: Since I don't recall the numbers from the article and they're probably different now (because of advances in technology and experience) anyway, how well does compressed air compare to water pumps as a means of energy storage?
Pretty favorably, they're both ~80% efficient, CAES construction is ~$500/kWe versus hydro's ~$1000/kWe, and storage is $1-2/kWhe to hydro's $10-80/kWhe (6.7MB PDF)
. Efficiency should come up quite a bit once they integrate thermal storage so they don't have to waste energy heating it back up during decompression. As the PDF notes, suitable locations cover 80% of the continental USA (aside: It also notes combined wind/CAES construction at $1250/kw, in 2005
: "A storage time measured in minutes"? That's pretty useful to lighten up your country for the whole night... (Sarcasm Mode
Aside from my disbelief at the idea of a lead acid battery blowing most or all of its charge in a matter of hours, I'm sure you know perfectly well that instantaneous storage and longer-term storage are different markets with different technical implementations. Fast high-efficiency systems (like ultracapacitors, nearly 100% efficient with huge wattage, but insanely expensive both in terms of throughput and storage volume) and slow moderate-efficiency systems (like fuel cells, which are already ~60% efficient round-trip (≥90% combined-cycle,) ~$3000/kWe (already well under $1k/kWe for automotive systems,) and almost nothing per kWhe since it can be compressed or liquefied in any suitable container just like other gasses) appeal to completely different applications.
Also, while I still insist batteries are not suitable for long-term grid storage, the very paragraph you pointed to describes lithium-ion as only slightly more expensive per watt, and the link directly above that paragraph notes that commercial NaS installations are already ~$400/kWe, ~$400/kWhe, and ~90% efficient.
edited 1st Jun '11 11:50:20 AM by EricDVH