PV on two Swedish buildings

By L Selhagen, NAPS Sweden AB

Building-integrated PV has much to offer, even at northerly latitudes. This article describes PV installations on two different types of building: a commercial buiding in Gothenburg and houses in Kristianstad.

At Gothenburg, the solar arrays include enamel coated steel plates which form
a decorative pattern.

At the head office of Göteborg Energi AB, a PV installation covers a little more than 180m2 of the  building's south façade. The PV system's nominal power is 6.8 kWp. The project was carried out jointly by Göteborg Energi AB and Naps Sweden AB.

Five hundred and seventy 12 Wp modules are mounted on specially-designed aluminium profiles bolted to the façade. This technique allows rapid installation and makes it possible to remove individual modules for easy inspection and replacement. The modules are installed on two separate surfaces and divided into seven sections, each feeding a string-inverter that converts the power produced by the modules to ac-electricity which is fed into the existing building grid.

The thin-film modules, known as 'façade-elements', are a further development of standard amorphous silicon modules. The main changes from the standard design are:

  • The frame is designed to be compatible with the specially-developed  aluminium mounting profile.
  • The lamination technique is changed to one which gives more  technical strength. As the glass pieces normally remain stuck  to this new lamination material, there is considerably less tendency  to shatter on impact, an important safety feature for large PV  façades. The lamination technique also provides significantly  better environmental protection to the thin film solar cell,  thus increasing its service life.

The system is monitored by two separate supervisory systems. The first is a comprehensive data-logging system which measures parameters on both the ac and dc sides on one block of the array. It also measures solar radiation and ambient temperature, as well as solar cell temperatures at three different levels. The total power and energy are also measured. All these data can be accessed remotely, using a special cellular phone. The logging system provides enough data to evaluate the system.

The second supervisory system monitors all the inverters simultaneously and is used by the staff responsible for maintenance and supervision.

The PV system is designed to produce 4.2 kWh/year (ac). An outdoor display, showing the actual power produced, will be installed later.

The modules are installed between aluminium profiles.

The PV façades at Kristianstad.

This site consists of two identical houses with building-integrated PV systems. The façade consists of twenty-nine 100 Wp multi-crystalline modules and the roof has 30 modules. The modules are connected by 10 in series, except the upper string of the façade which has nine modules in series. Each string is connected to an 850 W string-inverter, which gives a total of six inverters for each house. The inverters are installed in the attic.

The façade modules are provided with hook-on structures that are rivited on the module frames. U-profiles are installed on the façade with pre-installed, nylon-covered bolts. The modules are easily hooked onto the bolts at installation. All modules have quick-connectors, to simplify the installation, and a prefabricated earthing wire that is attached by self-tapping screws. The feeder cables to the inverters are installed in the protected area behind the modules. This method allows for quick installation and individual replacement of modules later.

The solar array is integrated in a brick wall and is designed to include the same colours as other façades in the area. The inverters and mains connection board are installed in the attic, just behind the top module.

The roof is a standard folded steel roof. The foundation for the 30 PV modules consists of standard mounting material in galvanised steel. fastened on the folders without holes through the steel sheets. Vertical galvanised steel U-profiles are bolted on the fasteners.

Specially-designed S-profiles are mounted horizontally, bolted to the U-profiles. The modules are then slipped between the S-profiles, five modules to each row. Quick connectors are also used for the roof modules. Individual earthing of these modules is not necessary; the modules are in contact with the S-profiles and earthing wires are attached to each profile.

The site is still under construction and the ends of the array will be covered by red steel work for aesthetical and protective reasons. The bottom and top gaps will be covered by perforated steel plates for bird protection.

The mounting methods for both the façade and the roof provide a gap between the surfaces and modules for efficient air flow, even though high temperatures are not too frequent in Sweden.

For more information contact the CADDET Finnish National Team in Helsinki.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.