The process of delivering water from the treatment plant to the customer requires a significant amount of hydraulic energy. In the process of water delivery, excess pressure often needs to be reduced or is wasted. Pressure reducing valves (PRVS), atmospheric discharge, or excessive hydraulic head are commonplace. Reclaimed water and raw water delivery systems also experience similar hydraulic conditions. This hydraulic energy can be captured with the use of hydro turbines.
How it works
As with a PRV, a hydropower turbine reduces pressure. Instead of dissipating this excess energy like a PRV, however, the turbine converts it to usable power. A pump can be operated as a turbine, referred to as “pump as turbine” or PAT, but it is not as efficient as a classical hydro turbine such as the francis-type turbine (see picture). For free discharge, a pelton or turgo type turbine is recommended with the pelton turbine most effective at high head applications. To determine the best turbine for an application and the subsequent expected return on investment, a good understanding of flow and pressure characteristics and site conditions is required.
Where to use
In many Cities throughout the Phoenix area, there are numerous examples of electrical energy that can be garnered from wasted hydraulic energy: 1) PRVs, 2) Free discharge to reservoirs, 3) Recharge wells, 4) RO brine discharge, 5) low head-high flow raw water intake, and 6) CAP/SRP canal systems.
Valentine is currently performing a study for the City of Scottsdale to investigate the use of hydro turbines within their water system.
