Energy storage (dull but important)

by John Q on February 3, 2014

OK, so energy storage isn’t the most exciting topic in the world, but it really matters. The problem of energy storage (or changes in energy use that make it unnecessary) is the biggest remaining obstacle to a transition to renewable energy. So, here are some observations, labelled for convenience and partly derived from this study by the US Department of Energy

(a) Any reversible energetic process represents a potential storage technology. Reversibility entails that some energy is stored (as potential or chemical energy) when the process goes one way, and released when it goes the other. Of course, the Second Law of Thermodynamics implies that we will always add entropy (that is, lose useful energy) in this process
(b) Any technical or social change that shifts the time at which energy is finally used replicates the effects of storage
(c)Energy storage is in much the same position as renewable electricity generation was, say, 15 years ago.
(d) There are a lot of potential approaches, most of which have been developed in niches where particular characteristics are required. For example, car batteries need to store a lot of energy for given weight, household batteries need to store energy for a long time and so on. The needs of a renewable-dominated electricity system are very different and will require substantial modifications of these technologies
(e) With one big exception, there is currently no price incentive, in most jurisdictions to use storage technologies and therefore none are used
(f) The big exception is off-peak hot water. Coal and nuclear systems generate baseload supply when it is not needed for consumption. Price incentives are used to encourage people to store the resulting excess energy in the form of hot water
(g) There’s no technological obstacle, given the availability of smart meters, to changing the timing of hot water systems to reflect actual availability of excess electricity rather than reflecting the assumptions of a coal-based system
(h) All of this applies to electric cars. Even ignoring the possibility of feeding power back into the grid, the economics of electric cars would be drastically improved if they could be charged using low-cost power in times of excess supply (in the case of solar PV, around midday when lots of cars are sitting in parking lots)
(i) Something I just found out from the DoE study: Electric car batteries are considered unfit for services when they fall to 80 per cent of their original charge capacity (recall that energy density is critical for car batteries). But they still have a long potential life as static storage devices. This enhances both the economics of electric cars (since the battery has resale value) and of storage (since the opportunity cost is zero)

Here’s an older post, with a really simple example of how the argument works, once you get away from the fixation on replicating the characteristics of a coal-fired system.



Ed Herdman 02.03.14 at 11:36 pm

Funny story – months ago I assumed that transmission losses were a lot higher than they really are. So there’s also a lot more flexibility, even if you’re generating energy 1000 miles from where it is actually used, than some people might think reasonable.

What are the upcoming energy storage technologies that are promising? The last 15 years of development in renewables (both technology and economically) have been astounding, and I already felt that batteries are dramatically improved over the past. I do read now and then about fuel cells making great progress recently but it seems a bit good to be true – new technologies have a habit of landing in your lap when you don’t expect it.

Also, about the problem of winter (a bit off the topic I know): Passivhaus needs to get more traction. This is in putting focus on treating the traditional “end point” of energy usage as a battery in itself. If you want to see a visual representation of some of the savings, just look at this:


The Temporary Name 02.03.14 at 11:40 pm


Joshua W. Burton 02.04.14 at 12:14 am

Yes, flow batteries @2 for the win. I’m extraordinarily proud to say that my daughter spent last summer working on the low-potential quinone in Roy Gordon’s lab (not the result that made it into Nature, but hey, she’s 19). With purely organic, plentiful and relatively nontoxic aqueous reagents, these systems have the, er, potential to solve the short-term storage problem completely, except in transportation where density matters.


The Temporary Name 02.04.14 at 12:19 am

Congrats Joshua.


Joshua W. Burton 02.04.14 at 12:24 am

If you live in a four-season climate, Prof. Gordon is also the reason you can afford low-emissivity windows. People think of the home heating problem as insulation (R-value), but a modern low-e window gains up to ten times as much heat on a sunny subzero day as the same area of insulated wall loses.


Joshua W. Burton 02.04.14 at 12:34 am

More about that here. Everybody knows about the Corning Museum of Glass, right? Best long day you’ll ever spend indoors in upstate New York, or two days if you care about both the art/archeology and the science. Less than an hour from Ithaca, if you’re ever visiting Cornell.


Matt 02.04.14 at 12:47 am

If you need to just shift demand profiles a few hours, thermal storage is excellent.

There’s already a commercial system that can do it for cooling. It’s pitched at getting cheap night-time grid electricity right now, but I could also imagine it used to buffer mid-day surpluses from rooftop solar for use later in the day, if net metering is technically or legally problematic in an area.

I haven’t seen one yet, but it seems like you could also use a hot water tank as a thermal reservoir for building heating if demand for hot water itself isn’t enough to absorb electrical surpluses. Just add an insulated water tank to a heat pump system and you get a good way to shift demand profiles in winter and in summer.

I like the quinone flow battery. I really hope it gets developed into something widely available. Other flow batteries fail if their chemical solutions mix, or require expensive metals for energy storage. The one thing I’d like to know that I haven’t seen from the press releases is how much degradation there is of the organic substrate over time. Does it form any solids or gases as side products that may complicate the mechanical design? How many charge/discharge cycles before the solution needs to be purified or replaced?


Happy Heyoka 02.04.14 at 1:20 am

Something I read just the other day:

ABB and Samsung have announced they will design and construct a hybrid Grid Energy Storage and Diesel Generation System (GESS) for Victoria’s SP AusNet.

Where do you locate the storage? How much load will it support and for what duration?

In what circumstances is it designed to be used? Who pays to build and maintain it?
Is there a business in just doing storage (I buy it off a solar farm and sell it at night) or do we require that intermittent producers “smooth” their output by adding storage?

Does an increase in “off-grid” houses result in “white-anting” of the distribution system?

How to reconcile the desire for uninterruptable power with safety (eg: islanding) ?
What control systems do we use? (There’s a whole career in that one alone).

