Buildings' energy efficiency measures effect on CO2 emissions in combined heating, cooling and electricity production

Valid tools for building designers and building simulation professionals to evaluate transparently CO2 saving potential of energy efficiency measures are needed to achieve CO2 reduction targets. Earlier studies have pointed out existing tools' weak interconnection between buildings and energy systems and the lack of transparency. This study developed and validated a multimode district energy system model including district heating, cooling, CHP and heat pumps, and connection to a national power generation, to evaluate buildings' energy efficiency measures effect on CO2 emissions. A calculation example demonstrates how important it is to take into account an interconnection between buildings and a wider energy system. Implementation of the robust model as a calculation tool is fully reported and validated against the measured data so that it fulfilled the calibration criteria. Calculation tool overestimated regional CO2 emissions only by 3% with small variation and correlation to real data was very good. Calculation example shows that buildings' energy efficiency measures effect on CO2 emissions was highly dependent on CO2 intensity of marginal national electricity generation and electricity import when regional CHP production exists, and existing building stock was considered. Thus, interconnection between buildings, regional energy production and national electricity generation must be taken into account if regional CHP production and district heating demand changes exist. Annual average CO2 factors failed to provide reliable results when the CO2 saving potential of energy efficiency measures was evaluated and therefore should not be used.