Francis Turbines : Parts, Working, Advantages and Disadvantages

Francis turbine is from the reaction turbine class of hydraulic turbine. It is name after its inventor James Francis. 

It was the first turbine with the radial flow, water enter the turbine radially and leave axially. 

High pressure water entering the turbine strike the blades of turbine and reaction of which blades of turbine rotates.

Its recommended to read our article on Kaplan Turbine and Pelton Wheel Turbine to know all about their parts, working and advantages and disadvantages

Francis Turbine Parts

Pen stock

It is a large size pipe which take water from the reservoir and take it to the turbine runner

Spiral / scroll casing

It is a close end passage with maximum cross section area at the inlet which decrease continuously along the direction of flow and finally zero at the outlet

Guide vanes / wicket gates

Main function of the guide vanes is to guide the water toward the runner at an angle appropriate for the design

Governing mechanism

Main function of the governing mechanism is to change the angle of attack at runner by guide vanes when flow rate of the water is changing

Runner and Runner blades

There are 16 to 24 runner blades attached to the runner. Runner blades the the direct action of water and rotate the runner. runner rotate due to both impulse and reaction forces

Bottom Ring

provide drainage space

Shaft Seal

Prevent water leakage between main shaft and head cover.

Draft Tube

It is gradually expanding tube which discharge water passing through the runner, to the tail race

Working of Francis turbine

As water enter the turbine through the inlet nozzle its velocity will decrease as it moves forward in the turbine but the continuous decrease in the area of spiral casing will not let it happen. Design of spiral casing makes shore that the water strike the each blade of the turbine as a constant speed.

Francis Turbine Working

Blades are mounted on the runner. Design of the blade is like a thin air foil so when water flow over it low pressure is created at one point and high pressure is created on other side

and motion take place from high pressure to low pressure. Lower side of the blade is like a bucket which use the impulse forces of water in the rotation.

Francis Turbine Blades

If water flow rate change then governing mechanism came into use and change the angle of attack of water on to the blade so the turbine can work properly. After the water passes the blades it enter the draft tube whose continuous increase in area decrease the velocity of the water.

Francis Turbine Draft Tube

To learn the difference between different turbine type read our article Difference Between Inward Flow and Outward Flow Reaction Hydro Turbine

Advantages of Francis turbine

• Easy control on changing head

• Size of runner and generator is small

• Small change in efficiency over time

• The operating head can be utilized even when the variation in the tail water level is relatively large when compared to total head

Disadvantages of Francis turbine

• Unclean water can create wear 

• Inspection method is very difficult

• Cavitation is an ever present danger

• Water hammer effect can create some problems

• Head 50% lower can have harmful effect on the efficiency as well as cavitation danger became more serious

Pelton wheel turbine : Parts, Working, Advantages and Disadvantages

Pelton wheel turbine is from the impulse turbine categories of hydraulic turbine. Pelton turbine was named after its inventor Allan Pelton. There are many other types of impulse turbine but Pelton  turbine is the most efficient from all of them. 

Its recommended to read our article on Francis Turbine and Kaplan Turbine to know all about their parts, working and advantages and disadvantages. 

Parts of Pelton Wheel Turbine

Pen stock

Pen stock is a solid pipe which take water from the dam( structure which store water on its one side) and take it to the turbine at very high speed.

Spear

A spear is provided with in the pen stock and its main function is to increase and decrease the speed of water entering into the turbine. If more water is needed spear move back and allow more to enter into the turbine and if less water is needed spear moves forward to spot excess water from entering in to the turbine.

Nozzle

Nozzle is provided at end of pen stock and its main function is to increase the velocity of the water and to direct it to the buckets of the turbine.

Buckets

Each Pelton wheel turbine has a specific number of buckets attached to its runner. Buckets take the impact of water and start to rotate along the runner

Runner

Runner is a heavy circular disc on which buckets are attached. Runner is further attached to the shaft. 

