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Energy Insights:89: Alternative energy sources

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89: Alternative energy sources


wolf at the door

Alternate Energy Sources

For the sake of simplicity, I have been looking at the state of conventional oil. But what of unconventional oil (whatever that is)? Or gas and coal, or nuclear, or renewable fuels such as wind and solar? You may have heard that hydrogen is the answer for the internal combustion engines. Unfortunately, all of these sources have problems which prevent them being the panacea we need. Some are running out like oil, others are unsuitable, and some are not usable within the period that we are looking at. They are all important aids in the effort to avoid disaster but aids only. I shall look at each and explain.

Primary energy consumption by fuel

E1. Primary Energy Consumption by Fuel (1997)

Energy Sources

E5. Energy Production by Fuel (2004) **

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The Other Fuels

The graphs below show some of the reasons why oil is so difficult to replace. E2 shows one reason why coal and other solid fuels are unsuitable replacements: to replace your petrol tank with plant biomass, for instance, it would require two and a half times the mass (rather simplified, of course).


Fuel Energy Density

E2. Fuel Energy Density

E3 shows one of the problems we would face if we switched to producing our electricity from coal instead of natural gas nearly 70% more carbon dioxide emissions with all the pollution and cleansing costs.

CO2 Emissions

E3. CO2 Emissions

The main problems with the alternatives to oil and gas are that:

  • they are generally only of use for heat and electricity, not the multitude of uses that oil in particular has (eg. transport and plastics)
  • they each have their own forms of pollution
  • even by increasing them to their maximum potential, they would find it hard to compete with the present day requirements

This last point is shown in Chart E4. Taken from Janet Ramage's book "Energy: a Guidebook" (1997), it shows that the alternative fuels would only just match the present fossil and nuclear fuels if they were expanded to their maximum. But this would involve many decades and enormous costs (wind power, for instance, would have to increase by 900,000 per cent!)

Alternate Fuel Contributions

E4. Alternative Fuel Contributions

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As noted above, all of the alternatives have their own pollution problems and this is summarised below (again from data in "Energy: a Guidebook".

Pollution Problems of Renewables
Fuel Source Problems
Oil Global warming; air pollution by vehicles; acid rain; oil spills; oil rig accidents
Natural gas Global warming; pipe leakage; methane explosions
Coal Global warming; environmental spoliation by open-cast mining; land subsidence due to deep mining; spoil heaps; groundwater pollution; acid rain
Nuclear power Global warming (despite what they say); radioactivity (routine release, risk of accident, waste disposal); misuse of fissile material by terrorists; spread of nuclear weapons
Biomass Effect of landscape of and biodiversity; groundwater pollution due to fertilisers; use of scarce water; competition with food production
Hydroelectric Displacement of populations; effect on rivers and groundwater; dams (visual intrusion and risk of accident); seismic effects; downstream effects on agriculture
Wind power Noise; visual intrusion in sensitive landscapes; bird strikes; TV interference
Tidal power Destruction of wildlife habitat; reduced dispersal of effluents
Geothermal Release of polluting gases (SO2, H2S, etc); groundwater pollution by chemicals including heavy metals; seismic effects
Solar energy Sequestration of large land areas; use of toxic materials in manufacture of PV cells; visual intrusion in both rural and urban environments

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An important element in comparing fossil fuels with other forms of energy generation goes by the unfortunately unmemorable acronym of EROEI "energy returned on energy invested". An alternative version of this is the EPR Energy Profit Ratio. To produce any energy, whether it is pumping oil out of the ground, or building and operating a wind turbine, you need to use some energy in the process. If the energy returned is less than the energy you produce, it is generally not worth producing it (but see below).

As a simple example, imagine a (very small) car whose fuel tank holds 1  liter of petrol. The car's fuel efficiency is 20 km per liter. If the nearest petrol station is 5 km away, fine you wait until the tank is quarter full then drive there to refill (positive EROEI). If it is 10 km away, you have gained nothing (and lost money) by the time you have refuelled and driven home, you only have enough fuel left to return to the station to fill up again. And if the station is 15 km away, once you have filled up and reached home, you would not have enough left to get back to refuel again. You would be better off staying at home and simply using up the existing petrol for other journeys (negative EROEI).

This example is mainly about fuel consumption rather than EROEI but the analogy holds: if you think of taking petrol from the station as extracting oil from a well, and the petrol used to drive to and from the station as the combined energy used to extract oil (manufacturing materials, building roads and pipelines, operating the well), you can see the principle.

The EROEI is calculated by taking the energy content of your energy (in whatever units you wish) and subtracting the energy used in producing the energy. The result will be a number either negative, positive or zero. The higher the number, the better.

The EPR is similar but the energy content is divided by the energy to produce: the answer will be a ratio where 1 is equal to the zero if EROEI, and less than 1 is equal to a negative.

As an example, if it takes the equivalent of 1 MJ of energy to extract oil which, when burnt, can produce 10 MJ, then the EROEI is 101 = +9 and the EPR is 10/1 = 10. If it took 15 MJ of energy to extract the oil, the answers would be 5 and 0.7.

The only time when negative EROEI can be worthwhile is if the energy produced is in a more useful form than the energy used. For example, oil can be used not only for energy generation but to make petrochemicals whereas wind-generated electricity cannot. So it could be more worthwhile using some wind-electricity to pump oil-energy out, even if the EROEI is negative. Using the car analogy above, if the journey to the 15 km petrol station was also used to deliver some goods to sell, you would gain elsewhere even if you lost out on the petrol. But negative EROEI is only acceptable if you have ample supplies of the one form and it looks likely in the future that we will be struggling for all.

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Individual Fuel Links

For more information on individual fuels, click the links below. EPR values (see above) are given on the pages according to information in Richard Heinberg's book "The Party's Over". For comparison oil and gas has dropped from 100 (in the 1940s) to 8 for discoveries in the 1970s.

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