Energy renewal of the heating system in a residential and office building in Bjelovar
In the basement of a residential and office building in Bjelovar there is a boiler room with two gas boilers, approx. 40 years old. One boiler is operational (1.3 MW) and the other serves as a spare one (0.5 MW). Boilers and burners are older, with high losses, which is reflected in heating costs. The pumps are old type three-speed, resulting in heating problems of the 10th floor apartments. The obsolete system created problems of leakage and replenishment of the open expansion tank on the roof of the building and the problem of heat transport from the boiler room to the substation (old and poor insulation).
The heating of the rooms in temperature range 80/60 ° C is done by a radiator system (gooseneck radiators), which in the basement boiler room is divided into two branches, one of which is for the residential building (10 floors) and the other is for the office building (4 floors).
As part of the energy renovation of the office building, a ROBUR GAHP-A absorption heat pump powered by gas and air and two AY condensation heaters were installed on the roof for external installation.
The absorption heat pump powered by gas and air has a 164% efficiency (COP 4.1) efficiency with the use of 40.0% energy from renewable sources (air), and it works to cover the base load for the entire heating period while the condensing boilers (efficiency in heating mode 105%) activate depending on the thermal load of the building, ie they serve to cut peak consumption. The total installed heating power is 105 kW. With the initial investment costs for the new equipment and installation and the need for one-year regular maintenance of the heating plant before the heating season, the payback period is 7.7 years.
As part of the energy renovation of the residential building, 12 AY condensation heaters were installed on the roof for outdoor installation (105% heating efficiency) with a total installed power of 420 kW in heating at 80/60°C.
The cost of purchasing and installing the heating system is financed by a commercial loan (4% interest for energy renovation) through the maintainer of the building, and the loan is repaid through an increase in the reserve to 10 years. The cost of heating after the energy renewal is reduced by approximately 35%, thus canceling the increase in the loan repayment reserve. The new system does not require a firebox, but needs to have a heating plant serviced once a year before heating. With the initial investment costs for the new equipment and installation, the payback period is 10.3 years.