Electricity is expensive to store in large quantities. The largest battery pack in North America has just opened this week at a cost of about $50m for 32 MWh of lithium-ion cells. That’s over $1,500 a kilowatt hour, several times the cost of batteries in electric cars. (I presume the reason for the high cost must be the sophisticated electronics necessary to tie the DC battery system to the local grid).
The new plant is sited at one of the substations serving the huge Tehachapi wind farms in Southern California. 600,000 individual batteries wired together in a 500 square metre warehouse are helping to stabilise the output of the five thousand turbines in this important wind province.
The UK’s largest storage battery is being built in Leighton Buzzard, north of London, and is due for completion by the end of 2014. This 10 MWh plant is costing about £20m, partly paid by Ofgem and partly by the local operator UK Power Networks. The cost is over twice the price per kilowatt hour of the Californian battery.
Adding the gigawatts/gigawatt hours of short term storage that we need is going to cost huge sums. Batteries will get cheaper, of course, particularly if Tesla continues to invest in enormous factories in the US. But even at $250 per kilowatt hour of storage capacity – one estimate of the likely cost of Tesla batteries within a few years – a gigawatt hour will require expenditure of $250m. That buys the capacity to store about a minutes worth of UK peak electricity need.
One alternative to lithium-ion batteries is an expansion of pumped hydro. Two water reservoirs at different heights are linked and reversible turbines are installed. When electricity is cheap, water is pumped uphill to the top reservoir. At times of high power demand the water flows back downhill, turning the turbines and producing electricity. The UK has had a large pumped hydro plant at Dinorwig in Snowdonia for thirty years.
A new company, Quarry Battery, has just raised another round of seed money to push its own Snowdonia project forward. £3m will enable the company to carry out engineering costings and other preparatory tasks for its scheme to turn two disused deep slate quarries into the upper and lower reservoirs of a pumped hydro plant. Read the rest of this entry »