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Building-integrated photovoltaics
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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 façades.[1] 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. In addition, BIPV allows for more widespread solar adoption when the building's aesthetics matter and traditional rack-mounted solar panels would disrupt the intended look of the building.
The term building-applied photovoltaics (BAPV) is sometimes used to refer to photovoltaics that are 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.[2]
History
[edit]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.[3] A 1998 doctoral thesis by Patrina Eiffert, entitled An Economic Assessment of BIPV, hypothesized that one day there would be an economic value for trading Renewable Energy Credits (RECs).[4] 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.[5] 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.[6] Despite the 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.[7]
Forms
[edit]

The majority of BIPV products use one of two technologies: Crystalline Solar Cells (c-SI) or Thin-Film Solar Cells. C-SI technologies comprise wafers of single-cell crystalline silicon which generally operate at a higher efficiency that Thin-Film cells but are more expensive to produce.[8] The applications of these two technologies can be categorized by five main types of BIPV products:[8]
- Standard in-roof systems. These generally take the form of applicable strips of photovoltaic cells.
- Semi-transparent systems. These products are typically used in greenhouse or cold-weather applications where solar energy must simultaneously be captured and allowed into the building.
- Cladding systems. There are a broad range of these systems; their commonality being their vertical application on a building façade.
- Solar Tiles and Shingles. These are the most common BIPV systems as they can easily be swapped out for conventional shingle roof finishes.
- Flexible Laminates. Commonly procured in thin-sheet form, these products can be adhered to a variety of forms, primarily roof forms.
With the exception of flexible laminates, each of the above categories can utilize either c-SI or Thin-Film technologies, with Thin-Film technologies only being applicable to flexible laminates – this renders Thin-Film BIPV products ideal for advanced design applications that have a kinetic aspect.
Between the five categories, BIPV products can be applied in a variety of scenarios: pitched roofs, flat roofs, curved roofs, semi-transparent façades, skylights, shading systems, external walls, and curtain walls, with flat roofs and pitched roofs being the most ideal for solar energy capture.[8] The ranges of roofing and shading system BIPV products are most commonly used in residential applications whereas the wall and cladding systems are most commonly used in commercial settings.[9] Overall, roofing BIPV systems currently have more of the market share and are generally more efficient than façade and cladding BIPV systems due to their orientation to the sun.[9]
Building-integrated photovoltaic modules are available in several forms:
- Flat roofs
- The most widely installed to date is an amorphous thin film solar cell integrated to a flexible polymer module which has been attached to the roofing membrane using an adhesive sheet between the solar module backsheet and the roofing membrane.[clarification needed] Copper Indium Gallium Selenide (CIGS) technology is now able to deliver cell efficiency of 17% as produced by a US-based company[10] and comparable building-integrated module efficiencies in TPO single ply membranes by the fusion of these cells by a UK-based company.[11]
- Pitched roofs
- Solar roof tiles are (ceramic) roof tiles with integrated solar modules. The ceramic solar roof tile is developed and patented by a Dutch company[12] in 2013.
- 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.[13]
- Façade
- Façades can be installed on existing buildings, giving old buildings a whole new look. These modules are mounted on the façade of the building, over the existing structure, which can increase the appeal of the building and its resale value.[17]
- Glazing
- Photovoltaic windows are (semi)transparent modules that can be used to replace a number of architectural elements commonly made with glass or similar materials, such as windows and skylights. In addition to producing electric energy, these can create further energy savings due to superior thermal insulation properties and solar radiation control.
- Photovoltaic Stained Glass: The integration of energy harvesting technologies into homes and commercial buildings has opened up additional areas of research which place greater considerations on the end product's overall aesthetics. While the goal is still to maintain high levels of efficiency, new developments in photovoltaic windows also aim to offer consumers optimal levels of glass transparency and/or the opportunity to select from a range of colors. Different colored 'stained glass' solar panels can be optimally designed to absorb specific ranges of wavelengths from the broader spectrum. Colored photovoltaic glass has been successfully developed using semi transparent, perovskite, and dye sensitized solar cells.
- Plasmonic solar cells that absorb and reflect colored light have been created with Fabry-Pérot etalon technology. These cells are composed of "two parallel reflecting metal films and a dielectric cavity film between them."[18] The two electrodes are made from Ag and the cavity between them is Sb2O3 based. Modifying the thickness and refractance of the dielectric cavity changes which wavelength will be most optimally absorbed. Matching the color of the absorption layer glass to the specific portion of the spectrum that the cell's thickness and refractance index is best tuned to transmit both enhances the aesthetic of the cell by intensifying its color and helps to minimize photocurrent losses. 34.7% and 24.6% transmittance was achieved in red and blue light devices respectively. Blue devices can convert 13.3% of light absorbed into power, making it the most efficient across all colored devices developed and tested.
- Perovskite solar cell technology can be tuned to red, green and blue by changing the metallic nanowire thickness to 8, 20 and 45 nm respectively.[19] Maximum power efficiencies of 10.12%, 8.17% and 7.72% were achieved by matching glass reflectance to the wavelength that the specific cell is designed to most optimally transmit.
- Dye-sensitized solar cells employ liquid electrolytes to capture light and convert it into usable energy; this is achieved in a similar way to how natural pigments facilitate photosynthesis in plants. While chlorophyll is the specific pigment responsible for producing the green color in leaves, other dyes found in nature such as, carotenoid and anthocyanin, produce variations of orange and purples dyes.[20] Researchers from the University of Concepcion have proved the viability of dye sensitized colored solar cells that both appear and selectively absorb specific wavelengths of light.[21] This low cost solution uses extracting natural pigments from maqui fruit, black myrtle and spinach as sensitizers. These natural sensitizers are then placed between two layers of transparent glass. While the efficiency levels of these particularly low cost cells remains unclear, past research in organic dye cells have been able to achieve a "high power conversion efficiency of 9.8%."[22][23][24]
Transparent and translucent photovoltaics
[edit]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.[25]
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.[citation needed]
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.
Types of transparent and translucent photovoltaics
[edit]Non-wavelength-selective
[edit]Some non-wavelength-selective photovoltaics achieve semi-transparency by spatial segmentation of opaque solar cells. This method uses any type of opaque photovoltaic cell and spaces several small cells out on a transparent substrate. Spacing them out in this way reduces power conversion efficiencies dramatically while increasing transmission.[26]
Another branch of non-wavelength-selective photovoltaics utilize visibly absorbing thin-film semi-conductors with small thicknesses or large enough band gaps that allow light to pass through. This results in semi-transparent photovoltaics with a similar direct trade off between efficiency and transmission as spatially segmented opaque solar cells.[26]
Wavelength-selective
[edit]Wavelength-selective photovoltaics achieve transparency by utilizing materials that only absorb UV and/or NIR light and were first demonstrated in 2011.[27] Despite their higher transmissions, lower power conversion efficiencies have resulted due to a variety of challenges. These include small exciton diffusion lengths, scaling of transparent electrodes without jeopardizing efficiency, and general lifetime due to the volatility of organic materials used in TPVs in general.[26]
Innovations in transparent and translucent photovoltaics
[edit]Early attempts at developing non-wavelength-selective semi-transparent organic photovoltaics using very thin active layers that absorbed in the visible spectrum were only able to achieve efficiencies below 1%.[28] However in 2011, transparent organic photovoltaics that utilized an organic chloroaluminum phthalocyanine (ClAlPc) donor and a fullerene acceptor exhibited absorption in the ultraviolet and near-infrared (NIR) spectrum with efficiencies around 1.3% and visible light transmission of over 65%.[27] In 2017, MIT researchers developed a process to successfully deposit transparent graphene electrodes onto organic solar cells resulting in a 61% transmission of visible light and improved efficiencies ranging from 2.8%-4.1%.[29]
Perovskite solar cells, popular due to their promise as next-generation photovoltaics with efficiencies over 25%, have also shown promise as translucent photovoltaics. In 2015, a semitransparent perovskite solar cell using a methylammonium lead triiodide perovskite and a silver nanowire mesh top electrode demonstrated 79% transmission at an 800 nm wavelength and efficiencies at around 12.7%.[30]
Government subsidies
[edit]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.[31][32][33] These incentives are offered in the form of a rate paid for electricity fed to the grid.
