Advantages of hydropower
- renewable
- meets peak demands
- Energy storage (pumped storage plants)
- hydrapower does not produce green house gasses and leaves no waste
- high efficiency
Drawbacks of hydropower
- the cost of the dam. Many developing countries countries cannot afford it
- negative environmental impact. Fish migration, birds affected by shifting wetlands(våtmarker), damage in riverbeds
- limited plant locations
- susceptible to droughts
Storage hydro (conventional)
- large units
- peak energy generation
- mindre vanligt än ”pumped storage”
- naturlig reservoar och begränsad reglerbarhet
Run-of-river systems (RoR)
- small units
- base energy generation
Pumped storage
- reversible units(pump & turbine operation)
- storage of energy
- effective way to consume and produce energy
Run-of-river power plants
The head is very low(10-15m) so normally it does not exist a penstock(or it is very short). A dam is constructed, a short penstock (or directly from the upper reservoir) water pass through a special spiral case to put the water inside the turbine, the turbine is few meters submerged.
What is a surge tank?
It is a device used to mitigate water hammer and located approximately at the same level as the upper reservoir.
What is the turbine setting?
The height of the turbine from the lower reservoir level
During cavitation phenomena, the violent process of cavity takes place when?
The pressure of the fluid is higher than the vapor pressure
Vad finns för delar i en Francis turbine?
Distributor - leads water to runner and regulates discharge
Spiral casing - leads water from penstock to distributor. The spiral casing completely surrounds the runner. It’s area of crossection decreases gradually around the circumference which leads to uniform distribution of water along the circumference of the distributor.
Runner - converts hydraulic energy to mechanical energy
General facts about the Francis turbine
- the most powerful turbine
- the best when you want to regulate the power since the efficiency changes during the operation
- the biggest risk of cavitation
- main types of cavitation is blade cavitation & draft tube cavitation
- best choice for a turbine with 100-400 m head
General facts about Francis turbine
- most powerful turbine
- the best when you want to regulate the power since the efficiency changes during the operation
- biggest risk for cavitation
- best choice when head is 100-400 m
General info of Kaplan
- best for head between 5-70 meters
- 4 MW- 200 MW
- moving runner blades
- the position of the runner blades chance to adapt the discharge
Bulb turbine
- for applications with very low head!
- head 2-20 meter
- 1 MW- 40 MW
- similar to Kaplan but in horizontal disposition
Pelton turbine
- impulse turbine
- no pressure changes through turbine
- head 250-1400 m
- 10 MW- 200 MW
Which parts does a pelton turbine consist of?
- injector: can be multiple, the flow rate is n times bigger with n injectors
- jet breaks: to stop a pelton turbine Two actions are required. 1 deflector has to be located in front jet & the jet is deviated
2 stop runner - a jet of water is injected in the buckets in the reverse face - break nozzle
- penstock
- spear
- deflector
- nozzle
- runner
- buckets
Pump-turbine: what is ternary unit and when it is used?
Its used when the head is very high, over 700 m
Composed by: a pelton turbine, a multistage pump(because of the high head)
Turbine - motor-generator - hydraulic torque converter with gear coupling - pump
Pump-turbine: binary units(reversible single stage unit)
Rotor spinning in both directions
Runner: pump & turbine
Generator: motor & alternator
Wells turbine used in marine power plants
The fluid crossing the turbine is air
