Integration of Solar Thermal Energy in an Existing DH System
The restructuring of Vattenfall’s thermal business in the Germany’s capital city is progressing
steadily. In Berlin by 2030 at the latest, the coal is to be eliminated. Gunther Müller, Berliner
Vattenfall Heat CEO, explains the significance of the project: “The primary goal of Vattenfall is
to be CO2-free within a single generation. For our business in Berlin, this means generating
and supplying heat without emitting greenhouse gases. To do this, we are transforming our
entire portfolio of facilities into sustainable energy sources, becoming more digital and
decentralized. The lignite withdrawal in May 2017 was a giant step on this path – now comes
the hard coal. With the feasibility study, Vattenfall and the State of Berlin are working together
to develop the timetable so that by 2030 the last coal-fired plant can go offline.”
Also other projects, such as the project “Urbane Wärmewende” (urban heat energy transition)
support Berlin’s ambition to pursue an urban heat supply that is environmentally and socially
compatible, and smartly interconnected with other infrastructures and resilient. These
initiatives and targets contributed to Vattenfall’s decision for upgrading its DH system in BerlinKöpenick with solar thermal collectors, hence increasing the share of renewable energies and
reducing the need for combustion fuels.
Vattenfall wanted to find the best solution to cope with the challenges of a CO2-free future.
Therefore in 2014, Vattenfalls’ employees were asked to develop ideas and options for
transforming the heat-generation systems. The most reasonable idea was to upgrade the
cogeneration plant with additional solar thermal plants. Then, this idea was well discussed
within the company and it was decided to initiate a first pilot project.
Fortunately, at the same time Vattenfall’s island networks were investigated to improve their
primary energy factor. In this context, unused area of the company were investigated as well.
Hence, it was possible to name a precise area and district heating network for the solar thermal
The next step was the feasibility study. For this project two feasibility studies were carried out.
The first shows the feasibility of the technical implementation of the solar thermal plant in the
existing network, but pointed out unprofitable economic characteristics. Only with a second
more detailed study and a precise offer from the Danish solar plant supplier Arcon Sunmark,
the economic feasibility was achieved.
With these results, the pilot project was further elaborated, subsidies were requested from the
German KfW Group and internal approvals were enquired. Compared to other project
procedure steps, this took very much time. After the project was approved, the period between
the groundbreaking ceremony and the placing into operation was just ten weeks.