Brake nozzle

When turbine is need to be stopped then water is thrown at the back of the buckets from another nozzle called brake nozzle

Casing

The whole setup of the turbine is enclosed in a structure called the casing of the turbine

Pelton Wheel Turbine Diagram

To learn the difference between different turbine type read our article Frances Turbine vs Kaplan Turbine

Working of the Pelton wheel turbine

Dam store water at its one side when water level is increased at a specific height then the gates of the dam is open and water start to flow through the pen stock. 

Nozzle at the end of the pen stock convert this high speed water into a water jet which on striking the bucket convert its kinetic energy into the rotation energy of the buckets and the runner. 

Runner is attached to the shaft which is further attached to a generator. Rotating runner rotates the shaft which rotates the generator. 

Different efficiency

Hydraulic efficiency 

It is the ratio of the power developed by runner to the power supplied at in let of turbine

Mechanical efficiency

It is the ratio of the power available at turbine shaft to the power available at turbine runner

Volumetric efficiency 

It is the ratio of volume of water actually striking the runner to the total water supplied by the jet to the turbine

Overall efficiency

It is the ratio of the power available at the turbine shaft to the power available from the jet

Advantages of Pelton wheel turbine

• Most efficient of all turbines

• High overall efficiency

• Easy assembly 

• Operate at low discharge

• Flat efficiency curve

• Can be operation in silted water

Disadvantages of Pelton wheel turbine

• Decrease in efficiency with time

• Components have large size

• Variation in the operating head is very difficult to control

• The operating head cannot be utilized even when the variation in the tail water level is relatively large when compared to total head

Tidal Lagoon

Tidal lagoon is type of tidal power production which is much similar to the tidal barrage, the difference is that tidal lagoon uses a hollow cylindrical structure to create the difference in water water level on opposite sides of wall instead o the the long barrage. 

Tidal lagoon structure is just like a huge hollow cylinder with one or more holes from which water enter and leave the cylinder. These holes have a turbine installed at the half thickness of the cylinder and have capability to produce electricity by rotating in both direction. 

Working of tidal lagoon

Tidal lagoon is install in places in which a water level increase and decrease frequently. When water level increase it start to gather around the walls of the cylinder and as the water level increase potential difference increase on opposite sides of the wall. As water have only few places to enter in the lagoon so it exert all the force at that point.When water start to enter in the lagoon, kinetic energy of the water in transfer into the rotation motion of the blades of the turbine and so the turbine produce the electricity. When water level decrease, water present in the lagoon start to leave the lagoon the same points from which it enter and so turbine rotating in opposite direction and produce the electricity.

Advantages of tidal lagoon

• Less construction cost than other types of tidal power
• Less area required for operating than other
• Less danger to marine life as in not stop the motion of water like tidal barrage

Disadvantages of tidal lagoon 

• Highly skill labour is required for the construction
• High maintenance cost
• Energy production is less as it store small quantity of water

Difference between Onshore and Offshore wind turbine

Wind speed

On shore wind turbine are design for the moderate wind turbine and offshore wind turbine are design for higher wind speed

Limitation of the area

Because of the fact the wind turbine can cause damages to human life that’s why there is limitation of are in onshore case but no limitation of are in offshore as there is no human life near by

Visual impact

Because of their interact with human onshore wind turbine have a bad visual impact but offshore wind turbine have zero visual impact because they are installed far away in the ocean

Acoustic noise

Both types produce the noise but noise of onshore wind turbine cause problem for the nearby human but noise of offshore wind turbine causes no problem to humans

Erosion 

Because of the moisture available in the area of the installation onshore wind turbines have very low erosion in them but offshore wind turbine has very high erosion effect on them

Capital cost

Because of the ease in installation, transportation and other facts capital cost of onshore wind turbine have lower that of offshore wind turbine

Maintenance cost

Because of easy transportation, low erosion and moderate wind speed maintenance cost of onshore wind turbine is low as compared to the offshore wind turbine

