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April 18, 2008



According to the US census, the US has about 126,000,000 households (http://quickfacts.census.gov/qfd/states/00000.html)

If 10 billion can supply 1 million homes, then 126 times that could supply all the homes in the US.

If my rough calculation is correct, you make a big step in the direction of energy independence for 1.26 trillion. How much has Iraq cost?

Kit P

“- the equivalent of building two commercial scale nuclear power plants -”

If you had 4000 MW of single cycle gas turbines to go with the 4000 MW of wind, it would be the equivalent in 4000 MW of nukes.

Mat, the US has achieved energy independence for making electricity. Nuke and coal plants built in the 70s & 80s replaced almost all oil fired plants. A small but increasing percentage is coming from oil and LNG imports.

If you would like to debate if the world was better place with SH running Iraq and building lots of windmills would US will get war criminal to change their ways, go for it.

Bob Wallace

It's not just combining wind, thermal solar, and geothermal, but also all the other potential contributers to our future power system that need to be connected.

Include tidal, wave, biogas (farming and municipal waste), hydro and things which we might not have yet imagined.

We're in the very early stages of learning how best to pull usable energy from these sources, but it might not be too early to begin thinking about a unifying grid. The more we tie divergent sources together, the less we need to create storage to make up for the periodicity of any one system or locale.

A high voltage direct current (HVDC) grid running from the tidal/wind power rich coast to tidal/wind power rich coast would stretch 3,000 miles or so. At a million dollars a mile we're looking at a fraction of what we spend a year in Iraq.

Additionally, along with learning how to extract electricity from natural sources we are rapidly learning how to power our vehicles with electricity. That will be both a problem and a blessing for the grid. PHEVs and BEVs will require more energy generation but will add significant short term storage to the grid.

And moving away from petroleum for our transportation will reduce the temptation to use our military in an attempt to seize oil from others in the future.

Wouldn't that be a huge savings of precious tax dollars?

David Walters

"4000 MWs"...not!

Pickens is intersted in the absolutely free gov't hand out for wind that is being offerered. There is virtually no return on the money invested from selling it on the market.

A 4,000 MWs wind farm runs 20% of the time (US onshore average). The $10 Billion dollars which if divided by MWs comes out to about $2.5 million per then, if scaled upward based on ACTUAL MWs produced (multiply by 5 for capacity) comes out to about $12 million dollars per MW installed. With Texas prices averaging $20/MWhr, exactly how long does it take to pay off this cost?

A nuclear/geothermal/hydro/coal or NG plant would, if billed at 4,000 MWs would infact produced at least 90% of this.

David Walters


Gee, a national grid will obviously require a lead integrator contractor. Would that be Boeing, Lockheed-Martin, General Dynamics, or Northrup/EADS? (Tee-Hee....)


"A 4,000 MWs wind farm runs 20% of the time (US onshore average)"

But is that the average for this specific site in Texas? Probably not. You can't base your math on the average for all of the United States. How do you know the wind doesn't blow 60% or 70% of the time at this site?

No one plunks down $10 billion without doing their homework, especially not an oil man. There are easier ways to get money than by spending $10 billion dollars and scamming the government as you suggest.

Tom G

I love this site and get my daily energy fix from it. After working for 20+ years in the energy field I agree with almost all of the comments here. What I really like to see are individuals who make a statement [either for or against something] and then offer an alternative or suggestion for improvement. If we just criticize and condemn change will be hard to achieve. So here is my suggestion.

We need to start thinking about how many people the planet can support. Is 2 billion too many? Can we support 8 billion? Currently we have about 300+ million in the U.S. and we are struggling to maintain our food, fuel and life style. And yes we are growing our U.S. population faster than we can support it. We reward individuals who have large families by giving them tax deductions so they will have even more children. So here is my recommendation. We need to eliminate any tax incentive for families larger than the population replacement number. I am not a social scientist but I think the number is about 2.1 children per female. If we do not we will surely eat and drive our selves into starvation. The plan would be something like this: Each family can have a many children as they want. If you have 1 child you get a deduction. If you have 2 you get 2 deductions. If you have 3 you give up 1 deduction. If you have 4 kids you give up all deductions. If you have 5 kids you are charged a monthly natural resource recovery fee.

As a society every item we use; cars, boats, diapers, tires, electric heat pumps, tractor fuel; almost everything has a kilowatt or energy and environmental cost. There will come a time when either we can not produce enough of something or the environment will not forgive some of our mistakes.

