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Seeking Consensus on the Internalized Costs of Energy Storage via Batteries

What is meant by “internalized costs”?

Internalized costs are the costs which can be accurately accounted for in our current systems. In energy production, these costs typically consist of capital costs, financing costs, operation and maintenance costs, and exploration costs. Some energy options incur these costs in various stages such as extraction, transportation and refinement. Profits and taxes are excluded wherever possible in order to isolate the pure cost of production.

Internalized costs of energy storage

This article will cover two battery-based energy storage solutions: standard batteries and flow batteries. Three currently mature energy storage technologies – backup thermal power, pumped hydro storage and compressed air energy storage – were covered in a previous article, while synfuels will be covered in the next article.

General comments on battery storage economics

Before we get started, some general comments on battery storage economics are in order. As discussed in the previous article, the most important factors influencing the economics of specialized energy storage technologies are the capital costs and the capacity utilization. Capacity utilization is an especially important issue in energy storage because of a trade-off between capacity utilization and the spread between the price at which the storage facility can buy and sell electricity. At higher capacity utilizations, the initial capital investment will be better utilized, but the spread between the buying and selling price will also reduce.

Germany currently offers a good example of the type of buy-sell spreads available in a system with substantial intermittent renewable energy penetration. As shown from the graph below, a buy-sell spread of about €20/MWh is available for probably about 20% of the average day while spreads of €50/MWh are only available on isolated occasions.

An important feature distinguishing batteries from other energy storage technologies is that storage capacity (kWh) is generally the economically limiting factor instead of output capacity (kW). This implies that a limited battery storage capacity must be utilized at as high a frequency and discharge depth as possible, while facilities like pumped hydro where storage capacity is not such a limiting factor are free to cycle over longer timespans.

The figure above illustrates this issue. As can be seen, significant spreads exist between weeks with high wind output and low wind output as well as between weekdays and weekends. These spreads are not economically accessible to battery technologies which should be cycled very frequently (at least once per day) to more economically utilize the limited storage capacity. In contrast, a pumped hydro facility with a week or more worth of storage capacity can take advantage of these spreads.

In addition to cycle frequency, cycle depth is also an important parameter in battery storage. Since the availability of high frequency spreads will vary significantly from one day to the next depending on fluctuations in renewables output and local electricity demand on weekly and seasonal timescales, the economically viable depth of discharge will also vary significantly. For example, batteries could be useful in Germany over summer when solar PV creates a reasonably reliable daily cycle, but will be of very limited use in winter when solar PV output is minimal and more unpredictable wind power dominates.

Another factor to take into consideration is that depth of discharge is often an important determinant in battery lifetime where shallower cycles can significantly prolong battery life (see above). In addition, battery lifetime is not only measured in cycles, but also in years. For example, reported Li-ion battery lifetimes range from 1000-10000 cycles and 5-15 years. At one cycle per day, 10000 cycles will take 27 years to complete implying that age-related degradation would probably have rendered the battery unusable long before the cycle lifetime is over.

Finally, it must be acknowledged that there exists substantial uncertainty regarding the economics of pre-commercial energy storage technologies like batteries. Numbers utilized in this article are guided by data available from the reviews of Duke University, the IEA and DNV. Various literature sources were also consulted to confirm that data in these reports is reasonable (Mahlia, Chen and Gonzalez).

Standard batteries

Batteries are often the first thing that comes to mind when considering energy storage. Standard batteries are especially attractive to advocates of distributed renewable energy because they can be deployed on small scale.

Even though Li-ion batteries are making all the headlines, most deep-cycle batteries for renewable energy application are still based on mature lead-acid technology. These batteries have the advantage of low up-front costs (~$150-200/kWh at most wholesalers), but have relatively short lifetimes, relatively high temperature-sensitivity, significant maintenance requirements and significant waste-handling challenges.

The breakeven electricity price spread for lead-acid batteries is given below as a function of the average depth of discharge and the capital costs. Other assumptions include a 2000 cycle service life with no degradation, 75% round-trip efficiency, an average of 1 cycle per day, balance of system costs of $150/kWh, O&M costs $20/kWh/yr, an electricity buying price of $30/MWh and a 5% discount rate. Balance of system and O&M costs are not often considered, but, just as is the case with solar PV will probably become a very important factor as battery prices fall. These costs are taken on the lower edges of the ranges given in the Duke University review. The Excel spreadsheet used to create this figure can be accessed here.

Given that most suppliers recommend a maximum depth of discharge of around 50%, it is clear from the above figure why deployment of lead-acid batteries for energy storage is very limited. Even under the lowest cost assumption, a 25% average depth of discharge requires an enormous breakeven spread of $800/MWh.

Li-ion batteries are not yet commonly available as solar backup options. One online supplier sells these batteries for around $1000/kWh which is much more expensive than lead-acid batteries. Tesla-manufactured batteries offered by SolarCity also appear to be in that price range. In exchange, Li-ion batteries offer longer lifetimes, lower maintenance requirements and higher round-trip efficiencies. The above figure is repeated for Li-ion batteries below under the assumptions of a 5000 cycle service life with no degradation, 90% round-trip efficiency, an average of 1 cycle per day, balance of system costs of $100/kWh, O&M costs $10/kWh/yr, an electricity buying price of $30/MWh and a 5% discount rate.


 

The figure shows that, thanks to the longer lifetime, lower maintenance costs and higher round-trip efficiencies, Li-ion batteries at $400/kWh have slightly better economics than lead-acid batteries at $100/kWh. Thus, if deep cycle Li-ion batteries for energy storage applications come down to $400/kWh, the choice between Li-ion and lead-acid will depend primarily on the locally applicable discount rate.

It is clear from the two figures above that battery storage is still about an order of magnitude from being economically viable given the price spreads available in wholesale electricity markets (around $50-100/MWh). However, sufficient subsidization could make batteries a viable option for early adopters in countries where household electricity prices are exceedingly high and feed-in tariffs are being reduced to limit deployment. For example, German households currently pay around $400/MWh for electricity and receive around $180/MWh as feed-in tariff for solar power fed back into the grid. Households can therefore avoid up to $220/MWh by storing more solar energy for self-consumption instead of selling it back to the grid.

This spread will further increase in the future, but will likely remain too small to drive significant deployment for the foreseeable future in the absence of subsidies which are substantially more lucrative than those currently in place.

