East Texas Getting Compressed Air Energy Storage Plant 248
First time accepted submitter transporter_ii writes "A compressed air energy storage (CAES) plant was first built in Germany in 1978, but East Texas will be the site of one of the world's first modern CAES plants. How does it work? A CAES power generation facility uses electric motor-driven compressors (generated by natural gas generators) to inject air into an underground storage cavern and later releases the compressed air to turn turbines and generate electricity back onto the grid, according to the plants owner. The location near Palestine, Texas was selected because of its large salt dome, which will be used to store the compressed air. The plant is estimated to cost $350 million-plus, and will create about 20 to 25 permanent jobs."
This cannot possibly be efficient (Score:5, Informative)
When your compress air it heats up, increasing the pressure and making it harder to compress more air.
After it's been in the ground for a while it cools back down to ambient temperatures.
Then when you're extracting it the air is expanding which makes it cool down and reduces the pressure, therefore reducing the practical energy you can get out of it.
This is basic stuff you learn in Chemistry I.
Re:Do they gain energy due to seasons? (Score:5, Informative)
Likely not...earth is not a really good conductor of heat and the air temperature in caves tends to vary only slightly over the year.
Re:20 perm jobs? (Score:4, Informative)
More importantly, I don't get why anyone would advertise that 350M is being spent to create 20 "permanent" positions. That's 17.5M per fulltime job!
Re:This cannot possibly be efficient (Score:5, Informative)
Re:Efficiency? (Score:5, Informative)
Compressed air is probably 75 percent of that.
Depends how adiabatic the whole system can be made. Needs to be terribly well insulated to store the heat of compression. Dieseling the lube oil inside the compressor pistons is probably the limiting temp on the hot end.
Water storage loss is very low, evap and leakage. Compressed air heats up and you need that heat to stay in the tank or you lose the energy.
Also your example of 85% in and 90% out seems a bit messed up since .85*.90 is about 76.5% which compares favorably to your pneumatic air storage system.
Non-adiabatic systems like pneumatic control systems used in factories etc are ridiculously inefficient. You end up with a 10 HP compressor output an effective 1/4 HP of "machine". No one is seriously suggesting non-adiabatic systems, like house or car or factory size.
Re:I wonder (Score:5, Informative)
I hope, at least, that using CAES is more efficient than just burning the natgas and twirling the turbines with that. (I doubt that but I'm no energy expert.)
It can be more efficient if wasted power generated is less, because power demand is highly variable. Burning straight up natgas may lead to waste, if not all the power generated is required. With CAES, all the output can be stored until needed, as long as there are no "leaks" in the underground cavern, and the rate of pressure loss isn't too high.
With CAES, the power generation output can possibly be more easily reduced, during off-peak hours, to match the demand, with less loss in efficiency, and without having to shutdown/fire up a certain number of natgas generators based on demand.
Re:I wonder (Score:5, Informative)
I just want to add something that might be escaping some people.
Most natural gas generators on the scale of a public utility use a turbine engine which means that it's efficiency concerning getting work from the fuel used is pretty much in a narrow spot close to peak production. If you wind it down to generate less electricity it becomes less efficient and degrades the engine components faster so it's avoided. If you keep it in it's peak range but turn the generation down, you are being almost as wasteful as if the machine was producing full bore all the time whether it was needed or not.
This is even true for traditional internal combustion engines like in your car or motorcycles where it is geared so that your cruising range is between a certain RPM in order to take advantage of it. Outside that range is a little less efficient but isn't as pronounced as it is when you are dealing with an engine producing thousands of horsepower to drive gigantic generators.
What this compressed air storage does is allow the generation to be controlled by something that can be turned up or down easily as demand increases or decreases (compresses air) and the natural gas portion of it operates in the peak efficiency range of converting fuel to useful work when it is running.
how much of this translates into savings or overall efficiency improvements is something I don't know, But it seems to be enough (on paper at least) to throw millions of dollars at.
Re:I wonder (Score:5, Informative)
The bit about natural gas in the submission is simply wrong. There happens to be a natural gas power plant somewhere nearby, but the two facilities have nothing in common. It is unlikely that the storage facility will be storing power while the natural gas power plant is providing it.
Re:I wonder (Score:5, Informative)
Oh, uninformed twats all up in this thread; surprise, surprise.... (chiefly referring to submitter and GP)
First some links (as opposed to URLs as text -- this is 2012, learn HTML or GTFO):
EPA application you didn't link. [epa.gov] A good read that should have been in TFS.
The company building it. [apexcaes.com]
The gear to be used. [dresser-rand.com]
Okay, the submitter clearly got confused, but I think differently. Possibly from this sentence of the EPA application:
A natural gas fired reciprocating engine will power an emergency electric generator rated at 740 ekW, necessary to support starting the plant when power from the grid is unavailable (“black start”).