Bob Wallace

Birth rate is not a problem of the developed world. High birth rates are happening in the least developed places.


If I am recalling the data correctly, US birth rate would be below replacement level were it not for first generation Americans generally high birth rate.

(And before the conversation goes there, we need new Americans from the outside to supply our workforce as our 'born here' population ages.)

Here in the US we need (IMHO) to get our energy usage under control via conservation and sustainable generation.

We are extreme energy hogs.


I think we need to be a bit more careful with units. Peak versus average power for varying sources is one source of confusion and error. Another is the press propensity to use enough to power XX homes. First they usually don't differentiate between peak and average power. Secondly homes are far from the only source of electrical demand in the US. Industrial, and commercial users each consume roughly similar amounts of power. It is all too easy for a reader to get the impression of X amount of renewable peak will cover all the needs of the country, when in fact it may only cover the needs of housing, part of the time.

Tom G.

I went to Wikipedia and looked up the data. The list contains 222 countries. The U.S. is number 126; 125 have more population growth, 96 have less population growth. However population growth of a country is not just about female birthrates. In the U.S. we have been allowing or encouraging the immigration [depending on the term you prefer to use] of millions. All of these millions want food, clothing, cars, kids and a better life which is of course fine and we call that the American dream. I think it's sad but not everyone is going to achieve the dream unless we change our ways.

I agree we are extreme energy hogs and need to do a much better job of conservation. But it is very difficult to change individual behaviors. The last time I drove on a California freeway the average speed was between 75 and 85 mph. The last time I went to Phoenix they still didn't have white roofs on their houses to reduce cooling costs/energy consumption. The last time I spoke to some of my friends who are farmers in the mid-west I asked them how many were making their own bio-diesel from used cooking grease - none were; however If my sampling was larger I am sure some would be.

I just watched a TV show called the "Human Footprint" on the National Graphic channel which was a real eye opener. You can not believe how many natural resources it takes just to get a child raised up to the age of 2. What's the old saying; we are 5% of the population but use 25% of all resources on the planet.

Charles Barton

How do you know the wind doesn't blow 60% or 70% of the time at this site? - Rip

Ripe find me a Texas site in the Wind Resource Atlas of the United States where the wind blows 60% or 70% of the time.
Even better find me a site in Texas where the capacity factor for wind is better in the summer than in the winter, or where the strong summer winds provide lots of electricity of Texas Air Conditioners on hot summer days. T, Boone Pickins knows the value of a government handout when he sees one.


Hey...I think David Walter's and my posts got mixed up. All I know about wind in Texas is that it blows.

Cyril R.

T, Boone Pickins knows the value of a government handout when he sees one.

Cyril R. knows a nuclear propagandist when he sees one.

ike solem

The real question here is whether or not this wind project will replace existing coal generation. T. Boone Pickens has a long history in the oil industry, and it is encouraging to see oil interests getting into the electricity generation business using renewable energy strategies (they certainly have enough cash to get involved at the ground level).

There is a huge struggle right now over the energy direction the U.S. will take.

On one side are porponents of coal and crude oil from Canadian tar sands, Venezuelan heavy sulfurous crude, Rocky Mountain oil shales, and imported liquified natural gas.

On the other are proponents of long-term clean energy strategies, the most promising being solar and wind, followed by biofuels and nuclear, which do indeed have widely noted problems - but are still far better than any coal-tar sand-heavy crude-oil shale based strategy - and, as people like T. Boone Pickens are starting to realize, solar and wind have huge profit potential and little risk of liability (unlike coal - wait till the first few global warming damage class-action lawsuits get launched). Nuclear also has a very high liability issue.

T. Boone Pickens would rather sell you electricity than wind turbines - because you only get to sell a solar panel or a wind turbine to a customer once, while you can sell electricity from now till forever - but that's business for you, and a lot of people don't want to have to maintain their own energy system - they'd rather pay someone else to do it, and they don't really care who - as long as the supply is steady and the rates are reasonable. If Pickens makes a lot of money with wind, good for him.

Clean coal, sorry to say, is a complete myth. See the discussion thread at http://www.realclimate.org/index.php/archives/2008/03/air-capture/ for reasons why (see my comment#135).

Carbon capture and sequestration will take most of the power that a coal fired power plant generates - and will also cost billions. Face it: the age of coal is almost over, and the smart money will get out now and into renewables while the getting is good.

