There are different types of Hydroelectric power plant ( Hydropower plants). The Hydroelectric power plant can be classified based on head, capacity, hydraulic features, constructional feature, storage capacity, etc.
Classification of Hydroelectric power plant | Hydropower plants based on head
Different countries classify differently based on the head of water. The classification of hydropower project based on head is given by;
- Low head plant : <15 m
( Axially flow turbine is used. E.g. Kaplan turbine)
- Medium head plant : 15m to 70 m
( Mixed flow turbine is used. E.g. Francis turbine)
- High head plant : > 50 m
( High turbine is used. E.g. Pelton turbine)
Classification of Hydroelectric power plant based on capacity
Micro- hydropower : up to 100 KW
Mini hydropower project : 100 KW – 1000KW
Small hydropower project : 1 MW – 25 MW
Medium hydropower project : 25 MW – 100 MW
Large hydropower project : > 100 MW
Classification based on hydraulic features
These plants utilize the normally available hydraulic energy of the following water of the river.
Pumped storage plants:
Such plants utilize the concept of recycling the same water by using pumping selecting.
Tidal power plants:
Only a few plants like ‘La Rance’ in France have been in operation using the tidal energy of seawater.
Depression power plants:
This is a rare type of hydropower plants. Here power is generated by diverting an ample source of water such as seawater into a natural topographical depression that provides operating head for the plant.
Classification based on constructional feature:
Valley dam plants:
Valley dam plant is a dam in the river which creates a storage reservoir that develops the necessary head for the powerhouse. The powerhouse is located at the toe of the dam.
Water flows through penstocks embedded in the dam to the powerhouse and joints main river course directly at the outlet of the powerhouse.
Diversion canal plants:
The distinguishing feature of the diversion canal plants is that the waters of the river are diverted away from the main channel through a diversion canal referred to as a power canal.
After the water flows through the powerhouse, it is conveyed back to the parent river.
Diversion canal plants are generally low head to medium head plants. The powerhouse requirements of bondage are met through a pool called forebay’ located just before the powerhouse.
Head development may achieved in different ways;
- The head may be made available due to the fatter bed slopes of the power canal as compared with the river.
- In the case of natural fall, the water is diverted from upstream of fall and is let back into the river flowing through the powerhouse on the downstream.
- By diverting the water from a higher level river to another lower-level river through a diversion canal and a powerhouse. This is termed as ‘ inter-basin diversion of flow.’
- A weir may be provided at the location of ‘A’( in the degree) so as to create some additional head.
- Excessive sediment in the rivers is prohibited for this type of plant.
- High head diversion plant
The main distinguishing feature of such plant is the development of high head resulting from the diversion of water.
There are two ways in which this could be achieved.
The water of the river can be diverted through a system of channels and tunnels to another neighboring river or basing which is at a much lower level than the parent river.
The water from the river could be diverted along the tunnels from an upstream point of the river to a downstream point of the same river.
Classification of Hydroelectric power plant based on storage capacity:
Rum-of-river (ROR) plants
Those plants which do not regulate hydro-graph of the river by one or more seasons.
Utilize the minimum flow of a river having no appreciable poundage on its upstream.
In this type of plant, weir or barrage is constructed across a river, simply to rise and maintain the water level at a certain height.
Usually, a low head (up to 70 m) scheme and is suitable only on a perennial river with sufficient dry weather flow to generate designed power.
Limited storage is used to meet hourly or weekly function of flow.
Peaking run-of-river plants (PROR)
The increased load during peak hours, ROR plants may be constructed with bondage which can regulate daily or weekly hydrographs to run the plant under full capacity. This type of plant is known as the peak run of the river plant.
- Storage plant
- Those plants which regulate the hydrograph of the river by one or more seasons are termed as storage plants.
- A dam is constructed to create a storage reservoir that develops the necessary head for the powerhouse.
- Powerhouse is located at the foot of the dam or away from the dam.
- Carryover from monsoon to dry storage.
- Suitable for medium to high head project.
- Its powerhouse is at the toe of dam concentrated fall hydroelectric development.
- If powerhouse far from the dam divided fall development.
- Pump storage plant
- Plants having a water reservoir at upstream as well as downstream of a powerhouse, which collects water in the upstream reservoir by pumping water from the downstream reservoir using cheaper energy.
- Energy (which is used to pump the water from downstream to the upstream reservoir) is generated during peak hours.
- In such a scheme, the same water is utilized again and again. So no water is washed.
- In this system, the turbine also worked as a motor reversibly.