Kit Betts-Masters

GCSE Physics

Electricity Generation

It's crucial that you have a good overview of the options that we have for electricity generation.  These will include types of power stations but also smaller scale options like solar cells, or diesel generators.  They all have their advantages and disadvantages, and a good way to learn them would be to create a fact file about each one with a description of how it works and the advantages and disadvantages about it.  Remember to BE DETAILED, just saying "expensive" will not be good enough in an exam; is it "expensive to build and maintain" or is it "more expensive than another option per MegaWatt".  Examiners are a really picky bunch!


It will probably be useful to memorise the types of energy resource that we use in two main groups, renewable and non-renewable.  Renewable means something which will come back as quickly as it can be used, for example wind and waves will always occur.  A non-renewable resource is finite, and once we've used it all then there will be none available for the foreseeable future, for example fossil fuels take millions of years being buried under high pressures to form.  This limited nature of resources affects our choices, not only for environmental reasons, but for economical ones as well.  And it's usually economical reasons which cause governments to change their policies.  But the other benefit of their being eventually forced to make these changes is that burning fossil fuels is the largest contributor of greenhouse gases to the atmosphere, which causes global warming.


Most power stations work in the same way, we call them thermal power stations.  You find some way of heating water, to make steam to turn a turbine, which turns a generator.  If you are going to memorise one sentence for your exams that's a good one, as it usually carries three marks in an explanation of a power station.  The only difference between these thermal power stations is the fuel, coal, oil, biomass, nuclear fuel,the earth's heat, even water heated by the sun; all that matters is that you make steam at a high enough pressure to turn the turbine, which turns the generator....  Other power stations use turbines to turn generators but do this directly, so if you have an energy source which is already a kinetic energy store, for example the wind, the waves or the tides you can directly turn your turbines.  Only really photovoltaic electricity generation, or chemical fuel cells don’t use turbines, for both, we'll have to explore quantum physics before we can truly understand how they work.


Make sure you try loads of questions and get your head around the types of things they might ask and the level of answer they might expect.

The really interesting part of electricity generation is how we deal with demand.  Demand is very different throughout the day, and throughout the year.  We use much more electricity for example in the mornings and in the evenings.  Just like a rush hour on the roads we’re all doing the same thing at once.  So around eight in the morning more electrical energy needs to be supplied to the national grid because so many kettles and toasters and showers and TVs and so on are being used, the same is true once everyone is home from work.  There can be even more temporary spikes in electricity, for example half time in the world cup final, or straight after strictly come dancing….  We have power stations that just come on during these times.  Gas power stations take around twenty minutes to get to peak generation, and hydroelectricity and other renewable resources can cover this short term deficit in the grid.  Larger power stations like nuclear and coal make much greater volumes of electrical energy but they take days to start up and switch off, so these are running all the time, covering the level of energy that we are always using, that demand never dips below.  Long term this helps us to aim for a low carbon emission future, whereby nuclear power provides the backbone, and renewable resources can provide the extra energy needed at peak times, with gas or biomass power just there for the back up where the the unreliable wind or solar renewable energy is not available.