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In the earlier post I summarized my estimates on the limits to capacity utilization if production is done either with wind or solar power.  Here I will (over)think implication a bit further.  mthOn their own wind and solar power implied strong restrictions on achievable utilization rates. Overbuilding generation capacity (and associated distribution system) could increase utilization rates, but at the expense of ever increasing amount of wasted power and underutilized power lines. Storage could also help, but smoothing out the production profile would require large amount of underutilized storage capacity. There doesn’t seem to be away around this. Low capacity factor of variable power source has cascading effects elsewhere. If not fixed capacity utilization of end users would be strongly constrained and most likely too low to enable profitable business. On the other hand attempts to fix the problem would imply underutilized generators, power lines, and/or storage. Technical developments will not change this since the problem is not due to specific technology or costs.  Are there ways around these problems? Of course…

If you are planning to invest in a new plant producing for example solar panels and you find production to be unprofitable with utilizations rates implied by solar power, your first choice is simply not to invest. If economic preconditions do not exist, production never materializes even if we might find such production desirable or even critically important. Production would either not happen or move to a place where higher utilization rates are possible. Various shades of gray might also exists as they do today especially in the developing world. If production process is such that you could for example store some parts for later use, it might be possible to outsource only those phases which require reliable power elsewhere. Of course, this still opens up possibilities for those not saddled with the same constraints.

Another option is not to rely solely on variable renewables, but to have a fleet of dispatchable generators delivering the power services variable renewables cannot deliver. Today this most likely implies burning fossil fuels, but in principle hydro and nuclear power would work as well. This again implies overbuilding infrastructure and is unlikely to be economically optimal. However this fundamental reliance on existing infrastructure is the order of the day in the developed world.

Visions where variable renewables dominate are aspirational marketing material while on the ground unholy alliance seems to have quietly developed between many renewable and fossil fuel lobbyists. Cozy reliance on fossil fuels enables somewhat more variable renewables to be built before technical limitations become apparent. Supporting this modest buildup (with public money) buys fossil fuel industry social licence as well as removes long term threat of actual decarbonization. Petty about the climate, but the constituency for whom this is actually a priority is weak.  This is welcome also for many politicians who are only too happy to project an appearance of activity (at relatively low cost) while their policies imply changes which have a marginal impact on the actual problem. This relates to deep decarbonization in a same way as “champagne socialism” relates to revolution of the proletariat.

I recently read a very interesting book “Fossil Capital” by Andreas Malm on the history of industrial revolution in the United Kingdom. (Note: book is only worth reading until chapter 12. There the author got tired of thinking.)  Malm focused on the question of why coal and steam engine won over water power in the early decades of the 19th century. Remarkably coal did not win because water resource would have been insufficient. There was still plenty of untapped potential in the UK. Also coal did not win because it was cheaper. In fact, mechanical power from steam engines was more costly and many were of the opinion that it was also of worse quality. So what happened?

There were many overlapping reasons. For example, factories followed labour to the cities. In the early 19th century it was already clear from the demographics that labour was to be found in the cities. Water power was dispersed and getting meek labour to run the machines in the middle of nowhere was harder. In fact, owners of water powered factories were relatively more dependent on the apprenticeship system providing them with, what can apparently with some justification be called,  slave (child) labour. Water power was also more variable than steam, which made it even more important to have well behaved labour that would be willing to work long and irregular hours.

However, it turned out labour did not think their position was optimal (go figure) and started to make noise. This resulted in legal (and actually enforced) restrictions on working hours and gradual improvement on workers position. (It also induced technological change that made large number of especially troublesome workers redundant, but let us not talk about that here.) Owners did not of course like these limitations and lobbied against them, but relatively speaking those using steam found it easier to adapt. They could live with the shorter and more regular working week since reliable power could enable high productivity during working hours. Coal became the backbone of british industrial might and the road was opened for more broadly shared economic growth.

So can we learn something from this? I think we can since economic and social arguments for why coal won have not disappeared. If you listen to todays renewables promotion, you will be constantly bombarded with statements about how huge the potential energy resource is and how cheap it is…or is going to be any day now. Might it be a cause for concern that these two reasons were also promoted by water proponents in the 19th century Britain just when coal was taking over? Might there be a risk, we are discussing beside the point? If excessive reliance on variable renewables end up limiting capacity utilization, is there not a similar risk that water power faced in the 19th century? Who bears the cost of lower utilization? Labour? Lower salaries and/or more irregular working hours anyone? Vacations in the winter since solar power produces mainly in the summer?  If push comes to shove and such questions have to be asked, I am quite sure any techno-fetishes we might have, will evaporate.

To me conclusion seems clear. It is unlikely humanity will ever be primarily powered by variable renewables. If fuel etc. costs for dispatchable generators are high compared to the cost of electricity from variable renewables, wind and solar might be economically justified as a part of a more diverse fleet of generators. However, it is also possible that on economic grounds they will remain niche producers whose existence is dependent on subsidies and political good will. Future will tell.