Europe
[edit]- France €0.25/kWh[32]
- Germany €0.05/kWh façade bonus expired in 2009
- Italy €0.04–€0.09/kWh[citation needed]
- United Kingdom 4.18 p/kWh[34]
- 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
United States
[edit]- United States – Varies by state. Check Database of State Incentives for Renewables & Efficiency for more details.[35]
China
[edit]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.[36] 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.[37] 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.[38]
Other integrated photovoltaics
[edit]Vehicle-integrated photovoltaics (ViPV) are similar for vehicles.[39] 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.[40][41][42][43]
Challenges
[edit]Performance
[edit]Because BIPV systems generate on-site power and are integrated into the building envelope, the system's output power and thermal properties are the two primary performance indicators. Conventional BIPV systems have a lower heat dissipation capability than rack-mounted PV, which results in BIPV modules experiencing higher operating temperatures. Higher temperatures may degrade the module's semiconducting material, decreasing the output efficiency and precipitating early failure.[44] In addition, the efficiency of BIPV systems is sensitive to weather conditions, and the use of inappropriate BIPV systems may also reduce their energy output efficiency.[44] In terms of thermal performance, BIPV windows can reduce the cooling load compared to conventional clear glass windows, but may increase the heating load of the building.[45]
Cost
[edit]The high upfront investment in BIPV systems is one of the biggest barriers to implementation.[44] In addition to the upfront cost of purchasing BIPV components, the highly integrated nature of BIPV systems increases the complexity of the building design, which in turn leads to increased design and construction costs.[44] Also, insufficient and inexperienced practitioners lead to higher employment costs incurred in the development of BIPV projects.[44]
Policy and regulation
[edit]Although many countries have support policies for PV, most do not have additional benefits for BIPV systems.[44] And typically, BIPV systems need to comply with building and PV industry standards, which places higher demands on implementing BIPV systems. In addition, government policies of lower conventional energy prices will lead to lower BIPV system benefits, which is particularly evident in countries where the price of conventional electricity is very low or subsidized by governments, such as in GCC countries.[44][46]
Public understanding
[edit]Studies show that public awareness of BIPV is limited and the cost is generally considered too high. Deepening public understanding of BIPV through various public channels (e.g., policy, community engagement, and demonstration buildings) is likely to be beneficial to its long-term development.[44]
See also
[edit]- Distributed generation
- List of pioneering solar buildings
- Microgeneration
- Nanoinverter
- Passive solar building design
- Perovskite solar cell
- Solar panel
- Rooftop solar power
- Roof tile
- Smart glass, a type of window blind capable of conserving energy for cooling
- Solar cell
- Solar power
- Solar thermal
- Zero-energy building
References
[edit]- ^ Strong, Steven (June 9, 2010). "Building Integrated Photovoltaics (BIPV)". wbdg.org. Whole Building Design Guide. Retrieved 2011-07-26.
- ^ "Building Integrated Photovoltaics: An emerging market". Archived from the original on 24 September 2015. Retrieved 6 August 2012.
- ^ Eiffert, Patrina; Kiss, Gregory J. (2000). Building-Integrated Photovoltaic Designs for Commercial and Institutional Structures: A Source Book for Architect. DIANE. p. 59. ISBN 978-1-4289-1804-7.
- ^ Eiffert, Patrina (1998). An Economic Assessment of Building Integrated Photovoltaics. Oxford Brookes School of Architecture.
{{cite book}}: CS1 maint: location missing publisher (link) - ^ James, Ted; Goodrich, A.; Woodhouse, M.; Margolis, R.; Ong, S. (November 2011). "Building-Integrated Photovoltaics (BIPV) in the Residential Sector: An Analysis of Installed Rooftop System Prices." NREL/TR-6A20-53103.
- ^ Kylili, Angeliki; Fokaides, Paris A. (2014). "Investigation of building integrated photovoltaics potential in achieving the zero energy building target". Angeliki Kylili, Paris A. Fokaides. 23 (1): 92–106. Bibcode:2014InBEn..23...92K. doi:10.1177/1420326X13509392. S2CID 110970142.
- ^ Temby, Owen; Kapsis, Konstantinos; Berton, Harris; Rosenbloom, Daniel; Gibson, Geoffrey; Athienitis, Andreas; Meadowcroft, James (2014). "Building-Integrated Photovoltaics: Distributed Energy Development for Urban Sustainability". Environment: Science and Policy for Sustainable Development. 56 (6): 4–17. Bibcode:2014ESPSD..56f...4T. doi:10.1080/00139157.2014.964092. S2CID 110745105.
- ^ a b c Tripathy, M.; Sadhu, P. K.; Panda, S. K. (2016-08-01). "A critical review on building integrated photovoltaic products and their applications". Renewable and Sustainable Energy Reviews. 61: 451–465. Bibcode:2016RSERv..61..451T. doi:10.1016/j.rser.2016.04.008. ISSN 1364-0321.
- ^ a b Kuhn, Tilmann E.; Erban, Christof; Heinrich, Martin; Eisenlohr, Johannes; Ensslen, Frank; Neuhaus, Dirk Holger (2021-01-15). "Review of technological design options for building integrated photovoltaics (BIPV)". Energy and Buildings. 231 110381. Bibcode:2021EneBu.23110381K. doi:10.1016/j.enbuild.2020.110381. ISSN 0378-7788. S2CID 225225301.
- ^ MiaSolé website
- ^ BIPVco technical datasheet
- ^ ZEP BV
- ^ Eiffert, Patrina (2000). Building-Integrated Photovoltaic Designs for Commercial and Institutional Structures: A Source Book for Architect (PDF). pp. 60–61.
- ^ "Solar Panels vs. Thin-Film Laminates: Costs, Pros & Cons, Top Brands". 19 January 2022.
- ^ Technical datasheet for a free-standing flexible module
- ^ Technical datasheet for a heat and vacuum-sealed CIGS cell
- ^ Henemann, Andreas (2008-11-29). "BIPV: Built- in Solar Energy". Renewable Energy Focus. 9 (6): 14, 16–19. Bibcode:2008REneF...9...14H. doi:10.1016/S1471-0846(08)70179-3.
- ^ Rim Yeo, Hye (2020). "Aesthetic and colorful: Dichroic polymer solar cells using high-performance Fabry-Pérot etalon electrodes with a unique Sb2O3 cavity". Nano Energy. 77 (6) 105146. doi:10.1016/j.nanoen.2020.105146. S2CID 225502407.
- ^ Lee, KT (2017-09-06). "Highly Efficient Colored Perovskite Solar Cells Integrated with Ultrathin Subwavelength Plasmonic Nanoresonators". Scientific Reports. 7 (1) 10640. Bibcode:2017NatSR...710640L. doi:10.1038/s41598-017-10937-3. PMC 5587539. PMID 28878362.
