nanolayers on carbon nanotubes. Very thin Al2O3 ALD layers with thicknesses ≥100Å are also observed to reduce the water vapor transmission rate through polymers over three orders of magnitude. Many potential ALD applications are on the horizon.

Photobiological Hydrogen Production – Basic and Applied Aspects of Ongoing Research
Maria L. Ghirardi1, Chris H. Chang1, Jordi Cohen3, Alexandra Dubini2, Kwiseon Kim1, Paul King1, Sergey Kosourov5, Hai Long1, Pin Ching Maness1, Matthew Posewitz2, Klaus Schulten3, Drazenka Svedruzic1, Vekalet Tek4, Anatoly Tsygankov5, Matthew Wecker2, Jianping Yu1, and Michael Seibert1

National Renewable Energy Laboratory1, Colorado School of Mines2, Beckman Institute at the University of Illinois, Urbana3, Florida International University4 and Institute of Basic Biological Problems, RAS5
View Poster

Oxygenic photosynthetic organisms such as cyanobacteria and green algae are capable of absorbing light and storing 10-13% of the incident light’s energy into the H-H bond of molecular H2. The process uses the photosynthetic apparatus of these organisms to convert sunlight into chemical potential (e.g., electrons and protons derived from water oxidation), which is then coupled to H2-gas production through the activity of two hydrogenase enzymes. Although promising, photosynthetic systems are not ready to be exploited for commercial H2 production yet. The major challenge facing these systems is the sensitivity of the H2 metabolism to O2, an obligatory by-product of photosynthetic water oxidation. This sensitivity occurs at four levels: (a) hydrogenase gene transcription, (b) hydrogenase maturation, (c) activity of the hydrogenase, and (d) competition for photosynthetic reductants. The goal of our research is to obtain a more complete understanding of this basic biochemical pathway and to implement practical solutions for the major challenges preventing commercial algal H2-production.

Our group works on fundamental projects related to the (a) maturation of the algal hydrogenase protein, (b) global algal gene expression under H2-producing conditions, (c) relationships between hydrogenase structure and catalytic activity and (d) development of biomimetic systems for coupled charge-separation and H2-production. Furthermore, we also conduct applied research, which includes: (a) molecular engineering of O2-tolerance into the hydrogenase protein; (b) expressing bacterial O2-tolerant hydrogenases in cyanobacteria and linking them to photosynthesis, and (c) optimizing a near-term system for algal H2-production based on attenuated water-oxidation activity of algal cultures subjected to nutrient stress conditions.

Support is from DOE’s EERE Hydrogen, Fuel Cells and Infrastructure Technologies Program (MLG, PCM and MS), DOE’s Office of Science BES (MLG, PK, MS) and BER (MS, MP) Divisions.

Using Genomics to Direct Strain Selections
Ryan Gill, University of Colorado

Selection is powerful yet poorly understood, which limits strain engineering efforts. We have developed a new genomics tool, SCalar Analysis of Library Enrichments (SCALES), which allows one to track the relative concentration of each of greater than 10^6 library clones, and thus to assess enrichment and dilution patterns throughout a broad range of selections. We have used this approach to improve understanding of how i) different genotypes are capable of conferring the same phenotype, ii) different phenotypes combine to contribute to overall fitness, iii) genetic adaptations that are beneficial in one environment can be costly in another (tradeoffs), and iv) selection strategy can dictate enrichments directed at the same phenotype. Based on these efforts, we began the development of a general strategy for using SCALEs to inform the development of directed strain selection strategies. We have demonstrated this approach within the context of engineering improved 3-hydroxypropionic acid (3HP) production in E. coli. A low-stringency, initial selection indicated that increased copy of carbon catabolism, transporters, or biofilm mediation genes were all capable of increasing strain fitness in the presence of inhibitory levels of 3HP. Using this information, we then redesigned our selections to enrich for transporter functions, which are more useful for strain engineering purposes as opposed to catabolic or biofilm functions. In summary, we have developed a new genomics strategy for assessing library enrichments and applied it to improve abilities to direct strain selections for the enrichment of targeted fitness altering mechanisms.

