I was surprised to learn that 99% of global electricity storage is “pumped hydro” What’s that?

When there is spare power you pump water uphill to the “top pond” To retrieve the stored power the water turns turbines as it flows back down. The picture below sums it up.


Clearly you do not do this at home – it is only feasible for “grid level” storage but it would turn an “intermittent” (sun goes in, night falls) solar farm into a base load generator.

Is it feasible around here?

Well it turns out that it is. To make it worthwhile you need a top pond at least 100 meters above the bottom pond – and within a kilometre or so. Both these requirements can be met at Cairn Curran. All that is needed is an investor…

Keep your eyes on lithium ion batteries though. The recent Tesla announcement brings the cost of storing power down dramatically to around $400 per KwH.

This is the cost of installing the equipment to store a “chunk” of electricity that you probably pay 30 cents for. Pumped hydro (PHES Pumped Hydro Energy Storage) costs around $150. That price will stay put but the battery price will fall.

Factor in the scale though. Today lithium ion batteries store a small fraction – say 1% – of the 1% of storage that is not PHES so there is a very long way to go. The Tesla “giga factory” will double global lithium ion production but these are still fleas on an elephant’s back.