Flow batteries

Flow batteries, Vanadium Redox Flow Batteries (VRB) in particular, are attractive due to their very long lifetimes even under consistently high discharge depths, their good scalability, and their flexibility in managing power and storage capacity separately. They are generally not suitable for small-scale applications, however, and are therefore targeted more towards grid-scale energy storage. Drawbacks include fairly average round-trip efficiencies and significant O&M costs.

The breakeven spread for VRBs is given below as a function of the capital costs and depth of discharge. Other assumptions include a 14000 cycle service life with no degradation, 75% round-trip efficiency, an average of 1 cycle per day, balance of system costs of $150/kWh, O&M costs $30/kWh/yr, an electricity buying price of $30/MWh and a 5% discount rate. The Excel spreadsheet used to create this figure can be accessed here.

When considering that VRBs can be discharged to 95% without any significant ill effects on lifetime, the figure above starts to look somewhat more promising. Naturally, the average depth of discharge achieved in practice will be much lower than 95%, but this will still improve the economics of VRBs relative to lead-acid and Li-ion batteries which should not be discharged beyond 50%. That being said, however, VRBs remain several times more expensive than pumped hydro storage analysed in the previous article even under the most optimistic cost assumptions.

Commenting

If you have a number that differs significantly from the estimates given above, please add it in the comments section below together with an explanation and a reference. 

Content Discussion

Schalk Cloete's picture
Schalk Cloete on July 10, 2014

DATA: Standard battery breakeven spread: $900/MWh.

This value is calculated for lead-acid batteries at $150/kWh and 25% depth of discharge or Li-ion batteries at $800/kWh and 30% depth of discharge.

Schalk Cloete's picture
Schalk Cloete on July 10, 2014

DATA: Flow battery breakeven spread: $450/kWh.

This is based on VRBs at $500/kWh and 45% average depth of discharge.

wind smith's picture
wind smith on July 10, 2014

I own a 2003 honda civic hybrid with 114,000 miles on it. Unlike the Prius it has a battery charge gauge on the dash that has an accuracy and resolution of about +/-3 percent. I maximize the dynamic braking so that on average I would say each acceleration or hill discharges 20 percent of the nickle-metal-hydrid 160vdc battery every mile. That would be 114,000 discharges after it’s so far 11 year life. Based on many observations my educated guess is 1kwh storage capacity so 20 percent is .2kwh/cycle x 114,000 cycles = 22,800kwh so far. If battery cost is around $3000 then 3000/22800 = $.132/kWh. Even with my guesses, I don’t think I’m off more than 2x. The battery performs like new in warm weather but I notice some lost performance in winter.

Nathan Wilson's picture
Nathan Wilson on July 11, 2014

Great article as usual.

Much of the enthusiasm for batteries comes not from their current cost, but from their cost trajectory, so it is important to discuss that. This article discusses a 2012 report from Lux Research which forecasts that Li-ion batteries will cost $397/kWh* in 2020.

So, reading from the graph above, and using a higher 50% depth of discharge**, and $400/kWh, we get: 

DATA: 2020 Li-Ion battery breakeven spread: $350/MWh (=35¢/kWh)

 

$397/kWh is not as low as the price expected by enthusiasts.  The U.S. Advanced Battery Consortium has a target of $150/kWh, in order to make a 60kWh automotive battery (such as used in the low-end Tesla Model S) cost $9,000; more of a goal than a prediction.  Even this price would be uninteresting compared to alternatives such as fossil fuel or pumped-hydro.

** A low average depth of discharge would be appropriate for off-grid systems, since the use of backup fossil generator at the first cloudy morning would be undesirable (hence the system is over-sized relative to the typical day).  

For a grid-tied commercial/utility solar system in a sunny area in which the system was designed for around 70% depth of discharge for sunny days during the sunniest half of the year, the year-around average depth of discharge (including cloudy days and low-sun winter days) would be around 50%.  This high utilization basically assumes the batteries are installed and operated by mandate, not market economics.

Nathan Wilson's picture
Nathan Wilson on July 11, 2014

It is also worth discussing battery recycling, since with major grid-scale battery use, the end-of-life disposal quantities involved would be enormous.

This 2000 article from the US Argonne National Labs has a section on battery recycling.  Lead-acid battery recycling is relatively easy, since they are easy to disassemble, and they contain only the plastic housing, lead, and lead-sulphate.

Li-ion packs have much higher dissassembly cost (the article cites a data point of $1.25 for each 95 gram pack).  The use of larger cell sizes will reduce the cost per unit mass (note Tesla uses laptop type cells, in the 50 gram range).  Obviously, outsourcing the disassembly to China will reduce costs (at the likely trade-off of reduced environmental and worker protection).

The other problem is the large variety of materials involved.  The most valuable components are the small amounts of cobalt and lithium contained (with >70% recovery rates hoped-for).  The largest constituents are the aluminum or steel case, and the aluminum and copper foil electrode substrates.  The carbon has an extremely low value which is discarded as a sludge or cake.

Clayton Handleman's picture
Clayton Handleman on July 11, 2014

Li-ion batteries are moving extremely fast and continue to blow past analyst estimates.  However, the latest firm pricing data is from Nissan which has offered Leaf replacement batteries for $6500 which comes out to $270 / kWhr

Research reports that came out prior to the Tesla Giga factory announcements had pricing by 2020 at $160 – $180 / kWhr.  The most optimistic of those came from Navigant which also said that they expected to see $300 / kWhr by 2015.  So Nissan has already exceeded the most optimistic projection put forth by credible sources. 

It would appear that the purpose of this exercise is to freeze a moment in time and then use it to assess what will be best for the future.  Technologies such as PV, wind and Li-ion battery storage are in rapid price decline so this approach heavily favors fossil fuel approaches.  Having said that I will weigh in on Li-ion.  If we snap the shutter today it appears that Li-ion is at $270 / kWhr and that a conservative figure for 2020 is $150 / kWhr.

As you pointed out, the lead acid degrades as you deep cycle it.  Li-Ion can go much deeper without degrading performance or lifetime.  This generally gives about a 2-1 capacity equivalence.  In other words, you need about half the Li-ion capacity as lead acid for a given deep cycle application.  I think that the pricing for Li-ion is at about $270 / kWhr today and falling.  This study shows the per MWh cost of Li-ion at a little over $200 / MWh after accounting for Euro exchange and drop in Li-ion battery prices since the study was performed.  So if you are right in your numbers, it appears to be in striking distance for German PV. 

