Dynamic modeling of heat pumps for ancillary services in local district heating concepts

This paper aims to describe the steady-state and dynamic heat pump models developed to study their abilities in ancillary services as well as the interconnection between these, electrical boilers and thermal storage with the aim to balance power and heat production for a given case.
An hourly steady-state system model was developed to understand the overall operational characteristics of the system for a given heat demand case in the area Kolt-Hasselager-Ormslev near Aarhus in Denmark. The model showed an annual average COP above 3,5 for a serial connected heat pump system.
Detailed thermal and dynamical models of the heat pump system were developed. The models show that it will be possible to use heat pumps successfully in ancillary services. The turn-up is unproblematic but the turn down of the heat pump will be limited in a nonliquid overfed system due to risk of liquid formation in the evaporator, requiring additional heating.