Tidal Force Generation
Aaron Gordon

The US is surrounded by miles of coastline that has abundant amounts of tidal power created by lunar/earth interactions. These predictable tides produce vast amounts of kinetic energy with underwater currents that have the ability to be harnessed through the application of off shore, sea-floor mounted generators. The use of the ocean as a truly renewable source of energy from tidal forces is a technology that has only begun to be utilized.

The idea of using tidal forces to generate power is an ancient concept that dates back to the Romans. However these generators utilize rare earth metals (such as neodymium magnets) that yield a high output of energy from the tides as they move in and out. Thorough this design of underwater generators that neither damage the coastline, harm sea life, nor pollute the surrounding environment, we hope to extract the potential power that the ocean creates.

Mapping and Measuring Social Transformation
Janet Graaff, Lecturer, Department of Management, Leeds School of Business, CU Boulder
Liane Pedersen-Gallegos, CARTSS Ethnography & Evaluation Research

We wish to gain a better understanding of how citizen, business and local government initiatives interact effectively to change collective behavior in the arena of global warming where currently the measures of effectiveness are defined in terms of in terms of carbon footprint and ecological footprint. Are these sufficient to induce collective behavioral change? What else does and will make a difference?

Research will focus on uncovering shared visions, developing measures of progress, and measuring progress for various citizen groups, business enterprises and local government initiatives separately and in interaction with one another.

Our trans-disciplinary approach combines theoretical tools from many disciplines: Institutional Economics and Ecological Economics offer analytical tools and language for institutional change; Systems Dynamics and Integral Theory provide systems maps for examining inhibitor/enabler dynamics; and Spiral Dynamics, Social Marketing and Identity Theories can be used to test the readiness and willingness of social groups to adopt new technologies and otherwise change their behavior.

The research process would include the following steps:
(a) design a dynamic interdisciplinary research frame to inform data collection and analysis
(b) collect data on carbon reduction initiatives
(c) do case studies of (i) leaders, (ii) laggers, and (iii) disinterested parties
(d) map systems, inhibitors, and enablers
(e) suggest market and policy initiatives
(f) collaborate with citizen, business, and city groups to design measures of effectiveness initiatives that purport to increase citizen participation in reducing carbon.
(g) the research process is an iterative process

Please contact us at janet.graaff@colorado.edu Subject: Energy, if you have curiosity around this project and/or would like to participate. We welcome NREL and other partners.

Material Design by Optimization: Application of Advanced Optimization Techniques to the Discovery of Novel Materials for Renewable Energy
Peter A. Graf, Wesley B. Jones, and Kwiseon Kim
National Renewable Energy Laboratory, Scientific Computing Center
View Poster

Rapid progress in both computer simulation and high throughput experimentation enables formulation of the discovery of advanced materials as an optimization process. Coupled with modern optimization techniques, a new paradigm is emerging in which simulation and/or experiment is guided by mathematics. Here we report on several examples of this approach with applications to renewable energy research.

In the area of alloy optimization by computer simulation:

An empirical pseudopotential based electronic structure code is driven by a genetic algorithm in a search for AlGaAs alloys with maximum and minimum electronic band gap.
An improved algorithm, scatter search, is applied to the same problem.
We present an enhancement--the "hydra" representation--that allows more of the possible structures to be searched at one time.

In optimization of nanostructures:

We have automated the process of passivation of simulated surfaces in the context of the empirical pseudopotential method.
We have applied a genetic algorithm to the shape optimization of nanostructures by gradual surface modification.

In the area of experiment optimization:

We have developed an open source scientific data interaction infrastructure to enable automated optimization of experiments.
Preliminary work coupling this system with response surface modeling and other experiment optimization techniques has begun.

Finally, we report on a novel multiscale optimization method for eigenvalue problems and a new project in parameter identification and optimization of metabolic models for algae-based hydrogen production. We thus demonstrate the broad applicability and significant potential of this general approach.

