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.

130 thoughts on “How to solve the solar storage problem

  1. @Nick

    There is a current report that 2012 oil and gas capex will be over $1 trillion. Google “Global Oil & Gas Capital Expenditure Breaks $1 Trillion Barrier”. (no link because of moderation delays). If anything Maugeri may be understating the situation.

    Brent crude futures are currently trading at something like $113 and the world hasn’t imploded. There does not seem to be any inherent reason why an average price of $80 could not be sustained over a number of years driving a new wave of capital expenditure.

    Of course any number of things could put the stoppers on Maugeri’s scenario or slow it up and however it plays out it’s unlikely to be completely smooth sailing – but these things never were.

    Aside from biofuels where the cure may be little better than the disease, there seems hardly any policy movement on “peak oil”. There may be a reason for that.

  2. Regarding the storage problem…

    Couldn’t we just pump water uphill in the snowy hydro area during surplus periods, then during high demand re-capture the potential energy by letting it back down the turbines?

    It may not be efficient, but it is a load leveler with vast capacity and already built (except for the upward pumps).

  3. Lindsay, my understanding is that Snowy Hydro already does some of that and will make the most of it’s ability to sell that service but it’s capacity for doing so is limited and their decisions will be prioritised to most efficient use of high pondage for their own energy production purposes. And during prolonged drought they will be struggling to remain fully operational.

  4. @Ken Fabian
    Yes, they pump back in cheaper off peak times to take advantage of peak periods when they can sell energy at a higher rate. Presumably the power required to pump water back is from coal fired sources making the whole exercise somewhat pointless. Energy companies are principally to make money using energy!

  5. @Lindsay

    Water poses a range of challenges in this country – like not enough in the right places (near electricity use points) and the need for very large storages. This is fine opportunistically like at Fitzroy Falls NSW but large storages imply dams, groundwater intrusion, evapotranspiration losses, flooding areas etc. – which would generate as much flack as windmills I suspect as well as these undesirable secondary effects.

    There are alternatives also. Most people are familiar with the fact that solar thermal systems often store heat in brine which can be used according to demand.

    An alternative is compressed air which they are exploring in Germany. There is good discussion of these issues here: Or perhaps small gas turbines running syngas during peak periods makes more sense.

    And finally there is conservation approach – a serious premium tax on peak uses such as air conditioning which are not essentials in 80% of instances (aged people, hospitals obvious need special consideration).

    The nice thing about it all is you dont necessarily need these giant multi GW establishments.

    In conclusion storage of renewable energy is not really a challenge – its really just about the economics and incorporating all the externalities into the costs and balancing the demand – which coal and nuclear power seem historically arent great at either.


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