Danitary Hot Water (DHW) demand will remain similar in spite of the effort done to reduce energy consumption in houses. Heat pump (HP) is a potential technology to produce DHW due to its high efficiency. However, DHW application is characterized by high secondary temperature lifts for what HPs have been using transcritical cycles.

Under the European project “NEXTHPG”, a water-to-water HP prototype (WtWHP) was developed. This HP stands out for: its high efficiency, the recuperation of the heat from wastewater mass flows and the use of natural refrigerants with subcritical cycles (propane).

The main objective of this work is to design a DHW production system integrating this WtWHP, a preheating heat exchanger, and a storage tank including the control strategy that leads to the maximum CO2 emissions reduction.

Results for a multifamily house show a potential reduction of the CO2 emissions up to 55% if the proper sizing and control strategy are used.