For Base-Load Wind Cheaper than Fossil Fuels: CAES
As PG&E ramps up renewable power in response to the California RPS requirement that it get 33% of its electricity from renewables by 2020; it has been exploring ways to add that much renewable power to the grid while smoothing out the ups and downs of wind energy, which often peaks at night.
The utility needs a way to turn sometimes-too-much wind into anytime-always-there electricity.
The solution? Simple tech. Underground compressed air.
With compressed air energy storage; air is compressed and then pumped in natural underground reservoirs. The air is released later and converted into electricity. With enough storage, even fickle wind could actually supply base-load power.
So PG&E has applied for DOE smart grid stimulus funding under The Recovery Act; to build a compressed air energy storage project with output capacity of 300 megawatts. They are applying for $25 million.
By comparison, building a plant to burn fossil fuels would cost around $850 million for the same 300 megawatts of fossil energy.
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PG&E estimates their $350 million project will take five years to design, permit and build. Wind turbines would compress the air during off-peak times and then draw from the reservoir during peak times. Shifting the energy from off-peak to peak times, such as the middle of the day, makes it more valuable as utilities pay far more for peak energy.
If granted, the utility would use the smart-grid stimulus funds available in The Recovery Act in order to build enough storage to hold and release as much electricity as a medium sized base-load power plant for about 10 hours each time.
PG&E would pump compressed air into an underground reservoir, using mostly wind energy to power the generators, and some natural gas - about a third as much as a gas-fired plant of that capacity.
Another proposal for reheating the air withdrawn from storage, is to use biomass-derived fuels produced locally from energy crops in remote, wind-rich areas.
Compressed air energy storage or CAES has orders of magnitude more capacity than typical utility batteries and appears to be the most cost-effective form of energy storage according to technical experts at the Electric Power Research Institute and a massive study of CAES at Princeton University which concluded:
“CAES appears to have many of the characteristics necessary to transform wind into a mainstay of global electricity generation. The storage of energy through air compression may enable wind to meet a large fraction of the world’s electricity needs competitively in a carbon constrained world.”
The concept has been proven. The Alabama Electric Cooperative in Alabama now has 20 years of experience with a 100 megawatt CAES system. A major new project is being backed by the DOE in Iowa, which gets 15% of its electricity from wind.
So just through time-shifting energy delivery; storage can make it possible for wind to essentially supply base-load power for far less money than building more fossil fueled power stations. What this amounts to is adding 300 megawatts of new power to the grid.
Hmm… $25 million for 300 megawatts of carbon-free future-friendly time-shifted wind power or $850 million for 300 dirty megawatts of a dwindling resource?
I’m betting that that very smart Steven Chu of the DOE is going to grant this $25 million to PG&E…
Via GreenTech and PG&E
Image from PG&E and Flikr user The Eleven
Great article! Also there isn’t that much loss (around 15%) to compress the air then bring it back.
One question, how many underground cavern sites are there around the USA? Do you have a map of these sites you can share?
I don’t understand why they need a grant if this is so cheap. What are they waiting for?
I also question the cost of building a thermal power plant which is usually around $1 per watt or $300 Million for 300 Megawatts or about 1/3 the cost displayed in this article.
I believe these companies plans are more about subsidies than renewable energy. First they want us to believe that renewable energy costs more so that they can request subsidies. Then they want us to believe that they can store energy for a lot cheaper than they made us believe in the fist place.
Remember that energy storage is the most crucial and costly component of most renewable energy solutions and suddenly this cost would become marginal (3% the cost of a thermal power plant).
There is a discrepancy here that needs to be explained.
According to the study from Princeton University, pg 11, the capital cost for a CAES is $580 per KW () or $174 Million. That’s a lot more (x7) than $25 Million.
CAES can also improve the efficiency of gas turbines by reducing compressor loads. It’s a perfect match for thousands of declining gas fields where exhausted gas pockets can accommodate CAES and augment onsite peak power production. These fields are already drilled for air injection and often have onsite power turbines, just add compressors and wind power.
$850 million is a generously low estimate - per that link = that coal plant has now gone over a $1 billion!
One thing: Right now only diabatic CAES systems exist, AFAIK one in the US and one in Germany. In a diabatic system, the heat resulting from compressing air is lost and later replaced by burning natural gas. Neither as efficient as it could be nor renewable. Only an adiabatic CAES (i.e. one that stores the heat as well) can truly operate without fossil fuels.
Lots of work to be done still.
Thanks for linking my “massive report”! More on my blog for those interested http://switchboard.nrdc.org/blogs/ssuccar/ -Samir
why not to invest massively in such cheap technologies
You’re welcome, Samir, one thing I am unclear about from the rather generic announcement from PG&E:
Does CAES require the use of some natural gas to run the generator? Can this all be done using wind power electricity? Your long pdf raised the question but didn’t clarify it for me.
What sandra said