Solar panels can do more than generate energy

[image: Imagine: the planet with climate action]
Collaboration between Sheffield University, World Agroforestry and Kenya’s Latia Agripreneurship Institute (LAI) has produced promising results for a new kind of farming: agrivoltaics. By positioning solar panels above open fields sown with arable crops in semi-arid Kajiado (a 90-minute drive from Nairobi), the team found that cabbages, aubergines and lettuce grew one-third third bigger on average, and were more nutritious than vegetables grown in control plots with the same amount of water and fertiliser.
The solar panels created enough shade to help the soil retain vital moisture. The researchers, like Judy Wairimu at LAI, call it “harvesting the sun twice”. Scientists are discovering that solar panels may be good for more than just generating electricity. So what else can they do?
You’re reading the Imagine newsletter – a weekly synthesis of academic insight on solutions to climate change, brought to you by The Conversation. I’m Jack Marley, energy and environment editor. This week, we’re looking at how solar panels can boost food production, protect water supplies and even offset the impact of climate change on ecosystems.
With so many different needs competing for the same amount of land, it makes sense to combine renewable energy generation with other forms of land use, like farming. But why stay anchored to the land? Floating solar panels can generate clean energy on water and alleviate the squeeze on terrestrial space. They can have lots of other benefits too, according to new research by Roger Bales, a distinguished professor of engineering at the University of California, Merced.
California, along with the rest of the western US, is suffering its worst megadrought for 1,200 years. The state has the largest canal system in the world, which draws from rain and snow-fed headwaters in the north to quench the thirst of the dry and populous south. Around 35 million Californians and 5.7 million acres of farmland depend on the water which flows through these 4,000 miles of canals, but 2% of it is lost each year to evaporation.
“As an engineer, I have been working with colleagues on a way to both protect water supplies and boost renewable energy to protect the climate,” Bale says. “We call it *the solar-canal solution* <>, and it’s about to be tested in California.”
Bales and his fellow researchers found that covering the entire canal system would save more than 65 billion gallons of water annually. “That’s enough to irrigate 50,000 acres of farmland or meet the residential water needs of more than two million people,” he says.
These solar canals would also produce a lot of electricity: 13 gigawatts – half of the renewable power generation that state legislators must add from new sources to meet their clean electricity goal. Better yet, building these solar panels over canals instead of creating land-based solar farms would save more than 80,000 acres of farmland and natural habitat. Good news for threatened species like the Mojave Desert tortoise.
Speaking of species, what about the aquatic life living in the solar-clad waterways? Bales estimated that the shading provided by the panels would prevent aquatic weeds growing out of control and choking the water supply without expensive and harmful herbicides needing to be used.
But engineers aren’t just proposing floating solar farms on canals. Many envisage entire lakes or coastal bays covered in panels. Jon Major, a research fellow at the University of Liverpool, wrote in 2014 about a proposal to create “*floating solar islands* <>” on reservoirs in Japan.
Could this cause problems for the life inside these water bodies? We already know, thanks to the work of researchers like Antonia Law, who teaches physical geography at Keele University, that freshwater species are particularly vulnerable to climate change.
“Lakes and rivers occupy just 1% of the Earth’s surface but are *incredible hotspots for biodiversity* <>, sheltering 10% of all species globally,” she says. “Since 1970, numbers of freshwater vertebrates, including birds, fish, amphibians, reptiles and mammals, have declined by a staggering 83% through the extraction of lake water, pollution, invasive species and disease. Now, climate change threatens to drive even deeper losses.”
Lake heatwaves – when surface temperatures linger above their average for five days or more – could last “between three and 12 times longer and become 0.3°C to 1.7°C hotter” by 2100, Law says. “In some places, particularly near the equator, lakes may enter a permanent heatwave state. Smaller lakes may shrink or disappear entirely, along with the wildlife they contain, while deeper lakes will face less intense but longer heatwaves.”
You might think adding solar energy to the mix would only cause further stress for beleaguered aquatic wildlife. But not so, says Giles Exley, an associate lecturer of energy and environment at Lancaster University, who used a computer model to simulate how floating panels in 10,000 unique arrangements would affect the water temperature of Lake Windermere (England’s largest and best-studied lake). Exley found that the effect was likely to be as big as climate change, only in the opposite direction.
“A floating solar farm that reduces wind speed and solar radiation by 10% across the entire lake could *offset a decade of warming from climate change* <>,” he says. “Designs that shaded the lake more than sheltered it, by reducing sunlight more than wind, had the greatest cooling effect. Evaporation fell and the lake was mixed more frequently, which helps oxygenate the deeper water.”
In a small number of simulations, Exley found that floating solar panels could cut wind speed at the lake’s surface by more than they reduced sunlight, which might amplify the effects of climate change on wildlife. This highlights the importance of carefully designing waterborne solar farms so that they can benefit the climate, wildlife and people simultaneously.
Even without all these side benefits, floating panels are likely to improve on the energy generating capabilities of their land-based counterparts, as Exley explains:
“Floating solar panels on a lake or reservoir might sound like an accident waiting to happen, but recent studies have shown the technology generates more electricity compared with rooftop or ground-mounted solar installations. This is thanks to the cooling effect of the water beneath the panels, which can boost how efficiently these systems generate electricity by as much as 12.5%.”
*- Jack Marley, Environment commissioning editor*
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[image: A drawing shows solar panels covering a canal.] <>
*First solar canal project is a win for water, energy, air and climate in California* <>
Covering the state’s canals with solar panels would reduce evaporation of precious water and help meet renewable energy goals – all while saving money. Read more <>
[image: Floating solar panels mounted on plastic floats on a lake, with orange marker buoys.] <>
*Floating solar farms could cool down lakes threatened by climate change <>*
Earth’s floating solar power capacity has grown one-hundredfold in the last five years. Read more <>
[image: A square floating platform covered in solar panels on a water body with a town on the banks.] <>
*Japan turns to floating solar islands as it seeks to end reliance on nuclear power <>*
Solar power is clean, cheap and there are no restrictions on where it can be deployed. Read more <>
[image: A flock of pink flamingos huddle on a lake at sunset.] <>
*Climate change: world’s lakes are in hot water – threatening rare wildlife <>*
The lives of one in ten of Earth’s species are connected to lakes and their tributaries. Read more <>

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