This will probably be a fairly long post mainly summarizing findings from my simple toy model….so proceed at your own peril.  For a while I have been interested in how the properties of the power source affect the end user. For the consumer different power sources deliver very different value, but the public discussion is typically centered (more or less honestly) on costs. I think one issue of great relevance is the capacity utilization and the aim of this post is to record my studies on the matter. In particular I wish to explore the variable power sources such as wind and solar in the context of capacity utilization. My thoughts are in the end closely related to “capacity factor rule” discussed by John Morgan, but I approach the issue from somewhat different angle.

What is a capacity utilization  and why it matters?

Capacity utilization compares realized production with what could be possible. The concept seems to be somewhat fuzzy since theoretically maximum output could be defined in different ways. However, for an advanced economy capacity utilization is high, for example, in EU it is typically higher than 80% with a scary dip during last financial crisis. In an undeveloped country capacity utilization is lower, for example around 55% in Bangladesh. This makes sense, since things like poor infrastructure hamper production that might have otherwise happened. High capacity utilization is needed especially when lots of capital is spent since otherwise production could not cover capital costs. If high capacity utilization cannot be ensured, investments requiring large amounts of capital will not happen (unless one finds someone to pay for the losses).

In a developed economy capacity utlization is not really limited by the power supply. We get power from the plug whenever we need it. Capacity utilization is limited more by things like rising labour costs if one aims for maximum production or perhaps uncertainty on whether or not a buyer can be found for the product. However, our electricity production follows the demand and not all power sources can do that. Some view it desirable that consumers should in fact adjust their consumption according to weather. This raises the question: “How will this limit the capacity utlizations?”

This is a hard question and I can only scratch the surface here. I assume a “machine” or factory that can use certain amount of power and what is produces is proportional to its electricity consumption. I will then either use wind power or solar power as a power source and also add a storage to help even out the power variations. If there is excess power and storage is not full, we fill it. If power supply is lacking, we drain the storage. (I assume 80% round trip efficiency.) How much power machine can use, is a variable. It probably makes no sense for this to be higher than the wind or solar capacity, but if it is reduced utilization rate for the machine can probably be increased. It should be noted that the estimates below do not (of course) use the economists definitions for capacity utilization. This is more likely to give an estimate on the additional limitations on capacity utilization on top of all those other factors that are operating in any case.

So let me quickly summarize what I find…

Figure 2: Wind power source limited capacity utilization as a function of “machine capacity” (i.e. what fraction of power source capacity it can use) and storage (days at average wind production). Wind power data from UK 2013.

Figure 3: same as Figure 1, but using solar power as a source. (Production data from Germany 2015.)

Figures 2 and 3 show my rough estimates for the “capacity utilization” as a function of machine capacity and amount of storage (hours of average power production). If machine capacity is equal to the capacity of the power source, capacity utlization is limited by the capacity factor of the power source. As machine capacity is reduced and/or storage is added capacity utilization can increase. However it is very hard to get to a situation where power source would not be a factor substantially limiting the overall capacity utilization.

In terms of capacity utilization wind power tends to beat solar power which has strong seasonal production profile. Removing that is hard since it would require massive amounts of seasonal storage which would (by definition) be used only by about once a year.

As machine capacity is reduced, the “factory”can run at a higher capacity utilization, but then certain fraction of the produced power will be wasted although waste can be reduced somewhat by storage. If we aim for high capacity utilization, wasted fraction can unfortunately be substantial. The unit cost of useful energy will rise with increasing waste.

Figure 4: Fraction of wasted wind output.

Figure 5: Fraction of wasted solar output. (Once daily variation is covered it is very hard to change things by adding even more storage.)

Waste can be reduced with storage, but then the question arises that how efficiently this storage is being utilized? Figures 6 and 7 illustrates this. If we add so much storage that capacity utilization is high and amount of wasted power is low, we tend to have a large amount of under utilized storage capacity lying around. Storage that is combined with solar power tends to be more efficiently used because of regular daily variation.

Figure 6: How efficiently storage is being utilized with wind power. (Here the scale is more arbitrary. I assumed full utilization amounts to one full cycle a day.)

Figure 7: Same as figure 5, but with solar power.

I suspect that these estimates are in fact too optimistic. If I choose a point from figure 2 with relatively high “capacity utilization”, the power supply for the machine is still quite erratic as seen in Figure 8.

Figure 8: Example power input to the machines when machines powered by wind had a capacity of 0.26 of wind capacity and system had 36 hours of storage at average wind output. Still a mess.

Maybe there are processes that do not mind this, but there are  also plenty of industrial processes where steady power supply is needed and where abrupt power cuts will undermine the economics of the plant. (It would be interesting to have real world examples of production economics as one changes between power sources. Do you know any? I suspect that current way of delivering power to industries in developed economies is close to optimal for their needs.)

