REN21 , the Renewable Energy Policy Network for the 21st Century , is an organization which provides a forum for international leadership in renewable energy policy , in order to promote the rapid growth of renewable energy technologies in developing countries and industrialised economies . REN21 , the Renewable Energy Policy Network for the 21st Century , is a policy network that provides a forum for international leadership in renewable energy policy , in order to share knowledge and facilitate the rapid growth of renewable energy technologies in developing countries and industrialised economies .