The best of both worlds: combining building shells and energy production

The federal government’s energy strategy states that 20 % of Switzerland’s energy requirements should be covered by photovoltaics by 2050. This objective is ambitious given the currently small share accounted for by solar electricity: this figure grew from basically nothing to 2.2 % between 1990 and 2016. How can the goal of generating 20 % of energy from photovoltaics by 2050 be achieved?

This question is being address by the joint project “Active interfaces”. Its work is based on the knowledge that equipping roofs on new buildings with photovoltaic modules alone will not be enough to meet the ambitious target stipulated under Energy Strategy 2050. The roofs and facades of existing buildings must also be used to generate energy from sunlight.

Holistic approach

“Active interfaces” has therefore set itself the objective of investigating photovoltaic modules integrated in the building envelope, for example in the form of roof tiles or facade elements. Combining the outer envelope of buildings with electricity production simultaneously meets two requirements of the energy turnaround: the saving of energy through energetically insulating materials for the building envelope and the generation of energy through photovoltaics.

As obvious as this approach sounds, the innovative construction elements pose developers as well as architects, legislators and building owners with a range of challenges due to their double function. The project “Active interfaces” therefore adopts a holistic approach. This is because it is not sufficient to develop roof tiles that can produce solar electricity but which do not meet an architect’s aesthetic requirements. The sub-projects of the joint project are investigating a total of five questions: • Technology: which technological hurdles have to be overcome in order for building-integrated photovoltaics (BiPV) to succeed? • Design: which architectural design strategies will allow for the use of BiPV in urban renovation projects? • Socioeconomics: what are the requirements of consumers and investors with respect to BiPV? • Assessment: how can standards and certification processes for BiPV be simplified by the legislators? • Distribution: which platforms (websites, conferences, workshops) are needed to promote the acceptance and distribution of BiPV?

Specific renovation projects

In order to obtain practice-relevant knowledge, “Active interfaces” is testing its approaches with very specific renovation projects. Successes have been recorded in several sub-projects, for example in a study in Neuchâtel. Here, researchers from the Swiss Federal Institute of Technology Lausanne (EPFL) showed that BiPV can be used during the renovation of facades of buildings of different ages.

The joint project is providing importing findings for the future use of BiPV in various areas:

• Buildings: combining the building envelope and electricity generation reduces the consumption of fossil energies as well as greenhouse gas emissions. At the same time, building owners save on materials and electricity costs.
• Financial attractiveness: although the initial investments for renovation projects with BiPV are higher than the costs for a conventional renovation, the effort is worthwhile when viewed over the long term. The amortisation period is shorter than the expected service life of a BiPV system.
• Market conditions and regulation: in 2014, the cantons agreed on new standards in the area of energy legislation for buildings (as part of the fourth revision of the model provisions of the cantons in the energy sector (MuKEn)). It will only be possible to significantly improve the distribution of BiPV if the MuKEn are appropriately implemented by the cantons.
• Acceptance: a survey shows that building owners have a positive attitude when it comes to BiPV. Of the 500 surveyed building owners, 85 % were not put off by the greater initial costs in light of the long-term benefits.
• Reduction of complexity: simpler solutions are required in order to make BiPV more attractive for building owners and investors. For example, only when suppliers are able to offer “ready-to-use” solar roofs as part of renovation projects will the technology enjoy greater distribution.

Despite all of the positive findings: there is still a great deal of work for all stakeholders. Legislators, architects, building owners and technology providers must work together hand in hand in order to quickly conquer the new field of BiPV. All information on the joint project can be found at www.activeinterfaces.ch.