Cyril R.

Could wind replace coal? Sure, because wind + CAES is cost-effective. Dispatchable electricity is worth a lot to utilities, and they're not afraid to pay a hefty premium for it - more than enough to pay for the CAES system.

Things will get even better with the development of no-fuel CAES.


I wouldn't expect 60% to 70% capacity factor, but it looks like Texas panhandle wind farms can get 35% to 44% capacity factor, according to slide 39 of

Cyril R.

Capacity factor is misleading. The correlation with the load is a better measurement. Wind scores pretty lousy. Although using several or many independent sites can improve the aggregate correlation with the load, this is not by itself a full solution as the transmission costs would be prohibitive. With wind, we'll still need storage. Which is OK, as you can see in the link above, the extra revenue earned by dispatchability is higher than the extra costs imposed by the CAES system.


All this is really interesting, but unless you include storage for all of those gigawatts, you don't have a pot to contribute yellow liquid to. Interestingly, if you have storage, the numbers get REALLY good for wind.

Benjamin Cole

Some people say energy independence is a myth.
I think it is quite doable. Wind farms, geothermal, nukes, solar. Shell sats they can pump shale oil at $30 a barrel.
PHEVs. Some biofuels, from seond-generation plants.
Put it all together, and you get cleaner air, lower CO2 emissions, and $100 billion a year pumped into our economy and not that of Oil Thug States.
We just spent $1 trillion in Iraq, and our military says there is no light at the end of the tunnel. Surely, we can afford energy independence.
This huge wind farm is a step in the right direction,


Some perspective on the corporate response to the climate-change demon:

The most recent annual report from Duke Energy, the big North Carolina electric utility, opens with this statement:

“We are the third largest emitter of CO2 in the United States, emitting more than 100 million tons last year.”

An extraordinary admission, yes? Give them some credit for that mea culpa.

Next, they describe their plan for changing their current emission profile.

“We are assessing what it would take to cut our CO2 emissions in half by 2030 and the implications of such an effort”.

So, they have presented a kind of fuzzy target. 22 years from now, they would like to be emitting “only” 50 million tons of CO2 per year. Progress? Sure. The end of the climate change issue? Uh, no.

If you are interested in knowing how they plan to reach their new emission targets, get a copy of the 2007 Summary Annual Report. In it, you will discover that coal and natural gas will continue to play a major part in the Duke plan.


“Pickens certainly thinks big, and somebody has to, as the U.S. government is doing little to resolve our compounding needs for new power sources.”

Jim I love you and your web log but I disagree that the US Government should be responsible for our power. Unless by this comment you mean they should open vast amounts of “government locked” resources such as off shore drilling, reduce overly complex regulations, lower extreme taxing of the industry, etc. etc. etc. We could all enjoy low cost and plentiful energy in an environmentally sound way if government had less of a role. Government is the problem not the solution.

Your advice as to what other companies “like Glitner and Chevron” should do is off base. Let the market place and free enterprise make the appropriate moves for their individual industries. The best help we can do is to impress our government leaders to back off on regulations and taxes to businesses we need. We should do all that’s possible to reduce the government burdens if they are to succeed.

Respectfully, JohnBo

Bob Wallace

Cyril -

Thanks for the CAES study link. Very informative.

I suspect one should remember that it was written for a specific part of the country where (apparently) there are more opportunities to store air than to store water.

Given an area with ample water and varied elevations this part of the study might be more important...

"PHES has higher round trip efficiency and is truly a storage system as it does not require external inputs to recapture the electricity. PHES also has a lower operating cost due to the natural gas input required for CAES."

I've got another question....

We've had wind farms operating around the continent for several years, as well at least one solar thermal plant in operation. And I assume some experimental PV sites must be strung around here and there.

I assume that these sites have been collecting 'minute by minute' data on energy input (wind strength, etc.).

When do we see the big unifying study that tells us how much backup generation or storage we would need if we tied a large enough geographical area together?

Cyril R.

I suspect one should remember that it was written for a specific part of the country where (apparently) there are more opportunities to store air than to store water.

Well, a majority of US geology is suitable for CAES one way or another, so it shouldn't be a huge problem. It's the pumped hydro resource that I'm worried about. Good locations are too rare to supply TWh's of electrical storage. There is also the NIMBY issue, a large pumped hydro system takes up a large area. CAES is mostly underground. Underground pumped hydro could also have a lot of potential.

