Building-integrated photovoltaics

The CIS Tower in Manchester, England was clad in PV panels at a cost of £5.5 million. It started feeding electricity to the National Grid in November 2005.

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

The term building-applied photovoltaics (BAPV) is sometimes used to refer to photovoltaics that are a retrofit – integrated into the building after construction is complete. Most building-integrated installations are actually BAPV. Some manufacturers and builders differentiate new construction BIPV from BAPV.

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). A 2011 economic assessment and brief overview of the history of BIPV by the U.S. National Renewable Energy Laboratory suggests that there may be significant technical challenges to overcome before the installed cost of BIPV is competitive with photovoltaic panels. However, there is a growing consensus that through their widespread commercialization, BIPV systems will become the backbone of the zero energy building (ZEB) European target for 2020. Despite technical promise, social barriers to widespread use have also been identified, such as the conservative culture of the building industry and integration with high-density urban design. These authors suggest enabling long-term use likely depends on effective public policy decisions as much as the technological development.

Photovoltaic wall near Barcelona, Spain

Projet BIPV, Gare de Perpignan, Southern France

PV Solar parking canopy, Autonomous University of Madrid, Spain

Forms

2009 Energy Project Award Winning 525 kilowatt BIPV CoolPly system manufactured by SolarFrameWorks, Co. on the Patriot Place Complex Adjacent to the Gillette Stadium in Foxborough, MA. System is installed on single-ply roofing membrane on a flat roof using no roof penetrations.

BAPV solar facade on a municipal building located in Madrid (Spain).

Building-Integrated Photovoltaic modules are available in several forms.

• Flat roofs
  • The most widely installed to date is a thin film solar cell integrated to a flexible polymer roofing membrane.
• Pitched roofs
  • Modules shaped like multiple roof tiles.
  • Solar shingles 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 is kept above the roofing membrane.
• Facade
  • 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
  • (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 solar panels use a tin oxide coating 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.

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.

Government subsidies

See also: PV financial 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 €0.25/kWh
• Germany €0.05/kWh facade bonus expired in 2009
• Italy €0.04–€0.09/kWh
• United Kingdom 6.38–13.39 p/kWh [1]
• Spain, compared with a non- building installation that receives €0.28/kWh (RD 1578/2008):
  • ≤20 kW: €0.34/kWh
  • >20 kW: €0.31/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 per 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 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.

Other integrated photovoltaics

Vehicle-integrated photovoltaics (ViPV) are similar for vehicles. Solar cells could be embedded into panels exposed to sunlight such as the hood, roof and possibly the trunk depending on a car's design.

See also

• Distributed generation
• Microgeneration
• Perovskite solar cell
• Solar panel
• Renewable energy
• Roof tile
• Smart glass, a type of window blind capable of conserving energy for cooling
• Solar cell
• Solar power
• Solar thermal
• Zero-energy building

External links

• Building integrated photovoltaics an overview of the existing products and their fields of application
• 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.