Land-use constraints are forcing developers to look at floating PV. Proponents say the concept makes good economic sense.

Recent months have seen a flurry of floating PV plant announcements amid growing land-use constraints in major solar markets. This month, for example, LG Electronics announced a partnership with Korea Water Resources to develop floating plants in South Korea. And the Energy Bureau of Anhhui Province in China trumpeted the grid connection of what is believed to be the world’s largest fishpond solar plant. The 20 MW array, located on a coal mining subsidence area of Huainan City and built by Xinyi Solar, is part of a project that when complete should cover 1,640 acres and boast a total of 300 MW.

Brazil also inaugurated the floating PV concept, with two plants of 1 MW each aimed at proving the benefits of combining solar with hydro power. If successful, the Brazilian plants will be expanded to 5 MW each from 2017.

These plants come on top of an already significant number of floating PV projects around the world, including a 13.7 MW installation on Yamakura Dam, Japan, and a 6.3 MW system in Walton-on-Thames, UK.

The primary driver for floating PV is that in some places it is easier to build arrays on freshwater bodies than it is to find open land.

An example in this sense is the Netherlands, where, according to research from Solarplaza, an increasing number of PV projects in the pipeline will be built on water. Land-use constraints explain why most of the floating plants to date have been built in Japan.

However, proponents of the concept say floating solar plants potentially offer a number of other advantages over land-based projects. “We are the most cost-competitive form of PV in Japan, because of the cost of land,” claimed Eva Pauly-Bowles, international sales director for Ciel & Terre International, which has worked on up to 95% of all floating projects to date. She said the relatively high costs for land, civil works, seismic-proof foundations and grid connections made Japan “the ideal country” for floating PV as an alternative to land-based installations.

The support structures used for floating plants can account for up to 25% of total project costs, she said, but this amount is often less than the cost of buying and preparing an equivalent area of land nearby. At the same time, the cooling effect of the water on the solar panels can increase annual generation.

This depends on the ambient temperature but can vary between around 5% on average in the UK and up to about 20% in hot countries such as Malaysia, according to figures from Ciel & Terre.

Operation and maintenance costs are also often reduced compared to land-based systems because the water needed for cleaning is available at source and components were less likely to overheat. Saltwater corrosion is not normally a problem since most floating PV is sited on freshwater bodies such as lakes and reservoirs. In addition, most balance-of-system equipment is usually sited on shore and is easy to access.

Floating PV is potentially less prone to shading and there is no maintenance associated with clearing away ground-based vegetation. A final advantage for floating plants is that many inland freshwater bodies, including industrial ponds, quarry and mine lakes, irrigation reservoirs and water treatment sites, have industrial or recreational uses. That means there is usually a nearby grid connection, reducing development costs compared to green-field land-based PV projects. “In every country there is a very large amount of man-made reservoirs built for or near an electrical consuming activity,” Pauly-Bowles stated.

She noted there could even be positive environmental effects from deploying floating PV. “There are not yet official third-party studies, but the shading effect will have a limiting impact on light getting through so it will reduce algal growth and stabilize water temperature,” she said.

Floating PV plants will be one of the topics discussed at the upcoming Solar Asset Management Asia conference on 2-3 June in Tokyo.