The team from Oregon State University described the concept of co-developing the same area of land for both solar photovoltaic power and conventional agriculture as agrivoltaics.
“Our results indicate that there’s a huge potential for solar and agriculture to work together to provide reliable energy,” said corresponding author Chad Higgins, an associate professor in OSU’s College of Agricultural Sciences.
“There’s an old adage that agriculture can overproduce anything. That’s what we found in electricity, too. It turns out that 8,000 years ago, farmers found the best places to harvest solar energy on Earth.”
The results have implications for the current practice of constructing large solar arrays in deserts, Higgins said.
“Solar panels are finicky,” he said. “Their efficiency drops the hotter the panels get. That barren land is hotter. Their productivity is less than what it could be per acre.”
The researchers analysed data from Tesla, which has installed five large grid-tied, ground-mounted solar electric arrays on agricultural land in Oregon.
The took this data, which was collected every 15 minutes, and synchronised it with data collected by micro-climate research stations they installed at the array which recorded mean air temperature, relative humidity, wind speed, wind direction, soil moisture and incoming solar energy.
Based on those results they developed a model for photovoltaic efficiency as a function of air temperature, wind speed and relative humidity.
“We found that when it’s cool outside, the efficiency gets better,” Higgins said. “If it’s hot, the efficiency gets worse. When it is dead calm, the efficiency is worse, but some wind makes it better. As the conditions became more humid, the panels did worse. Solar panels are just like people and the weather; they are happier when it’s cool and breezy and dry.”
Using global maps made from satellite images, their model was expanded worldwide, spanning 17 classes of globally accepted land cover, including classes such as croplands, mixed forests, urban and savanna.
The classes were then ranked from best (croplands) to worst (snow and ice) in terms of where a solar panel would be most productive. The model was then re-evaluated to assess the agrivoltaic potential to meet projected global electric energy demand that has been determined by the World Bank.
Such a study could play a key role in America if the proposed ‘Green New Deal’ – backed by several Democratic presidential candidates – is adopted into law.
Some firms have even been experimenting with floating solar panels which can be placed on large areas of unused space in the sea while minimising the land use impact.