To celebrate the 40th Anniversary of Earth Day, the U.S. Department of Energy (DOE) Office of Scientific and Technical Information (OSTI) has opened the Green Energy Portal. It offers to all -- scientists, students and the public -- quick access to research and development in the area of renewable energy. There are thousands of full-text documents.
"The DOE Green Energy portal is part of the DOE Open Government Plan, which furthers the Administration's Open Government Initiative. DOE Green Energy contains both current and historical research, including bibliographic citations, technical reports and patent information on different types of renewable energy resources and energy conservation. Subject areas include but are not limited to solar, wind, bioenergy, hydroelectric, geothermal, tidal and wave power, and energy storage."
Source: Email from Tim Byrne at OSTI firstname.lastname@example.org
This is most likely a just a short cut, but I trust that most all of these documents and their indexing is available via NTIS, NTRL, Science.gov and/or the DOE's Information Bridge.