IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change Heat and heat pumps

Heat, whether from fossil fuels or renewable energy, is a critical energy source for all economies. Its efficient use could play an important role in the development of transition and developing economies (UN, 2004; IEA, 2004e). It is used in industrial processes for food processing, petroleum refining, timber drying, pulp production, etc. (Chapter 7), as well as in commercial and residential buildings for space heating, hot water and cooking (Chapter 6). Many industries cogenerate both heat and electricity as an integral part of their production process (Section 4.3.5; Chapter 7), in most cases being used on-site, but at times sold for other uses off-site such as district heating schemes.

Heating and cooling using renewable energy (Section can compete with fossil fuels (IEA, 2006f). In some instances, the best use of modern biomass will be co-firing with coal at blends up to 5–10% biomass or with natural gas.

Heat pumps can be used for simple air-to-air space heating, air-to-water heating, and for utilizing waste heat in domestic, commercial and industrial applications (Chapter 6). Thermo-dynamically reverse Carnot-cycle heat pumps are more demand-side technologies but also linked with sustainable energy supply by concentrating low-grade solar heat in air and water. Their efficiency is evaluated by the coefficient of performance (COP), with COPs of 3 to 4 available commercially and over 6 using advanced turbo-refrigeration (www.mhi.co.jp/aircon/). A combination of CCGT with advanced heat-pump technology could reduce carbon emissions from supplying heat more than using a conventional gas-fired CHP plant of similar capacity.