So, not dull. Definitely technical, wonkish. Also the corner stone of any real solution…


Joshua W. Burton 02.04.14 at 1:24 am

Over 99.2% retention per cycle (Nature letter, page 199), and months at least. Remember, too, that you can recover all the breakdown products and reform them offline, so the losses only waste energy, not reagent. Also, remember that these are proof-of-concept numbers from kilogram samples handmade on the benchtop. At scale, it’s hard to see how it can get worse, and it’s likely to get better.


Joshua W. Burton 02.04.14 at 1:29 am

Quinone flow batteries vs. metals: it isn’t even a question of expense (and lifecycle toxicity). If you run the numbers, there just isn’t that much vanadium in the world, by a couple of orders of magnitude. But there are no fundamental obstacles to making AQDS and hydrogen bromide in million-tonne lots.


Chang 02.04.14 at 1:29 am

As long as we’re clear on one topic: using electricity to heat water is massively inefficient because you’re using energy that could be used to do work and just creating heat. A heat pump system is necessary store energy efficiently in the form of hot water, and this adds a great deal of complexity to any system. Lastly, changes in ambient temperature would probably work against such a system, cold when you’re storing energy, and hot when you’re extracting it. All the while, you’re losing energy through thermal cooling.


Happy Heyoka 02.04.14 at 1:53 am

Joshua, I find the interesting properties of flow batteries intriguing… the idea of moving about the electrolyte or using asymmetric arrangements of recharge and discharge cells for DC-DC power conversion.

I’m not across the chemistry enough to answer this: do I want a few hundred litres of this stuff in my back yard? Or is it best handled at a local utility level – eg: local water utilities regularly handle chlorine etc without incident.


Will Boisvert 02.04.14 at 2:06 am

@ John Quiggin:

“The economics of electric cars would be drastically improved if they could be charged using low-cost power in times of excess supply (in the case of solar PV, around midday when lots of cars are sitting in parking lots.”

Hmm. Electricity storage with car batteries would work a lot better with a low-carbon baseload generator like nuclear than with PV. Yeah, there’s a dip in driving at midday compared with rush hour, but there is still much more driving and electricity use at mid-day when solar PV is generating than at night when nuclear plants are still going strong. So it makes sense to store energy in auto batteries at night when cars and electricity are both in much less demand than at midday.

The key to efficient and economical energy storage is to store when demand is low and sell when demand is high. Nuclear complements that storage profile better than PV. And of course on cloudy days there will be virtually no PV storage period.

Dispatchable renewable technologies like hydro, geo and biomass also store well because storage yoked to those generators can reliably save up electricity during offpeak hours to sell during peak demand. But intermitten wind and solar are chaotically unreliable, so they don’t fit well with any kind of storage.

We’re seeing this now with pumped hydro in Germany. Pumped hydro is the main form of grid storage—your DOE document put it at 23 GW in the US, which is 95 percent of all US grid storage—and it’s always cooperated profitably with baseload generators. But the flood of solar in Germany is crushing the economics, because it overproduces in daytime hours when pumped hydro makes its money while generating no electricity to store during periods of low night-time demand. PH stations are starting to lose money, and will be cut their own slice of subsidies to stay in business (or be replaced by more carbon-powered generation).

Storage is a way of fitting electricity supply to variable load. That problem gets dramatically harder and costlier when intermittent wind and solar generators, whose outputs vary much more than the load itself, are introduced into the equation.


Matt 02.04.14 at 2:11 am

Ah, I found a free full PDF of the quinone battery article that I couldn’t find when it first came out. It looks like it still doesn’t match vanadium flow batteries on one really attractive property: leakage across compartments only wastes energy for vanadium, it doesn’t damage the chemistry of the system. According to the article AQDS is stable in the presence of bromine and HBr, but it sounds like you would still see capacity degradation from mixing until an external process re-purifies the materials for their respective compartments. If the side that is supposed to contain the quinone is only rated for corrosion resistance to dilute sulfuric acid, not hydrobromic, that could be another crossover concern since HBr is much more aggressive toward most metals. But, OK, these are wonky details; it sounds great and I really hope they can build a production-scale prototype.

I don’t think storage is yet cheap enough to make going off-grid cheaper than traditional distribution networks in any urban area. The medium term threat is people staying connected to the grid but drawing from it less, making the proportion of fixed costs higher for people who use the traditional system more heavily. To avoid underfunding distribution as rooftop solar becomes more popular, it’s probably better to make the fixed distribution infrastructure expense a separate billing item instead of folding it into the per-unit price of grid electrical consumption. Of course that fix may bring its own problems, like placing a proportionately higher burden on low-income, low-usage households.


Omega Centauri 02.04.14 at 2:14 am

Its probably boring for economists and philosophers, but for energy geeks, this stuff is exciting. Different minds are fascinated by different stuff.

Nearterm storage (as opposed to demand management -shifting the usage around via some combination of control systems, and changes to rate structures to incentivize compliance, which was mostly discussed above) is also coming along. Already California has passed regs to push for 1.3GW of storage by 2020. New York state, is also starting a similar, but smaller program. The biggest thing holding back the technology (IMHO) has been the lack of a viable business model to make storage pay. But opportunities are starting to emerge. At least for what could be termed frequency, and voltage regulation, which responds to powergrid needs in timespans of seconds to maybe a hour, looks viable in some markets. Today, Lithium Ion batteries are the main contender for this market. To cover day-night imbalances, or worse sunny/cloudy day imbalances will require different technologies from the short term stuff. But even voltage regulation can improve the ability of the grid to absorb higher levels of renewables.

For California, the big need is to cover the evening power spike (7-9PM) when solar isn’t producing anymore. I think in New York a bigger motivator is grid resilency during waether emergencies (hurrican Sandy).


