Let’s float some more solar farms

By Jeremy Williams 

There has been some unwarranted fussing about solar farms in the UK recently. There is an enduring perception that they compete with food production and should be restricted. I’ve described why that’s not the case, but even if land is in short supply and isn’t suitable for solar panels, there are other options. Yes, there are roofs, the natural habitat of the PV. There are options above roads, on bridges and over car parks, and the one I wanted to highlight today: solar panels on water.

As an example, here’s the array on the Queen Elizabeth II reservoir near London. It was briefly the world’s largest floating solar farm, though like most renewable energy records that crown has now gone China’s way.

The QE2 array has over 23,000 panels mounted on 6,000 floats. It was assembled onshore and then pushed onto the water, where divers secured it in place with a series of anchors. The energy created is used by Thames Water in their water treatment plant. But floating solar panels do more than generate electricity.

First, it’s good for the panels. Solar PV doesn’t perform as well when it overheats, which means that production can be sub-optimal on hot summer days. Those are good sunshine days, of course, so you want to be able to capture as much of that light as possible. Panels over water are naturally cooled from beneath, and so their location adds to their efficiency.

Secondly, panels shade the water and reduce evaporation. This is particularly important in hot countries, where water scarcity is an increasing risk. It’s a problem here in England as well. Population density and high consumption rates mean that water per capita is surprisingly low for a country famous for rain. We can’t afford to lose too much water to evaporation in the summer, and solar arrays on our reservoirs might help to buffer against future droughts and water shortages.

Note that I specify reservoirs here. Nobody is coming for the Lake District or your favourite loch. Even though the visual impact of floating solar is pretty low, covering local beauty spots with panels is not going to be a popular idea. There are plenty of reservoirs that aren’t open to the public, and those are good places to start. It’s there, on water infrastructure rather than natural lakes, that the benefits of reducing evaporation will be most useful.

Beyond the UK, some of the most promising locations for solar over water are on irrigation canals. If you can reduce evaporation from irrigation systems, that’s more water reaching fields and being put to productive use. California has thousands of miles of irrigation channels, and the first pilot project to put solar on them is underway at the moment. A study into the idea has suggested that the solar power could be used to run the irrigation pumps as well. Since that’s usually done with diesel power, it would reduce emissions as well as save water.

There’s no reason why it shouldn’t work in California since it’s working already in India – and here’s a rather impressive aerial view of a solar canal.

Solar projects of this type are reducing emissions with clean energy. They’re also a form of climate adaptation, making irrigation systems more resilient to dry spells and heat.

First published in The Earthbound Report.