PHES also has a lower operating cost due to the natural gas input required for CAES

That's why the adiabatic system is very promising. As you can see in the link, their adiabatic system has about 75% round trip efficiency, which is similar to pumped hydro, which is typically 75-85%. The newer pumped hydro systems are more efficient so they'll be at the higher end of the range. Still, 75% is good enough for bulk energy storage.

When do we see the big unifying study that tells us how much backup generation or storage we would need if we tied a large enough geographical area together?

That would be very useful. A lot of work though!


Has anyone considered using existing infrastructure powered with alternative fuels? Biofuels Power Corporation is powering an enitre town (Oakridge, TX) with turbines and diesels. Both are connected into the TX grid. They are using an ultra low grade alternative fuel that they happen to very tight lipped about. No ugly wind farms to build. We're considering working with them to build the exact operation at another location. If anyone knows of another operation generating power this way I would appreciate any info. avaialble.

Kit P

I must have been the only one to look at Clee's link. Slide 5 shows that the tiny greed sliver for wind capacity is growing slower than peak demand. Since most of the wind turbine erected in the US are in Texas, this means we do not have worry about storing energy from wind until pigs learn to fly.

I purpose that we discuss the potential to reduce dependence of foreign oil by training pigs to fly us to work. This air pollution a whole new meaning.

Bob Wallace

Many of us, I'm sure, would love to see biofuels as a viable energy source, but where do we get the land and water to grow that much organic matter?

Algae grown in salt or brackish water might be a source, but that technology seems to have significant problems yet to be solved.

There's a project starting up in Labrador that is combining wind and hydrogen storage for windless times.

Hydrogen storage might be a technology for future use if they can bring the cost down. It's good to see someone giving it a real world trial.

Wind/hydrogen can be a usable combo for isolated communities which otherwise rely on diesel for electricity generation.

Bob Wallace

"When do we see the big unifying study that tells us how much backup generation or storage we would need if we tied a large enough geographical area together?

That would be very useful. A lot of work though! "

Is it? Given that the data should already be digitized and the model (I suspect) wouldn't be hard to construct.

On a simplified level one could make some simple assumptions for the study, such as existing California wind farms would be connected to the same grid as some solar thermal (with storage) and PV.

If all we had to work with, what is the longest period during which we would have no usable power? (Sun goes down, wind stops, and we exceed the storage limits of thermal solar.)

Then one could add in tidal and wave sources. We must have good data for wave and we do have excellent data for tidal.

Playing with the mix in order to minimize storage/fossil fuel backup could be very useful for future planning I would think.

Tom G.

Are we proposing here to really try and teach pigs how to fly or are we just being a little sarcastic?

In either case you know that pigs are quite intelligent and they could probably be taught to fly given enough time, money and genetic engineering. Flying after all is quite easy to learn but in my humble opinion the difficult part would be to teaching them how to communicating with the control tower in controlled air space. So let's take on the bigger challenge first of teaching pigs how to talk.

To that end, I volunteer to try and find a government grant for teaching pigs how to talk. Of course I will report the results of my search results here first.

Cyril R.

If the choice is between:

1. 'ugly wind farms'
2. starving the poor and/or destroying ecosystems/soils at large
3. wishful thinking (algae)

then I am inclined to take # 1.

Cyril R.

On a simplified level one could make some simple assumptions for the study, such as existing California wind farms would be connected to the same grid as some solar thermal (with storage) and PV.

Such assumptions could be workable. Thermal storage tends to be cheap, so an oversized thermal storage system for a solar thermal plant could host other technologies without storage.

I'm thinking more about economics - what's the most cost-effective mix? The problem with that is that there's so many assumptions that have to be made to get any results that the results are unlikely to be valid in reality. Costs can change relatively quickly in many areas, and unforeseen developments in technology could change the gridmix as well. Let the market take care of this part. With a little help from e.g. carbon pricing of course. And IMHO a small feed-in tariff for alternative energy. It has to be guaranteed for at least a decade. Even worse than intermittent energy is intermittent policy and financial incentives.

Bob Wallace

I don't get the 'host other technologies' part. Are you suggesting using cheap (off-peak) electricity to heat the storage medium?


I think the market will sort out the 'what we need to build' issue. Look at the CAES paper you linked. In their model they are discussing the best time of day to sell their stored power to the grid.

