Sustainable energy technologies are being developed and introduced worldwide. However, there can be obstacles to this process. Part 3 looks at some of the technical, economic, strategic and environmental limitations and problems facing the development and implementation of sustainable energy options. It focuses in particular on the institutional difficulties of obtaining support for the development of renewable energy technology, and on the problems of winning acceptance from the public for the use of such novel technologies. Although renewable energy technologies are relatively benign in environmental terms compared with conventional energy technology, they may still have local environmental impacts and adverse public reactions can be an obstacle to implementation.