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The need for energy is increasing at a time when the majority of energy is created from fossil fuels that create greenhouse gas emissions. Another sobering fact is that as much as 60% of all energy delivered is wasted. For example fuels used for transport in New Zealand in 2002 were only 14.7% efficient which means that over 85% of the fuel used was wasted, mostly as heat.
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Energy
Fossil fuels are by far the main source of energy for modern civilisation - coal and gas for electricity generation; and petrol, diesel and kerosene-type fuels for land, sea and air transport.
Some two-thirds of the world’s electricity is generated by coal-fired power plants, and coal is responsible for more than a quarter of global carbon dioxide emissions. Coal is the dirtiest fossil fuel in terms of greenhouse gas emissions. For instance about 0.92 kg of carbon dioxide is typically released for every kilowatt hour of electricity produced in a coal-fired electricity generation station. Gas is a comparatively less carbon intensive fuel – about 0.52 kg of carbon dioxide is typically released for every kilowatt hour of electricity produced in a gas-fired station.
Unfortunately, we are not reducing our dependence on coal. In fact, coal emissions are set to increase hugely because of a tidal wave of new coal-fired power plants in the pipeline. More than 70 new coal-fired power plants are planned for the United States by 2012, 200 in India, and an astonishing 500 in China. A typical plant will be in operation for around 60 years or more so its legacy will be with us for a long time once built.
These new coal plants will burn about 900 million extra tons of coal each year and emit about of 2.5 billion tons of CO 2 into the atmosphere.
Burning petrol and diesel for transport also releases huge amounts of carbon dioxide into the atmosphere. About 2.3 kg of carbon dioxide is released when a litre of petrol is burned and about 2.7 kg for each litre of diesel.
Energy use in NZ
Table 1 (below) shows how energy was used in New Zealand in 2002. It highlights two importants facts.
Firstly, almost 65% of energy delivered comes from fossil fuels. Added to that is the fact that fossil fuels are used to produce about 30% of our electricity and biomass is used for 9.5% of energy. This means that about 82% of the energy used in New Zealand creates greenhouse gas emissions.
Secondly, the amount of useful energy is only 40.3% of the energy delivered. This means that nearly 60% of all energy delivered is wasted.
These facts are compelling and provide a very good case for two fundamental strategies:
- to find clean, renewable alternatives to carbon-based fuels
- to be much more energy efficient
Data source: http://eeca.govt.nz/enduse/index.aspx
PJ = petajoules (a thousand trillion joules)
NB Figures are from 2002 and are estimates aggregated from a number of sources
Delivered Energy
This is the amount of energy purchased by the final consumer. For example this is the amount of electricity passing the local meter, or the amount of petrol poured into the tank.
Useful Energy
This is the amount of useful work the delivered energy produces, excluding wasted energy from inefficiencies. For example for every 10 kWh consumed by a standard light bulb might produce about 9 kWh of wasted heat and the remaining 1 kWh produces useful light. The useful energy is 1 kWh that produces light.
Efficiency
Useful Energy divided by Delivered Energy shown as a percentage
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