Organic Photovoltaic and Photoelectrochemical Cells
Brian A. Gregg, Dong Wang, and Walter Doherty III
National Renewable Energy Laboratory

Our research seeks to understand photoconversion processes in solid-state excitonic (mostly organic) semiconductors, XSCs, with the ultimate goal of creating efficient and inexpensive photoconversion systems. We study exciton transfer processes and the generation, separation and recombination of charge carriers in molecular semiconductors, particularly in self-organizing films of liquid crystalline semiconductors. Excitonic semiconductors are possible replacements for the expensive, heavy and inflexible inorganic semiconductors presently employed to transform a flux of photons into a flux of electrons. This task requires neither megaherz switching speeds nor high carrier mobility. Silicon is overkill. We hope XSCs will ultimately be a more natural fit to the problem. XSCs can be mechanistically and mathematically distinguished from conventional semiconductors like silicon. Although such differences are now becoming understood, the rational design of efficient organic photovoltaic and photoelectrochemical cells is still a matter of speculation. We propose a new type of photoelectrochemical systems in which the nanostructured XSC phase will be directly coupled to a fuel-forming catalytic phase. In principle, both phases can be optimized independently. In some ways the proposed electrode films can be considered a new type of photosynthetic mimic. BES-funded research into the first generation of photosynthetic mimics has been highly productive. But a fundamental design change, from homogeneous solution systems to lower-dimensional heterogeneous systems is required before reactants can be continuously separated from products, thus enabling true photoconversion.

A Passive Solar Manufactured House
Susanna Gross (CIRES) and Frank Evans (ATOC) University of Colorado at Boulder
View Poster

A new passive solar house design has been constructed and evaluated for two years. The design is original because it uses an ordinary double-wide manufactured house. The house is heated by exchanging air with the site-built passive solar basement. The south side of the basement is covered with glass with an area equal to 22% of the house floor area. The basement has reinforced concrete walls and gravel under the floor for thermal storage. The basement walls and floor are well insulated, while the glass is insulated at night with polyisocyanurate panels that open and close under computer control. The temperature of the house is actively controlled by a single fan which forces air up through vents that open to the basement. Backup heat is provided by a forced air propane furnace, controlled by computer. Temperature sensors in the house, basement, and outside permit computer control and detailed monitoring of the thermal performance of the system. The house was constructed in 2004 with entirely private funding. A non-solar control house was modeled with Lawrence Berkeley Laboratory's Home Energy Saver web application. The heating intensity index of the control house with the same insulation, orientation, windows and siting was 6.5 BTU/(square-foot*heating-degree-day). The real house, constructed at 8300 feet elevation in the San Luis Valley had a heating intensity index of 0.67 for the winter of 2004-2005 and 0.23 for 2005-2006, suggesting it is 90-95% solar heated.

Solar Assisted Thermodynamic Cycle
Tom Guerin, University of Colorado

Many attempts have been made over the years to harness the power of the sun. Converting the sun’s energy into electricity has been accomplished with effective but costly methods. There is a simple solution to deliver the same electricity at a fraction of the cost.

There is a thermodynamic cycle (Rankine Cycle) where a fluid is first vaporized, sent threw a turbine, condensed, and then pumped back through the system. If heat could be supplied to the vaporizer and extracted from the condenser without using the electricity generated by the turbine, more than enough energy would be created to run the pump. Thus, enough electricity would be left over as excess to power a home or anything else.

A combination of solar energy and geothermal cooling can supply sufficient energy to supplement the heat needed to make the thermodynamic cycle work. Material costs for the system would be for more affordable than current photovoltaic solar cells. Tests would need to be carried out with different working fluids to maximize efficiency. A series of mirrors, tubes, heat sinks, pumps, and generators would provide means for the cycle to produce excess electricity when sunlight is present.

