Energy Efficiency and Environmental Benefits

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Energy efficiency of fuel supply chains and their environmental impact – measured in terms of emissions – are crucial ecological parameters. Damage to the environment will be lowest for supply chains with a minimal input of non-renewable resources. Considering this, all steps in processing the fuel from its primary source (an oil well, for instance) to the vehicle must be taken into account.

The above figure illustrates the energy efficiencies of a choice of fuel supply paths. It compares the share of useful energy left at the end of the transformation chains relative to the primary input (“well to wheel“). It is obvious that hydrogen production relying on grid electricity will be inferior to diesel propulsion, today’s standard fuel in public and freight transport.

The figures cited refer to the German energy mix for electricity generation with large contributions from coal; the picture will differ for countries like Norway where water power is an important primary energy source.

The efficiency factors stated for the single process steps are typical values that do not relate to particular systems on the market. A more detailed analysis is in preparation and will become available during summer 2001.

It should be noted that “hydrogen“ here always refers to compressed gaseous hydrogen as supplied by the EUHYFIS system. Liquefaction of 1Nm3 hydrogen requires electricity equal to 33% of the energy content stored in this amount of gas. The primary energy demand in the case of grid electricity thus would amount to 100% of the hydrogen energy content.

The ecological disparities become even more pronounced when emissions in terms of CO2-equivalents are compared, as shown below.
In addition to (local) vehicle emissions and contributions from the operation of the (global) supply chain, input from the materials investment into the processing equipment (the so-called gray energy) have been included. In the evaluation, the German grid mix expected for 2010 and emissions from diesel vehicles according to the EURO 4/5 regulations in force from 2005/2008 were assumed.

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