An asynchronous distributed optimization method for energy saving of parallel-connected pumps in HVAC systems

Abstract

The energy consumption of parallel-connected pumps in heating, ventilation, and air-conditioning (HVAC) systems make up a large proportion of building energy consumption leading to an increasing attention for the pump operation. The centralized and distributed methods have been proposed to solve the pump optimization problem, which need the global clock to be synchronized and lead to the increasing system cost and idle time. In this paper, we propose an asynchronous distributed control algorithm for parallel-connected pumps in HVAC systems, which does not need the global clock, reduces the idle time and has the convergence guarantee. Under the bounded delay, the algorithm makes the optimal control decision for pumps to minimize energy consumption and meet the system demand. The theoretical analysis on convergence of the algorithm is established. The whole system is fully distributed and each pump is controlled by an intelligent node that runs identical control code and does not need to be synchronous. Numerical simulations on 6 parallel-connected pumps for different working cases are given to illustrate the effectiveness of the proposed algorithm and compare with the method from other field. The results show that our method strictly meets the constraint and minimizes system energy consumption, fully uses parallel computational resources. The running time of our asynchronous method is near 46% faster than synchronous setting.