scope:

INTRODUCTION

Background

Historically, thermal energy storage (TES) has been applied to large chiller-based systems in the form of either chilled water or ice storage. The system analyzed in this manuscript is a packaged refrigerant-based ice-on-coil storage subsystem, designed for use with Standard Direct Expansion (DX) equipment. "Standard DX Equipment" means unitary, direct expansion A/C equipment, including but not limited to, split, mini-split, packaged, and single package vertical unit systems. As such, this design is termed a "Unitary Thermal Storage System," or UTSS. It shares many of the same benefits as the chiller-based systems, but is designed to work with standard DX equipment in both new and retrofit applications, and in a manner that can improve the combined system's overall efficiency. As with the performance of standard DX equipment, specific climates and application conditions will impact the actual amount of net energy used. Measuring the performance of systems in the field is challenging due to the broad range of operating conditions, indoor and outdoor environmental conditions, as well as the range of uncontrollable variables present in the field, such as building design, equipment maintenance, and allowable variations in manufactured OEM equipment itself. For this reason, performance ratings of standard DX systems are lab based, and tested over a well-defined range of controlled operating conditions. The lab data can then be used to evaluate the system's operation over a broad range of conditions, both static and dynamic. This in turn can be used to predict performance and efficiency in real-world applications. As a final step, actual field data can then be analyzed to see if it is consistent with predictions, and to provide indications for further investigation.