Evaluation of energy conserving measures in buildings connected to a district heating system : case studies in Gävle, Sweden

Abstract: When different energy conserving measures are implemented for reducing energy use in buildings and the buildings are connected to district heating systems, it is important that an overall system analysis is made which takes into account the effects of total change of energy use due to the energy conserving measures.The method applied in this thesis uses hourly production data for the different production units in the district heating system in Gävle, Sweden. The merit order of the different production units is dependent on the electricity spot market price. To calculate the merit order, hourly data for the electricity price is used. The marginal production unit can then be determined for each hour of the investigated year.This thesis analyzes five different energy conserving measures in a multi-dwelling building regarding how they affect the marginal production units in the district heating system. For CO2 emission evaluations, two different combinations of heat and electricity conserving measures are compared to installation of an exhaust air heat pump. This thesis also analyzes how the configuration of the electric meter affects the measured amount of self-consumed and produced excess electricity for a single-family house and for two multi-dwelling buildings of different sizes.The results show that the use of electricity is the most important objective to consider. The increased use of electricity for operation of the heat pump contributes to an increase of global CO2 emissions and the electricity produced by the solar photovoltaic installation contributes to a decrease of global CO2 emissions.The results also show that the configuration of the electric meter is important for the single-family house but negligible for the multi-dwelling buildings. The amount of produced excess electricity is high for all buildings, which means that the economic value of produced excess electricity is important for a profitable installation.