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The Catch-22 of Energy Storage

Barry Brook's picture
University of Tasmania
  • Member since 2018
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  • Aug 25, 2014

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.

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.


  1. Weißbach et al., Energy 52 (2013) 210. Preprint available here.
  2. Carbajales-Dale et al., Energy Environ. Sci. DOI: 10.1039/c3ee42125b
  3. Graham Palmer, Energy in Australia: Peak Oil, Solar Power, and Asia’s Economic Growth; Springer 2014.
  4. Pedro Prieto and Charles Hall, Spain’s Photovoltaic Revolution, Springer 2013.
Barry Brook's picture
Thank Barry for the Post!
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Nathan Wilson's picture
Nathan Wilson on Aug 30, 2014

See reply down thread.

Nathan Wilson's picture
Nathan Wilson on Aug 30, 2014

Sure, the Earth is full of hot dry rock.  But we really only know how to harvest geothermal energy from certain types of formations: hydro thermal, or porous formations with with a non-porous seal around it (how common is that?).

Nathan Wilson's picture
Nathan Wilson on Aug 30, 2014

Cute example.  Perfect for people who live on their own acreage, low relevance to most of the world’s population.  

We have lower eco-foots when we live closer together, in suburbs or in cities.  This greatly reduces our energy needs for personal transportation, which is around a third of our total energy footprint.

Once we live closer together, grid connections between homes will reduce the need to oversize power systems by reducing per-capita peak demands.  Consolidating fuel-powered backup systems will reduce total cost and allow improved effficiency. Separating the energy generation from the home will reduce the very large up-front cost barrier to home ownership, which is of large benefit to society and especially to the poor.

Note that super-insulation and energy generation systems must also earn their way into the houses and building codes.  If you chose an insulation level that takes say 20 years to pay for itself in energy saving instead of 3 years, then again you are creating an additional barrier to home ownership thus doing real harm to the poor. 

Once the energy system is away from the house, then energy storage and back up can be greatly improved.  Ammonia becomes preferable to gasoline for back-up, as ammonia can be made from uneeded sustainable electricity, and it eliminates CO2 emissions. 

With homes connected to neighborhood microgrids, it is very little extra cost to aggregate the microgrids into city-scale grids.  As described in the article, pumped hydro storage is much better than batteries for EROI (cost is also much better).  Using an electrical grid to aggregate demand also allows mega-Watt scale wind turbines to supplement or replace kWatt-scale rooftop solar.  Because wind speeds increase with altitude above the ground, larger/more powerful turbines are more cost effective and have better EROI (to get back on topic).  The industrial nature of wind farms means that the waste problem is more manageable (compared to distributed solar), and the waste (mostly concrete and steel) is more recyclable and more benign anyway.

As discussed in the article, switching from wind+storage to nuclear will further improve the EROI.  It also reduces our eco-footprint.

Robert Bernal's picture
Robert Bernal on Sep 1, 2014

Utilizing wastes are just a part of being efficient at the demand side. A dependable supply side? Nowhere close.

In the future, we must have a supply of dependable energy. If the EROEI for that energy goes down to about 7, then its storage must be of high energy stored on investment, or ESOI (such as pumped hydro which stores hundreds of mutiples of the energy required to make it, in its entire time of operation). If the EROEI is above 20, then there is simply no reason to worry about near perfect insulation and end use efficiency (unless from finite sources). At that rate, just a few percent of all activity is energy related and an excess can be used for lessor quality storage. Better to have a draft than to trap radon, for example.

If lead acid backup for solar off grid houses are used then that is a contradiction of the meaning “efficient”. This is because the batteries (lead acid) only store twice the energy in their entire life cycle as it takes to make them! Now, if a much higher (or more dependable) source was used, then we could afford the luxury of not having to worry that much about energy inputs for storage.

Once the overall EROEI gets below 3, such as from the foolish practice of wasting energy to develop tar sands and biofuels as primary sources, then civilization actually collapses because we actually need lots of energy just to grow food (to make ammonia), let alone hunt for more energy and maintain (and grow!) the modern civilization.

We can NOT wean ourselves from fossil fuels if we don’t secure alternative high EROEI sources.

