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Renewables such as wind and solar are becoming cheaper than fossil fuels in most parts of the world. But they need storage to provide a reliable, steady source of energy to power grids. That is where batteries fit in.
Lithium-ion batteries, used in mobile phones and Tesla electric cars, are currently the dominant storage technology. They can be placed anywhere and provide power to the grid very quickly. But cheaper, longer duration storage technologies, most of which are not yet cost effective, will also be required.
More than 97 per cent of the world's energy storage is currently done by pumping water up to a high reservoir and then releasing it, which drives the turbine to create electricity. The reservoir acts as a way of storing energy, but these systems may be limited by geography and increasing water scarcity.
Today, though, billions are being invested in other storage technologies. In …