Hydroelectric Power Plant : Layout, Working and Types

Generation of electricity by hydropower (potential energy in stored water) is one of the cleanest methods of producing electric power. In 2012, hydroelectric power plants contributed about 16% of total electricity generation of the world. Hydroelectricity is the most widely used form of renewable energy. It is a flexible source of electricity and also the cost of electricity generation is relatively low. This article talks about the layout, basic components and working of a hydroelectric power station.

Layout and working of hydroelectric power plant

Layout of hydroelectric power plant

The above image shows the typical layout of a hydroelectric power plant and its basic components.

Dam and Reservoir: The dam is constructed on a large river in hilly areas to ensure sufficient water storage at height. The dam forms a large reservoir behind it. The height of water level (called as water head) in the reservoir determines how much of potential energy is stored in it.

Control Gate: Water from the reservoir is allowed to flow through the penstock to the turbine. The amount of water which is to be released in the penstock can be controlled by a control gate. When the control gate is fully opened, maximum amount of water is released through the penstock.

Penstock: A penstock is a huge steel pipe which carries water from the reservoir to the turbine. Potential energy of the water is converted into kinetic energy as it flows down through the penstock due to gravity.

Water Turbine: Water from the penstock is taken into the water turbine. The turbine is mechanically coupled to an electric generator. Kinetic energy of the water drives the turbine and consequently the generator gets driven. There are two main types of water turbine; (i) Impulse turbine and (ii) Reaction turbine. Impulse turbines are used for large heads and reaction turbines are used for low and medium heads.

Generator: A generator is mounted in the power house and it is mechanically coupled to the turbine shaft. When the turbine blades are rotated, it drives the generator and electricity is generated which is then stepped up with the help of a transformer for the transmission purpose.

Surge Tank:

Surge tanks are usually provided in high or medium head power plants when considerably long penstock is required. A surge tank is a small reservoir or tank which is open at the top. It is fitted between the reservoir and the power house. The water level in the surge tank rises or falls to reduce the pressure swings in the penstock. When there is sudden reduction in load on the turbine, the governor closes the gates of the turbine to reduce the water flow. This causes pressure to increase abnormally in the penstock. This is prevented by using a surge tank, in which the water level rises to reduce the pressure. On the other hand, the surge tank provides excess water needed when the gates are suddenly opened to meet the increased load demand.
surge tank in hydro power plant

Types of Hydro-power plants

Conventional plants:

Conventional plants use potential energy from dammed water. The energy extracted depends on the volume and head of the water. The difference between height of water level in the reservoir and the water outflow level is called as water head.

Pumped storage plant:

In pumped storage plant, a second reservoir is constructed near the water outflow from the turbine. When the demand of electricity is low, the water from lower reservoir is pumped into the upper (main) reservoir. This is to ensure sufficient amount of water available in the main reservoir to fulfil the peak loads.

Run-of-river plant:

In this type of facility, no dam is constructed and, hence, reservoir is absent. A portion of river is diverted through a penstock or canal to the turbine. Thus, only the water flowing from the river is available for the generation. And due to absence of reservoir, any oversupply of water is passed unused.

Advantages of a hydroelectric power plant

  • No fuel is required as potential energy is stored water is used for electricity generation
  • Neat and clean source of energy
  • Very small running charges - as water is available free of cost
  • Comparatively less maintenance is required and has longer life
  • Serves other purposes too, such as irrigation


  • Very high capital cost due to construction of dam
  • High cost of transmission – as hydro plants are located in hilly areas which are quite away from the consumers


Why Electrical Engineering Jobs Rock?

Being an electrical engineer is no easy feat. These days, this particular field of engineering encompasses a broad range of scientific disciplines that include, but are not limited to, electronics, control systems, signal processing, power engineering, microelectronics, and telecommunications, which is one of the most vital tools of the 21st century.
Indeed, the explosion of the number of electrical engineering jobs and the subfields that specify them is proof of the world’s continued technological advancement. But what exactly do these engineers do? At the mention of “electrical”, or any word related to it, some of us immediately jump to mental images of wires and power outlets. There’s more to it than that, however. Apparently, being an electrical engineer can put you around expensive toys of science that almost none of us regular people would know how to turn on, let alone operate. Listed below are some of the reasons why electrical engineers are the equivalent of rock stars in the scientific field.
  • No industrialized city exists nowadays without a power grid, an electrical network of generators connected together to manufacture the energy needed by their users. Power engineers, as they are called, work on its intricate design and maintenance. If the knowledge needed to make something like that work does not give you bragging rights, then the job title alone should. In the future, satellite controlled power systems will be created, giving us the ability to do something about power surges or blackouts before they cause any further inconvenience.
  • Those scientists you see on television shows and movies that create these absolutely small machines called nanobots may look a tad too ridiculous to be real. Some of us might think that no technology today would be able to create a robot the way we understand those machines to be–able to perform a specific function upon command and operated by an energy source. And because we are all not scientists, some of us do not know that this already exists, albeit still in the developing process. The RoboBee or RoboFly took 12 years to make. Electrical engineers are all too familiar with microelectronics, the same field that gave birth to this invention. We can only imagine robot soldiers the size of a pinhead battling cancer cells in the future.
  • What do household security systems and a personal jet plane have in common? If you answered they’re probably owned by people who have too much money, then you wouldn’t be wrong. There’s one thing more, however–they both have a mechanism designed by instrumentation engineers. The mercury switch that enables the furnace to maintain a specific temperature and all the bells and whistles that keep aircrafts from getting lost and maintaining altitude are part of instrumentation engineering. This subfield is where sensors are developed for larger electrical systems, meaning that a Boeing 747 won’t probably last an hour in the skies without the proper sensors, if it takes off at all, of course. If you were one of those children who had been obsessed with making sure their paper planes remained aloft, you might want to look into this.
Electrical engineering is not for everyone, true, just like the rest of the other occupations it require years of studying and expertise.