Robert Bernal's picture
Robert Bernal on Sep 1, 2014

PV can’t last that long because the (non glass) sealant materials will not stand up against the sun and weather for that long. An NREL report states that PV takes about 3 years of normal use to recoup. Electricity (for the massive arc furnaces used in PV manufacture) requires almost 3 times thermal, for generation. I like the favorable number of 20 for wind, however, which can “energy pay” for itself, its mainenance and its storage (especially if that storage is of a high energy stored on investment – ESOI). Oil is still way above just 1 or 2 (thankfully). We WILL need it to build advanced nuclear and wind power.

I doubt that such a highly dense energy source as nuclear only getting 10. If conventional LWR nuclear has that bare minimum of 10, then advanced closed cycle nuclear would have a very much more favorable EROEI. This is because material inputs are less, processing is FAR less, waste mgt is less and the output temps are higher. In fact, there is only the need for the one time start up fissile and to “ready” spent LWR fuel to be used as fuel. From there, no energy related mines needed, ever, for hundreds of years, thus lowering energy inputs even further! Such high EROEI would easily enable storage options with negative ESOI, such as clean liquid fuels and primary, non chargeable batteries.

Robert Bernal's picture
Robert Bernal on Sep 1, 2014

Any source that says nuclear only has 2 is not close to reality. Aslo, search for oil, and you’ll see that it’s still in the 10 to 20 range (thus another reason not to trust the 8020 site).

Clayton Handleman's picture
Clayton Handleman on Sep 1, 2014

This is an interesting topic, thank you for the post.  I have added here one graphic that I found very helpful in wrapping my mind around the discussion. 


James Thurer's picture
James Thurer on Sep 1, 2014

I congratulate the author for highlighting and quantifying the importance of the energy costs of storage in evaluating the feasibility of various energy sources.  This is a very important factor that is commonly overlooked by proponents of renewable energy sources, particularly solar PV.

There are problems, however, with the derivation and application of the threshold EROI value of 7 for the development of buffered energy sources.   A review of the referenced article indicates that the threshold value of 7 is derived by estimating the ratio of the “energy value” of an economy (i.e., (GDP)/(total energy consumption) to the average electricity cost in that economy.

A problem with this logic is that does not consider external costs or savings associated with various energy sources.  The external costs are both environmental and economic.  For example, not only does the widespread burning of coal act as a major source of greenhouse gas generation  and ocean acidification (with associated economic costs), it also has a strong negative economic impact in terms of health effects to humans.  The health effects greatly increase the cost of health care, in addition to lost productivity.  Another example of an external cost is the cultivation of biomass, which can result in the excessive diversion of agricultural land from food production, thus increasing food prices.

Another problem is that the high threshold value of 7 applies only to highly developed economies, such as the U.S. and Germany.  As is mentioned only briefly in the article, the threshold value for less developed countries would be significantly lower than for highly developed countries.  

The information presented in this article might be best used as a guide to a relative ranking in allocating resources in energy development in various circumstances, rather than as a cutoff criterion.  For example, it may well be beneficial in a developed economy to invest in buffered wind energy if it displaces coal, even though its EROI is well below 7, because of environmental factors and reduces health costs.  Similarly, it may be worthwhile for a less developed economy to invest in buffered wind, because its (GDP)/(total energy consumption) ratio is low enough to justify it.

Robert Bernal's picture
Robert Bernal on Sep 1, 2014

I think the point is we need a high EROEI source. If we do not choose advanced nuclear, then we will have to develop wind, which is higher than solar. Most graphics show that wind actually competes with nuclear, but nothing could ever compete with the closed cycle. I ask, how can such a dense form (regardless of type) be so low on the EROEI scale! Low density sources which requires large fractions of output just for storage is NOT acceptable (unless on the small scale, as for off grid solar and lead acid, and made from higher non fossil sources).

Nevertheless, if the threshold for a modern society is really as low as 7 and is set to be some kind of target, given the total losses from the embodied energy for storage, the storage inefficiencies and conversion inefficiencies, we still need to achieve an overall averaged out net energy availability of above 7. This is because we currently do not have to account for these things (at the large scale) and because our finite and environmentally destructive sources are still way above 7. Our economy might not survive anything less!

Others and I have already suggested that we need even more to account for the energy required to deal with the adverse effects of fossil fuels, as well. Imagine if we had to input fully half the energy from a solar powered world just for climate change mitigation and excess CO2 removal.

