Texas Wind Still More Expensive with CAES than Nuclear

When I presented my cost study of "reliable Texas wind using batteries, several of my critics complained that alternative energy storage systems, for example pump storage or Compressed Air Energy Storage (CAES) . My analysis of the cost of Pumped Storage indicates that the capitol costs were comprable to those of batteries once uncertainties were taken into account.

However, CAES does appear to lower the cost of energy storage, but at the cost of a considerable inefficiency in the use of wind generated electricity, CO2 emissions, and a surprising environmental issue. CAES increases the reliablity of wind generated electricity, but may not greatly increase the value of off peak hours generated electricity to the producer, despite the delivery of more hours of electricity during day time and peak demand hours. Even with its ability to deliver electricity at times when utilities pay for it at optimal rates, CAES systems appear to only bring a modest return to their owners. I will presently argue that CAES could be more profitable without its coupling with wind using an alternative post-carbon energy stratigy.

This assessment is based on "The Economic Impact of CAES on Wind in TX, OK, and NM," by Ridge Energy Storage & Grid Services L.P, for the Texas State Energy Conservation Office. in 2005 .

The Ridge Energy study focused on atwo alternative hypothertical projects invloving the use of CAES thenology coupled to several wind generating facilities in West Texas, Western oklahoma, and New Mexico. These facilities have some of the most reliable wind in the United states, with average capacitiy factors of around .40. In addition, wind generation does not take place symultaniously at all of these facilities, thus coupled together they produce electricity with greater reliability than their average capacity factor might suggest. The use of CAES would enable the ability to guarantee the dispatch of both base electricity, and 16 hour a day week day electricity. The use of CAES would enable wind producers to sell electricity produced at night at day time prices, but with some fairly significant inefficiencies.

A significan amount of heat energy is lost during the air storage of the operation that aas the air decompresses, it comes out of the ground at below 0 C (32 F). Moisture in the decompressed air condensed and freezes. The resulting ice would damage generation turbines, necissitating the heating of the ait by burning natural gas to melt the ice. 40% of the energy converted into electricity in conventional CAES systems comes from burning natural gas. Energy output of CAES systems is .80 of energy inputs. This suggests that there are considerable in efficiencies in the use of wind generated electricity by the wind CAES system, and that 30% of the electrical input is lost to system inefficiencies.

Ridge energy stimatrd that the capital cost of a CAES system would run @$765 per KW, an exceedingly modest sum, but one which should be examined. The capital cost for electricity produced by the Wind cAES system is in fact much higher. Last week I discussed recent wind costs as reported by Bryan Layland, a electrical systems engineer from New Zeeland. Some commenters rejected Leylands cost figures on the wholely irrational grounds that he was a global warming skeptic. Looked for cost figures for North American Wind projects, in order to evaluare Leyland's numbers, and found 4four projects costing between $2200 and $3200 per name plate wind KW. For the sake of simplifying the argument I will stipulate a cost for new West Texas wind of $2250 per name plate KW in 2009. Since the capacity factor of West Texas runs around .40, the adverage output West Texas wind producer can expect to pay $5625 produce KWs of electricity his windmill will average producing. Since only 70% of the electricity entering the CAES facility reaches the consumer, the wind producer must add 30% more capacity to compensate for the energy loss. Thus the price of the wind generated electry entering the CAES facility must compensate the wind producer for something like a $8000 capitol investment for every average KW sold to the CAES facility. When added to the $765 per KW Capital investment in the CAES facility, we get a very ugly picture, of the cost of wind generated electrity. but one which is still less than our battery based system, about which I made some slightly different stipulations, Since the 2008 cost oh nuclear power is somewher between $4000 and $5000 per KW (as opposed to an estimated $8000 to 12,000 figure during the middle of the next decade).

I would next like to turn to what might be considered a suprising consequence of the use of CAES technology, that is a radiation problem. The same problem also exists, largely unrecognized with all gas fired electrical generating systems. The origin of the problem comes from the more or less uniform pressence of U238 and Th-232 isotopes in more or less uniform amoumnts in crustal rocks. Both isotopes are slighltly radioactive, and as they breakdown through alpha partical radiation, they under go nuclear mutations that eventually leads to the production of radsio-active radon gas. Radon present in rocks is known to escape with natural gas, and wiyh other gases, trapped underground, Salt is known to be relatively impermniable to the transportation of radioisotopes. And there is no uranium or thorium in salt domes. Thus air drawn from sali caverns should not posae radiation danger, as long as the salt has not been evaculated to the rock walls of the cavern. However there would be some question of radon pollutionof stored air in natural caverns, or in mines. There is an even more significant radon danger in deep underground aquifers, which have also been proposed for CAES. Greens, of course, will not see the sligest danger from radon escaping through the operation of CASES fascilities even though they would see far less radon escaping from reactors as an extreme and very dangerous environmental hazard. Radiation is not radiation if it comes from "natural" sources in the Green propoganda. Of course green advocates of CAES technology, all of whom are total hypocrites on radiation issues, have totally ignored the radon problem with natural gas and with many proposed CAES systems.

It is possible to recover at least some of the waste hear usually lost to cavern walls in CAES storage. Compressed air can be run through heast exchanges, just like air from super chargers is sometimes run through intercoolers to cool it before it enters an engine. Heat storage systems using rocks, mineral oil, or molten salt would have to be fairly masive, and would add complexity to the CAES system. While they might lesson the amount of heat lost to cavern walls, heat storage systems do not repeal the second law of thermodynamics, and at least 25% of the energy used to compress the air, is still lost in the process. It is not at all clear that the added capital expense of heat capture and release systems would cost less than the cost of the added wind capacity necessitated by CAES inefficiency.

Finally, it ought to be noted that a potential day carbon free power system for producing day time power with CAES without windmills is possible. It seems to have escaped the notice of most CASE advocates that CAES casn be teamed with nuclear power plants in innovative ways. Since it is more economical to keep reactors running at full power all night, suplus electricity produced at night could be used to store compressed air. During the day, compressed air can be used to expand the reactors daytime power output by as much as 40%. The air does not have to be heated with natural gas. Indeed the compressed air can be heated from the reactors waste heat, killing two birds with one stone, and conserving the water used for daytime reactor cooling, and the use of compressed air in cooling the reactor, would creat significant water use savings, allowing reactors to run even during drought conditions.