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IF YOU had $150 million to spend on boundary-busting energy research, where would you put the cash? The US Department of Energy’s has committed that amount this year, with one lofty aim: to transform the planet’s energy future. But which technologies are its best bets?

ARPA-E knows it’s taking some huge gambles: it fully expects that many of the 37 projects it picked will fail. “Our model is to look for risky, high-potential technologies that don’t currently have a means of funding to see if they will work,” says ARPA-E’s deputy director, Shane Kosinski.

“ARPA-E knows it’s taking some huge gambles: it fully expects many of the 37 projects it picked to fail”

The initial announcement that funding was available resulted in a flood of over 3600 grant applications. A team of 400 leading energy researchers helped whittle down the list. The fine details of the projects chosen remain sketchy, however.

Topping the grant allocation list was drilling company Foro Energy of Littleton, Colorado. The company has been tight-lipped about how it plans to spend the $9.1 million it was allocated. However, ARPA-E has confirmed that the grant will help to develop a hybrid thermal-mechanical drill system capable of quickly cutting through ultra-hard rock formations deep underground, potentially unlocking vast new stores of geothermal energy.

For “hot rocks” to become a viable, mainstream energy source, drills that can cut through hard crystalline rock more quickly and cheaply than those used in the oil and gas industries are needed.

“If you can drill down 2 to 3 kilometres you can potentially open up a vast sea of heat that you can run power plants on,” says at the Center for American Progress, who headed the DoE’s Energy Efficiency and Renewable Energy Office in 1997.

Such drilling technology is likely to use intense temperatures to soften hard crystalline rock, allowing a mechanical drill bit to move through it with less wear. Prior attempts at thermal drilling have employed electrical heaters, pressurised steam, lasers and blowtorches as hot as 1800 °C.

The type of thermal technology Foro is pursuing remains unknown, but documents obtained by 91av through a Freedom of Information Act request reveal that the company currently has a laboratory-scale drill and plans to dig a 4.6-kilometre-deep demonstration well within three years. “We didn’t even consider this 10 years ago because we did not imagine you could drill down that far economically,” says Romm.

The second-largest grant went to chemical manufacturing giant and biofuel start-up Bio Architecture Lab of Seattle, which will split $9 million to develop technology to obtain biobutanol from algae. The project aims to make biofuels a more viable energy source, says Nathan Danielson of DuPont. The first goal would be to produce higher yields than cellulose-based feedstocks such as maize are able to, without needing fresh water or arable land to grow. Secondly, biobutanol packs a higher energy density than existing ethanol biofuels and can be mixed with regular gasoline in higher concentrations.

“The conversion of algae into its basic sugars and subsequent treatment with a biocatalyst into biobutanol has never been done before; a significant portion of these technologies will have to be developed from scratch,” says Danielson.

If 2.5 per cent of US coastal waters were seeded with floating kelp beds, the biobutanol harvested from them could replace about 26 billion litres of petroleum-based gasoline per year, Danielson claims.

ARPA-E’s third-largest grant – one of only two for wind power – went to of Wilbraham, Massachusetts, which is developing a new type of wind turbine that could dramatically increase energy generation. It has been working on turbines which harvest twice as much energy as a conventional turbine of the same size.

FloDesign would not reveal specific goals for its 30-month project. However, the company has previously said it planned to complete a 3.6-metre-diameter, 10-kilowatt system by early 2010 before ramping up to megawatt-rated turbines.

Rounding out the four largest grants was $7.2 million to develop low cost, megawatt-rated batteries capable of backing up and smoothing out the intermittent energy supply from wind farms and other renewable sources. Today, such power-grid-scale batteries are prohibitively expensive for most renewable energy applications.

of Joplin, Missouri, and the in Richland, Washington, will use the funds to develop a sodium beta alumina battery that will cost no more than $200 per kilowatt hour of capacity, compared with about $500 today.

Sodium beta alumina batteries have been around for decades and require operating temperatures in excess of 300 °C. By reconfiguring the battery’s architecture, the group hopes to be able to operate it at higher power densities and at lower temperatures, allowing for construction using cheaper materials. The project aims to develop a modular, scalable 5-kilowatt battery within three years.

For Romm, the recent influx of funding to enable these and other ARPA-E grants is a dream come true. “I would have given anything to have had this kind of new money,” he says.

Others are less enthused. Energy analyst Daniel Kammen at the University of California, Berkeley, says the agency needs a more radical approach. “I think there are some nice projects in there, but I think we’re going to need to see a more ‘pie in the sky’ portfolio over time,” he says.

Such projects may include super-high wind turbines that tap into the jet stream, space-based solar power, and solar panels integrated into the skin of buildings, he suggests.

ARPA-E will be accepting applications for its next round of funding before the end of the year, though this cash is likely to be provided for a narrower range of technologies directed at specific problems, Kosinski says. But he insists it is still aiming high. “If it’s going to make a significant impact, ARPA-E is interested.”