Power Electronics

Experiments May Reduce Possibility of Water Wars

A method that uses roughly only one-hundredth the fresh water customarily needed to grow forage for livestock may leave much more water available for human consumption, as well as for residential and industrial uses. As a byproduct, it also may add formerly untapped solar energy to the electrical grid.

The method for lessening water use is being tested by 42 wireless sensors being installed in a forage-growing hydroponic greenhouse built barely a stone’s throw from the Mexico border under the supervision of the National Nuclear Security Administration’s Sandia National Laboratories, a U.S. national security lab.

Sandia is interested because, says lab researcher Ron Pate, “Disputes over water are possible, if not likely, causes for war in the 21st century.”

Conventional farming methods in arid regions lose huge amounts of water through evaporation and over-absorption by soil. Over time, this can also result in soil salination and loss of agricultural productivity. Neither are factors in hydroponic greenhouses, which do not require high-quality arable land to function in the first place. The Sandia-placed sensors in combination with computer simulations will tell researchers how to grow crops more efficiently than hydroponics alone.

The hydroponic greenhouse, also known as “protected agriculture” or “controlled-environment agriculture,” controls and modifies light reaching the plants. Experiments will reduce light intensity and restrict certain frequencies, using a variety of shading mechanisms to avoid overheating and improve plant growth.

Experiments are being planned to use the blocked light to create another asset: solar-generated electrical power. (Greenhouse pumps, timers and sensors are already powered by freestanding solar modules that change light into electricity, which is then stored in batteries for nighttime use and during cloudy weather conditions.)

“Greenhouses could be a solar source,” says Sandia researcher Vipin Gupta, “because sunlight has to be filtered in arid areas to prevent crop damage because it is too intense. The challenge is to create reliable, effective materials to use that part of the spectrum the plant is not interested in using to produce power that can be put on a grid as well as operate the greenhouse.” Commercial interest has been expressed in this project.

Vipin is currently based at the University of Texas at El Paso’s Materials Research Technology Institute and serves as a local focal point for the project. Sandia technologist Ed Baynes is based in Las Cruces and provides technical support for the greenhouse. Sandia/California researchers Nina Berry and Jesse Davis, with two summer student interns, are helping implement the wirelessly networked sensor array and cell phone data link, expected to be installed in mid-September.

For more information, visit www.sandia.gov.

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