Floating solar panels

I posted recently about the idea of covering large parking lots of stores like Walmart with solar panels. This would provide two benefits. One is that it would provide shade for their customers’ cars, no small benefit in hot areas when going to a car that has been baking in the sun can result in the door handles being too hot to touch and the inside stiflingly hot. The second is that it provides quite a lot of energy that could be used to service their buildings, provide charging stations for electric vehicles, and even sell surplus energy to the grid. I noticed that the parking lot nearby that services the city hall and public library has installed solar panel coverings and has a charging station. It is small in size but the idea seems to be catching on.

Now comes along another idea that also seeks to cover large expanses with solar panels, and this is to put them on floating rafts over large bodies of calm water, like lakes.

Floating solar panel systems are beginning to boom in the United States after rapid growth in Asia. They’re attractive not just for their clean power and lack of a land footprint, but because they also conserve water by preventing evaporation.

A study published in the journal Nature Sustainability in March found that thousands of cities — more than 6,000 in 124 countries — could generate an amount equal to all their electricity demand using floating solar, making it a climate solution to be taken seriously. In the process, they could save roughly enough water each year to fill 40 million Olympic-sized swimming pools.

Zhenzhong Zeng, a contributor on that study and associate professor at the Southern University of Science and Technology in Shenzhen, China, said in the United States, counties across Florida, Nevada, and California have the potential to generate more power than they use. Of course, they would need a mix of energy to actually provide power all hours of the day, Zeng said.

The concept of floating solar is simple: attach panels onto rafts so they float on water instead of blocking off land that could be used for agriculture or buildings. The panels are sealed and act as a lid that brings evaporation down to nearly zero, benefiting regions like California that repeatedly experience periods of drought. The water also keeps the panels cool, allowing them to generate more electricity than their land-mounted counterparts, which lose efficiency when they get too hot.

The world’s largest array so far is the 320 MW Dezhou Dingzhuang Floating Solar Farm in Shandong, China. North America’s largest, by comparison, is a fraction of that — 8.9 MW at the Canoe Brook Water Treatment Plant in Millburn, N.J., owned by New Jersey Resources Clean Energy Ventures, which operates utility-scale commercial as well as residential solar systems across the Northeast.

However, there are issues to consider.

But high up costs up front remain a barrier. Bartle estimates floating solar costs 10-15% more than land solar initially, but owners save money in the long run. Deeper water can increase installation costs, and the technology can’t operate on fast-moving water, on the open ocean, or shorelines with large waves.

Engineers are working on other challenges. If the solar panels cover too much of a water body’s surface, dissolved oxygen levels could change and water temperature will drop, which could harm aquatic life. Researchers are looking into whether the electromagnetic fields generated by cables could negatively influence aquatic ecosystems, however, there’s no evidence of that yet.

Like with parking lot arrays, floating panels is an idea that seems obvious once it is pointed it out!


  1. says

    The bit about O2 levels isn’t a necessary impact. If the panels are propped up a bit and free access is given for air to travel beneath, you can cover more of a body of water before that becomes a problem (although evaporation rises in that case, so you have to decide if you want more evaporation with a larger area covered but not sealed, or if you want less evaporation, with less area covered, but with a corresponding drop in power generation).

    What I found really interesting was a project in India where irrigation canals were covered with solar panels propped up on structures above ground. The shade dramatically reduced evaporation, but this wasn’t a floating structure and the air/water interaction was unimpeded. Here the construction costs to stably lift the panels up to their intended height was somewhat more than the cost of other solar installations, but the benefits of installing on land already public as well as avoiding the reduction of agricultural land and increasing water loss with climate change were seen as worth the increased initial expense. While the canals are water habitats (this isn’t filtered, potable water we’re talking about, just water diverted from a river) in what I remember from the articles I read there wasn’t any discussion of effects on the habitat other than comparing the solar panels to shade trees and saying that the shaded temperature (would? / would probably?) benefit frogs and fish.

    IIRC the articles about the project in India was from western India. Possibly near Goa? I’m not sure, exactly.

  2. Trickster Goddess says

    A third benefit of the parking lot solar panels is that by shading all those acres of asphalt it could cut down on the heat island effect and generally cool down cities a bit.

    I recently read that California has also started to build solar panels over irrigation canals. I was pleased to hear about that since it is an idea I had about 20 years ago. It makes sense to make sure more of the water gets to where it can be used instead of just evaporating back into the atmosphere. Apparently having the panels over water will also cool them and increase their efficiency.

