Hydro Power Flashcards
State the equation for transmission efficiency
nth=energy delivered/energy available at source
Usually, what is efficiency at max power of a hydro-electric power plant?
Ntr = 2/3
How high can transmission efficiency reach?
Around 90%
What kind of valve does an impulse turbine use?
Spear valve
Give an example of an impulse turbine.
Pelton wheel, asymmetric turbine (Turgo).
Give an example of an reaction turbine.
Francis, Kaplan
Give example of a crossflow turbine.
Banchi or Ossberger
What are the differences between impulse and reaction turbines?
In an impulse turbine, only kinetic energy is used to rotate turbine. In reaction turbines, both kinetic and pressure energy is used to rotate turbine.
Give the formula for the velocity in water jet of an impulse turbine?
Vn=Cvsqrt(2[gH-((4fl/d))-(v^-2/s))])
Briefly describe how each of the different turbine types work:
Pelton wheel - jet is split symmetrically blades on the wheel.
Turgo - jet passes through the wheel from left to right.
Crossflow- cylindrical runner and water passes through ring twice.
Francis - fed by water from spiral casing.
Propeller - axial flow machine, normally fitted with valves.
Describe how hydraulic pumped storage works.
In generating mode, the plant works as a conventional hydro plant. Generator can function as motor and turbine as a pump. When demand for electricity is low, power is taken from grid to pump water into upper reservoir to act as an energy store for future use.
What are the environmental and social issues associated with hydro power?
- Flooding of useful land.
- Population displacement.
- Interference with fishing.
- Risk of catastrophe.
- Interference with water supplies.
- Local ecosystem damage during construction.
- Visual impact of dams and power stations.
- Visual impact of pipelines and transmission lines.
- Increased seismic activity.