Matt 02.04.14 at 2:42 am


Solar is considerably more predictable than wind. I scraped data from CAISO and ran some calculations for the month of January. Left column on each date is megawatt-hours of PV production, right is wind:

2014-01-01 18326 1012
2014-01-02 20441 698
2014-01-03 16721 4411
2014-01-04 15228 20086
2014-01-05 18207 4885
2014-01-06 17318 1389
2014-01-07 11109 18326
2014-01-08 17370 37052
2014-01-09 15611 53929
2014-01-10 18015 29893
2014-01-11 16878 27430
2014-01-12 13112 41398
2014-01-13 19644 9316
2014-01-14 19773 7601
2014-01-15 18286 4430
2014-01-16 21006 7091
2014-01-17 20806 1936
2014-01-18 20573 982
2014-01-19 13389 545
2014-01-20 20620 1628
2014-01-21 13296 1992
2014-01-22 18838 6176
2014-01-23 18601 17438
2014-01-24 9054 14577
2014-01-25 16816 2625
2014-01-26 14575 17289
2014-01-27 18938 36225
2014-01-28 18779 30685
2014-01-29 19964 36173
2014-01-30 11704 40001
2014-01-31 12918 44257

Standard deviation for PV in January is 3143, for wind it’s 15926. But there’s also more wind capacity installed; normalizing by peak value in each population, it’s 0.30 for wind and for solar it’s 0.15.

I’m working on similar scripts for German and Australian output, though so far I only know data sources for solar production, not wind.

As a practical matter, for planning purposes you’re ok with just a few minutes’ worth of buffering storage and a reasonably accurate 15-minute-interval forecast produced 12-24 hours in advance. I unfortunately don’t have any data handy on how much forecast error there is in PV and wind day-ahead modelling. If you look at e.g. the UK, , you can see that coal plants are already load following night vs. day and weekday vs. weekend. Recent research also concludes that cycling fossil plants up and down in response to renewable output loses only a small portion of the expected fuel savings from startup inefficiency. The main thing for integrating renewables, then, is producing good near-future forecasts and building enough fast-reacting storage (and/or demand response) to cover residual forecast error. You may still have the fossil plants around but you can reduce how much fuel they’re burning and CO2 they’re emitting.


Joshua W. Burton 02.04.14 at 2:45 am

I’m not across the chemistry enough to answer this: do I want a few hundred litres of this stuff in my back yard? Or is it best handled at a local utility level – eg: local water utilities regularly handle chlorine etc without incident.

Well, it’s not explosive or particularly toxic; it’s also three to five times bulkier and heavier than the equivalent storage capacity in lead-acid cells. Probably the scaling of pumps, airtight seals and closed-cycle reprocessing will favor tankcar size and up: either a 100k liter tank under each windmill, or a 10M liter tank farm at the big transformers.

A useful rule of thumb is that if the power company doesn’t care enough about your inductive load to encourage you to install a capacitor yard (by making you pay commercial rates for complex V dot I instead of residential real-phase VI resistive power), they shouldn’t mind running your meter backwards and buying your home-generated alternative power at retail cost, storing it centrally if they can’t level the load. If they are losing nontrivial money from electrons you’re sloshing back and forth on their wires, their first line of defense is to balance your reactances with a capacitor yard, and only after that should they consider nudging you to store power on-site.


Collin Street 02.04.14 at 3:07 am

To avoid underfunding distribution as rooftop solar becomes more popular, it’s probably better to make the fixed distribution infrastructure expense a separate billing item instead of folding it into the per-unit price of grid electrical consumption. Of course that fix may bring its own problems, like placing a proportionately higher burden on low-income, low-usage households.

Or you could fund it out of consolidated revenue / general taxes like some other bits of infrastructure, just bill for the power consumed.


Happy Heyoka 02.04.14 at 3:25 am

either a 100k liter tank under each windmill, or a 10M liter tank farm at the big transformers

Well, given shipping containers are in the range of 30-80k litres, that’s not hard.
I recently toured the Hepburn Community Wind Farm; all the grid related gear is in a couple of shipping container sized boxes marked “ABB”.


Omega Centauri 02.04.14 at 3:48 am

Some storage slutions will scale down well, and some won’t. LiIon scales down well enough that some will end up in the home. Flow batteries, probably will be larger nodes on the grid, maybe at the substation level or larger.
Predictability of PV should be pretty high. Geographic distribution helps a lot here, clouds don’t instantly appear at the same time miles apart, so if some of your PV plants are surprised, others won’t be -or at least the timing of the surprise will be different. The same thing applies to wind.

The solar that you read on the CAISO site, is only about 2/3rds of the state’s PV, the rest is distributed on hundreds of thousands of roofs. In California rooftop solar does not count as renewable, but as demand reduction. The state’s grid is actually a lot greener than it appears. Much of the utility scale solar is concentrated in the sunny desert parts in the south of the state, much of the rooftop PV is in the greater bay area, which is usually a day ahead of the deserts cloudwise. So geographic PV distribution in California is actually better than what you see on the CAISO site.


Charlie 02.04.14 at 4:29 am

“Energy storage is in much the same position as renewable electricity generation was, say, 15 years ago.”
Disagree, the technology of using storing energy for electricity is over 100 years old and very mature. There’s probably still some efficiency gains that can be made, but unless a miracle happens, renewables are not going to get anywhere near the energy storage that fossil fuels offers. It’s a major stumbling block for renewable energy, and we need a *massive*, ww2-style investment in this area if we’re going to beat climate change.