Energy production

Energy production of both types is satisfactory but due to easy grid connection onshore wind turbines have good energy production but due to highly available wind energy production of offshore wind turbine is better

Access

Wind turbines have huge parts, transporting them and assembling them is a great task. On shore wind turbine have convenient accessibility whereas it is difficult to access offshore wind turbine

Dynamic Tidal Power

It is a fact that sea water continuous to flow in two direction one is perpendicular to the shore and one is parallel to the shore. Dynamic tidal power uses the parallel flow to sea water to produce the electricity.  It is most complicate and least sturdy type of tidal power production and it is still in theoretical form no practical work has been done yet. Dynamic tidal power plant is a 30 KM long ‘’T’’ like barrage perpendicular to the shore.

The red section shows the high water tide and blue section the low water tide.

Working of dynamic tidal power

It work just like the tidal barrage the only difference is that the tidal barrage work works with flow perpendicular to the shore and dynamic tidal power works with parallel flow. When the water tide shift the direction after every 12 hour then water start to build up on one side of the wall. When water reached specific height, gates of the barrage is open and water start to flow through the tunnels and make the turbine rotate and the whole process result in the production of clean electricity.

Advantages of dynamic tidal power

• A single unit can produce from 8 to 15 GW power
• Because of its T shape it can produce electricity in any direction of water flow
• It is most reliable that other renewable sources
• It is more efficient than other tidal power types
• It is safer for marine life than tidal barrage
• As head required is lower than the head required for the tidal barrage so it can be installed at low head places where tidal barrage can be installed

Disadvantages of dynamic tidal power

• Its biggest disadvantage is that it is still not tested
• Building a 30 km long barrage need high initial cost
• Although they are less harmful than other tidal but still 30km long barrage can create many problems for marine life

Tidal Stream Generator

Tidal steam generator is a type of tidal power plant which uses the kinetic energy of the running stream of water to produce the electricity. They are just like wind turbine in their structure and working, the only difference is the place of their working. Tidal stream generator are much more efficient than the wind turbine because of the fact that water is 800 times more than the wind.

Types of turbine in tidal stream generator

Horizontal axis tidal stream turbine

In this type of tidal stream turbine rotation axis of blades is parallel to the direction of water stream flow. Because all three blades rotate at a time so there rapid rotation and low torque make then ahead all other types of turbine.

Vertical axis tidal stream turbine

Axis of rotation in this type is perpendicular to the direction of flow of water stream. Their biggest advantages is that they can produce electricity in any direction of stream flow but their disadvantages is that their one blades always appose the rotation of the turbine.

  

Reciprocating devices (oscillating hydrofoils) 

In this type blades instead of rotating, oscillate up and down due to the lift created when water flow over and beneath the blade of the turbine

Venturi effect tidal devices

Duct section concentrate the flow from a larger area to a smaller area due to which velocity increase and thus smaller turbine as compared to normal horizontal axis turbine can be used to produce the electricity

Parts of tidal stream generator

Parts of tidal stream generator is much like wind turbine but all parts are packed in a water proof nacelle 

• Hub
• Blades
• Shaft
• Gears
• Nacelle
• Tower
• Base

Working of tidal stream generator

Working of Tidal stream generator is just like the wind turbine. Fasting moving water particle have kinetic energy which is converted in the rotation motion of the blades. Blades transfer their rotation to the shaft. Gear box increase the rotation motion before it is transfer to the generator to produce the electricity

Advantages of tidal stream generator

• No visual effects
• Much safer than wind turbine and efficient as well
• They can be installed in already build structures present in the stream path.
• As there is no need of building the barrage so they are much cost effective than other types of tidal power production methods.

