Characterizing Supermarket's Thermal Demands for Integrating Combined Heat and Power Systems

摘要

Supermarkets installing combined heat and power (CHP) systems are looking to reduce utility electric consumption while applying the thermal output to offset service hot water, space heating, refrigeration subcooling, desiccant dehumidification and space cooling via an absorption chiller. Unfortunately, monitoring of supermarket CHP systems has shown that while the electric power was successfully applied, the waste heat was not properly utilized. Comparatively, CHP projects are highly successful in industry and manufacturing settings since the thermal load profiles are well understood and remain relatively constant throughout the year. For supermarket CHP systems to make economic sense and reduce carbon emissions, the thermal output needs to be nearly fully utilized throughout the year. The following paper summarizes the variation of thermal demands of stores in San Diego, CA and Boston, MA, which apply fuel cell waste heat to different thermal loads; two combined big box/grocery stores in Arkansas with no CHP system; and a supermarket in Raleigh, NC also with no CHP system. These concrete examples also provide insight into how thermal loads change when new stores or deep-dive retrofits implement increased on-site food preparation, secondary refrigeration systems, doors on medium temperature refrigerated display cases, and reduced lighting power densities. Each section is dedicated to a separate thermal demand. The authors use a combination of field monitored data and modeling to discuss in detail how to effectively apply CHP thermal output, focusing on how to maintain sufficient temperature differences (heat quality), attack persistent and large loads (heat quantity), and address fundamental design considerations.