Journal of Korean Institute of Architectural Sustainable Environment and Building Systems ISSN:1976-6483(Print) 2586-0666(Online) 한국건축친환경설비학회논문집

Although ground-source heat pump (GSHP) system is promising for implementing a zero-energy building, the high initial cost of the system limits its applications. Most of all, reducing the drilling cost, which accounts for more than 50% of the total installation cost of the GSHP, is necessary. In other words, reducing the length of borehole can most effectively make GSHP affordable. In the design of the ground heat exchanger, a modification of building heating and cooling loads, which has not been considered carefully in previous studies, can be promising. Accordingly, this study aims at proposing load modification approaches and investigating their feasibility. First, heating and cooling loads were calculated for the medium office building using EnergyPlus 7.2.0, and based on them, the borehole length was determined using GLHEpro 5.0.4. Second, peak and total of heating and cooling loads were modified by changing values of design variables related to building envelope, such as thickness of insulation material, U-value, and SHGC of window and infiltration rate. Finally, the results of peak and total of heating and cooling loads were classified and effects of each load pattern on the borehole length were analyzed. The results showed two major insights for the application of load modification strategy on reducing the borehole length. Even lower SHGC did not reduce the heating peak load but contributed to an alleviation of thermal accumulation of the ground. Consequently, the borehole length was reduced by 16.0%. Lowering of the infiltration rate was intended to reduce peak heating load; however, it increased the borehole length 1.6%. Therefore, besides a reduction of peak load, a balance between total heating and cooling loads was concluded to be essential for reducing borehole length. Additionally, proper load modification strategy needs to be carefully investigated owing to the difference in the loads pattern caused by the climate of a region, building type, and envelope configuration.