Small District Heating Systems

Sammanfattning: The objective of this work is to identify, from an economical point of view, the optimal system design and operation strategy for the district heating of a small residential area. The applied methodology is an overall approach on the heat distribution system, the house connection and the space heating system in the building, i.e. all parts are regarded as one system.

To comply with this task, dynamic simulation which takes into account the interaction between different components is applied. Existing simulation model components and new developed model components for all parts of the small district heating system in question are combined to a system as a whole to predict the thermal performance for the period of one year.

To ensure that the valid component and system models are in accordance with the performance of real systems, measurements from two small district heating systems were compared with the calculated results. The outcome is a calibrated simulation model. The calibrated system simulation model was then generalised by using a typical space heating and domestic hot water load and weather data for the location of Göteborg.

Using the generalised system simulation model a thermal analysis of common system alternatives was carried out. Three different temperature levels for two district heating network types, 2-pipe and 4-pipe, and house heating system were analysed to ascertain distribution heat loss and electricity consumption for pumps.

The result of the thermal analysis was combined with typical costs for system parts, operation of the system and for covering the heat demand to calculate annual heat costs for each system. A sensitivity analysis regarding annual heat costs was carried out for the investigated system alternatives by varying major cost and design factors.