Distric heating

Feeding directly into the district heating system of the Austrian city of Graz: The collector fields are mounted on four different hall roofs belonging to the AEVG, a municipal waste disposal company. Photo: S.O.L.I.D. / Oberländer

Front-runners of solar district heating

by Bärbel Epp published in June 2008

The interest in solar district heating and cooling in Europe is increasing. Inthe last two years nine solar thermal installations of this type with more than 1,000 m2 have started operating in Denmark, Austria and Germany. Together with Sweden, these are the major markets in Europe as far as solar thermal district heating is concerned. This article gives an overview over the realised projects. Austria: Graz, the capital of the Austrian state of Steiermark, wants to become thecentre of solar district heating in Europe. Just recently, the city celebrated a first big milestone: the inauguration of a 3,556 m2 solar thermal collector area installed on several different hall roofs belonging to the AEVG, the waste disposal company of the city of Graz (see photo above). The solar heat is fed directly into Graz’s district heating grid. In order to attain optimum levels ofefficiency, the Austrian engineering office S.O.L.I.D. (www.solid.at) delivered high-temperature collectors designed specifically for this application. The so-called Gluatmugl HT collectors are basically available in 3 different sizes between 10.5 and 14.3 m2 gross area. Additionally to the outer high-transmission solar glass, an inner cover consisting of a transparent and high temperature resistantplastic film (Teflon) reduces the convection heat losses. A thicker back insulation (120 mm mineral wool) has also been incorporated to reduce heat losses at high working temperatures between 80 to 120°C. The collectors are manufactured by the Austrian company Ökotech Produktionsgesellschaft für Umwelttechnik m. b. H. (www.oekotech.biz), based in Graz.

The AEVG plants are only the beginning ofa series of solar district heating installations which are planned in the city of Graz. To bring forward this technology the municipal utility Energie Graz founded the consultancy Solar Graz (www.solar-graz.at) together with S.O.L.I.D. and nahwaerme. At Energiecontracting GmbH (www.nahwaerme.at), an energy services provider specialized in renewable energy sources such as biomass and solar energy,as well as in solar cooling. Altogether Energie Graz aims at investing € 6 million in the next three years to realise seven collector fields with a total of 18,000 m2. The plants will be designed, mounted and run by Solar Graz.
Town Investor Supplier of collectors / Type Realisation year Collector 2 area [m ] Volume of the central storage tank [litre] no storage 90,000 Investment 2 costs per mcollector area including pipework 2 [€/m ] 360* Solar yield 2 per m collector area [kWh/ m ] 450
2

Graz (AEVG)

Nahwaerme.at, Austria Nahwaerme.at, Austria Nahwaerme.at, Austria

Ökotech / Gluatmugl HT Ökotech / Gluatmugl Ökotech / Gluatmugl

2008

3,556 *

Gleinstätten

2007

1,315

240

390

Graz / Berlinerring

2007

2,417

60,000

n/a

420

Solar districtheating systems in Austria which started operation in 2007/2008 Source: S.O.L.I.D. * Will be extended to 5,600 m2 collector area in 2008 Denmark In Denmark the latest solar district heating plant started operating in August 2007. A collector area of 8,000 m2 feeds directly into the district heating system of Brænderup (near Horsens on the east coast of Denmark). “We used the existing tank of 2,500m2, therefore we could realise the mounting of the collector area and the pipework at a price of only 217 €/ m2,” says project engineer Knud Nielsen of Arcon Solvarme A/S, which has successfully planned and installed large module areas for central solar heating systems for more than ten years in Denmark and Sweden. Nielson is confident that the system will reach the guaranteed solar yield of...