Intelligent building façade generates energy

The name given to such systems is a little cumbersome: building-integrated photovoltaics (BIPV). It refers to building façades that can do more than simply house windows. Solar panels convert incoming sunlight into electrical energy. And BIPV façades offer a great deal more additional application options: they can be used, for example, for heat or sound insulation or as a means of light control.

Nevertheless, the technology is not yet very widespread. Objections with respect to aesthetics, in particular, often prevent use in upcoming façade renovations.

A variety of opportunities for building owners and architects

Emmanuel Rey, a professor at the ETH in Lausanne, opines that this technology is only implemented at an insufficient level in Switzerland. If the façades worked upon as part of renovation projects were upgraded with BIPV, this could represent an important step in the implementation of the Energy Strategy 2050. With this new technology for the integration of photovoltaic systems in buildings, building owners and architects now have a broad range of options for combining architectural quality with the necessity for sustainable energy generation.

In contrast to solar systems on roofs, calculations with respect to the use of BIPV are more complicated. The researchers therefore propose already initiating the integration of BIPV in an early project phase. In parallel to this, they also recommend making 3D city maps available to the architects and planners. Within this model, both solar radiation and the vegetation in the surrounding area, among other things, would be taken into account. Such parameters would make it possible to better identify the strategically optimal locations for photovoltaic systems.

The expenditure pays off

A study in Neuchâtel has shown how various renovation projects with BIPV perform in practice. On the basis of this medium-sized Swiss city, Rey and his researchers examined five buildings to ascertain the impact of BIPV in reality. To do so, he looked at buildings of various ages to which three different renovation models had been applied: ranging from a soft BIPV renovation strategy with the objective of maintaining the building’s expression and at the same time improving its energy to a BIPV renovation project implemented in accordance with the principles of the 2000-watt society and the requirements stipulated under the Energy Strategy 2050. The third renovation strategy lay between these two extreme variants.

If you are going to renovate, do it properly

Although the initial investments for renovation projects with BIPV are higher than the costs for a renovation without a PV system, the effort is worthwhile when viewed over the long term. The amortisation period for both non-renewable primary energy emissions and greenhouse gas emissions is significantly shorter than the expected useful life of a building-integrated photovoltaic system. The reasons for this include lower energy costs and tax incentives for BIPV renovations.

The researchers also anticipate that the costs for BIPV renovation projects will fall over the coming years. Viewed from this perspective, these renovations not only make an efficient contribution to the achievement of environmental objectives, but rather will also in future pay dividends from a financial viewpoint.

Sophisticated city model

For the study in Neuchâtel, the team headed by Emmanuel Rey applied a sophisticated 3D city model. It contains all of the data relevant for renovation projects with BIPV. A tool such as this for the whole of Switzerland would represent an important step towards achieving the goals of the Energy Strategy 2050.