Solar District Heating in Graz – an example for Europe
Further development potential is hugem


Pressefoto SDHtake-off/Fa. S.O.L.I.D.On March 16 and 17, 2011, a Solar District Heating Workshop and Plant Visit Tour took place in Graz. The workshop’s objective is the facilitation of the development of new Solar District Heating plants in towns and villages, focusing on Southern and Eastern European ‘newcomer countries’.

  Left to right:.: Dipl.-Ing. Wolfgang Malik , Dr. Christian Holter,  Mag.a. Barbara Muhr,
 Siegfried Schrittwieser Landeshauptmannstellvertreter,
 Lisa Rücker Bürgermeisterstellvertreterin, Dipl.Ing. Dr. Rudolf Steiner


Participants of the discussion with the press
Jan Erik Nielsen, Denmark, Chair of working group on large solar thermal systems of the International Energy Agency
Siegfried Schrittwieser, Vice Governor of Styria, lead for renewable energy
Lisa Rücker, Vice Mayor of City of Graz, lead for environment
Christian Holter, CEO, SOLID Gmbh


Jan Erik Nielsen, Chair of the working group on large solar thermal systems of the International Energy Agency stated at this event:
„Solar thermal systems are competitive with cogeneration power plants. In Denmark, suppliers to the district heating have to reduce their primary energy demand significantly. Hence, solar thermal systems with a size of 74,000 m² (51,800 kW thermal) have been built in Denmark in 2010; for 2011 another 100,000 m² (70,000 kW thermal) will be constructed.”


The Vice Governor of Styria, Mr. Schrittwieser affirmed:
„As member of the government of Styria responsible for renewable energy I am very happy that the organizers of the “Solar District Heating” event lead participants from 20 nations to the Water Works in Graz-Andritz. Styria can be proud to be a leader in solar thermal heating in Europe, which is based on a good working relationship between science, energy utilities and the companies involved. Especially for the development of solar thermal plants for district heating exists a high potential. It’s a great challenge for me, to be responsible for renewable energy and climate change mitigation. In the framework of the EU Climate and Energy Package, in which Austria agreed to increase the share of new renewable energy in its portfolio to 34% by 2020 (currently the Province of Styria has around 25%), and to reduce its greenhouse gas emissions by 16% by 2020, and the energy strategy of Styria for 2025 and the climate protection plan of Styria we will put everything in place to support the development of renewable energies in Styria.
While preparing the budget we achieved a slight increase of funds for renewable energies.

It is my dedicated goal, to care for a broader dissemination of climate friendly energy plants, also to avoid the risk technologies in the future. Presently the frightening catastrophe in Japan should teach us a lesson. I hope that it will lead to a further awareness creation within the public and will prepare the ground for a safe, affordable, socially responsible and further also environment friendly energy supply.”


Rücker, the Vice Mayor of Graz, declared:
“Days like these show us the importance of development and support of alternative energy. Together we can achieve to supply the district heating network in Graz with 50% solar energy during summer time. We have to pursue this goal consequently. Not only since last week people see it as relevant where the energy for their warm homes comes from.”


Dr. Holter – CEO of S.O.L.I.D. Gesellschaft für Solarinstallation und Design mbH said:
„Styria has an excellent knowledge and well worth seeing solar thermal plants. Meanwhile the solar thermal technology became an important export product.
The technical perspectives for solar heat are good: a feasibility study from Energy Graz contracted to SOLID three years ago shows that during summer time the energy demand of the district heating in Graz could be supplied fully by 50% from solar thermal plants and 50% from waste energy from industrial processes. This level would need a solar thermal collector area of approximately 80.000 m² which is easily available on the roofs of Graz. “
Further background information:

In many district heating networks the heat demand for hot water during summer time has been and is still being produced by cogeneration plants fired by natural gas. This operation is often no longer economic viable, as for instance ESTAG declared in its financial statement of 2009:


Quotation from ESTAG financial statement 2009, status report, page 51:“
In the district heating power plant Graz no power has been produced due to the price situation of natural gas, electricity and CO2 certificates. Extremely low electricity prices lead to an operation of the decentralized cogeneration plant mainly at peak times only.”

Without the operation of the cogeneration plants there is also no heat available, which then in turn has to be generated expensively in pure (gas) boilers. This lead to a boom of large solar thermal system in Denmark. In view of the power generation structures in Europe the operation of cogeneration during summertime makes less and less sense. Solar heat is a affordable and environment friendly alternative. The International Energy Agency has established a task group on the topic of large solar thermal systems. (Jan Erik Nielsen)

During summertime the district heating network of Graz is supplied by 70% from gas fired heating plants and 30% industrial waste heat. An analysis from 2007 by SOLID together with Energie Graz shows, that a 50/50 scenario with industrial waste heat and solar thermal heat is possible.
This would require a solar collector area of around 80.000m², as buffer storage to balance the solar radiation during daytime against the demand around the clock the district heating network with a volume of around 15,000 m³ could be used. (Lisa Rücker)

Just now where the Climate and Energy Fund of Austria has started a new program for advancing the feed in of solar heat, new projects have the best chances. Styria has envisaged a massive development of solar thermal energy in its Energy Strategy 2025. This cannot be limited to individual homes only. Many buildings in the central areas of Graz are not suited for solar thermal systems due to their orientation, protected status or technical limitations. Large scale solar thermal projects spread over the district heating grid could be a solution. (Siegfried Schrittwieser)

Opening of the international workshop on Solar District Heating


On March 16 and 17, 2011, a Solar District Heating Workshop and Plant Visit Tour took place in Graz. The workshop’s objective is the facilitation of the development of new Solar District Heating plants in towns and villages, focusing on Southern and Eastern European ‘newcomer countries’. The workshop has been organized by S.O.L.I.D. GmbH, Energie Graz GmbH & Co KG, and the European Heat & Power organization.

The event was opened by the Vice Governor of Styria Siegfried Schrittwieser and the Vice Mayor of Graz Lisa Rücker.


Over 90 registered participants from 20 countries from Europe, Korea, Israel and the Middle East followed the invitation. The participants were coming from district heating operators from Norway to Spain, district heating associations from Germany to Czech Republic, and officials from the EC, governments, ministries and development funds.


Besides the technical and economical experiences and knowledge to be shared, the interest of the participants focused on the many successful implemented projects in Styria. A field excursion lead to the first solar district heating in Eibiswald, Styria. The plant was constructed in 1997 and the solar energy from the collector field of 1246 m² is fed into the local heating network powered by biomass otherwise. It thus reduces inefficiencies of a low-load operation of the biomass boilers during summertime.


Further projects in the city of Graz have been visited. Graz as a middle sized town so far is the only one with 13,000 m² collector area installed, which supports the district heating during the warm period and thus reduces the consumption of fossil energy – mainly natural gas.

The solar installations at the site “Berliner Ring” still count as the biggest solar thermal system constructed during refurbishment of multifamily housing in Europe.

Further the plants at the water works in Andritz right at the workshop location had been visited and studied closely.



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