REVERSE TURBINE OR PUMP AS TURBINE

Reverse Turbine

Hi readers, are you thinking that what is reverse turbine?. Till now we've seen Francis turbine, Kaplan turbine, Steam turbine and Pelton wheel. But reverse turbine? It's also among all these turbines, and exactly to say, it's a Francis turbine. Let me explain how it's a Francis turbine.

To understand what is reverse turbine, first we've to know about how does a hydroelectric power plant works? 

How does a hydroelectric power plant works?

A hydroelectric power plant generates electricity by using potential energy of water. Water falls from certain elevation from turbine, technically we can call it as a head. The potential energy of water is converted into kinetic energy and pressure will vary according to diameter of casing when water entered into the casing of turbine, in case of Francis turbine. Then water with high kinetic energy shows impact on blades of turbine. Then turbine started to rotate, which is coupled to generator or alternator. When turbine started to rotate, generator also rotate along with turbine. Then alternator will generate electricity by the virtue of Faraday's law of motor/generator. After that water leaves the casing of turbine and flow in its way. But in case of Kaplan turbine and Pelton wheel there is a small variation. 

Reverse turbine, its not a type of a turbine. It's a mode of operation of turbine. It's actually a Francis turbine. So guys to understand reverse turbine we need to know what exactly is a Francis turbine.

Fig. 1. Francis Turbine

Guys above image shows the how a typical Francis turbine works. Francis turbine is a type of reaction turbine. The blade structure of it make it react to the water strikes.

Fig. 2. Structure of blade

Guys I hope you understand the how does a Francis turbine works.  Now coming to reverse turbine.

Reverse turbine is as an act of Reverse pumping

Reverse turbine is a reverse operation of turbine. Why we need to rotate turbine in reverse direction. The water which is flow after turbine rotation, is going to waste in view of power generation. So in order to bring back this water we need to rotate turbine in reverse direction. The Francis turbine in reverse direction act as a centrifugal pump.  Centrifugal  pump is used to transport the water. So here turbine transport waste water again into water reservoir to upcoming needs.

Advantages of Reverse pumping / Reverse turbine

1. We can save the water

2. We can generate the more electricity

And you may rise doubt, that to pump water in reverse direction, how much energy is needed?. Yes we have to do always energy balance. The energy produced by alternator is always greater than energy required to rotate the turbine in reverse direction. So in Peak hours we can generate more energy when compare with other plants. And if there is less demand we can pump the water reverse to the reservoir.

Nagarjuna Sagar:The first reverse pumping hydroelectric powerplant in India

Nagarjuna Sagar is a masonry water dam built across the Krishna River in the border of Andhra Pradesh and Telangana states. Operated by both states.

It has hydroelectric power plant capacity of 816MW.

Comprising of 8 units 

  1 * 110 MW Francis turbine,

  7 * 100.8 MW Reversible Francis Turbines.