Matt 02.04.14 at 5:04 am


I think there is a fruitful possible parallel between solar PV generation and battery storage. PV technology has not changed a lot on the surface. 15 years ago you could buy modules with the same basic technology (crystalline silicon), conversion efficiency, and form factor as you might install on a rooftop today. But the module cost several times as much 15 years ago. What has changed in the mean time is an enormous increase in production scale, with corresponding cost reductions, and a thousand little improvements at every level of the production chain, most of which would not make news on their own.

I think something similar may be possible with lithium iron phosphate batteries. Lithium, iron, and phosphates are fairly abundant and inexpensive, even after they’ve been purified to battery-grade. Turning those cheap raw materials into batteries is currently expensive; the finished battery costs something like 80 times as much as the purified but bulk-form mineral inputs. Silicon based PV modules were once in a similar position, but due to the improvements mentioned above the manufacturing cost is now in the neighborhood of 8 times as much as the purified mineral inputs (solar grade silicon, silver or copper, glass, aluminum, and plastic). I know relatively little about battery manufacturing, so I don’t know if a drastic cost reduction is possible following the same incentives-and-buildout model shown by PV. But the possible parallel seems provocative to me.

For a long time (and it still happens now) people were trying to make PV cheaper by pursuing big technological leaps: thin-film devices based on exotic metals, printable organic cells, proton beam wafering, ribbon silicon. But thin film cells are a smaller part of the market now than 10 years ago, and those other technologies are dead for the foreseeable future. Slow and steady (and big) won the race for crystalline silicon.


Thomas 02.04.14 at 7:39 am

@Matt (16): There are lots of graphs for Germany at

The source of the data is the EEX’s transparency platform, but I can’t figure out how to download data from there for more than one day at a time.


Tim Worstall 02.04.14 at 8:36 am

“If you run the numbers, there just isn’t that much vanadium in the world, by a couple of orders of magnitude.”

Not entirely convinced. There’s around 20 million billion tonnes of V in the Earth’s lithosphere. Sure, reserves are only 14 million tonnes and resources 63 million, but they’re not anything like, in fact entirely unconnected to, how much is actually available to us.

As to the point of the post, energy storage, I tend to think that it’s going to be fuel cells. Admittedly, this belief is likely because this is where I’ve bet my own money in business. One type of fuel cell (like the Bloom Box) uses the metal that I happen to deal in, the one I’ve spent some years working out how to extract and process. So clearly and obviously I’m highly biased here.

Solar to electrolise water and we then store the H2 until we want to run it back through the fuel cell again and use the resultant electricity. This would have to be a local system, given the difficulty of storing or moving H2 around. But conversion to other things isn’t all that hard: methane for example, which can be piped through the normal gas networks.

This is obviously an inefficient system: there are inevitable losses at each conversion. But that’s not quite a killer for such a system. It depends only on how cheap solar cells get. And given that they’re governed by something akin to Moore’s Law I would bet that there’s another order of magnitude reduction in cost possible (we’re currently seeing a 20% pa reduction in costs). And we’ve most certainly no shortage of sunlight to collect.

Worth noting also that fuel cells themselves, at least the type that I’m thinking of (SOFCs) are also governed by something akin to Moore’s Law. They are about tracing a circuit on a substrate. The current cost of those boxes could also come down by an order of magnitude (I’ll leave out the boring bits about how but one manufacturer was, at least they were two years ago, hand painting the substrates when something like thin film vapour deposition would clearly reduce materials costs radically).

I wouldn’t say that this will happen, only that it could. If solar PV comes in at a capital cost of 10 cents per W as opposed to the around $1 now then conversion losses would be a near irrelevance. And my best guess (and it is a guess) is that the solar and fuel cell prices will be low enough to make this a very cheap system indeed in 15 or so years.


Matt 02.04.14 at 9:46 am


My German PV-data scraper is working now. It’s pulling from, the same source that powers

It gives data in 15 minute intervals for all of Germany and broken down by PLZ code. The source you linked to is nice because it includes wind, but graphs embedded in PDFs are pretty much a worst-case scenario when it comes to extracting numerical data. Did I overlook tabular sources there – CSV, XML, XLS? No doubt I might have already found a better data source if I actually spoke German…

@Tim: What are the advantages of distributed electrolysis-plus-fuel-cells vs. distributed batteries? I see advantages for synthetic methane or hydrogen if you want to store mammoth quantities for seasonal energy shifting, export, or use as chemical feedstock, but it seems doubtful that anyone is going to store months’ worth of hydrogen or methane on-site at an office building or home. For handling a day or two of smoothing it seems like batteries have considerable advantages in round-trip efficiency and simplicity. It’s not just the fuel cell I’m thinking of, but also electrolyzer, compressor, high pressure storage, and (if you’re doing methane) CO2 concentrator and methanation unit.


Tim Worstall 02.04.14 at 10:25 am

“What are the advantages of distributed electrolysis-plus-fuel-cells vs. distributed batteries?”

Essentially, I think that fuel cells are going to be cheaper. There’s just nothing in them that is inherently expensive. They’re basically a zirconia plate with a thin layer of rare earths.

There are patent costs currently and the manufacturing of them is incredibly inefficient in both process and use of raw materials. But these are exactly the sorts of problems that tend to get solved over time. I just think they’re going to end up cheaper than using a whole bunch of lead/vanadium/whatever.

I’ll agree that I’ve not thought it through in detail but I can’t see much in there that would make it impossible to have a household running solar cell/fuel cell system for under $10k in a decade or so’s time.


Happy Heyoka 02.04.14 at 10:38 am


Not sure that it’s necessarily going be one storage solution or another.
I’ve done some work on compressed air storage, and while it’s almost instantly dispatchable, it’s not instant – so in small scale systems it is always going require capacitors or batteries to handle that instantaneous load and short term accumulation while making compressed air.
Hybrid and/or redundant setups make sense in other situations too.

Also, for Australian wind, insolation etc, try the Bureau of Meteorology… they have a fair amount of data available for free; support json, csv etc.


