Storing energy

  1. Tesla Powerwalls vastly too expensive
  2. But isn’t South Australia buying Tesla Powerwalls?
  3. Huge pumped hydro ‘batteries’ cheaper, but still too expensive
  4. Building enough storage costs so much energy it reduces the energy return of wind and solar
  5. But Amory Lovins says a smart grid doesn’t NEED storage?
  6. Storing energy for peaking power
  7. Gravel batteries

1. Tesla Powerwalls vastly too expensive

The Tesla Powerwall is not going to change things much according to The Breakthrough, and here’s why:


Unless storing energy becomes orders of magnitude cheaper, it cannot save 100% wind and solar scenarios. Seasonal variations in wind and solar output can require weeks of storage. But when we try to store real power for more than a single day, it gets vastly too expensive to be worthwhile. When reading about the various costs of storage below, keep in mind that if we were to put today’s nukes up on the assembly line and build heaps of them, their costs could easily come down to around $2 billion per GW. (These prices are already being achieved outside of America’s terrible legislative environment and the UK’s infamously terrible Hinkley point project.)  I’ve even seen IFR and MSR projections for half that, but let’s go with $2 billion per GW for now.

Tesla Powerwall’s have been sold as the band-aid for intermittent, unreliable renewables. But are up to the job? Eco-modernists have analysed it, and remain dismayed. Their figures show that if wind and solar provided just a third of Germany’s grid, and they tried to store 1 week for winter, you could replace the entire grid with nuclear power. (Note: German winters crash renewable output for weeks at a time!) The choice?

Store just a third of the German grid for a week, or nuke the entire grid for 60 years!

It gets far worse. That one third benchmark ends with the punchline that they could supply all their electricity with nuclear power. But 100% renewables would do it 3 times over, andGerman winters cut renewables for many weeks at a time, making storage 6 to 12 times as much as nuking the entire grid!

Remember, that does not even include buying and maintaining the wind and solar farms in the first place!

2. But isn’t South Australia buying Tesla Powerwalls


I don’t get it. Say we take Elon Musk’s price of $250 / kilowatt-hour for the capital cost of his battery system. (There’s good reason to think it might be $500 to $600 per Kwh!)

Let’s compare it to a 1 gigawatt nuclear power plant. $250 / kilowatt hour storage is one millionth of the output of a GIGAwatt power plant. So to scale up to one gigawatt, multiply the cost by a million which is $250 MILLION! But we can’t stop there, the figure is $250 million for just 1 hour of output at 1 Gigawatt.
A battery that can store about 16 hours (as solar PV only works about a third of a day) would be 16 * $250M = $4 BILLION dollars to store just 16 hours power of a 1 Gigawatt power plant. That’s not all. You haven’t built the power source yet, this is just the battery! You’ve still got to build all the wind and solar you need to charge this beast. Remember the rough rule of 3. You’ve got to build at least 3 times the power you need (in this case 3 GIGS of wind and solar) so that 1 lot can run your town during the day, and the other 2/3rd’s can charge the batteries for night time. Add in some cloudy weather forecasting and you might actually have to overbuild your wind and solar by 4 or even 5 times to be sure!

Then there’s another problem. These batteries might only last 12 years, but nuclear power plants can last 60 years. So you’ve got to multiply that $4 billion by 5, bringing it up to $20 billion, just for batteries. (You still haven’t built the solar and wind farms yet!) And this is based on Elon’s battery only price of $250 / kwh, not the full $500 to $600 per kwh that Forbes thinks is more likely given cooling and other infrastructure costs. But despite American nuclear being legislated into oblivion, there are good examples around the world that show nuclear power could be built for $3 billion, maybe even $2 billion per GW.

A nuke will run all day and all night, no matter the time of year. We are still so, so far from anything being a ‘saviour’ for unreliable wind and solar energy. In contrast, there are future projections for various modular breeder reactors that eat nuclear waste to come off the line at about $1 billion / GW.

3. Huge pumped hydro ‘batteries’ cheaper, but still too expensive

Normal giant hydroelectricity dams have all sorts of problems associated with them.

We are running out of suitable sites. Humanity has already used most rivers and many no longer even make it to the sea. Massive freshwater dams also threaten migratory and spawning cycles with many freshwater fish. River ecosystems are under threat everywhere we look, and more hydro dams will only add to extinction pressures on fish and river ecosystems already in danger. In summary, there are already too many people using too much river water too fast.

But instead of traditional rivers for hydro-power generation, what about using pumped seawater for hydro-power storage. Just build a hydro dam anywhere there is an elevated plateau next to the ocean, and pump the seawater up into the dam when you have excess renewable energy, then open the floodgates and let it rip when the renewables die down again. It’s a giant hydro-power battery.

At first it sounds great! South Australia has hundreds of kilometres of coastal cliffs, and plenty of desert in which to build seawater hydro dams without hurting our last, fragile rivers. The only disadvantage is that it would be power storage, not a power source. This beast is a battery only, and has to be ‘charged up’ by pumping water up the 90 meter cliffs of the Nullarbor.

