Renewable energy storage, illustration. Renewable energy sources such as wind and solar are only able to generate electricity at certain times. Therefore, to ensure a continuous flow of power to the grid any excess power generated needs to be stored. One proposed solution is to store it as liquid air. Freezing air to the point that it becomes liquid, leads to a 700 times reduction in volume. When electricity is needed the liquid air is pumped into an evaporator where its expansion drives a turbine, generating electricity that can be distributed via high voltage power lines.