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. Quokka, Germany has established that it needs no new fossil generating capacity once those that were already planned or being built at the time of Fukishima are completed.

  2. BilB :
    It is a short term problem, Quokka, while industry, community, and the market adapts. Your primary assumption in your comment is that the situation is insoluble and therefore permanent. False.

    Building new fossil fired capacity is not a short term problem. It’s going to be difficult to get rid of before at least the capital is returned. That’s the way it is.

    The problem of storage is a long term problem that has existed ever since there were electricity grids. Many engineers and grid operators over the years must surely have wished for storage as a mechanism to meet peak demand and/or reduce the need for reserve capacity. But still hydro is the only viable option aside from niche applications.

    So why isn’t it here? Because it’s hard to do economically. And it’s hard because it needs lots of materials and lots of materials cost lots of money with the possible exception of water. Doesn’t matter if it’s chemical energy or gravitational potential energy or kinetic energy – it needs lots of stuff to implement. This is not a consequence of lack of human ingenuity. Neither is it a consequence of lack of industry, community or market adaptation.

    Perhaps there will be a storage “solution”, but until there is at least one major grid where it is being implemented at scale the working assumption remains that intermittent renewables will continue to be backed by fossil fuels with no time line as to when that situation is going to change. Until such time it’s all just Powerpoint engineering and promises that the gas industry is perfectly happy to go along with.

    Meanwhile emissions continue to rise with no end in sight.

  3. There is another way to back intermittent renewables – biogas. This may be quite sensible and reasonable if it is produced from waste, but in Germany most is produced from corn and it is a bit of an environmental horror show:

    The significance in German “green” energy is shown here:

    Just about anything is acceptable, but don’t mention the “n” word.

  4. Storage is a problem in your mind because you continue to analyse energy production and consumption from a BAU perspective, while considering only those renewable solutions which fit the formula of doom version to which you subscribe.

    The exciting thing in our future is that the escalating energy costs are fueling the cauldron of creativity. Two business maxims to which I subscribe are

    Nobody has a franchise on good ideas

    Greed breeds competition

    Both of these forces are at play in our energy supply world today. For the every day user grid electricity has been an economy stabalising influence. But given the opportunity provided by the announcement of Rudd’s CPRS for quick profits the grid energy providers eagerly hiked electricity prices then used that money to engage in a competition buyup war.

    The permanent consequence of that action was the breaking of the “monopoly for low cost” contract that the industry held with the public for many decades. The energy consumer now has both the freedom to explore other energy options and the incentive to do so. Consecutively there is a tsunami of technological creativity sweeping the globe with very real offerings for ever aspect of energy production and consumption.

    there is no point in you and I slugging it out over what might or should happen (according to us), I suggest sitting back and enjoying the show. The one thing that I am certain of and that is that the outcome will exhibit unprecedented variety.

    The one thing that you need to come to terms with is, who will buy energy from the grid when they can get it for free from their rooftop? And a question that you need to answer: how will the economy react to petrol hitting a sustained $2 per litre, and then some short time later $3 per litre?

  5. BilB :
    Storage is a problem in your mind because you continue to analyse energy production and consumption from a BAU perspective

    All mind games and no physical reality…. or not.

    I’ll tell you what business as usual is. It is estimated that in 2012 there will be over one trillion dollars in oil and gas capital expenditure world wide – all done creatively, of course. Almost certainly an all time record. Time to wake up to reality.

  6. @BilB

    Bilb, you hit the nail on the head. I was a peak oil, renewables-cynic, limits to growth doomster. (Sounds like a B grade movie title.) By dint of continuous arguments with people, mainly on this blog and often with Prof. J.Q., I have revised some (not all) of my views.

    I still accept peak oil as having arrived and even accept peak coal and peak uranium as imminent. I still accept the ultimate irrefutability of the limits to growth argument. I still foresee a lot of problems with climate change, sea level rise, overpopulation, soil depletion, fresh water scarcity, species extinctions etc.

    However, I have been convinced to change my views on the viability of renewable energy. I don’t think it’s the perfect fix but it’s the only fix. I don’t think it will supply as much EROEI as high quality, easy to access fossil fuels. I do think that it will need to be combined with other measures like much better energy efficiency, greater elimination of energy waste and a move from private to public transport.

