Storing energy

  1. Storing energy to back up intermittent renewables
  2. The Nullarbor hydro dam idea could run all Australia for 10 hours!
  3. Storing energy for peaking power
  4. Gravel batteries could store energy for 3 years!
  5. Wind Balloon storage
  6. Energy storage groups

1.Storing energy to back up intermittent renewables

Unless the storage technology becomes orders of magnitude cheaper, I don’t think storage can really help save the day. The issue is that once one tries to store up more than a day of power for the grid the whole exercise becomes so expensive that we could build a nuclear power plant instead that would run all day every day, not just a few desperate days of low renewable power each year!

This is really drummed home in the Gravel-battery study below.

2. The Nullarbor hydro dam idea could run all Australia for 10 hours!

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 expenses!


“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
I stored his free 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.

So there’s $55 billion, which would build maybe 11 AP1000’s (or more if they go on the production line in China!) which could work for the next 60 to 80 years. Not only that, we could just plug them into the existing grid, saving the $20 billion lost on a DC super-grid.

3. Storing energy for peaking power

The media is full of stories about breakthroughs in storing energy mainly because everyone knows the wind stops blowing and the sun stops shining! Even though some wind farms produce power cheaper than coal, when the fact that it is intermittent is costed in, with all the required backups, energy storage systems, and alterations to the exiting grid to upgrade it to a ‘smart grid’ capable of handling renewable energy are all factored in, it could end up costing as much as 10 times a simple nuclear grid!

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. Sadly, natural gas is of course a fossil fuel, and so we are aiming to avoid that. (It is also not far off it’s world geological peak, which means it will become too expensive in some countries to provide peaking power this way. Fortunately for Australia’s economy we have lots of natural gas left, but unfortunately for the world, this will not help us solve global warming).

4. Gravel batteries could store energy for 3 years

Now this is interesting! IF this system works as advertised, this could prove to be a very useful energy storage mechanism.

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 later

$/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:

5. Wind-balloon storage

A new contender against nuclear?

Wind energy – storing the power

There are two big problems with wind turbines. One is cost. The other is the variable nature of wind. It doesn’t always blow when there is demand for power. So storage of generated power is vital if wind power is to become widespread. Seamus Garvey has been working on these problems and is speaking to Annette Langbehn.

via Wind energy – storing the power – Science Show – 17 July 2010.

The basic outline:

  • A new approach for wind: these wind turbines will float far off the coast and not be visible from land.
  • They will compress air, not generate electricity.
  • The compressed air is stored in large rubber balloons deep under water, about the size of your house.
  • These balloons use the pressure of deeper sea water to maximise the pressure that the air is stored at, making the rubber materials cheaper than trying to store all that air in steel strong enough to take compressed air on land.
  • With good wind, the turbines blow the compressed air straight into generating electricity. When the wind is low, the balloons take over supplying the compressed air to move the turbines.
  • It’s cheaper than any storage so far: Batteries are at about $500 thousand per mWh, Pumped hydro is about $80 thousand per mWh of storage, but these compressed balloons are only about $1 thousand per mWh!
  • Claims that the whole UK could run on wind without Brits even seeing the turbines because they are all so far off-shore!

My comments:

  • It’s a long way from being commercialised. The first balloon is only 1.8 meters across, the quarter scale balloon is later this year, and a full scale balloon will be tested next year in 2011.
  • Seamus admits that wind will have to store about a day of power: but even he admits that the winter wind can die down for about 3 days straight.
  • But where does this leave our nuclear campaign?
  • As I always answer: we have to start deploying reliable base-load clean energy now, not in 10 or 15 years when the kinks and quirks of some new technology might have been ironed out.
  • In GenIII nuclear plants we have a demonstrated technology that can keep the lights on and our electric cars running as peak oil and global warming hit. These will generate waste to fuel the soon to be released GenIV reactors that we know work, but are yet to be fully deployed at a commercial scale.
  • Are people really so frightened of safe, clean, cheap nuclear power that they’d have us gamble with catastrophic climate change? Do they really want us to delay solving climate change on the whimsy and rumour that the many expensive problems with unreliable renewables will one day be fixed? Do they really think reality will just bend to their whims and wishes? They’re kidding themselves if they are.
  • FINALLY, if this new compressed air wind turbine does prove more reliable and cheaper than nuclear power, no one will be happier than myself! We can save our uranium for a moon or Mars base.
  • I would be glad to announce that renewable energy could finally do the job!
  • But until I read a broad scientific consensus that a new individual renewable generator could reliably provide ample cheap base-load power, I’m not budging. I’m no longer convinced that we can rely on a grid where ‘a bit of wind at one time and a bit of solar at another will do the job’. We need power that we can rely on whatever the time of day or night, whatever the weather, and whatever the season. Today’s renewables just cannot do that!

6. Other energy storage groups

Local grids may require some energy storage, but thanks to I have the following list of organisations working on solving that problem.

Sandia National Laboratory: Energy Storage Systems
The Energy Storage Systems (ESS) Research Program develops advanced energy storage technologies and systems.

Distributed Energy Program: Compressed Air Energy Storage
For information on compressed air energy storage, provided by DOE’s Energy Efficiency and Renewable energy Nework

IEA ECES: Homepage
Further information on energy storage – reasons, techniques and success stories.

Research – Energy – The future potential of energy storage
The latest information by the European Commission on energy storage systems.
Click here for EC energy homepage.

Energy Storage Council
The ESC promotes the research, development, and deployment of storage technologies in America.

The Trade Show at WIREC (American Renewables)
Learn more about the largest business conference and exposition ever held on renewable energy in the U.S. on March 4-6, 2008.

Electricity Storage Association – energy storage, energy providers
A trade association established to foster development and commercialisation of energy storage technologies.

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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