Introduction to energy-chain analysis

Although in principle stationary and transport-specific energy chains can be analysed, here the assessment of the latter is explained in more detail, and is then referred to as well-to-wheel (WTW) analysis. The primary focus of WTW analysis in Europe is on global environmental impact, i.e., greenhouse-gas emissions expressed as C02-equivalents. Other issues of interest are (a) primary energy demand (which equals resource utilisation), (b) local pollutant emissions and (c) full energy or fuel supply costs. Well-to-wheel analysis covers the entire fuel supply chain from feedstock extraction, feedstock transportation, fuel manufacturing and fuel distribution to fuel use in a vehicle. 

In this evaluation only C02 from the combustion of fossil fuels is considered. The combustion of biomass is assumed to be C02 neutral because the amount of C02 

5 Examples of novel engine and transmission technologies are homogeneous combustion compression ignition (HCCI), combined combustion system (CCS), combined autoignition (CAI) and continuously variable transmission (CVT). 

A combined comparative WTW analysis of specific global emissions and fuel supply costs is typically presented in a pathway portfolio analysis. Portfolio analysis helps to identify rapidly those alternative fuels and drive trains, or combinations of these, which can lead to the highest specific GHG emission savings. 

Well-to-wheel analysis needs to be applied for all relevant time steps to understand the evolution of environmental effects and possibly costs in the short to long term. This is of specific importance when innovative processes are considered, as these are characterised by technology development and cost curves with high gradients. 

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