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Heat storage tanks in heating networks

In heat supply systems, many benefits can be achieved by using thermal energy storage. Their use often reduces investment in the peak load area, increases efficiency and utilisation rates and reduces operating costs. For example, the connection and disconnection to a generator can be avoided meaning that start-up losses are reduced and operating times increase. The operation at optimal operating points reduces consumption and wear. By way of the temporal decoupling from the excess heat and grid load, the supply system becomes more flexible. CHP plants can sometimes be decoupled from the district heating demand by way of the intermediate storage of heat and can be operated based on the electricity price.

A considerable benefit of thermal storage tanks is that several energy sources, e. g. solar thermal energy, heat from combined heat and power generation and biomass, can also be well integrated. Above all, the option of integrating renewable energy sources improves the primary energy factor of the total heat supply system. With an increasing share of power generation from renewable energies, the significance of heat storage in CHP plants grows.

Due to the versatile use, in recent years numerous heat storage tanks have been installed in district heating systems. In this sector, a demand beyond the requirements of the German Combined Heat and Power Generation Act (KWKG) can be observed. In Germany, the capacity of large heat storage tanks more than doubled between 2012 and 2016 from 8 GWhth to 20 GWhth. A research project (project number 03ET1188A) estimates a potential of approx. 88 GWhth for a Germany-wide expansion of the district heating supply. The researchers investigated the conditions under which investments in the construction of thermal storage and power-to-heat systems are economically viable, and which improvements would result from the environmental policy perspective. The project was carried out at the Technical University of Berlin in cooperation with the University of Applied Sciences and Arts Hanover, Leipzig University and with consultancy provided by industrial partners.

Classic district heating networks are often operated at temperatures of over 100 °C. Here, predominately slimline pressure vessel constructions or so-called two zone storage tanks are used. Many heat suppliers want to achieve lower supply temperatures due to the respective high thermal losses. The OBSERW project considered this tendency because the storage tank is designed for secondary networks. Other trends are the decentralisation of energy generation as well as the integration in the district concept. This type of storage tank can also be used for these purposes.

Projektinfo 10/2018:
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Addresses

Practice-based development and demonstration
farmatic tank systems

Coordination/scientific support
TU Chemnitz, Fakultät für Maschinenbau

Scientific support
Universität Stuttgart, IGTE

Service

BINE-Projektinfo 10/2018
(PDF, 4 pages, 242 kB)

Links

OBSERW
Project site of the research partner (in German)

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