Quantitative and Qualitative Flow Visualization Capabilities at CU Boulder
Jean Hertzberg, Dept. Mechanical Engineering, University of Colorado at Boulder

Flow visualization encompasses a range of techniques for making the physics of fluid flow visible. These techniques can be applied to a wide range of phenomena relevant to renewable energy, such as biomass combustion, interaction of turbine blades with a turbulent boundary layer, the flow of air over passive solar heating devices, etc. Flow visualization of these phenomena can enhance the understanding and interpretation of related data.

The Flow Visualization Laboratory at CU Boulder has a wide range of equipment and expertise available for collaborative work. Techniques range from quantitative laser-based methods such as Particle Image Velocimetry to simple photography, at scales ranging from the microscopic to convective atmospheric.

Quantum dots-mediated photo-oxidation: from solar cells to human cells
Zheng Huang, AMC Cancer Center, UCDHSC
Yong Zhang and Shengbai Zhang, Materials Science Center, NREL

Quantum dots (QDs) are attractive to a diverse range of applications from photovoltaics to biomedicine. Along with the widespread applications, a diverse array of engineered QDs has emerged, which causes a great concern of possible adverse health effects. To date, most toxicologic data are obtained from dark experiments without light irradiation which do not fully represent the potential risk of photo-induced QDs cytotoxicity. The presence of molecular oxygen and intrinsic redox potential around light-irradiated QDs might have profound effects on QDs-mediated photo-oxidatio. Oxygen derived reactive oxygen species (ROS), such as singlet oxygen (1O2), are well known to be cytotoxic and have been implicated in the etiology of a wide array of human diseases, including cancer. To date, there is very limited investigation on the possible role of ROS in QDs-mediated cytotoxicity. Photo-induced ROS production and QDs cytotoxicity deserve a further investigation. For this Seed Grant, we propose to use photo-induced 1O2 production as a valuable index for the evaluation of QDs-mediated photo-oxidation and photo-toxicity. Once produced, a molecule of 1O2 can undergo radiative decay at around 1270 nm. The time-resolved measurement of this near-infrared (NIR) emission is a reliable method for determining 1O2 lifetimes and quantum yields. As a joint research project, we will take the advantage of QDs expertise and ultrasensitive IR spectrometer at NREL to conduct a direct NIR luminescence detection of 1O2 generated by UV and visible light radiation of model QDs. The ultimate goal is to better understand, control and utilize QDs-mediated photo-oxidation.

Gap engineering of titanium dioxide for solar photocatalysis
Zheng Huang, AMC Cancer Center, UCDHSC
Yong Zhang and Shengbai Zhang, Materials Science Center, NREL

The availability of clean water and air is essential. However, most of water and air purification technologies are energy intensive. Thus, improving energy efficiency of water and air purification is vital to sustainable economic growth globally. Photocatalytic water and air purification-mediated with TiO2 and UV light introduces a revolution in cleaning technology. In order to use solar light efficiently, there is a need to develop a photocatalyst with high reactivity under visible-light. It has been suggested that one could lower the band gap of TiO2 to achieve visible-light photocatalysis by introducing impurities and/or defects, in particular by the use of nitrogen impurities. To date, the findings are controversial: while some maintain the original assessment that N indeed lowers the band gap, others suggest that N only introduces an impurity band above the valence band maximum, which may not be useful for efficient visible-light photocatalysis. Here, we propose a systemic study of band gap narrowing of TiO2 as a function of impurity properties to lay the ground for visible-light photocatalysis. We will take the advantage of modern computer facilities and computational expertise at NREL to consider a wide range of impurities - from non-metals (N), to simple metals (Mg, Sn), to transition metals (V). The single most important question to be answered through this Seed Program will be the condition to form the band-like state, oppose to the defect-like state, and how the former evolves with external parameters such as the choice of impurities, crystallographic structures, and growth parameters.

