Over the last 10 years, the price of wind and solar has reduced quicker than anyone anticipated. Consequently, the world is installing these renewables at breakneck speed to halt global warming.

However, there is a problem. Wind and solar only produce energy when the wind is blowing and the sun is beaming. To keep supply and demand matched, the world currently spends over $1T on fossil peaker plants that burn dirty oil, gas and coal to produce energy when renewables do not.

The solution to this is vast energy storage (of 4-10 hour discharge duration). For a 100% renewable grid, 70% of all power must be stored.

All energy storage technologies can be assessed on their Levelized Cost Of Storage (LCOS); this is the price needed to sell energy at to cover all costs of the project (finance, construction, maintenance etc). The following details each technology along with its LCOS for a 6h discharge duration:

**Battery energy storage:**

?Dominated by lithium-ion; used in most electric cars, laptops, and phones.

?Requires expensive processes and rare earth elements (lithium, cobalt, nickel) which are getting more expensive as demand rises.

?High efficiency

?LCOS = £223 /MWh

**Flywheels:**

?An electric motor takes electricity and stores it by rotating a metal or carbon fibre disk (called a rotor). To discharge the electricity, the motor is run in reverse, slowing the rotor.

?Expensive materials (high grade steel and carbon fibre) are needed to survive the forces from the very fast rotation required to store sufficient energy

?Highest efficiency, cheapest cost to extract the energy (power)

?LCOS = £479 / MWh

**Pumped-Hydro:**

?Similar to hydroelectric. Energy is stored by pumping water from the lower reservoir to the upper reservoir. Energy is discharged by doing the opposite.

?Requires very exact geography, many of the cheap sites have been used

?LCOS = £210 / MWh (highly location dependant)

**Hydrogen:**

?Stores energy by converting water to hydrogen. Energy is discharged by converting hydrogen back to water.

?Very expensive to extract power, very inefficient

?LCOS = £370 /MWh

Gas peaker plants have a Levelized cost of £90 /MWh, almost 3 times less than energy storage. Hence to achieve NetZero, with current technology, the cost of energy would more than double. To quote the largest private investor in energy storage (Bill Gates): "we need an energy storage miracle".