  3. Holms says

    Aquatic O2 and living conditions will also be affected by the large swathes of shade cast by these rafts. Less sunlight entering the water means less photosynthetic life and colder waters. Changing the environmental conditions of an ecosystem usually has detrimental effects.

  4. Jazzlet says

    Holms @#3

    Given a heating world cooling the water may well be good for the habitat. The panels over the canals in India do let some light in as you would see if you followed John Morales’ link.

  5. Silentbob says

    Humans: Oh noes! We thoughtlessly destroyed the environment!

    Also humans: It’s okay! We can pave over the waterways taking all the energy that would have been used for photosynthesis!

    Also also humans: Great idea! What could possibly go wrong?

    I especially like this comment:

    Given a heating world cooling the water may well be good for the habitat.

    Translation: “Given we’ve totally fucked the environment in one direction, if we totally fuck it in the equal and opposite direction I’m sure it will all even out in the end”. Lol.

    Meanwhile, space based solar power has been a solution in plain sight for at least half a century.


  6. says

    Uh, yeah, that “solution” has been in plain sight since at least the early ’70s. So have all the problems described in the article you cited. I’d love to see it happen, but it still doesn’t look likely.

    (Also, every micrometeor strike would likely knock the microwave gun off course enough to miss the ground receivng station altogether; and there would be no power received until the satellite could reorient itself and re-aim the microwave gun. And this could happen with every micrometeor impact.)

  7. John Morales says

    Again, this is not new, though the tech is better now.

    Abstract: Both energy and availability of water with good quality are essential for the well-being of humans. Thus, it is very important to study the parameters that would affect water quality, so as to come up with mitigation measures if water quality would be at risk or negatively affected. Moreover, it is very important to always search for new energy resources, especially if they are renewable. This research study is concerned with studying solar canals and their effect on evaporation and water quality variables of canals covered by solar cells, as well as the effect on power production. Both a mathematical model and an optimization study were done, in order to determine the previously mentioned effects, and thus, to determine the most favorable covering percentage of the case study canal’s area that would lead to minimum evaporation volumes, maximum power, and yet preserving and meeting the standards of the water quality variables of the covered waterway. Water quality variables that were investigated are dissolved oxygen concentration, algae, nutrients, and pH of the water. It was found that, between 33% and 50% covering of the canal, the optimum conditions will be met.


    In passing, canals are hardly natural, and are certainly not a riparian environment.

    (Algal blooms are natural, but unfortunate for waterways)

  8. says

    The fundamental problem with putting a solar power plant in space is, you want the electricity on Earth. Now there are basically two ways of accomplishing that. One is an extension lead several hundred megametres long. I’m sure a trailing cable hanging out of the back end of a rocket isn’t going to interfere much with the first part of its journey, through the atmosphere. We can always use a bigger rocket, if we need to ….. There might be some teeny issues with the forces it’s going to be subjected to, since an object at any given distance from the Earth will have a certain natural period that its journey around the planet would take. Still, it would be the first step towards an actual Space Elevator.

    Two is to use a space MASER to produce an intense concentrated beam of microwave radiation, which is then aimed at a ground station for conversion back to usable electricity somehow. (This also creates a no-fly zone, but at least there won’t be many complaints from anyone who strays into it accidentally.) Now, when you have triangles with sides hundreds of megametres long, a milliradian’s worth of angular difference corresponds to hundreds of kilometres. Any bit of space debris impacting on the MASER with enough force to alter the angle of the beam risks creating a remake of a scene from Independence Day.

    Whatever problems we may have with Solar panels on Earth, “running out of places to put them where they will still get 3.6MJ worth of photons per square metre every hour the Sun shines” isn’t one of them.

  9. KG says

    Something I’ve not seen explored is putting solar panels, and wind turbines, in the upper atmosphere, above clouds (for the solar panels) and at heights where the jet stream (for turbines*) could be exploited. A cable a few kilometers long seems much more feasible than one all the way to earth orbit, or the power could be used in situ to make fuels from atmospheric gases. I’m sure there are problems with this, but it seems much more feasible to me than space-based solar.

    *Of course you need either to hold the turbine still, or at least moving more slowly or in a different direction to the wind, but I imagine there are considerable variations in wind speed over relatively small distances.

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