I think I will stop here and discuss later what I think this will imply. Main point here is that nature of the power source will affect the capacity utilization and have economic consequences that are not accounted for when myopically computing the “cost” of electricity for the power sources.

Some months ago The Ecologist (among others) was hyping a “battery breakthrough” with Lithium-air batteries. Revolution was imminent. Oil was doomed. The usual stuff. We will just have to wait maybe 10 years.

Any day. now!

As it turns out, serious doubts have been raised about the hyped study and the revolution is thus postponed.

That was fast

Of course ten years is a disappointingly long time for renewable energy enthusiasts to wait. But significantly, it’s about the length of time it takes to build a nuclear power station. Indeed, if you include all the time spent in preparation for new nuclear, it’s considerably quicker.

Few months is the time-scale for the Ecologist predictions to fail? Actually given that the paper seems to have degenerated into anti-GMO, anti-medicine, anti-nuclear etc. brain dead website, this is perhaps too generous. Currently, they seem to feature Chris Busby on their front page, which indicates the depth of their intellectual bankruptcy #facepalm.

Undoubtably this failure will not have any impact on the people contributing to the Ecologist. Failed predictions will simply be replaced by new ones predicting exactly the same.

Earlier I have made some observations on Mark Jacobson’s energy scenarios. See here and here.  I continue my dumpster diving in this post with few storage related remarks. Let me start by showing Jacobson’s assumptions on energy storage in USA.

Jacobson et al.2015 assumptions on storage. Basically free.

Jacobson et al.2015 assumptions on storage. Basically free. (Ignore the factor of 100 mistake in the 3rd column for UTES. They didn’t mean that.)

Notice that storage is dominated by underground thermal storage. According to Jacobson underground thermal storage of more than 500TWh deliverable heat would cost between $1.75-78.26 billion in USA. For me perhaps the most striking thing about those numbers is the range. If you cannot tell whether something costs few billion or almost 100 billion, I would say you don’t actually have any idea on the costs. You have no basis on which to make serious claims on costs. Be that as it may, notice how Jacobson also claims that storage doesn’t really cost anything…less than 1 cents/kWh delivered. How can that be true?  IRENA which is tasked to promote all things renewable certainly mentions cost as an obstacle. They also tell that UTES based on boreholes has an investment cost of 0.1-10 €/kWh (that range again!) which is dramatically different from Jacobson’s numbers.

For UTES Jacobson has model in mind in Canada. “UTES storage is patterned after the seasonal and short-term district heating UTES system at the Drake Landing Community, Canada”. This is a group of 50 homes that get lot of their heat from solar thermal coupled to seasonal storage. Let us google…. and find a presentation by American association of Physics teachers. Boreholes, district loop, and short term storage alone had a cost of more than 20000$/home. This is far more than what IRENA says is the limit for financial attractiveness (0.25€/kWh investment cost). These houses were built only with generous subsidies from the public sector. Furthermore, if I read correctly the seasonal UTES system in Drake Landing can store about 12000 kWh per household. Of this about 60% is lost to the ground. So in Jacobson’s electricity heavy scheme we need almost 3 kWh of electricity in the summer to have 1 kWh of heat in the winter.  If you compare the cost to heating with natural gas, there is easily an order of magnitude difference in favour of gas. Conveniently Jacobson et al. excluded other sectors than electricity sector in their cost discussions. Miraculously demand for an order of magnitude more expensive heat just appears to help solve the integration problems of 100% WWS scenario….Not that Jacobson would bother to mention the issue. Mind boggles. While we are thinking, how much would it cost to change american houses so that they would be heating from UTES systems?  Let me guess… about 0.001…0.002 cents/household?

Incidentally Jacobson also has a soft spot for using cars to assist electrical grid. In 2011 he (and Delucchi) gave some cost estimates.

Delucchi and Jacobson 2011 on cost of vehicle to storage

Delucchi and Jacobson 2011 on cost of vehicle to grid storage. Range 1.4-17.6 cents/kWh


Delucchi and Jacobson intepreting V2G costs...

Delucchi and Jacobson intepreting V2G costs…

Notice the absence of references and that they claim (among other things) that V2G cycling does not really degrade the battery in any relevant way. This is an interesting claim. Why are there no references? I want to learn more. Why haven’t I heard about this before? Aren’t the physical and chemical processes in V2G cycling precisely the same as the ones in driving a car (give or take the bumpy road)? However, as years passed Jacobson became unhappy with the earlier values and in 2015  they quietly “updated” (no reference given) the V2G figures so that the upper limit was removed while everything got even better.

Some update! Vehicle to grid is also almost free.

Some update! Vehicle to grid is also almost free.

