While the concept of district heating is not new, it is worth taking a closer look at the merits of district heating in terms of sustainability and resources.
KWD-globalpipe: District heating refers to the supply of heat to buildings. The thermal energy generated at a central point is transported to the consumer by means of a pipe network, with the purpose of heating the building, water and other industrial use.
Difference between “Local Heating” and “District Heating”
Firstly, a small excursion to the terminology. In professional circles, the term district heating / local heating is often used, since the majority of installations are considered to be “local heating” supplies. The terms are used in different ways, even though they basically refer to the same technology.
- Local heating describes smaller networks
- District heating describes larger networks
The Federal Association for Geothermal Energy writes: “Local heating is defined as the transfer of heat through a local heating network between buildings for heating purposes, if the heat transfer takes place only over relatively short distances compared to district heating.
There is no legal distinction between local and district heating. According to the Federal Supreme Court, district heating is considered to be district heating as soon as a third party produces heat in a business-like manner and distributes it to others. A spatial distance is not taken into account.
For the sake of simplicity, the term district heating is used as a superordinate term in the following text.
Milestones in the development of district heating
- The first generation of district heating was developed in the 19th century using steam. At that time, people usually used individual fireplaces to heat their buildings. This had a number of disadvantages, such as the constant danger of fire and the permanent air pollution by ashes. As a result, centralising the heat supply on a larger scale created the first commercial district heating supply in densely populated cities and town centres. This was also the case in Hamburg, where the city hall, for example, was supplied with steam for heating purposes as early as 1894 from a power station located more than 300 metres away.
- In order to minimise the high risk of corrosion and at the same time increase efficiency, the heat transfer medium, steam, was replaced by hot water in the second generation of district heating supply.
- The third generation of district heating systems as we know them today was characterised by the optimisation of the control system using modern system components, such as a transfer station.
- For some years now, the fourth generation of district heating has been developed and partly already installed. In contrast to previous generations, it is possible to connect different heat sources to the district heating network at the same time, thus creating an optimal interaction between energy sources, their distribution and consumption. Thus, district heating today can also be used in many cases to bring in renewable energies, such as from solar thermal open space systems or from other future energy sources, thus reducing greenhouse gases.
As a result of this development and also as a consequence of the steadily decreasing energy demand thanks to more efficient building materials, district heating has become an important instrument in times of climate change.
Advantages of district heating
In addition to the lower environmental impact, district heating offers numerous advantages over conventional heating, such as greater efficiency in the utilisation of fuels, space saving due to the elimination of fuel storage, high operational safety, high fire protection and simple operation. Due to these aspects, district heating has been able to establish itself firmly as a heat supply in the energy market.
According to a study by the BDEW (Federal Association of the Energy and Water Industry), in 2019 approx. 14% of all apartments and approx. 7% of all residential buildings in Germany were supplied with district heating. For structural reasons, the system is most widespread in the cities of Berlin and Hamburg and, for historical reasons, in eastern Germany. This development is being further promoted, for example, by the Combined Heat and Power Act (KWGK).
Products of Conex Bänninger for district heating
For the ideal connection of system components required for district heating in buildings, Conex Bänninger offers the complete solution >B< Press Solar for solar and district heating installations.
The press fittings have a green FKM sealing element and are designed to leak at pressures between 0,1 and 6,0 bar when unpressed, thanks to the patented O-ring contour. They also meet the requirements of the AGFW worksheet FW 510, according to which the oxygen content of the district heating water must not exceed 0.1 mg/l. The press fittings tolerate permanent temperatures up to 150°C and short-term peak temperatures up to 230°C. This makes them ideal for solar thermal systems and district heating pipes with permanent temperatures above 110°C. Thanks to their resistance to oils, greases and fuels, they can also be used safely in industrial applications.
In summary, it can be said that if technically possible, to achieve increased sustainability society should continue to move towards district heating in order to conserve resources and save valuable space, especially in the private sector.