Solar panels lose output as they warm up, and almost nobody outside the industry knows it.
A silicon cell gives its rated power at a mild temperature, then drops a few tenths of a percent for every degree above that.
On a hot roof a panel can run far above air temperature and quietly give away close to a tenth of its output.
So heat is not a bonus that comes with sunshine. It is a tax on it.
Anything that pulls that heat away is worth real money.
Water pulls it away better than anything.
Under the surface instead of above it
The usual floating array sits on pontoons with the panels held clear of the water, staying dry and catching wind like a sail.
This one does the opposite and lets the sea close over the panels during working hours.
Three things follow at once. The water carries heat away continuously, so the cells run near sea temperature instead of baking.
The water also adds weight above the structure, which damps motion and stops the array behaving like a loose lid.
And a surface under water does not collect dust, salt crust or bird droppings, because the sea rinses it on every swell.
Losing a little light on the way through the water is the price, and the trade comes out in favor of wet.
The ring was going to be scrap
A fish pen is held open by a collar, a huge floating ring of black plastic pipe with a net hanging inside it.
Those collars wear out on a schedule. Ropes saw at them, the plastic fatigues, and a farm retires them long before the material is finished.
What is left is a ready made circular float, already engineered for the exact water it is sitting in and already certified for that site.
Stretch flexible panels across the ring and the hardest part of any floating solar project, which is the float, arrives for nothing.
The array in question is rated at 290 kilowatts and sits at a salmon farm on the Norwegian coast.
A smaller unit of 160 kilowatts went to a cod operation.
Neither farm had to build a float, tow one out or get a new structure approved, which removes the three slowest steps in any project on water.
What a remote farm actually burns
A fish farm without a cable to shore runs on diesel, and it runs on diesel continuously rather than in bursts.
Feed barges, lighting, cameras, sensors, pumps and accommodation all draw power around the clock, and a generator sized for the peak spends most of its life loafing at low load.
That is the worst way to run a diesel engine, for fuel burn and for maintenance both.
The technology demonstrator went into the water in November of 2020 at a fjord site, and the first commercial arrays followed in the years after.
The developer describes the result as a significant cut in diesel use and in the carbon that goes with it.
A significant cut is not a measured number, and that distinction matters here.
The figure nobody has published
No percentage has been put on the diesel saving by the company itself in the material available.
Other Norwegian sites with floating solar have been reported as covering most of their demand, but those are different arrays at different latitudes with different loads, and borrowing a number across them is not fair to either.
Latitude is the real question. A fjord site in Norway gets long summer days and almost nothing in December, exactly when a heated feed barge wants the most power.
An annual figure would settle it and none is public, in the way that a record cell or a new recycling plant gets announced well before a year of data.
The trade coverage was careful to describe the system as reducing the need for generators rather than replacing them.
Why aquaculture is the right first customer
Floating solar has a customer problem almost everywhere else.
Put an array on a reservoir and the power has to travel to somebody, which means a cable, a substation and a grid connection that costs more than the panels.
A fish farm is different because the demand is already floating right beside the supply, twenty yards away, with no cable to build at all.
The competition is not a grid tariff either. It is diesel delivered by boat to a fjord, which is close to the most expensive electricity anybody in the country buys.
Against that benchmark an array does not need to be cheap or efficient. It only needs to work in cold salt water for a few years, as the aquaculture trade press framed it.
The fish pen ring was never the clever part of this.
The customer standing next to it was.
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