If we were to use 100% PV (at, say 10) and lead acid with an energy stored on investment, or ESOI of only 2, we would collapse (especially because the poor CF of the solar requires even more storage, and because the efficiency of that storage is rather low for the round trip). This is why we should use the much higher EROEI sources to make these things. Then storage, no mtter how ESOI poor, would be considered just another required input to get the job done. Liquid fuels made from air and water such as ammonia would have to have an ESOI of less than 1, yet WILL be required in large part in a fossil free society.

Obviously, utility scale storage should be the high ESOI of pumped hydro, if we are not going to rely mostly on closed cycle nuclear.

Roy Wagner's picture
Roy Wagner on Sep 1, 2014

This report from the Global Climate and Energy Project, Stanford University, Stanford, USA is another ESOI comparrison between energy storage mediums.!divAbs...


Robert Bernal's picture
Robert Bernal on Sep 1, 2014

Everything including all the wastes requires fossil fuel input. Take away the fossil fueled input and there will be nothing, no way to build batteries, no way to haul around wastes for recycling, ect. How do you power a society from trash? There is a net loss from each of all the conversion processes to make that “trash”, to use that “trash” and finally to burn or recycle that “trash” (still better than just throwing that trash into a pit!).

Anyways, Hopefully, you’re correct about solar lasting longer, to get a higher eroei (and I’m sure the tech can improve even more). About the only thing we disagree is about advanced closed cycle nuclear (as that is on the order of 100x cleaner than the LWR). There should be an international effort to deploy it globally (I don’t see why we should limit our clean energy options unless they are of such low density such as the tar sands and corn ethanol).

Also, I ragged on the lead acid batteries, but if we secure high EROEI sources, then it simply does not matter (just as “everything else” like cars and TV’s do not even store energy). In fact, for stationary, they are on the order of 4x more efficient than clean liquid fuels (and they are recycled).

Robert Bernal's picture
Robert Bernal on Sep 2, 2014

I like the concept of being able to power everything without nuclear (and fossil fuels), just want to make sure that we can really do it. You said that silicone sealant can last a hundred years (without yellowing?). If so, then PV can have really high eroei. I agree that they can be made even cheaper. But in the meantime, don’t we need a source to make liquid fuels for the machines to build pumped storage (you will never convince me that there is enough energy in trash to do that and backup solar)?

I believe wind is even better because it has a higher eroei. Nevertheless we still have to convert much of that into clean fuels, as well.

My concern is that fossil fuels are FAR more dangerous than any nuclear!

We should at least use nuclear in the next few decades to make the million or so square miles of solar necessary to power a planetary civilization AND its continuing expontiation, the power for excess CO2 cleanup, etc. Also to make the clean fuels for massive pumped hydro storage, and also to green the deserts (which could eliminate the need for mineral CO2 sequestration).

Repeat, FF’s are far more dangerous than nuclear, and nuclear is needed to kickstart the renewables into a power source MORE powerful than the FF’s they will replace.

Nathan Wilson's picture
Nathan Wilson on Sep 4, 2014

Personally, I’m still waiting for EVs to be proven to be environmentally friendly.  Sure they are more energy efficient than vehicles burning synfuel, but they create a chemical waste disposal problem.  Maybe we’ll solve the problem, maybe we won’t.  

For a specific example, lithium-ion batteries that have 1900 cycle endurance and 150 Wh/kg energy density, when used to store 1 GWatt of power for a fleet of vehicles (something like a small cities’ worth), would produce 31,000 tons of decomissioned batteries each year.  If 99% gets recycled and 1% goes into land fills, thats 310 tons per year!

Nathan Wilson's picture
Nathan Wilson on Sep 5, 2014

The viability of a given level of electric generation is completely determined by cost.  If syn-fuel is affordable, we’ll find a way to make enough (assuming we choose a syn-fuel made from plentful and cheap feedstocks, as is the case with ammonia or hydrogen).

It is easy to show that syn-fuel can be made for a cost that is in the right ballpark:  the conversion factor is 34kWh per gallon-of-gasoline-equivalent (gge, energy basis).  That means that if you buy electricity for 5 ¢/kWh (which you can do with near central plains wind farms, older US nuclear plants, or brand-new Chinese or Indian nuclear plants), and the chemical synthesis plants makes the energy cost double (due to added capital cost and efficiency loss), then the fuel will cost $3.4/gge before distribution costs and profit (note that ammonia ICE cars will get 20% more miles-per-gge than gasoline cars, for the same reason that diesels do – the engine can be tuned for higher efficiency).

