P1aL16 Making Comparisons

Key Words

Air pollution - Smoke and other unpleasant waste gases make the air unpleasant or even toxic to breathe.

Capital cost - how much a structure costs to build.

Carbon dioxide - a greenhouse gas with the formula CO2

Climate Change - change in weather patterns due to global warming.

Efficient - what proportion of the total energy comes out as useful energy.

Fossil fuels - fuels derived from plants and animals that absorbed energy from the Sun millions of years ago.

Geothermal - heat from hot rocks.

Global Warming - the planet's average temperature is rising.

Hydrocarbons - substances consisting of carbon chains to which are bonded hydrogen atoms.

Operating Cost - how much it costs to run a power station.

Particulate matter - particles like soot carried into the air in smoke.

Power station - huge industrial plant where electricity is generated in vast quantities.

Reliable - energy that is always available.

Renewable energy - energy resources that will not run out and are constantly replaced.

Solar cell - a device that converts light into electrical energy.

Wave Power - energy generated by wave action.

Wind farm - a number of wind turbines in a small area.

Wind Turbine - a machine that drives a generator, and is driven by the wind.

Test Yourself

Homework
Physics GCSE
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Grade E

Power stations can harm the environment in some ways:

  • Burning fossil fuels gives out greenhouse gases;
  • Toxic waste gases can lead to cancers;
  • Wind turbines are seen as an eye-sore;
  • Hydroelectric schemes need valleys to be dammed;
  • Tidal power schemes destroy mudflats and other habitats;
  • Geothermal power stations can release gases and minerals from deep underground.

There are benefits:

  • Burning fossil fuels is cheap;
  • Wind turbines generate electricity in remote places;
  • Hydroelectric power stations generate massive amounts of electricity, and can also be used as reservoirs for drinking water;
  • Tidal power stations and wave generators have low running costs.
  • Geothermal power stations are small and do not need fuel deliveries.

Power stations that burn fossil fuels contribute a lot to global warming.  They will need to be replaced in the future.  Scientists are designing more efficient power stations which use waste heat to generate electricity, increasing their efficiency from 35 % to 50 %.

Some stations that use renewable sources are not that efficient; but that doesn't matter.  The main point is that they should be reliable, so that they can produce energy on demand, and have a reasonable running cost.

Solar cells can generate electricity where there is no mains.  A battery may be necessary to maintain the supply at night.

 

Grade C

Fossil fuels contain hydrocarbons.  They release not only carbon dioxide, but also particulate matter like soot.  Most power stations have dust precipitators that remove 95 % of the particulate matter from the gases; but 5 % is still a lot of soot, dust, and ash.  This air pollution can lead to health problems, as well as being unsightly.  The burning of fossil fuels has led to an increase in carbon dioxide which has contributed to global warming.

Fuels like biomass do not increase the overall carbon dioxide, because the carbon dioxide was taken up by plants in the last year or so, while fossil fuels had taken up their carbon dioxide millions of years ago.

The location of power stations is important:

  • Fossil fuel power stations need to be near rivers for water, and railways for fuel deliveries.  Gas can be piped in.

  • Wind turbines need windy areas;

  • Hydroelectric schemes need to be in deep valleys;

  • Geothermal power stations need to be where the rock is easy to drill.

In the exam, you need to be able to state at least one advantage and one disadvantage.

 

The demand for power varies quite a lot.  The fossil fuel power stations maintain a base load (a constant supply of electricity) because they are most efficient when they are working hard.  When the commercials come on the TV, many people go to switch on kettles to make themselves tea.  More power stations are needed at short notice to generate electricity for the extra demand.

Other important considerations are:

  • The capital cost - how much a power station costs to build;

  • The operating costs - how much the power station costs to run;

  • How much money the power station will make;

  • The reliability - will the resources be available to run in.  For example wind turbines are useless on a calm day; they need wind speeds of 50 km/h for maximum output.  If the wind speed is greater than 80 km/h, they shut down.

 

Grade A

Hydroelectric power is not as green as it's held up to be.  When a valley is flooded, the plants die and rot, releasing methane, a powerful greenhouse gas.  If the methane is dissolved in the water, it comes out as bubbles as it passes through the turbine.  As well as being a powerful greenhouse gas, methane is highly flammable, and could cause a serious explosion.

It has been found that bacteria feeding on decaying matter release protons and electrons.  These move through the water to a cathode and anode respectively.  The device acts as a battery.  If the cell is connected to an outside circuit, the current passes around.  The protons combine with oxygen from the air to make water.