Design of an RNA-based photocell
Tadeusz Janas and Teresa Janas, University of Colorado

A positive correlation between bilayer order and RNA membrane affinity was demonstrated. RNA binding to liquid-ordered domains in sphingomyelin-cholesterol-DOPC vesicles was structure-dependent. RNA affinity to gel phase membranes was stronger, but RNA structure-independent. Both modes of RNA-membrane association were found to be electrostatic. Membrane-bound RNA broadened the gel-fluid melting transition, and reduced lipid headgroup order, as detected via fluorometric measurement of membrane dipole potential. RNA preference for membrane rafts was visualized using fluorescence and FRET microscopy. Accordingly, similar techniques also seem applicable to other RNA activities, suggesting a route to other RNA-membrane nanosystems. The goal of the proposed research is to construct a new light-harvesting nanosystem: an RNA-base photocell, which can convert light energy into electrochemical energy. The RNA binding motif for uroporphyrin will be selected, and a modular RNA containing both a porphyrin binding site, and the membrane raft – binding site will be constructed. The ability of the porphyrin-RNA complex attached to the inner liposomal surface to generate transmembrane electrochemical potential upon light illumination will be tested in the presence of asymmetrically distributed ferrous/ferric ions. The liposomal membrane will be modified by pyrylium ions as the electron carriers, to function as electronic conductor in aqueous media partaking in redox reactions at the membrane/solution interface. Thus the electrons photogenerated at the inner liposomal surface can transverse the membrane and be involved in oxidation of ferrous ions at the outer liposomal surface.

Development of a Model Compound Based Kinetic Reaction Mechanism for Lignin
Mark Jarvis, John Daily, University of Colorado at Boulder, Department of Mechanical Engineering
David Dayton, National Renewable Energy Laboratory, Golden

Highly efficient conversion of biomass to liquid fuels and industrial chemicals is key to reducing our national dependence on fossil fuel. The two primary biomass conversion options include biological and thermochemically based processes. Thermochemical methods allow the conversion of the biomass components not amenable to fermentation, i.e. lignin, by employing heat to decompose the solid polymeric feedstock and allow conversion to more useful fuels and chemicals. Despite considerable research in this area, the complex heterogeneity of lignin has prevented a detailed chemical kinetic mechanism from being developed. Our objective is to capture the essence of lignin thermal decomposition using experimental techniques to measure the kinetics of biomass samples and carefully selected model compounds combined with molecular modeling techniques to develop a detailed kinetic reaction mechanism. The goal of this mechanism is to accurately predict the products of thermochemical conversion at a given temperature, carrier gas, and residence time, so desirable products can be maximized and low-value products minimized. Presented here are preliminary data from a laminar entrained flow reactor (LEFR) for a lignin model compound and a lignin rich residue derived from simultaneous scarification and fermentation of corn stover, an overview of the molecular modeling approach, and finally a description and computational evaluation of the preliminary reaction mechanism.

Using Isothermal Titration Calorimetry as a Tool to Assay Cellulase Kinetics
Tina Jeoh, Michael E. Himmel, and William S. Adney
Chemical and Biosciences Center, National Renewable Energy Laboratory

Isothermal titration calorimetry (ITC) has potential as a powerful tool for assaying cellulase kinetics. In this poster, we begin by presenting the use of ITC for assaying homogeneous enzyme kinetics, a method that is now well documented in recent literature. We follow with a description of a study comparing cellobiase kinetics of a set of thermally stabilized Thermobifida fusca BglC (GH family 1) enzymes. Finally, we discuss the progress in employing this tool to study cellulase kinetics on cellulose.

Femtosecond lasers and microfluidics devices for biomolecular spectroscopy
Ralph Jimenez, JILA and Department of Chemistry & Biochemistry
National Institute of Standards and Technology and University of Colorado

Our laboratory is currently engaged in three main areas of research: 1) developing femtosecond nonlinear spectroscopy for investigating protein dynamics, 2) implementing these spectroscopies with high spatial resolution in microfluidics devices, and 3) simplification of the optics associated with femtosecond laser systems. Examples of work from each area and potential for collaborations will be presented.

