Vidursolar FAQ

What is BIPV?

Building Integrated Photovoltaic (BIPV) can replace conventional building façade materials with photovoltaic (PV) architectural elements to generate energy. Photovoltaic (PV) solar technology generates energy from the outset without any requirement for an external source of fuel. By integrating Vidursolar PV modules on a large scale in an urban environment, maximum use can be made of its unique characteristics for renewable technology. These factors, combined with a high degree of modular flexibility, ensure that (PV) panels are "a technology of the future”. Their electrical generation capacity meets the challenges for our era of sustainable integrated building.

What are the benefits of applying BIPV?

There are many benefits of using the BIPV concept: Multifunctional façades by adding an electricity generating capability to the traditional functions of a building envelope. Solar protection and reduction of the solar factor (g-value) which result in a significant reduction in the thermal gain of buildings with resultant savings in air conditioning costs. A replacement of traditional construction methods for both the building façade and sunshading elements. Unlike conventional building materials the VIDURSOLAR PV-modules will provide a payback of the investment in the medium to long term. Since they are “economically active” the return upon investment will in most cases be significantly shorter than its lifespan. Creation of a new corporate image demonstrating innovation, ecology and sustainability with an abundance of options for creative, modern and challenging architectural design. An increased building value by virtue of a financially contributing construction element. This attribute has a strong influence upon energy conservation certification as the building’s CO2 footprint is assessed under energy qualification schemes (BREEAM, LEED, German Energy Pass, etc.)

Where can I integrate VIDURSOLAR glass-glass PV modules?

The special characteristics of VIDURSOLAR glass-glass PV modules permit their use in a wide range of applications, whilst combining stylish aesthetics and functionality for typical applications in:
  • Cladding – ventilated façades and curtain walling
  • Atriums, skylights, pergolas and conservatories
  • Sunscreen elements – Brise soleils
  • Balconies and balustrades
  • Installations of an artistic and decorative nature

What different types of photovoltaic modules exist and which ones are suitable for BIPV installations ?

There are differing types of photovoltaic modules in the market, but not all of them are suitable for BIPV installation. The well-known standard PV-modules are composed of a thin exterior glass and a plastic (called tedlar) on the reverse side. These modules are optimised to produce the maximum energy per square metre at the lowest cost. They are primarily used where the single objective is energy generation. These modules can be modified using a translucent tedlar on the inner leaf to create limited light transmission. However the “glass-tedlar” modules are not suitable for BIPV installations due to their low strength and impact resistance. The glass-glass PV modules consist of a laminate of two panes of glass. These PV modules offer important advantages in terms of safety, transparency and aesthetics are therefore the glass-glass PV-modules are used for BIPV. In the production of glass-glass PV-modules differing materials can be used to laminate the glass (called encapsulants): EVA or PVB (Polyvinylbutyle). PVB is the material used traditionally in safety glazing due to its superior tensile strength and resistance to breakage. EVA is mainly used to laminate the standard ‘thin glass-tedlar’ modules as it is simpler to work with. Its disadvantages are the significantly lower resistance to breakage and thereby a reduced safety aspect. In some countries the use of PVB is mandatory for this reason. BIPV requires glass-glass PV-modules that offer the highest quality standards in terms of safety and therefore VIDURSOLAR PV-modules are only laminated with PVB in accordance with standard safety glazing units (see also chapter 7.)

What are the main differences between crystalline and thin film PV technology?

To provide the maximum range of flexibility in module design, crystalline cells are used allowing varying grades of transparency to be achieved. The crystalline cells are available in different colours and power levels. It is possible to use ‘thin film’ technology, as opaque or semi-transparent surfaces since they have a significantly lower investment cost but power per square-metre is also significantly less than that gained with crystalline cells. Thin film PV technology lacks flexibility in design. In aesthetic terms the two technologies are very different with thin-film-technology generally a homogenous black (depending on the angle of solar radiation this may have a hint of red and brown) colour. It is usually the desire of the designer that decides the technology to apply.

Does PV technology affect health?

The silicon PV technologies used by VidurSolar (crystalline or amorphous) use materials that are completely non hazardous with silica being the world’s most abundant mineral. PV modules produce DC power from which there are no adverse affects upon health resultant from the effects of high-frequency or associated electromagnetic fields and radiation. Energetic aspects of BIPV

How can an optimum energy output be achieved?

