Peak Oil is You

Donate Bitcoins ;-) or Paypal :-)

Page added on August 25, 2014

Bookmark and Share

The Catch-22 of Energy Storage

The Catch-22 of Energy Storage thumbnail

Pick up a research paper on battery technology, fuel cells, energy storage technologies or any of the advanced materials science used in these fields, and you will likely find somewhere in the introductory paragraphs a throwaway line about its application to the storage of renewable energy.  Energy storage makes sense for enabling a transition away from fossil fuels to more intermittent sources like wind and solar, and the storage problem presents a meaningful challenge for chemists and materials scientists… Or does it?

Guest Post by John Morgan. John is Chief Scientist at a Sydney startup developing smart grid and grid scale energy storage technologies.  He is Adjunct Professor in the School of Electrical and Computer Engineering at RMIT, holds a PhD in Physical Chemistry, and is an experienced industrial R&D leader.  You can follow John on twitter at @JohnDPMorganFirst published in Chemistry in Australia.

Several recent analyses of the inputs to our energy systems indicate that, against expectations, energy storage cannot solve the problem of intermittency of wind or solar power.  Not for reasons of technical performance, cost, or storage capacity, but for something more intractable: there is not enough surplus energy left over after construction of the generators and the storage system to power our present civilization.

The problem is analysed in an important paper by Weißbach et al.1 in terms of energy returned on energy invested, or EROEI – the ratio of the energy produced over the life of a power plant to the energy that was required to build it.  It takes energy to make a power plant – to manufacture its components, mine the fuel, and so on.  The power plant needs to make at least this much energy to break even.  A break-even powerplant has an EROEI of 1.  But such a plant would pointless, as there is no energy surplus to do the useful things we use energy for.

There is a minimum EROEI, greater than 1, that is required for an energy source to be able to run society.  An energy system must produce a surplus large enough to sustain things like food production, hospitals, and universities to train the engineers to build the plant, transport, construction, and all the elements of the civilization in which it is embedded.

For countries like the US and Germany, Weißbach et al. estimate this minimum viable EROEI to be about 7.  An energy source with lower EROEI cannot sustain a society at those levels of complexity, structured along similar lines.  If we are to transform our energy system, in particular to one without climate impacts, we need to pay close attention to the EROEI of the end result.

The EROEI values for various electrical power plants are summarized in the figure.  The fossil fuel power sources we’re most accustomed to have a high EROEI of about 30, well above the minimum requirement.  Wind power at 16, and concentrating solar power (CSP, or solar thermal power) at 19, are lower, but the energy surplus is still sufficient, in principle, to sustain a developed industrial society.  Biomass, and solar photovoltaic (at least in Germany), however, cannot.  With an EROEI of only 3.9 and 3.5 respectively, these power sources cannot support with their energy alone both their own fabrication and the societal services we use energy for in a first world country.

Energy Returned on Invested, from Weißbach et al.,1 with and without energy storage (buffering).  CCGT is closed-cycle gas turbine.  PWR is a Pressurized Water (conventional nuclear) Reactor.  Energy sources must exceed the “economic threshold”, of about 7, to yield the surplus energy required to support an OECD level society.

These EROEI values are for energy directly delivered (the “unbuffered” values in the figure).  But things change if we need to store energy.  If we were to store energy in, say, batteries, we must invest energy in mining the materials and manufacturing those batteries.  So a larger energy investment is required, and the EROEI consequently drops.

Weißbach et al. calculated the EROEIs assuming pumped hydroelectric energy storage.  This is the least energy intensive storage technology.  The energy input is mostly earthmoving and construction.  It’s a conservative basis for the calculation; chemical storage systems requiring large quantities of refined specialty materials would be much more energy intensive.  Carbajales-Dale et al.2 cite data asserting batteries are about ten times more energy intensive than pumped hydro storage.

Adding storage greatly reduces the EROEI (the “buffered” values in the figure).  Wind “firmed” with storage, with an EROEI of 3.9, joins solar PV and biomass as an unviable energy source.  CSP becomes marginal (EROEI ~9) with pumped storage, so is probably not viable with molten salt thermal storage.  The EROEI of solar PV with pumped hydro storage drops to 1.6, barely above breakeven, and with battery storage is likely in energy deficit.