- ^ "The Vibrance of Natural Color".
- ^ Cerda, Bayron (2016). "Natural dyes as sensitizers to increase the efficiency in sensitized solar cells". Journal of Physics. 720 (1) 012030. Bibcode:2016JPhCS.720a2030C. doi:10.1088/1742-6596/720/1/012030. S2CID 99322759.
- ^ Kushwaha, Reena (2013-11-04). "Natural Pigments from Plants Used as Sensitizers for TiO2 Based Dye-Sensitized Solar Cells". Journal of Energy. 2013: 1–8. doi:10.1155/2013/654953.
- ^ Vasiliev, Mikhail; et al. (2016), "Photonic microstructures for energy-generating clear glass and net-zero energy buildings", Scientific Reports, 6 (8): 4313–6, Bibcode:2016NatSR...631831V, doi:10.1038/srep31831, PMC 4994116, PMID 27550827
- ^ Davy, N.C.; et al. (2017), "Near-UV Organic Solar Cells Paired with Electrochromic Windows for Smart Management of the Solar Spectrum", Nature Energy, 2 (8): 17104, doi:10.1038/nenergy.2017.104, PMC 17104
- ^ West, Mike (November 1992). "Transparent PV Panel" (PDF). Energy Efficiency and Environmental News. Retrieved October 5, 2011.
- ^ a b c Traverse, Christopher J.; Pandey, Richa; Barr, Miles C.; Lunt, Richard R. (2017-10-23). "Emergence of highly transparent photovoltaics for distributed applications". Nature Energy. 2 (11): 849–860. Bibcode:2017NatEn...2..849T. doi:10.1038/s41560-017-0016-9. ISSN 2058-7546. S2CID 116518194.
- ^ a b Lunt, Richard R.; Bulovic, Vladimir (2011-03-14). "Transparent, near-infrared organic photovoltaic solar cells for window and energy-scavenging applications". Applied Physics Letters. 98 (11): 113305. Bibcode:2011ApPhL..98k3305L. doi:10.1063/1.3567516. hdl:1721.1/71948. ISSN 0003-6951.
- ^ Bailey-Salzman, Rhonda F.; Rand, Barry P.; Forrest, Stephen R. (2006-06-05). "Semitransparent organic photovoltaic cells". Applied Physics Letters. 88 (23): 233502. Bibcode:2006ApPhL..88w3502B. doi:10.1063/1.2209176. hdl:2027.42/87783. ISSN 0003-6951.
- ^ "Transparent, flexible solar cells combine organic materials, graphene electrodes". Main. 15 June 2017. Retrieved 2019-11-27.
- ^ Bailie, Colin D.; Christoforo, M. Greyson; Mailoa, Jonathan P.; Bowring, Andrea R.; Unger, Eva L.; Nguyen, William H.; Burschka, Julian; Pellet, Norman; Lee, Jungwoo Z.; Grätzel, Michael; Noufi, Rommel (2015-03-05). "Semi-transparent perovskite solar cells for tandems with silicon and CIGS". Energy & Environmental Science. 8 (3): 956–963. Bibcode:2015EnEnS...8..956B. doi:10.1039/C4EE03322A. ISSN 1754-5706. OSTI 1237896.
- ^ "Subsidies: France moves up, Netherlands down". Eugene Standard. 2006. Archived from the original on 2006-10-04. Retrieved 2008-10-26.
30 €ct per kilowatt-hour (40 €ct for Corsica) for twenty years, while an extra premium of 25 €ct/kWh is received for roof-, wall- or window-integrated PV. Moreover, individual households also can receive a 50% tax credit for their PV investments.
- ^ a b "CLER - Comité de Liaison Energies Renouvelables". CLER. 2008-06-03. Archived from the original on 2009-04-18. Retrieved 2008-10-26.
30 à 55* c€/kWh en France continentale
- ^ PV Subsidies: France up, Netherlands down | Leonardo ENERGY Archived February 3, 2008, at the Wayback Machine
- ^ "Feed-in Tariffs".
- ^ "DSIRE Home". dsireusa.org. 2011. Retrieved October 5, 2011.
- ^ "China launches "Golden Sun" subsidies for 500 MW of PV projects by 2012". snec.org.cn. SNEC PV. 2011. Archived from the original on July 7, 2011. Retrieved October 5, 2011.
China launched its much anticipated Golden Sun program of incentives for the deployment of 500 MW of large-scale solar PV projects throughout the country on July 21.
- ^ "The Golden Sun of China". pvgroup.org. PV Group. 2011. Archived from the original on February 5, 2010. Retrieved October 5, 2011.
- ^ Wang, Ucilia (November 16, 2009). "Here Comes China's $3B, 'Golden Sun' Projects". Greentech Media. Retrieved October 5, 2011.
- ^ Browse Conference Publications > Ecological Vehicles and Renew ... Help Working with Abstracts Back to Results Vehicle-integrated Photovoltaic (ViPV) systems: Energy production, Diesel Equivalent, Payback Time; an assessment screening for trucks and busses
- ^ From BIPV to Vehicle-Integrated Photovoltaics
- ^ Opportunities for Vehicle Integrated Photovoltaics
- ^ VIPV and infrared harvesting
- ^ Solar vehicles
- ^ a b c d e f g h Yang, Rebecca Jing; Zou, Patrick X.W. (2016-01-02). "Building integrated photovoltaics (BIPV): costs, benefits, risks, barriers and improvement strategy". International Journal of Construction Management. 16 (1): 39–53. doi:10.1080/15623599.2015.1117709. ISSN 1562-3599. S2CID 112302779.
- ^ Chen, Liutao; Yang, Jiachuan; Li, Peiyuan (2022-01-15). "Modelling the effect of BIPV window in the built environment: Uncertainty and sensitivity". Building and Environment. 208 108605. Bibcode:2022BuEnv.20808605C. doi:10.1016/j.buildenv.2021.108605. ISSN 0360-1323. S2CID 244502729.
- ^ Sharples, Steve; Radhi, Hassan (2013-07-01). "Assessing the technical and economic performance of building integrated photovoltaics and their value to the GCC society". Renewable Energy. 55: 150–159. Bibcode:2013REne...55..150S. doi:10.1016/j.renene.2012.11.034. ISSN 0960-1481.
Further reading
[edit]- Agrawal, Basant; Tiwari, G N (2011). Building Integrated Photovoltaic Thermal Systems. Cambridge, UK: Royal Society of Chemistry. ISBN 978-1-84973-090-7.
- Warrick, Joby (March 2015). "Utilities, sensing threat, put squeeze on booming solar roof industry". The Washington Post.
External links
[edit]- Building integrated photovoltaics an overview of the existing products and their fields of application
- Canadian Solar Buildings Research Network
- Building Integrated Photovoltaics
- EURAC Research Building Integrated Photovoltaic on-line platform
- 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.