Characterization of the Macroscopic Properties of Dilute Acid Pretreated Corn Stover
David K. Johnson, Stuart Black, Mark Davis, Claudia Ishizawa, Tina Jeoh, and Michael Himmel
National Renewable Energy Laboratory

A key barrier to the commercialization of fuels and chemicals produced from lignocellulosic biomass is the high cost and relative inefficiency of producing fermentable sugars. Dilute acid pretreatment is a promising technology for increasing the accessibility of cellulose to enzymatic hydrolysis. A better understanding of the interaction of enzymes with pretreated biomass is needed so that the rate and yields of sugars can be increased. Consequently, we continue to study the relationship between pretreatment conditions and the chemical and structural changes occurring in biomass during pretreatment. The purpose of this work was to uncover the macroscopic properties that have the greatest influence in determining the enzymatic digestibility of cellulose in dilute sulfuric acid pretreated corn stover. We have characterized a large set of samples from two sources; NREL’s pilot-scale vertical reactor, and a batch reactor operated under organosolv conditions where both xylan and lignin are removed. All samples were treated at relatively high severities effecting >70% xylan removal. A variety of methods were used to measure the crystallinity, particle size, porosity, and cellulose reducing end group concentrations of the samples. Correlations between changes in these characteristics and the digestibilities of the samples were then examined.

Novel photophysics and tandem device designs for solar hydrogen production
Justin Johnson

The efficient production of hydrogen from water using solar photoelectrochemical devices has represented a unique and important challenge to researchers for many years. Early progress in the field has not necessarily translated into continued advancement toward efficient and reliable hydrogen-producing devices today. Our goal recently has been to develop and test new designs of water-splitting cells that capture a larger portion of the solar spectrum and have the ability to produce considerably higher solar-to-hydrogen efficiences than earlier designs. Moreover, these cells are designed to utilize newly developed photophysical properties of molecules and quantum dots to increase further the attainable solar-to-hydrogen efficiency. In addition to device concepts and initial results, we describe our efforts toward understanding one of the novel charge-multiplication concepts in molecules (called singlet fission), which holds great promise for increasing hydrogen yields beyond previous limits.

Measuring Minority-Carrier Lifetime by Photoconductive Decay at NREL
Steve Johnston, NREL
View Poster

Minority-carrier lifetime provides a measure of material quality and is therefore a useful and informative characterization tool used by the Si photovoltaic industry. The lifetime measurement must evolve as industry shifts to using lesser quality feedstock, thinner wafers, and multi-crystalline wafers and ribbons. Lifetime scanning and mapping is becoming important in order to detect non-uniformities and process irregularities. We are working to develop an improved understanding of the currently available techniques for measuring the minority-carrier lifetime of multi-crystalline Si. Some of the issues involved that we plan to address at NREL are the following: the effect of injection level in microwave reflection, the effect and need for surface passivation, and how microwave reflection lifetime compares to other techniques such as Sinton quasi-static photoconductivity, resonant-coupled photoconductive decay, surface photo-voltage, dislocation density, diffusion length, and photoluminescence imaging. This work involves experimental measuring and theoretical modeling to address known but poorly understood issues of lifetime with respect to topics such as grain boundaries and other non-uniformities, injection level dependence, the influence of surface recombination, and completed solar cell performance.

Two-dimensional spectroscopy: probes for fast electronic processes
David Jonas, Chemistry and Biochemistry, University of Colorado, Boulder

Fast electronic motions are important in photochemistry, photosynthesis, interfacial electron transfer, and in some proposed next generation photovoltaics, where they generate multiple electron-hole pairs from a single photon. Our group developed two-dimensional femtosecond spectroscopy, a new method for measuring fast electronic motions in disordered materials mentioned in the recent DOE report on Basic Research Needs for Solar Energy Utilization. We have used this method to probe the fastest electronic motions in molecules, which proceed through "conical intersections" between electronic potential energy surfaces. The new method allows us to determine the mechanism for electronic motions, in that it characterizes the molecular vibrations which cause the electron jump and stabilize the new electronic configuration. The theory connecting these measurements shows that a 1 meV stabilization drives electrons from orbital to orbital in 100 fs. For chemically reactive conical intersections, which can have 1000x greater stabilization energies than the one observed here, the same theory predicts electronic equilibration within 2 fs. Such electronic movements are the fastest known chemical processes and are likely to be critical in photosynthesis, interfacial electron transfer, and multiple exciton generation.