Dragon-King Wangchuck 02.04.14 at 1:06 pm

Electricity is a weird “market”. Fluctuating demand levels must be met instantaneously by a system that has no warehousing on a 24-7 basis. It’s quite a lot different from just cranking out widgets.

Demand response and load shifting can do a lot of the same things that energy storage does, but there’s a very significant difference between the two. The more you do energy storage then the cheaper it gets as you slide down the cost curve. Changing the way people use electricity is the opposite. There’s a bunch of low hanging fruit applications that are cheap to do (like doing your laundry and dishwashering off-peak), but once you’ve harvested those opportunities, each additional amount of demand becomes harder. It’s quite similar to conservation and energy efficiency in this way.

Regarding price incentives for storage – it’s actually worse than zero incentives. A standalone energy storage facility would actually be penalized. Most jurisdictions have uplift and transmission costs which are levied per unit energy delivered. Energy that goes into storage for use at a later point in time would have these uplifts charged to it twice when it got to the end user.


The Raven 02.04.14 at 2:43 pm

Over to the Joint Center for Energy Storage Research (yes!—JCESR) which is, for some unimaginable reason (kraw), located at Argonne Labs near Chicago.

Also to the (US) National Renewable Energy Laboratory’s (NREL) Energy Storage team, Lawrence Berkeley National Laboratory’s Energy Storage and Distributed Resources department and Amory Lovins Rocky Mountain Institute, which has been engaged with these issues for decades.


The Raven 02.04.14 at 2:47 pm

(While the gnomes of the Crooked Timber pile go through my previous linky post, here’s a general remark.)

I think it’s too early to pick winners and losers in these technologies, by the way. As usual in such cases it’s likely that the technically best technologies will not be the winners; these things depend on unpredictable social and economic contingencies.


JG 02.04.14 at 3:17 pm

There have been new cool ideas for storage that developed and unfortunately stayed in the lab for at least 20 years. I was CEO of one at Harvard in the lat ’90’s. I’d love to hear you economics wonks explain what the suite of disincentives for current behavior and incentives for changed behavior (and investment) would be to produce fundamental change. Also please remember that the many VCs who focused on renewables and storage have taken serious cold water baths and are mostly now investing in the newest cool interface.



Dragon-King Wangchuck 02.04.14 at 4:00 pm

Another thing to consider about energy storage is that it shifts energy in both time and space. Being able to use off-peak generation to meet on-peak demand is amazing and all, but we shouldn’t forget about the locational effects it can provide.

When load centres are geographically situated at a distance from generators, energy storage technology can move power from the big generator closer to the load during off peak, alleviating the need for major transmission upgrades. This effect is scalable downwards as well. A growing load centre can defer transmission line and distribution network upgrades by strategically placing energy storage units throughout the system. Being required to meet peak demand everywhere and all the time means under utilized infrastructure, so shaving the peak with some well placed batteries should be very useful.

One other thing to consider – when we talk about “Energy Storage” we are referring to a pretty wide range of products and technologies. Normally electrochemical batteries is what we think of, with maybe some fancy new high tech alternatives. And yet, the overwhelming majority of MW and MWh operating energy storage is pumped hydro.

What technology you might want for diurnal or even weekly power shifting is not necessarily going to be the same thing you would want for seasonal storage or renewables integration and voltage support. Focusing on technologies is fun and all, but I think what would really get the ball rolling is better definitions of the problems the electricity systems of the world face and then quantifying how much a solution to those problems would be worth.


Omega Centauri 02.04.14 at 4:57 pm

I would second what Raven said in30. Most of the current hot solutions, are best thought of as irons in the fire. Its difficult which ones will become part of the longterm solution, and which ones just also-rans.

I’ve heard Tim’s argument about batteries, “been around a century, didn’t work then, won’t work now” before. Sure there was effort soent back then, especially by the likes of Edison. But the scientific/engineering equiment and knowledge back then can properly be considered to be possitively stone-aged compared to whats available now. Many technologies are inveted too-soon, and were found unworkable simply because the technical support structure didn’t exist.


Mario 02.04.14 at 5:45 pm

As a chronic pessimist, I will also point out that local storage and generation imply complex nonlinear interactions between large numbers of all sorts of megawatt-rated things, run by all sorts of people. It’s bound to be interesting and, er, flashy.

Interesting times ahead.


Dingbat 02.04.14 at 6:35 pm

This is an excellent article from 2011 on electricity forecasting and production smoothing in the context of hydroelectric, which (as of 2011, and it seems still) is a huge load-balancer. It gives a very good sense of the scale of the problem and our current solution to it.


Michael Cain 02.04.14 at 6:43 pm

@Mario I would have said “interesting and… dark.” There’s a lot of gear already deployed whose sole purpose is to disconnect things when it gets too interesting, with a history of working quite well, eg the Northeast in 2003 and the Southwest in 2011. Not much flashy, but plenty of dark.

Regarding the useful comments others have made on pumped hydro, the problem at least in the US is that too much of the population is too far from where pumped hydro has room to expand. The Western Interconnect has a reasonable opportunity: deep narrow canyons not too far from either the demand centers or the best of the more-intermittent renewables. The hunt for flow batteries or hydrogen or compressed air storage is largely to find solutions for the Eastern Interconnect.


Thomas 02.04.14 at 10:21 pm

@Matt (25): The source of their data is the EEX’s transparency platform ( You can download data from there, but only one day at a time. There’s a captcha on the site but it turns out it is verified client-side. The URL format for wind in de is,xlsday,DD.MM.YYYY/7,wind/timepoint/YYYY-MM-DD/-,-,-/view-page,/0/4405

You’re probably in violation of their TOS though…


john c. halasz 02.04.14 at 11:01 pm


Speaking from VT, for New England, there’s Quebec and Labrador.


