Influence of daily temperature behavior on earth-air heat exchangers: A case study from Aichi, Japan

Urban climate modifications are evolving the heating and cooling regime. Earth-air heat exchangers (EAHE) are a potential solution in addressing these needs opposite of conventional approaches which are intrinsically ill-suited for the urban environment. Heating and cooling were classified by detrimental and beneficial conditions based on a degree hours approach for a multi-tube EAHE system in Aichi, Japan. Linear models were also constructed for a winter and summer season based on the inlet air and surrounding soil temperatures. Inputting temporally decomposed model inputs (annual, weekly and random) into the linear models highlighted the importance of diurnal inlet air temperature variations on producing beneficial cooling in the summer. Weekly signals in the inlet air temperature also perturbed the surrounding soil, although this had a smaller effect on system performance relative to inlet air temperature variations. Beneficial cooling was maximized during the diurnal temperature maximum when inlet air was typically warmer than the soil. This implies a susceptibility to increased cooling needs during daily temperature minimums. As a result, urbanizing sites where enhanced morning cooling may arise should consider the impacts of urban climate during the pre-design stage.