Nano Solar has stated that they can produce thin film at $0.30 per watt. (I'm assuming that's material and labor costs per watt and don't include capital costs recovery.)

If that's the case then it seems likely that when the sun is out, thin film solar will be the least expensive. Thermal solar may well all go to storage until the sun starts to set as peak hours extend into the late afternoon/evening.

Anyway, seems like there ought to be enough available data to start the modeling process. (I'm betting that it's already happening, just not being made public....)


A study was done for Japan several years ago on how Japan could be powered using local renewable energy (no imports), including biomass, wind, solar, geothermal, hydro, storage, and reductions from increased efficiency. By balancing the different sources to match the load curve, and using hydro and geothermal to deal with short term fluctuations, they ended up needing surprisingly little storage.

Kit P

“they ended up needing surprisingly little storage.”

Clee, the link you provided is a complete work of fiction. You can make any assumptions you want to in a study to get what ever answer makes you feel good.

If you responsible for keeping children warm in the winter time this study is fiction. If you want to ignore fossil for transportation and generation in a study, I will suggest that you get paid to write studies and not find solutions.

I will repeat again for the learning impaired. Except for biomass and hydroelectric, renewable energy 'other' is an insignificant source of electricity and becoming more insignificant every year. Demand is growing faster than renewable energy.

There is a fundamental reason for this. Renewable energy 'other' is a very impractical to make electricity. You can worry about storage of renewable energy 'other' when pigs fly.

You might ask biomass and hydroelectric form of renewable energy are practical. The energy source for both can be stored to produce electricity when people need it.

Bob Wallace

Picture this:

Our resident pig expert receives an abrupt, but not fatal blow to the head. Not enough to be even life threatening, but enough to cause an "attitude reset".

He starts thinking like an engineer. An engineer with a problem to solve.

Here's his problem:

How to get us from a 20th Century system to one appropriate for the 21st Century.

His "Can't Do That" center would be disabled by the blow and he would start assembling known solutions into a vision of the future.

Wonder what sort of blend of energy sources he might suggest given his expertise?

Might he suggest that we maximize (soon to be inexpensive) solar for the early peak hours, solar thermal storage for later peak, blend in wind, wave, tidal, and geothermal, for around the clock availability?

Add in some compressed air, pumped hydro and battery storage? Even allocate a storage role for the plug in cars that we're likely to be driving in the near future?

Reserve biomass and free fall hydro for those times when wind and sun will fail us?

Suggest reworking our existing coal and gas as "deep backup", thus giving us a reliable grid while minimizing both CO2 emission and fuel expenditures?

(Would it be too much to imagine the blow could make him aware that there is very significant distaste for nuclear among the general public, rational or not?)

Ah, fantasy!

But, as long as we're visiting the land of golden sunsets and meadows of flowers, what if that blow also caused him to start acting like someone with whom one would enjoy sitting down and sharing a cup of coffee and conversation?

Ah, the power of imagination....


An interesting challenge, Bob. Kit P said in
"I am an engineer. Tell me your problem and I will provide a list of ways of solving that problem."

How would an engineer solve the problem of energy independence for Japan?
Comparing proven reserves to consumption, Japan has 11 days worth of oil, 6 months of natural gas, 2 years of coal. As far as I can tell, Japan has no uranium reserves.

Japan says they can extract uranium from seawater, but that hasn't gone into commercial production. According to
"The technology to extract uranium from sea water has only been demonstrated at the laboratory scale... but scaling up laboratory-level production to thousands of tonnes is unproven and may encounter unforeseen difficulties.

Japanese production of uranium is as MIA as PHEVs, so you can't depend on that.
Japan is considered to be energy-poor in conventional fuels, which is exactly why the EnergyRichJapan people chose it. But Japan does have sunshine, wind, trees, rivers, and being on the Pacific Ring of Fire, it has geothermal. How can Japan fill its energy requirement without importing fuel?


There it is. http://www.world-nuclear.org/info/inf79.html
"Japan has no indigenous uranium. Its 2007 requirements of 8872 tU

Cyril R.

I don't get the 'host other technologies' part. Are you suggesting using cheap (off-peak) electricity to heat the storage medium?

Simple. During times of extra wind power, the solar thermal turbine can be throttled down and the array's energy will be completely transferred to the thermal storage, to be used at a time of lower wind resource. This requires an oversized thermal storage resevoir, but that is relatively inexpensive.

