This extensive report from the Intergovernmental Panel on Climate Change (IPCC) provides an assessment and analysis of renewable technologies and their potential role in mitigating climate change. The report aims to provide a definitive policy-relevant (rather than policy-prescriptive) resource for decision-makers. Following a summary for policymakers and a comprehensive technical summary, the report charts the historical development, challenges of integration, technical aspects, potential and comparative cost of the following six renewable technologies.

Bioenergy – typically offering constant and controllable output, the types of biomass and processes currently available are broad and varied in terms of technical maturity. Increased competition of food and fibre demand poses a threat to achieving high potential deployment levels of biomass for energy.
Direct solar energy – offers a practically unlimited, if variable and unpredictable, source of energy. The paper focuses on the four main types of solar power: solar thermal, photovoltaic, concentrating solar power (CSP) and solar fuels production methods.
Geothermal energy – with no significant impact from climate change on sources of supply, geothermal offers a reliable, if technically challenging, energy source that could meet around three per cent of the world’s energy demands by 2050.
Hydropower – a proven, mature and cost-competitive technology, thoughh the high up-front investment in infrastructure and planning remains a deterrent to investors and requires new financing models.
Ocean energy – the theoretical potential easily exceeds present human energy requirements, but development is still in its nascent stage and large-scale deployment is unlikely before 2020.
Wind energy – primarily used for electricity generation from large on- and offshore grid-connected wind turbines. Social acceptance, transmission and operational costs and institutional constraints are likely to restrict growth.

The report discusses the integration potential of renewable technologies, including their integration into existing energy systems, their position within the context of sustainable development and their mitigation costs and potentials. The report concludes by analysing policy options for research, development and deployment of renewable energy, such as fiscal incentives, public finance and regulations. These options are also presented by sector: electricity, heating and cooling and transportation.