Modern technology has developed in a manner which often conflicts with the environment. Nevertheless, it is possible and practical to achieve a high level of technology without altering the overall environment or running out of non-renewable natural resources. 　　There are two basic methods of conserving the natural environment. One is alternative technology in which new techniques must be found for providing power in a more decentralized manner. The other is to try to minimize the effects of modern technology by the more efficient use of materials and more effective pollution control. 　　Present energy policies of the western world are seeking new energy sources to meet the demands of a growing population. The main sources used have been oil, gas, and coal, which are in limited supply, as well as nuclear power. Hydroelectric, wind and solar energy are all alternative possibilities, whereas only solar energy is likely to become the main power source for many countries.