Public buildings with photovoltaic systems are showcases for the technology. The institutions are leading by example and generating green electricity. The idea is to encourage members of the public as well as decision-makers in business, local authorities and other public organisations to follow suit. Often, however, these buildings in particular present complex challenges in the planning and installation of solar power systems. For example, the architectural design might not have a uniform roof surface, the building might have higher energy efficiency requirements, or a higher return on investment might be needed for the energy-producing system. These were all factors in the photovoltaic system on the Herman Teirlinck building in Brussels. This is the largest office building in Belgium to be built to Passivhaus standards, and it accommodated 2,400 employees of the Flemish Government. On the roof, a 412.2-kW photovoltaic system with Panasonic HIT® modules generates solar electricity for the offices, a data centre and a restaurant. Linea Trovata, a Belgian specialist in ecological building services and a Panasonic Solar Premium Installer Gold, managed to install a successful solution in a complex situation.

The building, named after the Belgian writer and cultural policy maker Herman Teirlinck, is in the Tour et Taxis site between Brussels Central Station and the port. In a major urban development project, the former industrial site is being redeveloped into a new quarter with offices and homes. The ochre-coloured brick building is an elongated six-storey block on which an office tower with a further eight storeys rests. The building has a net surface area of 46,000 square metres and comprises a publicly accessible part with an atrium, catering outlets, business, exhibition and event spaces, and a wing for the regional government. Designed by Neutelings Riedijk architects, it was completed in 2017.

Maximum sustainability

The client wanted the construction methods to be as sustainable and resource-efficient as possible. As a result, the Herman Teirlinck building not only meets the Belgian Passivhaus standard, but was awarded four stars – the maximum possible – for sustainability according to the “Office Building Valuation” of the Flemish Government. With passive cooling and heating it already achieved E-Level 31. This was improved to E23 by installing the photovoltaic system.

Contributing factors included the compact design with lots of daylight, good thermal insulation, brick façades and recycled materials. Geothermal energy, concrete core cooling and rainwater harvesting are used alongside the photovoltaic system.

It was much more difficult to design and install this photovoltaic system compared to most systems installed on buildings.

Difficult to plan and install

To start with, the roof is complex, with the available surface area restricted by roof domes and technical equipment. This required the modules to be positioned with great care, but also made it harder to plan the cable paths, system monitoring and secure data communication.
Furthermore, the work took place on a government building. That meant strict access checks and complete removal of waste material had to be coordinated. The availability of cranes to lift components onto the roof was also an issue.

There were also high energy-efficiency requirements resulting from energy certification (Energy Performance of Buildings – EPB). Not forgetting the expectations around the return on investment of the equipment, which had to take account of the high electricity consumption in the building. Lots of electrical energy is gobbled up by the offices with modern communication technology, the restaurant and, most importantly, the data centre. The consulting engineers soon realised that the HIT® N325 high-performance modules from Panasonic were the best solution for the difficult and complex requirements. With a module efficiency of 19.7 per cent, these modules use heterojunction technology to produce a higher solar yield than conventional crystalline modules over the same surface area.

What makes the Panasonic heterojunction cells so special is that they combine crystalline technology and thin-film technology. In HIT® solar cells, a thin monocrystalline silicon wafer is surrounded by an ultra-thin amorphous (= thin film) silicon layer.

Crystalline cells can convert more direct sunlight into electricity than thin-film cells can. Thin-film cells, for their part, have better low-light performance and generate more electricity in diffuse light. And their better temperature coefficient means they lose less power than crystalline cells as the temperature increases. HIT® cells combine the benefits of both photovoltaic technologies.

And this was the solution chosen for the Herman Teirlinck building. Two subsystems with a total of 1,268 Panasonic HIT® N325 modules were installed on the roof of the building. 853 modules were set to an angle of 15 degrees. Another 415 modules were installed at an angle of 3 degrees in special substructures for aesthetic reasons. The system is south-west facing. 14 inverters convert the direct current into mains-compatible alternating current.

Following a planning period of four and a half months, the photovoltaic system was installed in three phases within three weeks. Just as planned by the installation contractor Linea Trovata. The system has been running since October 2017, and the forecast solar yield is about 361,000 kilowatt hours per year.

Meanwhile, Linea Trovata has completed its next prestigious project. The company has installed a photovoltaic system on the AZ Sint-Lucas hospital in Bruges, Belgium, with 345 Panasonic HIT® modules with a total power of 112.13 kW. It has been up and running since mid-February.

For more information:

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