Hi users,

In a project (hotel, under "residential") to go for LEED, the proposed heating system is combined boiler and water source heat pump. Water in the loop is at first heated by the boiler (with COP of 0.9) and then as act as circulating water in the WSHP system (with COP of approx. 3.7) so the system COP is expected to be much higher than using boiler only. Now, the client wants to know how much % of cost savings they can get.

In common cases, the heat source in heat pump system is free (either air or ground), it is the first time happened to me that the heating source is not free. I thought about treating hot water from the boiler as domestic hot water, so the heat source for HP is, as if, free. However, the amount of heat as well as the heating period is hard to define. I thought about using PTAC for cooling and a boiler, with extraordinary high COP of 0.9*3.7=3.33, for heating, but the amount of electricity consumed by heating cannot be reflected this way...

Could anyone give me some suggestion about how to model this combined system, which could make sense under GBCI's eyes? And which system shall I choose as Baseline?

Many thanks,

Rick