As we look, a little wistfully, at the latest EU grant given to Gaelectric to developed their CAES project near Larne, it's a timely reminder in amongst the li-ion rush, that major storage infrastructure projects using other technologies are forging ahead.  

Although there is clearly a limit on the number of natural salt caves that meet the geotechnical criteria, there are a number of natural gas projects that have stalled in development. Compressed air could well unlock the potential for those projects, either instead of, or alongside gas storage. it alsohas the benefit that any leaks are likely to be a little less damaging.  

The projects have come under fire for causing excess salination of the surrounding marine waters during the excavation phase, but the developers claim this is a temporary issue and the sea waters will absorb this over time to become habitable.  It seems like the short term cost could well be worthwhile if the technology proves effective. We'll watch with interest.