Since battery prices are following an experience curve volume = cost reduction.  Germany combined with EVs and some other markets I have identified will push pricing rapidly down.  Though I suspect there will be a lithium shortage at some point that will have a similar impact to the silicon shortage experienced in the PV markets. 

Clayton Handleman's picture
Clayton Handleman on July 11, 2014

Nathan,

Thanks for bringing up trajectory.  Batteries are moving very rapidly.  2013 studies (several referenced here) suggest 2020 numbers will be closer to the $150 / kwhr number than the $397 number.  It is noteworthy that Nissan is selling replacement battery packs for Leaf’s for $270 / kwhr as of June 2014. 

 

Regarding labeling of positions,

There is a tendency on this board to label people.  ‘Battery enthusiasts’, ‘PV enthusiasts’, ‘fossil fuel apologists’ etc.  This is a common method for manipulating message and polarizing discussion.  By applying a label it tends to associate that person with an extreme position typically in an effort to marginalize them and their ideas. Further it suggests an ‘in group’ that in order to belong notices those ‘others’ as being flawed.  In politics this is being done a lot by using the liberal label or teapublican to pejoritively code, at the waive of a hand, an idea proposed by a moderate as a being grouped with a more extreme position.  This diminishes the value of the discussion and undermines the quality of debate by attempting to negate ideas based upon association with a group rather than on their own merits. 

I hope that you will reconsider playing the labeling game. 

Schalk Cloete's picture
Schalk Cloete on July 11, 2014

Perhaps you can help me to identify the reasons for the large difference in the apparrent low cost of EV Li-ion batteries and the much higher cost of solar storage Li-ion batteries. I provided two links in the article which put pricing around $1000/kWh. This is very far from the $270/kWh figure you cite based on Nissan’s new battery replacement cost announcement. 

Do you have any estimates on how many cycles / operating years the cheap replacement Leaf battery can handle? The fact that Nissan is in fact offering replacement batteries already today (3 years after the Leaf was launched) implicitly implies that the battery lifetime is quite short. I used 5000 cycles in my calculations – enough for 20 years of service at 5 charges per week. Under this assumption battery replacement would be completely unnecessary. 

Do you think Nissan will make any profit on the replacement battery packs? The article reporting on this states that Nissan may well be losing money on this deal initially and are counting on low initial demand and future economies of scale.

What would be the BOS costs for changing a battery pack? The article states that installation fees and taxes are excluded. 

Schalk Cloete's picture
Schalk Cloete on July 11, 2014

Good point. It would be very useful to get some reliable data on this. Interestingly, the Nissan Leaf case cited by Clayton above states that Nissan will actually pay for the old battery pack, effectively implying that the old battery packs have a negative disposal cost. What do you think the economic value of old batteries would be? Will the recycled materials be worth more than the costs of recycling?

Of course, this cost/benefit would ultimately have a fairly small effect on the levelized costs since it occurs at the end of the operational life which is normally discounted quite substantially. 

Schalk Cloete's picture
Schalk Cloete on July 11, 2014

About future costs, the new IEA Energy Technology Perspectives report gives a nice summary of what needs to happen for Li-ion batteries to reach the point where pumped hydro is today. As you can see, some rather incredible progress is required to reach the mostly uncompetitive position of pumped hydro storage. 

 

Schalk Cloete's picture
Schalk Cloete on July 11, 2014

Another interesting point in your comment is about deploying batteries in places where solar is best suited. I agree that this will have a very large effect on battery storage economics which are dependent on a reliable demand for high-frequency storage throughout the year. However, these places are usually very hot, implying that battery lifetimes could suffer as a result (or extra O&M costs will be required to keep the batteries cool). Li-ion batteries are more heat resistant than lead-acid, but still have this problem. It will be interesting to get some more info on this tradeoff. 

Clayton Handleman's picture
Clayton Handleman on July 11, 2014

‘Perhaps you can help me to identify the reasons for the large difference in the apparrent low cost of EV Li-ion batteries and the much higher cost of solar storage Li-ion batteries. I provided two links in the article which put pricing around $1000/kWh.’

– Low volume application for the listed prices.  The Tesla numbers are heresay.  Any industry insider can make stuff up.  There was insufficient information to even speculate on the quality of their source.

‘This is very far from the $270/kWh figure you cite based on Nissan’s new battery replacement cost announcement.

Do you have any estimates on how many cycles / operating years the cheap replacement Leaf battery can handle? The fact that Nissan is in fact offering replacement batteries already today (3 years after the Leaf was launched) implicitly implies that the battery lifetime is quite short. I used 5000 cycles in my calculations – enough for 20 years of service at 5 charges per week. Under this assumption battery replacement would be completely unnecessary.’

– I imagine they anticipate low volume initially and that the purpose is as the article says, reassure customers that it will be available and what the cost will be.  I think it is highly unlikely that they plan to replace at a loss when the volume picks up.  So no, I don’t think they are replacing many only 3 years out.  The person I know who has one, routinely deep cycles, twice per day (charges at the office due to long commute) it is holding up well.

‘Do you think Nissan will make any profit on the replacement battery packs? The article reporting on this states that Nissan may well be losing money on this deal initially and are counting on low initial demand and future economies of scale. ‘

– What the article says makes sense to me.  They are ramping production as this is the same battery as in their newest model.

‘What would be the BOS costs for changing a battery pack? The article states that installation fees and taxes are excluded.’

– It seemed clear to me from the article that the change out costs are a small percentage of the battery pack cost. 

 

Bottom line, do I think that Nissan can sell these at a profit today, no.  Do I think that this pretty much guarantees that in 1 – 3 years these battery packs will be profitably sold, yes.  In other words, it looks to me like this is very supportive of the Navigant numbers over the Lux numbers. 

 

Schalk Cloete's picture
Schalk Cloete on July 11, 2014

If EV battery prices can be used for reliably estimating the cost of Li-ion stationary energy storage applications, why don’t battery suppliers simply sell EV batteries as solar backup solutions? Almost all the deep-cycle battery supplyers I looked at offer predominantly lead-acid solutions. If EV batteries at $270/kWh could be used for stationary energy storage, all of these supplyers are missing out on some serious business opportunities.

