Performance and dynamics of active greywater heat recovery in buildings

In the effort to de-carbonize building stock, heat pumps are increasingly utilized in Switzerland, with 70% of fast-growing pump market using ambient air as source. Inexpensive and easy implement, these are, however, less efficient than their ground- or water-source counterparts. this modeling study, we aim at increasing efficiency air-source domestic greywater-contained heat. We assess performance improvement relative standard configurations across various climates, seasons, envelopes, hot water consumption patterns. The results show that annually-averaged coefficient improves by 4.1% on average – ranging from 0.6% 7.5%. This gain translates 1.8 kWh/week compressor electricity savings. Although attractive due its simplicity, proposed open-loop configuration preheating an external source only leads moderate pumps. Based results, extensively discuss compare alternative system identify several fundamental differences recovery dynamics each configuration. closed-loop systems greywater direct largest potential, although being more expensive complex implement.