Disadvantages of tidal stream generator

• They are less efficient as compared to other types of tidal wave production methods.
• Their effect on marine life is still unknown

Multistage Centrifugal Pump

A simple centrifugal pump use a single impeller mounted on a shaft to produce a specific head and a specific discharge rate but what if you need n times greater head or discharge rate. This problem can be solved by using the multistage centrifugal pump

There are two possible reason why you use multistage centrifugal pump

1. Need high head at constant discharge rate
2. Need more discharge rate at constant head

Mounting more than one impeller on a same shaft and closing them in same casing will produce higher head than single impeller pump but the discharge rate will be same as single impeller

If you install two pump parallel to each other at same sump then the discharge rate will be increase but head will be same as that of single pump

Pump is series

In series arrangement of pumps, more that one impellers are mounted on the single shaft of a centrifugal pump and closed under a same casing. This arrangement can increase the head of the pump by keeping the discharge rate constant.This type is used to deliver small quantity of liquid at high head

In this type of arrangement impeller one take is input from the sump and discharge is at a specific head and discharge rate. This out put if impeller one is the input for the impeller number two. Out put of impeller number two will be same discharge and twice the head.

H total = n H
n = number of impeller
H = head made by single impeller

Advantages

• Less frictional losses
• Reduce stresses
• Less slip leakage
• Thrust can be eliminated
• High suction lift at relatively low impeller speed

Pump in parallel

For a single centrifugal pump it is impossible to deliver a huge quantity of liquid at small head but it is possible with parallel arrangement of pump. More that one pumps are install at a single source and both of them work separately to produce a specific discharge rate then their out put is merged in a single delivery pie to get a  greater discharge rate than single pump.

Q total = n Q
n = number of pump installed
Q = Discharge of single pump

Tidal Barrage Power Generation

Tidal power harness by the tidal power plant is the power inherent in tides at sea or oceans that is the power of motion of water actuated by tides. Tides are defined as the increase and decrease in water levels due to the motion of water from one place to the other.

It is a fact that water level increase and decrease during the high and low tide of sea. Tidal barrage power generation system uses this method to produce the electricity.

Components Of Tidal Power Plant

The components of  tidal power plant are as follow

A barrage

A barrage is a small wall built at the entrance of a gulf in order to trap water behind it. It is just like the dam structure. It will gather water by stopping it from going into the gulf when water levels at the sea are high or it will stop water from going into the sea when water level at the sea is low.

Turbines

Turbines are the components which convert the kinetic energy of water in to the rotational energy of the generator which convert rotational energy into electrical energy. They are located in the passageways that the water flows through when gates of barrage are opened

Sluices

Sluice gates are the ones responsible for the flow of water through the barrage

Embankments

They are caissons made out of concrete to prevent water from flowing at certain parts of the dam and to help maintenance work and electrical wiring to be connected or used to move equipment or cars over it

Working Tidal Power Plant

We have divided the working phenomena of tidal barrage generation into seven components

Tidal motion

As said above water level increase and decrease during the high and low tide of sea and this is the most important in this power generation system because it all depends upon the increasing and decreasing level of water

Barrage

Barrage is the wall structure just like the dam structure. Its function is to stop the water on one side during high tide and release it when it reach its maximum value and store it on other side and release it during low tide

Potential energy

I tidal barrage power generation system main source of energy is potential energy of water stored at some high due to the barrage. This energy will be converted to kinetic and then to electrical energy

Opening of barrage doors

Barrage store water during the high tide and when it reached its maximum value doors of barrage are open to let the water flow to the other side

Kinetic energy

As water when stored at some height has some potential energy and when doors are of water atsrt to flow to other side and potential energy is converted in to kinetic energy  which will be used to produce the electrical energy

Using turbines

Up to now potential energy of water is converted into kinetic energy and now this kinetic energy will be converted into the rotational energy of turbine blades when they strike them. Blades attached to a shaft and the shaft is attached to the generator

Electrical energy

Water rotate blades which rotates the shaft and shaft rotates the generator which will produce the electrical energy and one cycle is completed. This process will be continuous till there is difference in the water level

Advantages Of Tidal Power Generation

• There are many advantages of generating power from the tide; some of them are listed below:

• Tidal power is a sustainable energy resource.

