Connection to a Cold Local Heating Network (Anergy Network)

A low-temperature network (8-20 °C) links several buildings via decentralised heat pumps — each building draws or feeds heat and cooling and uses the network as its source.

How does a cold district heating network work?

A cold district heating network – also known as an anergy network or fifth-generation district heating and cooling (5GDHC) – connects several buildings via an uninsulated pipe network in which, instead of hot water, only lukewarm water at 8 to 20 °C circulates. Each connected building has its own water-to-water or brine-to-water heat pump, which extracts heat from this network water and raises it to the flow temperature required in the building. Borehole fields, groundwater, industrial waste heat or photovoltaic-thermal collectors feed the network as heat sources. The particular advantage: buildings that are cooling release heat into the network, buildings that are heating extract it – the network acts as storage and balancing element. Thanks to the stable source temperature, the decentralised heat pumps achieve a seasonal performance factor of 4.5 to 5.5. In summer, the network also enables passive cooling with minimal electricity input.

Which buildings are suitable for connection to cold district heating?

Cold district heating is a neighbourhood solution, not a single-building concept. It is suitable for new-build districts, urban regeneration areas, university campuses and industrial estates where several buildings are supplied jointly and ideally there is a mix of heating and cooling demand. A prerequisite is a district or cooperative structure that bears construction and operation of the network, plus an available anergy source such as boreholes, groundwater or waste heat. Individual buildings without an accessible network are ruled out. Compared with conventional district heating, the pipes are cheaper because no insulation is needed and there are no distribution losses; the heat pumps in the buildings, however, involve higher investment than a substation.

What does connection to an anergy network actually deliver?

Final energy falls by 60 to 85 %, CO2 emissions by more than 95 % if the heat pumps run on green electricity. A new-build district with five apartment buildings and a total heat demand of 600,000 kWh saves around 547,000 kWh of final energy per year compared with gas boilers. The investment is 800 to 1,500 € per metre of district network and 25,000 to 60,000 € per decentralised heat pump. Over a 30-year service life, payback is 15 to 25 years, usually borne by district or municipal financing.

Energy carrier

Erdgas, Heizöl, Fernwärme alt → Strom (WP) + Anergie-Netz

Savings potential

60-85 % Endenergie, >95 % CO2 (bei Ökostrom)

Worked example

A new-build district consists of five apartment buildings, each with 800 m² of usable floor area, and a total heat demand of 600,000 kWh per year for heating and hot water. In the reference case, each building would have received its own gas condensing boiler with an efficiency of 0.90, corresponding to a natural gas consumption of around 667,000 kWh. Instead, a cold district heating network fed by a borehole field is built; each building receives a decentralised heat pump which, thanks to the stable network temperature, achieves a seasonal performance factor of 5.0. The final energy saving is calculated as 600,000 × (1/0.90 − 1/5.0) = 600,000 × (1.111 − 0.200) = 600,000 × 0.911 = 546,667 kWh per year. The electricity demand of the five heat pumps is only 120,000 kWh. If they are supplied with green electricity, the district's heat supply is almost CO2-free.

Investment & payback

Quartiersnetz: 800-1.500 €/m Leitung; dezentrale WP pro Gebäude: 25.000-60.000 € · Service life: 30 a · Payback: 15-25 (oft Quartiers- oder kommunale Finanzierung) a

Applicability

Requirements

Exclusion criteria

Typical buildings

Frequently asked questions

What is the difference between cold district heating and conventional district heating?

Conventional district heating transports hot water at 70 to 120 °C in insulated pipes to a substation in the building. Cold district heating carries only lukewarm water at 8 to 20 °C in uninsulated pipes; each building raises the temperature with its own heat pump. This eliminates distribution losses, the network can heat and cool simultaneously, and the pipes are cheaper. In return, the technology in the building is more complex.

How much does a cold district heating network cost?

A cold district heating network costs 800 to 1,500 € per metre of pipe in the district, plus 25,000 to 60,000 € for the decentralised heat pump per building and the cost of the anergy source such as a borehole field or wells. Payback is 15 to 25 years, over a service life of 30 years. Financing is usually via district companies, cooperatives or municipalities, often with subsidies.

Can a cold district heating network also provide cooling?

Yes, cold district heating networks can cool buildings in summer. At network temperatures of 8 to 20 °C, a heat exchanger is sufficient to passively supply thermally activated building systems or chilled ceilings – only the circulation pumps need electricity. The heat released into the network regenerates the borehole field or is used by buildings with simultaneous heat demand. This balancing between heating and cooling is a key efficiency advantage of the concept.

Which districts are suitable for cold district heating?

Cold district heating is suitable for new-build districts, urban regeneration areas, university campuses and industrial estates with several buildings and, ideally, mixed heating and cooling demand. A joint operating structure and an anergy source such as boreholes, groundwater or waste heat are required. The combination of residential buildings with offices, data centres or commercial premises whose waste heat is utilised in the network is particularly favourable. The concept is not applicable to individual buildings.

What seasonal performance factor do heat pumps on an anergy network achieve?

Heat pumps on a cold district heating network achieve a seasonal performance factor of 4.5 to 5.5. This is higher than for borehole heat exchangers on a single building, because the network keeps the source temperature stable through balancing between buildings and regeneration from waste heat. With a heat demand of 600,000 kWh in the district, a seasonal performance factor of 5.0 means an electricity demand of only 120,000 kWh, i.e. 80 % less final energy than with gas boilers.

Related measures

Standards & sources

Metering points in the EDM Toolbox

Komplexe Bilanzierung erforderlich: Wärmemengen-/Kältezähler an Übergabepunkten (Bezug + Einspeisung), Strom dezentrale WPs, Netztemperaturen Vorlauf/Rücklauf. EDM Toolbox + Multi-Site-Aggregation perfekt geeignet.

All measures