The optimum electricity production will be achieved if the PV-modules are directly aligned at a perfect angle to the sun to maximise annual energy generation. Shadowing should be avoided as far as possible since even small shadows can have a significantly negative effect. On modules with good rear ventilation the energy production will be better as extreme module temperatures result in a reduction of the efficiency of the cell. In BIPV-projects it is difficult to secure optimum conditions for electricity generation as the integration of PV will be a compromise between aesthetics, functionality and energy production. Therefore in most installations it is necessary to calculate the negative impact of reductions due to imperfect orientation, inclination or high cell temperatures. The performance of BIPV installation cannot be measured by its energy output alone. As a general rule it is considered that an acceptable level of reductions from the optimum output is no more than 50% in a BIPV installation. Fig 1 below indicates the percentage of PV energy produced for different orientations and inclinations in comparison with the ideal is shown for central Europe (ideal inclination approx. 40º, orientation South). East and West façades have similar values. Losses of efficiency due to shading effects need to be taken into account separately. Small shadows can have a large influence and if these cannot be avoided additional losses must be checked and evaluated by a competent PV engineering company.

What is the relationship between PV-power and the transparency of a glass-glass PV-module?

The nominal power that can be obtained in a glass-glass PV module is dependant upon the level of transparency i.e. the distance between PV cells in the module. The following table shows the relationship between transparency and approximate PV-power. The g-value is indicated is an important parameter for designers to calculate the solar energy gain to the interior of the building and this also shows the level of solar reflection provided by the PV-module.

What are the most important safety requirements for glass-glass PV-modules?

With PV it is common to make comparisons with standard glass-foil panels used for generating energy but the performance of a PV-module and its safety requirements must be considered differently according to its application. PV modules used in BIPV-projects perform several functions in addition to the energy production they are are designed for. A BIPV-module is an integral component of the building façade offering the same security and functions as traditional construction cladding. They must comply with the criteria applicable to curtain walling and cladding in relation to impact, detachment and dynamic/static loads whether used as façades, glazed roofs or pergolas. VIDURSOLAR glass-glass PV modules have been designed to comply with the highest quality and performance standards. The main features and key-point differences to integrate PV-modules in the building façade are: PV-modules must provide adequate resistance against breakage and therefore both panes in the glass-glass PV-modules are made from tempered glass. The glass thickness is designed according to the performance criteria of the project, fixing centres and the construction method proposed. The PV-module must comply with the EU-norm for Safety Glazing units and have been tested accordingly with certification provided by the supplier. As a security guarantee a CE-marking according to EN 14449:2005 shall apply. PV-modules must meet the strictest requirements of breaking strength and integrity. Therefore, in some countries only materials with the highest performance parameters are allowed to be used for laminated safety glass. In France and Germany, only PVB (polyvinylbutyle) can be used as the laminating material for these applications. PVB has been widely used in laminated safety glass applications (construction, automotive sector for wind-screens, etc.) due to its excellent resistance against breaking. A minimum tensile strength of 22N/mm2 assures excellent security in overhead glazing units as well as for glazing units that are mounted on façades. There should be a stated requirement for glass-glass PV modules to be manufactured with PVB as the encapsulant (laminating material) to achieve this tensile strength.

What are the advantages of PVB in comparison with other encapsulation materials?

There are three types of laminating material identified as: PVB - Polyvinylbutyl, EVA – Ethylenevinylacetate and resins. The main advantages of PVB are the following: High tensile strength at a minimum breaking strength 22 N/mm2. In comparison, EVA will only provide 14 N/mm2 and then only if it cured under a special process. Resins may have a lower performance (no data available). Reduced elongation at a breaking strength of approx 300% ensures that the glass compound is securely bound. In the case of EVA the elongation is more than 1000% with the result that the glass compound is easily deformed when under stress. Long-term performance: good durability of the laminate in terms of transparency, resistance against delamination and prevention of detachment. These are the important advantages of PVB as they guarantee the safety requirements in buildings. EVA is used basically for standard glass-tedlar PV-modules for its good performance in contact with moisture (as the tedlar back-sheet is not resistant to humidity) and its ease of storage and handling during fabrication.

What are the major advantages of VIDURSOLAR glass-glass PV modules?

