Energy and Electricity

The Cost of ElectricityElectricity is measured in units called “kilowatt hours” (kWh). For example…

A 3kW fire left on for 1 hour uses 3kWh of energy

A 1kW toaster left on for 2 hours uses 2kWh

A 0.5kW hoover left on for 4 hours uses __kWh

A 200W TV left on for 5 hours uses __kWh

A 2kW kettle left on for 15 minutes uses __kWh

The Cost of ElectricityTo work out how much a device costs we do the following:

Cost of electricity = Power (kW) x time (h) x cost per kWh (p)

For example, if electricity costs 8p per unit calculate the cost of the following…

1) A 2kW fire left on for 3 hours

2) A 0.2kW TV left on for 5 hours

3) A 0.1kW light bulb left on for 10 hours

4) A 0.5kW hoover left on for 1 hour

Power stations

Cooling tower

Turbine

Generator

TransformerBoiler

What does each part do?

The boiler is where the fuel is burnt to boil water. Chemical energy to heat energy.

The steam from the boiler is used to turn a turbine. Heat energy to kinetic energy.The turbine is connected to the generator, which acts like a dynamo – it generates electricity out of movement. Kinetic energy to electrical energy.

The steam is cooled down and turned back into water in the cooling tower

The National GridElectricity reaches our homes from power stations through the National Grid:

If electricity companies transmitted electricity at 230 volts through overhead power lines there would be too much ______ loss by the time electricity reaches our homes. This is because the current is ___. To overcome this they use devices called transformers to “step up” the voltage onto the power lines. They then “____ ____” the voltage at the end of the power lines before it reaches our homes. This way the voltage is _____ and the current and power loss are both ____.

Power stationStep up

transformerStep down

transformerHomes

Words – step down, high, power, low, high

Non-Renewable Energy• Three FOSSIL FUELS (___, ___ and ___) and NUCLEAR

power are non-renewable. They will run out eventually.

• Burning fossil fuels releases carbon dioxide, CO2. This is a __________ gas, and adds to the greenhouse effect which is causing global ________.

• Burning coal and oil releases sulphur dioxide, SO2 which causes _____ ______.

• Nuclear power produces no waste _____, but the nuclear ______ is very dangerous and difficult to get rid of.

• Decommissioning a nuclear power station is very _________ , and a nuclear accident could be devastating.

Words: greenhouse, waste, coal, gases, expensive, oil, acid rain, gas, warming

Renewable EnergyRenewable energy resources will never run out.

Most of them do damage the environment, but much less than non-renewables.

They do not provide much energy, and some are unreliable because they depend on weather conditions.

Wind PowerEach wind turbine contains a generator to make electricity.

They emit no pollution.

Many people think they look ugly. They are also noisy.

You need about 5000 turbines to replace one power station. This would take up a lot of space.

They are unreliable, since they only operate when the wind speed is correct – not too low or too high.

Solar EnergySolar cells generate an electric current directly from sunlight. There is no generator and no pollution.

It is a good choice in remote areas, and is used for satellites. Initial costs are high, but there are no running costs and energy is free.

In sunny countries solar power is very reliable, but only during the day. In poor weather and during the winter, power output may be low.

Solar heating panels are NOT the same as solar cells. They use the heat from the sun to heat water for household use. There is no electricity involved.

Hydroelectricity and Pumped StorageHydroelectric power uses flowing water to turn turbines. A big advantage is immediate response to increased electricity demand.

It usually requires the flooding of a valley by building a huge dam. Initial costs are high, but there is no fuel, no pollution and minimal running costs.

Environmental impact is very high, and may involve loss of habitat.

Pumped storage uses surplus night-time electricity to pump water up into a reservoir, which can then be released quickly to cope with peak demand periods.

Wave PowerWaves produce an up and down motion, which can be used to drive a generator.

A lot of small generators are needed. There is no pollution, but they may be unsightly, and must be located carefully or they will be a hazard to boats.

They are unreliable, as they will not operate if waves are too small because the wind has dropped.

Tidal BarrageA tidal barrage is a dam built across a river estuary, with turbines in it.

As the tide goes in and out, the turbines are turned.

It will prevent free access by shipping, and may alter wildlife habitats.

Tides are reliable, but electricity will only be generated during certain times each day.

Geothermal EnergyUses hot rocks underground to heat water into steam, which then turns turbines. Rocks are hot due to the decay of radioactive elements deep underground.

This an excellent source of free energy with no environmental problems.

It is only possible where hot rocks are close to the surface, because the cost of drilling is so high. There are very few geographical locations where this is an economic option.

BiomassBiomass is the general term for organic ‘stuff’ that can be burnt to produce electricity. The material is burnt in a power station to heat water, produce steam and turn turbines.

Set-up and fuel costs are low, and the process uses waste products which might otherwise end up as landfill.

The plants that grew to make biomass absorbed carbon dioxide from the atmosphere as they grew. This is released back into the atmosphere when they are burnt. The process is described as carbon neutral.

Other pollutants such as sulphur dioxide may also be released.