The Europeans have already done the expensive fuel experiment (by adding high taxes).  The result is that even in cities with great mass transit, the roads are filled to capacity with cars.  Another shock is that high fuel cost has not given Europe a particular boost in EV or hybrid adoptions.

To answer the question of whether people will prefer expensive fuel or a 10′ tall pantograph attached to the top of their cars, just look at what people buy today.  Electric buses and trolleys have been around for decades in many cities, and no one is rushing to buy cars that hook into the bus system, even though it would result in cleaner air, fewer trips to the gas station, and more energy security for the nation.

Nathan Wilson's picture
Nathan Wilson on Sep 5, 2014

Here’s a photo showing a vehicle with over-head power lines (the pantograph articulates to maintain contact with the wires; I doubt that you are the first person to wish it were less obtrusive):




Roy Wagner's picture
Roy Wagner on Sep 5, 2014

Here is a better solution

Inductive charging wireless whilst vehicle is in motion or at rest in traffic.

Nathan Wilson's picture
Nathan Wilson on Sep 5, 2014

Your $9T cost estimate for the global ammonia fuel system  does not impact any decisions, because there is no global energy authority.  The decisions are made by fuel companies who will be equally happy selling syn-fuel or fossil fuel, and car buyers who must decide between highly visible pantographs and hidden fuel tanks.  

Oh, and don’t forget that the pantograph cars are worthless until much of the city is wired with overhead power, presumably paid for by a polarized/paralysed government.  The ammonia system can start with half a dozen refueling stations per city (supplied via truck, so even pipeline infrastructure can wait).  And it will be easy to make the first round of ICE ammonia cars have gasoline tanks as well (mixing pantographs with gasoline backup gives the worst of both worlds).

Nathan Wilson's picture
Nathan Wilson on Sep 5, 2014

If you don’t need to change lanes, go backwards, or cross an electrified street, there is this system.  (I think electric buses in some cities use a dual wire version of this, so that no electric rail is required): 


Here‘s the wiki page on rail pantographs.

Nathan Wilson's picture
Nathan Wilson on Sep 5, 2014

Yes, in-route inductive power transfer is elegant and appealing; the main problem is the cost.  It is much more expensive than over-head lines.  It has a very severe chicken-and-egg problem.  The compatible cars are worthless until the infrastructure is in place.  

The infrastructure, when amortized across the cars it serves, will have astronomical per-car cost initially.  Even once the cars achieved high market share (which would take decades), it will still have poor consumer acceptance, since the cost must inherently be paid to a monopoly supplier, such as the government.  Also, it add complextity, which will means the roads are distrupted by construction and repairs a higher percentage of the time.

Nathan Wilson's picture
Nathan Wilson on Sep 5, 2014

There is not now, nor will there ever be a shortage of sustainable energy resources.  As long as there are customers will to buy $4/gallon-equiv fuel, industry will build the facilities needed to make it.


* the graphic ignores all of the thorium and 99.999% of the uranium in the world (ideological bias).


Robert Bernal's picture
Robert Bernal on Sep 5, 2014

A better solution is to design the city from the ground up. Only small battery packs would ever be required for commuter traffic. The “cars” could be designed to transport on overhead minirail, in and throughout the city on many of multiple levels. No stop lights and no rush hour (and everything within a couple of kilometers).

Only “city to city” traffic would use the much larger amounts of energy required to make larger packs or fuels. I believe that even though the fuels are less efficient than batteries, they could still be made as long as the energy source itself has an eroei of at least that of wind power and nuclear.

Robert Bernal's picture
Robert Bernal on Sep 5, 2014

Battery powered vehicles require less energy but industrial equipment requires liquid fuels.

Both technologies must be able to weed out the fossil fueled laws against them, which are the so called “safety” laws against nuclear and the nimby and enviro laws against PHS, wind and solar.

Established businesses (and governments) are obviously threatened by the unlimited clean energy that nuclear, wind, (higher eroei) solar and PHS offers.

Roy Wagner's picture
Roy Wagner on Sep 5, 2014

Where is the information you base the cost comparrison on?

Street Trolleys as the one in your picture that require overhead cable systems and possibly in road rail systems would cost considerably more.

Induction circuits are already being installed for some buses why not let cars use the same infrastructure?

Electric cars do not need a continuous supply however their range would be extended by such a system as could local delivery vehicles.