Matt 02.04.14 at 11:46 pm

Thomas, thanks, I was able to use that to get wind data back to October 2009. Will post later comparing winter time wind and PV variability in Germany like I did for California above.


Eli Rabett 02.05.14 at 4:42 am

The issue is EITHER energy storage or energy transmission. High efficiency transmission serves the same purpose


Omega Centauri 02.05.14 at 5:33 am

Eli, storage and transmission are rather imperfectly interchangeable. Unless transmission spanned the planet -so the sun is always shining somewhere you can get power from, and you don’t have to worry about winter because you are getting juice from the sothern hemisphere. Last I looked, the US only spanned three time zones.

Good long distance transmission certainly removes some of the pressure for storage, but any concievable transmission network won’t eliminate the need.


Tim Worstall 02.05.14 at 9:41 am

“I’ve heard Tim’s argument about batteries, “been around a century, didn’t work then, won’t work now” before. Sure there was effort soent back then, especially by the likes of Edison. But the scientific/engineering equiment and knowledge back then can properly be considered to be possitively stone-aged compared to whats available now. Many technologies are inveted too-soon, and were found unworkable simply because the technical support structure didn’t exist.”

That’s not an argument I’m making at all. Indeed, entirely the opposite. Solid oxide fuel cells have been around for 150 years after all.


Haftime 02.05.14 at 10:05 am

I think that argument was Charlie’s. I think arguing for stagnation in battery technology for a century is a bit misleading when Li ion batteries are at most 30 years old.

Tim – what kind of efficiencies do you expect for SOFC – my impression was that losses were relatively large if you wanted to get reasonable power out? Also, I thought you needed fancy Pt or Ir containing electrodes to split the H2? Is this mitigated by the high running T? (If I can ask a final question in my interrogation, what are the materials you think with be used? Sorry, my fuel cell knowledge is p. rusty).


Collin Street 02.05.14 at 10:43 am

Sort of semi-related, but… what effect will a rise in the fraction of people living in multiple-dwelling buildings have on distributed PV construction, gien you don’t have the rather nice owner/occupier/electricity-consumer synergies that have been driving PV construction locally?

Thoughts, anyone? I mean, if you rip down a house and put up some strata-title flats, the land still supports the construction of the same PV capacity, it’s just I don’t think the interests align quite as strongly to favour putting it there.


Omega Centauri 02.05.14 at 2:56 pm

I have seen local condos with PV systems on the roof. I’m not sure how the residents are involved, I would guess via PPAs (power purchase agreements). This is not much different from having third party ownership PV on a residence, the system is owned and paid for by the third party, and the homeowner “buys” the power at a pre-agreed price. In areas with a lot on sun and high retail power costs the customer saves money.


Dragon-King Wangchuck 02.05.14 at 4:22 pm

Why wouldn’t the condo corporation own the PV system? I guess it depends on the specifics of your market, but in Ontario I have seen both third party ownership of the PV system with the condo corporation receiving revenue from a roof lease agreement and condo corporation ownership of the facility. We have a Feed In Tariff program though.

There’s also a premium for condos that can advertise themselves as “green” even if a third party owns and operates the PV and the PPA counterparty contractually claims all the monetizable environmental benefits (i.e. RECs, etc.).

One advantage of condos over single family homes is having maintenance staff on site. While they may not be trained electricians, they can keep soiling losses under control as well as monitor the system to report any significant malfunctions.


Ragweed 02.05.14 at 10:50 pm

Condo’s going green are pretty straightforward, as the unit owners are owners and usually have some semi long-term stake in the building, as well as a say in the condo owners association, et al.

The much bigger issue is with rental units, and that is one where the incentives run counter to more than just solar application. In the US at least, in most rental units the tenant pays the utility bills. That means the owner has not incentive to improve energy efficiency in most applications (maybe hallway lighting and shared laundry, but sometimes not even then). So no reason to, say, insulate or install more efficient windows. Tenants, on the other hand, are generally restricted from making modifications, and since they may not be able to stay more than a year or so, have no incentive to make any sort of major investment in the unit. So at best you get some more efficient lightbulbs.

There is some market advantage for “Built green” and the like, and in some markets building owners can use energy efficiency as a selling point, but the market incentives themselves are not very strong. It is one reason that carbon pricing alone is not enough – much of the improved energy efficiency of multi-family comes from building codes and requirements for new construction rather than market effects.

For Solar, how the incentives stack up depends on how the energy can be used. If it can be sold to the utility for a reasonable amount, then an apartment owner may see it as a source of added revenue and make the investment. If it would primarily offset electricity costs for the tenants, less so.


hix 02.05.14 at 10:56 pm

On the conventional liion battery technology cost side, they seem to have followed a similar price path as solar on the long term, arround 7% cheaper each year so far. Long distance grid technology had no such price path. Thus odds are good, its going to be a lot cheaper to stay more local. Either way, i dont think running a grid with 100% renewables will be an important topic anytime soon. The climate will survive 20% natural gas.


Eli Rabett 02.06.14 at 4:36 am

Omega Centauri, transmission systems can span a useful portion of the Earth. If nothing else energy demand at night is much lower than during the day.


derrida derider 02.06.14 at 5:06 am

hix is right – the issues around demand matching will always be far more difficult for a fully renewable system than for a partly renewable one. But getting the climate under control does not require fully renewable systems, just systems that spew out less CO2 than the current ones.

Good old fashioned supplementary natural gas turbines can do a lot of the work here, as they increasingly do in coal-based systems anyway. One day in the distant future, of course, we will run out of affordable natural gas but sufficient unto the day be the evils thereof …

I think we should distinguish our motives a bit better here too. Lets not mix the “small is beautiful” or the “smash capitalism” agendas with the climate control one. If getting the climate under control means more, not less. centralisation that might be unfortunate – but we shouldn’t hesitate to do it anyway. Let’s see where the technology takes us.


