Solar power plants on water do more than on land

Indistinguishable from magic, Future Crunch often says of some technological and scientific advances. And that is definitely how I feel about floating solar power plants. I never knew there were so many of them – and that many more are planned.

Photo by Diego Madrigal from Pexels

Like me, you’ve probably seen pictures of massive arrays of solar panels on land and thought about how much land they are taking up. Indeed, they do – but put them on water, especially on an existing dam, as is happening to an astounding degree, and amazing things happen.

Not only do they generate renewable power and thus reduce greenhouse gases, but they complement hydro power generation – and they can use the power transmission lines that were installed for the dam. They support fishing industries; protect water levels in dams; and prevent algae growth.

“At face value, it costs more to float solar panels on water than to plant them on firm ground: about 10-20% more typically,” says China Dialogue in exploring the possibilities in Africa . “But there are advantages. Floating panels don’t take up land, suffer less from dust pollution, and do not require land levelling or removal of trees and buildings. They also often have a higher energy yield because the water is cooler than the land.”

“At hydroelectric reservoirs there are added benefits. Grid connections are already present to distribute the power. And the two sources of power may complement each other, with solar energy available during the day allowing engineers to save water for generating hydro-power after the sun goes down.”

“But the biggest add-on gain, particularly in the tropics, is that by covering the open water, the panels reduce evaporation, and so increase the hydroelectricity generating potential of the reservoir. In much of the tropics, reservoirs lose up to two metres of water from their surfaces each year, which can represent up to a third of the water they capture.”

Asia is far ahead

Sometimes called floatovoltaics, solar panels are mounted on a structure that floats on a body of water, usually a dam or a lake. Twenty plants were built between 2007 and 2013, and floating solar has really taken off since 2016, says Wikipedia. World floating solar output grew 100-fold from 2014 to 2018, the World Economic Forum reported in 2019, and could soon provide more power than conventional land-based systems. A recent report by the Korea Energy Economics Institute predicts the global market for floating solar panels will quadruple by 2025, and estimated that the total power generation capacity of floating solar farms had surpassed 3 gigawatts as of October 2020. By 2025, the volume will grow by another 10 GW, the institute said.

Kagoshima power plant. Kyocera, The Conversation

Asia is ahead in floating solar. China’s installed floating PV capacity is estimated to be larger than that of the next 11 countries in terms of installed base greater than 5 MW, according to one authoritative analysis, with many of the projects in coal subsidence areas.

In 2021, the world’s largest operating floating solar power plant was in China, and China and India together account for six of the ten largest such plants in the world. But that may not be so for long.

South Korea is creating the world’s biggest floating solar power plant near Saemangeum, on the Yellow Sea coast. The 2.1GW floating solar farm is expected to generate enough electricity to power one million homes. Its capacity is expected to be 14 times the size of the 150MW Huainan solar farm, currently the biggest operational floating solar farm in the world.

It’s not that easy to find a full listing of all the projects commissioned, planned or underway, but a Google search finds floating solar in Albania, South Korea, India, China, Indonesia, Singapore, JapanWest Africa, and the African continent. Some studies are being done of the potential for using flooded open pit mines for floating solar arrays.

But Japan, where the world’s first floating solar plant was built, may have the most floating solar projects. According to the World Economic Forum, Japan’s many inland lakes and reservoirs are now home to 73 of the world’s 100 largest floating solar plants and account for half of those plants’ 246 megawatts of solar capacity. As of 2019, the biggest Japanese floating solar plant sits behind the Yamakura Dam, covering 18 hectares, powering nearly 5,000 homes and saving more than 8,000 tonnes of CO2 a year.

Shading wastewater

These massive projects far exceed what is happening in floating solar in North America. Earlier this year, what is thought to be the largest such North American project was completed in California. The Healdsburg Floating Solar Project, a 4.78MW array across two wastewater treatment ponds in Sonoma County, was developed by White Pine Renewables and floating solar specialist Noria Energy. (A New Jersey project completed in 2019 on a retention pond, which generates 4.4MW, was previously thought to be the largest.)

The project, which placed 11,600 panels on about half of 15 acres of ponds, will provide 8% of the city’s annual electrical needs and puts the city’s municipal power utility, ‘at the cutting edge of solar energy development’, says the North Bay Business Journal. But while it will bring the city a step closer to its goal of securing 60% of its energy supply from renewable sources by 2025, power generation wasn’t the main concern.

Healdsburg was primarily focused on shading the recycled wastewater so as to prevent algae from blooming in the ponds, which hold treated water from the city’s municipal sewer system. Preventing algae growth, and preventing evaporation, could allow the city to sell recycled water to new agricultural users like fruit orchards or cattle pastures, generating savings for the city. For now, the city gives the treated wastewater to vineyards.


Solar Panels to Be Installed Above California Canals. EcoWatch, Feb. 10, 2022

Giant Floating Solar Panel Flowers Replace Coal in Korea and Become Tourist Destination. Daily Good, Mar. 7, 2022

Portugal’s floating solar energy auction sets world record negative price. Reuters, Apr. 6, 2022.

Biggest Floating Solar Park in Europe Perfectly Integrates in Portugal Reservoir. Good News Network, May 11, 2022

Floating Solar Farms Are a Game Changer. Reasons to be Cheerful, Sep. 12, 2022.

The floating solar panels that track the Sun. BBC Future Planet, Nov. 17, 2022

Long popular in Asia, floating solar catches on in the US. AP, May 12, 2023