More than 23,000 solar photovoltaic panels floating on the surface of the Queen Elizabeth II reservoir outside of London are powered up to supply energy to a nearby water treatment plant.

At a size of about 8 football pitches, this is Europe's largest solar farm. The 23,000-panel array was recently powered up at the Queen Elizabeth II reservoir outside of London.

Utilising this previously redundant space created some challenges for its builder, solar energy company Lightsource.

Nick Boyle, CEO of Lightsource Renewable Energy, saying:

"There are some disadvantages in water; clearly the fact that we've got to get it out there. But by the same token there are some positives as well. One of the things about solar panels and indeed the wiring connecting solar panels is that they work optimally at cooler temperatures. So actually there's an advantage of having these floating on water because the water actually has a positive effect on the actual production that the system actually generates."

The farm will generate about 5.8 million kilowatt hours of power in its first year.

While that's enough to power 1,800 homes, the energy harvested here will be used by this water treatment works.

It's part of Thames Water's aim to self-generate a third of its own energy by 2020.