Building-integrated photovoltaics (BIPV) are photovoltaic materials that are used to replace conventional building materials in parts of the building envelope

Building envelope

The building envelope is the physical separator between the interior and the exterior environments of a building. Another emerging term is "Building Enclosure". It serves as the outer shell to help maintain the indoor environment and facilitate its climate control...

 such as the roof, skylights, or facades. They are increasingly being incorporated into the construction of new buildings as a principal or ancillary source of electrical power, although existing buildings may be retrofitted with BIPV modules as well. The advantage of integrated photovoltaics over more common non-integrated systems is that the initial cost can be offset by reducing the amount spent on building materials and labor that would normally be used to construct the part of the building that the BIPV modules replace. These advantages make BIPV one of the fastest growing segments of the photovoltaic industry.

History

PV applications for buildings began appearing in the 1970s. Aluminum-framed photovoltaic modules were connected to, or mounted on, buildings that were usually in remote areas without access to an electric power grid. In the 1980s photovoltaic module add-ons to roofs began being demonstrated. These PV systems were usually installed on utility-grid-connected buildings in areas with centralized power stations. In the 1990s BIPV construction products specially designed to be integrated into a building envelope became commercially available. A 1998 doctoral thesis by Patrina Eiffert, entitled An Economic Assessment of BIPV, hypothesized that one day there would an economic value for trading Renewable Energy Credits (RECs).

Forms

Building-Integrated Photovoltaic modules are available in several forms.

• Flat roofs
  • The most widely installed to date is a thin film solar cell
    Thin film solar cell
    A thin-film solar cell , also called a thin-film photovoltaic cell , is a solar cell that is made by depositing one or more thin layers of photovoltaic material on a substrate...
    
     integrated to a flexible polymer
    Polymer
    A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
    
     roofing membrane.

• Pitched roof
  Pitched roof
  A pitched roof is a roof for which one or more roof surfaces is pitched more than 10 degrees, and alternately a roof with two slopes that meet at a central ridge. Some definitions are even more general, including any roof with a sloping surface or surfaces....
  
  s
  • Modules shaped like multiple roof tiles.
  • Solar shingles
    Solar shingles
    Solar shingles, also called photovoltaic shingles, are solar cells designed to look like conventional asphalt shingles. There are several varieties of solar shingles, including shingle-sized solid panels that take the place of a number of conventional shingles in a strip, semi-rigid designs...
    
     are modules designed to look and act like regular shingles, while incorporating a flexible thin film cell.
  • It extends normal roof life by protecting insulation and membranes from ultraviolet rays and water degradation. It does this by eliminating condensation because the dew point
    Dew point
    The dew point is the temperature to which a given parcel of humid air must be cooled, at constant barometric pressure, for water vapor to condense into liquid water. The condensed water is called dew when it forms on a solid surface. The dew point is a saturation temperature.The dew point is...
    
     is kept above the roofing membrane.

• Facade
  Facade
  A facade or façade is generally one exterior side of a building, usually, but not always, the front. The word comes from the French language, literally meaning "frontage" or "face"....
  
  
  • Facades can be installed on existing buildings, giving old buildings a whole new look. These modules are mounted on the facade of the building, over the existing structure, which can increase the appeal of the building and its resale value.

• Glazing
  Glazing
  Glazing, which derives from the Middle English for 'glass', is a part of a wall or window, made of glass. Glazing also describes the work done by a professional "glazier"...
  
  
  • (Semi)transparent modules can be used to replace a number of architectural elements commonly made with glass or similar materials, such as windows and skylights.

Transparent and translucent photovoltaics

Transparent

Transparency and translucency

In the field of optics, transparency is the physical property of allowing light to pass through a material; translucency only allows light to pass through diffusely. The opposite property is opacity...

 solar panels use a tin oxide

Tin oxide

Tin oxide may refer to:* Tin oxide , SnO* Tin dioxide , SnO2...

 coating

Coating

Coating is a covering that is applied to the surface of an object, usually referred to as the substrate. In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance...

 on the inner surface of the glass panes to conduct current out of the cell. The cell contains titanium oxide that is coated with
a photoelectric dye

Dye

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

.

Most conventional solar cells use visible and infrared light to generate electricity. In contrast, the innovative new solar cell also uses ultraviolet radiation. Used to replace conventional window glass, or placed over the glass, the installation surface area could be large, leading to potential uses that take advantage of the combined functions of power generation, lighting and temperature control.

Another name for transparent photovoltaics is “translucent photovoltaics” (they transmit half the light that falls on them). Similar to inorganic photovoltaics, organic photovoltaics are also capable of being translucent.

Incentives

In some countries, additional incentives, or subsidies, are offered for building-integrated photovoltaics in addition to the existing feed-in tariffs for stand-alone solar systems. Since July 2006 France offered the highest incentive for BIPV, equal to an extra premium of EUR 0.25/kWh paid in addition to the 30 Euro cents for PV systems. These incentives are offered in the form of a rate paid for electricity fed to the grid.

European Union

• France + EUR 0.25/kWh
• Germany - former EUR 0,05/kWh facade bonus expired in 2009
• Italy + EUR 0.04-0.09 kWh
• Spain, compared with a non- building installation that receives 28,00 cent€/kWh (RD 1578/2008):
  • <= 20 KW, 34,00 cent€/kWh
  • >20 kW: 31,00cent€/kWh

USA

• USA - Varies by state. Check Database of State Incentives for Renewables & Efficiency for more details.

China

Further to the announcement of a subsidy program for BIPV projects in March 2009 offering RMB20/watt for BIPV systems and RMB15/watt for rooftop systems, the Chinese government recently unveiled a photovoltaic energy subsidy program “the Golden Sun Demonstration Project”. The subsidy program aims at supporting the development of photovoltaic electricity generation ventures and the commercialization of PV technology. The Ministry of Finance, the Ministry of Science and Technology and the National Energy Bureau have jointly announced the details of the program in July 2009. Qualified on-grid photovoltaic electricity generation projects including rooftop, BIPV, and ground mounted systems are entitled to receive a subsidy equal to 50% of the total investment of each project, including associated transmission infrastructure. Qualified off-grid independent projects in remote areas will be eligible for subsidies of up to 70% of the total investment. In mid November, China’s finance ministry has selected 294 projects projects totaling 642 megawatts that come to roughly RMB 20 billion ($3 billion) in costs for its subsidy plan to dramatically boost the country’s solar energy production.

See also

• Microgeneration
  Microgeneration
  Microgeneration is the small-scale generation of heat and power by individuals, small businesses and communities to meet their own needs, as alternatives or supplements to traditional centralized grid-connected power...
  
  
• Renewable energy
  Renewable energy
  Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...
  
  
• Roof tile
• Solar cell
  Solar cell
  A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
  
  
• Solar panel
  Photovoltaic module
  A solar panel is a packaged, connected assembly of solar cells, also known as photovoltaic cells...
  
  
• Solar power
  Solar power
  Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...
  
  
• Solar thermal
• Zero-energy building
• Smart glass is a type of window blind capable of conserving energy for cooling

External links

• Canadian Solar Buildings Research Network
• Wisconsin Public Service Corporation: Building-Integrated Photovoltaics (buildingsolar.com)
• PV UP-SCALE, a European founded project (contract EIE/05/171/SI2.420208) related to the large-scale implementation of photovoltaics (PV) in European cities.