    So whilst I do still see great problems ahead I am not now a total doomster. Renewable energy on a large scale does provide considerable hope and indeed our ONLY hope long term. Those opposing renewable energy without properly investigating the latest empirically proven renewables advances and without proposing any alternative to exhaustible (and climate wrecking) fossil fuels and exhaustible and dangerous fission fuels, are white-anting all positive efforts and making a catastrophic civilizational collapse considerably more likely.

    It all very well for doomsters and fatalists to point out that fossil use currently continues in pedal-to-the-metal fashion (like I used to). This is true but not useful. It entrenches a fatalistic “the game is already over” mentality. The only useful thing to do politically is debate and pressure and keep pushing for the soonest possible switch to renewables and away from fossil fuels.

    All the concerning and very obvious stuff (sea level rise, high average temperatures, loss of arctic sea ice, high incidence extreme weather events, ocean acidification, tropical fish – what’s left of them – changing their range to formerly cool temperate seas) is happening right now. It is no longer in the future. This will soon be accompanied by food shortages in some countries, crippling petrol prices for people with cars over 2000 cc capacity or so, crippling power bills for people without home solar power etc. etc. This will cause, must cause, a sea change in politics and finally some real action on these critical issues. It can’t be far away now.

  7. The perfect metaphor for the Business as Usual approach which ignores real physical forces.

  8. I would have prefered for CO2 emissions to be addressed in a directed manner using a levy on electricity to fund renewable energy infrastructure, but that got howled down as “slush fundism”. So we have the market approach which gives us an electricity price free for all which costs many times more for the consumer and offering absolutely no certainty emissions reductions.

    Change will be slow as and be driven by oil prices more than emissions based Carbon Prices. But that is what we have got to contend with. The pace of change will be largely proportional to the gradient of the advantage, but the direction of change is another matter altogether. As it is shaping up the greatest rate of change is likely to come from distributed power generation which engages distributed investment. Of course for this to work optimally the products have to be available, affordable, and offer economic or functional advantage. So to demonise storage as an impossible mission because it hasn’t happened yet is to ignore the shortcomings of the market economic engine.

  9. Those anticipating peak oil to save our climate bacon may be disappointed. Leonado Maugeri in his paper “Oil: The Next Revolution” (free access) argues convincingly that there is a revolution in oil production capacity underway as exemplified by the unprecedented current capital expenditure in oil and gas. He puts a figure of $70 per barrel as necessary to maintain that level of investment. The scenario he considers most likely is price volatility up until 2015, stabilizing thereafter as the new capacity comes on-line.

    When George Monbiot had the temerity to report on this in the Guardian, he was just about screamed at by some “greens” for being a heretic.

    If peak oil turns out to be a house of cards, and there is enough to cook us all, then what? That there are limits is obvious, but exactly where they lie is much less obvious.

  10. Peak oil, Quokka is not going to save anyones bacon. The harsh reality is that global oil demand continues to grow while existing production has plateaued, major fields mature rapidly towards exhaustion and new finds are ever smaller and more difficult to exploit. Meanwhile the global population continues to rise and Global Warming driven Climate Change takes an ever higher toll on property around the world.

    Addressing the causes of Climate Change and/or adapting to Climate Change require the continuity of supply of affordable oil to fuel the infrastructure transition. I argue that there may very well not be enough oil in the affordability window to perform the transition to an all electric world.

    Oil prices “stabilizing” after 2015 is highly unlikely, and there is plenty of informed comment to support that view. That can only be the view of someone commenting on America’s internal supply and demand position. I see two highly populous countries with fledgling auto makers keen to have a go themselves at building the Indian and the Chinese Dream.

  11. @BilB

    Oil prices “stabilizing” after 2015 is highly unlikely, and there is plenty of informed comment to support that view. That can only be the view of someone commenting on America’s internal supply and demand position.

    It isn’t.

