Measured Performance of Thermal Storage Systems: One UtilityTMs Experience

In an effort to integrate the measurement of savings into the normal procedures of qualifying for utility incentives, New England Electric has developed stringent end-use metering requirements for the installation of all cool thermal storage systems. Payment of incentives has been made contingent upon successful demonstration of data collection capabilities. Measurements include total cooling system demand and chilled water temperatures and flow rates. Using the metered data to calculate building cooling load being met by the storage system an avoided demand is calculated. This paper presents the results of the analysis of data collected from nine thermal storage systems installed over the last three years. In addition, insights gained from the commissioning of a number of systems are examined. Results indicate that measured demand reductions are lower than those estimated in design or feasibility studies. The main reason for lower results is over-estimation of cooling loads. As demonstrated in the data presented, the standard practice of oversizing HVAC systems must be taken into account in estimating savings and in the calculation of incentives. Lessons learned in this study are applicable to the design of any HVAC system efficiency program.