BIPV stands for ‘building-integrated photovoltaics.’ In other words, BIPV is about the integration of photovoltaics or solar technology in buildings, whereby PV elements become an integral part of permanent structures.
The trend of BIPV is still at the cusp of the built environment and construction industries. However, it is slowly gaining traction, especially with the greater emphasis on carbon footprint reduction in some countries and attractive tax rebates to apply green technology in others.
For instance, the EU2030 energy target drives architects and the construction industry to renovate and decarbonize existing buildings in some European countries.
Innovative architects and PV specialists in many parts of the world are also exploring creative ways to incorporate photovoltaic technology into building designs, giving rise to a new vernacular of solar architecture.
What is solar architecture?
Solar architecture is a term synonymous with PV architecture, photovoltaic architecture, or BIPV architecture. The concept of solar architecture has 3 underpinning aspects:
- Integration of technology – using the photovoltaic system in a multifunctional manner by incorporating it into the structure of a building
- Aesthetics – the architectural appearance of the PV system
- Energy integration – the capability of a PV system to interact with a building and its environment by maximizing electricity generation.
Function of BIPV
Serving a dual purpose, BIPV should convert solar energy into electricity while providing building envelope functions such as:
- weather protection (waterproofing, sun protection),
- thermal insulation
- noise protection
- daylight illumination
When implementing BIPV, the solar architectural approach also considers the orientation of a building towards the sun.
The spaces which form part of the architectural design should also naturally circulate air. Even the type of materials should contribute to the thermal mass or light dispersing qualities of the BIPV solution.
What is a BIPV system?
A complete BIPV system has these components:
- PV modules – the PV panels which make up the module can be either thin-film or crystalline, transparent, semi-transparent, or opaque.
- Charge controller – it regulates the power into and out of the battery storage bank (in stand-alone systems)
- Power storage system – consists of batteries in off-grid systems or the utility grid in utility-interactive systems.
- Power conversion equipment – usually an inverter to convert DC output to AC
- Backup power supplies – for example, diesel generators for off-grid systems
- Mounting support – mounting hardware, wiring, and safety disconnects
- Heating, cooling, or e-mobility systems (where necessary)
Benefits of BIPV
BIPV not only produces on-site clean electricity without requiring additional land area, but it can also impact the energy consumption of a building through daylight utilization and reduction of cooling loads.
BIPV can therefore contribute to achieving net-zero energy buildings. Turning roofs and façades into energy-generating assets, BIPV is the only building material that has a return on investment (ROI).
Furthermore, the diverse use of BIPV systems opens many opportunities for architects and building designers to enhance buildings’ visual appearance.
Finally, most importantly, building owners benefit from reduced electricity bills and the positive image of being recognized as ‘green’ and ‘innovative.’
What is a BIPV solar panel?
As the name suggests, it is a solar PV module integrated with the architecture of a building.
BIPV solar panels currently available on the market use either crystalline silicon-based (c-Si) solar cells or thin-film technologies such as amorphous-based silicon (a-Si), cadmium telluride (CdTe), and copper indium gallium selenide (CIGS).
Semi-transparency can be achieved with most technology by either spacing the opaque solar cells or making the thin film layer transparent. However, module efficiency decreases with the increase of transparency.
Applications of BIPV
The built environment allows for many ways to integrate BIPV. In general, there are three main application areas for BIPV:
- roofs (e.g., shingles, tiles, skylights)
- façades (e.g., cladding, curtain walls, windows)
- shading systems.
BIPV can be incorporated into a roof during construction or added later. The type of photovoltaic technology or system to be used depends on the nature of the roof, the building, and the size of the roof.
For instance, some buildings have sloping roofs with tiles or shingles. For this type of roof shape, roof tiles or shingles integrated with solar cells are suitable.
These tiles can come in PV roof tiles, PV roof shingles, or solar laminated tiles. PV roof shingles are produced with thin-film solar cells on glass or metal substrates or crystalline solar cells.
Roof-integrated photovoltaics can be designed to look very close to or identical to the regular, existing tiles on a roof, especially using solar laminates, which can come in various colors.
Flat roofs are often prescribed amorphous silicon modules or substrate synthetic rubber modules. These are more flexible and lighter than PV tiles or shingles.
Photovoltaic glazing can be applied for skylights, meaning the regular glass in the skylight is replaced by PV laminated glass.
The same technology is also employed for plastic roofs, which are curved, or roofs that require transparency for more light to pass through.
For a large roof area where the desired appearance is transparent or semi-transparent, plastic is the preferred medium over glass laminated PV panels.
This is due to safety issues. Should there be any hard impact on the roof, large swathes of falling glass will cause great harm and damage to the occupants below the roof.
BIPV in facades
A building’s façade includes the building’s walls, cladding, curtain walls, awnings, and windows.
