Integration of district heating systems with small modular reactors and organic Rankine cycle including energy storage: Design and energy management optimization

Abstract

The heat-only small modular reactor (SMR) concept is one of the potential carbon-free solutions for replacing fossil fuel-based district heating systems (DHSs). This idea faces an economic challenge (high levelized cost of heat) due to high capital cost and low capacity factor (because of demand fluctuations) in stand-alone operation mode. This study proposes integrating DHSs with heat-only SMRs and organic Rankine cycle (ORC) electricity generation to maximize the system's economic profit. Heat storage, gas boiler, and electricity storage are candidate units for optimizing the system's energy management. The developed optimization method is a mixed-integer nonlinear problem (MINLP). The objective variables are the equipment's design capacities and hour-by-hour operation, and the net present value (NPV) is the objective function. Considering a typical DHS in Czechia (peak of 41 MWt), the optimized integration found comprises a heat-only SMR (Teplator-150 MWt), an ORC power plant of (20 MWe), heat storage of (10000 MWth), a gas boiler of (3.4 MWt), and (20 MWe/120 MWeh) electricity storage. This system and its energy management optimization enhanced the SMR's capacity factor (from 10 % to 83 %), and the NPV changed from a loss of 50 M€ to a gain of 357 M€ compared to the basic heat-only supply system. The sensitivity analyses showed that the size and technology of ORC, the interest rate, and the electricity price are the most important factors in the system's economic viability.