This study introduces a novel transcritical CO2 pumpless Rankine power generation cycle based on the thermal compression concept, utilizing low-temperature renewable sources. The investigated theoretical system consists of a 5 kWe unit incorporating the aforementioned working cycle coupled with a 50 m2 evacuated tube solar collector arrangement installed on the rooftop of a multifamily house in Athens, Greece. The proposed innovative configuration is parametrically analyzed for different hot water inlet temperature levels ranging from 70 to 120 °C and its efficiency is compared to the typical Organic Rankine Cycle (ORC) topology employing different conventional refrigerants. The energetic assessment is made using validated mathematical models developed in MATLAB integrating the CoolProp library. The derived results show that the investigated topology increases the performance figures compared to the baseline system for all the examined refrigerants, leading up to over 15% thermal efficiency enhancement for operation under low heat source temperatures. Finally, the year-round operation of the proposed system generates up to 5221 kWh/year for the building.
Syngounas et al. (2026) studied this question.