Renewable methods for (produce) electricity, such as wind turbines and solar panels, can only provide power on the days wind blows or the sun shines. Electric batteries (use) to store energy are expensive and can also be polluting. Finnish scientists came up with a simple solution that puts unwanted green electricity to work, heating 100 tons of sand to around 500℃. The sand stays hot for months; when energy (require), air can be pumped through it and heated up. The air in turn heats a system that supplies hot water to heat nearby houses.
