MODEL ANALYSES FOR SUSTAINABLE ENERGY SUPPLY TAKING RESOURCE AND ENVIRONMENTAL CONSTRAINTS INTO CONSIDERATION

This paper aims at clarifying kg points for realizing sustainable ener gy supply under restrictions on resource and environment. For this pur pose, we first developed a database to estimate life cycle efficiencie s and greenhouse gas emissions for various energy systems. Then on the basis of this life cycle assessment, we quantitatively define the con cept of 'Sustainability Limitations' on resource depletion and environ mental emissions. From this concept, present world is judged to be uns ustainable both from resource and environmental viewpoints. At the sam e time, we clarify how far present world is from Sustainability Limita tions. Then we describe our mathematical model simulating global energ y supply and demand in ultra-long term. In this model, the concept of Sustainability Limitations is utilized so as to impose economic incent ives to make energy system shift to a sustainable one in long term. Su stainability limitations of resource depletion and CO2 emissions are t aken into consideration. As energy resources. this model includes coal , oil, natural gas, other unconventional fossil fuels, uranium and ren ewable resources. As energy technologies, it includes major technologi es of mining, transport, conversion and final utilization. Computed re sults have shown that present energy system, which is judged to be uns ustainable, shifts to a sustainable system in the ultra-long term with appropriate incentives.