Photovoltaic solar panels are wonderful things, capable of capturing mere light and turning it into useful electricity. They’re often installed on residential and commercial rooftops for offsetting energy use at the source.
However, for grid-scale generation, they’re usually deployed in huge farms on tracts of land in areas that receive plenty of direct sunlight. These requirements can often put solar farms in conflict with farm-farms — the sunlight that is good for solar panels is also good for growing plants, specifically those we grow for food.
One of the more interesting ideas, however, is to create solar arrays that float on water. Unlike some of the wackier ideas out there, this one comes with some genuinely interesting engineering benefits, too!
Not As Crazy As It Sounds
“Floatovoltaics”, as they like to be known, come with significant engineering benefits relative to typical land-based installations. One of the primary benefits is that of cooling. Solar panels, like many other electrical devices, benefit from being kept in a nice cool temperature range. Of course, being exposed to the sun means that, when generating electricity, solar panels are in fact forced into operating at elevated temperatures. With the average commercially-available photovoltaic panel hitting a peak efficiency of only around 20%, and only roughly 1,000 W/m2 available from the sun, solar panels are already up against it when it comes to producing decent amounts of electricity. The estimated efficiency benefit from floating a solar array on water is on the order of 5-6% according to researchers from the Institute for Energy Technology in Norway; certainly nothing to sniff at. Fully immersing panels in water has shown even greater improvements, up to an 11% boost in efficiency in some tests.
The benefits of floating solar panels don’t end there, either. When floated on a reservoir, for example, solar panels can shade the water course, reducing evaporation. Proponents suggest that this effect can save up to 90% of water that would otherwise be lost to the air in dry climates, through a combination of shading as well as reducing the impact of wind. The lower levels of light reaching the water also have the benefit of reducing algal growth as a further bonus.
For these reasons, floating solar is most often proposed to be colocated with pumped hydroelectric storage dams. These facilities rely on storing large amounts of potential energy in water, and any water lost to the atmosphere is water that can’t be used to generate electricity later. As a further benefit, these facilities already have infrastructure tying them into the electrical grid, making wiring up solar generation more cost-effective compared to developing arrays at greenfield sites.
Indeed, perhaps the biggest benefit often cited when talking about floating solar is that it reduces the need to secure large tracts of expensive land. Instead, existing watercourses like reservoirs can add solar, providing electrical generation to the grid without needing any extra footprint on the ground, barring a few utility boxes.
Floating solar panels on water also has the benefit of reducing the environmental impact and waste of cleaning operations. Rather than having to pump in clean water to wash panels as in a land-based installation, a floating array can simply be cleaned with the very water it is floating on. Little of that water need be lost either, as it can simply run back down off the panels.
Drawbacks
There are drawbacks to floating solar installations, however. They must be designed carefully to manage and avoid corrosion wherever possible, as the wet environment can be harsh on cabling, framing and components. This is only compounded in salt-water installations, which increase the likelihood of damaging corrosion further. Of course, corrosion is a manageable problem, with all manner of freshwater and seawater hardware having been designed to withstand these environments. However, it adds cost and time to deal with these problems that aren’t such an issue in a typical land-based installation.
The array itself must also be designed and assembled in such a way as to not only float, but also resist the dynamic forces of being on the water. In inland reservoirs, this can involve being blown around or rocked by small waves kicked up by the wind, or even dealing with rocking, splashing or spray from water inlets when installed with pumped hydro. Off-shore applications are possible too, but locations must be chosen carefully to avoid tidal forces and weather from destroying the hardware, as demonstrated by the destruction of the Yamakura dam in 2019.
Naturally, maintenance is more difficult as well, as a floating installation is more difficult for technicians to work on and comes with additional health and safety risks as well. Dealing with all these engineering requirements can add significant cost to a floating array versus a more typical land-based installation.
The Future Is Already A Reality
Far from a pie-in-the-sky thought exercise, floating solar arrays are actually already in use around the world. The biggest installation presently operational is the 320 MW installation in Dezhou, China. The floating array is expected to generate 550 million kWh of electricity per year, located in a reservoir near to the local coal power plant. It’s also colocated with a 100 MW wind farm and 8 MWh of battery storage on site.
It’s not a one-off facility, either. Projects have been undertaken all over the world, from a 6.3 MW installation in London to the 4.78 MW Healdsburg, California array that claims to be the biggest in the United States.
However, the biggest projects on the cards are in Asia. South Korea plants to build a gigantic 2.1 GW solar farm floating in the Yellow Sea. Expected to cost on the order of $4 billion USD, the project will span an area of 7,000 acres and feature 5,000,000 solar modules to generate its peak output.