Martin Bento 02.06.14 at 8:14 am

I don’t have the detailed knowledge of this stuff that some others here have, but I wonder something. I’m hearing a conventional wisdom to stay away from thin-film solar (for example) because a lot of companies have put a lot of money into research and developing facilities, and the stuff basically works, but was not economically competitive for them. Now those companies are mostly dead or dying. Sounds like it might be a good time to go in, though, because those patents and facilities should now be available for what the market thinks they’re worth, which is probably much less than they cost to create. And the SV VC community is very trendy and tends to overreact to earlier losses, as they did circa 2000. The market may have an irrationally low estimation.

Likewise, there may ultimately be a difference between failed companies and failed technologies. All this work is being done, and all this money invested, without knowing what ultimately will be useful. Some things may require the early investors to take the bath to make them economical.


Niall McAuley 02.06.14 at 9:24 am

derrida derider writes: But getting the climate under control does not require fully renewable systems, just systems that spew out less CO2 than the current ones.

I was under the impression that most climate scientists think we are already screwed, and that a reduction in the rate we add CO2 to the atmosphere will not save us, wikipedia summary at Avoiding dangerous climate change

I’m not suggesting that spewing out less CO2 is a bad idea, just that it won’t stop catastrophic climate change at this stage.


Pete 02.06.14 at 10:37 am

@Martin Bento: thin-film cells are only viable if silicon purification is too expensive, which is no longer the case. It’s also less efficient than monocrystalline wafers.‎ has a good overview of the cost question.

There are plenty of interesting but not yet commercial technologies for either making the cells *very* cheaply through printing processes, or using titanium dioxide (ubiquitous constituent of white paint). The next cost question is “balance of system”: inverters, permits, labour to fit it to a roof.


john c. halasz 02.06.14 at 12:54 pm

@50 is just completely delusional.


Dragon-King Wangchuck 02.06.14 at 1:49 pm

NREL has a report on PV non-hardware costs. Soft costs already exceed hardware costs.

There’s probably a number of reasons why financing is so expensive. Lending directly to homeowners carries a significant amount of development risk and credit risk. Seasonal generation means monthly revenues fluctuate wildly (although predictably) which wreaks havoc on debt service coverage ratios. With residential units, loan sizes are pretty small and a lot of jurisdictions have not reached the critical mass of uptake to enable programmatic approaches to financing. Plus bankers. If they can squeeze a bit more juice out of it, they will.

“Green mortgages” for energy efficiency applications is probably a good model for enabling small scale PV installations, but it’ll be hard to work out. Every jurisdiction has it’s own way to pay for solar power.


Omega Centauri 02.06.14 at 3:01 pm

No. Slowing emission rate will only slow the descent towards a hellish climate, not stop it. While reducing is probably the best we will do during my lifetime, the goal has to be to ramp those net emissions to zero (or preferably negative something). Zero or negative doesn’t mean we can’t have some emissions somewhere, but that they must be more than offset by some sort of long term sequestration. The later would probably be a combination of biochar and enhanced silicate weathering, but I doubt it will pull down CO2 at even ten percent of the current emissions rate.

But, you are right about priorities with regard to centralisation. Opposing say utility scale PV and wind, because we don’t like the ownership model is harmful to the future climate. We need all scales and ownership models to be part of the solution.


Martin Bento 02.06.14 at 4:34 pm

Pete, thanks for the info. I think the general point stands though. Company failures may make a lot of technology ultimately available for much less than development cost, which could end up being an important component of economic viability.


reason 02.06.14 at 4:51 pm

Insulated houses are a good and important energy storage technology, and in some places, insulating a house is subsidised.


Omega Centauri 02.06.14 at 6:42 pm

Greentech Media just put out a report claiming the (annual) commerical market for energy storage will be 720MW by 2020.


Haftime 02.07.14 at 12:16 am

Pete, Martin, there’ve been some interesting (imo) developments in the fundamentals of thin film PV in the past year or two:

Caveats: efficiency still low compared to c-Si (so far up to 15%), contains lead. However, if you’re willing to extrapolate it looks like there could be a competitor, especially in specialty applications (e.g. windows, flexible substrates).


Matt 02.07.14 at 2:40 am

Now the German renewable output data:

2014-01-01 28567 212694
2014-01-02 12903 306620
2014-01-03 21989 327970
2014-01-04 15375 268350
2014-01-05 18950 169385
2014-01-06 22495 364281
2014-01-07 43047 362007
2014-01-08 31898 289877
2014-01-09 19270 414233
2014-01-10 28180 383544
2014-01-11 22877 297341
2014-01-12 44226 249764
2014-01-13 18194 125435
2014-01-14 17077 33054
2014-01-15 26249 80502
2014-01-16 13267 170833
2014-01-17 21168 122342
2014-01-18 34486 152466
2014-01-19 18541 304725
2014-01-20 5152 82538
2014-01-21 5052 15831
2014-01-22 11742 57052
2014-01-23 12264 122028
2014-01-24 8503 107496
2014-01-25 18026 137512
2014-01-26 14036 180956
2014-01-27 22265 185069
2014-01-28 37389 154062
2014-01-29 21374 211639
2014-01-30 38349 167356
2014-01-31 45570 107257

Again the left column is daily megawatt hours of PV production and right is wind.
Standard deviation for wind is 106760 and for PV is 10845. Normalizing standard deviation to observed peak in each population, for PV it’s 0.24 and for wind it’s 0.26. It appears that at least in January Germany experiences substantially larger daily variations in PV output than California, on top of having a more unfavorable latitude for winter time generation. There are in fact days in January where Germany produces less PV electricity than California, despite having a monitored nameplate capacity nearly 10 times as great. Germany also has higher winter-time electrical demand peaks than in summer.

