Improvement of the Performance of Mechanical Ventilation Systems with Earth-Air Heat Exchangers (EAHEs) for Detached Rural Houses in Severe Cold Regions

Natural ventilation with manually opened windows is insufficient to ensure adequate indoor air quality in rural houses situated in Chinese severe cold regions, especially during the winter season. Major challenges in implementing high-efficient mechanical ventilation systems in these houses include the substantial heating requirements for preconditioning the incoming outdoor air and the frozen problem in air handling units. Earth-air heat exchanger (EAHE), which utilizes geothermal energy, is a promising technology to help preheat or precool the supply air. This study thoroughly investigated the feasibility of EAHE applied in severe cold regions, focusing on its heating performance and effects on building systems. A detached rural house in Harbin was selected as the reference house. Two mechanical ventilation cases were established and simulated in IDA ICE, involving one traditional exhaust ventilation case and one balanced ventilation case with an EAHE and a heat recovery unit (HR). The results show a strong and opposite relevance between outdoor temperature and the supply air temperature difference of outlet/inlet EAHE. Besides, compared to the case with exhaust ventilation, the case of balanced ventilation with both EAHE and HR could reduce total heating demand by 20% with an increased annual electricity consumption of 11 kWh/m2.