Meet the world's largest floating solar-energy farm

The 23,000 solar panels to be installed in the outskirts of London will become Europe’s – and momentarily, the world’s – largest floating solar-energy farm. But despite its spectacle, only few people will be able to actually see it.

That’s because the solar panels will literally be floating on a large, manmade lake southwest of London – the Queen Elizabeth II reservoir at Walton-on-Thames, which is only visible to the passengers flying in and out of Heathrow Airport and a few neighboring estates.

The solar farm project is designed to generate electricity for the local water treatment plants. After five years of planning and £6 million (more than $8.3 million) in costs, construction is scheduled to wrap up in early March and will be operational for decades.

“This will be the biggest floating solar farm in the world for a time – others are under construction,”  Angus Berry, energy manager for Thames Water, the utility company that owns the site, told The Guardian. “We are leading the way, but we hope that others will follow, in the UK and abroad.”

Under Thames Water, the energy generated by the panels will help provide clean drinking water for nearly 10 million people in London and just southeast of the city.

But why solar panels on water? According to Mr. Berry, the answer is "why not"? The vast lake is already there, and the panels will only comprise 6 percent of its surface, so they won’t be harmful to the local ecosystem, he said.

Aside from a few waterbirds, including moorhens and gulls, and maybe some fish that somehow made their way into the water, the reservoir was never supposed to be a home to wildlife. The water is nearly 60 feet deep and has a constant churning stream that becomes drinking water. As more and more of London’s growth is concentration in the east end, most of its water sources – such as the Thames Water – are located west of the city.

But like recent trends in the US, the current British government has cut back on subsidies for solar and wind power. This means that future projects like this one may be in doubt, Berry told the Guardian.

“We have had to look very closely at the economics of this, at all stages,” he explained. “It is not clear what the future economics would be [for other potential projects].”

Similarly, in Japan, the global electronic company Kyocera is building a 50,000-panel solar farm on a reservoir in Japan’s Chiba prefecture. The decision to locate the farm on water was driven by the shortage of space in the country, and after it's complete, the panels will supply electricity for up to 5,000 households.

Still, the Kyocera solar farm and the Thames Water one are minuscule compared to some of the largest solar farms on land. In 2012, the Indian state of Gujarat built a $2.3 billion solar park that produces more than 600 megawatts of the country’s electricity. The park spreads across about 5,000 acres of land.

The next few largest solar power plants are in the US, where solar power is expanding rapidly thanks to a boom in the residential solar panel industry. But this trend of exponential growth is reflected globally.

According to energy experts at German solar association BSW-Solar, the world solar photovoltaic (PV) capacity will more than double in the next four years, hitting at least 400 gigawatts. In many places, solar power is the cheapest and most efficient option for private residents and public institutions alike.