Building-integrated photovoltaics
View on GrokipediaBuilding-integrated photovoltaics (BIPV) encompass photovoltaic modules designed to serve as principal structural or architectural elements of a building, such as roofing, facades, or glazing, thereby generating electricity while fulfilling conventional building material functions like weatherproofing and shading.[1][2] This integration distinguishes BIPV from add-on solar systems by eliminating the need for separate mounting structures, potentially offsetting some installation costs through multifunctional design.[3] Emerging in prototype form during the 1980s for residential applications, BIPV technology advanced through the 1990s with commercial implementations in facades and roofs, driven by improvements in photovoltaic efficiency and material durability.[4][5] Notable achievements include diverse product forms like opaque panels, semi-transparent windows, and solar tiles, enabling aesthetic versatility in modern architecture while contributing to on-site renewable energy production.[2][6] Despite benefits such as decentralized power generation that reduces grid dependency and transmission inefficiencies, BIPV systems face challenges including elevated upfront costs—often 20-50% higher than conventional rack-mounted photovoltaics—due to customized engineering and potentially compromised module efficiency from architectural compromises.[1][7] Durability concerns in harsh environments and the need for interdisciplinary expertise in design and installation further complicate widespread adoption, though ongoing research in thin-film and bifacial technologies aims to enhance performance metrics.[6][8] Empirical assessments indicate that while BIPV can achieve payback periods comparable to traditional systems in high-insolation regions, real-world yield variations underscore the importance of site-specific modeling over generalized sustainability claims.[9]
Definition and Principles
Core Concepts and Distinctions from Traditional PV
Building-integrated photovoltaics (BIPV) consist of photovoltaic modules engineered to serve as multifunctional building envelope components, generating electricity while fulfilling structural, cladding, or glazing roles such as roofs, facades, or windows.[2] These systems replace conventional construction materials, thereby integrating power production directly into architectural design without requiring separate mounting hardware.[10] The core concept emphasizes duality: photovoltaic functionality combined with building performance attributes like weather resistance, thermal regulation, and visual aesthetics.[11] At the fundamental level, BIPV operates on the photovoltaic effect, where incident solar radiation excites electrons in semiconductor materials—typically silicon or thin-film variants—to produce direct current. However, integration necessitates adaptations such as encapsulation for durability, custom geometries for curvature or transparency, and compliance with building codes for load-bearing or fire safety, distinguishing these modules from standalone PV designs optimized solely for energy yield.[9] This approach enables seamless incorporation into new constructions or retrofits, potentially enhancing overall building energy efficiency by minimizing transmission losses from remote panel locations.[12] In contrast to traditional PV systems, which are add-on installations like rooftop racks or ground mounts that supplement rather than supplant building elements, BIPV eliminates dedicated support structures, reducing balance-of-system costs and spatial demands. Traditional systems, often termed building-applied photovoltaics (BAPV), prioritize high-efficiency, flat-panel arrays for maximal irradiance capture but incur extra expenses for framing, wiring, and elevation above surfaces.[2] BIPV, by serving as envelope substitutes, can offset material procurement costs—such as for tiles or glazing—though architectural imperatives may yield lower module efficiencies due to factors like suboptimal orientations, shading from integration, or material compromises for translucency.[13] Empirical assessments indicate BIPV power outputs vary widely, with facade integrations typically generating less per unit area than optimally tilted traditional panels, reflecting trade-offs between energy production and holistic building value.[14]Underlying Photovoltaic Technologies
![United Solar Ovonic thin-film PV building-integrated solar shingles.jpg][float-right] Building-integrated photovoltaics (BIPV) rely on established photovoltaic technologies adapted for architectural integration, primarily crystalline silicon (c-Si) cells and thin-film semiconductors. Crystalline silicon cells, manufactured from sliced silicon wafers, dominate due to their high efficiency and proven durability, while thin-film variants offer advantages in flexibility and aesthetics essential for seamless building envelope incorporation.[1][3] Crystalline silicon encompasses monocrystalline and polycrystalline subtypes. Monocrystalline silicon cells, grown from a single crystal, achieve commercial module efficiencies of 18-22% as of 2023, benefiting from uniform charge carrier mobility that minimizes recombination losses. Polycrystalline silicon, cast from melted silicon into blocks, yields efficiencies of 15-18%, with cost savings from simpler production but slightly reduced performance due to grain boundaries scattering electrons. In BIPV, c-Si cells power rigid facade panels and roofing elements, where their thermal stability—retaining over 80% efficiency after 25 years—supports long-term building energy generation, though added weight requires reinforced mounting.[1][15] Thin-film solar cells, fabricated by depositing micrometer-thick semiconductor layers onto glass, metal, or flexible substrates, include amorphous silicon (a-Si), cadmium telluride (CdTe), and copper indium gallium selenide (CIGS). Amorphous silicon, with efficiencies of 6-10%, suits BIPV for its low-light responsiveness and potential semi-transparency via laser-scribed patterns, enabling window integrations without full opacity. CdTe thin-films reach 18-22% efficiency in optimized modules, leveraging abundant materials and high absorption coefficients for compact designs, as commercialized by First Solar since 2005. CIGS offers 15-17% efficiency with flexibility for curved surfaces, its chalcopyrite structure providing tolerance to defects and suitability for lightweight BIPV shingles or facades. These technologies reduce material use by over 90% compared to c-Si wafers, easing installation on weight-sensitive structures, though they exhibit higher temperature coefficients, degrading output by 0.3-0.4% per °C rise.[1][3][15]| Technology | Efficiency Range (Commercial Modules) | Key BIPV Advantages | Limitations |
|---|---|---|---|
| Monocrystalline Si | 18-22% | High power density, longevity | Rigidity, higher weight |
| Polycrystalline Si | 15-18% | Lower cost, scalable production | Lower efficiency, visible grain patterns |
| Amorphous Si | 6-10% | Low-light performance, semi-transparent | Lower efficiency, light-induced degradation |
| CdTe | 18-22% | Low material cost, high absorption | Toxicity concerns in manufacturing |
| CIGS | 15-17% | Flexibility, aesthetics | Scalability challenges |
Historical Development
Early Concepts and Prototypes (1970s–1990s)
The concept of building-integrated photovoltaics (BIPV) emerged in the 1970s amid the oil crises, prompting U.S. government initiatives to explore distributed photovoltaic systems for buildings, including designs that incorporated PV elements into structures rather than as add-ons.[16] In 1973, the University of Delaware constructed "Solar One," a residence featuring roof-integrated PV arrays combined with thermal collection, marking an early prototype that generated electricity while contributing to passive solar heating.[17] These efforts focused on polycrystalline silicon modules, with initial capacities in the low kilowatt range, driven by demonstrations at institutions like MIT to assess feasibility for residential and small-scale building applications.[16] By the early 1980s, prototypes advanced toward true integration, with the Carlisle House in Massachusetts completed in 1980 as the first documented BIPV system, utilizing a 7.5-peak-watt array of Solarex polycrystalline modules embedded in the building envelope.[16] DOE-sponsored evaluations of similar prototypes from 1979–1983 at test stations in Massachusetts and Florida tested durability and performance of PV-integrated roofing and facades, revealing challenges like thermal expansion mismatches between silicon cells and building materials.