Li-ion technology at $500/kWh with a 5000 cycle lifetime should already be greatly preferred over lead-acid for stationary energy storage applications due to the longer lifetime at deeper discharge, higher efficiency, lower maintenance and lower temperature sensitivity. In fact, as described in the article and my comment below, Li-ion should be competitive with lead acid even at $800/kWh. EV batteries have been below this number for some years now. Why is this not reflected in the market? 

Nathan Wilson's picture
Nathan Wilson on July 11, 2014

I’m sorry for any offense I have created with labelling.  But re-reading the paragraph in question, I’m not sure how to make it any better.  I feel like data doesn’t mean much unless the source is revealed.  

All too commonly, we see seamingly neutral articles about nuclear power which include a comment such as “many people are concerned about the safety of the project”.  Which people are concerned, the scientists and engineers involved? the fossil fuel stakeholders who stand to loose market share?  bystanders who learned everything they know about nuclear by reading bumper-stickers? (with apolgies to Sckalk for the taboo topic.)

When data is provided, it clearly matters when the data is provided by companies which have a financial interest in the data, and it matters whether the data source comes from an expert or a non-expert.

I could have replaced “battery enthusiasts” with “TEC forum members”, but that would undersell your expertise as well as the prevalence of the viewpoint.  I think the liberal/conservative and pro/anti-nuclear labels are the only ones that are associated with the extreme polarization you are concerned about.  Be proud of who you are, but be aware we all have biases.

Nathan Wilson's picture
Nathan Wilson on July 11, 2014

Don’t forget that Leaf sales are small and growing rapidly.  So Nissan can afford to sell at a loss to the relatively small number of existing Leaf owners, in the hopes of gaining an even larger number of future customers (who would be buying Leafs which will likely have better profit margins, and with cheaper batteries, which would need replacement even further in the future).  The Leaf also helps Nissan to sell gasoline vehicles by generating buzz.

So I believe that disposal (recyling) value is likely near zero (+- 1% of the new battery cost) – for those batteries which are too degraded for re-use (based on many recycling companies which charge a fee to recycle waste).  I suspect that the payment for used batteries is really just a version of the “core deposit” which is government-mandated in the US for all automotive lead-acid batteries (which helps maintain the very high, >90% lead-acid recycling rate).  In this case, Nissan probably wants the old batteries back mostly to avoid the liability and PR head-aches of toxic battery waste in land-fills, and instead polish their green image by demonstating a high recycling rate.

As the Nissan spokesman hints, many of these batteries will be suitable for re-use in other (e.g. stationary) applications; I would expect a retail per kWh pricepoint of maybe 25% of a new battery, but handling and refurbishment will eat into this value.  However, I believe that future EVs will have larger capacity batteries to begin with, thus 30% or even 60% capacity fade will not make them un-usable in cars.  Hence future EV batteries are likely to be “driven into the ground”, at which point they will go straight to the recycler.

Clayton Handleman's picture
Clayton Handleman on July 11, 2014

I am sticking with $270 / kwhr for storage from Li-ion batteries as the appropriate price to use.

 

 

Li-ion is an industry that is changing rapidly, it is in the process of disrupting the lead acid battery industry.  The best capitalized, highest volume players are the EV companies.  They are able to move the fastest and have the strongest incentive to move fast.  For the purposes of understanding major industry trends it makes sense to use them to benchmark the state of the art.  They are a leading indicator. 

In answer to your question as to why isn’t Li-ion showing up in PV systems.  It is.  Solar City is ready to deliver Li-ion storage now (though some regulatory hassels have slowed them down), SunPower is hinting pretty strongly that they are going to and a large number of Li-ion solutions are popping up at the solar trade shows.  Remember, from the time a company chooses to use it to when they are rolling out products with price lists, there is a product development cycle.  So what is showing up at tradeshows now has been in the works 1 – 2 years.  The collapse of Li-ion pricing is rippling through the industry and it will be mainstream in a year, 2 at most.  Lead acid is a dead man walking. 

 

 

Clayton Handleman's picture
Clayton Handleman on July 11, 2014

Perhaps I am oversensitive on the subject but I offer this for consideration.  I think you could get the same idea across doing something like this:

From:

“$397/kWh is not as low as the price expected by enthusiasts.  The U.S. Advanced Battery Consortium has a target of $150/kWh, in order to make a 60kWh automotive battery (such as used in the low-end Tesla Model S) cost $9,000; more of a goal than a prediction.  Even this price would be uninteresting compared to alternatives such as fossil fuel or pumped-hydro.”

To

‘Analyst firm Lux Research is projecting Li-ion prices at $397 / kwhr by 2020.  However, even with the much more optimistic projections of $150 / kwhr coming out of the U.S. Advanced Battery Consotium, the cost of storage remains uninteresting compared to alternatives such as fossil fuel or pumped hydro.’

That identifies your sources very clearly. 

If you disagree with an individual or a specific post I think it makes sense to refer directly to that. 

Consider the term nuclear enthusiast.  That lumps together people who support next generation technologies such as Thorium reactors or fast breeders or modular reactors with folks who are still pining for the days of building boiling water reactors with limited oversight and perpetually storing the spent fuel on site in cooling pools. 

 

Anyway, take it for what its worth.  Sometimes ruffling a few feathers gets people motivated so perhaps I should leave it alone.

 

Nathan Wilson's picture
Nathan Wilson on July 11, 2014

Ok, point taken.

Schalk Cloete's picture
Schalk Cloete on July 12, 2014

Impressive. But do you really discharge an average of 0.2 kWh/mile? Full EVs generally get economies of about 0.3 kWh/mile, implying that you get 67% of your overall propulsion from electric only which is rather extraordinary for a mild hybrid like the Civic. 

Anyway, the problem with very large number of shallow cycles for stationary energy storage applications is that you can generally just utilize 1-2 cycles per day. At one cycle per day, 114000 cycles will take more than 3 centuries to complete which is obviously totally impractical. 

Schalk Cloete's picture
Schalk Cloete on July 12, 2014

DATA: Li-ion breakeven spread: $440/MWh.

This is based on Clayton’s estimate of $270/kWh capital costs based on the recent Nissan Leaf announcement outlined in his comment below and a 30% average depth of discharge over the full 5000 cycle lifetime. All other parameters outlined in the article are kept constant under the assumption that EV battery technology can be directly used in deep-cycle stationary energy storage applications. 

