Making Solar Arrays Better for the Environment
One of the most ironic things about renewable energy technologies isthat sometimes they’re bad for the environment.
Hydropower can be bad for fish and marine eco-systems, wind turbinesmay contribute to bird and bat deaths, and photovoltaic solar arrays are usually set up in areas that have been cleared of vegetation.
But the National RenewableEnergy Laboratory (NREL) is using its newest solar array at the National WindTechnology Center (NWTC) near Boulder, Colorado, to examine theenvironmental impact of such large-scale projects and develop ways tomitigate any effects.
Many of the best locations in the U.S. for renewable energy are inopen, sunny ecosystems such as deserts and prairies. These are aridareas where, once disturbed, the vegetation and wildlife may be slow torecover.
"Most plant species in the West have evolved to grow in directsunlight, and that’s where the best resource is for generating solarpower," NREL Senior Biologist Brenda Beatty said. "We need to know howshade from PV panels may affect native plant growth and whether thoseeffects will impact wildlife."
Furthermore, PV array fields typically are graded flat and thevegetation is removed before installation begins. Soils under PV arraysfrequently are sterilized to prevent weed growth, a step that not onlyintroduces chemical agents into the environment, but also prevents thenatural revegetation of native plants that could minimize erosion andprovide wildlife habitats.
Alternatively, installers spread gravel beneath the solar panels toinhibit weed growth. But gravel can trap heat, which not only can reduce an array’s operating life, but also can stress any plants that mightgrow there.
The NREL study examines how ecosystems respond to renewable energydevelopment and develop best management practices that re-establishhabitat, minimize weed invasion, prevent erosion and protect wildlife.The research may help utilities and solar companies reduce theirlong-term operation and maintenance costs.
Crews will manually reseed graded areas beneath the solar panels inearly spring with a blend of native grasses. The composition of the seed blend was formulated to include plants that can tolerate some shading,to help curtail erosion and weed invasion, and to be somewhatfire-resistant.
In the center of the eight-acre array field, construction crews alsoleft two acres ungraded. This parcel of intact vegetation will serve as a natural source of native seeds to help in revegetation efforts.
To develop a clearer understanding of the types of plants that cansuccessfully be grown under solar panels, NREL is also creating one-acre vegetation test plots under the solar array – as well as two controlplots away from the solar panels. Data from the test plots will be usedto evaluate vegetation success under varying conditions of moisture,seed mixes, mulching, and other treatments.
"The experiments will begin to give us a handle on how PVinstallations and operations affect vegetation in our portion of thearid West, and the information obtained may be useful for other NRELprojects, and for revegetation efforts at other solar installations,"Beatty said.
The shortgrass prairie is also home to a wide variety of wildlife.Before the array’s installation, Beatty supervised the humane relocation of a black-tailed prairie dog colony from the southwestern corner ofthe NWTC to another onsite location which they had prepared for theanimals.
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