Pressure regulation and energy recovery in water distribution networks using pumps as turbines

Abstract

Water distribution networks (WDNs) are considered a potential renewable energy source, as they have more than enough pressure energy to deliver water to users. To control excessive pressure, WDNs are commonly divided into district metered areas (DMAs) with pressure-reducing valves (PRVs). The energy wasted by PRVs can be recovered using pumps as turbines (PATs). However, selecting the appropriate pump remains a challenge, as it must account for daily pressure and flow variations from consumers (off-design conditions). In this article, a combination of models was validated and applied to select the suitable pump for operating in an actual WDN. The replacement of two PRVs with PATs in a real network, previously divided into two DMAs and operating at constant speed was investigated. Economic and environmental analyses were also conducted. PAT1 was technically superior to PAT2, as PAT2 exhibited negative outlet pressure, affecting the pressure in DMA2. Optimal efficiencies are achieved at flow rates corresponding to the pump’s best efficiency point or near it, mimicking pressure control as if they were the valves themselves. The most efficient pump recovered 4,331 kWh/year, equivalent to a reduction of 1,732,400 gCO2/year, serving two households categorized as low-income. PATs proved to be a viable alternative, with a payback period of 2.1 years, as it can recover renewable energy. However, for effective pressure control in WDNs, other operational strategies, such as variable speed operation, should be explored.