LAUSR

ABSTRACT Wastewater-source heat pump (WWSHP) applications to wastewater collection systems provide an attractive option for recovery of thermal energy. Although the idea is not new, there are few if any existing studies that talk about how the WWSHP location relative to the collection system influences efficiency. We used a wastewater collection system model and cost-benefit analysis to examine the payback time for a WWSHP relative to a conventional hot water boiler. The best location for WWSHP implementation depends on design capacity and collection system size, and the payback time could be as low as 3 years. There is a threshold of design capacity (160 kW) in the range of sizes that we investigated, and hourly variations leading to a higher electricity price could lead to a longer payback time. However, that threshold should increase and the payback time may decrease (<2 years) if larger sizes are included in the investigation.