A electric road toll could be required and collected using transponders just as road tolls for bridges and expressways pay for these special roads we have now. 


Nathan Wilson's picture
Nathan Wilson on Sep 6, 2014

See reply upthread (I wanted more width for pictures).

Robert Bernal's picture
Robert Bernal on Sep 7, 2014

The LiFePO4 battery is even less toxic, provides more cycle life, has more power density, and is less prone to thermal issues! Its only drawback is the fact that its not deemed goodenough (and slightly less energy density).

Roger Arnold's picture
Roger Arnold on Oct 14, 2014

Ammonia is not an absurd proposition. There is and will continue to be a need for fuels with much higher energy densities than batteries will ever be able to deliver. Air transport is an obvious case. Ammonia is not a great fuel for such applications, but it’s easy to make and generally adequate. It’s particularly good as a store for hydrogen, in applications that employ high temperature fuel cells for portable electricity.

The interesting question for me is whether the comparative easy of synthesis of ammonia is enough to outweigh its lower energy density, compared to synthetic gasoline and diesel. But addressing that is a deep dive into details of reaction kinetics and process yields, in a dynamically evolving world of chemical process technology. Way above my pay grade. I’m happy to let industry sort that one out. 

Clayton Handleman's picture
Clayton Handleman on Oct 14, 2014

Consider contacting Richard Perez.  He is a busy guy but accessible.  Mention your thoughts about the bias of the graphic and see what he says.  He is easy to find with a few minutes of Google time.  Last time I went looking for him he had a web page that was reasonable inviting and did not occur to me as a firewall.

He has always been a strong advocate for solar energy but also is respected and seems to strive to be objective.

Robert Bernal's picture
Robert Bernal on Oct 15, 2014

It could be used to fill in for load following rather than building extra pumped hydro or molten salt storage. If solar really kicks butt, then nuclear would have to make large amounts of it in the day, just to keep operating and to prevent even more fossil fuels combustion at night. It would seem that there would be extra to sell to the liquid fuels market. Also, that infrastructure would “set in” as CO2 restraints increase, to power much of the remaining non battery machines.

I agree, it would be far more efficient in the long run to design “everything” to run on batteries, however, a source such as advanced nuclear can “afford” quite a bit of inefficiency. It might even compete directly with propane and future natural gas.

Roger Arnold's picture
Roger Arnold on Oct 15, 2014

Most of the comment threads below have drifted considerably away from the thesis of the article — that when sufficient energy storage for buffering the intermittency of renewables is added to the system, its net EROI becomes too low for economic viability. It’s an interesting thesis. I don’t entirely buy it, but I wish that more of the comments had addressed it.

I’ve never been a big fan of EROI analysis. I don’t fault its good intentions, but it pretends to a fundamental validity that I don’t think is warranted in practice. For one, there’s the “boundary problem”. How does one decide where to draw the line for what you count as “energy in”? A classic example is “the kids’ soccer practice”.  If someone is employed in the nuclear industry, should the gasoline used to drive their kids to soccer practice count as “energy in” for nuclear power? The methedologies for some analyses have implicitly said “yes”. That’s how one manages to get the EROI number for nuclear power to come out low. The rules for drawing boundaries are inherently fuzzy, and can easily be warped to suit the analyst’s agenda.

That’s not to disparage the honest work of professor’s Weissbach, Hall, et. al. They are trying to get at something that is genuinely important. But even the most rigorous of analyses are forced to resort to an artificial “cost to energy” equivalence ratio for estimating energy in. There is, for any nation, an overall ratio of GDP to energy consumption that is easy to find. When the actual energy inputs needed to produce some particular component of a system are too diffuse and difficult to identify, the fallback is use its cost as a proxy for its energy in.

That may be the only reasonable option, but it can’t account for factors that cause wide variations on the actual cost to energy ratio for real components. What’s the “energy in” to produce an aspirin pill, for example. If the pill comes from a bulk purchase from a pharmaceutical supplier, its cost will be a fraction of a cent. If it was administered in hospital, its cost might be $10. So what’s “the” energy cost to produce an aspirin pill? On the basis of a cost to energy equivalence ratio, the answer will differ by three orders of magnitude depending on what cost is chosen.

