At about £200 per kWh of storage, batteries aren’t cheap. The cost of the electricity to fill it would be about 30 pence – or 600 times less than the battery (and good luck finding a battery that cheap in the shops!)
If I want to make a profit by buying cheap (5p per kWh) and selling expensive (30p) making 25p each time I fill and empty the battery. This needs 800 cycles to break even.
This is beyond the design life of some battery technologies, but some can cycle 3,000 times or more.
In 3,000 cycles I have £550 profit – not bad, but my 3,000 cycles have taken 3,000 days (electricity is only cheap at night) which is 8 years – although I broke even just after 2 years of running.
At the grid scale there is a further consideration. If we have an electricity system with a lot of renewables, then well-placed batteries can allow the solar and wind to continue to generate when there is congestion on the grid, which could mean cheaper electricity for us all. How we pay for this is one of the harder questions.
We are going to need a lot of batteries, but we also need to be realistic about the costs and the scale of this challenge:
As I write the UK is producing 15GW of wind power, to store this for one day will need about 360 GWh of batteries at a cost of £72bn. This would us 10 years of the production capacity of one Telsa Gigafactory. That’s also a lot of lithium, and we must think about what we do with them when they’re worn out.
Demand is growing exponentially, we want batteries in our cars, in our homes, and we want a renewables-based electricity grid, and this will need batteries. This isn’t going to get any easier or any cheaper.
As with all choices in the energy transition there should not be technology A vs technology B, we need all of them and at scale. So, time to get building those Gigafactories, investing in research, building a smarter grid, or let China lead (again).