[18] In Europe, the 1982 Wohnanlage Richter project near Munich integrated crystalline silicon cells into a glazed building skin, representing one of the earliest facade integrations for aesthetic and functional purposes.[19] The late 1980s and 1990s saw prototypes scaling up, with the U.S. DOE's Building Opportunities with New Options for Utility-Scale (BONUS) program developing PV roofing shingles and facade glazing modules by the early 1990s, emphasizing multifunctional elements that replaced conventional materials.[19] A 1991 installation in Aachen, Germany, integrated PV into a curtain wall facade with insulation glazing, producing approximately 100 kWp and serving as a benchmark for semi-transparent applications.[20] These efforts highlighted causal trade-offs, such as reduced efficiency from encapsulation needs (typically 10–15% lower than standalone panels) but gains in overall building energy balance through shading and reduced material use.[21] By 1998, innovations like flexible solar shingles by Subhendu Guha enabled shingle-integrated prototypes for sloped roofs, paving the way for commercial viability.[16] In the UK, the CIS Tower in Manchester retrofitted PV panels into its cladding starting in 1993, generating 200 kWp and demonstrating large-scale facade integration on an existing high-rise, though primarily as a proof-of-concept amid high costs exceeding £1 million per MW.[19] Such prototypes underscored empirical limitations, including suboptimal orientations on vertical surfaces (yielding 20–30% less output than optimal tilt) and dependency on government subsidies for economic feasibility, as module prices hovered around $10–20 per watt.[21] Overall, 1970s–1990s developments transitioned from experimental roof hybrids to multifunctional prototypes, informed by first-hand performance data from field trials rather than theoretical models.Commercialization and Key Milestones (2000s–Present)
The commercialization of building-integrated photovoltaics (BIPV) gained momentum in the early 2000s, propelled by policy incentives in Europe that differentiated BIPV from conventional rooftop PV through premium feed-in tariffs and subsidies. Germany's Renewable Energy Sources Act of 2000 established feed-in tariffs for PV systems, encouraging integration into building envelopes as part of broader solar expansion, with BIPV representing a niche but growing segment amid falling module costs.[19] Italy's Conto Energia program, launched in 2005, offered elevated tariffs—reaching 0.44–0.49 €/kWh for BIPV by 2007—spurring facade and roofing integrations in commercial and residential projects.[19] France followed with a BIPV-specific premium to its feed-in tariff in 2006, while Switzerland introduced a similar incentive in 2009, collectively driving early adoption despite higher upfront costs averaging 8.75 $/Wp in 2003.[19] Key early projects exemplified this shift, such as the Beddington Zero Energy Development (BedZED) in the UK, completed in 2002, which integrated PV elements into sustainable housing and earned recognition for advancing multifunctional building designs.[19] In Australia, the first commercial BIPV facade appeared in an educational building in 2000, marking initial non-European progress.[22] By the late 2000s, Europe saw hundreds of installations, though BIPV comprised only about 1% of global distributed PV capacity in 2009, limited by customization challenges and premium pricing over standard modules.[19] Cumulative European BIPV capacity reached 6.9 GWp by 2019, led by Italy (38%) and France (35%), reflecting policy-driven scaling in urban and institutional applications.[19] The 2010s marked expanded commercialization through technological maturation and high-profile innovations. Italy refined its BIPV definition in 2011 to encompass partial integrations, boosting eligibility for incentives, while France initiated tariffs for innovative BIPV systems.[19] In Switzerland, projects like the multifamily housing in Brütten (2016), featuring a 550 €/m² BIPV facade enabling full energy autarky, and the Grosspeter Tower (2017), a solar-active skyscraper, demonstrated aesthetic and performance viability.[19] Tesla's unveiling of its Solar Roof in October 2016 introduced scalable, shingle-like BIPV for residential markets, positioning it as a direct replacement for traditional roofing with integrated PV generation, though initial deployments were limited to pilots.[23] Into the 2020s, BIPV adoption has accelerated with cost reductions—e.g., module prices to 375 €/m² by 2019—and EU directives like the Energy Performance of Buildings Directive emphasizing net-zero standards.[19] Annual European installations hovered around 150 MWp in 2020, with projections for doubling within five years amid mass customization advances from firms like Onyx Solar, specializing in PV glass facades since the mid-2000s.[19] In the US, federal and state incentives, including California's solar mandates, have supported commercial facades and canopies, though Europe remains dominant; global market analyses forecast BIPV revenue growth from approximately $14 billion in 2020 to higher figures by 2030, driven by efficiency gains in thin-film and crystalline technologies.[9][24] Despite progress, barriers like higher initial costs (150–200% over conventional PV) persist, confining widespread commercialization to premium or policy-subsidized segments.[19]Types and Forms of BIPV
Opaque BIPV Systems
Opaque building-integrated photovoltaics (BIPV) systems embed photovoltaic modules directly into non-transmissive building envelope elements, such as roofs, facades, and spandrel panels, enabling them to serve as structural cladding or roofing while generating electricity. These systems differ from traditional add-on solar panels by forgoing separate mounting racks, which reduces installation costs and material layers, though they may incur higher upfront expenses due to customized integration. Common technologies include crystalline silicon (c-Si) modules for their established efficiency and thin-film variants like copper indium gallium selenide (CIGS) or cadmium telluride (CdTe) for flexibility in curved or lightweight applications.[1][3] In roofing applications, opaque BIPV manifests as photovoltaic shingles, tiles, or flexible laminates that replicate conventional materials like asphalt shingles, ceramic tiles, or standing-seam metal, directly replacing the waterproofing layer. Efficiencies for such shingle systems typically range from 14% to 18%, comparable to standard rooftop PV but with added durability against foot traffic and weather exposure. Thin-film options, such as amorphous silicon (a-Si) rolls, suit low-slope or irregular roofs, providing uniform aesthetics and lower weight. These configurations minimize thermal bridging and enhance building insulation when combined with underlying membranes.[1][25][3] Facade-integrated opaque BIPV employs PV panels as cladding in ventilated systems, curtain walls, or solid infill panels, often with glass fronts for protection and visual appeal, including colored or textured finishes to match architectural designs. These setups can incorporate multi-crystalline c-Si cells, as seen in the Paul Horn Arena in Germany, where a 530 m² south-facing facade with emerald-green modules generates 43.7 kWp. Similarly, the Beit Havered building in Israel features a 608 m² c-Si facade with digital printing, projected to yield 1,938,623 kWh over 35 years. By shading interiors, such systems reduce cooling loads, with studies indicating positive return on investment even for suboptimal orientations like north-facing walls.[1][26] Overall, opaque BIPV prioritizes robustness and multifunctionality, with thin-film technologies enabling bespoke forms like bent panels for non-planar surfaces, though c-Si dominates for higher output in space-constrained urban settings. Durability aligns with building lifespans, often exceeding 25 years, supported by encapsulation that resists hail and UV degradation.[3][1]Semi-Transparent and Translucent BIPV
