Improving energy efficiency of ground thermal energy systems by reducing drag inside pipes

Abstract

AbstractAt specified depths, ground temperature remains almost constant at 15°C, above atmospheric temperatures in winter and below those in summer. Ground thermal energy systems technology circulates water or brine through a heat‐collection tube buried underground and uses the ground thermal energy for air conditioning. However, depending on the facility, the total length of the heat‐collection tube can be several hundred meters. As a result, the pump can require significant electric power. In this study, we adopted a drag‐reduction technique using a cationic surfactant and a counter‐ion system. The optimal addition conditions of additives were investigated with a laboratory‐grade device. We also investigated corrosion inhibitors that do not interfere with the drag‐reduction effect. According to demonstration tests using practical ground thermal energy systems at two locations in Japan, we found that pump power consumption could be reduced by 10%–20% with suitable additive conditions.