Hydropower electrical power calculation

We have already discuss about hydropower plant where we discuss about all component used in hydropower plant. link is here

Power Production Process

The basic principle of hydropower is that water is flow from a certain high level to a lower level, this will result water pressure which is used to move mechanical component(rotating part i.e. turbine) that converts potential energy of the water into mechanical energy. When water is stored in a place at certain height, there is potential energy stored in a form of water. And when that water is flow through penstock/pipe and hit turbine, it will convert potential energy into mechanical energy/rotational energy. Turbine's shaft is connected to generator which will convert mechanical energy into electrical energy. That's simple and known process of generating electricity, here we are going to calculate how much power will generate in hydropower.

Theoretical power(P) available in hydropower plant,

P ∝ Q x H

Where, Q = flow rate (m³/s) or water discharge

             H = Net head of water= Head race - tail race

From above equation, theoretical power or electrical power output is directly proportional to flow rate and net head of water which mean for high electrical power generation, high head and high flow rate is required. But it is not possible in all case because of geo-graphical location. It is more economical of having high head with low discharge instead of low head high discharge.

Electrical power production calculation

Potential energy of water per unit volume = P = ηρgQH

We know that the energy per unit time is the power so,

Theoretical electrical power(P) available ,

P = ηρgQH

where, η = efficiency of plant = efficiency of turbine x efficiency of generator x efficiency of transformer

ρ = density of water which value is 1000 kg/m³

g = acceleration due to gravity which value is 9.8 m/s²

So,

P = η x 1000 x 9.8 x Q x H

  = 9.8ηQH kW

As compare to other power plant, efficiency of hydropower plant is much more better. It is nearly about 95% or generally above 90% efficiency which is far better than wind power plant, solar power plant and so on. But only about 20% of world's electricity energy is provided by hydropower and remaining energy is provided by thermal power plant, nuclear power plant.

Advantages of hydropower plant

The advantage of it is given as:-

1. Renewable source of energy so can generate unlimited power.
2. Operating cost is negligible since no fuel is required. 
3. Water can be used for multipurpose such as drinking water, irrigation etc.
4. Hydropower dam can help to stop floods and erosion in rainy season.
5. Water can be saved for another time when electricity demand is high. 
6. They do not pollute the atmosphere.
7. Electrical energy can be converted into any type of energy that is used in daily life as well as in factory.

Due to these advantages, it is mostly used in the power system but it requires hilly geographical region and rivers which is not always practical for all country. In country like Nepal, China there is very good land for hydropower plant.

Disadvantages of hydropower plant

The disadvantage of it is given as:-

1. They are very capital intensive i.e. huge initial investment.
2. Due to water flow in penstock, turbine etc., it may harm aquatic life cycle.
3. For hydropower, the direction of water flow in river should be changed which will directly affect environment, ecosystem as well as local people.
4. Bursting of penstock, dam may cause flood in town or village which will directly affect local people life.
5. Huge number of people were dead (in history as well as nowadays) while constructing the hydropower plant.

These are some disadvantages but it has more advantages so it is very popular where there are hilly geographical region and rivers.