Building integrated Photovoltaics (BIPV): Solar electric power systems conquer large roofs and façades

by Rolf Hug
07/09/2007

Since the beginning of 2007 photovoltaic records are going from strength to strength: in Brandis near Leipzig (Germany) the world’s largest solar power plant with an output of 40 Megawatt is being built and will be commissioned by 2009, in the Spanish town of Beneixama City Solar AG is working on a 20 MW photovoltaic system that is to be completed in October 2007. These are both ground mounted systems, such as the power plants of "Solarpark Gut Erlasee" (Germany, 12 MW), "Serpa PV Power Plant" in Portugal (11 MW) and the German Solar Park "Pocking" (10MW). International demand for German photovoltaics is on the rise and export figures of manufacturers are continuously increasing. Executive German companies are becoming active abroad and are building large-scale open-space systems in Spain, Greece and even as far afield as Africa.

Megawatt solar roofs implemented mainly in Germany

But also photovoltaics integrated into buildings (BIPV) is aiming for new superlatives: just behind the solar roof complex of Sharp in the Japanese town of Kameyama with an impressive output of 5.1 MW, the list of the largest solar roofs boasts two German photovoltaic roofs in Bürstadt (5 MW on one roof) and Muggensturm (3.9 MW on one roof) in second and third place. Other solar roofs of the Megawatt category can be seen on four factory stores of the private company Franz Fischer in Dingolfing (Bavaria; 3.7 MW) or in the Michelin Solar Park Homburg (Saarland; 3.5 MW). On the roof of the new Trade Fair in Munich an impressive 2.1 MW have been installed, the roofs of the Solar Park Pfersdorf e.G. achieve 2 MW, a logistics centre in Relzow (Mecklenburg-West Pommerania) has 1.5 MW. The discount store LIDL is operating a solar roof with 1.2 MW near Freiburg in Breisgau.

Vertical photovoltaics are also showing a tendency towards larger systems. The Solar Report 6 / 2007 presents some examples of high-output photovoltaic solar roofs, innovative solar power façades and a brief outlook on the future integration of photovoltaics into buildings.

The second largest solar power plant worldwide on a single building
in Baden-Württemberg

On the flat roofs of the logistics company Hartmann AG in the town of Muggensturm the company TAUBER-SOLAR from Tauberbischofsheim installed 80 000 square metres of solar power modules. The photovoltaic system is located in the district of Rastatt, directly next to the A5 Autobahn. The annual solar power output covers the consumption of 900 four-person households. This photovoltaic power plant is currently the third largest system worldwide installed on a building. The almost 30 000 Conergy solar power modules were installed on stands on a flat saddle roof (double-layer steel trapezium profile) with integrated insulation layer and cover a surface corresponding to 16 soccer fields. At a peak performance of 3.84 Megawatt (MWp) the operator expects an annual output of 3.5 million kilowatt hours.

Inverter station weighing 50 tonnes, total investment of 17 million euro

Eight large inverters of the company SMA Technologie AG from Niestetal/district of Kassel (4 x SMA Sunny Central SC500HE, 4 x SMA Sunny Central SC350HE) are located in a double-storey concrete station with a height of 6.8 metres and a weight of over 50 tonnes. These are located next to the buildings and convert the solar direct current into indirect current so that it is compatible with the network. Feed-in is done directly into the medium-voltage network of the municipality of Muggensturm (network operator: eneregio Muggensturm).

The costs of this large-scale solar power plant are estimated by TAUBER SOLAR to amount to approx. 17 million euro. Per kilowatt of peak performance the system price was 4.415 €. Project management was done by the engineering company IBU from Karlsruhe, the installation was done by the company activ solar (Tauberbischofsheim and Friedelsheim/district of Bad Dürkheim) that is now in charge of maintenance of the entire solar power system.

The world’s largest PV system on one single roof in Bürstadt (Hessen)

An overview of all large-scale photovoltaic systems of above 150 kilowatt peak that are installed throughout the world can be found on the Internet under http://www.pvresources.com. This overview also includes the world’s largest system on a single roof that is run by TAUBER SOLAR. The Solarserver presented the solar power plant "Sonnenfleck" in Bürstadt as “Solar System of the Month” in May 2005 under anlagemai2005.html.

Hartmann AG is a logistics company that transports mainly food and frozen products as well as spirits and beverages. The contact with the owner of the roof was established through the Raiffeisenbank Südhardt. The town of Muggensturm with its 6 300 residents and the owner of the roof are proud to have written solar history with this sun roof: some of the trucks of this company are decorated with large sunflowers, and the slogan “Solar power from Muggensturm” is an awareness-raising campaign on their trips through Germany.

Increasing numbers of thin-layer modules on roofs and façades

Cost-effective thin-layer technology is used increasingly in open-space systems, but is also suitable for larger façades. The new PV roof of the Colruyt Group on a factory store in the Belgian town of Halle consists of thin-layer photovoltaic systems and achieves a total output of 330 kilowatt (kWp). This is clearly below the Megawatt line but it is nevertheless the largest system in Belgium. On a wheat silo of the mill “Schapfenmühle” in Ulm the largest CIS photovoltaic system worldwide was integrated into the highest façade and consists of 1 300 modules with a total nominal output of 98 kWp. The new solar façade at the Ferdinand Braun Institute for Hyper-Frequency Engineering in Berlin-Adlershof has a peak output of 39 kilowatt, the modules covering a surface of approx. 640 square metres.

