The idea of light coming on at the flick of a switch is not as ubiquitous as one might think. Many millions of people, including 600 million in sub-Saharan Africa alone, live in rural areas without access to the grid.
Even many urban areas lack consistently reliable grid supplies. For these
people, renewable power offers an increasingly popular and established route to homegrown, low-cost energy. However, renewables such as solar PV and onshore wind are inherently intermittent and cannot be relied upon for continuous power supplies.