Semi-transparent and translucent building-integrated photovoltaics (BIPV) employ photovoltaic materials designed to permit partial visible light transmission, facilitating their incorporation into fenestration systems like windows, curtain walls, and skylights. These modules typically achieve average visible transmittance (AVT) levels of 10-80%, with optimal ranges around 45-55% for balancing daylighting, solar heat gain reduction, and electricity yield. Unlike opaque BIPV, they prioritize multifunctionality, including passive shading and aesthetic uniformity, though at the cost of reduced photovoltaic efficiency due to the transparency trade-off.[27] Primary technologies include thin-film variants such as amorphous silicon (a-Si) and copper indium gallium selenide (CIGS), which enable homogeneous transparency via inherent material properties or laser scribing, yielding efficiencies of 6-10% and AVT up to 30%. Dye-sensitized solar cells (DSSC) support higher transmittance (10-50%) but lower efficiencies around 5-8%, while emerging perovskite cells demonstrate potential for 13-25% efficiency with 30-77% transmittance in laboratory settings. Crystalline silicon (c-Si) achieves semi-transparency through cell spacing in glazing units, producing non-uniform light patterns but leveraging higher base efficiencies (19-22%) with 10-30% transparency losses.[27][2] These systems reduce solar heat gain coefficients (SHGC) to 9-12% and support overall building energy savings of 18-59% by combining power generation with daylight control and lower cooling demands. For instance, the Energiewürfel building in Konstanz, Germany, integrates semi-transparent modules for filtered sunlight and shading benefits. In the Ludesch Community Centre, Austria, translucent BIPV covers a plaza area, demonstrating architectural versatility.[1][1] Notable implementations include the San Antón Market in Spain (2010), featuring 168 m² of a-Si skylights with 20% transmittance, generating 7,700 kWh annually and achieving return on investment under two years. The Azurmendi Restaurant in Spain (2015) employs 270 m² of a-Si in skylights and curtain walls, delivering 55% energy use reduction through integrated daylighting and power output. Palazzo Lombardia in Milan, Italy (2011), uses m-Si curtain walls over 1,420 m² with 34% transmittance, producing 73.5 kWh/m² yearly.[2][2][2] Challenges encompass efficiency penalties (e.g., 5-15% losses from patterning or coloring), potential glare or illuminance reductions indoors—particularly in low global horizontal irradiance (GHI) climates—and modeling complexities for optical-thermal-electrical interactions. Durability concerns, such as stability in organic or perovskite layers, persist, though thin-film options offer uniform views and color rendering indices (CRI) above 80 when designed appropriately. Ongoing research addresses these via synergistic systems, like BIPV coupled with air treatment for visual comfort.[27][2][28]Specialized Forms and Hybrid Integrations
Specialized forms of building-integrated photovoltaics (BIPV) include thin-film solar shingles and flexible PV membranes designed to mimic traditional roofing materials while generating electricity. These products, such as those developed under early U.S. Department of Energy programs, utilize amorphous silicon tandem-junction modules encapsulated in materials compatible with roofing applications, allowing field application over metal roofs or as standalone shingles.[29] Solar shingles typically exhibit lower module efficiencies compared to conventional rack-mounted PV systems, often due to compromises in cell design for aesthetic and structural integration.[9] Hybrid integrations in BIPV primarily encompass photovoltaic-thermal (PV/T) systems, which couple PV modules with thermal collectors to harvest both electrical and thermal energy from the same surface area. These systems mitigate PV efficiency losses from elevated operating temperatures by extracting heat via circulating fluids, such as air or water, thereby enhancing overall energy yield for building applications like facades and roofs.[30] Early prototypes, including the Phototherm Module developed in collaboration with Solar Design Associates and SunEarth, integrated PV laminates with unglazed polymer collectors for domestic hot water production, demonstrating feasibility in residential settings.[29] More recent advancements feature BIPV/T configurations classified by collector type (e.g., sheet-and-tube, channel-type) and integration method, contributing to net-zero building goals by addressing up to 40% of sectoral energy demand.[30] A notable example is the building-integrated hybrid PV-T window (PVTW), fabricated in 2024 with a semi-transparent amorphous silicon PV layer and a water-based thermal absorber clamped between low-iron glass panels.[31] Tested outdoors in London during July 2021 under solar irradiance up to 1100 W/m², the PVTW achieved an electrical efficiency of 3.6% and thermal efficiency of 10.7% at a 30° inclination, with water temperatures reaching approximately 50°C.[31] At steeper angles, thermal efficiency improved to 17.6%, outperforming standalone solar-thermal windows by about 10% in heat output while adding electricity generation.[31] Such hybrids require advancements in manufacturing process control and material durability to meet building codes and PV standards simultaneously.[29]Integration Methods and Applications
Facade and Envelope Integration
Facade and envelope integration in building-integrated photovoltaics (BIPV) involves incorporating photovoltaic modules directly into vertical building surfaces, such as walls and cladding systems, to serve dual roles in weather protection, structural support, and electricity generation. Common configurations include rainscreen facades with ventilated cavities exceeding 100 mm, curtain walls using stick or unitized systems with pressure-equalized joints, and double-skin facades that enhance airflow for cooling. These methods employ reversible mechanical fastenings like screws or bolts to facilitate maintenance and replacement.[2] Dominant technologies feature crystalline silicon (c-Si) modules, holding over 95% market share with efficiencies of 19-22% under standard test conditions (STC), often in opaque monocrystalline form for cladding. Thin-film options, comprising about 5% of the market, include amorphous silicon (a-Si) at 6-8% efficiency and copper indium gallium selenide (CIGS) at 12-19%, prized for flexibility, lighter weight, and semi-transparency up to 30% via laser patterning, suitable for aesthetic and daylighting applications in envelopes. Bifacial c-Si variants capture rear-side irradiance, boosting yields in reflective environments.[2] Performance yields from facades typically range 35-45% below optimally tilted roofs due to suboptimal orientations and shading, with specific outputs like 73.5 kWh/m² annually for semi-transparent c-Si curtain walls or 102 kWh/m² for shading-integrated systems. Ventilated designs mitigate module temperatures (25-60°C range), reducing efficiency losses by up to 15°C compared to sealed systems, while maintaining thermal transmittance (U-values) akin to conventional glazing at around 1.3 W/m²K. Energy payback times stand at 0.9-1.3 years, with performance ratios exceeding 74% in well-designed installations.[2] Challenges encompass higher upfront costs for custom integration, thermal expansion mismatches requiring robust mounting, wind load resistance, and fire safety compliance, where standards lag for non-combustible PV materials in high-rises. Soiling and partial shading further demand optimizers or bypass diodes, while facade-specific degradation may accelerate without proper moisture control.[2] Notable implementations include the Palazzo Lombardia in Milan, Italy (2011), featuring 1,420 m² of semi-transparent monocrystalline silicon curtain walls generating 104.4 MWh annually from 170.4 kWp. In Berlin, Germany, a full-scale CIGS ventilated curtain wall (circa 2022) with 360 modules at 12.3% efficiency yielded 83.6 kWh/m² yearly across south-, west-, and north-facing orientations, demonstrating minimal impact from air gap variations (50-150 mm) but highlighting shading losses from adjacent structures. These cases underscore facade BIPV's viability for urban decarbonization, with payback periods of 2-17 years depending on incentives and self-consumption rates.[2][32]Roofing, Shading, and Structural Elements
