A Tour of the U.S.'s Clean Energy Future [Slide Show]
The third annual ARPA-E summit showcases potentially transformative energy technologies
![A Tour of the U.S.'s Clean Energy Future [Slide Show]](https://www.scientificamerican.com/sciam/cache/file/C248BA78-A493-4C31-A6AC3EB58B04197F.jpg?w=590&h=393)
A Tour of the U.S.'s Clean Energy Future [Slide Show]
- CONSTANT WIND: High in the stratosphere the wind is always blowing, supplying a steady source of energy. But how to harness it? Makani Power's carbon-fiber "kite" would circle high in the sky, harvesting incessant wind power and transmitting it via its tether to the ground. The kite-wing has already flown in tests. © David Biello
- ARTIFICIAL PHOTOSYNTHESIS: Sunlight kicks off a chemical reaction that splits water, releasing oxygen and hydrogen, which can be used as a fuel--just as plants use sunlight to split water to make carbohydrates. Sun Catalytix hopes to turn its sunlight-and-water system into a cheap source of power for homes. © David Biello
- SEMICONDUCTOR REFRIGERATOR: Without hydrofluorocarbons or compressors, Sheetak technology employs semiconductors to refrigerate--and may enable cheap cooling for the poorest people in developing countries. "It will enable people who never had access to refrigeration in their lives to use refrigeration to preserve food and medicine," said ARPA-e director Arun Majumdar, noting the company has a deal with a distributor in India to make such coolers. "We can make locally and sell globally." © David Biello
- BETTER BIOREACTORS: Glass manufacturing giant Corning is working on technology to improve algae growth in so-called bioreactors. Quantum dots shift incoming sunshine to wavelengths the human eye perceives as red, which is also the best wavelength for photosynthesis. It also blocks ultraviolet light to help keep things cooler for the algae. © David Biello
- SOLAR-THERMAL ENGINE: This Rankine cycle engine from Cyclone Power Technologies can run on everything from sunshine to syngas derived from garbage at temperatures as low as 260 degrees Celsius. The engine employs heat—or waste heat—from these sources to create the steam that powers the engine. © David Biello
- MICROBIAL FUEL CELL: Graduate students at the Wyss Institute for Biologically Inspired Engineering at Harvard University explain their microbial fuel cell, a method for producing electrofuels, to ARPA-E founding director Arun Majumdar. Using synthetic biology to tinker with the genes of microbes ranging from Escherichia. coli to algae and cyanobacteria is one route to creating biologically derived fuels and chemicals. © David Biello
- CAPTURING CARBON: "The U.S. has the largest reserves of coal in the world and we ought to be able to use it in a sustainable way," ARPA-E director Arun Majumdar argued. To that end, the agency is funding work on making carbon capture and storage cheaper so that it can be implemented at coal-fired power plants. The system would store carbon deep underground, as laid out in this diagram. © David Biello
- ALTERNATIVE FUELS: Biofuels remain one of the most promising options to reduce oil use in another transportation sector—aviation. The oil derived from the weedy flowering plant known as camelina can be refined into a bio–jet fuel that has already been used to power commercial and military flights. And there are other options as well. "The most likely source of scalable biofuel for aviation is micro- or macro-algae," FedEx's Fred Smith said. "That's seaweed and pond scum." © David Biello
- IMPROVED INTERNAL COMBUSTION: One of the winners of the U.S. Department of Energy's America's Next Top Energy Innovator challenge, Umpqua Energy injects hydrogen into regular gasoline in order to boost the power that today's internal combustion engines can deliver. "We've doubled the power for the same fuel consumption," U.S. Secretary of Energy Steven Chu noted. With existing technologies, such as variable transmissions and lighter weight steels, automakers could cut U.S. oil use by nearly 50 percent as well—an effort boosted by new fuel economy standards. © David Biello
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