A hydroelectric power station is a set of hydraulic engineering works together with a series of suitable machines. The objective of a hydroelectric power station is to produce electricity from the potential energy of moving water bodies.
This type of power plants take advantage of the potential energy of the water to generate electrical energy.
The energy produced by hydroelectric plants must be classified in all respects as renewable energy. Thanks to the water cycle, this resource can be reused endlessly for the same purpose without undergoing a purification process. The concept of renewability is subordinated to the constancy of the annual volume of total entries.
Hydroelectric plants can be activated and deactivated in a few minutes. The opening of the hydraulic gate valves are immediate. This feature provides the possibility to easily cover sudden spikes in electrical energy demand that may occur.
The first hydroelectric power station in the United States was the Hoover Dam in Arizona and Nevada.
How does a hydroelectric plant work?
A modern hydroelectric power plant consists of: a reservoir, a dam, sluices, turbines and generators.
The tank stores the "fuel" and allows operators to control the amount of water that is fed to the turbines. It also serves as a sedimentation tank. Most of the dirt and debris in the water is deposited at the bottom and away from the suction area.
The water that comes from the basin is transported to the turbines through an inlet (gate dam) and a forced conduit. An inlet filter system further cleans the water to ensure it is relatively free of suspended solids. These particles could damage the turbine blades.
Hydraulic systems work together to open and close gate valves. It allows the flow of water to flow downstream from the basin. These systems are: the regulator, the brakes, the gate controls, etc.
Hydraulic turbine drive
Regardless of the type of design, the turbine transforms the kinetic energy of the movement or fall of water into mechanical energy.
For maximum efficiency, the turbines are tailor-made for each hydroelectric plant.
What are the types of hydroelectric power plants?
Hydroelectric power stations can be divided into three large groups depending on the height of the drop. Each type uses a specific hydraulic turbine design to maximize performance.
Low tension pressure installations. The waterfall in these hydroelectric plants is less than 25 m. These facilities use Kaplan turbines.
Medium voltage installations. The waterfall in these hydroelectric plants is between 25 and 100 m. Francis turbines are used here in these hydraulic installations. It is the most common type of hydroelectric energy.
High voltage installations. The waterfall in these hydroelectric plants is greater than 100 m. In hydroelectric power plants with a waterfall between 100 and 400 m. Francis turbines are used, while for water levels greater than 400 m, Pelton turbines are used.
What are pumping stations?
Pumped storage plants are power plants that fill their own storage basin with water when electricity is produced in excess of consumption.
The power plant buys electricity at a price below its average price. At which point it changes its configuration and pumps water into its storage tanks. When consumption exceeds the electricity supply, the power station sells the electricity it produces from its storage tanks. The price is more expensive than its average.
The pumping stations use two reservoirs located at different heights. When there is demand of electricity, the plant generates electric power like a conventional plant. Water falls from the upper reservoir, drives the turbines, and is stored in the lower reservoir.
When demand is low, the water from the lower reservoir is pumped back to the upper reservoir on foot.
Characteristics of a hydroelectric power plant
The main characteristics that determine the production capacity of a hydroelectric power station are:
The power depends on the difference in level between the average water level of the reservoirs.
The maximum water flow that the plant is capable of passing through the turbines.
The characteristics of turbines and electric generators.
The energy that the plant is capable of guaranteeing in a certain time (generally one year).
There are four turbines used to transform mechanical energy into electricity:
Advantages of hydroelectric power plants
The benefits of electricity generation through hydroelectric plants compared to other alternatives are:
Low economic cost
Fuel is not necessary and does not need to be imported.
The overall cost of labor is low, as the plants are automated and understaffed during operation.
A hydroelectric power station can be established at relatively low construction costs. It provides a useful source of revenue to offset base operating costs.
This way of generating energy does not emit greenhouse gases.
Large hydroelectric dams can control floods, which otherwise affect people living near these projects.
Other types of activities: Recreational activities, sports and tourism
The reservoirs located in the central, sometimes offer facilities for water sports, becoming tourist attractions in themselves.
In some countries, fish farming on bases is common.
It can support the establishment of cultivation relatively constant with the reach of water.
Disadvantages of hydroelectric power plants
A problem related to hydroelectric power plants is the accumulation of sediment in the upper reservoir. This problem inevitably appears to be found over time.
To avoid this, the accumulated sediments must be dredged periodically.
The presence of a dam implies certain complications at the environmental level:
Dams block the transport of solids from rivers flowing (sand and gravel).
The water leaving the plant is sediment-free, altering the balance between solid supply and erosive activity in downstream waters. Due to the reduced or no solid contribution, there is the phenomenon of coastal erosion.
Destruction of natural habitats.
Many of these environmental problems do not occur in "MINI-HYDRO" systems. In most cases they do not require the construction of dams.