EVALUATION OF THE OPTIMAL SOLAR FRACTION FOR A DISTRICT HEATING SYSTEM

Abstract

This paper addresses the issue of promoting solar thermal energy in district heating systems and determining the optimal solar fraction in the system heat generation. Despite the bad soviet past of this technology, it is time to insist on promoting a new generation of district heating systems (fourth one), free from the shortcomings of the past, as pillars of the future decarbonized energy systems, based on the use of renewable energy sources and heat recyclable waste. The problem of establishing the solar fraction, integrated in a district heating system is an optimization problem. Even if solar radiation is free and available virtually everywhere – solar technology and infrastructure (solar collectors, heat reservoirs, underground heat accumulators, pumps for circulating the working agent, heat pumps for discharge, etc.) are quite expensive. Based on the application of the criterion of minimum total expenditures, a mathematical techno-economic model was developed, which allowed to obtain an analytical expression for the calculation of the solar optimal fraction, on the one hand, and the share of hot water boilers on natural gas or biomass – on the other hand. This assessment was made on both the power and energy dimensions. The numerical calculations performed demonstrate the application of this analytical tool in the pre-feasibility studies of solar district heating systems.