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U.S. Department of Energy's ARPA Grants Hope to Transform Solar Energy Research

Dec 12, 2012

Solar energy research is a field that's constantly changing and evolving, as new research and technology allow for breakthroughs that might have been unthinkable even a year or two earlier.

Much of the funding for solar research comes from the U.S. Department of Energy (DOE), and recently the DOE's Advanced Research Projects Agency - Energy (ARPA-E) announced that it was giving grants worth $14 million to eight possibly transformational projects taking place across America.

These grants, given to private companies and universities alike, are part of a larger $130 million DOE investment in cutting-edge research encompassing 11 technology areas in 24 states.

For our purposes, though, the solar research projects are worth a closer look. 

The full list of solar project grants can be found here, but I spoke to researchers and developers involved in three of the winning projects more closely:

Georgia Tech University: At Georgia Tech, Professor Asegun Henry, an assistant professor in the Woodruff School of Mechanical Engineering, will receive $3.6 million to develop a high-efficiency solar reactor to produce solar fuel.

Using liquid metal, the reactor transports heat away from the sunlight-collection point to a chemical reaction zone, minimizing the loss of solar heat. This system could enable cost-effective solar fuels that would be used for transportation and continuous electric power generation.

For Henry,  who just arrived at the school less than a year ago,  this grant will allow him to hire and collaborate with more scientists than he previously could. For example, he said Pacific Northwest National Laboratory will help him build prototypes of electromagnetic pumps needed for his research.

"The biggest thing is it allows me to bring in all the necessary minds to attack all the critical aspects of the problem," Henry said. "When we're dealing with this particular technology, there's a lot of risky assets, and now I can engage some of the best and brightest minds who've thought about these issues. This is not inexpensive work, so I'm extremely grateful to ARPA-E."

Henry explained the way his process will work: In looking at solarchemical reactors as they are used currently, he said there's a two-step procedure in how the reactors work. The reactors take incoming light, and convert that light to heat. Then, that heat is converted to chemical bonds that are being formed and broken up. As the process currently works, one device does both of those tasks; what Henry and his team would like to do is to improve efficiency by separating the tasks and using two separate devices to take in the light and then convert the heat.

"When you look at why those devices aren't as efficient, it's because a lot of the heat is converted to radiation," Henry said. "The same device has to do both conversions, and the radiation comes from the high temperatures you're dealing with. The material that's being hit with the light is being heated up, and at high temperatures becomes radiation.

"We'd like to have two separate devices that are optimized for the process," Henry continued. "We want one device that takes in heat and converts it to chemical bonds, and a separate device that generates light to heat."

Henry said that this could also help solve the problem of storing solar energy, as his device would be "a new version of concentrated solar power that would allow us to store the energy chemically, instead of thermally."

That's where liquid metal comes into the process; the device that would convert heat to fuel is the reactor; and the device that converts light to heat is the receiver. Henry wants to take liquid metal,  run it through pipes, and the liquid metal then gets fed into a reactor. The reactor then converts the thermal energy in the metal into fuel, and you can store it; compress it and put it in a compressor vessel.

MicroLink Devices: One of the private businesses to receive an ARPA grant is MicroLink Devices, an Illinois-based outfit specialized in solar cell development. MicroLink received a $3.3 million grant to develop high-efficiency solar cells to capture concentrated sunlight with a unique blend of crystal layers in an innovative design.

As explained by Dr. David McCallum, MicroLink's vice president of business development, these cells will improve concentrated photovoltaic products to increase the amount of energy generated from solar power plants.

"The technology is based on a triple-junction solar cell, which was developed by NREL (National Energy Research Laboratory, a Division of the DOE) in Colorado," McCallum said. "What we're doing is doing the same approach, but using a different set of materials, with different composition in our cells."

MicroLink will use sophisticated manufacturing techniques to allow for reuse of expensive growth templates to minimize costs normally associated with high-performance solar cells.

"The cells will be the focus of the light collection concentration, and the money will give us more to put into research and design," McCallum said. "When we get the results we hope for, the solar cells' efficiency should go up by a large amount. "We're grateful to ARPA-E for giving us the grant, it's the biggest we've gotten from them."

University of California-Santa Cruz:  At UC-Santa Cruz, Professor Nobuhiko Kobayashi, an associate professor of electrical engineering, has been awarded a $1.6 million grant to develop an innovative optical device for harvesting concentrated sunlight into optical fibers, solar cells, and thermal storage devices, which maximizes use of the solar spectrum.

The optical device uses unique thin-film materials and structures to transfer and transform concentrated sunlight with minimum losses compared to traditional light-concentrating optics. Kobayashi spoke excitedly about his project in a phone interview, explaining that "we're extremely happy to get this money, but now we've got to get to work!"

Kobayashi said he's never worked on concentrated sunlight research before, but that his work essentially boils down to "creating a little device that can turn one giant optical device, like a mirror, into a smaller device."

This innovative optical device would harvest concentrated sunlight into an optical fiber, for "sun to fiber" for efficient transmission from mirrors at a distance, for applications such as thermal storage, photovoltaic conversion or use as daylight.

Essentially, Kobayashi wants to transmit light so you can further concentrate the light coming from a thousand different places.

He said after studying the "solar tilting" project going on in the Mojave Desert, he thought it would be useful to try to transmit light from a mirror through optical fibers to a place that it can be used.

"Optical fibers are used and designed for communication right now, but we have a question if any optical fibers can work in the solar spectrum," Kobayashi said. "The device we're working on would couple two optical components: a tiny mirror, and small optical fibers. The concept isn't new, but this particular device is something new."

Kobayashi said that until now there hasn't been a good material with which to make optic film, but that he believes he can now make the material that will allow for a high refractive index and a very low optical loss.

He and his research team will be getting assistance from two private companies based in California: Antropy, Inc., a patent specialist; and Tango Systems, Inc., which specializes in thin-film production.

The timetable for the project is 18-24 months.