What is quantity of supply?
The amount of an energy source that is available for generating electricity is referred to on this site as that energy source's quantity of supply. Every energy source has strengths and weaknesses, such as its inherent limitations on quantity of supply, which could contribute to the likelihood of an energy gap, when supply falls short of demand, and might cause interruptions to the electricity supply.
For example, fossil fuels – gas, coal and oil – are finite resources: eventually they will run out, presenting a quantity of supply challenge at some stage in the future. On the other hand, renewable energy sources, such as wind, sunlight and tides, are practically inexhaustible, although the potential to harness them has limits.
There are limits to how much generating technology the UK can build to convert an energy source into electricity. Constraints include finding suitable sites, cost of construction and the length of time it takes to plan and build power stations.
The UK Government favours a diverse mix of generating technologies where the strengths of one energy source compensate for another's weaknesses.
If the Government is to meet its carbon-reduction commitments, the UK will have to increase the use of low-carbon energy sources such as nuclear and renewables. Furthermore, the majority of fossil-fuelled power stations will have to be fitted with carbon capture and storage (CCS) technology – although this has yet to be proved at an industrial scale, and will make power stations more expensive to build and less efficient to run.
Offshore wind makes a contribution to the mix. The technology is developing and a large increase in deployment over 2010 levels is expected by 2030.
New nuclear power stations are also proposed for the UK. Each new reactor could supply up to 4% of the UK's electricity needs, based on current demand.
What does it mean for the UK?
Each of the different energy sources has its quantity of supply strengths and weaknesses, all with important impacts for the UK.
The Energy Sources
Wind is a practically inexhaustible source of energy. The biggest constraint on harnessing the wind is the number of turbines the UK can build, but the move offshore opens up a greater number of suitably windy sites.
The UK's climate and latitude make it a less than ideal location for harnessing solar energy. But improvements in solar panel performance and using solar energy wherever possible could go some way to addressing these challenges.
As a renewable energy source, hydropower is theoretically inexhaustible, but the best sites have already been exploited.
The sea is a practically inexhaustible source of energy and the UK is in a good position to harness the movement of the sea to generate electricity. But the technologies to do so are currently in the early stages of development.
Nuclear energy's biggest quantity of supply challenge is that nuclear power stations take so long to plan and build. But Government policies to speed up construction time without compromising safety and accountability, and more transparent communications between energy companies, Government and the public, help to alleviate these constraints.
The world's gas reserves could last until the 2070s at the current rate of consumption, but that rate is likely to increase, depleting the reserves more rapidly. Gas is an important fuel for UK electricity generation, and greater efficiency and a diverse mix of generating technologies should help to stretch gas resources further.
Coal is a finite fossil fuel, although it won't run out until the 2120s at current usage rates. But the UK's climate change commitments mean that no more coal-fired power stations can be built without technology to reduce their carbon emissions.
Oil is a finite fossil fuel and will run out around the 2050s at the current rate of consumption. Oil-fired plants are used only for meeting peaks in demand in the UK and will be phased out of operation by 2015.