• It reduces fossil fuels dependence.

• It has very less visual impact.

• Construction of large-scale offshore devices results in new areas of sheltered water, attractive for fish, sea birds, seals and seaweed.

• Tidal energy is available worldwide on a large scale from deep ocean waters.

• Tidally driven coastal currents provide an energy density four times greater than air

• A feature which gives them an advantage over both wind and solar systems is that the tidal currents are both predictable and reliable 

• Seawater is 832 times as dense as air; therefore the kinetic energy available is much greater than air

Disadvantages Of Tidal Power Generation

• Unfortunately, there are also disadvantages and limitations to generating tidal power. Some of these are:

• At the present time there is a problem that the method is not economical.

• Tidal power systems do not generate electricity at a steady rate and thus not necessarily at times of peak demand

• Tidal fences could present some difficulty to migrating fish.

Last Words for Tidal Power Plant

So, Our loyal Engineers that was all about Tidal Barrage Power Generation. we are sure you have enjoyed reading it and understood each and everything. 

If you still have any questions please comment below or if you have some better information that we have missed please share with me via the comment box below. 

we will appreciate your efforts. Take A Lot Of Care!

Four Methods Of Tidal Power Energy Generation

There are few facts that every should know about our planet earth

• 70% of our planet is occupied by water and 30 % by dry land
• Water never stops its motion
• We are facing the energy crises 
• Use of excess amount of fossil fuel cause the global warming

Problems we are facing can be solved if we see the fact 1 and 2 that is a huge amount of water that never stops.

As we all know that every moving thing have kinetic energy and if we look at the amount of water we have means we have a huge amount of kinetic available every time. 

If these resources are used they can easily solve our problems of energy crises and global warming. Technology which could convert this kinetic energy into electrical energy is called Tidal power

Four methods of Tidal Power Energy Production

• Tidal steam generators

• Tidal Barrage 

• Dynamic Tidal Power

• Tidal Lagoon 

Tidal Stream Generator for Tidal Power  Energy

Tidal stream generator method is use to extract energy from running tides of water. Many of you may have a visit of a river where you see flowing water at high speed which means that water have huge amount of kinetic energy store in it and we can use that energy to produce electrical energy by tidal stream method

If you have ever seen a wind turbine know how it works them there is no need of learning the working of tidal stream generator method because it works on the same principle. 

But for those did not let us explain high speed moving water when strike the blades of turbine its kinetic energy is converted into the rotational kinetic energy of the turbine blades. Blades cause the generator to rotate which produce the electricity energy

Tidal Barrage for Tidal Power Energy

Look of Tidal Barrage Power Generation is just like a traditional dam and it work on the same principle as the traditional dam do but there is one difference between them traditional dams store water on one side and then convert the potential energy to kinetic energy and use that kinetic energy to rotate the blades to turbine to produce electrical energy and tidal barrage use this method on both sides of the barrage.

Consider a place where water level increase and decrease with the increase and decrease of tides. 

If you constructs a wall from one end to another then when water start to increase it will be stored in one place when it reach its maximum value, gates are open and water starts to flow over the turbine blades and so electrical energy is produce. 

When water level on both sides is same then gates are closed and when water level lowers on one side’s gates are open again and so electrical energy is produce again. This is how this method works 

Dynamic tidal power for Tidal Power Energy

It is a fact that ocean tides don’t operate strictly perpendicular to the shore, but also flow in parallel to the shore as well and Dynamic tidal power use this method to generate electricity. 

It is the most complicated, least well understood tidal power scheme yet conceived. 

This method involve the creating of a long dam-like structure perpendicular to the coast, with the option for a coast-parallel barrier at the far end, forming a large 'T' shape to harvest energy from the tides as they flow parallel to the shore as the diagrams below illustrate. 

Red represents relative high water and blue represents relative low water

Tidal Lagoon for Tidal Power Energy

A newer tidal energy design option is to construct circular retaining walls embedded with turbines that can capture the potential energy of tides. The tidal lagoon scheme is very similar to the tidal barrage method of using tides to generate power. 

