Saturday, February 22, 2014

Distributed energy storage

Tom Murphy thinks energy storage for a mostly solar- and wind-powered grid would be impractically large
Putting the pieces together, our national battery occupies a volume of 4.4 billion cubic meters, equivalent to a cube 1.6 km (one mile) on a side. The size in itself is not a problem: we’d naturally break up the battery and distribute it around the country. This battery would demand 5 trillion kg (5 billion tons) of lead.
 The figures he uses to get there:
Let’s also plan ahead and have all of our country’s energy needs met by this system: transportation, heating, industry, etc. The rate at which we currently use energy in all forms in the U.S. is 3 TW. If we transition everything to electricity, we can get by with 2 TW, assuming no growth in demand. Why? Because we currently use two-thirds of our energy supply (or 2 TW) to run heat engines, getting only about 0.6 TW out for useful purposes in the bargain. An electrical system could deliver this same 0.6 TW for only 1 TW of input, considering storage and transmission efficiencies.
Running a 2 TW electrified country for 7 days requires 336 billion kWh of storage.  We could also use nuclear power as a baseload to offset a significant portion of the need for storage—perhaps chopping the need in two. This post deals with the narrower topic of what it would take to implement a full-scale renewable-energy battery. Scale the result as you see fit.
This raises the question, if you have converted all transportation to run on electricity, how much of the storage requirement can be met by those batteries alone?

There are 254.4 million registered passenger vehicles in the United States. There are also several million commercial trucks and bus that are significantly larger than your average passenger vehicle. I'm going to count them as several "passenger-vehicle equivalents" and round that number to 300 million. Assume they are driven about 4 hours a day, and otherwise available to the grid, and give each one of Tesla's 85kWh batteries:

85 * (3*10^9) * (5/6) = 21.25 billion kWh.

So you could meet about 7% of the week's worth of power Mr. (Dr.?) Murphy estimates we might need (there's no point in being falsely precise in an exercise like this.) However the numbers look better if we make the scenario a little more realistic; for example, if we presume about 40% of the normal load will be baseload power -- about what a smart grid is thought to require to be stable. We can meet this through a combination of hydro, geothermal, nuclear, tidal, and/or space-based solar.

We should also suppose a dynamic pricing model for electricity, something the UK is already experimenting with. When solar are wind farms are idle, power costs more, reducing consumption. It seems likely that you could reduce energy consumption by a fair amount by this method -- 35% perhaps.

Now, in our nightmare scenario of unending darkness and perfectly becalmed winds, we have 35% of demand met by conservation, 40% by baseload power, leaving 25% to be covered by batteries. That's still more than we have, so let's add some hydroelectric storage.

In investigating the potential of hydroelectric storage -- no mean feat, when existing hydro storage plants tend to be rated by output (MW) not total storage (MW hours) I found myself right back with Tom Murphy:
The U.S. has 78 GW of hydroelectric capacity installed. In a year, these plants produce 272 TWh. Divide by 8766 hours in a year, and we find 0.031 TW (31 GW) of average power. This implies a 40% capacity factor.
In this post he is looking at hydroelectricity's potential as a power source, rather than as a form of storage, but let's borrow the numbers.
When we built things

We can suppose that most of the convenient sites where a large amount of water can flow abruptly downwards are occupied by these sites. We can further presume that if we can control the flow of water downwards, we can also, with the necessary infrastructure, pump the water upwards.

The potential of the dams for storage would reflect the amount of time we could run them at full capacity (78GW) instead of average capacity (31GW) presuming we were using intermittent renewables to "top off" the dam reservoir. Let's say, in the spirit of Fermi estimation, that that time is one week. That would give us a major boost to our storage capacity:

(78GW - 31GW) = 47GW
47GW * 24 hours = 1128 GW-h
1128 GW-h = 1,128,000,000 kW-h * 7 days
7.896 billion kW-h

So that puts us at 29.146 billion kW-h. Note that this is not a hard upper limit; reservoirs can be created artificially near the sea and energy stored via pumped sea water. But that's probably not necessary, because . . .

The Strategic Petroleum Reserve has a capacity of 727 million barrels (30.5 billion gallons, 115.4 billion liters). Let's fill that with biodiesel, which has a specific energy of about 35MJ/liter. That would provide a reserve of 115.4 billion * 35MJ = 4 trillion MJ. That's 1.1 trillion kW-h.

Now we have about 16 weeks of stored energy based upon the assumptions above (40% baseload power, 35% drop in consumption secondary to dynamic pricing) or almost four weeks based on Dr Murphy's pessimistic scenario (no adaptive drop in consumption, absolutely no baseload power, not even the 10% of our electrical supply currently provided by hydroelectric dams.

That's almost excessive, but we can trim it down by using imported sugarcane ethanol from Brazil, to give us one of the cleanest biofuels in the world (remember, we are not using this for everyday consumption, but rather as an emergency reserve, so we can acquire it gradually over time.) Ethanol is a little better than half as energy dense as biodiesel, which still gives us a nice margin under either set of assumptions.

So there you have it. Do we need billions of tons of lead to acquire the infrastructure to store a week's worth of energy? No, in fact we have it already!


  1. Given that there is neither a scientific nor a logical basis for curbing CO2 emissions ( ), why spend a lot of money on distributed energy storage?

    1. Terry, to people who are not scientifically and technically illiterate, there is every reason to cut CO2 emissions.

      I suggest you seek to overcome the ignorance that afflicts you -- ignoring incompetent clowns like Watts & Co and learning the basic science of climate change would be a good place to start.