One vast 7km diameter dam would run the whole of Australia for 10 hours! The problem? Expense. This might be cheaper per unit than other methods of storing energy, but how do you get it across the whole continent? Here come the costs.

“Optimisation of a renewable energy power system and electricity”
Storage by means of pumped seawater hydro, Submission to ACRE 23/12/2010
Professor Peter Seligman, DEng. PDF here: sub982_attach

Pages 6 – 8 show the costs: Storage pond = $2 billion, 20 huge turbines & pipes = $33 billion, wiring it all up with a new DC super-grid across the bottom of Australia = $20 billion, which is also required by the renewable energy projects themselves. Remember we still have to bring electricity from the sunny deserts and windy coasts to where the people live. That’s $55 billion for 10 hours storage for all of AustraliaBut at $2 billion per GW nuclear power, we could nuke nearly half our grid for that! The Australian Energy Regulator shows us to be around 50 GW. What do you want to do?

Store just 10 hours, or nuke half the Aussie grid for 60 years?

Building enough storage costs so much energy it reduces the energy return of wind and solar

One of the great questions about any energy system is how much energy do you get back after all the energy it took to actually make your power plant or wind turbine? This is called  ERoEI (Energy Return on Energy Invested), which takes the energy returned and divides it by the cost of building the thing in the first place!

Most renewables have good ERoEI’s on face value. But here’s the thing. These papers always ignore energy cost of building the storage required by wind and solar. That’s a major problem when trying to assess the Energy Return of an energy system that is mostly OFF! Sadly, when we include energy storage costs, the actual energy profit drops off a cliff.  Solar PV is not even an energy source, wind only returns 3 times the energy it took to make the turbines and the energy storage (like pumped hydro dams), and solar thermal is the highest at 9Our civilisation requires an ERoEI of at least 12.

4. But Amory Lovins says a smart grid doesn’t NEED storage?

Amory Lovins is just plain smug in this next presentation. There’s something seductive about his confidence (or is that arrogance?) I wish I could sit back, unplug all my questions, and ‘believe’. Watch him be smug about the cheap price of wind and solar — when we’ve just seen that it hurts the utilities that carry us through the night. Watch him be smug about baseload power plants having 90% capacity factors (only requiring one ‘spare’ plant for every 4 or 5 other baseload plants) — when wind only has 35% to 40% capacity factors, requiring vastly more storage! Listen to him smugly ignore capacity factors as he states “The grid handles this intermittence by backing up failed plants with working plants!” Yup, and so he just avoids the vastly different ratio of backup between baseload plants and wind. There’s a huge difference between one nuclear plant going down and an entire continent’s wind going down! (See graphic above for Europe). Watch him be dismissive about huge drops in wind  — simply because we can see it coming, which does not actually solve the storage cost and EROEI problem!

Watch him directly contradict another NREL study (Page 10 here) that concludes baseload power is essential if we want to wean off oil and onto electric cars. The NREL study concluded that America could charge most of their light family cars and trucks and buses — essentially most of their gasoline (petroleum) — if we turn every baseload plant up to full, especially overnight! That’s amazing. That’s the gasoline half of oil replaced with today’s grid and power plants! (Diesel for heavy trucking, mining, and farming is the other half of oil, and requires other solutions). This makes me wonder about NREL. Amory Lovins claims their modelling says no baseload plants are required. (2 minutes in). Their electric car study claims baseload is ESSENTIAL, TURN IT UP TO FULL! What gives? This kind of inconsistency should alarm us all. It points to the influence of ideology at work, not hard nosed engineering and maths.

Watch him smugly assert that renewables are going to charge electric cars that are then going to backup the grid rather than — I don’t know — use that power to drive!!! 

5. Storing energy for peaking power

If we build nuclear power stations which are 90% reliable (baseload) power, then we will only require a tiny fraction of the power storage otherwise required by intermittent renewable energy. However, in some rare circumstances it may be cheaper to store power from nuclear power stations for peaking purposes. Peak demand usually refers to how we meet the late afternoon peak in demand, as some industry is still running, air-conditioners blast away, and people start cooking. In the future we will also have workers coming home from and plugging in their electric vehicles into the grid, placing additional power requirements on the grid. As the wiki says:

Peak demand, peak load or on-peak are terms used in energy demand management describing a period in which electrical power is expected to be provided for a sustained period at a significantly higher than average supply level. Peak demand fluctuations may occur on daily, monthly, seasonal and yearly cycles. For an electric utility company, the actual point of peak demand is a single half hour or hourly period which represents the highest point of customer consumption of electricity.


Peak demand is considered to be the opposite to off-peak hours when power demand is usually low.

There are off-peak time-of-use (TOU) rates.

So we either build a few additional power plants known as peaking power plants which can be ramped up really fast (usually natural gas) to meet this demand, or look for ways to store power that can be dished out quickly at an industrial scale. There is still a market for storage for these purposes, but it has got to be compared to reliable clean nuclear power when we do so.

