The value of flexibility for large-scale heat pumps in district heating systems - a survey on technical constraints and economic opportunities

Abstract

Large scale heat pumps and electric boilers are commonly treated as a measure to increase flexibility in district heating systems. The transformation of the energy market towards more volatile renewables in combination with our climate protection goals demands for this additional flexibility. In this thesis, the economic value of flexibility for large scale heat pumps is assessed by identifying essential parameters and comparing the effects of differently configured heat pumps on conventional district heating systems. By using four different base systems in a wide range of sizes and a variety of low-temperature heat sources it is tried to obtain general results. A MILP model is introduced which optimizes the combined dispatch of heat pumps, conventional heat generators, and heat storages on an annual basis with respect to the specific operational properties of heat pumps. It is shown that the flexibility of heat pumps bears a considerable economic benefit for typical Austrian district heating systems and that this benefit is heavily dependent on a joint operation with CHP units. Furthermore, it is found that the most compromising factor for the flexibility of heat pumps is the competition with baseload generators and renewables during low demand times. A comparison with generation portfolios without P2H devices shows the positive impact of large-scale heat pumps on the CO2 footprint of district heating systems. However, it is revealed that operational flexibility does not necessarily further improve the emissions situation.