This is a rather unsettling conclusion if we are looking to renewable energy for a transition to a low carbon energy system: we cannot use energy storage to overcome the variability of solar and wind power.

In particular, we can’t use batteries or chemical energy storage systems, as they would lead to much worse figures than those presented by Weißbach et al.  Hydroelectricity is the only renewable power source that is unambiguously viable.  However, hydroelectric capacity is not readily scaled up as it is restricted by suitable geography, a constraint that also applies to pumped hydro storage.

This particular study does not stand alone.  Closer to home, Springer have just published a monograph, Energy in Australia,3 which contains an extended discussion of energy systems with a particular focus on EROEI analysis, and draws similar conclusions to Weißbach.  Another study by a group at Stanford2 is more optimistic, ruling out storage for most forms of solar, but suggesting it is viable for wind.  However, this viability is judged only on achieving an energy surplus (EROEI>1), not sustaining society (EROEI~7), and excludes the round trip energy losses in storage, finite cycle life, and the energetic cost of replacement of storage.  Were these included, wind would certainly fall below the sustainability threshold.

It’s important to understand the nature of this EROEI limit.  This is not a question of inadequate storage capacity – we can’t just buy or make more storage to make it work.  It’s not a question of energy losses during charge and discharge, or the number of cycles a battery can deliver.  We can’t look to new materials or technological advances, because the limits at the leading edge are those of earthmoving and civil engineering.  The problem can’t be addressed through market support mechanisms, carbon pricing, or cost reductions.  This is a fundamental energetic limit that will likely only shift if we find less materially intensive methods for dam construction.

This is not to say wind and solar have no role to play.  They can expand within a fossil fuel system, reducing overall emissions.  But without storage the amount we can integrate in the grid is greatly limited by the stochastically variable output.  We could, perhaps, build out a generation of solar and wind and storage at high penetration.  But we would be doing so on an endowment of fossil fuel net energy, which is not sustainable.  Without storage, we could smooth out variability by building redundant generator capacity over large distances.  But the additional infrastructure also forces the EROEI down to unviable levels.  The best way to think about wind and solar is that they can reduce the emissions of fossil fuels, but they cannot eliminate them.  They offer mitigation, but not replacement.

Nor is this to say there is no value in energy storage.  Battery systems in electric vehicles clearly offer potential to reduce dependency on, and emissions from, oil (provided the energy is sourced from clean power).  Rooftop solar power combined with four hours of battery storage can usefully timeshift peak electricity demand,3 reducing the need for peaking power plants and grid expansion.  And battery technology advances make possible many of our recently indispensable consumer electronics.  But what storage can’t do is enable significant replacement of fossil fuels by renewable energy.

If we want to cut emissions and replace fossil fuels, it can be done, and the solution is to be found in the upper right of the figure.  France and Ontario, two modern, advanced societies, have all but eliminated fossil fuels from their electricity grids, which they have built from the high EROEI sources of hydroelectricity and nuclear power.  Ontario in particular recently burnt its last tonne of coal, and each jurisdiction uses just a few percent of gas fired power.  This is a proven path to a decarbonized electricity grid.

But the idea that advances in energy storage will enable renewable energy is a chimera – the Catch-22 is that in overcoming intermittency by adding storage, the net energy is reduced below the level required to sustain our present civilization.

BNC Postscript

When this article was published in CiA some readers had difficulty with the idea of a minimum societal EROI.  Why can’t we make do with any positive energy surplus, if we just build more plant?  Hall4 breaks it down with the example of oil:

Think of a society dependent upon one resource: its domestic oil. If the EROI for this oil was 1.1:1 then one could pump the oil out of the ground and look at it. If it were 1.2:1 you could also refine it and look at it, 1.3:1 also distribute it to where you want to use it but all you could do is look at it. Hall et al. 2008 examined the EROI required to actually run a truck and found that if the energy included was enough to build and maintain the truck and the roads and bridges required to use it, one would need at least a 3:1 EROI at the wellhead.

