6.POWER STATIONS THAT USE RENEWABLE RESOURCES

6.1.Wind farms

Wind farms use the kinetic energy of the wind to generate electricity.The wind turns the blades of a turbine at the top of a tower.The blades are connected to a gearbox which increases the rotational speed of the generator.

The output and efficiency of a wind farm depend on two factors:
-the location of the farm,which determines the speed and strength of the winds.
-the number of turbines that can be installed there.

6.2.Hydroelectric power stations

Hydroelectric power stations use the energy of falling water to produce electricity.
There are two main types of hydroelectric power stations:

-In conventional hydroelectric stations,the water flows from the reservoir to the turbines through a high-pressure conduit.Then it flows out, usually into a river.

-In pumped-storage hydroelectric stations,the water flows from the turbines to a second reservoir.Then it is pumped back up to the higher reservoir and stored for later.These stations are often built in areas where there isn't enough rain or river water to keep the upper reservoir full, so the water must be reused.
 

Solar power stations use energy from sunlight to generate electricity.There are two types of solar power stations:solar thermal and photovoltaic.

6.3. Solar thermal stations

Solar thermal stations can use sunlight in two ways:
-With solar collectors that absorb sunlight in order to produce heat.
-With mirrors called heliostats that reflect and concentrate sunlight in one place.

Photovoltaic stations
In photovoltaic stations, solar pannels convert sunlight directly into electricity.Each panel contains many photovoltaic cells.
Small solar power installations can provide energy for homes and rural areas.Excess power can be stored in batteries or accumulators and used at night.

6.4.Biomass power stations 

Biomass is any organic material that is produced by natural processes.

There are many types of biomass which can be used to produce energy.
Plants materials can be composted and fermented in tanks called digesters.These processes convert biomass into fuel.

In a biomass power station the fuel used to produce energy comes from biomass.The steam produced from burning the biomass moves a turbine that is connected to a generator.

6.5.Marine power stations

Marine power stations use the movement of ocean water to generate elctricity.
There are three general types of marine power stations:

-Tidal power stations,which use the energy of tides.



-Wave power stations,which use the energy of waves.


-Ocean thermal conversion stations,which use the difference in water temperature between the surface of the ocean and deeper areas to produce energy.

6.6.Geothermal power stations 

Geothermal power stations use natural heat from the deepest underground layers of our planet.
Geothermal energy can be used in two ways:
-It can be use directly to provide hot water for heating and industrial uses.
-It can be used indirectly to drive generators and produce electricity.