Components of Tidal Power Plants and Types

The followings are the components of a tidal power plants.

The dam to form the pool or basin.
Sluice ways from the basins to the sea.
The power house.

Dam – The function of dam is to form a barrier between the sea and the basin.

Sluice ways – These are used to fill the basin during the high tide or empty the basin during the low tide, as per operational requirement.

Power house – It consists of turbines, electric generators and other auxiliary equipments.

Types of Components Tidal Power Plants

Tidal power plants are classified into

Single basin arrangement
a) Single tide – cycle system
b) Double cycle system
c) Single ebb – cycle system
Double basin arrangement

Single basin arrangement

The single basin schemes have only one basin. Power generation is intermittent and mostly during off-peak load periods on daily load curves.

The tidal basin and the sea are separated by a dam or dyke. The rise and fall of tidal water levels provide the potential head.

Working

Fig shows a general arrangement of single basin tidal power plant (double cycle system) such plants generally use reversible water turbines so that power is generated on low tide as well high tide.

The turbine generator units are mounted within the ducts inside the dam or dyke.

General arrangement of tidal power plant

When there is incoming tide, sea level and tidal basin are equal, the turbine conduit is closed. When the sea level raises, the turbine valves are opened and the sea water flows into the basin through the turbine runner and generates power.

The turbine continues to generate power until the tide passes through its high point and beings to drop. The water head then quickly diminishes till it is not enough to supply the no-load losses.

To gain maximum water level into the basin, by pass valve quickly opens and the water comes into the basin. When sea and basin water level are again equal, the valves are closed as well as the turbine conduit.

The basin level then stays constant while the tide continues to go out. The turbine values are again opened after getting sufficient water head, the water now flows from basin to the sea thereby generating power.

Double basin arrangement

A single basin plant cannot generate power continuously, though it might do so by using a pumped storage plant, if the load supply fluctuates considerably.

A double basin scheme can provide power continuously or on demand which is a great advantage.

In the simplest double basin scheme, there must be a dam between each basin and the sea, and also a dam between the basins containing the power house.

Working

Fig shows a general arrangement of double basin tidal power plant. In this type, the two basins are located apart and their waters are never exchanged.

The turbine is set up between the two basins. One basin is intermittently filled by the flood tide and other is intermittently drained by the ebb tide.

Water flow from high basin to low basin is through turbines. This flow is controlled such that continuous power is obtained from the plant without waiting for tidal sequence.

Advantages and Disadvantages of Tidal Power Plants

Advantages:

It is free from pollution as it does not use any fuel.
Large area of valuable land is not required.
It does not produce any unhealthy waste like gases and ash.
It has a unique capacity to meet the peek power demand effectively when it works in combination with thermal or hydroelectric system.
It is much superior to hydropower plants as it is totally independent of rain which always fluctuates year to year.

Disadvantages:

Due to variation in tidal range, the output is not uniform.
There is a fear of machinery being corroded due to corrosive sea water.
It is difficult to carry out construction in sea.
As compared to other sources of energy, the tidal power plant is costly.
The power transmission cost is high because the tidal power plants are located away from load centers.