Building-integrated photovoltaics (BIPV) in roofing applications replace conventional materials like asphalt shingles, metal seams, or tiles with photovoltaic modules that serve dual purposes of weather protection and electricity generation. Common forms include solar shingles, tiles, and thin-film laminates on standing seam roofs, which integrate seamlessly without additional mounting structures.[1][33] Crystalline silicon modules in these systems typically deliver approximately 20 W/ft², while overall efficiencies range from 15% to 18% depending on module type and environmental conditions.[1][34] Installation on new roofs requires about 3.5 worker-hours per kW, compared to 6.9 for rack-mounted PV, due to integrated supply chains and reduced flashing needs.[33] BIPV shading elements, such as awnings, canopies, and louvers, provide solar control to mitigate overheating while harvesting energy, often reducing building cooling loads through semi-transparent or adjustable designs. Parametric optimization of flexible photovoltaic shading devices (PVSDs) enhances multi-objective performance, balancing energy yield with shading effectiveness via shape and orientation adjustments.[35][36] For instance, a 350 m² photovoltaic canopy at Ludesch Community Centre generates 16,000 kWh annually, demonstrating combined shading and power benefits.[1] Copper indium selenide (CIS) BIPV shading has been shown to lower life-cycle environmental impacts by improving overall building energy efficiency.[37] In structural applications, BIPV roofing and shading components act as load-bearing envelope elements, offering insulation, waterproofing, and durability equivalent to traditional materials. These systems are engineered to withstand environmental stresses like wind, rain, and snow, with projections for leak-free performance over 20 years under standard maintenance.[38][39] Long-term monitoring of over 50 Swiss BIPV installations, including shading-integrated systems, reveals year-on-year performance ratios influenced by partial shading, with degradation accelerated by environmental exposure but mitigated through proper design.[40][41] Such integrations enhance building resilience, as BIPV elements provide superior fire, water, and structural resistance compared to add-on panels.[42]Emerging Application Contexts
BIPV systems are increasingly applied in agrivoltaic greenhouses, where semi-transparent photovoltaic glazing replaces traditional covers to enable dual crop cultivation and electricity generation. In such setups, modules transmitting 30-50% of photosynthetically active radiation (PAR) support plant growth while yielding 200-600 kWh/m² annually, as demonstrated in tomato greenhouse trials with no adverse yield impacts compared to polyethylene films.[43] Quantum dot-enhanced BIPV glass optimizes spectral transmission for crops like lettuce, reducing operational energy costs by up to 40% through on-site power for lighting and ventilation.[44] These applications, piloted in Europe since 2022, address land-use conflicts by integrating vertical farming with renewables, though optimal transmittance remains site-specific to latitude and crop type.[45] Transparent and semi-transparent BIPV windows represent a burgeoning context for high-rise and commercial buildings, generating power from facades without compromising daylighting. Recent perovskite-based cells achieve 12-15% efficiency with 20-40% visible light transmittance, enabling net-zero energy facades that offset 10-20% of building loads.[46] In smart window integrations, these systems dynamically tint for glare control while exporting surplus energy, as tested in prototypes yielding 100-150 kWh/m² yearly in urban settings.[47] Deployment challenges include durability against weathering, but advancements since 2023 have extended lifespans to 25 years, positioning them for widespread adoption in retrofits.[48] Integration with electric vehicle (EV) charging infrastructure emerges as a key urban application, where BIPV facades and canopies power on-site stations, reducing grid dependence by 30-50% in residential and commercial buildings. Malaysian case studies show rooftop BIPV systems delivering 5-10 kW for Level 2 chargers, with annual outputs covering 20-40 EV charges per household.[49] In dedicated stations, bifacial modules on noise-integrated structures generate 140-200 kWh/m², slashing emissions by 160 metric tons CO₂e over 20 years compared to grid-sourced power.[50] This synergy, accelerated by policies post-2020, enhances energy autonomy but requires storage to match EV demand peaks.[51] Photovoltaic noise barriers (PVNBs) along highways and rail lines constitute an innovative infrastructure context, combining acoustic attenuation with power production in dense urban areas. Bifacial PV modules mounted on barriers yield 150-250 kWh/m² annually, with rear-side gains from reflected light boosting output by 20-30% over monofacial designs.[52] European installations since 2024 demonstrate noise reduction equivalent to standard barriers (10-20 dB) while feeding grids or nearby facilities, potentially powering 1-2 million households if scaled nationwide.[53] Economic viability hinges on subsidies, with levelized costs of energy (LCOE) at 0.05-0.08 €/kWh, though soiling and orientation constraints limit efficacy in shaded corridors.[54]These contexts underscore BIPV's shift toward multifunctional urban elements, driven by efficiency gains in thin-film and perovskite technologies since 2023, though scalability depends on standardized testing for fire safety and aesthetics.[6] Prefabricated active facades with embedded BIPV further enable rapid deployment in modular construction, optimizing for bidirectional energy flows in smart grids.[55]
Performance Characteristics
Efficiency Metrics and Output Factors
The efficiency of building-integrated photovoltaics (BIPV) is typically quantified through module-level peak efficiency under standard test conditions (STC, defined as 1000 W/m² irradiance, 25°C cell temperature, and AM1.5 spectrum), alongside system-level metrics that account for real-world output factors such as orientation, temperature, and integration-specific losses. Crystalline silicon-based BIPV modules commonly achieve 15-20% peak efficiency, comparable to rack-mounted photovoltaic (PV) systems, while thin-film variants like amorphous silicon (a-Si) or copper indium selenide (CIS) range from 8-12% due to inherent material limitations but offer advantages in low-light performance or semi-transparency.[2] [56] Annual coverage-area efficiencies for vertically mounted BIPV panels, however, drop significantly to 4.6-12.2% owing to reduced irradiance capture compared to optimally tilted rooftop arrays, which can exceed 15% in equivalent metrics.[57] Key output metrics include the performance ratio (PR), defined as the ratio of actual AC energy output to the theoretical DC output under equivalent irradiance, and specific yield (kWh/kWp), which normalizes annual energy production to installed capacity. BIPV systems exhibit PR values of 70-85%, with monocrystalline silicon facades reaching up to 82.9% and CIS-based integrations averaging 72.8%; these are generally 5-15% lower than traditional rooftop PV due to suboptimal tilt angles (e.g., 90° vertical facades) and higher module temperatures from reduced airflow.[58] [56] [59] Vertically installed bifacial BIPV can mitigate losses, retaining approximately 82% of the yield from tilted systems through rear-side irradiance gains, though overall specific yields for facade integrations remain 50-70% of optimal rooftop benchmarks in mid-latitude climates.[60] Influencing factors on output include temperature coefficients, typically -0.3% to -0.5% per °C above 25°C, amplified in BIPV by encapsulation and proximity to building envelopes, leading to 10-20°C higher operating temperatures than ventilated rack systems and corresponding 5-10% power derating.[61] Degradation rates average 0.5-1% annually for silicon-based BIPV, similar to conventional PV, but thin-film options may experience 1-2% initial light-induced degradation (LID) or higher rates in humid environments; empirical data from long-term installations confirm cumulative losses of 10-20% over 20-25 years.[18] [62] Additional derates arise from soiling (1-3% annual loss without cleaning), module mismatch in non-uniform facades (2-5%), and inverter efficiencies (95-98%), collectively reducing PR by 10-20% relative to idealized models; bifacial and tracking hybrids can offset these through enhanced albedo utilization.[63] [64]| Metric | Typical BIPV Range | Comparison to Traditional PV | Key Influencing Factor |
|---|---|---|---|
| Peak Module Efficiency | 15-20% (c-Si); 8-12% (thin-film) | Comparable | Material type[2] |
| Performance Ratio | 70-85% | 5-15% lower | Orientation and temperature[58] [60] |
| Annual Specific Yield (vertical facade) | 200-600 kWh/kWp | 50-70% of tilted rooftop | Irradiance angle and shading[57] |
| Temperature Coefficient | -0.3% to -0.5%/°C | Similar, but higher effective losses | Ventilation constraints[61] |
| Degradation Rate | 0.5-1%/year | Comparable; higher for some thin-film | Exposure and encapsulation[18] |
Durability, Degradation, and Reliability Data
