An Energy Solution in the (Compressed) Air?

[jpak]

http://greeninc.blogs.nytimes.com/2008/12/23/an-energy-solution-in-the-compressed-air/

The wind doesn’t blow all the time, so the electricity it produces is also intermittent. A solution to this problem could be pulled from the air, literally, using a technology known as “compressed air energy storage,” or C.A.E.S.

Compressed air storage essentially involves using electricity to compact air and force it underground. Then, when the air is released and burned with natural gas, it expands, driving turbines and creating electricity.

The compressing is done when there is an excess of cheap electricity — at night, for example, when the wind is blowing but nobody has their lights on. Then it can be released when there is strong demand for electricity — in the middle of day, for example, when air conditioners are humming.
Compressed air is one of several innovative storage technologies — including ice — that my colleague Matthew Wald wrote about last year.

Several states are exploring it, including Iowa, Texas, Ohio and, as my colleague Ken Belson recently reported, New Jersey. The technology is already used at a power plant in Alabama, where compressed air is stored in a salt dome. Germany also has a compressed-air plant. Xcel Energy, a Western utility that uses substantial amounts of wind power, is also studying compressed-air storage in conjunction with the Electric Power Research Institute, according to Steve Roalstad, Xcel’s media-relations director.

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[Tesha]

1. This is a pretty reasonable approach for large-scale stationary storage.

IIRC, Con Edison in New York was investigating this for a while, but I
never heard the results.

On the other hand, in a few moments, the compressed-air car people
will probably arrive and *THAT*, for blatant thermodynamic reasons,
is a pretty poor energy storage means.

Tesha

[kristopher]

2. CAES is set to be one of the principle ways

CAES is set to be one of the principle ways of generating dispatchable power for a renewable grid. You can expect to see a lot of them.

Google:

Using gas turbines to enhance the value of wind power
By Jeffery B Greenblatt, Princeton University

Or for more detail and academic rigor:
Baseload wind energy: modeling the competition between gas turbines and compressed air energy storage for supplemental generation
Jeffery B. Greenblatt,

[TheWraith]

3. Only if you have a massive oversurplus of power in the first place.

Otherwise you're wasting a huge amount of power in efficiency loss converting to work and then back again.

[kristopher]

4. Any way you slice it we are going to need storage.

That incurs a price.

If we are interested in a renewable economy, CAES with natural gas is one step in the process. As renewable infrastructure develops, CAES offers the opportunity to initially reduce GHG emission substantially, and the potential of eventually moving from natural gas to methane produced from wastes.
With fluctuating demand it is inevitable that a nation's generating infrastructure will configure itself to meet peak demand. This means that all systems are inevitably going to have wasted capacity that is producing in excess of demand. That is true whether the energy source is coal, natural gas, nuclear, or an assortment of renewables operating on independent schedules. Although wind, sun, tides and currents operating in their own timetables instead of ours, they are reasonably-to-very predictable. Bottom line, their excess will be stored and used in conjunction with other technologies to match supply with demand.

The economic viability of producing baseload wind energy was explored using a cost-optimization model to simulate two competing systems: wind energy supplemented by simple- and combined cycle natural gas turbines (‘‘wind+gas’’), and wind energy supplemented by compressed air energy storage (‘‘wind+CAES’’). Pure combined cycle natural gas turbines (‘‘gas’’) were used as a proxy for conventional baseload generation. Long-distance electric transmission was integral to the analysis. Given the future uncertainty in both natural gas price and greenhouse gas (GHG) emissions price, we introduced an effective fuel price, pNGeff, being the sum of the real natural gas price and the GHG price. Under the assumption of pNGeff $5/GJ (lower heating value), 650 W/m^2 wind resource, 750 km transmission line, and a fixed 90% capacity factor, wind+CAES was the most expensive system at b6.0/kWh, and did not break even with the next most expensive wind+gas system until pNGeff $9.0/GJ. However, under real market conditions, the system with the least dispatch cost (short-run marginal cost) is dispatched first, attaining the highest capacity factor and diminishing the capacity factors of competitors, raising their total cost. We estimate that the wind+CAES system, with a greenhouse gas (GHG) emission rate that is one- fourth of that for natural gas combined cycle plants and about one-tenth of that for pulverized coal plants, has the lowest dispatch cost of the alternatives considered (lower even than for coal power plants) above a GHG emissions price of $35/tCequiv., with good prospects for realizing a higher capacity factor and a lower total cost of energy than all the competing technologies over a wide range of effective fuel costs. This ability to compete in economic dispatch greatly boosts the market penetration potential of wind energy and suggests a substantial growth opportunity for natural gas in providing baseload power via wind+CAES, even at high natural gas prices.

Baseload wind energy: modeling the competition between gas turbines and compressed air energy storage for supplemental generation
Jeffery B. Greenblatt etal

[TheWraith]

5. Given the absurd price of storage, I think we're better off without it, honestly.

You're talking about doubling our build-out requirements when you talk about storage like pumped hydro and CAES. It's easier and smarter to build reliable base-load generation capacity.

[kristopher]

6. No it isn't.

There have been far too many analysis that say the most cost effective, sustainable, carbon-free route to a climate solution is built around maintaining the current level of nuclear, combined with renewables, EVs w/V2G storage, CAES storage and pumped hydro.

There is nothing in nuclear technology that allows you to get away without a means of load following - which means meeting demand peaks that are substantially greater than average load. If you are going to solve the climate crisis with nuclear, that means that the excess nuclear capacity for meeting peak demand is going to sit idle the vast majority of the time. All systems require a means of load leveling. All of them. You can't criticize renewables for requiring the capacity for load following and then ignore that same requirement for a technology you've preselected without proper analysis - in this case, nuclear.

In the event you aren't familiar with what the typical demand curve looks like, here is one plotted on a Climate Progress FAQ page discussing another storage tech, plug in EVs with V2G.
http://climateprogress.org/2008/07/11/plug-in-hybrid-faq/


http://www.calcars.org/epri-driving-solution-1012885_PHEV.pdf

[Tesha]

7. Not if you want to avoid carbon emissions *AND* nuclear waste.

Aside from hydro, there really aren't any renewable technologies that
don't require either a grid cast very, very wide or localized storage.

Tesha