Quality and experience: VIDURSOLAR is part of a group of companies with more than 45 years experience in glass processing for construction-architecture (façades-interior), automotive and industrial applications. This expertise, developed and proven technologies and production facilities ensures the highest flexibility and quality of VIDURSOLAR PV-modules with: Production with quality control certified according to ISO 9001. Specially tempered safety glass for both sides of the module Laminated safety glass with PVB tested according to EN 14449. Flexibility: VIDURSOLAR offers diversity in a wide range of potential uses of which the following are the most important: Differing dimensions and shapes: up to 4 m2 – modules; circular, triangular and trapezoidal shapes to fit perfectly into the architectural aesthetic. Different Colours: Translucent colours of PVB (blue, green, yellow, violet, red etc.) and opaque colours on the rear face of the glass are possible. Different types of cells: different coloured cells and different power levels are available, even perforated cells for improved consistency of light transmission. Different connection types: Rear side junction box or edge terminals that are designed to hide the cabling inside the support structure. Different fixing methods: Holes for point fixing, other preparation for various fixing systems are possible. The facility to combine screen-printed surfaces and PV-cells in the same module or to have screen-printed designs on the inner pane of the module. Double/triple glazed units can be produced with the PV-laminate.

What is the expected life of a BIPV module?

VIDURSOLAR glass-glass PV modules are produced with the same process and type of glass as conventional safety glazing units using materials and manufacturing systems proven over decades to meet the highest levels of quality. The PV cells used are the same as for standard PV modules. Therefore the expected life of the VIDURSOLAR glass-glass PV-modules is at least the same as for standard PV modules. International experts assess that the PV-cells should function for 35 years or more but there are no older PV-modules in existence to verify this. There is a minor loss in power during the lifetime of the cell and hence the standard power warranty does not exceed 20 years. This matches the duration of most feed-in-tariff-schemes which are usually for a minimum of 20 years (25 years in Spain for example).

What is the investment cost level for a BIPV installation?

The cost of a BIPV installation cannot be compared with that of a standard ‘thin film’ PV system as the latter is specifically designed for energy generation as its sole function. A BIPV installation offers a range of other benefits (see point 2) such as aesthetics, corporate identity and function as a façade. The performance criteria and design flexibility of BIPV modules result in higher initial build costs than for standard ‘thin film’ installations in a range from 1.5 to 3 times the price. In a BIPV installation conventional construction elements are being replaced and therefore in the payback calculations of BIPV projects the differential cost of glass-glass PV-modules and the conventional alternative has to be calculated: BIPV Investment = glass-glass PV elements less replaced materials plus the additional electrical equipment and installation. Replaced materials are mainly the alternative glazing units and the sunscreen provisions. These can be significant as they can be adapted to the performance of any building to reduce its thermal gain and air conditioning requirements. Investment for the mounting structure and module installation are no more than for a conventional façade and in many cases the extra cost of engineering is very low if the BIPV project is part of the initial building project.

What is it the payback period for a BIPV installation?

What is the payback upon a conventional façade? None. What is the payback upon a polished stone façade or another exclusive material? None, and the initial build cost can be similar to PV. The importance of this is related to perception of the client and his appreciation of the best solution. There are benefits that cannot be quantified but are nevertheless important in an overall scheme. Obviously, a payback period can be calculated for a BIPV installation but it should not be the main factor for selection. The period depends on several factors because the influence of location, hours of sunshine and temperature, the orientation of the PV elements, shading and statutory regulations for PV application in each country vary. In many countries a special feed-in-tariff for PV electricity is established, but also other incentives can be available as fiscal grants, subsidies, etc. Due to these factors, the payback period usually is in wide range and it is difficult to give hard and fast values and every project requires to be calculated individually.

Can investment costs for a BIPV installation and a conventional roof panel PV system be compared?

Glass-glass PV modules are a more sophisticated production process, and therefore more expensive than a standard glass-tedlar PV modules (see chapter 4). These are not suitable for the replacing alternative construction products and extra costs apply for the support structure. These costs are already included if the PV module are being fixed within curtain wall units. The installation cost between a BIPV (calculated according chapter 11) and a conventional roof panel PV system will therefore not be greatly different. As indicated previously in chapter 11, the real value of a BIPV installation is not always easy to quantify (aesthetics, image,…). The comparison between BIPV and conventional installations or modules is not really valid.

