Last year Bloomberg reported that the price of energy produced from wind and solar had fallen below the cost of energy produced from coal.
This was found to be true in Britain, France and Germany. It means that renewable energy can now compete with fossil fuels on price, without requiring government subsidies.
However, renewable energy is only cheap when it is being produced. When the sun isn’t shining and the wind isn’t blowing, we remain dependent on fossil fuels and nuclear power. It is possible to store energy produced from renewable sources but the current options are limited. A huge increase in grid-level energy storage is likely to be required as electricity is fully transitioned to renewable sources such as wind and solar.
There are a few established technologies for grid-level energy storage. The oldest is pumped-storage hydroelectricity in which energy is stored by pumping water up to an elevated reservoir and then allowed to flow back down through a turbine to generate electricity when required. More recently, grid-scale battery banks are starting to be installed. In their current form, neither of these technologies can be deployed at the scale and rapidity needed to reduce greenhouse gas emissions to safe levels.
An innovative pumped-storage hydroelectricity technology uses a concrete sphere located on the seabed as the lower reservoir. No upper reservoir or transmission pipe is required since the surrounding seawater provides the necessary water pressure. This has significant potential to provide near-term highly scaleable grid-level energy storage, integrated with other offshore power facilities.
Conventional hydro
The most economical way of storing really large amounts of energy is pumped-storage hydroelectricity (PSH). This stores surplus electricity as potential energy, typically by pumping water from a low-lying reservoir up to another reservoir located much higher up in a mountainous region. When electricity is needed, the water is allowed to flow back down to the lower reservoir, passing through a turbine that generates electricity. Round-trip energy efficiency is typically 70 to 80%. Total global installations of PSH amount to 127GW, over 99% of the world’s bulk-storage capacity.
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