Meanwhile on planet earth I notice that others don’t seem to think V2G is free. Googling I, for example, quickly find a recent estimates from pluginamerica.org. They give a cost range of  about 20-40 cents/kWh. This is not even contained in Jacobson’s earlier cost range let alone his 2015 update of 0.3-0.6 cents/kWh. Someone has made a mistake of a factor of 100 or so. (This time it is relevant.)Blackadder-Confused-Look

This is getting too depressing and disorienting. Time for a drink.

Screen Shot 2016-01-02 at 18.53.51

Mark Jacobson brought to you by Shell.

Finns have traditionally had a low self-esteem and have been very concerned what others think of them. Running into Mark Jacobsons 100% RES energy scenarios gave me a rare chance to come in touch with my inner Finn. For this I wish to thank him. His “visions” are visibly marketed online for example at 100.org website and National Geographic with a help from none other than Shell. (For the actual papers and associated pile of excel files see here.)  Reading his papers and excel files made me wonder, what have we done to deserve his wrath?

Let me elaborate. As a backbone of our energy system Mark Jacobson and his accomplices grant Finland 29 GW capacity of onshore windpower, 27 GW offshore, and almost 50 GW of photovoltaics. For reference notice that our maximum electricity demand is around 14GW in the winter and 9 GW in the summer. Total energy consumption is somewhat less than 400 TWh. In size we are about 1% of EU which has around 90GW of photovoltaics installed. So according to Mark on a windy sunny day production could be more than 10 times our demand and around 7 times the maximum (winter) demand. Our installed PV capacity would be comparable to whole PV capacity in EU today which has, after all, spent around 10 years constructing it. This all seems a bit intimidating.

Considering how off-scale this is it is noticeable that Jacobson spends very little time  spelling out the details of how exactly are we supposed to cope with implied massive swings in production. From his excel file I cannot find details on what he assumed for our grid and how much his assumptions end up costing. He also says there won’t be any new hydropower (we have 3.2 GW), but there might be pumped hydro storage. They tell us “…we restrict our calculations to assume each country can generate all of its annually-averaged power independently of other countries, since ultimately this goal may reduce international conflict.” So that water will be sloshing somewhere in Finland since otherwise we might invade Sweden and Norway (and Russia while we are at it). Makes sense. If I read this correctly our hydropower is supposed to be configured in such a way that it pumps water upstream at massively higher powers than downstream. Somehow I feel we need a 2nd opinion from someone with actual competence in engineering. (Maybe Mark meant that we were supposed to use hydrogen storage somehow? Well, no he didn’t. According to him just 1.24 GW, out of total average demand  close to 30 GW, or about half of the transport demand was diverted to electrolysis. Something very weird is happening behind the scenes and I have a nagging suspicion science fiction is involved.) Also note that our electricity demand is never less than about 6GW so potentially we are supposed to shut down the country for Mark. No problem!

Furthermore, why doesn’t Jacobson tell us where  those mythical pumped hydro storages are? If you have a look at the topographic map of Finland, you will quickly realize why this is a critical question.

We are a mountainous country…by dutch standards.

Finland is a flat country. If you drain our biggest lake Saimaa (the funny shaped water area between Lappeenranta and Joensuu) you might get around 5 TWh of energy. It feels unnecessary to point out that this cannot be done. Furthermore, you cannot even pump all that much water into the lakes since that would flood the cities, summer cottages, roads, and railways next to the lakes. Jacobson should probably add an army of goons into his employment figures to ensure the continuing happiness of our sad little country when his plan is being implemented.

Jacobson also suggests we get about 20% of our energy needs from photovoltaics. This made me laugh. Here is a picture from the moment when my power consumption for 2015 peaked.

20% of energy from photovoltaics.

20% of energy from photovoltaics. Sure Mark! Whatever you say

Picture is taken towards a calm lake (very little wind) when I was leaving a sauna during Christmas. Since lake was freezing the scenery was pretty, but too few photons of right energy hit my phone. Sauna was powered by bioenergy (aka trees) and consumed several tens of kW of power. In the heating stage probably closer to 100kW. (Sauna stove was emitting ridiculous amounts of particulate matter and all sorts of carcinogenic carbage. It was also very enjoyable and I warmly recommend it. We do it with kids.)

Of course a Finn would check the scenario not just for Finland, but also our dear neighbour Sweden. Sweden is about twice our size and has per capita GDP that is roughly comparable to ours. To remind you, according to Jacobson we are supposed to get around 20% of our energy from photovoltaics. Sweden on the other hand is inflicted just with around 1% share.

 

Mark lets us play on our strengths -- sunshine!

Mark lets us play on our strengths — sunshine!

According to Jacobson upfront capital costs for the electricity generators alone would be more than $225 billion. This is about the same as our GDP. What about Sweden? In Jacobson’s scheme Sweden will pay less than $170 billion in upfront investment costs. Less than us even though they are twice our size. Thanks Mark. What is it? IKEA? Nobel committee? ABBA?