Schalk Cloete's picture
Schalk Cloete on July 12, 2014

OK, I have added another DATA comment to include your opinion into the statistics. 

I am following several real-world solar PV and EV prices and will add the specialist Li-ion solar storage batteries linked in the article to this list. If you are right, these prices should collapse quite spectacularly from the current $1000/kWh price point over the next one or two years. It will be interesting to follow this very rapid development in real time. 

I wish SolarCity published their prices openly so this could also be monitored over time. If you know of a way in which I can monitor SolarCity/Tesla stationary battery solutions, please let me know. 

Nathan Wilson's picture
Nathan Wilson on July 12, 2014

“…why don’t battery suppliers simply sell EV batteries as solar backup solutions?

I suspect the the main reasons are:

  • The Li-ion cost is not really that low compared to lead-acid.  Most products need a 5x markup from manufacturing cost to retail cost, in order for the manufacture, distributor, and retailer to all make a viable profit.  Certain very high volume industries operate with much lower margins.  For example, in the automotive market, the profits are not spread evenly across products, but come mostly from the upgrades and high end models.  100 MW scale energy storage should have much lower margins than residential, but still not as low as low-end automotive.
  • Upfront cost.  For the typical off-grid homeowner seeking an energy storage system, paying double the upfront cost to get a saving which will occur several years down the road is nice in theory, but likely to be avoided in practice.
  • Liability.  Li-ion cells normally use a flammable electrolyte, so the end-result of battery failures is often fire.  The EV fires which have occured already have been bad PR for the industry.  Li-ion batteries include more sophisticated safety circuitry than other battery types, and manufacturers need to be assured their batteries won’t be used in a way that burns down someone’s house. (I worked in the cellphone industry 20 years ago when Li-ion was new and scary, but I doubt things have changed much).
Clayton Handleman's picture
Clayton Handleman on July 12, 2014

” If you know of a way in which I can monitor SolarCity/Tesla stationary battery solutions, please let me know.”

I don’t.  I think they will keep it quiet for strategic reasons.  When the Giga factory is built, the numbers will get out.  They are interested in becoming the worlds largest battery maker and will be shopping storage to other companies.

Schalk Cloete's picture
Schalk Cloete on July 12, 2014

Hi Michael, 

Thanks for taking a close look at my analysis. However, I think I do have the same units for RATE and NPER. NPER has units of years: cycles/lifetime / (days/year * cycles/day) = years/lifetime.

I verified the levelized cost methodology I use in the Excel sheet against formalized levelized energy cost calculations as given here. I also validated the methodology extensively against LCOE data given by the IEA in this report

Schalk Cloete's picture
Schalk Cloete on July 12, 2014

Wow, a 5x markup from manufacturing to retail? That is quite extreme. However, this can help explain some of the difference between the $1000/kWh in my sources and the $270/kWh in Clayton’s sources. Your other points also make sense. Will be interesting to watch the Li-ion space over coming years. 

John Miller's picture
John Miller on July 12, 2014

Nathan, my past research found that recent years’ Li-ion automobile batteries have costs closer to the $500/KWh range.  The higher cost is due to a combination of new technology and ‘light-weight’ designs.  The lighter weight Li-ion batteries are more likely to have reduced lives (up to about 5 yr. max.) and light-weight designs that definitely make the batteries more susceptible to damage that leads to shorting-out/fires; compared to heavier stationary battery applications.  Stationary batteries should also be cheaper, and possibly half the cost of light weight auto batteries; or in the $270/KWh range that Clayton references.  This is still a magnitude pricier than lead-acid batteries that have historically been used in off-grid applications (with backup petroleum motor fueled generators of course) in most Developing Countries (Mexico, India, etc.).  Lead-acid batteries are definitely cheaper, but their lives’ are typically only a couple-three years, however.  

Clayton Handleman's picture
Clayton Handleman on July 12, 2014

“Most products need a 5x markup from manufacturing cost to retail cost, in order for the manufacture, distributor, and retailer to all make a viable profit.”

This is similar to what I have seen for retail = off the store shelf pricing – Mfg sells for about 3X their cost then the retailer doubles what they purchase it for.  But there are a lot of variants on this.

For example, for commoditized products in a competitive market compress considerably.  For example, in the solar industry, when the silicon shortage made it a sellers market, the small installer used to pay a substantial premium for modules.  10’s of percent higher than volume users and that was if the distribution would sell it to the small guy at all.  When things switched to a buyers market the difference between large and small buyers compressed to a few % difference.  Also, often electrical contractors bid on solar projects or electricians are hired by solar contractors.  The model is often mark up materials 15%.  Larger firms go factory direct or volume purchase to distribution allowing for lower soft costs.  This creates a situation where margins can be compressed.

In businesses like cars and bikes they often use the primary product as a low margine platform to sell high margin options and services.  Sometime look at the base price for a Tesla and then compare to one that is loaded!  Bike shops make almost nothing on the bikes but 2x or more on accessories.

With the batteries, the Smart Battery guys are a relatively low volume specialty retailer and likely are 5x to 6x the mfg cost of goods sold.  On TEC the discussion revolves around large volume, commoditized applications.  And more recently installation, mfg, sales and finance are all being captured in a vertically integrated company cutting out the middle man.  Solar City offers a hybrid.  They are not owned by Tesla but I am pretty sure they are co-developing storage solutions allowing for exclusive agreements which compress margins.

 

Michael Hogan's picture
Michael Hogan on July 17, 2014

So when do you plan to include a look at the cheapest, most well-proven energy storage option of all – end-use energy storage? By that I mean the type of end-use energy applications to which proven, cheap storage capability can be added, usually thermal energy storage. This would include grid-integrated appliances like storage heat pumps, water heaters, ice-storage enabled air-conditioning and refrigeration systems, thermal storage for district heating applications, as well as small industrial inventory storage applications at places like municipal water and wastewater facilities. I feel justified in violating your stricture because you’ve indicated no intention of comparing these exotic, expensive alternatives to their most effective competition, an all-too-common oversight in these “storage” debates. The current cost to apply aggregation software/hardware interfaces to existing facilities is on the order of $15/kWh – yes, 10% or less of the options you spend so much time on, an order of magnitude consistent with data represented below from Sandia National Labs, the Electricity Storage Association and a series of pilot projects conducted by Ecofys. The cost to install new, storage-enabled systems is a bit higher, and the cost to retrofit existing installations is a bit higher still, but it is still orders of magnitude less than even the 2020 targets for the more exotic or traditional grid-scale alternatives you’re devoting these postings to. Indeed pumped storage hydro, a very well-proven technology, has never made economic sense on a stand-alone basis because of its prohibitive capital costs, but it has made economic sense when coupled with large, inflexible resources like nuclear (as was the case extensively in France in the 1970s and 1980s). Various aggregator start-ups and hardware makers are already in the commercial deployment phase on these options, and the most comprehensive power sector decarbonization studies have all tended to agree on one thing, which is that the scale of the opportunity to exploit these options and their proven cost and performance make it unlikely, though not impossible, that significant new investment in options such as flow batteries and pumped storage hydro will be cost-justified for several decades to come even at higher levels of penetration by intermittent supply resources. (The sole exception to that may well be G2V EV battery applications, which is in effect another end-use energy storage application.)

