A Stepwise Approach Based Optimal Energy Utilization Scheme for HVAC Secondary Chilled Water Pumps in Commercial Buildings

Sandali Walgama, Sisil Kumarawadu, Chandima Dedduwa Pathirana


In many countries, buildings are responsible for as much as 40% of total energy consumption and in many commercial buildings, about half of total electricity is consumed by Heating, Ventilating and Air Conditioning (HVAC) systems. As a result, many research efforts have been made over the years aiming to maximize building energy efficiency and savings. This paper proposes a novel strategy to enhance the energy savings in the HVAC secondary chilled water pumps based on the required water flow variations due to the changes in the cooling load of the building. The resulting power usage minimization problem was solved using a stepwise approach that reduces the complexity, in order to determine the optimal number of pumps to be operated and their optimal operating speed also ensuring that the flow requirement and other operational constraints are duly satisfied. The pump characteristics were mathematically modelled, and the proposed method was validated comprehensively via simulation and case studies. As per results of the first case study, the suggested method offers a 15.26% reduction in consumed pump energy compared to that of the cascading method used in a large commercial building. The second case study provides a performance comparison of the proposed method with the Particle Swarm Optimization (PSO) method and the proposed strategy shows a 1.78% energy saving over to the PSO method with a comparatively small execution time. Therefore, a highly efficient, safe, and reliable pump operation can be assured with the proposed method. This approach is simple to implement, reliable, robust, efficient, and suitable for energy-based optimal control of HVAC secondary chilled water pumps in commercial buildings.


Chilled water system; Energy optimization; HVAC; Parallel pumps; Variable speed

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