In Jacobson’s vision employment in our energy sector grows from about 38000 to 130000. Doesn’t this mean massive productivity reduction in our energy sector? Isn’t that a bad thing?  In the topsy-turvy world of 100% RES discussions this is of course not so. Jacobson instead talks as if we are winning by spending more.  By inverting the logic of productivity increases that I suspect pretty much all economists (whether on the left or right) agree on, he talks of our $8.15 billion/year “earnings due to jobs” as if we are winning. Sweden would end up employing only about half what our energy sector would do (quarter on per capita basis) and they would get just 0.96 billion in earnings due to jobs. Take that Sweden!

How does Jacobson actually end up with the claim that his vision would make any economic sense? He gets this basically by estimating body counts from PM 2.5 emissions and then multiplying this by “the statistical value of life”. In this way he claims that in 2050 Finland emissions would kill 600-6000 people and cost us maybe more than $100 billion or about 30% of our GDP every year. Wow! This is crazy on steroids. First of all I think this is inappropriate use of the concept “statistical value of life” and 2nd it doesn’t pass the sanity check. Here PM emissions have declined drastically in past decades thanks to cleaner fuels, filters, centralized power plants replacing small scale burning etc. What am I supposed to learn from Jacobson’s figures? That in 80s when emissions were much higher, we lost basically all our GDP because of pollution? Also, is there someone who has a life insurance for 17 million. Isn’t maybe 100000-200000 more typical…1% of their claim? Jacobson and his friends assign pollution problems to the energy system as a whole and ignore that lot of it here is actually caused by small scale burning of bioenergy. They also deny the existence of alternative ways to address pollution concerns. History already tells they are incorrect in this assumption.

Small particle emissions from Finnish transport sector. Green for road transport, blue for water. (Lipasto, VTT)

In summary, thanks for dropping by Mark! Now don’t let the door hit you on the way out.

P.S. Jacobson’s work is a treasure trove of nonsense and since I seem to like poking on carbage, I will probably return to it later. I name this post with “Part 1” for that reason.

Added 4.1.2016: I realized that Jacobson’s plan also assumes we spend about $12 billion on wave devices (almost 2GW capacity). It is a wonderful source of energy especially on the time of the year we need energy most. (More on this theme from the article by Soomere and Eelsalu. I thank @alexharv074 for the link.)

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Does that white stuff matter? Photocredit La Brionnaise

I usually write this blog in finnish, but since these thoughts originated from the comments to a recent post in Carbon Commentary this one will be in english. (See especially the comments by J. M. Korhonen and Dominic Hofstetter.) I want to understand some general issues regarding attractiveness of electricity storage and also how storage schemes are likely to differ between intermittent power sources and baseload power sources.

Since storage would pay for itself from the spread of electricity prices at different times, as a first step, I wanted to know how much do the prices actually vary. I checked this for the Swedish market and show the result in the figure. In Sweden the average range for daily variation in price is about 18 euros/MWh. Data implies that the price varies from about 0.75 times the daily mean price (typically) at night to about 1.25 times the mean price during peak demand.

Swedish spot prices (2012)

Swedish spot prices (2012)

So each stored kWh should make a profit from this spread and cannot therefore cost more than this. So it would seem that for large scale electricity storage to be interesting, the cost should certainly be less than about 10 euros/MWh. Unfortunately storing electricity is costly.
Over the lifetime the prices per kilowatt hour can vary from hundreds of dollars to thousands. If we optimistically assume a cost of 100 euros/kWh, to get the cost for a single cycle to the 10 euros/MWh range implies around 10000 cycles. If there is one cycle per day, this implies a lifetime of around 30 years. For battery systems both the cost assumption as well as the lifetime assumption are quite unrealistic. Pumped hydro is somewhat more realistic (although it has its share of problems…see here), but it is geologically limited resource and implies flooding large areas of land.

What kind of efficiency should we expect from our storage system? Let us say we have an efficiency E so that to get 1 kWh of stored electricity for sale, we need to spend 1/E kilowatt hours during storage and lose “minimum price/E” worth of sales. Selling the stored electricity will gain us (at best) “maximum price” and in order for the process to make sense efficiency must be much better than about “minimum price/maximum price”. With Swedish figures anything that has a roundtrip efficiency less than around 60% makes no sense. Naturally, less efficient the system is less it should cost so that it can still make a profit within that 18 euros/MWh range.

Increasing amount of wind power in the grid will increase price volatility. Why this would be desirable is unclear. Typically increased uncertainty is a thing to avoid since it increases the likelihood of proverbial shit reaching all the way up to the proverbial fan. Here it would seem that we first pay someone subsidies for extra volatility and then someone else to get rid of it. Maybe there is beauty in here, but it does seem well hidden. In any case increased volatility can make some storage schemes more viable, but who would build such storage? Currently wind power producers are guaranteed a market AND the price so they do not have an incentive to move their production to some other time periods using storage. For storage the system should be changed so that wind power producers do not get guaranteed prices and have to find actual customers for their product. However, even then the volatility increases to make (theoretical) large scale storage viable would have to be very dramatic and storage schemes would still have to compete with generators burning stored energy contained in fossil fuels.

