Electricity production using renewable energy sources such as wind and water is the need of the hour due to the emerging issue of climate change and global warming. A machine that utilizes the energy of moving water and converts it into mechanical energy or electricity is known as a water turbine.
It was invented in the 19th century and used mainly for grain milling and water pumping purposes. Now it is majorly used for electricity generation by constructing dams. The efficiency of modern water turbines exceeds 90%.
Components of a Water Turbine
A water turbine consists of essential elements, namely the draft tube, runner, scroll case, stays, stay vanes, and wicket gates.
1. Draft Tube
The draft tube is a cone-shaped tube connected to the turbine runner. It is located at the bottom of the turbine and helps to direct the water flow away from the turbine.
The runner is a rotating component with blades. The runner is in constant motion due to water flow. As the runner spins, it becomes a generator that creates electricity. The runner needs a good design to work well.
3. Scroll Case
The scroll case is a concave enclosure that embraces the turbine runner and wicket gates. It guides the water flow onto the blades and prevents them from hitting the blades directly.
These are bars that connect the wicket gates to the runner. They keep the gates in place and evenly distribute their weight.
5. Stay Vanes
They are vertical bars attached to the stays. They help guide the water towards the center of the runner, ensuring smooth flow over the blades.
6. Wicket Gates
They are placed on the turbine runner to control the water flow onto the blades. They protect the blades from direct impact and damage. A governor controls the opening and closing of the wicket gates based on the generated electricity. When more electricity is needed, the gates open to allow more water flow, and vice versa.
Characteristics of Water Turbine
Different characteristics are needed to keep in mind while selecting a water turbine for specific application purposes which are mentioned as follows:
- Efficiency: Generally, it ranges from 85-90%. The ratio of the power output to the power input is termed efficiency.
- Capacity: The unit used for measurement is gallons per minute (gpm). It is determined by estimating the amount of water that can flow through it per second.
- Head: The head is the height of the water above the turbine, which ranges from as low as 10 or 1000 feet (about 304.8 m).
- Pressure: The flow of water through the turbine is the pressure of the water, which is measured in pounds per square inch (psi).
- Temperature: Temperature is an important parameter when selecting the appropriate water turbine as these are designed to function with temperature ranges up to 120 degrees Fahrenheit.
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Types of Water Turbine
There are two main types of water turbines: impulse and reaction.
1. Reaction Turbine
Reacting to the force of pressure and the flowing water, power is generated by reaction water turbines. As water moves past the turbine, its pressure, velocity, and direction are modified, effectively harnessing its energy. When water flows over the blades, it generates pressure that results in a powerful force pushing against the front and rear of the blades. This force causes the runner to rotate, creating torque and initiating rotation.
2. Impulse Turbine
The velocity of a water jet is modified by impulse turbines, which cause the jet to exert force on the curved blades of the turbine, thereby altering the direction of flow. The momentum impulse creates a strong push on the turbine blades. In an impulse turbine, the pressure of the fluid that flows over the rotor blades remains constant, resulting in all the work output being directly linked to alterations in the fluid’s kinetic energy.
Application of Water Turbine
As water turbine is a renewable energy means of electricity generation it finds various applications in multiple disciplines which are mentioned as follows:
- Used in Hydroelectric Power plants, as they help in generating electricity using the flow of water.
- In irrigation systems, water turbines can be used to pump water from lower to higher elevations. This is especially useful in steep areas where water supply is a challenge for farmers.
- Turbines in water treatment plants can be efficiently used for water pumping purposes.
Advantages and Disadvantages of Water Turbines
Water turbines serve both advantages and disadvantages that need consideration when turbine selection is done.
- It is relatively more efficient than the other ways of electricity production.
- It has various application industries.
- Maintenance and operation are easier.
- Produce zero emissions.
- Installation is expensive.
- It creates noise so it must be managed properly.
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