The other possibility is because it's a natgas-fueled hybrid CAES rig, which concept is apparently very difficult for a certain class of mushbrain to grasp.
This plant uses only electricity from the grid to compress air. Could well be from natgas (which is damn cheap these days, and less CO2 than oil or coal), but if so it'll probably be a modern combined-cycle plant with high efficiency. Could also be nuclear, hydro, wind, or coal.
It DOES, however, use natgas to run -- rather than simply blowing compressed air down to atmospheric in a turbine, they use the stored compressed air in a Brayton cycle. A conventional gas turbine exhibits low load range (typically can't run less than 50% of maximum power), because the compressor is designed for specific conditions; throttle it back, and you lose efficiency rapidly, and eventually it stops working completely.. With a hybrid CAES plant, though, the gas is pre-compressed, so you just add heat (burn natgas) and expand w/ reheat. This allows scaling to very low power output. (In this particular case, the very high storage pressure (1900~2830 psi) actually means they can put another turbine before combustion, blowing the air down to around 800 psi.)
Best i can tell is that they buy electricity during non-peak, and use that to compress the air so that it can be released against to drive the turbines during peak. Almost as if they are acting as electricity speculators (buy low, sell high).
More like cross-border arbitrage than speculation IMO; even though peak and off-peak pricing aren't set simultaneously, they both usually move slowly compared to the diurnal alternation of the two. So to me, rather than considering it a single market with wild periodic swings, it's useful to treat it as 2 (or many) concurrent markets, of which you can only trade in one at any given time.
Re:I wonder (Score:4, Informative)
Not really speculators. Electric utilities have several rates it costs them for the power they generate or obtain and sell to the consumer. They are classified as base, peak, and overages of either.
They determine their base usage which can be done relatively easily and purchase or generate that much plus 10 or 15 % (I forget what the demand surplus by law was last time I checked but this is needed at all times to avoid brownouts and so on). They only purchase or produce enough energy to supply this needed amount the majority of the time. Excess energy is either sold to other utilities or not purchased. This is the cheapest rate by far because it can be purchased by long term contracts and the generation facility can be running at max performance at all times.
The next rate is the peak usages which is similar to the base but only applies during the peak times electricity will be used. It's a bit more expensive because peak times are generally within hours of each other all across the nation. This means that an electric producer somewhere has to have generating capacity on standby for these times and not in use for others. Of course if you have generating capacity and the investment needed to procure it, maintain it, and transmit it, you would do it all the time to get the benefits of economic of scale (producing 1000 units for sale with the same devices instead of 100 units). But because this is only needed for a relatively short period of time, the generation costs lost by not being needed the other times is recaptured in the increased pricing for the peak costs. This is also subject to long term planning so long term contracts can secure cheaper prices then the third type of energy, the overage type.
The overage type of energy a utility needs to purchase is all amounts of energy in excess of the base or peak estimates not covered by an existing contract and is purchased as needed when needed. This is the most expensive because someone has invested in a generation facility that doesn't make much money unless utilities plan poorly or something happens outside their control or expectations. This down time is also recaptured in the pricing. An example of when this is needed is when there is a heat wave and not only is everyone running their Air conditioners set on max, but they are turning on fans and everything else they can think of to keep cool. Perhaps a sale on plug in electric cars added to the load for a specific utility in a short period of time on top of that and everyone plugs in when they get home from their 9-5 job. Or there is a rash of burglaries and everyone is increasing their outside lighting and leaving more lights on at night in order to avoid being a victim. Whether the utility is on base or peak at the time, the amount of excess or overage capacity that needs to be available is purchased as needed and at the highest prices they have to pay for electricity to sell to their consumers.
All that is figured into your rates when you get a bill and isn't really obvious. The term overage might be the wrong term to use (I'm thinking it might be something else but am too lazy to look it up). Some utilities separate peak rates from base rates and charge more for peak to give you an option of trimming your usage during the peak. But buying on base rates and reselling on peak or even overage rates is sort of how the entire electrical utility industry operates except energy storage techniques haven't traditionally made it practical. It is the same concept except that the source fuel is separate by a conversion factor (natural gas or coal converted to electricity to be stored as compressed air to be converted back to electricity) instead of being converted to electricity only once.
This type of pricing to the utility is also something that makes the usage of solar and wind power difficult to use. Maybe if this project proves useful and profitable, alternative energy could use compressed air storage to store it's production and sell in the same ways to get around the problems of compet
Re:I wonder (Score:5, Informative)
Someone mod this up. You'd have to be retarded to use natural-gas-generated electricity to operate an electric compressed air storage plant. The submitter just made that up.
Texas has a relatively de-regulated electric grid with a lot of wind capacity. Prices fluctuate wildly. This facility will use renwable wind and solar energy to compress air at times when it is cheap. Then, at times when electricity is expensive, the air will be used to operate a natural gas turbine and generate electricity.