Now if you wanted to put something in the truck, say some grain, and deliver it, that would require an EROI of, say, 5:1 to grow the grain. If you wanted to include depreciation on the oil field worker, the refinery worker, the truck driver and the farmer you would need an EROI of say 7 or 8:1 to support their families. If the children were to be educated you would need perhaps 9 or 10:1, have health care 12:1, have arts in their life maybe 14:1, and so on. Obviously to have a modern civilization one needs not simply surplus energy but lots of it, and that requires either a high EROI or a massive source of moderate EROI fuels.

The point is illustrated in the EROI pyramid.4 (The blue values are published values: the yellow values are increasingly speculative.)

Finally, if you are interested in pumped hydro storage, a previous Brave New Climate article by Peter Lang covers the topic in detail, and the comment stream is an amazing resource on the operational characteristics and limits of this means of energy storage.

brave new climate

14 Comments on "The Catch-22 of Energy Storage"

  1. Pops on Mon, 25th Aug 2014 3:08 pm 

    A current discussion on this very topic in the forums:

  2. shortonoil on Mon, 25th Aug 2014 8:03 pm 

    There are several things that are blatantly wrong in this article. Hall did not invent the term EROI; he was just the first to use it for energy produced from hydrocarbons. The EROI from nuclear is not 75:1. If it was nuclear would have long ago replaced fossil fuels for the production of electricity. It is closer to 8:1 (conventional crude is now 9.1:1). If the decommissioning of these plants is taken into consideration it is probably less than 2:1, and they are likely energy sinks.

    The main error in the article is that the energy storage problem is not insolvable. It has been worked on intensively for the last 50 years. The main obstacle appears to now be application. Many politically powerful groups are now standing in its way. You can read about it here:

    An efficient, low cost energy storage system would dislocate the most powerful group in the world. The centrally controlled energy sector.

  3. Tom S on Mon, 25th Aug 2014 8:23 pm 

    This article is repeating all of the ERoEI errors which have been floating around for decades. You can find a refutation of these ideas here:

    -Tom S

  4. ulenspiegel on Tue, 26th Aug 2014 2:44 am 

    To take a wind turbine (E-66) that is not longer produced as “reference” is a poor performance and let me doubt that the author was actually interested in a serious discussion.

    New turbines have a EROEI of >40 in Germany with not so good wind resources. From this number it claer that the same turbine in the midwest USA would beat a NPP.

  5. Makati1 on Tue, 26th Aug 2014 7:32 am 

    Germany gets a very small percentage of their electric from Solar and wind. They brag, but it is minuscule.

    Tom S. your article is pure BS! Author: “I study economics. I thought my knowledge of economics might be useful in analyzing doomerism and energy decline arguments.”

    An economist talking about energy is like the oxymoron ‘military intelligence’. He is selling something and it is not renewable energy. The graph in the article is close to the truth except, as shortonoil said, nuclear is a loss.

    Quite possibly, the others are all a loss also if they were properly researched. For instance, how much energy goes into making a simple D cell battery? I would bet a fifth of Johnny Walker Red that it is also a net loss.

    What do economists know anyway? They are nothing but charlatan fortune tellers that look in the rear view mirror for their numbers. I’ve never seen a correct prediction more than two days from the event in the last 20 years. The weathermen are more correct than they are. Maybe they are all engineer wannabees that couldn’t do math?

  6. Makati1 on Tue, 26th Aug 2014 7:32 am 

    Oops! …Germany gets a very small percentage of their energy from Solar and wind. They brag, but it is minuscule…

  7. Solarity on Tue, 26th Aug 2014 12:19 pm 

    The article clearly defines its EROI criteria: ‘the ratio of the [net] energy produced over the life of a power plant [relative] to the energy that was required to build it.’

    The nuclear EROI figure of 75:1 is very realistic, and is probably understated for some applications. A submarine is a classic and appropriate case in point: it requires a buffer between power generation and usage. A nuclear sub reactor produces more than 10,000 times the energy used to build it.

    It is interesting how some people selectively recognize that politics stands in the way of advanced technology.

  8. shortonoil on Tue, 26th Aug 2014 12:25 pm 

    “I would bet a fifth of Johnny Walker Red that it is also a net loss.”