So it's about storing energy from the grid system perspective, not directly from one power source. Should also work for PV in addition to wind.

Cyril R.

Regarding Japan, there is interesting work going to develop cost-effective sea water uranium mining. Passive (natural convection) heavy metal extraction. If it works, it could be great for Japan.

Cyril R.

Oh, Clee mentioned that already... yes, upscaling was my concern as well.

The Japanese are still trying breeders, but so far it's been an expensive and impractical venture.

Kit P

“How would an engineer solve the problem of energy independence for Japan?”

Bob and Clee confuse stupidity with imagination and creativity. We need both innovation and reason. Of course I think we should maximize solar and wind, but logic tells us we do not need to solve the problem of storage for wind and solar until there is excess to store. The first step in solving a problem, is to ask if it is a problem. There is no problem to solve yet. Debating how you would solve it is a waste of time and therefore stupid.

So using a logical process, is 'energy independence for Japan' and problem? No, not for me. As an American I want to sell coal and nuclear fuel assemblies to Japan. In turn they will use the energy to forge new reactor vessels at Japan Steel Works. We will then use the latest innovative Japanese construction experience to build that power plants whose design was a joint effort of American and Japanese engineers.

Bob wrote, “(Would it be too much to imagine the blow could make him aware that there is very significant distaste for nuclear among the general public, rational or not?)”

I suppose Bob had a theory that if you tell a lie often enough and induce brain damage, I will believe him. I have attended public hearings for the two closest new nuke plants. There appeared to be general favorable support. One woman who did not live in the coal community was very concerned about spent fuel rods 'laying around' and killing people. I was holding in my hand literature that that was available before the meeting started. A man and woman wearing hard hats were standing next to a very robust dry storage cask. The NRC was very tactful and neutral. They stated what regulations must be followed.

For all of you who want to put their imagination to work, go back to college and learn the tools. Some of the tools are location specific. The links that Clee provided enough info to evaluate Japan. However, countries without large coal and uranium reserves choose nukes and reprocessing because it is easy to store reserves. Next they must compete with a energy hungry world for tankers of LNG, oil, and coal. It has been a scary few months for China, Japan, and South Africa.

We can ignore the problems in the US of the 70' and the issues in California in 2000/2001. How that saying go? When you are up to your ass in alligators, you tend to forget your goal was to drain the swamp. So why do some people worry about AGW and think PV is any kind of solution?

Bob Wallace

"During times of extra wind power, the solar thermal turbine can be throttled down...."

OK, got that. I thought you might be suggesting thermal storage from wind, which wouldn't seem to be an efficient system.

Rather than "hosting" we might want to talk about timing the release of power to the grid for when it's most needed. That's something that thermal solar can do to a certain extent, unlike wind, wave, etc.

(Wonder how much the "16 hour storage" limit can be extended?)

As all these systems are going to come on line piecemeal it really seems like the market will create a good mix.

Interesting, innovative times ahead.

Cyril R.

Storing wind through thermal storage, well that requires a couple of breakthroughs in thermal conversion efficiencies, which I wouldn't count on, but it's possible.

(Wonder how much the "16 hour storage" limit can be extended?)

The only real limit is cost. Just add more tanks or thermal storage solids, or caverns if surface space or aboveground costs are too high.

Although, storing thermal energy seasonally would, besides being costly, also be impractical due to very high thermal losses which also costs a lot. Space age insulation could solve it, but that's not cheap either.

A bit of natural gas or biogas backup makes more sense. The Nevada Solar One trough plant uses some thermal storage but still has a NG backup for an emergency. It says 98% solar fraction so that's just 2% NG, no worries.

CAES could work for weeks of storage; resevoir specific costs are relatively low so getting a high turnover is not that important for good ROI. With AACAES there would be the long term thermal storage issue.

These issues will become more important, and will no doubt receive more attention, when the percentage of wind and solar on the grid increases. Interesting times indeed.

Cyril R.

I'm actually not sure about that 16 hour figure. Sounds rather mandatory; why not 15.8 or 16.3 or something like that? Maybe they rounded it down for the readers' convenience, because I can't imagine the actual figure is exactly 16.

Roger Brown
Well, a majority of US geology is suitable for CAES one way or another, so it shouldn't be a huge problem.

