Editing Compressed-air energy storage (section)

=== Adiabatic ===
Adiabatic storage continues to store the energy produced by compression and returns it to the air as it is expanded to generate power. This is a subject of an ongoing study, with no utility-scale plants as of 2015. The theoretical [[Energy conversion efficiency|efficiency]] of adiabatic storage approaches 100% with perfect insulation, but in practice, round trip efficiency is expected to be 70%.<ref name="BINE1">{{cite web| title = German AACAES project information| url = http://www.bine.info/fileadmin/content/Publikationen/Englische_Infos/projekt_0507_engl_internetx.pdf| access-date = February 22, 2008| archive-date = August 26, 2018| archive-url = https://web.archive.org/web/20180826211224/http://www.bine.info/fileadmin/content/Publikationen/Englische_Infos/projekt_0507_engl_internetx.pdf| url-status = dead}}</ref> Heat can be stored in a solid such as concrete or stone, or in a fluid such as hot oil (up to 300&nbsp;°C) or molten salt solutions (600&nbsp;°C). Storing the heat in hot water<!-- 100&nbsp;°C ? --> may yield an efficiency around 65%.<ref name="es2022jan20">{{cite web |last1=Colthorpe |first1=Andy |title=Why Goldman Sachs thinks advanced compressed air is worthy of US$250m investment |url=https://www.energy-storage.news/why-goldman-sachs-thinks-advanced-compressed-air-is-worthy-of-us250m-investment/ |website=Energy Storage News |archive-url= https://web.archive.org/web/20220403123901/https://www.energy-storage.news/why-goldman-sachs-thinks-advanced-compressed-air-is-worthy-of-us250m-investment/ |archive-date=3 April 2022 |date=20 January 2022 |url-status=live}}</ref>

[[Packed bed]]s have been proposed as thermal storage units for adiabatic systems. A study <ref>{{cite journal | last1=Barbour | first1=Edward | last2=Mignard | first2=Dimitri | last3=Ding | first3=Yulong | last4=Li | first4=Yongliang | title=Adiabatic Compressed Air Energy Storage with packed bed thermal energy storage | journal=Applied Energy | publisher=Elsevier BV | volume=155 | year=2015 | issn=0306-2619 | doi=10.1016/j.apenergy.2015.06.019 | pages=804–815| s2cid=28493150 | doi-access=free | bibcode=2015ApEn..155..804B | hdl=20.500.11820/31a2a7f9-5fc6-4452-8bd8-b08614bebae2 | hdl-access=free }}</ref> numerically simulated an adiabatic compressed air energy storage system using packed bed thermal energy storage. The efficiency of the simulated system under continuous operation was calculated to be between 70.5% and 71%.

Advancements in adiabatic CAES involve the development of high-efficiency thermal energy storage systems that capture and reuse the heat generated during compression. This innovation has led to system efficiencies exceeding 70%, significantly higher than traditional Diabatic systems.