In the end, it seems to me that EROI analysis is simply an economic analysis denominated in joules rather than dollars (or pounds or whatever). It’s obviously true that an energy system must produce a healthy surplus of usable energy over and above its input requirements in order to be sustainable. However, stating that its EROI must be greater than some specific over-unity value is really a statement about the fraction of GDP that the analyst believes we can devote to energy without major impact to the economy. It may be accurate, but it’s not fundamental. Economies do reshape themselves in major ways over time.

Bas Gresnigt's picture
Bas Gresnigt on Oct 17, 2014

This German simulation study shows the results of four different scenarios with variables; storage*), flexible load, different mix’s of solar & wind with increasing shares of those in electricity production.
The study shows that with flexible power plants (so after 2023 when all nuclear is gone), the losses & cost due to storage will be minimal even while the share of wind and solar is 35% – 50%.

Restrictions of the simulation study, such as no im- and exports, imply that in reality results with high shares of wind & solar will be far better. Especially since Germany’s interconnection capacities to the Nordic and the alpine countries are expected to be increased.
E.g. Netherlands is implementing two new high capacity interconnections, so NL can trade more electricity.

Hence little losses & costs to be expected until wind & solar have a share >70% in the electricity generation.

*)  I assume that 40GWh storage with a capacity of 9GW was chosen, because the ~35 existing pumped storage facilities in Germany have similar capacity.

Nathan Wilson's picture
Nathan Wilson on Oct 18, 2014

Why do I predict that in the future, people will prefer cars with internal energy storage rather than powered from overhead wires?  Because internal storage is what the vast majority of people have used in the past, and continue to choose today.  There are plenty of trolley and bus systems around to demonstrate the concept; there is no market for cars powered in this way.

If you look at the cost of fuel in places like American and the UK, the cost range is huge.  I can only conclude that the cost of fuel doesn’t matter, people love cars with internal energy storage.

Nathan Wilson's picture
Nathan Wilson on Oct 18, 2014

I advocate starting to move forward today with ammonia fuel, knowing full well that the transition to non-fossil energy will take many decades.  In particular, I expect we (in the developed world) will be using fossil-derived transportation fuels long after we stop using fossil fuel for electricity (renewable and nuclear electricity is rather low hanging clean-energy fruit).

So in this syn-fuel future, with no fossil fuel used for electricity, from where is the CO2 for synthetic gasoline going to come?

As of today, direct air capture of CO2 will make syn-gasoline hopelessly uncompetitive with ammonia.  I realize that not everyone will want ammonia in their cars, but for those people, battery electrics are available.  We’ve discussed sea-based CO2 capture on TEC before, but I thinks that only works for mobile systems like OTEC and aircraft carriers, due to poor mixing.

Roy Wagner's picture
Roy Wagner on Oct 18, 2014

Meanwhile in the real world right now in Berlin they are testing inductive charging for buses this system could be extended for car use.


Nathan Wilson's picture
Nathan Wilson on Oct 18, 2014

Grid energy storage is not necessary with the right generation mix and with enough dispatchable load.  And the ultimate dispatchable load is fuel synthesis, since the market for direct fuel use is about double the size of the electric power industry.

The best kept secret in the energy industry is that ammonia can be used as a fuel for transportation or stationary power, in just about any application that uses gasoline or diesel.  And ammonia is the cheapest fuel which can be made from solar, wind, or nuclear energy (the only other ingredients are water and air).

This link describes a recent conference on ammonia fuel.  There are several demonstration programs going on around the world.  The only thing missing is public awareness (i.e. it is not being promoted by any of the big energy companies).

Robert Bernal's picture
Robert Bernal on Oct 18, 2014

I would think it’s easier to make ammonia than carbon based fuels from clean sources of heat and electricity. I believe there are ways to extract the energy from it without emitting much N2O. The main components is water, not the greenhouse gas, thus should be much less of a problem.

Nevertheless, I agree that the production methods of the other forms of storage should be developed to reduce costs. Batteries require a 2 dimensional boundary which increase costs compared to the volume of heat and gravity storage. This is one reason why I believe there will be no mainstream utility scale battery storage except as a bridge for whatever small amount of time needed to utilize the other storage sources.


Robert Bernal's picture
Robert Bernal on Oct 18, 2014

Bio fuels can’t scale  unless we first green the deserts. Perhaps they could be used for turbine combustion in place of ng as an intermediate until some other slower form of storage meets demand.

I agree that the entire fleet should be electric due to reasons of both efficiency and EROI.

