Part of Grid Network »

The Grid Professionals Group covers electric current from its transmission step down to each customer's home. 


You need to be a member of Energy Central to access some features and content. Please or register to continue.


Fads and Fallacies of the Energy Transition

image credit:

Warning: this blog article is rather more strident than most.


The energy transition isn't carefully thought through – it’s driven by fads, the current ones being batteries, distributed, virtual and demand-side. They all fall down on a number of factors, including:

  • All are small-scale and rely on the grid for back-up: what's on the grid providing that back-up? (Us...)
  • All are DC connected and therefore have no inertia, real reactive power/load, grid-forming capability (unless expensively fitted out), voltage/frequency regulation etc.: what provides those naturally? (Us...)
  • All are small scale: how do they expect to solve GW scale problems with kW or MW scale solutions? (We're at the right scale...)
  • What happens after sunset on a windless winter evening, when batteries and DSR are exhausted by 6pm and there's no real power for virtual solutions to optimise? (Us...)

When confronted with those, they all fall back on fad no. 5, interconnectors, saying that if renewables aren't generating somewhere, they are generating somewhere else:

  • Sunset on a windless winter evening happens across Europe simultaneously. Weather patterns extend this to up to a fortnight (the kalte Dunkelflaute, cold dark doldrums). What then? (Us...)
  • For generation from one corner of Europe to be balancing lack of generation in another would require 2,000-mile transmission lines of at least 500GW going along all points and half-points of the compass: prohibitively expensive, and environmentally unacceptable...
  • ...And it would require enormous over-capacity of generation in every single corner of Europe to make up for lack of generation elsewhere – which is also prohibitively expensive, and environmentally unacceptable.
  • And the interconnectors are DC systems, so carry no real inertia or real reactive power/load etc.

At this point they jump on fad no. 6, hydrogen. However:

  • If electrolysis absorbs the intermittency of generation, it needs 3-8 times as many expensive (both capex and opex) electrolysers...
  • ... and doesn't solve the problem of variability of demand, unless you burn hydrogen in turbines which has a theoretical maximum efficiency of barely over 40% for the electricity-to-electricity cycle, compared with our 70% with much cheaper kit.
  • Hydrogen is great for feeding into industrial-chemical processes (e.g. steel making), the gas grid and use cases where the output is not electricity (e.g. fuel cell vehicles where the output is portability and motive power), but not where the output is grid-based electricity.

The final fall-back, fad no. 7, is CCS (carbon capture and storage) generation. This is advocated by the hydrocarbon industry desperate to get governments to invest billions and adopt burdensome legislation, all to give them a future. But they usually fail to consider a number of points, including:

  • CCS equipment imposes a 20-30% inefficiency on any power station to which it's fitted, while increasing capital costs greatly.
  • Carbon capture effectiveness (i.e. capture %) isn't perfect (~85-90% in systems that are put forward as being potentially affordable within a decade or two), and its cost and inefficiency penalty increase exponentially with capture effectiveness.
  • Any leak in the capture equipment, pipeline or storage location would cause an asphyxiating cloud of CO2 that would drift over population centres like a WW1 chlorine gas cloud, only it can't be seen or smelt, or fought by simple means (chlorine is resisted by breathing through a wet rag), and is 50% heavier and therefore much slower/harder to disperse.
  • Most carbon usage (the U in CCUS) is merely delaying the emissions, not preventing them.

Which all begs the question: why are policy makers and regulators so determined to ignore large-scale long-duration storage, which can resolve every one of these issues? It has frequently been described as the missing link or Holy Grail of the energy transition, yet policymakers are determined not to support it with financing first-of-a-kind commercial-scale plants, and regulators are determined to undermine it by mis-defining storage as a type of generation, by eliminating contracts of durations that encourage investment, by salami-slicing contracts which split up services that such storage cannot deliver separately, and by wasting billions in supporting technologies that, frankly, can’t do the job. That is not to say that those technologies are wrong: they have their place. But people seek magic bullets, one-size-fits-all solutions. They don't exist. But they do give them hundreds of excuses for not considering the issues in the round. Or, more bluntly, for giving as little thought to the challenges as they think that they can get away with.