Meanwhile, an Indian project hopes to construct a 600 MW floating solar project in the Omkareshwar Dam. The project hopes to begin power generation by 2023, exceeding the 520 MW capacity of the hydroelectric power station colocated at the site. The dam itself primarily serves to store water for irrigation purposes, with the solar installation likely to maintain much more water in the reservoir due to reduced evaporation.
Installation of floating solar is ramping up year-on-year as the technology matures and various jurisdictions see the benefits to be had. With the promise of generating more power, more efficiently without requiring more land purchases, it’s hard to deny the benefits of floating solar. Expect it to spread rapidly to reservoirs and calm coastal areas near you – presuming you live somewhere sunny!
> project will span an area of 7,000 acres
Wait a second. Killing 7000 acres of sea life that would be completely deprived from sunlignt with completely unknown consequences of the artificial permanent temerature gradient of huge size in open sea hardly even close to “benefit of reducing the environmental impact”. How that differ from the fields of floating plastic garbage in ocean everybody is mad about?
May be it is already a time to drop that “environmental friendly” thing about solar panels, at least here, on technical site? Solar panels are just one of many ways of getting electricity with its own drawbacks (including environmental ones) and benefits, nothing more.
Agreed. I find the modern over-use of the phrase “green” absolutely cringeworthy. Algae is green. Money is green.
Solar panels are not. They are a power-generation scheme that has a DIFFERENT (not necessarily less) impact on the environment.
And the floating solar business… My first thought was… OK… reduced algal growth, reduced evaporation, and potentially more efficient use of urban square footage. But what are the eco and local-climate effects of THAT?
And if (when) they catch fire… as depicted in the video? Burning plastics and who knows what else–not to mention fire-retardants or foam sprayed on top to douse the flames–leeching/draining directly into the drinking water?
People in California recoil at the miniscule lead content in brass faucet fittings, but they’d drink THAT?
Oops… never mind… this appears to be in China, Their Baowu steel factory puts more CO2 in the air than the entire country of Pakistan, and China is responsible for 3/4 of the plastic bottle trash floating in the ocean. Nothing to see here.
Their people will drink what the CCP TELLS them to drink, and they’ll LIKE it.
“People in California recoil at the miniscule lead content in brass faucet fittings, but they’d drink THAT?”
“minuscule”
(Sorry…)
Don’t you think the planners have maybe considered the environmental impact carefully and deemed it to be acceptable? Or are you a marine biologist specialising in the sunlight requirements of the ecosystem of the Saemangeum region?
Given the amount of money involved in 5 million solar modules, one should at least entertain the possibility that the planners hired as many experts as necessary to find the one willing to say “sure, I don’t see any downsides.”
Don’t you think that coal power plant planners have maybe considered the environmental impact of burning fossil fuels carefully and deemed it to be acceptable? Or are you a climate scientist specializing in the CO2 levels of the ecosystem of the Saemangeum region?
The pro’s con’s list doesn’t seem too considered to me.
There seems to be a lot of obvious things missing in the con’s list.
And then – no algae because … yes but when a change to the environment so it’s unfriendly to one biological element then it becomes more friendly to a different biological element.
I don’t know about the Yellow Sea, but reducing algae in man made dams is usually a good thing. Due to fertiliser runoff from farming, lawns and urban areas (think lots of dog poo and food waste) there is a real problem with excessive algal growth in inland waterways. Far from being a good base for the food chain, excess algal growth removes oxygen from the water, which kills higher lifeforms that used to live there. The keyword to search here is “eutrophication.”
If the dam is used for irrigation, the benefits from reduced evaporation can be significant too. These dams are usually in dry, hot places where water loss through evaporation can be large.
So as a measure of harm, what percentage of the ocean would be affected?
Yeah, *reservoirs* are uniquely freshwater environments, thus the damage to the sea life you express concern about is invalid.
The comment you’re replying to is referring to a project in the Yellow Sea, an area of ocean between North-East China and the Korean peninsula.
Spot on! This reminds me of the recent news that a much-hyped “green” Shell carbon-capture and storage (CCS) hydrogen facility produces as much emissions as running 1.2 million vehicles.
https://www.cnbc.com/2022/01/24/shell-ccs-facility-in-canada-emits-more-than-it-captures-study-says.html
https://www.globalwitness.org/en/press-releases/shell-plant-emissions-million-cars/
May as well ask this about human use of any of the surface area of Earth. Farming monocultures replacing native biodiversity; homes, roads, and businesses replacing any biodiversity; rivers straightened and floods stopped.
What about underwater plant life that would be shaded?
A lot of algae relies on sunlight, lives in CO2 and feeds fish.
But it’s not scary like nuclear power.
how strange. what could be the cause of that?
Low temperature reactors that can’t melt down. Also, reactors that use yesterday’s reactors waste fuel as their main fuel source.