Nathan Wilson's picture
Nathan Wilson on Oct 18, 2014

It is true that burning ammonia produces more nitrogen oxides than gasoline, but it is also true that having small amounts of ammonia in the catalytic converter allows more effective cleanup of the exhaust (some power plants use this trick today – see SCR).  As a result, mass market ammonia fuel vehicles will meet the same exhaust standards as today’s cars, with no CO2, sulphur, or particulates.

Saying we should ignore a proven (bird in the hand) technology like ammonia fuel, in the hopes that a breakthrough in some other area (CAES, pumped hydro or whatever) strikes me as a bad idea.

The other syn fuels that are in use today are just distractions and ways to prolong the use of fossil fuel (often coal, the dirtiest of fuels).  We’ll phase out fossil fuels first in electric power, and later in transportation fuel.  So by the time synfuel made from renewable and nuclear power becomes big, there won’t be much CO2 available for making hydrocarbon synfuel (direct air capture is CO2 is expensive, uses a lot of water and land).  We can get enough CO2 from cement making to fly our airplanes, but not much more.

Sure hydrogen synfuel will have a market.  It is great for baseload applications like steelmaking, when produced from a baseload source like nuclear.  But with excess spring/fall windpower and summer solar, we’ll need seasonal energy storage, which can only be done with liquid fuel, such as ammonia.

Ammonia is a much better car fuel than hydrogen also, with double the energy density of 10,000 psi H2, and 30% better than CNG (GNC is near the pain threshold, so H2 has a big problem).  Ammonia is a clean fuel when used in fuel cells or piston engines; it’s cleaner in piston engines than hydrogen too, because H2 burns hotter, making more nitrogen oxides.

I agree that hydrocarbons are better automotive fuels than ammonia, but only slightly better.  We can make the compromise to get the environmental, climate, and energy security benefits (in fossil fuel importing countries it could be cheaper too).

Robert Bernal's picture
Robert Bernal on Oct 19, 2014

My understanding is that the higher the EROEI, the lower the ESOI necessary. If we power a world on solar which is estimated to have eroei of 7, and if we need to store the inverse of its capacity factor in a medium that gets less than .5 (say, ammonia), then overall net energy to society would either be impossible or require such vast amounts of land to make it almost impossible. If we stored it in batteries that get an ESOI of say, 10, then we can net a lot more energy with less land covered. And with pumped hydro, better yet.

If we use advanced nuclear, then we can obviously afford the low ESOI of ammonia, especially since it has a much higher capacity factor.

Nathan Wilson's picture
Nathan Wilson on Oct 19, 2014

Presumably the anti-nuclear bias in the graphic results from Perez’s own bias (i.e. his comparison assumes nuclear power which is limited to the most common and most economical form, but uses a solar interpretation that assumes future breakthroughs in storage and economics).  My goal is not make everyone share my biases, but rather to simply insure both sides of the issue are available for seekers.

Clayton Handleman's picture
Clayton Handleman on Oct 19, 2014

The reason I suggested you contact him is so that you don’t have to presume.

Richard was promoting solar at a time when he was in the vast minority.  He has worked hard to use the system to monetize those benefits that the current system ignors.  What looked like overzealous idealism a decade ago now looks like wisedom in hindsight.  He may benfit from your insights on nuclear power.  You many benefit by learning why he is not sharing your perspective on nuclear power. 

Whether I agree with the conclusions that are to be drawn from his work or not, I rarely go away without finding value and the efforts of a well thought out position. 

Anyway, if you don’t, I may have time in December as I am a bit curious myself.


Roy Wagner's picture
Roy Wagner on Oct 19, 2014

One of the misconceptions about energy storage is the total conversion losses.

It is possible with Solar thermal to directly store heat energy and with Wind and Wave to directly produce compressed air instaed of electricity.

Compressed air is a dispatchable potential energy that can be used for electricity generation on demand.

By using these renewable sources to store energy directly instead of into electricity then storing surplus electricity by converting them in some other way makes them much more efficient.

The total useable energy is increased in this way, in the case of compressed air it can also be transported by pipeline (additional storage capacity) and can be converted to electricity onsite on demand.

It can even be used for transportation uses on a campuses, airports or military bases. 

Robert Bernal's picture
Robert Bernal on Oct 19, 2014

I like the idea of super efficient (auto)mobiles and realize that we humans are very inefficient when it comes to having to waste all that momentum, having to stop all the time, and “inchworming”, not knowing how to conserve momentum, etc.

