Kostnadsanalys av investering i en fjärrvärmeackumulator : Ett underlag för beslut om utökade lagringsmöjligheter vid Bomhus Energi

The district heating system of Gävle will within a few years likely undergo changing routines in production and a rising demand for heat, which will increase the need for flexibility and availability in the production units. It is therefore relevant to study the economic potential of installing a thermal storage at the largest production unit in the system; Bomhus Energi. For storing heat over short time spans in district heating networks it is common to use heat accumulators. A model of the district heating system was created within an existing model structure. The system was simulated in scenarios where electricity price, electricity certificate price and heat demand were varied. For each scenario four different sizes of heat storages were tested. The reduction in production cost was used to calculate the payback time for each accumulator. None of the accumulators received a payback time shorter than the economic lifespan of 20 years. The second largest storage (4000 m3) received the shortest payback times, the best result being 23 years in the scenario of increased heat demand. The results for the largest storage (20000 m3) indicates on a large potential under certain circumstances. The study concludes that a heat accumulator would not be profitable under the investigated circumstances. However, it indicates that there are cases where a heat storage of the right size could be a good investment. For further study it is recommended to investigate the case of greater heat demand and accumulators with a volume between 4000 - 20000 m3