Why Covering Canals With Solar Panels Is a Power Move
Peanut butter and Jelly. Hall & Oates. Now there is a duo that could literally and figuratively be even more powerful: solar panels and ducts. What if we didn’t leave the channels open and let the sun evaporate the water, but instead covered them with panels that would both shade the precious liquid and soak up solar energy? Maybe humanity can do that.
Scientists in California just got the numbers on what would happen if their state slammed solar panels on 4,000 miles of its canals, including the great California aqueduct, and the results suggest a potentially beautiful partnership. Their feasibility study, published in the journal Nature Sustainability, found that if the panels were used nationwide, they would save 63 billion gallons of water from evaporation per year. At the same time, solar panels in California’s exposed canals would provide 13 gigawatts of renewable electricity annually, roughly half the new capacity the state needs to meet its decarbonization goals by 2030.
California’s water extraction system is the largest in the world, serving 35 million people and 5.7 million acres of farmland. 75 percent of the available water is in the northern third of the state, while the lower two thirds of the state account for 80 percent of urban and agricultural needs. To move all of the water, pumps are required to make it flow uphill. Accordingly, the water system is the largest single electricity consumer in the state.
Solar collection channels would not only produce renewable energy for use across the state, but would also power the water system itself. “By covering channels with solar panels, we can reduce evaporation and avoid disrupting nature and work areas. At the same time, we can offer renewable energy and other benefits, ”says environmental engineer Brandi McKuin of the University of California, Merced and the University of California. Santa Cruz, lead author of the paper.
Ironically, the performance of solar panels decreases with increasing temperatures. In a solar cell, photons from the sun knock electrons out of atoms and generate electricity. If a panel gets too hot, this puts the electrons in an already excited state so they don’t generate as much energy when they are shifted by photons. Spanning panels over ducts would make them water-cooled, so to speak, and increase their efficiency. “Also,” adds McKuin, “the shade of the panels reduces the growth of aquatic weeds, which is a major problem in sewer maintenance.”
The engineering wouldn’t be too complicated either. You could throw a steel tie over a canal and cover it with panels. India has actually experimented with such solar ducts and commissioned a 25-mile stretch for an estimated cost of $ 14 million.
To put it bluntly, this new paper is not a direct hit for state officials to immediately cover all channels with solar panels. “Our paper is not a detailed construction or concept design – it is a feasibility study, a proof-of-concept to take it to the next phase of investing in a demonstration project,” says engineer Roger Bales of the University of California, Merced. “But I think the amount of electricity could be significant both nationally and locally.”
Bales and McKuin calculated all of this using a variety of models. For example, the evaporation rates came from hydrological models. They also folded up climate models to predict how the state will warm in the coming years. They got so grainy that they also calculated how the cooling effect of the canal water would improve the panels’ generating efficiency.
Ultimately, they landed on a potential annual saving of 63 billion gallons of water across California. But they also took into account the human benefits of such a project, which are more nebulous. For example, many farmers use diesel generators to pump their water. If solar panels were to provide this energy instead, this could reduce local emissions and thus improve air quality. “You can look at the economic costs, but you can also look at the social benefits,” says Bales.