The district heating net is a pipe network that supplies heating and hot water for connected consumers from a central power plant. It is a more efficient way to provide heat and power compared to localized boilers. District cooling is the cooling equivalent of district heating. Working in accordance to similar principles, district cooling delivers chilled water to buildings like offices and factories. Trigeneration is when electricity, heating and cooling are combined in the same plant.

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Co-generation is the combined production of useful thermal energy and electricity (Combined Heat and Power, CHP) from the same primary fuel. CHP can take on many forms and encompasses a range of technologies, but will always be based upon an efficient, integrated system that combines electricity production and heat recovery. By using the heat output from the electricity production for heating or industrial applications, CHP plants generally convert 75-80% of the fuel source into useful energy, while the most modern CHP plants reach efficiencies of 90% or more (IPCC, 2007).

Under the anaerobic (oxygen free) conditions of landfill sites, organic waste is broken down by micro-organisms, leading to the formation of landfill gas (LFG). LFG is a gaseous mixture which consists mostly of methane and carbon dioxide, but also of a small amount of hydrogen and occasionally trace levels of hydrogen sulphide.

With the surge in bio-based activities around the globe, a new concept called bio-refining starts to emerge. IEA Bioenergy Task 42 on Biorefineries defines biorefining as “the sustainable processing of biomass into a spectrum of marketable products and energy”. A bio-refinery combines/integrates a series of biomass conversion technologies to produce a range of products and (base-)materials, such as food, feed, chemicals, materials, oil, gas, heat and/or electricity. The concept is similar to a conventional oil-refinery where multiple petroleum products and fuels are produced.

Solar cooling technologies transform solar radiation to provide space cooling and refrigeration services. Air conditioning in buildings has traditionally been provided by air conditioners using electrically driven vapour compression chillers. These are responsible not only for GHG emissions, but also use CFCs and HCFCs and related compounds as refrigerant fluids, which also contribute to climate change and are known to deplete the ozone layer.

Community based energy services, as the term suggests, provide heating, cooling and renewable energy to more than one building. It is an alternative to the use of individual energy related systems in each building. The services often consist of: (1) Centralised generation and supply of heating/cooling as well as energy from renewable sources; (2) A distribution network to bring heating/cooling to buildings within the community; (3) Other installations (air handling units, and controls) within individual buildings.

Co-generation is the combined production of useful thermal energy and electricity (Combined Heat and Power, CHP) from the same primary fuel. CHP can take on many forms and encompass a range of technologies, but will always be based upon an efficient, integrated system that combines electricity production and heat recovery. By using the heat output from the electricity production for heating or industrial applications, CHP plants generally convert 75-80% of the fuel source into useful energy, while the most modern CHP plants reach efficiencies of 90% or more (IPCC, 2007).

Combustion is the most common way of converting solid biomass fuels to energy. Worldwide, it already provides over 90% of the energy generated from biomass, a significant part of which in the form of traditional uses for cooking and heating. Biomass of different forms can also be used to produce power (and heat) in small-scale distributed generation facilities used for rural electrification, in industrial scale applications, as well as in larger scale electricity generation and district heating plants.