Dag Henning, Ph.D.IKP Energy Systems, Link?ping Institute of TechnologyS-581 83 Link?ping, SwedenPhone +46 13 28 27 12, Fax +46 13 28 17 88, e-mail
Energy may be supplied by several sources but sustainability requires a moderate energy demand. Through systems analysis, resource utilisation that nature can withstand may be found. Computer models can treat complex correlations between phenomena and helps in finding beneficial system designs. By model construction, the important parameters and their relations must be known and assumed to remain valid. The input must be complete, correct and consistent. It must be scrutinised that the output is reasonable. Energy models may reflect the planned economy of a single utility or many consumers that may find energy conservation, energy carrier switching and load management profitable compared to the energy supply cost. Environmental impact can be represented by emission limitations and uncertain external costs. Energy system optimisation models can consider many component combinations and present the system design and operation that best serve the objective, normally minimum cost for satisfying useful energy demand. Through scenarios and sensitivity analyses, the influence of varying conditions should be analysed and robust strategies may be found. It should be easy to test unlikely conditions that may show favourable but not obvious solutions, such as co-operation beneficial to many actors. Besides results, modelling gives insights to the involved persons and improves the understanding of system behaviour, which may be more valuable than the, after all, uncertain result numbers. Long-term studies are problematic because the foundations for costs may include new elements (e.g. environmental externalities) and discounting reduces the importance of future activities. A model must prove to be an adequate tool but many factors outside models must be considered by decision making.
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