Do you have a reference for the above statement? I have seen this claim made a number of times on the web but have never found a detailed reference. In the following PDF discussing CAES technology (http://www.espcinc.com/ViennaCAESGT2004rev3-54278.pdf) I find this statement:

Also, EPRI (Electric Power Research Institute) conducted very extensive geological studies to identify locations in the U.S. with geological characteristics acceptable for development of underground storage facilities for the CAES power plants and produced a data base of construction and operating costs. The published report and produced maps confirm that more than 80% of the U.S. territory has salt, hard rock and aquifer formations acceptable for creation of underground storage facilities in a cost-effective manner.

No reference to a specific report is given. I have searched the EPRI website (http://my.epri.com/portal/server.pt?), but I was unable to find a detailed study on CAES geology. I am distrustful of “well know facts” which have no supporting data. If the hard rock formations referred to above constitute the majority of CAES potential then the capital cost of creating underground storage may be quite high.

Cyril R.

Yes, I've seen the 80% claim a couple of times as well. Doing a quick search, this PDF came up.

Notice Figure B1: Regions of the United States with Potentially Suitable Sites
for Compressed Air Energy Storage.

It appears that a large part of the US has aquifers/salt formations. Hard rock only is a minority area, and there are some areas, such as Nevada and Florida which don't have much suitable geology at all.

I've also looked at the reference that was quoted under the map, Cohn and Louks (1991), but it was no longer available. In another study (subscription required), they note some caveats:

Low-cost geologic reservoirs for CAES may not be available in all areas. While it is estimated that some form of suitable geologic storage is present in 75–80% of the US land area (EPRI-DOE, 2003 EPRI-DOE, 2003. EPRI-DOE handbook of energy storage for transmission and distribution applications. Report Number 1001834, EPRI, Palo Alto, CA and the US Department of Energy, Washington, DC.EPRI-DOE, 2003), the type of geology varies: salt domes are prevalent in the Great Plains, Rocky Mountain and Gulf States regions; saline aquifers are ubiquitous in the Great Plains, Midwest and Appalachian regions; some regions contain only expensive hard rock; a few regions (the Southeast, much of California, and Nevada) contain no suitable geologic formations (Cohn et al., 1991). However, for the most part, the areas of potentially favorably geology overlap substantially with regions of high-quality wind resources. It remains to be determined from high-resolution geologic surveys just how prevalent this overlap is, though such surveys have not been completed for the US or any other region. Also, experience with the use of aquifers for CAES is limited.

Basically, they're still working on the details.

Roger Brown


Thanks for the links. The infomation is still pretty sketchy, but it's more than I have found previously.

Cyril R.

Hard rock and buried pipes would be more expensive, but then again if you look at the costs, it's still much cheaper than flow batteries, sodium sulphur batteries, which have similar efficiencies. And hydrogen is even more easy competition.

Of course, the CAES doesn't have to be near the wind site. It can make better use of transmission economics if placed in more centralized locations.

Alternatively, the CAES systems could be near demand centers. Perhaps combined heat and power could be an option then, especially for medium- and small-scale systems.

Cyril R.

If the CAES is placed near the wind site (ie if it has suitable geology) then there is another promising idea. There was a post on this blog about it, General Compression just skips the electrical turbine altogether, integrating the compressor with the windmill itself. If the aquifer or salt dome is directly under the windfarm then this could definately be viable.

Bob Wallace

I notice by your posted info that California seems to lack good CAES sites.

But California does have a bit of existing hydro and the reservoirs with which I'm familiar seem to be forced to reduce output in the late summer/fall. Our streams are very seasonable.

Here on the North Coast the proposed wind farm has been downsized as our grid connection to the outside world is too small to ship out the power that could have been generated with the larger farm running full blast.

It wouldn't take much to install a secondary basin below the dam of our local hydro source. And I don't image any NIMBY resistance as this land is already set aside 'in the event the dam should burst'.

(Same situation over east of the San Francisco area where I used to live. Good wind at times and several hydro systems already in place.)

Local solutions as we kill the energy problem with a thousand small cuts....

Cyril R.

Lots of potential for conventional pumped hydro no doubt, what can be done must be done.

My take on our current hydro-electric infrastructure is to convert them to micro-hydro over time, when they get too old.

Calfornia also has good solar thermal resource, so could do the power hosting idea.

Anyways, if we're going with the supergrid, then the storage location restraint may not be relevant at all.

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