Hydrogen enriched natural gas blends in gas absorption heat pumps: seasonal experimental characterization and numerical modelling

The decarbonisation of residential heating systems requires low-carbon solutions capable of exploiting existing natural gas infrastructures without compromising device performance. In this context, the present study investigates the energy and environmental behaviour of a commercial gas absorption heat pump fuelled with hydrogen-enriched natural gas blends under real operating conditions. Experimental campaigns have been conducted during both winter and summer operation by varying the hydrogen volumetric fraction from 0% to 25%. In parallel, a MATLAB-Simulink thermo-physical model and a data-driven nonlinear regression model for NOx prediction have been developed and validated against experimental measurements. Results show that hydrogen enrichment does not significantly affect gas absorption heat pump energy performance, while substantially reducing pollutant emissions. At 25% vol. H2, CO, CO2, and NOx emissions decreased by up to 30%, 7%, and 32.2%, respectively. Overall, the findings demonstrate the technical feasibility and environmental benefits of moderate H2NG blending in commercial thermally driven heat pumps.