Installations for facades are usually vertical, which garners lower solar generation output than roofs. This is because the PV cells face sunlight at an angle throughout most of the day.
When placed on the roof, the PV cells are exposed to longer daylight hours, which gives a greater electrical output.
However, the larger surface area of facades can compensate for this shortfall.
An example of BIPV application on facades is saw-toothed designs on a building façade. This application allows entry of more direct sunlight. At the same time, it provides passive shading, an additional architectural benefit.
There are a few BIPV modules for facades: classic (opaque) PV panels, transparent panels, and semi-transparent panels (such as microperforated amorphous modules and crystalline modules).
These also come in several colors, which gives architects and interior designers unlimited room for their imagination to be realized.
There are instances where the entire wall of a structure is replaced by PV modules meant for facades, using a technology called façade glazing. Examples of such applications are greenhouses, atriums, and sunspaces.
These buildings’ walls can be replaced by a mix of laminated PV panels, which are transparent, semi-transparent, and opaque. Attractive patterns can be formed in this way and purposefully placed opaque PV panels to offer shaded areas.
The artificial supertrees in Gardens by the Bay, Singapore, integrated with solar photovoltaic systems, provide power for lighting at night and offer shelter during the day.
Solar shading architecture
Also known as shadow-voltaic systems, this type of photovoltaic technology is often part of a BIPV façade. Their dual functions are to generate electricity and to provide shade.
The PV modules of solar shading architecture often serve as venetian blinds or awnings. They can be permanent fixtures or have sun-tracking systems.
The photovoltaic technology applied here is similar to that of BIPV for façades. Commonly employed are solar glazing and transparent solar modules.
Are BIPV installations more complicated?
BIPV installations are more complicated compared to regular solar panels as it needs more preparation, planning and skill. As integrated solar needs to be discussed during the early stages of building construction, developers, architects as well as PV system designers need to work closely with each other.
Because there are not many reference projects, and integrated solar products are still considered quite new, architects will need foresight and vision to put the building plan together. Additionally, a solar expert will also be required.
BIPV building design considerations
Planning for environmental and structural factors will maximize the BUPV system as these two factors play a role in the aesthetics, economics and efficiency of solar systems.
- Energy requirements of the building – BIPV system design should consider if the building should be able to operate independent of the electrical grid. This will require batteries as well as on-site storage systems.
- Design of the solar system – This is usually determined by the energy requirements of the building. However, structure and aesthetic factors may limit choice of materials. For example, crystalline silicon panels have higher costs and more design limitations, but higher energy output per square meter. Thin film materials cost less, are more flexible and easily integrated into surfaces but generate less power per square meter.
- Weather conditions and climate – Clouds, and rainfall can have an effect on the system. Areas in which there is high air pollution will most likely require panels to be cleaned regularly to maintain efficiency.
- Shading – Nearby trees, buildings as well as other structures that may block the sun and thus, cause a reduction in the PV system output.
- Insolation – The average amount of solar radiation received in a particular area.
- Latitude – This refers to the distance from the equator that influences optimal tilt angle for solar radiation received by the solar panels.
Potential for growth in BIPV
About 100 GWp of power a year comes from photovoltaics installed all over the world. This works out to 350 to 400 million solar modules sold per year.
However, the integration of solar technology into buildings remains small in comparison to those figures. According to a report by PVSITES, only 2% of the installed solar capacity was integrated into building skins in 2016.
This figure is minuscule because over 70% of the energy produced worldwide is consumed in cities, and over 40% of all greenhouse gas emissions originate from urban areas.
The potential for growth in BIPV is therefore huge. Furthermore, BIPV is not just limited to its capacity to generate electricity.
There is a subset of BIPV called BIPVT, which is BIPV with thermal energy recovery. BIPVT systems produce both heat and electricity simultaneously from the same solar installation. Its application is handy for countries that need heating.
The extracted thermal energy is available either for direct use or low-temperature applications, such as fresh air preheating. It can also be used for higher temperatures to mediate a heat pump—for example, space heating, domestic water heating.
The main benefit of BIPVT is that it produces more energy per surface area than a standalone BIPV system. Furthermore, under heat recovery conditions, a BIPTV system’s PV cells will be cooler than in a BIPV roof, thus improving the module efficiency.
BIPV are solar power generating building products or systems that are seamlessly integrated into the building envelope. They replace conventional building materials by serving as building envelope material.
At the same time, BIPV panels and systems offer savings in electricity costs. By replacing the building material, BIPV also provides some savings in materials.
The endless supply of electricity generated helps reduce the cost of energy, usage of fossil fuels, and the emission of ozone-depleting gasses and carbon emissions.
BIPV also adds architectural interest to buildings. Not only is BIPV functional, but it can also give buildings a futuristic appearance. BIPV is also flexible enough to be applied to existing structures, including heritage buildings.