Solar farms that would "co-locate" carefully selected crop plants between rows of photovoltaic panels might produce an energy "win-win" yield of electricity and biofuel, researchers at Stanford University say.
Computer models suggest the solution is ideal for sunny and arid regions in the U.S. Southwest, they say.
"Co-located solar-biofuel systems could be a novel strategy for generating two forms of energy from uncultivable lands: electricity from solar infrastructure and easily transportable liquid fuel from biofuel cultivation," Stanford postdoctoral researcher Sujith Ravi says.
Ravi and environmental Earth system science professors David Lobell and Chris Field are conducting the research at the university's Stanford Woods Institute for the Environment.
Solar farms create electricity out of sunlight, but a supply of water is needed to wash dust from the solar panels to make sure they run at maximum efficiency.
To minimize the spread and buildup of dust, the ground around the photovoltaic panels is also kept moist with water.
Desert-tolerant plants planted between and underneath the panels could use the excess water running off the panels, and as they grow could anchor the soil, cutting down on the problem of dust.
Such a system could allow solar farms to operate with reduced water needs, Ravi says.
"It could be a win-win situation," he says. "Water is already limited in many areas and could be a major constraint in the future. This approach could allow us to produce energy and agriculture with the same water."
Not just any crop would be appropriate, the researchers acknowledge, and food crops in particular are not well-suited to arid desert regions.
However, there is perfect candidate crop well-suited to the inhospitable environment, they say: Agave.
The prickly plant, known to most people as the source of tequila, thrives on poor soil and high temperatures in its native North and South America.
Tequila aside, they say, it can be a source for liquid ethanol, which as a biofuel can be blended with gasoline or operate as a sole source of power for ethanol vehicles.
For that purpose it's even better than many food crops already being used as biofuel stock, Ravi says.
"Unlike corn or other grains, most of the agave plant can be converted to ethanol," he says.
Ravi and his colleagues have run computer simulations of a hypothetical "co-locating" solar farm in California's southern San Bernardino County to test the thesis.
Further modeling to investigate the approach in other areas of the world could suggest ideal candidate plants to use and yield realistic estimates of crop yield and potential economic returns, they say.