6. Gravel batteries

Now this is interesting! IF this system works as advertised, this could prove to be a very useful energy storage mechanism, but again not cheap enough to replace baseload power.

Isentopic claims its gravel-based battery would be able to store equivalent amounts of energy but use less space and be cheaper to set up. Its system consists of two silos filled with a pulverised rock such as gravel. Electricity would be used to heat and pressurise argon gas that is then fed into one of the silos. By the time the gas leaves the chamber, it has cooled to ambient temperature but the gravel itself is heated to 500C.

After leaving the silo, the argon is then fed into the second silo, where it expands back to normal atmospheric pressure. This process acts like a giant refrigerator, causing the gas (and rock) temperature inside the second chamber to drop to -160C. The electrical energy generated originally by the wind turbines originally is stored as a temperature difference between the two rock-filled silos. To release the energy, the cycle is reversed, and as the energy passes from hot to cold it powers a generator that makes electricity.

Isentropic claims a round-trip energy efficiency of up to 80% and, because gravel is cheap, the cost of a system per kilowatt-hour of storage would be between $10 and $55.

Howes says that the energy in the hot silo (which is insulated) can easily be stored for extended periods of time – by his calculations, a silo that stood 50m tall and was 50m in diameter would lose only half of its energy through its walls if left alone for three years.

via Giant gravel batteries could make renewable energy more reliable | Environment |

What does all this mean in terms of the size of plants and how much it will cost?

Professor Barry Brooks reviews it saying:

eclipsenow, I hope it works out – sounds interesting in principle and the energy density doesn’t look too bad. From the figures given, 540 cubic metres stores 16 MWh of energy, or 30 kWh per cubic metre. To store one day of output of a 1 GW power station would require 1,500 of those 7m tall, 7 m diameter twin silos. Let say you stacked them in a 15 x 15 m square (for each silo), that would require about 1 square km of silos (ignoring interconnections and local generators etc.) Could be useful for storing cheap baseload nuclear-generated electricity for peaking purposes.

…and then…

$/kW is generating capacity (peak, in the case of wind), whereas $/kWh is energy storage. To store 1 day of energy from a 1 GW power plant requires 24 million kWh. At $55 per unit, that’s a storage cost of $1.3 billion for 24 hours of storage. Not ridiculously expensive by any means, but neither is it cheap as chips as you might have thought it to be, given the implicit comparison you made above. I’ve used the upper price figure cited, since we’ve not even seen a demonstration unit yet.

Regarding rise in steel and concrete prices, these will effect the cost of renewables at least 10 times more than nuclear power, see:

In other words, it costs $1.3 billion to STORE just 24 hours of a 1GW nuclear plant, when future MSR’s might come down to anywhere from $2 to $4 billion to BUY and they’ll run for 60 to 70 years!

2 Responses to Storing energy

  1. prkralex says:

    Technology to create heat using abundant solar energy stored in rivers, lakes, reservoirs and the sea is something that UK terms it as game changer. I think this is something all countries should look at as it can give a new avenue of renewable energy source.

  2. Eclipse Now says:

    Hi Prkralex,
    I’m aware of solar thermal. Professor Barry Brook, head of climate at Adelaide University, and Dr James Hansen both support nuclear power given renewable’s unreliable, dispersed, fundamentally problematic power supply. As Barry’s blog documents:
    The amount of concrete, steel, and land used by solar thermal to nuclear is:
    “Concrete = 15 : 1; Steel = 75 : 1; Land = 2,530 : 1”

    Solar thermal uses way too much stuff, costs too much, and delivers too little in terms of baseload power.

    Now get this for cost. A good GenIV, waste eating nuke could come in at around $4 to $5 billion / gig, depending on assumptions for mass production. Check out solar thermal on a cost per gigawatt supply.

    “Precise construction costs are hard to come by, but it seems to have been about €300 million ($AUD 500 million). This works out to be $25 billion per GWe of average power, but this is clearly a first-of-a-kind cost that can be expected to fall with replicated builds. The levelised cost of energy (including the energy storage) is estimated to be 45 c/kWh (in Australian cents) — which is about the size of the Spanish feed-in tariff which is set to run for 25 years. Including its charge for electricity to customers, the maximum cost has been capped at 58 c/kWh.”

    Just because it is *technically* possible to imagine renewables being baseload, doesn’t mean they are *economically* possible.

    Don’t get me wrong: if some kid in a lab invents a new super-cheap super-strong super-battery, I’ll be the first to rush out and buy a complete off grid system… if solar PV prices continue to drop. But right now? If we’re being honest? Dick Smith has calculated that for the average Australian home solar PV would cost 4 times as much. (1 lot of solar for daytime use + 3 lots of solar to charge the whopping great battery for the 3 parts of the day solar pv doesn’t work = average of 4 times as expensive amortised over the lifetime of the products).

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