Energy performance assessment of a complex district heating system which uses gas-driven combined heat and power, heat pumps and high temperature aquifer thermal energy storage

• District heating system modelling with TRNSYS software.
• Peformance comparison between an old CHP and a new integrated system.
• Energy performance of buildings is very much dependent on the heat source.
• 60% primary energy savings and 80% CO2 reduction after replacing the heat source.

The large industrialization in 70s and 80s provoked a transfer of population from the rural areas to cities. Especially in the communist countries, massive multi-storey buildings were erected, supplied by a district heating grid with big power plants. Nowadays the maintenance of such big systems is big-energy consuming and refurbishment is very hard to accomplish and therefore, in many situations, district heating is no longer profitable. We present in this paper an integrated system for local district heating, aiming to substitute the old and inefficient district system for a condominium, located in the city of Bucharest, Romania. The main paper objective is to demonstrate that the energy performance of the connected buildings could be significantly improved by changing the heat source. With CHP–HP–HT-ATES technology, initially D-energy class buildings (according to the Romanian methodology of calculation of buildings performance-Mc 001/2006) can switch to B-energy class. Moreover, the refurbishment of the buildings envelopes will help the envisaged condominium to approach the nZEB characteristics of energy consumption. A comparison between several heat production systems, in terms of primary energy and CO2 emissions is also provided.