Current predominance of fossil energies

According to the 2008 issue of the World Energy Outlook published by IEA, in 2006, the world supply of primary energy (from oil, natural gas, coal, nuclear sources and renewable energies) amounted to 11.7 billion tonne oil equivalent [1].

One tonne oil equivalent (toe) represents the energy obtained through combustion of 1 t of oil. Even though the increasing electrification of our economy also brings other units into use, such as the kWh and the MWh (1 MWh = 0.086 toe), the widespread use of the toe as an energy unit shows that oil remains the reference energy.

Primary energy is that available before any conversion, except for energies which cannot be exploited directly (Figure 1.1). Hydroelec-tricity and nuclear energy are therefore considered as primary energies. Electricity produced from nuclear power is assigned an equivalence

Figure 1.1 Sources of primary energy (2006 figures - Source: IEA)

coefficient based on 0.33 efficiency (0.261 toe for 1 MWh of nuclear electricity).

Primary energy is then converted into secondary energy, into a form which can be used by the consumer (production of fuels in the refineries and electricity in the power stations).

The final energy is consumed by the user after the transport and distribution process.

Currently, fossil energies are by far the most widely used, providing a little over 80% of the world supply of primary energy [2]. Oil still represents the most important share (34%), followed by coal (26%), natural gas (21%), renewable energies (13%) and lastly nuclear power (6%).

Most of the renewable energy supply comes from biomass (nearly 80%). Hydroelectricity represents only 16% of this supply and the other forms of renewable energy (including wind and solar) just 4%, i.e. about 0.5% of the total primary energy consumed.

After a fast development phase in the 1970s, the proportion of nuclear power stagnated and even dropped, following the concerns raised by the accidents at Three Mile Island and especially Chernobyl, which exacerbated public distrust. This trend was amplified by the oil counter crisis, which reduced the financial attraction of nuclear power for a long period of time.

At the same time, extensive development in road and air transport generated a high demand for oil, virtually the only source of the fuels used for which there is no immediate substitute at the required scale.

In this context, the share of fossil energies used has remained more or less stable. The share of oil has dropped slightly, with a corresponding increase first in natural gas and more recently coal, which has made a remarkable come-back over the last five years. Although 'post-oil' is often mentioned, making substantial changes to the distribution of the various primary energy sources will involve considerable time and effort.

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