Schalk Cloete's picture
Schalk Cloete on July 17, 2014

Thanks Michael. Could you please provide me with links to the references you cited so that I can take a closer look at this information? I aim to be quite complete in this series of articles and would gladly write a Seeking Consensus article on thermal energy storage if it can be considered a potentially large player in our future energy landscape. 

My reason for leaving it out thus far was just that I had the impression that it does not have such a large potential and that the storage of excess electricity as low-grade heat would not be that interesting.

It is also mostly a small scale solution centred on the (relatively expensive) distribution grid. If large intermittent spikes of electricity must be accommodated on the distribution grid, it will require costly grid buildouts which will have to be utilized at a very low capacity factor, thus driving up costs. Large centralized storage solutions (PHS, CAES, P2G and perhaps flow batteries) which cut out the need to send intermittent spikes through the distribution grid have a significant advantage in this regard. 

 

Michael Hogan's picture
Michael Hogan on July 17, 2014

I tried to attach a graphic that combines data from Sandia, the ESA and the Ecofys pilots but it apparently didn’t come through. If I can figure out how to include it I’d be happy to do so. Sandia has worked with DNV/KEMA to create a tool called ES-Select for comparing various energy storage options that provides very representative results, results like those that I reflected in my first posting. Again, if there’s a way to insert a graphic I’d be happy to provide a sample of the output from Sandia. The decarbonization studies I referred to include the IEA’s recent “Power of Transformation” report, the DoE’s “Renewable Energy Futures” report from 2012 and the “Roadmap 2050” report from 2010 by McKinsey, Imperial College London and KEMA, the most independent and comprehensive decarbonization pathway studies done to date. All of them agree on the relatively limited role battery and grid-scale electricity storage is likely to have for decades to come if the most cost-effective alternatives are pursued.

As for the other two points:

1) The scale of potential is quite large, certainly more than sufficient to do what is needed in the next two decades. In the US, for example, the current installed base of electric water heaters is 45 million, representing 200 GW of potentially controllable load. Conservatively, factoring for how much of that load is likely to be operating at any given moment, the capacity to replace down-ramp services by generators from just that installed base is about 100 GW and the ability to replace up-ramp services is a bit less than that. The potential for adding ice storage to air-conditioning and refrigeration, particularly in commercial and multi-family residential buildings, is even larger. The cost of these options is considerably lower than the most optimistic projections for advanced battery technologies or the known cost for PSH and CAES – retrofitting an existing electric water heater costs approximately $200/unit today – a new storage-enabled unit costs about $600 – and allows storage of about 25 kWh very efficiently over the course of a day. An advanced battery capable of delivering a comparable service today would set you back about $10,000.

2) The impacts on transmission and distribution are far more mixed than you seem to believe. The problem of large quantities of surplus production are almost exclusively associated with solar, and much of that production will be distributed or connected at distribution voltages, not central station, so the match between the location of the generation and the location of the storage will in many cases be quite good. The storage requirements for wind production do not usually create an over-supply problem but rather a problem of production during times when demand is low, with a need to shift delivery to existing high demand periods, so there is no real impact one way or the other on distribution systems between grid-scale storage and distributed storage.

That’s a start on answering your questions.

Clayton Handleman's picture
Clayton Handleman on July 17, 2014

To insert the graphic click on the Input Format hyperlink at that bottom of the edit window.  Select Full HTML and then it should give you a toolbar which includes a little button for inputting links to graphics.  You can probably just edit your prior comment and from Edit I think you can access the Input Format .  Once in the Full HTML mode you also can cut and paste.   I simply copied this from Windows Explorer and pasted it into the post.

 

 

Michael Hogan's picture
Michael Hogan on July 17, 2014

Thanks Clayton, but the images I’m attempting to include are saved on my computer as .pdf files, they’re not weblinks. I’ve tried again pasting the graphics but they don’t show up when the reply is actually posted.

Nathan Wilson's picture
Nathan Wilson on July 17, 2014

I’m just not sold on the merit of storing electrical energy in water heaters.  

I use a natural gas powered water heater because in my town natural gas is cheap, and our electricity comes mostly from coal (with 2/3 of the energy in the coal being wasted, compared to few percent of the energy from the gas heater).

I’m also old enough to remember solar water heaters.  Back when these were favored, they always had extra large tanks (sometimes loaded with rocks) to store more energy.  So I can accept that a normal-sized smart water heater might provide a few minutes of demand-side management (for example to improve grid stability and improve compatibility between variable renewables and slow-throttling coal plants), I simply don’t believe they constitute a large scale solution to energy storage.

I’m agnostic on refrigeration with ice-storage, but again I’m not hopeful.  Pumping heat into 100 degree outside air from a 25 degree ice-machine is less energy efficient than pumping it from a 60 degree air-cooler.  So there must be an efficiency penalty for this.  So we are back to the question of how much the cost of electricity must swing for this to make sense.

Schalk Cloete's picture
Schalk Cloete on July 18, 2014

This topic can lead to much more interesting discussion, but this is not the right place to do so. I’ll therefore post an article on thermal storage after the next one on synfuels and then we can discuss in depth. 

Do you know of any reliable capital cost estimates of the storage enabled air conditioning & refrigeration systems relative to standard systems? Will ice storage have any impact on lifetime or O&M costs? Estimates of efficiency penalties related to this kind of storage would also be useful. To me, this option appears to be much more interesting than water heating, simply because cooling is most relevant in regions (and seasons) which are best suited for PV, while the opposite is true for heating. 

