Fossil fuel small-scale power generation methods

Fossil fuel small-scale power generation methods: 

Technology	Advantages	Disadvantages	Comments
Diesel and petrol powered generators	Small. Relatively low capital cost. The smaller units are easily portable.	Consume fossil fuels – therefore not sustainable. Expensive in fuel costs. Are net producers of the greenhouse gas carbon dioxide. Produce varying amounts of noise. Some petrol powered units are remarkably well muffled for internal combustion engines.	Petrol engine powered generators are generally small; up to 5 or 10kW. Diesel powered units tend to be larger, heavier, and less portable.
Technology	Advantages	Disadvantages	Comments
Fuel cells	Can be a highly efficient way of converting a fuel to useful energy, 45% or even better; 60% has been claimed	Not yet available at commercially competitive costs At present they (directly or indirectly) consume fossil fuels – therefore they are not sustainable and are net producers of the greenhouse gas carbon dioxide.	If fuel cells were used for powering homes, and the 'waste' heat then used for tasks such as heating water or space heating, the effeciency could be higher again; 85% has been claimed.

Fuel	Advantages	Disadvantages	Comments
Coal	Low cost Apparently plentiful: we will probably not run out of easily mined coal in the next few decades. It has been believed that the world's coal reserves would last a century or more, but some recent research has indicated that this was optimistic.	Not sustainable Requires around 1.7 million litres of fresh water for each gigawatt-hour of electricity generated. Produces more carbon dioxide (CO2) per Watt-hour of energy than any other generation method. The methods of mining coal can be very destructive, although responsible coal miners do a remarkably good job of restoring the land after the coal has been mined out. Very large quantities of ash have to be disposed of and a lot of smoke is produced, although in modern power stations most of the latter is separated from the waste gas stream and disposed of with the ash. Coal contains substances such as sulfur, arsenic, selenium, mercury and the radioactive elements uranium, thorium, radium and radon (see USGS). When the coal is mined and burned these substances can be released into the environment. Burned sulfur is one of the main causes of acid rain, but most modern coal-fired power stations remove most of the sulfur oxides from the released gasses. War time – For maximum efficiency coal fired power stations must be big. They therefore present a desirable target for enemy attack.	Coal has an 'unfair' advantage over 'cleaner' forms of power generation in that the power station operators do not have to pay for the damage that they are doing to the atmosphere. See: No level playing field. A coal-fired power station generates a large amount of energy in a relatively small area compared to most renewable methods. However, when all the land required for mining and disposal of ash is taken into account coal does not have any space advantage over several sustainable methods. The misleading term 'clean coal' is sometimes used to refer to coal-fired power stations that efficiently extract substances like sulfur from the coal, either before or after burning. It is impossible to burn coal without producing carbon dioxide, so all coal-fired power stations are dirty in this sense. However, it is possible to dispose of (sequestrate) the carbon dioxide so that it is not released into the atmosphere for a long time. As of the time of writing (Feb. 2006) this has not been done for a commercial scale power station. It seems that some coal-fired power stations that are not economically viable are being kept in operation because decommissioning and cleaning up would be more expensive than keeping them going.
Fuel	Advantages	Disadvantages	Comments
Natural gas	Low cost Generators are very compact Produces less CO2 than oil and much less than coal Requires much less water than coal fired power stations	Not sustainable Produces carbon dioxide. (CO2), which is an important greenhouse gas. The world's natural gas reserves are limited, but not so limited as oil reserves. Seismic surveys of the sea-bed cause death and injuries to marine species. Leakage of methane to the atmosphere, very difficult to quantify, increases the greenhouse effect.	At the rate we are using natural gas our children will see the price rise so much that it will no longer be economical as a fuel. In a more far sighted world natural gas would be reserved for more valuable uses than burning as fuel. We are consuming our children's heritage. Also see:No level playing field.
Technology	Advantages	Disadvantages	Comments
Solar thermal	Sustainable, non-polluting Heat can be stored and used to generate electricity when the sun is not shining. This gives solar thermal an advantage over wind which can only generate electricity when the wind is blowing.	Solar energy is spread relatively thinly. If a solar thermal generator is to produce much electricity it has to cover a large area. Some forms of solar power require substantial amounts of cooling water. The sun's position in the sky is continually changing so most solar thermal generators have to include expensive machinery to keep them pointed in the right direction. Solar thermal electricity is more expensive than wind and solar PV; US$0.20 to $0.28/kWh.	Solar thermal energy has been most highly developed in the United States South West where clear skies are common. While the technology has great promise it has not yet been proven to be cost-competitive on a large industrial scale. Solar power is most effectively built on flat land. I have written on Australian solar energy at Sun on the Bush.
Technology	Advantages	Disadvantages	Comments
Solar chimney (A type of solar thermal)	Sustainable, non-polluting Requires little water Unlike some other forms of solar energy this can produce electricity at night and for limited periods under clouds due to the heat stored in the 'greenhouse'.	Must cover a very large area While a small (50KW) trial station has run in Spain for some years, the technology has never been proven on a commercial scale. War time – To maximise efficiency solar chimneys must be very tall. They would present conspicuous and desirable targets for enemy attack.	The solar chimney concept uses a large 'greenhouse' to convert solar radiation into warm air. The air is then allowed to rise up a very tall (around 1km to be highly effective) chimney, turning turbines and generating power as it rises. I have written on Australian solar energy at Sun on the Bush.