some environmental advantages of using these systems in transportation, because not all steps in the supply chain are developed to the same level, e.g. too few CNG filling stations.•Changing the system in one step is feasible - as demo-strated in the case of the introduction of reformulated gasoline and the sale of energy-efficient cars - but depends on the investment and replacement rate in the oil refinery sector or the vehicle producing sector. •Complex changes may be facilitated by a hybrid strategy: double storage (gasoline and LPG), a dual drive system (electric and combustion-engine-driven), or a conversion system may guarantee the sufficiency and the reliability of the system.The electricity system(FIGURE3)The main elements of electricity system are the elec-tricity producing and distributing companies, the electricity grid(divided in high, medium and low voltage grid), the goods(e.g. appliances and light bulbs) using the electricity, and theenergy services delivered by these goods to the consumers(e.g. light, music, clean cloths and dishes).The sufficiency of this system is guaranteed by the total avail-able electricity capacity and the electricity transport capacity ofgrid. The reliability of this system depends on the regulatorystrategy of the electricity producers and the availability of back-up capacity (on production and distribution level) in case ofdisturbances. To change the transport system in a more sustainable direc-tion, one should consider •The presently available technologies differ with regard to efficiency, to flexibility, and to the ability to regulate the output, and to predictability. The mix of technologies used in a system determines the overall reliability of the system.•A substantial diversity exists of electricity production methods: Regular sources are coal, oil, natural gas, nuclear; other (renewable) sources are waste, wind, solar PV; important technologies are gas turbine, steam turbine, combustion engines, combined heat and power systems.•Some interesting change demand-side strategies are decentralised production and demand side management.Thus, each energy system contains several elements, likesources of energy, investment goods (plants, grids, vehiclesand appliances), human needs that should be fulfilled andbehavioural patterns. System change may be realised by tar-geting each of these elements. However the dynamics ofchange may differ between these elements. Grids and build-ings are constructed for half a century, appliances are in use fora decade, human behaviour may be changed quickly but main-taining desired behaviour asks also for some other efforts.P 20
P 21FIGURE2 THE TRANSPORT ENERGY SYSTEMFIGURE3 THE ELECTRICITY SYSTEMFIGURE1 TRIASENERGETICA PRINCIPLES
4.Spatial relations and energy system development.