ABSTRACT
Renewable energy flows are very large in comparison with humankind's use of energy. Therefore, in principle, all our energy needs, both now and into the future, can be met by energy from renewable sources (see Box 2.1). Technologies exist that convert renewable energy flows to modern energy carriers or directly into desired energy services. Technological development during the past few decades has resulted in modern renewable energy supply becoming competitive in a number of situations. Further technological development and industrial learning will continue to bring costs down. When environmental costs and security of supply considerations are included, renewable energy has even wider markets. With decisive efforts to speed up the development and dissemination of renewable energy technologies and systems, all human energy needs could be met by rerouting a small fraction of naturally occurring renewable energy flows within a century.
