18 May 2017

P.4.3.4 Translating cycle performance to system-level efficiency for sorption heat pumps


For sorption heat pumps, a gap often exists between metrics of efficiency provided in the literature (typically COP) and system-level performance expressed according to various national minimum energy performance standards and labeling schemes. Engineers and decision makers would benefit from a convenient, even if approximate, translation between the two. Focusing on fuel-fired heat pump systems, this work bridges the gap through a straightforward analytical model relating cycle COP to system performance, while incorporating practical system-level parameters. These parameters include burner efficiency, electrical power consumption, standby losses, cyclic losses, and flue gas heat exchanger effectiveness. Separate translations are provided for water heating and space heating for single and double effect water/LiBr and ammonia/water. The EES&L metric is generally 15-35% lower than the cycle COP. For metrics that are based on primary energy, the electrical consumption of the fuel-fired heat pump is of high importance. The burner efficiency is important in all cases.