Economic analysis of integrated ground source heat pumps on a shared ground loop

Abstract

An integrated geothermal system in which heat pumps for air conditioning and hot water both share the same ground loop was proposed in our previous study. Although this system produced electricity savings of 15% compared to a conventional system in which the two heat pumps operated on their own ground loop, practical requirements regarding further lowering the operation cost of the integrated geothermal system and the possibility of the energy savings being low during winter initiated further investigation into potential energy conservation measures at no initial cost increase, if possible. Outdoor reset control for hot water supply and sequential heat pump operation, both of which could be included at no extra cost, were subsequently targeted as potential measures for greater electricity savings and economic feasibility. When these measures were incorporated into the integrated geothermal system, electricity savings of approximately 25% during the heating season compared to the conventional system were predicted. Eventually it led to annual electricity savings of about 25% compared to the conventional system, which is up to 9.6 million South Korean won a year at today's rates. Additionally, it reached the break-even point earlier than one year after installation.