Apparently some picture of Indians using a photovoltaic (PV) panel above a water canal has gotten some Californians clamoring for PV all over California’s major aqueducts. Someone ran a rough look at the numbers here. It is true that harnessing solar energy would offset the energy footprint of moving all that water around, which is not trivial. But there are a couple of reasons why any water manager should be skeptical of this option, which aren’t widely publicized.
- California’s aqueducts, open to the atmosphere, receive a high dose of natural UV irradiation as the water travels, which acts as a natural disinfectant to keep down microbial growth. This means that the water quality would decrease if the UV rays were captured for energy purposes. Drinking water utilities would likely need to spend more money (and energy) on water treatment to offset this natural treatment process. (As an aside, this is what concerns me about Christo’s art project in which he wants to drape fabric over six miles of the Arkansas River in Colorado.)
- PV panels get dirty, especially in the desert. You know what they use to clean PV? Water. So you’d also lose some of the water to cleaning those hundreds of miles of panels, which at scale is also not trivial.
- Finally, there is the cost of PV itself. Solar projects are notoriously capital intensive, which is one reason that they have a tough time competing with non-renewable energy projects like coal and natural gas, which have higher operations and maintenance costs. The installation above the aqueduct channels would require new design and likely extra steel to straddle the wide channels, compared to normal solar arrays mounted on single posts.
My guess is, utilities like Metropolitan Water District of Southern California, which owns the Colorado River aqueduct, or the Los Angeles Department of Water and Power, which owns the Los Angeles aqueduct, have done enough cost analysis to determine that the benefits do not outweigh the costs (and the financial risks) in this case. It’s understandable to me that they would be very conservative when it comes to anything that might disrupt their most valuable resource: water.