Generating Electricity

Why do we need electrical energy? We need electrical energy to power the appliances in our homes. Electrical energy powers factories in order to make things. Without electricity we wouldn’t have technology as we know it today. Life would be much simpler!

Energy Resources There are a number of sources of energy that we could use to generate electricity. The most common are called fossil fuels. Power stations use fossil fuels to generate electricity. We burn fossil fuels to release heat energy. The heat energy is used to heat water to produce steam. The steam drives a turbine and then a generator which converts the kinetic energy of the turbine into electrical energy.

Power station Steam Turbines Generator

Conventional Ways of Generating Electricity Fossil fuels consist of Coal, Oil and Gas. Coal – Burning coal releases Carbon Dioxide (a Greenhouse gas) and Sulphur Dioxide. Both of these gases dissolve into the clouds and create acid rain. Oil – Burning oil also releases Carbon Dioxide and Sulphur Dioxide. Gas – Burning gas releases Carbon Dioxide gas.

Nuclear Power - Not a Fossil Fuel! Uranium, which is a nuclear fuel, is not burnt. A nuclear reaction is required to release the energy. Nuclear – They do not produce ‘greenhouse Gases’ or produce acid rain. When they are running normally, very little radiation escapes to the surroundings. An accident could cause extreme damage to the surrounding area from radiation and nuclear fallout. Also getting rid of the dangerous waste produced is costly. However the cost of the actual nuclear fuel is very low.

Fossil fuels and Nuclear fuels will eventually run out. Fossil fuels take millions of years to form in the Earth’s surface and they are being used up faster than they are being made. This means fossil fuels will eventually run out! Also, we only have a limited supply of nuclear fuel and so this will also eventually run out.

Alternatives to Fossil Fuel? If both Nuclear fuel and Fossil fuels will eventually run then it makes sense to replace them with something else. Also, it makes sense to replace them with something which does not pollute the Earth!

Types of energy sources Non renewable Coal Oil Gas Nuclear Renewable Solar Wind Hydroelectric Tidal Geothermal Biomass Non-renewable will not be replaced. Renewable are being replaced all the time.

SOLAR ENERGY The Sun can be described as our ultimate source of energy. Energy to grow our food comes from the Sun. (Photosynthesis converts light into plant food) The Sun heats the Earth. The energy from the Sun drives the weather which gives us wind, waves and rain.

We can change sunlight to Electricity by using solar Photovoltaic cells. This electrical Energy can then be used directly in the home (sometimes on calculators) or in larger scale projects as shown opposite. However, Solar Cells are quite expensive to buy and a very large area of cells is required to generate a substantial amount of power, also, they do not produce a constant supply of power e.g at night. Despite this, they are often the best energy source for producing electricity in remote locations e.g on a satellite or when only small amounts of electricity are needed.

WIND ENERGY Wind is another kind of energy that makes things work. You can’t see the wind, but when it blows on a windy day you can feel it push against your body. Some areas of the world have areas that are windy most of the year, but the amount of electricity produced always changes with the strength of the wind.

Blowing wind spins the blades on a wind turbine just like a large toy pin-wheel. The spinning blades turn a generator that makes electricity. Some people say that ‘wind farms’ look unsightly and that they produce a lot of noise as they turn around. This could cause are a nuisance to people living nearby. This is called visual and noise pollution.

HYDROELECTRIC ENERGY Moving or falling water can be used to do work. Years ago moving water turned wooden wheels to grind flour. Today moving water is used to make electricity in HYDROELECTRIC POWER STATIONS.

Hydroelectric power stations use water to make electricity Hydroelectric power stations use water to make electricity. Dams, usually in the mountains, are built to hold river water forming a huge lake this water then flows through a pipe called a penstock and into a machine called a turbine which has blades like a big fan. The water pushes against the blades and makes them turn. This rotating turbine is connected to a generator that makes electricity. Hydroelectric schemes are generally very reliable. They can be started very quickly to meet sudden increases in demand for electricity. They can also be used in reverse using surplus energy from other stations to pump water up to the top reservoir, ready to be used again.

Problems with Hydroelectric Power Hydroelectric schemes involve damming upland river valleys. This involves flooding vast areas of land that could have been used for farming or forestry. Hydroelectric power stations cannot produce a constant supply of electricity – eventually the water in the top dam will run out and will only be able to supply electricity when it is refilled.

GEOTHERMAL ENERGY Geothermal means “earth heat” and is as old as the world itself. Deep underground the earth is very hot and this can be used to heat water.

Around 3000m below the earths surface the rock is molten. Water sometimes comes close to this rock and turns into steam. This water can reach temperatures of more than 230degrees Celsius (Remember water boils at 100 degrees) In some areas of the world there is enough steam produced to turn a Turbine and produce Electricity.

TIDAL ENERGY The energy of moving water due to the flow of the tides can be harnessed to produce electricity.

The way that electricity is generated from the tide is similar to hydroelectric stations, except that water is able to flow in both directions. the photograph opposite shows a tidal barrage built across an estuary, and also one of the huge turbines that will turn when water rushes through it In its simplest form the barrage directs the flow of the tide through a turbine which turns to move a generator and create electricity. However building barrages across river estuaries can destroy the habitat of many organisms e.g sea birds and the other animals on which they feed.

Biomass Another sustainable energy resource is plant matter which is called Biomass. Forests and certain crops can be cultivated to provide fuel for burning. The fuel is burnt to release heat. The heat boils water to produce steam which turns a generator. The generator converts the KE of the steam into electricity.