Cold district heating

The collective term for such systems in scientific terminology is 5th generation district heating and cooling.

Due to the possibility of being operated entirely by renewable energies and at the same time contributing to balancing the fluctuating production of wind turbines and photovoltaic systems, cold local heating networks are considered a promising option for a sustainable, potentially greenhouse gas and emission-free heat supply.

As of 2019, the fifth generation heating networks described here have not yet been given a uniform name, and there are also various definitions for the general technical concept.

In the English language technical literature the terms Low temperature District Heating and Cooling (LTDHC), Low temperature networks (LTN), Cold District Heating (CHD) and Anergy networks or Anergy grid are used.

In addition, the definition of so-called low-ex networks allows to classify them as both fourth and fifth generation.

This was used to heat the school and the swimming pool in addition to various residential buildings and commercial enterprises.

Also in 1994 (according to Pellegrini and Bianchini already in 1991 [3]) a cold local heating network was built in the Swiss village Oberwald, which is operated with seepage water from the Furka base tunnel.

While the former are mainly used to supply individual houses, the latter are often found in commercial buildings which have both heating and cooling needs and have to meet these needs in parallel.

Cold local heating extends this concept to individual residential areas or districts.

[1] Cold district heating is particularly suitable where there are different types of buildings (residential, commercial, supermarkets, etc.)

and therefore there is a demand for both heating and cooling, enabling energy balancing over short or long periods of time.

Alternatively, seasonal heat storage systems allow for a balance of energy supply and demand.

This concept, which allows further agricultural use, has been realized, for example, in a cold heat network in the German town Wüstenrot.

[1] In addition, there are cold-heating networks that extract geothermal energy from tunnels and abandoned coal mines.

[1] Cold local heating systems allow a variety of network configurations.

A rough distinction can be made between open systems, in which water is fed in, passed through the network where it is supplied to the respective consumers and finally released into the environment, and closed systems, in which a carrier fluid, usually brine, circulates in a circuit.

Due to the low operating temperatures, there is no thermomechanical stress, which allows the use of ordinary polyethylene pipes without insulation, as used for drinking water supply.

A heat pump as well as a direct hot water storage tank must be installed at each connected consumer or prosumer.

For example, 20 PlusEnergy houses have been built in Wüstenrot, all of which are equipped with photovoltaic systems, a solar battery and a heat storage tank for the highest possible degree of self-supply through flexible operation of the heat pump.