I am grateful that Germany kick-started the deployment of PV on large scale but it seems like one of the most challenging locations possible for the technology. It’s too bad that Australia, Taiwan, or Chile couldn’t have been the first to attempt a solar-heavy Energiewende. A lot of criticisms of solar power are tied to difficulties specific to Germany, but most of the world’s population lives at less extreme latitudes.


derrida derider 02.07.14 at 2:45 am

There’s a big difference between being screwed and being really screwed.

Getting emissions reduced makes the difference between (say) a 3 degree increase and a 6 degree one. A 3 degree one is something you’d certainly avoid if you could (and, yes, we no longer realistically can – that’s actually part of my point) but a 6 degree one is civilisation-ending stuff.

It is certainly not “delusional” to seek the achievable rather than the utopian; this is an issue where daydreams and nightmares alike can cost us big. Bend your wish to your judgement, not the other way around. I say make a cool estimate on what is politically achievable (that is, achievable at relatively small economic cost) and go hard as you can for that. Forget the “now wouldn’t it be nice if we could just force everyone in the whole world to radically reconfigure their lifestyle so they use only a tenth as much energy” dream because however pleasant it is but a dream.


john c. halasz 02.07.14 at 3:03 am


Your economics, your engineering specs, your science and your politics are all wrong. There’s nothing “utopian” about that.


Omega Centauri 02.07.14 at 3:11 am

Only getting emissions down, but not stopping them completely means we will sonn enough blow past 6C, it will just take longer to get there. Unless you only care about 2050 or 2100 -but but 2200 or 2300.


Omega Centauri 02.07.14 at 3:15 am

Matt. January 2014 was highly anomalous for California. Great for solar power, not so great for water. December and January are usually very poor PV production months, January 2014 was a (excepting crazy climate change) once in a hundred year event.


Matt 02.07.14 at 3:37 am

China’s CO2 emissions are now greater than the EU, USA, Canada, and Australia combined. India has plans that would take it beyond the USA on emissions by decade’s end; the only reason it may emit less is because endemic dysfunction has impaired the expansion of coal extraction and power generation just like every other governmental plan. In short, it looks like the planet is screwed on climate even if everyone in the OECD gets serious about emissions.

Since a global dynamic of cooperative emissions reduction does not appear to be on the table in the next decade, I have some hope that an an alternative oppositional approach might work. If you’re in a nation that has committed to curb emissions, why should trade still flow freely with nations where emissions are going up 7% every year? It’s just shifting coal use to other parts of the world if manufacturing can relocate to dodge the costs of cleaner power. An oppositional approach based on tariffs penalizing use of dirty energy could also find support among domestic workers since dirty energy is strongly correlated with low wages. If you’re really lucky, the penalized nations will retaliate with trade barriers of their own out of spite, thus further slowing emissions. For example, Australia puts tariffs on Chinese manufactures, and China puts tariffs on Australian coal and iron ore in return — win/win for the climate!


Matt 02.07.14 at 4:30 am

Omega Centauri,

California in each January of 2013 and 2012 also had days where its solar output was higher than e.g. Germany on January 20 and 21 of 2014. But I’m actually more interested in daily variability than total output. If Germany were even further north but cloudless then PV would be a more predictable source of winter power.

Older CAISO data sets report solar thermal and PV together, so I’m going to combine them in newer sets too for consistency. The number I’m reporting in each case is standard deviation normalized by highest daily output observed in the month.

January 2014: CA solar: 0.15 CA wind: 0.30 German solar: 0.24 German wind: 0.26
January 2013: CA solar: 0.21 CA wind: 0.30 German solar: 0.23 German wind: 0.26
January 2012: CA solar: 0.17 CA wind: 0.27 German solar: 0.29 German wind: 0.28
January 2011: CA solar: 0.16 CA wind: 0.28 German solar: 0.24 German wind: 0.29

It looks to me like 2014 was unexceptional for solar power variability in California in January. 2012 and 2011 were very similar. In January wind is always more variable than solar in California. Wind and solar are much closer in variability in Germany in January, but solar still had lower variability than wind in 3 out of 4 years.

Germany and California really aren’t great locations for onshore wind. I don’t have the necessary data to hand, but I am pretty sure that wind power in Texas would show lower daily variability than Germany or California as well as greater annual capacity factor.


Happy Heyoka 02.07.14 at 4:34 am

@derrida derider

It is certainly not “delusional” to seek the achievable rather than the utopian; this is an issue where daydreams and nightmares alike can cost us big.

True, a few people have not “done the math” to realise that there is no low hanging fruit in low-emissions energy production.
Those people pretty much balance out the “other side” who haven’t looked at the math that says we’re screwed in the BAU scenarios (which, IMHO, includes holding off until all the possible problems are neatly tied up in a bow).

There is much inertia in billion dollar infrastructure projects… I want to see them happen too. Until then we have to rely on “holding actions” to shave off as much GHG production as we can, as early as we can.

If you can get a million people to spend $10k for some storage on top of their existing solar installation, you can start shutting down gigawatt sized slabs of coal fired power. $10k is not a huge impost (~3% of your house) and many people will do that just because it will help. Even more will if there’s money in it not too far down the track.
(see previous discussion as to how to provoke the housing/construction to get higher efficiency, solar equipped housing as a starting point)

If you can guarantee that your 10MW solar or wind plant could deliver today’s production tomorrow because you have storage, then you’re in a better position to sell at a higher price or get better terms on your contracts, and reduce the payback time for your investment.
Again, this is a ~$50m level of investment; we can do thousands of those a year with much less red tape and, co-incidentally, mothball another gigawatt slab of coal fired generation.

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