A stochastic load demand-oriented synergetic optimal control strategy for variable-speed pumps in residential district heating or cooling systems

Abstract

For a residential district heating or cooling (RDHC) system in the “part-time part-space (PTPS)” service mode, the thermal load demands of end users are notably stochastic.To reducing the energy consumption of centralized variable-speed pumps (VSPs) in RDHC systems, this study presents a stochastic load demand-oriented synergetic optimal control strategy for VSPs in RDHC systems. In this strategy, the spatial and temporal distribution of the stochastic load demands (SLDs) in a residential district is predicted using the stochastic occupant behavior (SOB) method. The operation regulation of the RDHC system is mathematically described based on graph theory. A synergetic optimization mathematical model is developed based on each end user’s SLD as well as the operation regulation characteristics of the RDHC system. This synergetic optimization mathematical model is subsequently solved using particle swarm optimization (PSO) algorithm. Thus, an optimal hourly pump frequency ratio is obtained. A case study is performed to comprehensively compare the proposed synergetic optimal control (SOC) strategy with the conventional constant pressure difference control (CPDC) strategy. The results show that for the same load demands, the energy consumption of the pumps throughout the heating season under the SOC strategy is 62.9% lower than that under the CPDC strategy.