Gary Tulie's picture
Gary Tulie on July 18, 2014

The value of battery services in this calculation are considered to be that of arbitrage only. There are a number of secondary services which battery systems can be configured to perform which add value. 

1. Avoidance of grid / generating capacity extension – If peak demand in a remote location is rising, and projected to exceed the carrying capacity of the current grid infrastructure, then local energy storage can defer or prevent the need for a grid / local generation upgrade. 

2. Balancing services – energy storage can be used to rapidly respond to voltage or frequency variation or grid instability a service which can have considerable value. (consider the value of avoiding a major widespread power cut).

3. Black start – many traditional generators need some power to manage their ancillary systems during start up. Energy storage can provide this.

4. UPS – some users such as hospitals, air traffic control, data centres, banks, etc require or can benefit from UPS services.

When several “revenue streams / services” are provided by batteries, their value greatly increases as compared to the pure arbitrage case.

Clayton Handleman's picture
Clayton Handleman on July 18, 2014

In cases like that I take a screen shot to get it to an image format such as jpg.  A great screen shot app is called Snagit.

Schalk Cloete's picture
Schalk Cloete on July 18, 2014

Agreed, but arbitrage and seasonal storage are the areas where the real volume lies. Frequency response with a large number of small cycles per day is probably the best application for stationary battery storage technologies (although flywheels may well proove to be a better option), but, if battery storage is to be considered as an important player in the broad decarbonization of the electricity sector, frequency response and other low volume applications are not of high interest. 

Schalk Cloete's picture
Schalk Cloete on July 18, 2014

I agree, but many people participating in the energy and climate debate still see battery storage as a very important enabling technology for high-penetration wind/solar futures. My aim with this column is to get fairly accurate numbers out there for all the major energy options we have at our disposal and, as long as battery storage captures the imagination of many wind/solar advocates, it is an important technology to include in these discussions. 

Gary Tulie's picture
Gary Tulie on July 18, 2014

I would broadly agree with you whilst pointing out that low volume high value markets can help commercialise the technologies and reduce their cost just as space based and other niche applications helped make solar power affordable. 

In my view, the best way to use batteries for arbitrage is to time the charging of electric car batteries where possible to support the requirements of the grid. i.e. absorbing excess power and improving the predictability of net demand. As the electric car market grows, this measure supported by smart charging technology can offer a very substantial battery resource with minimal additional capital expenditure.

Electric car batteries can even offer short term support to the grid by supplying power at times when market prices are exceptionally high.

Pure arbitrage using either Lead Acid or Lithium Ion technology – where the batteries do not have an additional function for the moment looks too expensive to make a commercial case.

Clayton Handleman's picture
Clayton Handleman on July 18, 2014

Yes – well said.

“In my view, the best way to use batteries for arbitrage is to time the charging of electric car batteries where possible to support the requirements of the grid. i.e. absorbing excess power and improving the predictability of net demand. As the electric car market grows, this measure supported by smart charging technology can offer a very substantial battery resource with minimal additional capital expenditure.”

Time Of Use metering combined with EV charging and some time later V2G discharging will provide an orderly path to massive storage with little capital investment.  The path will look something like:

– Open Loop Non-Monetized Charging (no Time Of Use (TOU) metering ) – Just set a timer and tell your car to charge after peak. 

– Open Loop Monetized (TOU metering allows the user to monetize the value of charging at best times ) – Look at your bills and understand when the electricity is least expensive and set your charging timer accourdingly.

– Closed Loop Monetized Charging – Price signal to your vehicle triggers charging.  You would set price triggers and the car would charge only when price was below the threshold.  The algorithms could be smart.  For example, if price didn’t go down by 1:00am, charge until set point and then arbitrage to full charge.

– Closed Loop Monetized Sell Back V2G – Car is set up to arbitrage both buying (charging) and selling (discharging) of electricity.  

The last case would become practical as battery prices dropped.  Initially it would only work for the most extreme spikes since the user would not want to reduce the lifetime of their battery unless paid well for that.  However, if we truly monetize electricity, pricing would get much more “spikey” and there could be significant value assigned even over short periods of time. 

Using the car battery for arbitrage opens up an interesting possibility.  On a net basis, people could actually get their ‘fuel’ for free.  Quite a marketing opportunity there.

 

Michael Hogan's picture
Michael Hogan on July 18, 2014

Nathan, let’s remember what we’re talking about here, energy storage. All dispatchable energy storage options have upfront investment costs (even existing water heaters and “night heaters” must be retrofitted with control interfaces). All energy storage options have a round-trip efficiency penalty associated with them. And all energy storage options face “the question of how much the cost of electricity must swing” (or how much the ancillary service is worth) to make sense. The simple answer to the last question, with very few exceptions, is that as things stand at the moment storage does not make economic sense on a stand-alone basis. The proposition is that that will change as more and more intermittent generation, or more and more nuclear, is added to the system. (Fred W’s post reminds us, lest we forget, that the high penetration of nuclear on the French system was only possible when coupled with parallel and considerable investment in pumped hydro storage and in a nationwide network of resistance electric water heaters that store thermal heat for various local applications. That challenge has not appreciably changed in the last 30 years. The “problem” with renewables is hardly a new one, we’ve just been led to believe that it is.)

The only relevant question for the various thermal energy storage options, then, is how they compare to alternatives like advanced batteries, pumped storage hydro and compressed air. The lower the cost of viable options, the sooner they’ll make economic sense, and the lower the barriers will be to greater penetration of new intermittent or nuclear generation. And the fact is that the thermal energy storage options I’ve described are feasible at a small fraction of the cost of alternatives and are capable of delivering the same service. (There are of course many different types of storage services, and neither thermal storage nor advanced battery storage are suited to provide all of them.) You’re wrong about how much energy-shift a typical existing water heater can provide, but it is certainly the case that installing a new water heater kitted out specifically to be able to provided grid-integrated thermal storage (as PJM, the Maritime Provinces in Canada, CAISO, Denmark and BPA, and probably others I’m not immediately award of, are doing even as we speak in pilot programs on their systems) would have even greater capability. Commercial refrigeration coupled with ice storage is already a commercial product and is being installed in markets like Hawaii and Southern California where the economics of the ability to shift electricity demand by a few hours is already becoming economic, at least at the very low cost of end-use thermal energy storage. As the graphs I’m trying to post show rather starkly, the answer to the question of how these thermal storage options compare is, that they are far superior in cost and comparable in performance. Yes they require investment, yes there’s an efficiency penalty, but those are true but thoroughly uninteresting questions in this context. The only interesting question here is whether or not those costs are lower than for the alternatives. The combination of cost, round-trip efficiency and scale of opportunity makes end-use thermal energy storage the clear winner for the foreseeable future.