In fact, the only real difference between the two is that the tidal lagoon does not block off an entire estuary, but rather makes use of only part of it. 

During the high tide water level around the lagoon will increase and try to move in the lagoon and during low tide water will move outside in both direction it will produce electricity

GeoThermal Power Plant

According the theories core of our earth is in molten form and volcanic action taking place at different location on the surface of the earth are prove to these theories. There is water and other resources above the core and because of core high temperature water start to boil and get into vapor shape as it has no way to go so it start to gather in place and create huge pressure and this pressure when taken up to the ground, is used by the turbine to move the generator and produce the electricity. Geothermal energy is considered renewable because the heat is continually replaced. The water that is removed is put right back into the ground after its heat is used.

Types Of Geothermal Power Plants

All geothermal power plants use steam to turn large turbines, which run electrical generators.  There are three basic types of geothermal power plants and they are as follow

Direct Dry Steam

Direct dry steam is the oldest type of geothermal power plant. In this type of plant hot steam is piped directly from geothermal reservoirs to steam turbine which drives the generator that produces electricity. This plant emits only the steam and very small amount of gases.

Flash and Double Flash Cycle

Flash and Double Flash Cycle got its name from the way of its working. Flash and Double Flash Cycle use water that's between 300 and 700 degrees Fahrenheit (148 and 371 degrees Celsius) to make electricity. Water is sprayed into a tank which is held at a much lower pressure than the water, causing some of the fluid to rapidly vaporize which is also called flash. The vapor then moves to a turbine, which drives a generator to produce electricity. If there is any liquid left in the tank, it can be flashed again in a second tank called the double flash to extract even more energy.

Binary Cycle

Binary Cycle power plant is for those geothermal places which have moderate temperature (below 400 F). Binary Cycle use the concept of heat exchangers, water at moderate temperature transfers its heat to a low boiling liquid and vaporized it, which then move forward to drives the turbine. There is a close loop of this system due to which nothing is eliminated in the atmosphere. Moderate-temperature water is by far the more common geothermal resource, and most geothermal power plants in the future will be binary-cycle plants.

Components and Working

Geothermal Vent

As the geothermal energy resources are deep under the earth and to reach them you need a path that’s why the first component of a geothermal plant is the geothermal vent. Geothermal vent is a deep well drilled into the Earth to extract the steam energy. A geothermal plant may have two goals for its vent; most of the power plant draws superheated and pressurized water upward, they are called flash steam plants and others use simply dig far enough underground to reach a point where the Earth is warm enough to boil water, they are called dry steam vents.

Steam Tank

The pressure of the Earth kept the water in liquid form despite its high temperature but when this water is taken out by geothermal power plant into a tank it suddenly changes to steam that’s way name of flash steam is given to it and tank in which it is placed is called steam tank

Separator

The steam is then passed through the separator where most of the dirt and sand carried by steam are removed.

Turbine

A large steam turbine is used by all types of plants. High pressure steam causes the turbine to rotate. This turbine is attached to an electric generator, and as the turbine start to rotate the generator turns the mechanical energy into electric energy.

Condenser

After the steam passes through the turbine it is still very hot and this energy can be used can be used for other purpose. That’s why there is a condenser after the turbine which collects it and condenses it. Steam in condenser can be used for heating or greenhouse farming.

Advantages Of Geothermal Energy

• It is clean and safe for the surrounding environment.
• It is renewable because hot water can be used
• It is extremely cost effective in suitable areas
• It use has very low emissions of greenhouse gases to about three percent of the carbon dioxide emissions of a fossil power station
• It doesn't depend on the sun, wind and huge water resources  like other renewable energy resources

Last Words!

So our loyal reader that's was all about to day post hope you have enjoyed reading it. If you have any questions or we have missed any point or have make any mistake, you can mark them in the comment box below