The Advanced Research Projects Agency for energy put out its second call for new ideas, and this time, the agency has narrowed its focused to three research fields.

The new arm of the Department of Energy, which is dedicated to high-risk, high-reward innovations, is betting $100 million on batteries for cars, new materials for capturing carbon, and microorganisms that can convert sunlight and carbon dioxide directly into fuels.

"This solicitation focuses on three cutting-edge technology areas which could have a transformational impact," said Energy Secretary Steven Chu, in a release.

Energy gets used in a lot of different ways, so no single technology can make all the difference. That said, a few key pieces of technology would provide the political world with better clean-energy options. We use coal to make half the nation's electricity. Fossil fuels, mostly oil, burned for transportation account for roughly one-third of American emissions. Finding cheaper, cleaner solutions to the key problems of baseload generation and fuel for cars would be major steps toward reducing carbon emission and dependence on foreign oil.

This is the second call for proposals the DOE outfit has issued. ARPA is modeled after the military's Defense Advanced Research Projects Agency. This new request is as narrow as the last was wide. In the first grants announced in October, ARPA-E spread the first $150 million from its coffers broadly on 37 different technologies across the energy landscape from building efficiency to biomass conversion to waste heat capture. Each endeavor received between $500,000 and $9 million.

Energy-dense, low-cost, long-lived batteries have been a dream of inventors since Thomas Edison claimed to have solved the problem in 1901. His battery was described by The New York Times as "combining all of the long-sought advantages of lightness, durability, and effectiveness." It was so good, in fact, that "it was predicted that a new art of electrical propulsion and navigation would result."

Though that has yet to happen, scientific knowledge of materials at the nanoscale has grown by leaps and bounds. ARPA-E is looking for battery makers who can meet the ambitious goals (.pdf) laid out by the United States Advanced Battery Consortium, a group of car makers working with the government.

Another area where scientific knowledge has been growing at an astounding pace is microbiological genomics. Scientists have gone beyond understanding individual gene functions to tweaking them for specialized functions. Synthetic biologists are working to develop microorganisms that are, in essence, programmable. One company, LS9, calls them "DesignerMicrobes." The equation that the DOE would like these biological machines to solve is simple: CO2 and sunlight in, a substitute for oil out. Already, a flock of synthetic biology companies like Amyris, Solazyme and Synthetic Genomics are trying to create alternatives to oil using microorganismal genomics, and the DOE would like to see more.

Carbon dioxide capture is considered a mainline strategy for reducing carbon dioxide emissions by the Intergovernmental Panel on Climate Change, but it requires a substantial percentage of the energy that the plant produces to do it. It's thought that new materials could, as the DOE puts it, "dramatically reduce the parasitic energy penalties and corresponding increase in the cost of electricity required for carbon capture."

Some labs, like Omar Yaghi's at UCLA and Gerbrand Ceder's at MIT, have developed new methods for finding large amounts of new materials and determining their properties. Their work is a promising start, but more carbon capture isn't the only step needed to keep smokestack emissions from warming the earth. They also have to be permanently buried. Last year, energy researcher Vaclav Smil at the University of Manitoba estimated that to bury just 25 percent of CO2 produced by power plants would required moving twice the material the world's crude-oil industry (.pdf) does now. That's a tall order and would require a heck of a lot of pipes and caverns.

Image: A prototype sunlight-to-fuel solar furnace at Sandia National Laboratory.

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