I’m just afraid of computer crashes due to animals and unexpected events. I better like the idea of personal rapid transit. At least, there would be less stops (or crashes) due to such events. And, I believe, they could be safely electrified ditching the need to carry fuel altogether!

Roger Arnold's picture
Roger Arnold on Oct 19, 2014

So in this syn-fuel future, with no fossil fuel used for electricity, from where is the CO2 for synthetic gasoline going to come?”

Two obvious and easy sources: (1) cement  production, and (2) biomass. Biomass itself can be used in a couple of ways. One is fermentation to produce alcohols, followed by capture and utilization of the CO2 stream from fermentation. Roughly doubles the liquid fuel yield per ton of biomass. The other is low temperature pyrolysis to produce syngas, condensible liquids, and biochar. Fuel yield per ton won’t be as high as the first approach, but the biochar, used as a soil ammendment, sequesters carbon and enhances soil fertility.

The amound of liquid fuels produced by these means won’t be large compared to current production of petroleum-based liquids, but it won’t need to be. Batteries, direct electrfication, and a diminished need for personal transportation due to increasing role of VR-based telecommuting and home shopping (the latter aided by efficient semi-autonomous delivery services) — all that will substantially reduce the need for liquid fuels. 

Reduced demand for liquid fuels will probably become economically significant even before oil production declines sharply. Also, it’s not an either/or choice between ammonia and carbon-based synfuels that we’ll be looking at. They will co-exist and compete for market.

I suspect that ammonia will find its most secure niche as a hydrogen source for FCEV’s, in competition with batteries more than with carbon-based synfuels. The latter will be important for aviation and in competition with oil for the legacy vehicle fleet.


Nathan Wilson's picture
Nathan Wilson on Oct 20, 2014

When you predict computer driven cars will displace human driven cars, I assume you mean computer driven taxis will replace personally owned cars (whether computer driven or not).  

Sure it might happen, but it is extrordinary to claim with confidence that it will, since personnally owned cars greatly outnumber taxis today.  

The biofuel solution also requires extrordinary reductions in fuel consumption per passenger-mile travelled.

Extrordinaryclaims require extrordinary proof, and I have not seen it for either of these claims.

Nathan Wilson's picture
Nathan Wilson on Oct 20, 2014

But long-cycle-life batteries don’t exist yet for cars (in deep cycle).  The high temperature sodium-sulfur (liquid metal) batteries are claimed to have 20 year lifetimes with daily cycling, but these are unsuitable for cars.  Li-ion researchers have claimed long cycle life for laboratory samples, but the batteries on the market today are only good for a few thousand cycles (Tesla‘s entry level model has a 125,000 mile battery warranty).

Of course shallow-cycling extends cycle life, but that doesn’t fix the economics, since it makes the battery more expensive for a given daily mileage.  Also, it makes the vehicle heavier and less energy efficient.

Roy Wagner's picture
Roy Wagner on Oct 20, 2014

I suggest you read about Tesla’s latest model S and the self driving features available today.

Watch them here

Roy Wagner's picture
Roy Wagner on Oct 20, 2014

125,000 miles is about 10 years of use for the average driver, during the next 10 years battery performance will inevitably improve as will the cost.

This is comparable to the warranty on most internal combustion drivetrains available today.

Tesla also offer to buy back the car after 3 years at 50% of cost if you upgrade to the newer models.

Robert Bernal's picture
Robert Bernal on Oct 20, 2014

With hydrocarbons, the end result will obviously be less than 1 unless we use them to develop a source that has more global potential and which has a high enough eroei (and a high enough capacity factor) to deal with whatever low EROI which best fits convenience.

Roy Wagner's picture
Roy Wagner on Oct 20, 2014

The oceans are one increasing source of CO2 which I thought was a problem not a solution.

Here is an interesting Hydrogen production technology that can sequester CO2 and/or reduce concentrations in seawater.


Roger Arnold's picture
Roger Arnold on Oct 20, 2014

Indeed. “Carbon-negative” hydrogen production is an intriguing concept. It’s very promising, but it needs funding to move it beyond its current status as a laboratory curiosity toward something that might prove economically viable.

So far, professor Rau hasn’t had much luck in obtaining funding. It’s too much “applied R&D” for the NSF and academic science organizations, and too “academic” to attract attract venture funding. This country really needs a mechanism to address that class of development.


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