The operational aspects, optimal operating strategies and economic viability of a single and dual thermal storage HVAC system (hot water and chilled water) in a large commercial structure was studied. A computer simulation model of the HVAC thermal storage system of the Electronic Associates, Inc. (E.A.I.) office buildings in Long Branch, N.J. was developed and used in conjunction with actual operation data to define and test optimal modes of space conditioning systems with thermal storage.

Thermodynamic models of each component of the system were incorporated into the computer simulation model, which may be easily programmed for a wide range of HVAC thermal storage systems and modes of operation.

An optimal two tank simulation (as opposed to a no storage system) of the EAI system reduced peak electric demand (Kw) by 36% in the summer and 75% in the winter. 50% of the yearly on-peak (10 a.m. to 10 p.m.) energy (Kwh) requirement was shifted to off-peak times. Total electric energy (Kwh) required was reduced by only 3%. The total building HVAC operating costs were reduced by 39.9%, based on an on-peak demand charge of $10.10/Kw; this produces an estimated simple payback of 4.8 yr for the two tank system with its associated piping and pumps. These results indicate a significant potential for thermal storage as an alternative for reducing on-peak demand and energy requirements and decreasing HVAC operating costs.