Using High Performance Insulation in District Heating Pipes

It is necessary to improve the distribution of district heating for the future in order to maintain its competitiveness. In recent decades a number of high performance insulation materials have been developed. This paper presents an investigation of high performance insulation materials in district heating pipes. Three different paths were chosen as the most promising; mixing aerogel granulates in polyurethane foam, hybrid insulation with layers of aerogel blankets within the polyurethane, or hybrid insulation with vacuum insulation panels. The thermal conductivity of aerogel have been measured to as low as 13 mW/(m∙K) and the thermal conductivity through the center of a vacuum insulation panel can be as low as 4 mW/(m∙K). These can be compared to polyurethane which has a thermal conductivity around 25-26 mW/(m∙K). Prototypes of district heating pipes were produced in laboratory and the thermal conductivity of the pipes was investigated. The effective thermal conductivity of the hybrid insulation of the district heating pipes by aerogel blankets or vacuum insulation panels were 15-20% less than pipes insulated with pure polyurethane. The high performance insulation materials are still expensive. However, the result of a simple payoff time analysis indicates that the vacuum insulation panels already might be economically beneficial the tested dimension of district heating pipes