The Sun, our star, produces its prodigious energy by a process of nuclear fusion at its core. We are unable to mimic that trick here on Earth: our nuclear reactors work by splitting atoms, not fusing them, and generate a lot of toxic waste. With a free standing solar mini grid in Kenya and the problems of the old grid system in California, Dava Sobel explores the progress being made in tapping the Sun for its inexhaustible supply of free, clean energy.

Audio for this programme was updated on 8th September 2020.

(Photo: Solar panels on the Kitonyoni grid are cleaned. Credit: BBC)