  12. Folks, viable storage has already happened. It’s up and running, working and viable.

    “The Andasol solar power station is Europe’s first commercial parabolic trough solar thermal power plant, located near Guadix in Andalusia, Spain. … The Andasol plant uses tanks of molten salt to store solar energy so that it can continue generating electricity even when the sun isn’t shining.” – Wikipedia.

    Further quotes from Wikipedia;

    “Andasol 1 went online in March 2009. Because of the high altitude (1,100 m) and the semi-arid climate, the site has exceptionally high annual direct insolation of 2,200 kWh/m² per year. Each plant has a gross electricity output of 50 megawatts (MWe), producing around 180 gigawatt-hours (GW·h) per year (21 MW·yr per year). Each collector has a surface of 51 hectares (equal to 70 soccer fields); it occupies about 200 ha of land.”

    “Andasol has a thermal storage system which absorbs part of the heat produced in the solar field during the day. This heat is then stored in a molten salt mixture of 60% sodium nitrate and 40% potassium nitrate. A turbine produces electricity using this heat during the evening, or when the sky is overcast. This process almost doubles the number of operational hours at the solar thermal power plant per year. A full thermal reservoir holds 1,010 MW·h of heat, enough to run the turbine for about 7.5 hours at full-load, in case it rains or after sunset. The heat reservoirs each consist of two tanks measuring 14 m in height and 36 m in diameter and containing molten salt. Andasol 1 is able to supply environmentally friendly solar electricity for up to 200,000 people.” – Wikipedia

    I can find no reports of incidents or outages at Andasol 1 in 3 years of operation. This does not mean they have not occurred of course. I found the following recent report about Andasol 2 which I believe is still under construction or testing. I do not know the veracity of this report.

    “03.12 Spain 120312-08 Granada, Aldeire. Andasol 2. The explosion of a boiler for reasons still unknown occurred in the early hours and caused a fire in the solar thermal plant Andasol 2, …” – Weekly Incident Summary from;

    Many installations of proven, mature technologies (refineries, coal power stations etc.) have incidents all over the world all the time. The apparent Andosol 2 incident is not diagnostic in itself of inherent technology problems or limits with molten salt storage. The wording “explosion of a boiler” seems to indicate a steam boiler and not a molten salt storage tank.

  13. Quokka, even if engineers have long wished for better storage it’s not been a high R&D&D priority – they may have wished for it but then they went out and used a diesel generator.

    Even now, with strong cause to believe it could be a make or break technology for avoiding catastrophic climate change the budgets for energy storage development and deployment represent less than petty cash for big energy companies.

    Although it is beginning to get a modicum of serious attention the biggest part or our energy sector see continuing rise in emissions as an acceptable fall back position at best or at worst see that as the preferred outcome.

    I mentioned a British start up that is claiming storage costs for their pumped heat system of less than pumped hydro – it may prove to be a dud but they were convincing enough for the UK’s Energy Technologies Institute to not only help fund it’s £15.7 million pilot project , but to buy equity in the company. They claim under US$55 per kWhr and aiming for $8. (elsewhere I saw $38/MWhr but I think the M was meant to be K). It doesn’t sound like it’s rocket science either – hot and cold gravel with argon as the working fluid. Which sounds like something that really could be low cost.

  14. Quokka,

    After your endorsement of Maugeri I wondered what Robert Rapier’s take on the projections would be. My opinions are entirely guesswork based on serendipitous observation. Robert Rapier on the other hand is an oil industry consultant and long time commentator on energy matters. Here is his take on both Maugeri and Monbiot….

    Even the International Energy Agency are predicting a rise in the price of petrol by 2020 to around $3 per litre. Now along the way desperate governments might take extraordinary action to stabilise energy prices within their domains, but the trend is well in place.

    In my view only the most ideologically biased of politicians would ignore these dire warnings and take comfort in one report against the compendium of contrary assessment, which may account for Monbiot’s treatment. Given the trends, all of them, there is only one conclusion to be made, and that is, as Carbonsink declared over and over, our economic future has to be based on the electrification of industry and transport.

    I doubt that you disagree with this. Our differences are in the method of electrification.

