By Jeff McMahon, Opinion, Forbes

Purdue researcher Rakesh Agrawal is leading work to develop solar cells that do not obstruct the light needed for crops to grow.

A Purdue University professor is developing a way for farmers to capture solar energy without blocking the sunlight their crops need.

The solar collectors being developed by Chemical Engineering Professor Rakesh Agrawal and his colleagues would capture infrared radiation for energy production while letting visible light pass through to crops.

“We are going to build this structure on agricultural land. We have an agronomist who will grow corn and we will monitor the land and make sure we can produce electricity and grow food at the same time,” he said in Chicago Wednesday. “The day we figure out how to have food and energy coexist together, I think it is perfect.”

Winner of the 2011 National Medal of Technology and Innovation, Agrawal just received a $2.5 million grant from the National Science Foundation for a demonstration project.

“There are dozens of possible structures we can build. Some are cheaper than what is being done right now,” he said in a lecture at the Illinois Institute of Technology co-sponsored by the Chicago Council on Science and Technology. “It’s why we want to build these on the farm and do experiments and prove indeed this can be done. I think NSF has been very kind to give us the money to go and prove it. I’m pretty excited about it.”

Agrawal calculates that the United States would need to cover 4 to 6 percent of its land area with solar panels to meet all of its energy needs, including transportation. Land currently developed with buildings and roads accounts for 3.6 percent—not enough. But most population centers are near agricultural land, which covers 54 percent of the United States, making farms a promising location for renewable-energy generation.

“Almost all the states can meet their local needs with local photons,” he said.“This is big news, right? This is a big change from building $30 billion of power supply lines from the regions of the United States where there’s a lot of sunshine to the regions where there’s not.”

Agrawal came to this research after spending three years trying to make biomass fuels more efficient. Unlike photovoltaic cells, which currently have an efficiency of about 20 percent, biomass fuels contain less than 1 percent of the solar energy that fell on their feedstocks, he said. After struggling to improve that number, Agrawal concluded it made little sense to try to improve or expand biomass production.

“We were asking the wrong question all this time. We were asking the question of how to make oil from biomass or from solar. But why do we need the oil? Actually it is for transportation,” he said. “We should have been asking the question: how do we use solar energy for transportation?

Agrawal’s proposed systems would employ hydrogen as a transportation fuel, produced with solar energy. They would also generate electricity much as solar panels do now, but without capturing the visible light plants need, and they could also reflect heat to a collector for water purification, he said.

Agrawal believes such a system could meet the food, energy and water needs of a growing population because it uses both land and solar radiation more efficiently.

Rakesh Agrawal proposes to simultaneously use different parts of sunlight’s spectrum to produce crops, generate electricity, collect heat and purify water on the same piece of land.

By Jeff McMahon, based in Chicago. Follow Jeff McMahon on Facebook, Google Plus, Twitter, or email him here.

For a link to the original article, go to Forbes