Basic Layout and Working of a Nuclear Power Plant

In a nuclear power plant, heat energy is generated by a nuclear reaction called as nuclear fission. Nuclear fission of heavy elements such as Uranium or Thorium is carried out in a special apparatus called as a nuclear reactor. A large amount of heat energy is generated due to nuclear fission. Rest parts of a nuclear power plant are very similar to conventional thermal power plants. It is found that fission of only 1 Kg of Uranium produces as much heat energy as that can be produced by 4,500 tons of high grade coal. This considerably reduces the transportation cost of fuel, which is a major advantage of nuclear power plants. Also, there are large deposits of nuclear fuels available all over the world and, hence, nuclear power plants can ensure continued supply of electrical energy for thousands of years. About 10% of the total electricity of the world is generated in nuclear power plants.

How does a nuclear power plant work?

Heavy elements such as Uranium (U235) or Thorium (Th232) are subjected to nuclear fission reaction in a nuclear reactor. Due to fission, a large amount of heat energy is produced which is transferred to the reactor coolant. The coolant may be water, gas or a liquid metal. The heated coolant is made to flow through a heat exchanger where water is converted into high-temperature steam. The generated steam is then allowed to drive a steam turbine. The steam, after doing its work, is converted back into the water and recycled to the heat exchanger. The steam turbine is coupled to an alternator which generates electricity. The generated electrical voltage is then stepped up using a transformer for the purpose of long distance transmission.

The image below shows basic components and layout of a nuclear power station.
components and layout of a nuclear power plant

Basic components of a nuclear power plant

Nuclear Reactor

A nuclear reactor is a special apparatus used to perform nuclear fission. Since the nuclear fission is radioactive, the reactor is covered by a protective shield. Splitting up of nuclei of heavy atoms is called as nuclear fission, during which huge amount of energy is released. Nuclear fission is done by bombarding slow moving neutrons on the nuclei of heavy element. As the nuclei break up, it releases energy as well as more neutrons which further cause fission of neighboring atoms. Hence, it is a chain reaction and it must be controlled, otherwise it may result in explosion. A nuclear reactor consists of fuel rods, control rods and moderator. A fuel rod contains small round fuel pallets (uranium pallets). Control rods are of cadmium which absorb neutrons. They are inserted into reactor and can be moved in or out to control the reaction. The moderator can be graphite rods or the coolant itself. Moderator slows down the neutrons before they bombard on the fuel rods.

Two types of nuclear reactors that are widely used -
  1. Pressurised Water Reactor (PWR) -
    This type of reactor uses regular water as coolant. The coolant (water) is kept at very high pressure so that it does not boil. The heated water is transferred through heat exchanger where water from secondary coolant loop is converted into steam. Thus the secondary loop is completely free from radioactive stuff. In a PWR, the coolant water itself acts as a moderator. Due to these advantages, pressurised water reactors are most commonly used.
  2. Boiling Water Reactor (BWR) -
    In this type of reactor only one coolant loop is present. The water is allowed to boil in the reactor. The steam is generated as it heads out of the reactor and then flows through the steam turbine. One major disadvantage of a BWR is that, the coolant water comes in direct contact with fuel rods as well as the turbine. So, there is a possibility that radioactive material could be placed on the turbine.

Heat exchanger

In the heat exchanger, the primary coolant transfers heat to the secondary coolant (water). Thus water from the secondary loop is converted into steam. The primary system and secondary system are closed loop, and they are never allowed to mix up with each other. Thus, heat exchanger helps in keeping secondary system free from radioactive stuff. Heat exchanger is absent in boiling water reactors.

Steam Turbine

Generated steam is passed through a steam turbine, which runs due to pressure of the steam. As the steam is passed through the turbine blades, the pressure of steam gradually decreases and it expands in volume. The steam turbine is coupled to an alternator through a rotating shaft.


The steam turbine rotates the shaft of an alternator thus generating electrical energy. Electrical output of the alternator is the delivered to a step up transformer to transfer it over distances.


The steam coming out of the turbine, after it has done its work, is then converted back into water in a condenser. The steam is cooled by passing it through a third cold water loop.