How would a storage scheme coupled to say wind power compare with a scheme coupled to a baseload power plant? Even if the size of the storage would be the same, storage for wind power would have to live with much larger swings in power levels. A 1 GWe baseload power plant could store night time production at a rate from zero 0 to 1 GWe. If same amount of electricity is produced with wind power storage would be fed with anything between zero and 3 GWe. This would add to the costs. Similar conclusions apply to the rate at which the storage is discharged. If it has to cope with baseload plant dropping off grid, output of 1 GWe is enough. If it has to compensate for swings in wind power production, much more might be required. (Also, it might not be a good idea to put large mass of water moving upwards and then suddenly stop. Reliable pump power seems more fit for this purpose, but someone with required engineering skills can correct me if I am wrong.)

Since the output of a baseload power plant is also predictable, it seems clear that anyone who has storage to spare will find it easier to make a profit by coupling this storage to a baseload power plant. Finally, it should be noted that with wind power storage for about 12 hours is not enough to create a wholly renewable system. Not even close. With such a short time storage we would still need reliable (fossil fuel based most likely) power plants with capacity that is enough to cover all electricity consumption. On the other hand, 12 hours of storage coupled to a baseload power plants would go some way towards removing the need for peaking power plants.

All of the above is of course purely theoretical. I do not see any reason to believe that the cost for electricity storage would become so low as to make it economically viable in anything but fringe applications. Perhaps more viable route is to use night time production to produce heat and fuels that would reduce emissions outside the electricity sector?

Updated on 19.3.2013:  Anders Örbom raised an issue in Twitter as to how representative Sweden is due to price levelling effects of their hydro power. I hand’t thought of that and I used swedish data mainly since that I had readily available. From the link in the text one can also get the spot price in Germany. It turns out that in Germany the daily variation is stronger and amounts to about 39 euros/MWh on average. So there the storage can cost more than in Sweden and still be interesting. Nevertherless, to get the price low enough is still a huge challenge even in Germany.

I usually write this blog in finnish, but since issues discussed here might be of some interest also to english speaking audience, I decided to write this one in english.For quite some time I have been troubled by the difficulty of finding open and sensible discussions on energy scenarios where erratic energy sources such as wind and (somewhat less erratic) solar provide the bulk of the power produced. Proponents of such alternatives routinely talk as if scaling such energy sources up to significant levels poses no insurmountable challenges or costs that the society cannot afford. One can often read claims such as:

“By aggregating power generation from wind farms spread across the whole (North Sea) area, periods of very low or very high power flows would be reduced to a negligible amount. A dip in wind power generation in one area would balanced by higher production in another area.” European renewable energy council and Greenpeace (page 34).

Strangely, proponents feel comfortable in making such statements, but show a noticeable lack of interest in actually demonstrating whether the statements are true. Why is this? In science the burden of proof falls upon the claimant and it would be desirable if the same  principle were to apply to discussions about energy policies. (Notice by the way, that EREC+GP are not even satisfied with claiming that wind speeds in different parts of the North Sea are uncorrelated, but actually claim that speeds are anti-correlated.)  Why is it, that an amateur like me feels the need to do his own computations to figure out such issues rather than just being able to read proper studies online?

So as it appears hard (certainly outside academic journals) to find detailed numbers on how strongly, for example, wind power actually relies on fossil fuels, I decided to do some estimates myself. I am not primarily interested in cosmetic amounts of wind power production, but will take the ambitious renewable visions seriously and study scenarios where wind power would be enough to power the entire society. I want to understand to what extent electricity production in such scenarios still relies on reliable energy sources and what kind of energy storage is required to enable wind power to stand on its own feet. Since hydropower capacity at a global level is limited, I will mostly use the term “reliable energy source” as an euphemism for fossil fuels. Not to be too parochial and allow for massively distributed generation,  I will assume a “super(duper?)grid” coupling wind power sources from three different continents together.

As a starting point I want to create a production profile based on real wind power production data. As sources I choose south-Eastern Australia, Ireland, and the Bonneville Power Administration in Oregon. Each has roughly comparable amounts of wind power installed, but I will scale the capacity of each to 3333MW so that the combined capacity will end up being 10GW. Data for BPA and Australia is given every 5 minutes while the Irish data is every 15 min. To get the datasets to match I will make a linear interpolation of the Irish data. Furthermore, since my chosen time period for the Australian data (1.8.2010-30.7.2011) is a bit different from the other two (1.7.2010-30.6.2011), I will fold the Australian data onto itself from the end to generate few missing datapoints. I take the consumption profile from the BPA load, but reserve the right to change its scale to suit my purposes. As a result, I get a combined wind power production from three massive clusters of wind turbines on three different continents. (Note: Slight bias might be caused by increasing capacity over the year.) In Figure 1, I show the power distribution for the individual clusters and for the combined system. The distributions look a bit different from each other presumably because the Australian turbines are most distributed geographically. The combined system has about 7% probability to produce less than 10% of the installed capacity.