  15. I appreciate your sober assessment, Ikonoclast.

    My vision of the near future is predominately electric powered by the GenIIPV system or similar efficiency solar solutions. But of course there will be a broad mix of energy solutions which will include cane ethanol from the Burdekin and Ord areas, Palm oil from Arnhemland, sewerage fed Algal oil from a number of locations, and even municipal and domestic level methane gas from local digesters. Complementing all of this is wind energy capacity and eventually storage solar thermal as Ken Fabian has described. Beyond that there will be a progression towards solar thermal direct to process applications such as hot oil powered rotational and injection moulding, for instance.

    Based on my life time observation of the world and its processes, and as an industrial designer, I believe that the market based transition to a predominately solar powered ….lets stick to Australia here…can take place within 60 years. This can be compressed into just 20 years with decisive leadership and community will, but we are nowhere near that position, …..obviously.

  16. @BilB
    Actually the Pumped Heat Energy Storage system I mentioned is electricity to electricity storage and isn’t tied to any particular source. I think the pilot plant is being incorporated into a standard substation. In Britain that may or may not near wind farms – unlikely there’d be much solar thermal though.

  17. quokka, there’s something that stood out in Maugeri’s report: shale oil drilling also produces trillions of cubic feet of natural gas. What do you do with that natural gas? You have to sell it. By selling it into a market already flooded with natural gas, you further reduce the cost of gas, and make gas the more attractive option to the middle-man and consumer. ie. potentially the more shale oil you drill (also expensive to transport and refine), the more demand for oil in the US will continue to decrease. As an aside, it’s also worth noting that by law US oil can’t be exported.

    He doesn’t offer a solution to this conundrum, but concedes it could severely affect the economics and medium-term viability of shale oil.

    You can see this confirmed here, btw:

    Where, if I’m reading correctly, by far the most new natural gas resources discovered have been from shale/tight oil drilling.

    It’s beyond me to know what all these factors really add up to, so just putting them forward for discussion and consideration, not to be argumentative.

  18. One of the concerning things it all adds up to IMO is more fossil fuel for the “Burn the Lot” lobby to recover and sell. Certainly, capitalists with interests in oil, gas and coal are funding the climate change debunking propaganda. They are also funding the “renewables will never work” propaganda. They pay for many scientific charlatans and shills to write on the net pretending to be ordinary concerned citizens.

    All this propaganda is very effective. When I bring up these topics in general conversation with family, friends and acquaintances, the majority say things like this. “Climate change? The science isn’t settled yet.” , “Wind and Solar will never work.” , “Wind is too intermittent and the sun doesn’t shine a night.” They think rebuttal of all the genuine science is this easy.

    It’s scary how propagandised and closed their minds are. And most of them are smart enough to know better.

  19. Ike, probably most common “c’mon, even if what they say is true, surely it’s not going to be as bad as they say…”

    I’m constantly bewildered by Monbiot’s ability to have an industry paper (Belfer Center? it’s named after an oil mogul, ffs) thrown in his lap, not question the thing at all, and start rabbiting on about “oh noes, we’re all definitely rooned now…how do i go home and explain to my kids how wrong we’ve been all been about peak oil theory all these years…”

    Well, actually nobody has been proved wrong about peak oil. Even according to Maugeri, from now on it needs at least a $70 floor price to remain profitable. And if it stays above $100 for any serious length of time? Also no good because 1) that stuffs up economic growth, and 2) there are too many other alternatives. Wait until Evs are 30% cheaper in 10 years.

    I also suspect Maugeri is at least 6 months out of date, and that his capex calculations are based on last year’s figures, not the >$1 trillion for 2012 quokka reported upthread. So you could possibly guess his $70 floor price should be more like $80…or am I way off on that?

    To my mind, it’s pretty clear (if nothing else is just yet) that oil has an ever shrinking window of profitability. And if at any time in the next 5-10 years growth in China slows dramatically, or there’s another major war or uprising in the Middle East or Africa, or America decides to get serious about tackling climate change/not trashing its environment, or the advent of dark silicon causes a tech stock crash, or there actually never is any significant economic recovery across large parts of the world etc…these are all other factors Maugeri concedes will make a mess of his predictions of ‘a new oil renaissance’.

  20. @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.

  21. 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).

  22. 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.

  23. @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!

  24. @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.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s