page_title: District heating
section_title: Fifth Generation/Cold district heating
hierarchical_section_title: District heating / History / Generations of district heating / Fifth Generation/Cold district heating
caption_attribution_description: English: A circular representation of a 5GDHC system. The network is balanced over the year, with warm return flows from cooling supply and cold return flows from heating supply covering as much of the demand as possible. Any residual heat or cold demand is supplied using renewable sources.
context_page_description: District heating is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels or biomass, but heat-only boiler stations, geothermal heating, heat pumps and central solar heating are also used, as well as heat waste from nuclear power electricity generation. District heating plants can provide higher efficiencies and better pollution control than localized boilers. According to some research, district heating with combined heat and power is the cheapest method of cutting carbon emissions, and has one of the lowest carbon footprints of all fossil generation plants. Fifth generation district heat networks do not use combustion on-site and have zero emissions of CO2 and NO2 on-site; they employ heat transfer which uses electricity which may be generated from renewable energy, or from remote fossil fuelled power stations. A combination of CHP and centralized heat pumps are used in the Stockholm multi energy system.
context_section_description: A fifth generation district heating and cooling network (5GDHC), also called "cold district heating", distributes heat at near ambient ground temperature: this minimizes heat losses to the ground and reduces the need for extensive insulation. Each building on the network uses a heat pump in its own plant room to extract heat from the ambient circuit when it needs heat, and uses the same heat pump in reverse to reject heat when it needs cooling.  This allows waste heat from cooling to be recycled to those buildings which need heating on a "Heat Sharing Network".  The overall temperature within the ambient circuit is controlled by heat exchange with an aquifer or another water source to remain within a temperature range from 10 °C to 25 °C.
  A modern building with a low temperature internal heat distribution system can install an efficient heat pump delivering heat output at 45 °C. An older building with a higher temperature internal distribution system like radiators will require a high temperature heat pump to deliver heat output.
  Network piping for ambient ground temperature networks is less expensive to install than earlier generations as it does not need heavy insulation for the piping circuits and minimizes heat losses to the ground. All buildings on the network are required to install and maintain individual heat pump systems to meet their heating and cooling temperature needs, each with capacity to satisfy its own peak demand. Because fifth generation district heating and cooling systems operate at ambient ground temperature they can be used both for heating and cooling. The cold ring that feeds the heat pumps can be fed by various (low-temperature) heat sources including ambient heat, ambient water from rivers, lakes, sea or lagoons, and waste heat from industrial or commercial sources. 
  A larger example of a fifth generation heating and cooling grid is Mijnwater in Heerlen, the Netherlands
  . In this case the distinguishing features are that heat and cold are always exchanged on the grid. The system is driven not by the supply, but by the demand from customers for heat or cold.
  A fifth generation network ("Balanced Energy Network", BEN) was installed in 2016 at two large buildings of the London South Bank University as a research and development project.
caption: Schematic function of a "cold district heating" system
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