The installation of thin-layer modules directly onto the roofing prevents problems of statics

Currently the largest photovoltaic system of Belgium is located on the roof of a factory store of the discount store Colruyt in Halle in the province of Flemish-Brabant. The Colruyt Group, one of the leading food chains of the country, obtained the thin-layer modules of the “PV Plate” make with a total output of 330 kWp from the Paderborn-based company BIOHAUS PV Handels GmbH.

The bitumen flatroof has a total surface of 12 000 square metres of which three quarters are covered with modules. The company Colruyt is not only attempting to establish a “green” image through the utilisation of renewable energies – the long-term goal of the discount store is to cover their own energy demand to a large extent with regenerative energies. Besides the photovoltaic system, the property in Halle also boasts a wind power station. A 2MW turbine at another location, the participation in a planned wind park in Ypern, as well as investments in offshore wind projects are further proof of the ecological commitment of the company.

Originally Colruyt engineers had even planned a solar power station of about 900 kWp. Sufficient space would have been available for such a system just below the Megawatt line on the neighbouring roof. "Since it’s not yet clear whether this hall will be changed soon, we decided to restrict ourselves to the one roof first,” project engineer Dirk Vandercammen explains in an interview with Photon Magazine (2/2007). The new building that is currently being planned is designed for the inclusion of a large-scale solar power station. This was not the case with the surface areas that have been covered with modules thus far – and that is the reason why thin-layer modules were installed directly onto the roofing, without frames, without covers and without assembly frameworks. “Otherwise we could not have installed the system, because the statics of the roof simply would not have carried the weight,” Vandercammen explains. These special conditions, that exist quite frequently in factory stores, were decisive in Biohaus winning the tender with its PV-Plate modules.

Innovation bonus for PV and construction

The DGS already indicated in its position paper for the hearing of associations in the Federal Ministry of Environmental Affairs that it was open for an optimisation and amendment of future compensation for solar power in terms of the renewable energy law. The association considered it important that future perspectives of photovoltaics be expanded and that no disadvantages would result for local leaders in technology. Building shells were to be discovered and utilised as a “climatically neutral power plant”, the DGS pointed out. To this end the renewable energy law would have to include an innovation bonus for solar technology that forms part of a building shell. In this way the continued growth of the solar sector in Germany as well as the construction industry would be ensured and strengtehened. This will still require some time but would be an investment in our future. “If this protection is offered now, it will have an immediate effect on the national medium-sized businesses and the craft,” the DGS explains.

Exemplary solutions of PV integration

In comparison to optimally positioned modules installed on a roof, solar façades are exposed to less global radiation over the period of a year which results in lower yields. However, specifically designed photovoltaic façades are increasingly being used as architectural element. Solar façades multiply the design options of architects. They are a well visible “promotion” of the utilisation of solar energy and reflect ecological awareness of the construction company. Transparent PV facades also establish contact with the outside world and allow impressive lighting effects in the inside of buildings. Even from an economical point of view, the replacement of conventional façade elements may be of interest, because solar systems not only supply solar energy but also fulfil the tasks of building shells. Thus a photovoltaic façade can replace expensive natural stone tiles or stainless steel elements and can also represent a high prestige value such as these.

The building shell as a decentralised and emission-free electricity supplier in the immediate proximity of the consumer becomes a feasible option if the immense interest in the generation of solar power is combined with well-founded specialised information on archictecturally meaningful integration of photovoltaics. This task was assumed by Dr Ing. Ingo B. Hagemann – and glamourously accomplished. His book “Gebäudeintegrierte Photovoltaik” (Solar Book of the Year 2002) documents an interdisciplinary approach and shows international developments of the integration of solar power systems. Architects, engineers and the construction industry are presented with multiple uses and concepts of photovoltaics in the building industry.

With over a 1000 graphic presentations, tables and photos Hagemann shows integration techniques and documents exemplary building practices that include photovoltaics throughout the world. The 180-page section with photos of PV systems as well as detailed drawings is a reflection of global solar architectural performance. The book shows the different shapes and sizes of solar cells, the fact that modules are available for virtually every roof shape, what façade solutions are feasible and how convincing and aesthetically attractive the integration of solar power systems can be.

The “Solar Book of the Year 2005” also shows new possibilities of an aesthetically sensitive integration of solar power plants; in addition “Solar Design” presents different concepts and modules. Ample examples and illustrations are provided for the retrospective installation of solar power plants in existing constructions, such as old buildings, monuments and existing city spheres. Furthermore, it is shown how possible conflicts between the protection of historical monuments and solar technology can be avoided. Solar Design reports on the results of the German-Italian research projects “PVACCEPT” and proves by way of short descriptions of projects and many photos how solar power plants can be utilised differently and deliberately as design elements in construction.

Solar thermal applications are also ideally suited for integration into buildings. Solar heating façades and roofs covered with thermal solar collectors provide heating for utilisable water and for support of heating when required and thus contribute to an increased autonomy in energy supply.

Further information on photovoltaics integrated into buildings (in german only):

Tübinger Solarstromfassade zeigt Möglichkeiten der Photovoltaikintegration.

Denkmalintegrierte Solaranlagen: Kompromisse statt Kontroversen.
Solarfassaden: Sonnenenergienutzung in der Senkrechten.

Solarstrom-Weltrekord auf einem Dach: Der "Sonnenfleck".
Neues Biohaus-Domizil: perfekte Photovoltaik-Integration im Nullenergiehaus.