Within the last 100-150 years district heating went trough a steady transformation. First generation systems used steam as the working fluid. The latest fourth generation schemes are based on the circulation of medium temperature water (50-70°C) for integration with other sources of energy, such as waste heat.

Some of pioneering groups are developing a next generation of networks allowing the utilisation of low temperature fluids to enable even wider integration possibilities. One of the main drivers behind introduction of the networks of Fourth and Fifth generation schemes is the need to integrate thermal energy storage within systems.

Worldwide demand for air-conditioning is rising at an exponential rate. It is predicted that within next 50 years cooling requirements will match and exceed the total demand for space heating.

Despite a slow response to fast growing market, the expansion of district cooling systems in developed countries is a new reality. Centralised cooling offers advantages over individual systems, including: greater efficiency; more reliable; wider use of natural refrigerants in place of synthetic gases characterised by high GWP (Global Worming Potential); and overall reduced cost.

District energy schemes represent one of the most heated frontlines in the struggle for a more sustainable future. District Heating and Cooling (DHC) at the top of modern energy chains is a long established concept that has been undergoing improvements throughout its history.

Nowadays most of the energy used to fuel DHC is sourced from far afield. However, district energy schemes are capable of reducing the consumption of the prime fuel by cogeneration at Combined Heat & Power (CHP) plants and by enabling mechanisms of the economies of scale.