What is the payback period for BIPV installations with thin film technology?

In chapter 5 the basic features of thin-film technology has been explained. If we refer to the payback of a ‘thin-film’ PV installation the same arguments as in chapter 12 are valid. The rumour that a ‘thin film’ PV installation gives a better payback is not normally true. This is based on the lower initial cost per power unit (Wp) of standard opaque thin-film modules. For a BIPV installation the use of opaque thin-film PV modules for façade cladding or as parapets or screens may result in a better payback than with crystalline modules. But, when a specific transparency is needed the payback of a semi-transparent ‘thin-film’ PV installation is similar to the crystalline modules and the payback period might even be longer.

How can VIDURSOLAR glass-glass PV modules be installed?

The installation of VIDURSOLAR glass-glass PV modules is the same as that of a standard laminated glass with the same mounting standards and regulations applicable. Care must be taken in the handling as the breakage of a PV-glass is much more costly than for conventional glass. Installation by an experienced installer is always recommended. The electrical connection for BIPV modules is the main difference with that of a normal glazing unit. In the case of the electrical junction box being placed on the rear face of the module the electrical connection is independent of the mounting of the glass. The electrician can undertake the connection of the modules after their installation. In the case of an electrical junction box on the edge of the module (edge connector or terminal) the cabling must be co-ordinated with the glass installer as the terminal and cables are carried inside glazing support profiles. The latter option is most important from the aesthetic perspective with no cabling visible.

Do VIDURSOLAR glass-glass PV modules need any kind of special support structure?

VIDURSOLAR glass-glass PV modules can be installed using standard façade systems for curtain walls or standard fixing systems for glass cladding elements. Also point fixing elements (spider-type) can be used as VIDURSOLAR glass-glass PV-modules can be prepared with holes for point fixing. The same regulations and technical standards apply as for traditional glazed façades, roofs or skylights. VIDURSOLAR can assist in finding a suitable mounting system for a broad range of applications and will provide technical recommendations for module installation according to the application.

In the case of creating holes for in the glass for point fixing, what factors have to be taken into account?

For the mounting of tempered glass the following basic criteria applies:

  • The diameter of the hole and the minimum distance between hole and the edge of the glass must be larher than the thickness of the glass.
  • The distance between holes must be 1,5 x the thickness of the glass.
  • The distance between hole and a corner must be 4 x the thickness of the glass.
  • If the fixing method prevents the ingress of any moisture to the interlayer between the glass laminate the distance between hole and any active part of the PV module (cell or interconnection ribbon) can be 20 mm as a minimum (instead of 30 mm between edge and cell that is normally required (see also chapter 21)

How is the electrical connection done?

The electrical connection of a VIDURSOLAR PV-module can be done either with a junction box or the rear face of the glass (as in a standard glass-tedlar PV-module) or with an edge terminal that is secured to the edge of the laminate. Both junction boxes have to be fastened to the glass in order to assure maximum isolation of the electrical conductors. The advantage of the rear face junction box is that the mounting of the glass and the electrical connection can be done independently. The disadvantage from the architectural perspective is that it may not be desirable for the junction box and cabling to be visible from the interior of a building. Also, the rear pane applied junction box cannot be used in double glazing unit where the air cavity cannot be puncture and therefore an edge terminal has to be used. The main advantage is the invisibility of connectors and cables once the PV-glass is installed. If using an edge terminal it is important to check that the support sections have a sufficient void for the terminal and cabling or how it can be adapted. VIDURSOLAR uses an edge terminal that needs 15 mm of space inside the profile. The cables have a diameter of 6 mm and the connectors have a diameter of 14 mm. This criteria needs to be reviewed for each project with the supplier of the support structures. The number of junction boxes required for each module is dependant upon the electrical circuit of the module. If up to 4 cell columns one junction box should be sufficient, but if there are more cell columns normally not more than 2 junction boxes are required. In the case of edge terminals this may be different and should be checked for each case.

What are the detailed design possibilities for VIDURSOLAR glass-glass PV modules?

