Development of an integrated underfloor heating system model in TRNSYS and performance assessments

In this study, a transient model for a solar underfloor heating system with a sensible heat thermal energy storage (SHTES) system to meet the heating demand of a residential building is developed in TRNSYS software. As a novelty in the current model, rather than using the built-in modules in the software, an in-house MATLAB routine is implemented in TRNSYS to simulate the spatial and temporal variations inside a 2D slab-type SHTES tank. Long-term dynamic simulations are conducted to discuss the influences of the design and working parameters on the (i) energetic and exergetic performances, (ii) solar fraction, and (iii) CO2 emissions associated with the alternative underfloor heating systems. Parametric analyses are performed for climatically different locations, such as Izmir (Csa: Hot-summer Mediterranean climate) and Erzurum (Dfb: Warm-summer humid continental climate). Variations in charging loop mass flow rates have minimal impact on the overall system performance in Izmir and Erzurum compared to other design and working parameters. The highest energy efficiencies of the solar-aided underfloor heating system for Izmir and Erzurum are achieved for a comfort temperature of 20 degrees C with 32.9 % and 24.6 %, respectively. Regarding exergy efficiency, the highest was determined as 4.04 % with a 23.5 degrees C comfort temperature in Izmir and 3.89 % with a comfort temperature of 20 degrees C in Erzurum. As a final result of the environmental assessments, integrating solar SHTES, especially with a natural gas-based auxiliary heater, significantly reduces CO2 emissions by 99.6 % and 50.0 % in Izmir and Erzurum, respectively.