One more point I overlooked in responding to Schalk’s point on transmission and distribution: In the case of wind, which as I said presents for the most part not a peak demand challenge but an off-peak production challenge, I said that the fact that storage is distributed rather than central station makes little difference to the T&D system. In fact, at least in the case of wind, distributed storage options actually benefit the transmission and distribution system relative to grid-scale storage or storage located at the wind farm, by using (or continuing to use) the wires during low load periods and reducing line losses that would result from shifting delivery to high demand periods.

Michael Hogan's picture
Michael Hogan on July 18, 2014

Grid-integrated storage water heaters have also been in use for decades in a number of rural co-ops in various parts of the US, predominantly in the Midwest. The co-ops often simply gift the water heater to the customer in return for the right to control it remotely, with the commitment, of course, that the customer will never have to endure a cold shower as a result. You’re correct about the use of “night heaters” in many markets as well (in Germany, for instance, where they were installed to help balance the system with the nuclear plants that were added in the 1970s). Cheap natural gas certainly raises the bar for the cost-effectiveness of heat storage, but again, the point here is that all storage options have an economic hurdle to get over, due to the combination of costs (such as the difference between electricity and natural gas as the primary source of energy) and value (from either on-peak/off-peak price spreads or from the value of the ancillary services they can provide). Where naturaly gas is cheap the bar for thermal storage will be higher, but it will still be WAY, WAY lower than it is for batteries, pumped storage hydro or compressed air for the vast majority of storage service applications. And the lower the cost of viable storage options, the faster we can increase the share of intermittent renewables and/or nuclear on the system. Which brings me to your last point – when factoring in the cost of risk, the most economical optino for a non-fossil fuel future is a combination of a portfolio of very-low-carbon technologies, including both nuclear and renewables. There is no point in dredging up the nuclear-vs.-renewables debate here. As your post reminds us, BOTH face system integration challenges, both have big question marks about cost, and both face implementation challenges and risks at meaningful scale. In both cases, however, the balancing challenges can readily addressed at a relatively modest cost using the ample opportunities available for end-use themal energy storage.

Michael Hogan's picture
Michael Hogan on July 18, 2014

Let’s see if that works.

Clayton Handleman's picture
Clayton Handleman on July 18, 2014

 

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Schalk Cloete's picture
Schalk Cloete on July 19, 2014

Michael, from my experience, you have to upload the pictures to some location on the web and then provide the link to that picture. I use my blog for this purpose, but there are many other options for uploading images. 

However, if this is not an option, please send the pictures and any other domumentation you might have on thermal storage to my gmail address: schalk.nr14@gmail.com. As outlined in my comment above, I’d be especially interested in reliable cost and efficiency data of cooling systems relative to similar systems without storage. 

wind smith's picture
wind smith on July 19, 2014

Right. Sorry about the late reply, must have missed the email notice.

What I meant to say is that the battery discharges 0.2kwh/accel or uphill not 0.2kwh/mile driven, since hybrid batteries are only used for extra power/torque for acceleration and hills.

Agreed, my real world experience is not very applicable to gird scale storage, just shows the potential of a battery in this particular application.

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

By far, the easiest way for the grid to benefit from EVs is via nightime charging.  The various permutations of this in your list all can very effectively make the net demand more “baseload”.  

The smarter implementations could help to make the net demand take other shapes too (e.g. shifting towards available solar or wind), but these other load shapes require much more storage, and require the cars to be grid connected at less convenient times of the day.  So I think it’s fair (and important) to say that any given level of implementation will be less effective for these goals compared to the easier baseload.

Gary Tulie's picture
Gary Tulie on July 20, 2014

Easiest, but perhaps not the most effective. It depends on the local situation. 

Where penetration of intermittent wind and solar generation is relatively low, off peak periods will coincide with the night time period so night time charging suits the grid very well.

In areas such as Germany, parts of Australia, and Hawaii levels of solar installation are now such that on sunny days, off peak periods can now occur during the day. Likewise, in Denmark, wind power can generate an off peak period at any time of day or night.

Most vehicles are driven only for a relatively short period of time each day with the biggest journey being the daily commute to work. Suppose a car is parked in the workplace car park from 9am to 5pm, it makes little difference to the owner whether the car is “trickle charged” to achieve a predetermined charge level by home time, or charged at varying rate to flatten out the net impact of solar generation. 

This latter charging pattern can be hugely beneficial in stabilising the grid and allows for charging to be speeded up or interrupted to provide “spinning reserve” as well as enabling peak solar / wind generation to be absorbed without forcing low or even negative wholesale electricity prices.

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

Certainly the system you’ve suggested is technically feasible.  But by effective, I meant to say effective for reducing fossil fuel use (when couple with variable versus baseload non-fossil generation).  Again, asking drivers to plug-in twice per day (instead of just at night), and asking office building owners to install chargers in the parking lots (instead of chargers only being installed at the home of EV owners) is a higher level of implementation.

Geoff Thomas's picture
Geoff Thomas on July 29, 2014

Gary’s comments are great, but I would like to add that many arguments and summations do not really include product knowledge, the most important driver in renewable energy is new products, – as new products develop, new possibilities arrive in design, cost and efficiency.

As an example, it is important to understand that certain lead acid batteries, ie Tubular Positive batteries, can be cycled down to 80% per day, and even 100% (approx 100 times.)

This expands design possibilities, particularly given that lead acid batteries have a theoretical 100% discharge of 1500 cycles, 3000 at 50% etc, and efficiencies of around 98%, which compares very favourably to the 80% of Lithium.

Then again there may be Lithium configurations that do not get so hot, but data is not presented.

Gary has argued correctly, but the contrary arguments do not take into account the development in Lead Acid, by far the cheapest, and with much higher cycle rates, I believe that these analyses that one sees comparing this sort of battery with that should take a look at the best of Lead Acid before looking at the best (and most expensive) of the Lithium and then comparing apples with apples.

Cheers,

Geoff.

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