Optimum utilization of power plant waste heat by nearly-zero exergy district prosumers for minimum carbon footprint

Abstract

This paper presents a new exergy-based model for minimizing the total carbon dioxide emission responsibility of district heating systems connected to thermal power plants. An optimal exergy balance can be determined between the degree of low-exergy prosuming buildings on the demand side and the utilization rate of waste heat from a power plant on the supply side. Therefore, the optimum degree of prosuming buildings and the utilization of waste heat in a district also minimize the embodied emissions and costs of prosuming buildings for sustainable growth. Following the massive earthquake in 2023 in the Afşin-Elbistan province located in the Southeast region of Türkiye, 10,000 apartments to be heated by individual boilers are compared with an alternative design using this model. This alternative design features low-exergy prosumer buildings integrated with the waste heat of the 1,355 GW lignite power plant. The waste heat is obtained from the nearby return pipe of the water-cooling system, which is connected to a river head, located 30 km away. The model played a crucial role in determining the optimal degree of low-exergy building design, which simultaneously minimizes the carbon footprint of the power plant and the embodied emissions of such buildings, thereby facilitating the optimal level of renewable energy sources for prosumption. A new exergy star green metric is introduced, with a maximum rating of five stars. The new model assigned an optimal of three stars for the alternative design, which minimizes the carbon footprint by reducing carbon dioxide emissions by 79 %.