Complex Oxides for Energy Storage and Energy Conversion
T.S. Kalkur
Microelectronics Research Laboratories, Department of Electrical and Computer Engineering, University of Colorado-Colorado Springs

Capacitors fabricated on thin films of complex oxides such as Barium Strontium Titanate (BST) offer high capacitance per unit area over capacitors fabricated with conventional oxides such as silicon dioxide. Multilayer capacitors implemented with BST can be used for a variety applications for energy storage such as on-chip decoupling capacitors as well as on-chip power source. In this poster presentation, we will highlight the work going in our laboratory on the modeling, fabrication and characterization of these films
on silicon substrates. Another interesting application of these materials are energy conversion. Oxides such as TiO2 and BST are semiconductors and can be used for energy conversion. We will also outline plans to explore these oxides for energy conversion.

Optical Durability of Candidate Solar Reflector Materials
C.E. Kennedy and K. M. Terwilliger, National Renewable Energy Laboratory

Commercialization of concentrating solar power (CSP) technologies requires the development of advanced reflector materials that are low in cost and maintain high specular reflectance for lifetimes of 10 to 30 years under severe outdoor environments. The Department of Energy (DOE) Solar Program targets cost reductions of up to 50% in the solar concentrator to meet long-term goals. This is accomplished through technology advances by moving from heavy glass mirror reflectors to lightweight reflectors that include surface coatings to reduce soiling. The objective of this research is to identify new, cost-effective advanced reflector materials that are durable with weathering. Durability testing of a variety of candidate solar reflector materials at outdoor test sites and in laboratory accelerated weathering chambers is the main activity within the Advanced Concepts task of the CSP Program at the National Renewable Energy Laboratory (NREL) in Golden. Outdoor exposure testing at up to three outdoor exposure sites that are fully instrumented in terms of monitoring meteorological conditions and solar irradiance has been underway for several years. In addition, accelerated exposure testing (AET) of these materials in parallel under laboratory-controlled conditions may permit correlating the outdoor results with AET, and subsequently predicting service lifetimes. Optical durability testing has been performed for a large number of candidate solar glazing and reflector materials including thin glass, thick glass, front-surface, polymer, and aluminized reflectors to date. The performance and durability of these materials will be discussed.

Progress toward Developing a Durable High-Temperature Solar Selective Coating
C.E. Kennedy and H. Price, National Renewable Energy Laboratory

Increasing the operating temperature of parabolic trough solar fields from 400ºC to >450ºC will increase their efficiency and reduce the cost of electricity. Current coatings do not have the stability and performance necessary to move to higher operating temperatures. The objective is to develop new, more-efficient selective coatings with both high solar absorptance (α > 0.96) and low thermal emittance (ε < 0.07) that are thermally stable above 450ºC, ideally in air, with improved durability and manufacturability, and reduced cost. Using computer-aided optical design software, we successfully modeled a solar selective coating with α = 0.959 and ε = 0.061 at 400C composed of materials with high-temperature stability. This exceeds the goal specification by about 1% overall, because 1% in emittance equates to about 1.2% in absorptance. Incorporating improved antireflective coatings, cermets, and textured surfaces should further improve absorption; however, trade-offs exist between low emittance and high absorptance. The key issue is depositing the modeled coating. Our experimental work focuses on modeling high-temperature solar selective coatings, depositing the modeled coatings, obtaining data to validate predictions, re-optimizing the coating, and testing the coating performance and durability. We will describe our progress toward developing a durable advanced selective coating.

Advancing Renewable Energy Research through High Performance Computing
Kwiseon Kim, Peter A. Graf, Qingzhong Zhao, Christopher H. Chang, Hai Long, M. Erkan Kose, Wesley B. Jones and Steven Hammond
Scientific Computing Center, National Renewable Energy Laboratory
Henry M. Tufo, Computational Science Center, Department of Computer Science, University of Colorado at Boulder
View Poster

We will describe the expertise, facilities and research activities within NREL’s Scientific Computing Center. This ranges from computational chemistry and biology to nanoscale materials simulation applications.

