Nearly zero energy buildings through HVAC-geothermal energy integration: Challenges and prospects

The building sector faces rising energy consumption and carbon emissions due to urbanization and rising living standards, prompting a focus on nearly zero energy building (nZEB). It serves as the backbone for achieving challenging objectives related to reducing carbon dioxide (CO2) emissions and improving energy efficiency. The current study attempts to give a thorough summary of the advancements in the subject of nZEB research. Also, it examines the emerging role of geothermal technologies coupled with heating, ventilation, and air conditioning (HVAC) systems in the context of energy use reduction. The VOSviewer software was used to find hot issues and important research axis, as well as influential researchers, sources, and countries. Detailed inspection of the current review shows that there is a growing interest by using geothermal energy utilization in space heating and cooling, witch reached to 600,000 TJ/year in 2020. The analysis reveals that 53.4% of exploitation is located in Asian countries, and 27.4% in European countries. No significant exploitation was recorded in African countries (0.4%). According to the findings, the sector has recognized the importance of energy generation, storage, and conservation in buildings. Nonetheless, the research shows that the subject is still growing, with many recently developed themes including smart buildings, zero-emission regions, and the integration of renewable energy sources. The current status and research developments in nZEB depict that some nexus topics should be studied.