I just watched the June 9, 2023 DW Planet A video In-pipe energy: The hydro power nobody is talking about. It's a "happy story" video light on data and specifics. There's a demonstration for example of charging a cellphone from a backyard spigot at full throttle. (Don't do that at home!)
A fairly constant, reliable and significant pressurization of water mains is important for several reasons. It tries to ensure that if/when there are leaks, bad stuff underground (e.g. nasty microbes, pollutants, dirt) can never get into the water supply.
- In what situations could "dirty water leak into" municipal water pipes besides a catastrophic loss of pressure? (the answers are interesting!)
And of course there is viscous friction and sometimes significant height (potential energy) challenges (which are susceptible to air bubble-induced problems).
So pressure in the mains is a good thing!
And sometimes we depend on the kinetic energy of exiting water to do some work, like washing things.
This leaves me wondering about the following
Question: At which points in a pressurized municipal water distribution system are energy-recovering turbines generally placed as part of "in-pipe energy" generation?
And why is the inevitable pressure drop due to these turbines during flow1 not a problem?
1There is only a pressure drop when the water is actually flowing. The available power is delta-pressure times area (i.e. force) times velocity. The efficiency of the turbine and its distribution system determines what fraction of that power loss you can recover as electrical power.