District heating - the promising alternative

District heating – the promising alternative

District heating refers to the supply of heat to the building. The thermal energy generated at a central point is transported to the consumer via a pipe network with the purpose of heating the building, the water and further industrial use. The concept is not new, but it is advisable to take a closer look at the efficiency of district heating in terms of sustainability and resources.

A small digression on terminology. Experts often speak of district heating / local heating, since most of the installations are considered to be “local heating” supplies. The terms are used differently, although the technology behind them is basically the same. Local heating describes smaller networks, district heating larger ones. The Federal Association for Geothermal Energy writes: "Local heating is the transfer of heat through a local heating network between buildings for heating purposes if the heat transfer takes place over relatively short distances compared to district heating (...). There is no legal distinction between local and long-distance heating.” According to the Federal Court of Justice, district heating is when a third party produces heat commercially and distributes it to others. Spatial distance is not taken into account. For the sake of simplicity, the term district heating will be used in the following.

The first generation of district heating was already developed in the 19th century on the basis of steam. At that time, people typically used single fireplaces to heat their buildings. This resulted in a number of disadvantages, such as the constant risk of fire and permanent air pollution from ash. Centralizing heat supply on a larger scale as a result created the first commercial district heating supply in densely populated towns and city centers. This is also the case in Hamburg, where, for example, the town hall was supplied with steam for heating purposes as early as 1894 by a power plant located more than 300 meters away.

In order to minimize 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 characterized by the optimization of control using modern system components, such as a transfer station.

The fourth generation of district heating has been in development for a number of years and some of it has already been installed. Unlike previous generations, it is possible to connect different heat sources to the district heating network at the same time, creating an optimal interaction between energy sources, their distribution and consumption. In many cases, district heating can now also be used to inject renewable energies, such as from solar thermal ground-mounted systems or from other future energy sources, and thus reduce greenhouse gases.

Due to this development and also as a result of the constantly decreasing energy demand thanks to more efficient building materials, district heating has become an important instrument in times of climate change.

In addition to the lower environmental impact, district heating offers numerous advantages over conventional heating, such as greater efficiency in the use of fuel, space savings due to the elimination of fuel storage, high operational reliability, high fire protection and simple operation. Due to these aspects, district heating was able to firmly establish itself as a heat supply in the energy market. According to a study by the BDEW, around 14% of all apartments and around 7% of all residential buildings were supplied with district heating in 2019. 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 further promoted, e.g. via the Combined Heat and Power Act (KWGK).

For the optimal connection of the system components required for district heating in buildings, Conex Bänninger offers the complete solution >B< Press Solar for solar and district heating installations.

Thanks to the patented O-ring contour, the press fittings with green FKM sealing element leak from 0.1 - 6.0 bar and are extremely temperature-resistant when not pressed. 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 of up to 150°C and short-term peak temperatures of up to 230°C. This makes them ideal for thermal solar 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 stated that, if technically possible, society should move further towards district heating in view of sustainability in order to conserve resources and save valuable space, especially in the private sector. Going the other way as well, the concept of long-distance supply is worth exploring further. Because the supply of cooling systems can also be controlled centrally.

Technical contribution by Daniel Schröck

Area Sales Manager