Shapes: rectangles, circles, triangles and specials.
Size: flexible to suit project specific requirements but the maximum commercial size is 2.60 m x 1.60m. Bigger sizes are available but due to difficulties in handling and fabrication the costs are higher and should be discussed on a project basis. The minimum size is one cell (156mm x 156mm) which with connection details produces a module of 22 cm x 26 cm. Composition and thickness: The standard composition of VIDURSOLAR PV-modules is the following:

  • Front pane: 5mm extra-white tempered security glass with polished edges
  • Encapsulant: PVB (polivinylbutyl) of 0,76mm
  • PV cells
  • Encapsulant: PVB (polivinylbutyl) of 0,76mm
  • Rear pane: 5mm float tempered security glass with polished edges with different glass types available

The standard thicknesses of the PV laminate are 5+5 = total of 11,5mm or 6+6 = total of 13,5 mm but 8+8 or 4+4 can by consultation be considered on special projects.

Weight of the product: The total weight has to be taken into account as it is a major factor for fabrication. If possible the total weight of a PV laminate unit should not exceed 100 kg. The weight of glass is about 2,5 kg/mm thickness/ m2 and mm of thickness. The weight of the PVB layer of 1,5 mm thickness is 2,5 kg per m2. Therefore 5+5mm laminate (total thickness of 11,5 mm) has a total weight of about 27,5 kg / m2.

Insulating units: to achieve thermal and acoustic performance of the building envelope cavities of 10, 12, 16 or 20 mm are available. The inner glass pane can be a laminate, a requirement for roof glazing, or a simple glass pane (normally tempered). The thickness and type of the inner glass unit is flexible, and can be low-e glass, coloured or screen-printed glass, etc.

Glass colour: directly applied to the rear glass or translucent when applied to the intermediate layer. In the first case an opaque or acid simulating vitrified painting is applied. In the second case another PVB-sheet is introduced behind the cells (thickness 0,38 mm additionally). The introduction of colour can result in a slight reduction of the energy output as dark colours will increase the heat build-up of the PV-cells resulting in a voltage drop/lower power output. In BIPV applications this power loss is 2-3% and therefore quite low.

Feature glass: it is possible to combine photovoltaic cells with screen-printing or other specialist glass applications.

Cell types: mono- or poly-crystalline cells of different colours and power categories. Poly-crystalline cells are the most readily available in a size of 156 mm x 156 mm cells and are offered as our standard product. An optional cell size is 125 mm x 125 mm, but this is subject to special order. Coloured cells are available in the two sizes and ordered on a project by project basis with a minimum delivery time of 2 months, if no stock is available. The semi-transparent perforated cells are available in 125 mm x 125 mm also on a special order basis.

Transparency: variable spaces between the cells provide project specific levels of solar protection and light transmission. The minimum cell distance is 2 mm and maximum 60 mm in the alignment direction of connected cells. The distance between rows of un-connected cell columns is optional but should not exceed 100 mm. A minimum distance between live parts of the PV–module (cells or interconnection ribbons) of 30 mm is a requirement when designing the cell distribution. The light transmission (transparency) is dictated by the free surface area of glass (visible after installation) between the cells and interconnection ribbons.

Electrical connections: junction box on the rear glass or edge terminal to be hidden in the support structure. Please see chapter 20 for more details. Fastener Methods: Inclusion of apertures for point fixing details similar to structural glass. Please see chapter 19 for more details.

What testing are VIDURSOLAR PV modules in compliance with – which norms are used?

VIDRUSOLAR production processes and products comply with the following norms and have passed the corresponding tests:

Production process controlled according to ISO 9001.
VIDURSOLAR PV glasses are manufactured as a construction product under the CE mark denomination of “laminated safety glass”. This is defined by EN 14449. Tested according to different norms defining product quality of glass in construction:

  • EN 14449: Glass for construction – laminated safety glass – conformity of product (CE mark)
  • EN 12150: Tempered glass
  • EN 12600: Resistance test – soft body (pendulum test)
  • EN 12543, 1-6: Laminated safety glass

Designed and produced according to EN 61215 and EN 61730. These norms are designed for type approval and safety of standard PV-modules. Despite VIDURSOLAR PV-modules normally being a custom-made product we are frequently asked for these norms. As a result corresponding tests for our module range already have a declaration from TÜV Rheinland for the tests done to date. This module family includes laminates of 5+5 or thicker, size up to 2,5 m x 1,5 m, Sunways poly-crystalline PV cells and edge connector. In theory other cells and junction boxes are not covered by this testing but the positive results of these tests form part of the quality guarantee provided. Product specific certification is pending.