Coal
The fuel that powered the West’s industrialisation is still the most popular fossil fuel: around 6.2 billion tonnes are consumed annually, 75% of which is burned to produce electricity. A little under half of the world’s power is made this way.
Global consumption increased by 4.5% in 2006, with most of that increased demand coming from the Asia–Pacific region, and principally China, which opens one new coal-fired power station roughly every 10 days.
The 1990s' ‘dash for gas’ means that use of coal has fallen in the UK, although it has been rising again in recent years due to the increased gas prices. It now represents 17% of primary energy demand compared to 31% in 1990. However, new coal-fired power stations are planned, in part to help meet expectations of future electricity demand, so coal use may not decline much further. The challenge for engineers in this sector is to develop systems to capture and store the CO2 to greatly reduce coal power’s impact on the earth’s climate.
At current rates of use, total known coal reserves – including the most polluting and low energy types – may last another 300 years, but with gas and oil becoming increasingly scarce, and demand for coal going up, that figure may soon look grossly over-optimistic.
Gas
Gas is a cleaner fuel than coal and it provides the UK with about 40% of its primary energy. We are the world’s fourth largest producer, with more than 200 off-shore fields in production and reserves of c18 billion barrels of oil equivalent. However, rates of production are slowing.
The Middle East has the world’s largest proven reserves, at 73.47 trillion cubic metres or 40.5% of world supply. As well as being the second largest consumer of gas, Russia is also the second biggest exporter, supplying many European countries. The income from gas underpins a resurgent Russian economy and political confidence.
Oil
Oil is the fossil fuel most in the headlines, especially now as its price has more than doubled in the space of a year. Although factors such as war and commodity speculation are influencing that price, it is widely believed that oil production peaked at 82 million barrels per day in 2005.
Demand is growing at around 2% per year. If oil production has peaked, though, that level of demand simply cannot be met, so prices are bound to stay high.
How are fossil fuels used?
Coal, oil and gas powered power stations all work on similar principles: the fuel is burned to heat water, with the resulting steam being used to drive a turbine. Depending on the fuel and the particular technology being used, around 50-60% of the energy contained within the raw fuel going into a typical power station is lost in the form of waste heat emanating from the cooling towers.
More modern ‘combined heat and power (CHP) designs, capture and make good use of this heat, rising overall conversion efficiencies to 80% and more. There are currently around 1300 CHP sites in the UK, producing 6% of our electricity.