Although in theory STES can be applied at any scale ranging from a single home to a sizeable community, (10) its economics--and its efficiency--improve appreciably with scale.
STES saves energy by storing thermal energy that would otherwise be wasted and using it to meet a significant portion of building space heating, water heating, and/or cooling loads.
For example, in solar thermal applications, the solar fraction equals the portion of the heating loads that the STES can provide.
The efficiency of STES, defined as the portion of heat transferred into the STES that remains available to meet loads, also varies significantly.
STES systems do not realize their full energy savings potential immediately.
STES has been under investigation since at least the solar boom in the 1970s, but relatively few systems exist.
Solar thermal STES systems have particularly high estimated and projected costs per unit of thermal energy provided.
Cold STES may have more favorable economics than warm STES, (1) presumably because it displaces more costly electricity (relative to thermal energy) while also achieving significant electric demand reductions.
4,6) Furthermore, successful design and implementation of STES requires close integration between hydrologists, geologists, engineers, and architects.