      I wish you luck!

  2. TheTracker:

    Thank you for taking the time to respond. In your response you do not address the issue that I've raised with you but attempt to substitute me for this issue. This is an example of an ad hominem argument. It is well known that such an argument is illogical.

    1. You failed to make any case for your extraordinary (and extraordinarily mistaken) assertion that "there is neither a scientific nor a logical basis for curbing CO2 emissions." Hence, there is no case for me to answer. Obviously, citing a known serial fabricator like Watts does you no help.

      I diagnosed the fact of your ignorance not to refute an argument you never successfully formulated, but to offer you guidance in becoming informed about the subject you are pontificating upon. After all, ignorance is nothing to be ashamed of if you are willing to do the work to correct the situation.

    2. My case is made in the peer-reviewed article at ; this article is cited in my testimony to the EPA. The case that you've made thus is thus far is a logically vacuous example of argument by assertion.

    3. In my previous post, please strike the phrase "thus is thus far" and replace it with "thus far."

  3. "The case that you've made thus is thus far is a logically vacuous example of argument by assertion."

    Again, I don't have a case to make. You're denying basic facts about the physical world; you have a case to make.

    Right now, you're playing the classic denier game of weaponized ignorance: Show up, say something scientifically illiterate, provide no evidence and demand that your opponent give you a free education. Not interested.

    To make a case, you need to follow these steps:

    1. State why specifically you feel "there is neither a scientific nor a logical basis for curbing CO2 emissions." Describe what part of the broad consensus among scientists and economists you have disproved.

    2. State the evidence for your argument specifically, from credible sources, and explain why you think it supports your position.

    I engage pretty freely with deniers, but no, I'm not going to click on a random think to a paper and try and determine from it the exact shape of your delusion.

    Make a case, if you have a case to make. I don't have to argue settled science with you; if I chose to spend some of my valuable time educating you, don't think I'm going to relieve you of your burden of proof.

  4. Also, Terry? Would this be the argument that got eviscerated here: ? 'Cause I really don't think beating that dead horse is going to go well.

  5. TheTracker (Feb. 28 at 7:45 pm):

    I make my case by the peer-reviewed article that you refuse to read. Can you refute the argument that I make in this article? One cannot know the answer for, as you admit, you do not know what this argument is!

    Replacing a logically legitimate counter argument from you is an argument of the form:

    Premise: TheTracker is right
    Conclusion: TheTracker's opponent is wrong.

    I claim that the premise to this argument, that you are right, is refuted by the peer-reviewed article which you refuse to read. Like the proverbial ostrich with head in sand, you deal with this challenge to your thinking through refusal to think.

    1. You need to articulate your case here in a way that allows me to justify clicking on a link you provide. As of now, you have made no coherent argument in support of your assertion. I explained the steps you need to undertake. Feel free to include the abstract in your response.

  6. TheTracker ( Feb. 28 at 7:57 PM):

    My argument was not "eviscerated" through the debate at ? This debate was aborted on specious grounds by its moderator.

    Arguments incorporating the equivocation fallacy remain active in climatological arguments. I'll supply examples from your own blog at your request.

    1. It's unfortunately that you learned nothing from that experience. Multiple patient people explained to you how you were misunderstanding the equivocation fallacy, whilst simultaneously indulging in verbose and, ironically, highly vague and ill-defined lectures so incoherent they verged upon a word salad.

      You failed there, totally and completely, long before you were Mercy Ruled by the mods. Don't repeat that failure here. Come with a better argument, and real evidence. Good luck.

  7. Utility grade batteries are what you need to be looking into.

    I've been actively following Ambri liquid metal batteries;

    A shipping container is 2MWh;

    The downside with most storage methods is that they drive up the cost of electricity delivered, that's no small matter. (optimistic $0.05 per kwh)

    Solar PV currently costs $0.20 per kwh in Canada. (No... its not sunny.) Obviously its a lot less in utility grade formats. Overall its entirely affordable to roll out now.

    Solar is a disruptive market event for existing utilities. It provides when the market has the greatest demand, and using it, essentially drives up the cost of for fossil fuels which are no longer needed and on stand by.

    Give this a good long read, the paper from a conservative think tank is particularly funny.

    We haven't even gotten into the downtime for fossil fuels. Coal Plants are down 13% of the time for repairs and maintenance. So, if you want one more plant, you should probably build 2.... (that -100% for one plant going down is a serious issue) By comparison, if you drop 13% of your wind turbines or solar panels, that is all you dropped.

    Last but not least is that supply is predictable. We know long in advance about how much power will be provided and when. By comparison we have no idea about demand or when it will spike. That is the reason we need batteries, or in fossil speak, spare 500MW plants running and on line.

    The other way to look at all this is that we can use fossil fuels as our batteries until we phase them out.

    1. Using Tom Murphy numbers of 336 billion kwh, you'd need 168,000 Ambri shipping containers distributed over the power grid. (Note: This means remote towns can now have backups without needing a coal power plant next door.)

      "More than 6 million cargo containers enter U.S. seaports annually..."

      Estimates for number of containers in the US are 9 - 60 million. (Lots but I have no real clue. :-) )

      PS... I usually post by the name AnOilMan. I work in oil and gas.

  8. I am always searching for informative information like this. Thanks for sharing with panels for schools

  9. How much lithium would be required to make the 300 million 85kWh batteries? If we consider replacement rates, is this a sustainable future?