Optimization of insulation thickness of double buried district heating pipes using the Eco-indicator method

Abstract

In order to minimize the annual total environmental impact (ATEI), an optimization model for determining the optimal insulation thickness (IT) of double buried district heating (DH) pipes was developed based on the Eco-indicator method. This model was solved by using the fsolve function in MATLAB. The effect of heat sources, operating strategies, insulation materials, buried depth (BD), nominal pipe size (NPS) and meteorological conditions on the optimal values was analyzed. The effect of heat source unit heating energy consumption, insulation material environmental impact point (EIP), heat source EIP, and insulation material service lifetime on the optimal values was analyzed in the sensitivity analysis. Results confirm that the developed model can be applied to obtain the optimal values. Coal-fired combined heat and power plant (CFCHPP), constant mass flow rate (MFR) operating strategies, glass wool and increase in BD are beneficial to the environment. As the NPS increases, the optimal IT does not linearly increases, while the minimal ATEI increases. Larger optimal values correspond to colder meteorological conditions. In the sensitivity analysis, the heat source unit heating energy consumption and heat source EIP have a greater effect on the minimal ATEI, while sensitivity parameters have a great effect on the optimal IT.