Variable-speed pumps simulation in EPANET

ABSTRACT In water distribution systems, energy savings can be achieved by substituting fixed-speed pumps by variable-speed pumps (VSP). The high costs of installation and operation of VSP require a preliminary economic assessment of the project, which is usually complemented by the use of a computer simulation software for hydraulic analyses of the system. One of the most used software programs for this purpose is EPANET 2, which is inaccurate when computing VSP efficiency. This is because the software does not take into account the changes in the pump efficiency curve when the pump speed is changed. In this study, a routine for calculating VSP efficiency, based on literature methodology, was implemented in the source code of EPANET 2. The influence of the new routine on the results predicted by the software for efficiency, power and energy consumption of VSP was evaluated in simulations with a hypothetical network. The results show that the original version of EPANET 2 tends to underestimate the efficiency and thus overestimate the power and energy consumption of VSP. The modified version of EPANET 2 provides a better prediction of VSP behavior; thus, its use is recommended in the simulation of water distribution networks equipped with VSP.

摘要：在配水系统（water distribution systems）中，通过以变速泵（variable-speed pumps，VSP）替代定速泵（fixed-speed pumps），可实现节能目标。但变速泵的安装与运行成本高昂，需对项目开展初步经济评估（economic assessment），该评估通常辅以计算机仿真软件（computer simulation software）进行系统水力分析（hydraulic analyses）。目前应用最广泛的此类软件之一为EPANET 2，但其在计算变速泵效率时存在精度不足的问题，原因在于该软件未考虑泵转速变化时泵效率曲线（pump efficiency curve）的相应调整。本研究基于现有文献中的方法，在EPANET 2的源代码（source code）中嵌入了变速泵效率计算程序。通过构建假想管网（hypothetical network）开展仿真实验，评估了该新增程序对软件输出的变速泵效率、功率（power）及能耗（energy consumption）预测结果的影响。结果表明，原版EPANET 2往往会低估泵效率，进而高估变速泵的功率与能耗；而修改后的EPANET 2可更精准地预测变速泵的运行特性，因此推荐将其用于配备变速泵的配水系统仿真分析。