UTILIZING BUILDINGS AS SHORT-TERM THERMAL ENERGY STORAGE

Paper in proceeding, 2014

Heat demand in a district heating system can exhibit significant variation within one day, which sets problematic conditions for efficient heat generation. Short-term thermal energy storage can decrease this daily variation and make the conditions for generating heat more favourable. By periodically overheating and under-heating buildings, causing small variations in the indoor temperature, their thermal inertia can be utilized as short-term thermal energy storage. This study presents the results from a pilot test where the potential to function as short-term thermal energy storage was tested in five multifamily residential buildings in Gothenburg, Sweden. These results are then up-scaled to study the consequences for a whole-district heating system from a large-scale implementation. The signal from the outdoor temperature sensors in the test buildings were adjusted in different cycles over a total of 52 weeks. The delivered heat and indoor temperature were measured during the test. The results show that heavy buildings with a structural core of concrete can tolerate relatively large variations in heat delivery while still maintaining a good indoor climate. Storing 0.1 [kWh/m2 floor area] of heat will very rarely cause variations in indoor temperature greater than ±0.5°C in a heavy building. Utilizing about 500 substations for short-term thermal energy storage in large residential buildings would provide capacity for storing heat equivalent to that of a hot water storage tank with a volume of 14,200 [m3] for the city of Gothenburg. This would decrease the daily variations in heat load by 50%, reduce the need for peak heat generation, and reduce the number of starts and stops of heat-generation units.