RSE Report: monitoring the energy performance of a heating system with absorption heat pumps fired by natural gas + air source renewable energy
RSE (Italian Agency Research on Energy System)* has recently monitored a system for heating and DHWproduction consisting of two absorption heat pumps fired by natural gas + air source renewable energy (GAHP-A) combined with a modular cascade of condensing boilers. The above mentioned system is installed at Robur manufacturing facilities in Verdellino/Zingonia (BG), near Milan, in Italy.
The system is based on absorption heat pumps fired by natural gas + air source renewable energy in the heating only / high temperature version (max. temp. 65 °C), particularly suitable for retrofit applications with radiators in MFHs, light commercial and industrial buildings as well
The water temperature settings have been configured for the existing distribution system with high temperature fan coils, according to a weather compensation curve with the following operational conditions as follows:
- water target at 50 °C when external air is 5 °C,
- water target at 57 °C when external air is -5 °C.
Due to the flowrate difference between primary and secondary circuits, this means an actual outlet temperature from the heat pump ranging from 54 °C to 61 °C.
At outdoor temperature of 0 °C, GAHPs (which represent only 26% of the total installed capacity) provide more than 50% of the energy requested by the building, with outlet temperatures always exceeding 59 °C.
The graph on the right clearly shows G.U.E. (Gas Utilization Efficiency) actual trend over the outdoor air temperature, compared with the nominal data from the manufacturer.
It’s worth mentioning that:
- even at -6 °C outdoor temperature, efficiency is still higher than 105%, with water delivery temperature above 60 °C;
- considering delivery temperatures higher than 60 °C, field-measured G.U.E. is consistent with nominal G.U.E. values declared by the manufacturer, thus confirming the reliability of both the appliances and the declared data.
The RSE report is confirming:
- high performances of GAHPs, consistent with the nominal data declared by the manufacturer;
- average seasonal G.U.E. of 130%, corresponding to a PER (Primary Energy Ratio) of 1.2, including electrical consumption (during one of the coldest winter in latest 27 years);
- this level of efficiency has been reached in spite of the high delivery temperatures required by the existing distribution system (from 54 °C to 61 °C). This makes the GAHP technology particularly suitable for retrofit applications with radiators;
- also under severe winter conditions, reliability and continuity of service have been granted, with performances always higher than any boiler.