Huge Floating Solar Project Being Developed In California — To Be Largest In US Once Completed

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What will be, once completed, the largest floating solar photovoltaic (PV) project in the US is now under development in California by the company Pristine Sun, according to recent reports.

The project array — which will be situated on 6 wastewater ponds (filled with treated sewage) in Sonoma County — is currently slated to be completed in 2016, and will, once completed, provide enough electricity to power roughly 3,000 Californian homes. It will have a power output capacity of 12.5 megawatts.


Considering that it’s relatively hard to get access to well situated land (for solar) in Sonoma County, the choice of developing a floating solar PV project was a strategic one, according to the deputy chief engineer at the county’s Water Agency, Cordel Stillman.

“We know it’s hard to get big solar projects in Sonoma County. You get pushbacks on aesthetics and the taking of agricultural land. We took a look and said ‘Where else can we put solar?’ ”

The ponds that’ll be home to the solar PV arrays are being leased from Sonoma County Water Agency for roughly $30,000 a year.

The CEO of Pristine Sun, Troy Helming, noted: “We consider these bodies of water an ‘underutilized asset’ or ‘un-utilized asset’ (from which) their owners can now enjoy a modest revenue stream by leasing the water surface rights to Pristine Sun, in order for us to sell clean energy to the local utilities.”


Climate Progress provides some background:

Floating solar — which typically involves installing solar panels on pontoons that rest on the surface of a body of water and is also called “floatovoltaics” — has been installed in California before. Far Niente, a Napa Valley wine producer, has a 1,000-panel floating solar installation on its winery’s irrigation pond. The array, coupled with 1,300 solar panels on the land next to the pond, provides enough yearly energy to offset the winery’s power usage. As the New York Times reported in 2011, the solar arrays are useful in other ways too: they can help prevent harmful algae growth and prevent evaporation from ponds.

Floating solar has already caught on in other parts of the world. Australia is starting construction on its first floating solar power plant this year, which will feature a solar array on a wastewater pond. France, too, is home to a large-scale floating solar array, and Japan has also begun taking floating solar seriously. Japan’s lack of space and desire to move away from nuclear power after the Fukushima disaster make it a prime spot for floating solar. It’s unsurprising, then, that the country is home to the world’s largest floating solar array.

If only in specific circumstances and environments, floating solar PV arrays do seem to be an interesting solution. I’ll be curious to see what gets developed, with regard to the approach, in the coming years.

We’ve been writing about floating solar power plants a lot as of late. Here are some of our recent articles on this topic:

First Floating Solar Power Plant To Be Tested In India (April 2013)

India Plans World’s Largest Floating Solar Power Project (50 MW) (July 2014)

Kyocera To Develop Japan’s Largest Floating Solar Power Plant (September 2014)

Yet Another Claim For World’s Largest Floating Solar Plant (November 2014)

Sunflower Floating Solar Power Plant In Korea (December 2014)

World’s Largest Floating Solar Power Plant Announced By Kyocera (December 2014)

Image Credit: SPG

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James Ayre

James Ayre's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy.

James Ayre has 4830 posts and counting. See all posts by James Ayre

24 thoughts on “Huge Floating Solar Project Being Developed In California — To Be Largest In US Once Completed

  • Floating panels on reservoirs and lakes offer two advantages over terrestrial. They cut evaporation, a big issue in water-short regions, which is an increasing part of the globe. And the water keeps the panels cool and hence raises output; how much depends on whether the developer pays extra for a pumped water cooling system, but simple proximity must have an effect by air convection and conduction through metal frames.

    I haven’t heard about the effect on the ecosystem. Cutting aquatic vegetation and creating shade may or may not be good for fish.

    • Sewage ponds generally don’t harbour a large community of photothropic organisms and their dependents (unless it is an algae treatment unit, but you wouldn’t cover those in solar panels to begin with).

      Various micro-organisms, either heterotrophic (eating biomass like we do) or chemolithotrophic (obtaining energy from inorganic molecules like ammonia or methane) dominate such an ecosystem. They don’t really care all that much about light and neither do the organisms consuming them.

      What could be worrying is the reduction in oxygen levels due to reduced gas exchange, but that would only become much of an issue if the pond was almost completely covered.

      • One of the best technology to treat sewage water is the use of solar powered laminar flow recirculators. It encourages oxygen oversaturation (>100%), which are then quickly used up by the BOD of the effluents, thereby minimizing organic matter sedimentation. It basically takes advantage of the natural algae and put them to good use, powered by the same sun, supplying dissolved oxygen directly in the water. With solar panels floating on the surface, this type of waste treatment technology would not work.

  • Is Californian homes an SI unit or an imperial one? And is there a table to translate that to cow farts?

    • It’s an SD unit like the thaum – Standard Discworld. (Homage to the late great Terry Pratchett RIP).

    • Ha, ha, ha! Should be California homes and 12.5 MW though. And asssumed to be DC?

    • You would need a cowculator to count the cowlories of the cowfarts. How many cowlowatt hours do you need? Welcome to Cowlifornia.

  • Mall parking lots would be ideal for solar panels, it would provide shaded parking, the power can be used by the mall and it will not disturb any wild animals, vegetation and environmental impact would be minimal. This would work on school, church, hospital parking lots also, plus commercial roofs should be utilized, combined with battery storage it would reduce the amount of Rural land need for generating and transmission line to get it to market where it is needed.

    • IKEA do this already.

      • Yep, they doos!

    • “This would work on school, church, hospital parking lots also, plus commercial roofs should be utilized…”

      To see all of the above working right now, just Google; Lancaster California solar power, and click images. And add churches, stadiums, theaters to the list. As panel and installation prices fall, it’s coming.

    • installing solar over parking is ~30% more expensive than roof mount. so in terms of cost…roof mount > ground mount > floating / parking lots etc. we need to maximize output from low hanging fruit before moving on to other nice to have or longer ROI projects. Granted, in some places, the benefit of the shade justifies the extra expense.

      • There might be additional value in collecting and storing rainwater for irrigation.

        That thought brought to you from drought stricken California….

        • I’m there (in cali) and agree 🙂 I don’t think most parking lot solar installations currently take this into account but as you mentioned that, I remembered a few that I have see that have.

        • Except – we don’t have any rainwater!

      • If you add in the cost of long distance transmission lines ( building and maintenance ) more complex and time consuming EIR’s plus the legal fees from the court fights and the delays from these actions, then using parking lots would seem to be cheaper and faster in the long run with less complex and time consuming EIR’s. Generate Locally and Use Locally should be the priority along with reduced cost’s and delays, after all parking lots are already flat and that saves a lot of time and money on site preparation.

  • I was told the maintenance people love it.

    • Are you auditioning for “Commentor with lowest content input?”

      If so, you’ve made a good start.

      • I will let you elaborate on that one, Bob.

  • cool project, I hope they are putting on roof top solar also….just wondering what they meant with the “You get pushbacks on aesthetics”.

  • California should put these over all their reservoirs . . . generate electricity and reduce evaporation of valuable freshwater.

    • Right now most would be sitting on dry land….

    • I don’t know if the extra expense of floating systems etc is justified. Maybe put caps over the reservoirs…then put solar on that? dunno,

  • In Dec 2014 a local (Malta) project started testing the first PV systems on open sea. This is part of a project (SolAqua) which aims to develop viable PV systems on the sea. In small, densely populated countries or cities the cost/lack of availability of land makes this an inteesting proposition. Our installaiton of 4 panels at sea is meant to prove this is viable.
    Contact me if interested in knowing more.

Comments are closed.