Solar and wind investment pays off as Google reveals it will reach 100 percent renewable energy target in 2017
Search engine giant contributes $300m (£195m) to a fund to push solar panels onto residential roofs
Elon Musk's SolarCity buys panel maker and promises to slash the cost of solar power
IBM and others are working on a solar collector that can magnify the power of 2,000 suns for green energy
The SolarSinter project makes objects from sand and sunlight - and it will be on show in London in September.