Figure 1: Wind power distribution for different clusters together with the combined system.

Figures 2 and 3 show how production and consumption relate to one another during one randomly picked week in two different scenarios. In the Figure 2, the minimum consumption is the same as the maximum production so that no wind power has to be wasted. In the Figure 3, the wind power produces the same amount of electricity in a year as the society consumes. Because in neither case does the consumption match the production, some reliable source of energy must bridge the difference. For now I assume that this reliable source of energy can be turned on instantaneously in response to changes in wind production. This assumption is typically wrong and eventually I will make few remarks as to how serious this assumption is.

Figure 2: Maximum wind power is less than the minimum consumption.
Figure 3: Wind power production over the year equals the electricity consumption.

For the scenario in Fig. 2 it turns out that 74% of the electricity is produced with fossil fuels and the capacity of the reliable power plants must be 92% of the peak demand. The CO2 reductions in this scenario are nowhere close to what is required and the entire wind capacity has been build to work in tandem with power plants burning fossil fuels. This modest tinkering of electricity supply is quite close to what is being practiced today in many countries.

In the ambitious scenario presented in Figure 3, some of the wind power ends up wasted and periods of low production must be covered with fossil fuels. It turns out that the capacity factor of wind power drops from around 30% to around 24%. Power plants burning fossil fuels cover about 21% of demand and their capacity must be 88% of peak demand. If we take the threat of climate change seriously, even this rate of emissions is excessive considering that electricity production is not the only source of green house gases and that the global electricity consumption will most likely rise. Importantly, it should also be noted that in this scenario the reliable power plants are running at a capacity factor of only 15% which increases the cost of their power dramatically. Under this scenario one would quite likely (and perversely) end up paying subsidies to the owners of the power plants burning fossil fuels.

(As an aside,  a leaked European Commission document apparently includes a 50% wind scenario by 2050. Based on the above approach this would imply a need for reliable power plants that can account for 92% of the peak demand. Capacity factor for these plants would be around 35%. Since solar PV production almost never peaks during peak demand and is reliably off during most of the day… CSP with storage might be theoretical possibility, but to be able to contribute to next days peak demand and compensate for the cloudy days they will need large storage. Solutions where CSP plants are backed up with fossil fuels are clearly not satisfactory.)

That these scenarios rely fundamentally on fossil fuels does not feel right to someone seriously concerned about climate change. This dependency can be broken if wind power during periods of high production could be stored somewhere. How much storage would be needed? I will now assume that: (i) (only) 20% of the energy is lost during the transfer of wind-generated energy to and from the storage, (ii) storage doesn’t “leak”, (iii) there are no limits on the storage input-output powers, and (iv) that the storage is arbitrarily large. Only type of storage that might approach these conditions even to some extent, appears to be pumped-hydro storage.

In Figure 4 I show how the energy content in the storage varies over the year. I choose the consumption to such a level that the storage at the end of the year is about the same as in the beginning of the year. It turns out, that the entire electricity consumption (95% of wind production) could be covered with wind power if the storage amounts to about 9% of the yearly production or 2.5 million MWh. In practice about this amount of energy would be released when the water from a 90km^2 lake that is 20 meters deep drops 500 meters. Naturally this (fresh) water would also have to be stored at lower elevation to await pumping back into the mountains. However, this scenario appears somewhat unrealistic in that it requires that we can store energy at a power 5.1GW and release it at 4.3GW. These figures are massive relative to the maximum demand of 4.7GW.

Figure 4: Content of the energy storage over the year.

So let us proceed to make things perhaps a bit more realistic by throttling the storage input-output power to “just” 1GW. In this case some of the wind power is again lost and dependence on fossil fuels reappears. Consumption can now be 89% of yearly wind power production and storage must be sufficient for about 5% of production. 4.5% of consumption would be covered by reliable power plants running with a capacity factor of just 5%. However, their capacity must still be 63% of peak demand. If we throttle the storage power further, the need for fossils fuels increases.

What if we just store energy for few days? If the storage is for 5 days peak production and we throttled its power like before, about 9% of consumption must be covered with reliables. Their capacity must be 70% of peak demand and the capacity factor is 8%. If we are to remove reliables entirely from the picture, the consumption must drop drastically to the average level of about 900MW. Naturally, this implies a drop in the winds capacity factor to less than 9%.

So far I have assumed that reliables can react instantaneously to changes in wind power production. Let us add a delay of 10-30 minutes to the scenario of Fig. 3, where most electricity was from wind. I.e. I assume that if the reliable source was turned off, it takes 10-30 minutes for it to start producing power again. In Figure 5 I show the resulting difference between production and demand. As is clear, even with only 10 minutes delay more than 600MW mismatch can appear. Smaller discrepancies appear regularly over the year and their frequency increases as the reliables response becomes more sluggish. These observations presumably set some constraints on the amount of reliable power plants which must either be constantly spinning no matter what the wind conditions are or be able to react very rapidly to changing wind conditions (hydro probably).