In the meantime, I’m still waiting for someone to figure out how to deal with all the solar cells when the time comes to discard them…
+1
“Uh, water ecosystems? What are those?”
I think the point was you can float them on reservoirs where sunlight, evaporation and algae are a nuisance and not a feature.
A friend of mine has been trying to deploy floating solar for at least 10 years, and this was one of his primary selling points for his municipal proposals: put these in cooling ponds for coal or nuclear power plants, where A: you already have the electrical connections, B: there’s nothing in the water because it’s controlled to prevent algae in the heat rejection intercoolers/cooling towers, C: people don’t rely on the lake for recreational purposes.
That sounds like an excellent idea. The possible environmental impact is reduced to a minimum.
The issue with putting solar panels on a cooling pond for a power plant is that, as mentioned in the above article, they reduce evaporation. In a cooling pond this is the exact opposite effect that you want. The evaporation is one of the main mechanisms that the waste heat is removed from the power plant.
Another possible issue with nuclear plants is the regulatory risk of putting solar panels in the cooling pond. What’s the risk of one of those panels breaking free and blocking the water inlet? Maybe it is a small risk, but unless it’s known precisely how small there’s no way that anybody would go forwards with it. Yes, there are safeguards against the inlets being clogged, but (to my knowledge) that specific kind of failure/risk hasn’t been analyzed yet.
So, spray the water over the panels.
> people don’t rely on the lake for recreational purposes.
To add my two kopecks, NPP cooling ponds and recreation aren’t always mutually exclusive. I grew up in a Russian city not far from a nuclear power plant, and the cooling pond was known as *the* place to go swimming, because the water was always pleasantly warm.
And as a side benefit you could see each other when swimming at night. :D
I’m sure it was the secondary cooling loop, not the primary.
Plus, evaporation is cast in a negative, but for local weather it may play an important role.
I just want to see the relative $/W. Does the land cost and cooling efficiency actually result in a net improvement despite added costs of flotation and increased waterproofing efforts
A project in Malaysia is claiming an LCOE of $.051/kWh. This compares to $.035/kWh for a typical utility-scale solar installation. NREL seems to be a bit more generous with an estimated cost just 25% higher than land-based.
many aquatic /marine comunities thrive in shaded or semi shaded environments,I have spent much time snorkling in a cove covered with lily pads and the place is SWARMING with life and algae,many of the existing floating solar plants are in the resevoirs of hydro electric dams,so man made and right next to power sub stations,etc.the article misses that solar has been a boon for small
and medium scale farming as they tend to have large buildings
with plenty of roof,and often some land unsuitable for agricultire.
tenting canals with solar will/does reduce evaporation,plus what evaporation does occur lowers local temperature and increases
pannel eficiency, while useing no new land.
Thank you for this information.
Interesting concept, thank you for the article.
By the way, I took a look at the 11% efficiency improvement paper: as far as I understood they obtained increased efficiency as they accounted for the reduced incident light power when cells are submerged. But, what is the point of submerging cells? To get less power converted with higher efficiency?!
When 700W/m^2 incident radiation can be converted to 120W by a cell standing on liquid surface, why prefer extracting 33W from the same cell at 6cm depth? Am I missing something?
That paper seems quite vague, to say the least.
actually, from a fire containment point of view, they should compartmentalize the farm like they sometimes do with forests so that when a fire occurs, not the whole shebang will go up in flames.
What is the balance between sunlight providing light for growth of algae vs sunlight not reaching the water to sterilize it. Sunshine contains a lot of sterilizing ultraviolet light. Areas in my yard that do not get sunlight actually get more fungal growth.
Also, birds. You’ve now provided perches for infinite birds and those birds like to poop. If that goes in to the water and there is no light to sterilize the mess, then what?
However! There are some advantages. For instance instead of one massive pontoon. You can make smaller ones (600 feet maybe) that have small electric trolling motors that spin the entire island to track the sun throughout the day.
“Also, birds. You’ve now provided perches for infinite birds and those birds like to poop. If that goes in to the water and there is no light to sterilize the mess, then what?”
Imagine bacteria doing this job. Sunlight sterilizes no poop in a lake. Poop will drop on the ground and be eaten up by happy microorganisms.
Sorry, thats just not how things work otherwise we would just all be pooping in our water reservoirs.
What? Never heard of a bottom-feeder?
There’s a whole subset of the marine ecosystem that sits on the bottom eating fish- (whale-, shark-, etc.) poop. Ghost shrimp, for one…
That implies that it would contain itself to the lake which is impossible to ensure.
Maybe in the Antarctic where the hole in the Ozone is?
