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…