Instead, a cost-effective energy transition requires an entire ecosystem not just of zero-carbon generation but also of supporting technologies, as described in a previous blog article. And it needs to be regulated sensibly, as outlined here. Storelectric has published many supporting articles on its website, such as on:


Matt Chester's picture
Matt Chester on Oct 22, 2020

It has frequently been described as the missing link or Holy Grail of the energy transition, yet policymakers are determined not to support it with financing first-of-a-kind commercial-scale plants

If, hypothetically, the pursestrings were open and all the funding the energy storage industry could imagine were made available, how quickly do you think the energy storage industry theoretically would see a rise in efficiency & cost-effectiveness of these solutions compared with the status quo? 

Mark Howitt's picture
Mark Howitt on Oct 22, 2020

Storelectric already has technologies that are already there, and able to be built at sizes greater than 100GW / 5-12 hours tomorrow. Extending beyond 12 hours will require a different geology, which will take 3-5 years more.

Our TES CAES is 70% efficient now (at scale), zero emissions, cheaper than traditional CAES; it additionally provides enormous mutual benefits if installed in conjunction with renewables e.g. on the cable from a wind or solar farm. Our CCGT CAES is 57% efficient, much cheaper though it emits, therefore higher returns on capital at least in the short run. Our CCGT hybrid is more efficient and less emitting than our CCGT CAES, with better returns and a price point between the two. Both the last two can uniquely be retro-fitted to suitably located gas-fired power stations. All deliver double digit IRRs in todays market, depending on the jurisdiction / regulatory landscape.

The lead time to plan and construct such plants is 3-7 years. But we can do a number concurrently.

Roger Arnold's picture
Roger Arnold on Oct 23, 2020

Mark, your idea of "strident" is pretty mild. You've got to be old school British or Canadian.

I happen to agree with nearly everything you say above. Fads prevail, inflated, unwarranted hopes pinned on batteries (both real and virtual), and demand side management. Not that there's anything wrong with those things, but they aren't sufficient to get us to where we need to go. They aren't sufficient to deal with extended periods of adverse weather and certainly not sufficient to deal with seasonal variation in solar. One of the options in which we should be investing is more cost-effective and scalable approaches to long term energy storage.

In the dominant green narrative, electroytic hydrogen is the solution for periods dunkelflaute and seasonal variations. That view overlooks the poor round trip efficiency (about 40%) of power-to-hydrogen-to-power. It requires massive overbuilding of renewable generation resources. That overbuilding would consume massive capital, material, and land resources, all for a very low return on investment. It effectively assumes unlimited consumer apetite for subsidation of what the priesthood of green energy deems the proper way forward.

(Now that's what I call strident.)

Your company's idea for TES CAES is an interesting approach for scalable long-duration storage. It's more worthy of development funding than many of the projects that are being supported with EU funds. It's not the specific approach to CAES that I'd recommend, but that's not something to get into here.

I'll say this much, however. The thing you'll be running up against and the chief obstacle to your company's success is the low capital cost of gas combustion power turbines and their low cost of operation in a regime where natural gas is relatively cheap and carbon emissions aren't heavily priced. IOW, dispatched generation from stored fuel, not the stored product of excess generation. Saves the cost of all that overbuilding of renewables, low capital cost for the combustion turbine, and low cost of operation if you can get away with not paying for carbon emissions. That's the competition that ultimately sank Lightsail Energy.


Mark Howitt's picture
Mark Howitt on Oct 26, 2020

And so a Brit is uncovered!

Thanks for your comments, Roger.

I agree: there's a place for all these "fad" technologies. The technologies that enable a Net Zero energy system is like the road system that enables the economy; if we only have freeways and highways, we can't get to our offices, homes or shops; if we only have small roads we can't get anywhere fast or far. All are needed - but to do their appropriate roles, not to be bent out of shape to do different roles. And that includes the overbuilding of hydrogen technologies for wrong purposes, which you outlined. Otherwise we'd develop a system that costs far too much and still isn't reliable or resilient - and this would lose the political and popular will to de-carbonise the energy system. Nothing less than the world's future climate is at stake here.

TES CAES is adiabatic, i.e. it balances the heat over the whole cycle. We also offer CCGT CAES which is a form of traditional CAES that is much cheaper and more flexible, and a little more efficient than the competition. I don't know what kind of CAES you have in mind as an alternative. Some years ago investors wasted over $250m on isothermal CAES (i.e. done at constant temperature) which, of its very nature can't work: it wastes its heat of compression and has to scavenge heat for expansion - but since the volumes of heat required are so enormous, it would freeze both the plant (creating failure) and the environment (snow storms in summer).

