2.12 producing electrical energy

2.12 Producing electrical energy – renewable sources

10 April 2023

Key terms

• Transformer – a device that changes the voltage of an alternating current without changing its frequency

Hydroelectric power

• Hydroelectric power stations are one example of the use of renewable energy sources

• Water is stored behind a dam, often high up in the mountains

• The height of the reservoir provides a source of potential energy

• When the water is released and flows downhill, the PE is converted to kinetic energy and the energy turns the turbines

• No burning of fuels so no pollution with nearly 90% efficiency

List the energy transformations that take place in a hydroelectric dam

Wind Power

• Wind turbines use the KE of the wind to turn the turbines to produce electricity

• No pollution is produced but people worry that the wind turbines spoil the view of the countryside and the noise produced

• Although wind is free, the turbines are expensive• No wind, no electricity• When they do operate the efficiency can be

around 35-60%

Solar power

• Solar power can be harnessed using solar cells called photovoltaic cells. When the sun shines on these cells they emit electrons which form a current

• The solar panels are expensive, but the energy source is free and no pollution is produced.

• However, the amount of electricity generated depends on how bright the sunshine is

• As with wind power, the efficiency of energy conversion varies, between 12-25 %

Compare the efficiencies of three renewable methods used to generate electricity and list

their advantages and disadvantages

Getting electricity to our homes and factories

• The UK has a network grid of pylon towers linked by copper cables that transfer electrical energy to our homes

• The voltage produced at the power station is about 25 000 V

• Engineers than increase the voltage to 400 000 V using a step-up transformer

• This reduces the energy losses during transfer, the higher the voltage the lower the current

• A step-down transformer then reduces this to 230 V for your houses (or 11 000 V for some factories)

Assessment activity

• Explain why the voltage used in the home is different from that used to transmit electricity over the national grid

• Which equipment is used to increase and decrease the voltage as electricity is transferred from the power station to our homes and factories

• Which type of renewable energy power station would you recommend to be built near your community.