Without energy we would have no warm homes, no hot water for showers, and no electricity to keep food chilled, operate appliances or allow us to work at the computer. Up to now our economy has been driven – and our homes made comfortable – by oil, coal and gas. Slowly but surely, these natural resources are running out. If we want to continue to enjoy affordable power, heat and cooling in the future, we need to become more efficient in the way we use energy, get better at storing it reliably and try harder to develop renewable energy sources.