Pressure and flow recovery
Turning surplus gas or water pressure into power.
Recovery and reuse · Pressure, motion and waste fuels · No. 131
- Recovery and reuse
- Waste energy: Pressure
A ceramic rotor in desalination plants hands brine pressure back to incoming seawater at up to 98% efficiency.
Chart: Illustration: Pressure and flow recovery
Where it comes from
Chart: Map of where it comes from
Wherever pressure is thrown away across a valve, a turbine or exchanger can catch it: city gas stations dropping 70 to 20 bar, water mains, and brine leaving reverse osmosis membranes.
Three things to know
- Gas cools about 0.5 C per bar as it expands, so one modelled 2 MW expander needed 1,980 kW of extra preheat.
- Compressors turn 80-93% of their input into heat; a 100 bhp unit's recovered heat saved about USD 6,975 a year.
- Small in-pipe hydro is slow to pay: Manitou Springs in Colorado expected 12 to 14 years.
The journey
- 1 Surplus pressureGas mains, water pipes or RO brine
- 2 Bypass loopTurbine sits beside the old valve
- 3 Expander or exchangerPressure becomes shaft work or transfers directly
- 4 PreheatGas must be warmed as it expands
- 5 OutputElectricity, or cheaper fresh water