    Economists don’t use Johny Walker Red for energy, they use it to build confidence. To them that is a much more important aspect of economics than energy. Chances are you are not going to get any takers on that bet from an economist.

    A simple way to calculate the energy needed to produce a product is by using Graph# 12 at our site. The graph gives BTU/$ for respective years.

    Find the BTU/$ projection for any year. Example: 2012 gives 6380 BTU/$. If a D cell battery cost $3.00 it took 19,140 BTU ($3.00 * 6380 BTU/$) to produce it, transport it, and stock on it on the self at your store. 1 Watt (1 amp*1Volt) = 3.413 BTU/hour. We are talking about a major loser here.

    The graph is using the “average” cost of energy for any particular year. So, the larger the dollar cost of an item the more accurate it becomes. For a $20 billion nuclear plant, it is most likely right on. Smaller $ items are likely to be less accurate, but it allows a quick way to sort out much of the BS shoveled out by the industry.

    The graph equation is:
    BTU/$ = 3.0*10^13* year^-4.72

    where year zero is 1900: so the year 2000 would be 100, 1960 would be 60, 2010 would be 110.

  9. Tom S on Tue, 26th Aug 2014 2:36 pm 

    Makati, you haven’t produced a single relevant objection to anything in the blog post. Your whole response was ad hominem.

    Focus on content! Don’t worry excessively about who the author is.

    -Tom S

  10. marmico on Tue, 26th Aug 2014 2:49 pm 

    The graph is using the “average” cost of energy for any particular year.

    Energy intensity is declining. Energy Consumption per Real Dollar of GDP. Since 1950, U.S. petroleum and natural gas btu consumption has increased 3-fold and GDP has increased 7-fold. Since 2000, U.S. total btu consumption is flattish but GDP has increased 25%.

  11. Tom S on Tue, 26th Aug 2014 3:24 pm 


    “Germany gets a very small percentage of their energy from Solar and wind. They brag, but it is minuscule…”

    I just quickly went to wikipedia ( and it claims that renewables made up over 30% of German electricity production in the first half of 2014. Also, renewables supplied 11% of all energy in 2011, and (just extrapolating here) about 15% so far in 2014. Almost all of that comes from wind, solar, and biomass. One of the sources in a German gov’t agency.

    It appears that solar and wind by themselves produce about 8% of primary energy in Germany at present. If you include biomass, it’s about 12%.

    Just counting solar, wind, and biomass, Germany went from about 6% of all energy from those renewable sources, to about 12%, in 5 years.

    Who knows how long that can be sustained. So far, they’re doing ok.

    -Tom S

  12. Tom S on Tue, 26th Aug 2014 4:47 pm 


    “A simple way to calculate the energy needed to produce a product is by using Graph# 12 at our site.”

    I don’t think that’s going to be very accurate. There’s only a loose correlation between dollars and energy used to produce something. Increasingly, a large fraction of the GDP consists of services like medical care, financial services, software, and intellectual property, which use little energy but cost a lot of money.

    “For a $20 billion nuclear plant, it is most likely right on.”

    That doesn’t follow. It would only be a reasonable estimate if building nuclear plants were a large fraction of the entire GDP. Even then, it could be off by a lot.

    -Tom S

  13. Tom S on Tue, 26th Aug 2014 4:50 pm 


    “For instance, how much energy goes into making a simple D cell battery? I would bet a fifth of Johnny Walker Red that it is also a net loss.”

    Every battery is a net loss.

    -Tom S

  14. Robert on Tue, 26th Aug 2014 5:58 pm 

    To take this article to heart is to believe in the numbers provided. Who made these numbers up and how accurate are they to real world application. Real world economics determine what can and cant be done. If the cost of a solar cell is lower cost than coal than its possible. Because digging it up, driving those materials, and making the factory are all included in the pricing. We have a real world model for determining viability. Some economic theory of viability is irrelevant because in real world economics its proven wrong. I simply refuse to accept the premise that its negative energy efficient and somehow economically viable at the same time. Thats what money was designed to prevent from happening.

Leave a Reply

Your email address will not be published. Required fields are marked *