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Customer application 28 August 2020

Modernizing with Vision

The modular WAGO-I/O-SYSTEM and the WTG Protocol Converter enable easy management of the complex district heating system in Greifswald.

Greifswald relies on district heating. Almost 20,000 residents – about 70 % of the population – use it for heating and for hot water, which is an astonishing statistic in comparison to the national average of 14 %. The first thermal plant went online in 1958, and more have been added over time. Starting in 1983, one of the two nuclear plants in the GDR supplied the city with both waste heat and electricity. Up until 1990, a district heating line extended 24 kilometers between the Lubmin nuclear plant and Greifswald.

The end of the GDR sealed the fate of the nuclear reactor. Serious safety infractions were revealed, and conforming to FRG standards would have been prohibitively expensive. In 1990, the power plant was taken off line, and the aboveground supply line was dismantled four years later. From 1990 to 1993, an oil heating plant at the Lubmin location temporarily supplied Greifswald with district heat.

Following the shutdown of the nuclear plant, Greifswald maintained its district heating and established Fernwärme Greifswald GmbH in 1991 to supply it. This entity introduced a new energy concept: Downtown pipeline systems were renovated, and four new power plants were built in just five years. Three CHPs with internal combustion engine systems, and one thermal plant with a gas turbine engine and waste heat boiler, now supply thermal energy and electrical power. Electricity is generated exclusively by the high-efficiency CHPs located within the city limits.

Managing district heating systems – here’s how WAGO supports you:

The WAGO-I/O-SYSTEM 750 combines the functions of a telecontrol station and data concentrator in one system.
The telecontrol gateway records data from the heat regulators in the transfer station via serial channels.
New elements are added via FTP and Web-Based Management.

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Highly Efficient Power–Heat Coupling

The complex district heating network requires an intelligent management system for efficient operation and for the (highly unlikely, yet conceivable) possibility of accidents or disruptions. Therefore, the two generating plants that are responsible for the central network are linked together thermally by a network coupling station in the city center. This is where heat is transferred between the two primary networks. Since the maximum supply temperatures and the pressure are different for historical reasons, the coupling initially takes place via a heat exchanger.

To guarantee an efficient and error-free supply, the transmission of the amounts of heat is automated. The outside temperature is detected, and the supply temperature is automatically adjusted to the level necessary for heating demands. This turns district heating into heating energy for private consumption with demand-based control.

When their previous telecontrol hardware was discontinued, the Greifswald municipal utility decided to replace both of the components in the telecontrol station and the data concentrator with WAGO solutions. The WAGO-I/O-SYSTEM 750, with its find-grained modularity and fieldbus-independence, has been used since October 2016. Greifswald is unusual in that a WTG Telecontrol Gateway is integrated as an application for the I/O system. Whereas the modules previously operated as a telecontrol station or data concentrator required an individual interface to the network control station, this is now accomplished through a common bidirectional interface.