In my energy numeracy primer I have suggested we think of power stations as factories for electricity. To illustrate, we can compare them to a popcorn factory: corn gets delivered, workers run the machines, popcorn comes out and is sold for a price which is affordable yet still high enough to cover the cost of corn, wages, operation/maintenance, debt, regulatory compliance, and so on. A thermal power station takes in fuel – coal, gas, uranium, etc – and makes voltage and current from high quality heat by spinning magnets really fast. For solar and wind power the fuel is of course free (nature delivers it) but it’s best to put these power stations/factories out where it’s sunniest and windiest.
The analogy is just as valid for energy storage, except the fuel is the same as the product. Electricity is transformed into gravitational or chemical potential energy, then changed back again. At the scale of a regional electricity grid – an industrial scale – the economics of a factory still roughly apply.
Here is a “microgrid scale” battery.
It is part of the massive US$179 million Pacific Northwest Smart Grid Demonstration Project. Racks of lithium ion cells are housed within an 8,000 square foot (approximately 740 m²) warehouse, and can supply 5 megawatts of power for one half of an hour. The facility cost US$23 million to install. The results were recently compiled, with impressive success of the networked supply control systems.
So, when proponents of avoiding the consideration of nuclear energy invoke the promise of sufficient storage to replace conventional fossil fuel “backup” for renewable wind and solar, is this what they specifically have in mind?
Well, the sort of nuclear energy technology we have in mind, when built, can generate considerably more than 5 MW for half an hour. The 622 MW PRISM power block will supply 311 megawatt hours (622 x 0.5) in that time. The battery facility, 5 x 0.5 = 2.5 MWh. To match this 1/48 of a day nuclear output, the battery must be expanded by 124 times. Hopefully, the economies of scale might help to reduce the price tag below $4 billion (Australian dollars at current exchange rates), although the useful lifetime of these lithium ion cells will be very short on grid timescales. It would also be pretty big (124 x 740 m²).
But how expensive is that? Australia’s most recent proposed grid-scale storage project, the $282 million Genex Kidston pumped hydro facility west of Cairns will produce 330 MW for 5 hours on a full reservoir, i.e. 165 MWh in a half hour. A tenth of this capacity would equal $28.2 million – so it is clear why pumped hydro storage is universally recognised to be the cheapest form of storage! And just to be clear, Kidston is not even intended for storing intermittent renewable energy (despite some heavily insinuating it may be so).
The most up-to-date estimate for the first PRISM power block puts it around $8.3 billion. With a physical footprint comparable to a conventional nuclear plant and a sixty year design life (with years between outages, not 5 hours, or half an hour), there is little need to further labour the point. Storage technologies are cool, and have a part to play in our energy system, but invoking them to dismiss modern nuclear energy has to be the oversell of the decade. If we’re not replacing fossil fuels in our energy mix at the scale of PRISM, we’re not really decarbonising.