India unveiled the world's biggest solar farm earlier this year and has quadrupled its solar capacity in the last three years, bringing electricity to millions of off-grid households. But what are the innovations that could see solar replacing fossil fuels completely? Rameshwarlal Choudhary, a 45-year old farmer, and his wife Dakha, 40, live with their two children in a small shack near the village of Solawata in India's Rajasthan. Their home has thatched walls, a tin roof, and one side is completely open to the elements. Until six months ago, they were part of the 44% of India's rural households who lack electricity.

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