Study on the in situ performance of a 60 kW condensing gas boilers thermal installation and economic assessment

Abstract

Condensing gas boilers currently represent the most advanced solution for heating based on combustion of fossil fuels from both efficiency and pollution points of view. Besides, compared with the district heating, condensing gas boilers make possible the entire management of the heat supply function by the real heating needs. Subsequently, minimization of the heating cost is possible. In this view, one of the buildings of the “Gheorghe Asachi” Technical University of Iasi was disconnected from the district heating and two condensing gas boilers – one of 25 kW and the other of 35 kW nominal output – were connected to the heating network to ensure the heat supply. A performance and economic analysis of the thermal installation with the two boilers, based on in situ experiments, was performed. The analysis was performed for nine operating regimes described by boilers flow water temperatures from 80 °C to 40 °C. Efficiency (in terms of higher heating value of the fuel) had varied from 86.7 % to 97.5 % and the price of thermal energy produced with the two boilers proved to be 21…30 % lower than the price of thermal energy coming from the district heating system. The annual heating savings are estimated to be 642…907 Euro/year, which induce a payback period of 1.6…2.3 years with strict reference to the investment represented by the two boilers.