The sterilizing UVC light you are referring to is blocked by the Ozone layer everywhere else on the planet. A good thing too otherwise any exposed skin would be sunburnt in minutes blistered and cancerous after a few hours exposure! Not to mention you’d get cataracts and/or go blind over slightly longer time frames.
Makes me wonder what the surface area of waste/tailing ponds is world wide, floating solar panels on these might be slightly more difficult but it sure as hell would not disrupt any marine communities.
If only there was a nicer way to write “550 Million kWh”… some sort of larger unit…
19.8 zettaergs
0.55 PWh Peta Watt hours
550 TWh Tera Wh
550 000 GWh Giga Wh
550 000 000 kWh kilo Wh
550 000 000 000 wh
You missed mega. 550,000,000 kWh = 550,000 MWh = 550 GWh = 0.550 TWh.
So I assume that when talking about Earth’s circumference you’d say 40 Mm instead of 40000 km?
On the water has some conversational value, but what about deployment in the desert if you’re worried about land costs? How much wildlife could thrive in deserts with cooler temperatures (you wouldn’t deploy these where the heat would be excessive, because the return on power per panel would dive below sensible). With all the land in the southwest that is arid, deploying solar farms make some sense. Of course the location compared to grid interties comes up with that suggestion.
In residential deployments on a rooftop using a water based heat exchanger to provide cheap hot water while keeping the panels cool would be sensible. Most designs I’ve seen are “either / or” Either the panels provide water heating OR power, rarely both. Wouldn’t such a hybrid system make sense for residential use?
Solar generated electricity AND pool water heating? I’m down.
What impact will this massive sheet of panels have on water oxygenation? will it be a 7000 acre patch of suffocated water.
How are the floats designed, sure if the thing is like those floating balls that stop evaporation, they also clog the air/water interface, never mid the shade of the panel, it is the float area that concerns me.
In the meantime, I’m still waiting for someone to figure out how to deal with all the solar cells when the time comes to discard them…
Give them to me. I will crush them up and make roads out of them.
SOLAR FREAKIN ROADWAYS!
The cells are not the issue (it’s silicon mostly, with some aluminum). But the frame itself can be less than recyclable (for plastic backed ones).
Otherwise it’s much less problematic than coal hashes, heavy fuel or highly active actinides.
In Lithuania, first floating solar panels just drown to the bottom after heavy snowstorm in first winter :D
Seems like a Lithuanian design problem. How often do you get snow?
Wow so much bitching and moaning here.
This is a marriage made in heaven, reservoirs are often hydro-electric, so there’s already electric distribution equipment. It’s not a natural lake, and fish actuallly prefer the shelter of solar panels rather than the open water, which is usually deep enough in the center that bottom vegetation does not thrive. Water from the reservoir can be used to clean and cool the panels. The panels don’t have to form a 100% coverage skin over the water, they can be planned, and even moved, to provide the optimum level of evaporation, sunlight for shallow-water plant-life, shade for fish, etc, etc. To me, there is nothing about this basic idea not to like, though of course the implementation needs to be honed.
“corrosion is a manageable problem”
so is travelling to mars.
i love these statements. obviously some think money can just be printed out of thin air. and saving the planet is priceless!
>corrosion is a manageable problem
Tell that to commercial vehicle operators, car owners, sailors…
wrong, you skipped mega
I got there first even though I arrived later! I think you need to unblock a certain script (though I don’t remember which one) to get your replies to end up in the right place.
I always laugh at articles about Generating electrical power on top of a Lake, Pond, or Ocean. Its a stupid idea. Electricity plus Water is dumb. I could see cooling the electrical panels by pumping ground water through them. Operating a power plant on top of a lake isn’t something I would invest in. Nor would I be one to get into a boat to go work on them.
Maybe the people who dream these things up should become a boat owner first. I would love to hear their opinion after they pull their boat out and clean the hull two or three times a year. Then they could see for themselves how fast the metal parts oxidize due to constant exposure to water. Or how hard it is to navigate against a headwind.
I bet the birds would love nesting on the warm solar panels. I would pick one in the middle where you have to navigate a ways to come and disturb the nest.
I suppose a farm on a lake in the desert is better than a farm up here in Western NY. We drive by many panels covered in snow. Haven’t seen anyone shoveling snow off solar panels yet. My neighbor hasn’t gone up and shoveled his roof either.
Maybe the snow is transparent to sunlight and is cooling the solar panels increasing their efficiency by keeping them cool. I doubt that.
Just curious as to why we can’t put panels in cold areas that have ice year round, Antartica for instance. The panels get more efficient due to being cold, and they shade the ice to keep it from melting?
To reduce the “greenwashing” effect, no solar arrangement should be termed “farm.” Obviously, “farm” connotes all manner of gentle, fine things to the general public. Call them “arrays” or something even less benign. Thank you for the article.