Coal, Renewables

Renewables Still Need R&D

Issue 4 and Volume 108.

By: Stanley R. Bull,
National Renewable Energy Laboratory

Research and development activities remain essential to the widespread commercialization of renewable energy. The National Renewable Energy Laboratory (NREL), operated for the Department of Energy by Midwest Research Institute and Battelle, pursues a unique and highly motivating mission — to develop commercially viable renewable energy and energy efficiency technologies for the benefit of the nation and the world. Recent successes and cutting-edge explorations validate the enduring importance and impact of renewable energy R&D.

In solar cells, NREL researchers and their industry partners continue to set records for sunlight-to-electricity conversion efficiency, marking progress toward lowering the cost of commercial modules and solar electricity. As an example, thin-film cells using a copper-indium-gallium-selenium material system have reached efficiencies above 19%, the same performance levels as research multicrystalline silicon cells. This achievement underscores the high efficiency potential and manufacturability of large-area thin-film modules. Scientists are also vigorously pursuing solar devices using new materials such as organic semiconductors, concentrating optics, improved sputtering techniques, and other options for very low cost solar devices.

Improving manufacturability is one of the most critical issues facing the solar industry today. Congress recently appropriated the first $4 million of a $21.2-million construction project to build a unique research laboratory at NREL to investigate process and manufacturability issues common to solar technologies.

In wind energy research, NREL recently developed the capability to test wind turbine blades at their natural resonant frequency along two axes of the blade. This enables researchers to assess a wide range of larger blades for their susceptibility to fatigue and delamination. As the industry moves towards larger blades to serve low-wind-speed areas and offshore locations, NREL is responding with new research efforts to optimize designs, develop new wind turbine control strategies, and assist stakeholders with analyses of these new opportunities. NREL also recognizes the critical need for U.S. industry to test their new larger turbine designs to be able to compete with foreign suppliers, and is working with DOE on plans for these critically needed testing facilities.

Hydrogen from renewables is another exciting area of research today. NREL is developing ways to produce hydrogen from a variety of feedstocks and energy sources. Molecular and metabolic engineering is improving yields of hydrogen from water through a natural process involving green algae and sunlight. Photoelectrochemical systems, integrating photovoltaic semiconductors, produce hydrogen directly from water using sunlight, and NREL scientists are investigating materials that will improve efficiency and performance lifetimes. Hydrogen can also be produced from water using renewable energy sources to power an electrolyzer; low-cost wind electrolyzer systems, for example, are being developed. Lastly, hydrogen can be produced from biomass via gasification or pyrolysis, requiring research into catalysts, separation techniques, and process controls.

The geothermal energy industry is benefiting from NREL’s development of a polyphenylenesulfide coating system for steel surfaces in hostile corrosive environments. This material, now commercialized under the trade name CurraLon, protects and extends the life of key components in geothermal power plants such as heat exchangers, lowering energy costs. NREL is also evaluating advanced heat-to-electricity cycles that increase conversion efficiency and is performing fundamental research to significantly enhance airside heat transfer rate in finned air-cooled power plant condensers.

Stanley Bull
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Small modular biomass systems help supply electricity to rural areas using wood, crop and animal waste, and landfill gas. NREL researchers have worked with industry to develop several successful sub-5 MW prototype systems that use efficient and clean biomass-based generating systems. The U.S. Forest Service is also working with NREL to generate electricity from forest thinnings.

The underlying foundation of all this work is our basic understanding of the materials and fundamental mechanisms related to these technologies. Nanoscience — the study of materials in such small sizes that they assume new properties — is opening doors to advances like semiconductor “quantum dot” arrays with eventual applications in high-efficiency solar cells and solid-state lighting. NREL is also developing carbon nanotube structures that can store hydrogen in a lightweight device for future use in fuel cell vehicles. Lastly, as math underpins all the sciences, computational science is becoming an equal partner with experimental and theoretical science. As an example, NREL scientists are simulating the diffusion of oxygen and hydrogen in algal enzymes through computational modeling, impossible to observe directly in the lab.

Transitioning from today’s reliance on fossil fuels to a national energy portfolio including significant renewable energy sources will require continued improvements in cost and performance of today’s renewable technologies, as well as breakthroughs to new generations of technologies and as-yet-unforeseen renewable energy solutions. This transition will also require shifts in the energy infrastructure to allow a more diverse mix of technologies to be delivered efficiently to consumers in forms they can readily use. The upcoming decades will bring an interweaving of individual renewable energy technology and market developments that will both challenge our ability to adapt to new ways of thinking about and using energy, and bring us hope for a clean and secure energy future.

Stanley Bull is the Associate Director for Science and Technology at the National Renewable Energy Laboratory and Vice President with Midwest Research Institute. He can be reached at [email protected]