Kuva 5: Mismatch between delivered and needed power for few different delays.

It is of interested to check what did we actually gain by combining Irish, Australian, and BPA productions with the “super grid”. If we only use the production data from Australia for the wind dominated scenario, 24% of the electricity would come from reliables (21% with the “supergrid”) , required reliable capacity would be 92% (vs. 88%), and the reliables capacity factor would be 17% (vs. 15%). Therefore, it seems that distributing wind turbines over an area larger than around 1 million square kilometers provides only modest additional benefits. These benefits should naturally be balanced against the additional costs.

In all the above I have taken the consumption pattern to be fixed. In  principle, using smart grids the consumption could change. However, not only does the required change have to be very rapid, but it also has to be potentially a very large fraction of the total demand. It is naturally partly a political and ideological question whether it is desirable to force the society to adapt to failures of the chosen technology rather than demanding that the technology adapts to way people behave. (The way I phrased it, makes it quite clear where I stand.) In fact it is curious how eagerly proponents of, for example, wind power wish to rely on smart grids even though the most obvious use of smart grids seems to be almost diametrically opposed to their vision.

Sending more detailed pricing signals to consumers, has the potential advantage of lowering peak demand and perhaps inversely increasing night time demand. Under such circumstances the difference between average and peak demand is reduced and the share of the baseload power actually increases. In the extreme limit we would end up with an electricity supply entirely made out of baseload power plants (coal or nuclear typically). Not only would this lower the cost of average kWh, but it would also seem to simplify the design and maintainance of the energy infrastructure. I.e. used in this way, a smart grid seems to be a really smart idea! However, the way proponents of unreliables intend to use smart grids is quite different. For them smart grid is a way to lower demand not when demand is necessarily high, but when their favored energy supply is failing. Smart grid is then transformed into a system of managing blackouts. Then it is about giving consumers the choice between very costly energy and a blackout. Managed blackout is certainly better than unmanaged one, but how is it exactly better than not having blackouts is unclear.

For the reasons above, I think it is clear that it is very difficult to base the electricity supply on erratic sources of energy. As soon as we start estimating the required storage capacity or the capacity of reliable backup power, we end up with massive figures, implying huge escalations in costs, or an unacceptable reliance on fossil fuels. Getting the production and demand to match each other becomes ever more complicated, and I cannot help myself thinking that the resulting device starts to, more and more, resemble a Rube Goldberg device.

Here is the scenario you end up with: If wind power is too variable, build a supergrid and then connect it to smart grid. Then combine everything to solar power on the other side of continent, which will be smoothed with wave power coupled to geothermal, and as an icing on the cake build large number of microlevel bio, natural gas,and hydro power plants across the continent. If the goal is to create a reliable voltage difference, is there no easier way? If the goal is to redistribute common resources to those who manufacture pieces of the device, however,  then there is unarguably some internal logic. Also, if the real goal is to maintain de facto dependence on fossil fuels, this approach is eminently sensible.

Figure 6: Rube Goldberg device comes in handy when you need to brush your teeth.

Unfortunately, this kind of confusion makes it harder to understand how the whole system works (or doesn’t work) and also harder to understand the final costs and emission levels involved. (Sometimes I get the feeling that proponents for unreliables prefer it that way.) Such visions do not become more convincing when one observes the politics involved. Each part of the device is constructed with scant regard for other parts, with multitude of different national (especially in the European Union) subsidy schemes. Many parts of the device also seem to be more like rhetorical tools, to divert attention from the shortcomings of the activity under spotlight. For example, supergrids are often evoked as a tool that would make huge fluctuations of wind power at national level disappear. As we have seen from this analysis, not only is this assumption unjustified, but it also seems unclear who exactly is supposed to pay for such grids. It is certainly not included in the typical cost estimates for wind power. Also, how are the small nations around Germany, some of which have no need for wind power, supposed to balance the wind power of 80 million Germans? Would Germany pay for the construction of wind turbines in, and transmission cables from, another country? Not likely.

Only scenarios which are based on reliable energy sources from the beginning seem to avoid the problems discussed here. Scenarios based on unreliable sources become progressively harder as their share of electricity supply increase. Reducing GHG emissions sufficiently requires, in practice, total decarbonization of the electricity supply, and the emissions reductions achieved by the time erratic sources run into trouble are far too low. I cannot avoid the conclusion that approaches based on renewables will mainly, at a very large expense, end up delaying the real decisions we must eventually make to lower emissions to acceptable levels. The alternative zero-carbon baseload source seems rather obvious…

(This posting appeared as a guest post in Brave New Climate and you should read the discussion there.)

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