How to solve the solar storage problem

Australians installed more domestic rooftop solar PV in 2011 than in any other country in the world. Despite sharp cuts in subsidies, that seems likely to continue, and raises the question of how this will effect patterns of electricity demand and in particular the capacity of the electricity system to meet peak demand. I just ran across an interesting infographic prepared by a consulting group called Exigency management which puts the question into sharper focus . Under current conditions, demand peaks around noon, remains high through the afternoon, then has another peak in the early evening, as people come home and turn on airconditioning or heating. Widespread takeup of home solar PV will increase supply at the noon peak and even more in the afternoon, but drop off as evening approaches. The result, in the absence of any other changes, will be a system with a demand trough in mid-afternoon followed by a much sharper evening peak.

Source: Exigency

(More graphics here)

What can be done about this? The first point to observe is that the demand projection is under current pricing rules. Any sensible system, faced with a demand pattern like this would set peak prices to cover the actual demand peak, not the one that prevailed under a 20th century coal-based system. But, price incentives alone aren’t satisfactory in the absence of some way of storing energy. There’s been lots of discussion of more-or-less exotic solutions, but there’s a much simpler answer.

The energy storage solution

Because the evening peak is only an hour or two after the afternoon trough, the simplest response to a big price differential is to set a timer to turn on heating and cooling systems a couple of hours before you get home. The house itself then acts as the storage system. Of course, there are much more sophisticated management systems available, and already routinely installed with central AC systems, but most people don’t use them because there is very little incentive to do so.

This might not be a complete solution (particularly for winter) but it illustrates the central point I’ve been making. We already have most of the technology we need to greatly reduce CO2 emissions, and rapid progress in both PV and wind will soon give us most of the rest. The big problem is institutions and attitudes hanging over from the era of cheap fossil fuels.

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