Roger Arnold's picture
Roger Arnold on Oct 26, 2020

I usually think of it as "quasi-isothermal CAES". It can also be thought of as quasi-adiabatic CAES on a fluid that has an unusually low value of gamma. Whatever, it's the same thermodynamic approach that was promoted by failed startup LightSail Energy. There was at least one other startup that pursued a similar approach, but their name escapes me.

Lightsail, IMO, made a fatal technical choice in their approach. It was related to a bad business model choice for the early market they were going for. That choice seemed to make sense at the time, but it put them sqarely in the the path of advancing battery storage technology.

I'll be happy to talk about all this in depth, but best off line.

Mark Howitt's picture
Mark Howitt on Oct 27, 2020

I really don't like using "quasi" everywhere: nothing is perfect in this world.

In my opinion Lightsail, SustainX and General Compression all failed because they selected a technology that COULD NOT work: isothermal CAES. Yes, the most efficient way to compress air is at constant low temperature, but once they've removed and lost the heat (at 40oC it's too cold to store usefully or densely), where's the heat going to come from to support expansion? The environment? This would put limits of hundreds of kilowatts on the equipment before you freeze it and the environment.

Our adiabatic CAES has been validated by Costain, Fortum, Arup, Mott MacDonald, Siemens and Mitsubishi Power and others - and the last two say that they can build it with their existing kit. It works, full stop. And all calculated its efficiency, independently and by different methods and referring to different manufacturers' equipment, to within decimals of a % from each other. So Costain, who reviewed 3 other validations too, declared the technology "robust".

Roger Arnold's picture
Roger Arnold on Oct 28, 2020

Lightsail, SustainX and General Compression all failed because they selected a technology that COULD NOT work: isothermal CAES. 

That's unfair. The people who designed the processes were competent. The processes could and did work per design. AFAIK, they met their design specs.

Now, if you meant "could not succeed commercially", that's quite another kettle of fish.

There's a reason I prefer to refer to the cycle that these companies employed as "quasi-isothermal". It has nothing to do with the well understood fact that "isothermal" is a thermodynamic ideal that no real system can truly achieve. 

I use "quasi-isothermal" because there's a fundamental difference between the compression and expansion processes in question and the processes that would normally be termed isothermal. In these processes, the fluid being compressed or expanded is not air; it's an air-water aerosol. A mist. The mass of water droplets in a given volume of aerosol can be larger than the mass of air. The droplets are small enough, however, that the time constant for heat transfer between air and droplet is small relative to the expansion or compression time. The thermal mass of suspended droplets limits the temperature change.

The quasi-isothermal approach to CAES is sound. The reasons the startups trying to exploit did not succeed lie elsewhere.  

Mark Silverstone's picture
Mark Silverstone on Oct 26, 2020

"A de-carbonised energy system would be built up of many diverse elements selected to be the most suitable mix for each location. There is no single answer or “magic bullet”, no “winning technology” for powering the world, or even for providing balancing and ancillary services: the actual answer to questions of which to choose is “all of the above”."

Sorry - I fail to see what is so "strident" about that.  Pretty obvious, no?

Mark Howitt's picture
Mark Howitt on Oct 27, 2020

I would agree, but quite a few people in the sector are so wedded to their own pet solutions being one-size-fits-all that they would find it insulting to be called "fads and fallacies". This includes people in ministries, regulators and grid operators who all have their favoured technologies and argue against a "most suitable mix" until they're blue in the face.

We've even had the Engineering Director of InnovateUK declare "it can't be done" when assessing a funding application in which we quote the MD of Siemens Oil and Gas UK (and give the link to the recording) saying "we have the technology, it can be done, and it will be done". It makes me wonder what he knows about Siemens equipment that they don't. And he's (assuming they're a "he") refused to give me even his name so I can discuss the technology with him: much better to live in his self-delusional bubble.

Mark Howitt's picture
Mark Howitt on Oct 30, 2020

@Roger Arnold,

I can't respond to your post under it, so have to create a new entry.

It's not unfair to say that their process cannot work. Their innovations were all geared towards the most efficient compression possible, and they developed excellent techniques to achieve this. Yes, they were very competent engineers.

