Advances in standalone and hybrid earth-air heat exchanger (EAHE) systems for buildings: A review

[Display omitted] •EAHE preheating/precooling potential for reducing buildings energy consumption.•Discussion on the chief design and operation aspects that affect EAHE performance.•Survey on advances in hybrid EAHE systems to improve the use of renewables.•EAHE systems coupled with other active and/or passive techniques.•Inventorying of research gaps and emerging trends in the EAHE research domain. This paper provides an up-to-date survey on recent advances in earth-air heat exchanger (EAHE) systems for buildings, and presents systematic information on the main design parameters and operation conditions that affect the overall performance of the technology. This review also aims at providing room for the discussion on how this technology can be used in standalone and/or hybrid schemes, i.e., EAHE systems coupled with other active/passive techniques, such as air conditioners, air source heat pumps, heat recovery units, mechanical ventilation systems and air handling units, evaporative cooling, air humidity control devices, photovoltaic panels, building integrated photovoltaic systems, solar air heaters and heating ducts, solar chimneys, wind towers, building thermal mass and phase change materials. It was concluded that further research is required to provide reliable design guidelines for different climates, EAHE configurations, typologies of buildings, sorts of construction, types of soils, and finally, to overcome the main drawbacks of the technology that have restrained its worldwide dissemination. Further studies are also required to numerically and/or experimentally assess the thermal performance, the environmental benefits, and the economic viability of innovative hybrid EAHE systems, since a great research gap persists on this matter.