Here we propose a collaboration with the Computational Science Center at the University of Colorado for large scale computational science applications for modeling, simulation and visualization of complex systems and data for renewable energy research.

Theory of pH and Red-Ox Reactions: Application to Water Splitting
Yong-Hyun Kim, Kwiseon Kim, and S. B. Zhang, National Renewable Energy Laboratory

Electrochemical redox reactions are at the core of many renewable and sustainable energy applications including solar hydrogen production via water splitting, pollution-free power generation via fuel cells, and portable electricity storage via battery technology. In spite of the growing interest and importance, theoretical understanding of such electrochemical redox reactions are lacking on the microscopic quantum theory basis. Here, we present our recent efforts to address this problem via re-formulating the thermodynamics equations of pH and redox reactions and devising a systematic computational approach to process the thermodynamics equations with the first-principles density functional theory (DFT) and molecular dynamics (MD). The concept of pH can be incorporated into a thermodynamics equation by introducing a proton chemical potential. With this interpretation, the general acid-base chemistry can be cast as a simple pictorial representation. Our direct DFT-MD calculations reasonably reproduce the auto-ionization constants (pKw) of water and the dissociation constants (pKa) of acid and base molecules. In addition, introducing the electron chemical potential for charge-transferring redox reactions enables us to identify the positions of various important redox potentials such as H+/H2, O2/H2O, Zn/Zn2+, and Cu/Cu2+ with respect to the electronic energy spectrum of water. The calculated formation energy curves naturally explain how photoelectrochemical water splitting takes place in term of thermodynamics. We will apply and extend the theory to understand, predict, and optimize the semiconductor/liquid, oxide/liquid, metal/liquid, and organic/inorganic interfaces for sustainable energy applications.

[FeFe] hydrogenases: Biocatalysts for Hybrid Applications
Drazenka Svedruzic, Maria L. Ghirardi, Michael Seibert and Paul W. King
Chemical and Biosciences Center, National Renewable Energy Laboratory

The conversion of solar energy into chemical energy to generate clean fuels such as H2 has been a longstanding objective of photoelectrochemical research. Efforts to design photoelectrochemical devices with improved solar conversion efficiencies and longevities include the exploration of a variety of novel materials and designs. Also there is a need to identify, develop and optimize novel catalysts for H2 production or fuel cell devices. Our group is investigating the functional properties of biological catalysts, [FeFe] hydrogenases, to assess their praticality as substitutes for platinum in hybrid devices. Structurally the [FeFe] hydrogenases consist of a unique, iron-sulfur catalytic site that in some instances is electronically wired to accessory iron-sulfur clusters, which function in electron transfer. Although more structurally complex than platinum, these biocatalysts possess characteristics desired for bio-hybrid systems (i.e., high catalytic activities and solubilities) with the added benefit of utilizing abundant, low cost materials. Modifications of [FeFe] hydrogenases are being undertaken to optimize their structural properties to complement a range of materials and devices. Major challenges to the utilization of [FeFe] hydrogenases in hybrid devices include optimization of biosynthetic systems for biocatalyst overexpression and integration of biocatalysts that preserves catalytic efficiencies and stabilities. To address these challenges our group currently investigates; 1) how physiology and growth conditions affect recombinant expression and biosynthesis of [FeFe] hydrogenases, 2) the biocatalytic mechanism of H2 production, 3) integration and performance of [FeFe] hydrogenases in a dye-sensitized, photoelectrochemical cell, and 4) interactions of [FeFe] hydrogenases with polymers and nanomaterials. Here we report on recent progress made in these areas of investigation.

The Potential for Renewable Energy Sources and Energy Efficiency to Meet Colorado’s Future Electricity Needs
R. J. Peterson, P. Komor, L. Dilling, R. Klein
University

CU Energy Initiative/NREL SymposiumAbstracts

CU Energy Initiative/NREL Symposium
Abstracts