But they didn't address the whole cycle. By wasting the heat of compression they created a need to scavenge the heat of expansion. Such amounts of heat are not readily available. so at any substantial scale they would freeze and destroy their plant and/or environment. Or consume energy from outside the CAES system (e.g. combustion) in order to re-inject that heat. So they posited industrial waste heat, but that volume of waste heat is very uncommon and becoming less common every year because any industrial process that wastes such amounts of heat is inefficient and uncompetitive.

Roger Arnold's picture
Roger Arnold on Nov 2, 2020

Their innovations were all geared towards the most efficient compression possible, <..> But they didn't address the whole cycle. 

Hmm, that seems .. unlikely. You're saying that they used adiabatic expansion, resulting in exhaust so cold that it froze the machinery. So the concept was unworkable from even a technical viewpoint. I don't know for sure that that's wrong, but it's contrary to what I understood of the process on the basis of what I read on LightSail's web page and from a few e-mail exchanges with LightSail's founder, Danielle Fong.

My understanding is that they used a water spray injection on both the compression and expansion cycles. If the pressure tanks and the hot water reservoir were sufficiently insulated that they lost little heat between the compression and expansion phases, then the overall cycle would have been nearly isentropic. The expanded air would have exited at a temperature only a little cooler than when it entered. I'm pretty sure that LightSail had one or more working prototypes. At one point, I believe they had round trip efficiency number for a prototype posted on their web site.

Mark Howitt's picture
Mark Howitt on Nov 4, 2020

They tried to use similar water-spray technology in expanders, but had to get the heat into the water from somewhere. And there just isn't a "somewhere" producing sufficient such heat for a large plant. I said "would have frozen...", because they never tested a system at such scale.

The efficiency that they posted on their website was a theoretical 70% at large scale. They never built it at anything remotely resembling such scale.

You appear to have missed out that all three isothermal CAES companies (Lightsail, General Compression, SustainX) went bust because they couldn't make a scalable technology that works, so I don't understand how you can advocate their solution as better. Isothermal cannot work at scale for the reason I gave; adiabatic is the way forward. In some applications, diabatic is a viable solution: just as scalable as adiabatic.

Roger Arnold's picture
Roger Arnold on Nov 4, 2020

We're getting pretty far down in the weeds here. If I can find them, I'll send you the some thermodynamic calculations I ran years ago when I was looking at these issues. Or I'll try to retrieve that part of my brain from cold storage and recreate them.

For the record, I don't advocate for one approach as decisively better than the other. I regard both quasi-isothermal and adiabatic CAES as technically viable. Adiabatic is simpler in that it doesn't have to deal with issues around water spray injection. Probably less risk as well, for the same reason. But it does have the issue that high temperature heat stores are hard to insulate. Radiative heat transfer begins to dominate over conduction. Unless the store is large enough to exploit the square-cube scaling law for surface area to volume, it will be difficult to hold the heat for periods of weeks or months.

I don't know much about the history of General Compression or SustainX. In the end, though, most technology startups fail for the same general reason: failure to prove their technology to be decisively better than the incumbent competition. That could be due to unexpected and difficult technical problems encountered in product development. It's usually a lot more complicated than a plain "this just won't work".

That said, I'll grant that you're in a better position to know than what I am. I'll take your word that the problems these companies encountered with quasi-isothermal were intractable. 

Mark Howitt's picture
Mark Howitt on Nov 5, 2020

We've solved the thermal storage challenge with cheap, clean, off-the-shelf technology. And we have validations from Mitsubishi Power, Siemens, Arup, Mott MacDonald, Costain and others to prove it. But details are only available under non-disclosure agreement to businesses that would help us towards constructing our first, e.g. financiers, or manufacturers.

No need to send the calcs. I believe that they prove isothermal is the most energy-efficient way to compress air, because it is - it just doesn't consider the other half of the cycle.

Mark Howitt's picture

Thank Mark for the Post!

Energy Central contributors share their experience and insights for the benefit of other Members (like you). Please show them your appreciation by leaving a comment, 'liking' this post, or following this Member.

Get Published - Build a Following

The Energy Central Power Industry Network is based on one core idea - power industry professionals helping each other and advancing the industry by sharing and learning from each other.

If you have an experience or insight to share or have learned something from a conference or seminar, your peers and colleagues on Energy Central want to hear about it. It's also easy to share a link to an article you've liked or an industry resource that you think would be helpful.

                 Learn more about posting on Energy Central »