Field studies on building-integrated photovoltaics (BIPV) indicate annual degradation rates generally comparable to those of rack-mounted photovoltaic systems, typically in the range of 0.5% to 1% per year, though integration-specific factors such as elevated operating temperatures and mechanical stresses can introduce variability. A comprehensive analysis of 55 rooftop BIPV installations in Switzerland, monitored over 5 to 10 years, reported a median year-on-year performance loss rate (PLR) of 0.06%, suggesting negligible average degradation, but with a broad spread across systems highlighting the influence of site-specific conditions like shading and soiling.[40][65] Similarly, a four-year outdoor exposure test of a glass/EVA/back-sheet BIPV module using PERC cells yielded a total performance degradation of only 0.8%, attributed to robust encapsulation mitigating environmental stressors.[66] BIPV durability is challenged by building envelope constraints, including reduced airflow leading to higher module temperatures—often 10–20°C above standard PV arrays—which accelerate mechanisms such as thermal cycling, potential-induced degradation (PID), and encapsulant discoloration. Reliability assessments emphasize that while crystalline silicon-based BIPV modules demonstrate field survival rates exceeding 95% over 10–20 years when adhering to IEC 61215 standards adapted for building loads, facade-integrated systems face elevated risks of microcracking from structural flexing and moisture ingress at edges.[14][67] Long-term data from U.S. and European deployments, including NIST-monitored sites, show median fleet degradation remaining flat after 5–10 years, but outliers with rates up to 2%/year underscore the need for enhanced ventilation and bypass diodes to maintain output.[68]| Study | Systems Analyzed | Duration | Median Degradation Rate (%/year) | Key Factors Noted |
|---|---|---|---|---|
| Swiss Rooftop BIPV (SUP SI/EPFL) | 55 | 5–10 years | 0.06 | Large variability; minimal average loss despite shading/soiling |
| PERC BIPV Module Outdoor Test | 1 (glass/EVA/BS) | >4 years | ~0.2 (cumulative 0.8%) | Encapsulation effectiveness against UV/thermal stress |
| Global PV Fleet (incl. BIPV subsets, NREL/NIST) | Multiple | 5–10 years | ~0.5 (flat median) | Heat buildup in integrated setups; spread due to installation quality |
Economic Analysis
Cost Structure and Comparisons to Conventional Systems
The capital costs of building-integrated photovoltaics (BIPV) are dominated by customized photovoltaic modules engineered for architectural compatibility, including adaptations for transparency, curvature, or color that increase fabrication expenses over standard silicon panels. These modules, often glass-glass or thin-film variants, contribute the largest share, with full facade systems priced at €200–€625 per m², while roofing integrations range from €134/m² for thin-film to higher for structural elements like balconies at €520/m². Additional components include specialized framing for load-bearing integration, electrical wiring embedded in envelopes, and compliance with building codes for fire safety and wind resistance, which can elevate total upfront costs by 20–50% per watt-peak relative to rack-mounted PV systems due to lower module efficiencies (typically 10–15% vs. 20%+ for conventional panels) and bespoke manufacturing. Installation labor, however, may be lower for BIPV in new construction at 3.5 worker-hours/kW compared to 6.9 for racked PV on existing roofs, as integration streamlines workflows by combining envelope and PV assembly. Operational costs mirror those of standard PV, at under 1% of capital annually for cleaning and inverter upkeep, though integrated designs can reduce access-related maintenance expenses over 25–30-year lifespans.| Application | BIPV Cost Range | Conventional Envelope Cost Range |
|---|---|---|
| Facades (glass-glass modules) | €95–€380/m² | €400–€1,000+/m² (windows); €520–€1,120/m² (curtain walls)[70] |
| Roofing (thin-film integrated) | €134/m² | €25–€175/m²[70] |
| Specific products (e.g., eFacade) | $79–$138.50/sqft pre-incentives | $12–$35/sqft (brick); $50–$120/sqft (glass curtain wall)[71] |
Payback Periods, LCOE, and Viability Assessments
Payback periods for building-integrated photovoltaics (BIPV) systems, calculated as the time required to recover initial investment through energy savings or revenue, vary significantly based on location, system design, electricity tariffs, and incentives. In favorable climates with high solar irradiance and supportive policies, such as Mediterranean regions, discounted payback times can be as low as 6–12 years, particularly when BIPV displaces conventional building materials like cladding or roofing, thereby reducing net capital outlay.[24] [75] However, empirical studies in less optimal conditions, such as northern latitudes or without subsidies, report periods exceeding 20 years, often due to higher integration costs and lower output from non-optimal orientations like vertical facades.[14] For solar siding applications in the U.S., simple payback ranges from 9–13 years, influenced by local rates and incentives.[76] The levelized cost of energy (LCOE) for BIPV, which accounts for lifetime costs divided by energy produced, typically falls between 3.2 and 13.9 U.S. cents per kWh in sunny regions like the Mediterranean, making it competitive with fossil fuel-generated electricity but higher than utility-scale rack-mounted PV.[75] In residential U.S. contexts, unsubsidized BIPV LCOE ranges from $0.18 to $0.24/kWh, comparable to or slightly varying from traditional PV depending on technology—crystalline silicon derivatives may achieve 7% lower LCOE through material offsets, while thin-film options like CIGS or a-Si show 2–5% higher values due to performance trade-offs. Compared to standard rooftop PV, BIPV LCOE is often 2–3 times higher (e.g., $0.077/kWh for BIPV versus $0.023/kWh for rooftop), attributable to custom fabrication, reduced efficiencies from aesthetic constraints, and installation complexities, though dual-use credits for envelope replacement can narrow the gap.[77] Viability assessments of BIPV emphasize its economic potential in scenarios where architectural integration provides added value beyond energy production, such as in net-zero buildings where benefit-cost ratios reach 3.35 through combined energy revenue and material savings.[75] However, without feed-in tariffs, tax credits, or high retail electricity prices, many projects exhibit negative net present value or extended paybacks, limiting adoption to premium or policy-driven markets.[78] Recent analyses confirm that falling module prices improve prospects, but BIPV's viability hinges on site-specific factors like irradiance and orientation, with facade systems often underperforming relative to rooftops; holistic evaluations recommend prioritizing rooftop or optimally tilted integrations for better returns unless aesthetic or space constraints justify premiums.[79]Environmental Impact Assessment
Lifecycle Analysis Framework
The lifecycle analysis (LCA) framework for building-integrated photovoltaics (BIPV) adheres to the ISO 14040 and ISO 14044 standards, which establish principles, requirements, and guidelines for evaluating the environmental impacts of products and systems from cradle to grave.[80] These standards divide LCA into four iterative phases: goal and scope definition, life cycle inventory (LCI) analysis, life cycle impact assessment (LCIA), and interpretation, ensuring transparency, completeness, and consistency in methodology.[81] For BIPV, the goal and scope must address multifunctionality, where systems provide both electricity generation and building envelope services (e.g., weather protection, shading), necessitating clear definition of system boundaries that include displaced conventional materials like cladding or roofing to credit avoided impacts.[81] System boundaries in BIPV LCA typically span cradle-to-grave stages: raw material extraction and processing (A1), manufacturing (A2-A3), transport (A4), installation (A5), use phase with operation and maintenance (B1-B7, including degradation and output modeling), end-of-life deconstruction, waste processing, and disposal (C1-C4), plus potential recycling benefits (D).[81] The functional unit is standardized as 1 kWh of alternating current (AC) electricity delivered to the grid or end-user, allowing comparability across PV configurations while incorporating BIPV-specific factors like irradiation modeling via tools such as PVsyst and assumptions on system lifetime (e.g., 30 years for modules, 15-30 years for inverters, up to 60 years for structural elements).[81] Inventory data combine primary sources for foreground processes (e.g., BIPV module fabrication) with secondary databases like ecoinvent for background processes, emphasizing country-specific electricity mixes (average or marginal) for use-phase credits from avoided grid emissions.[81] Multifunctionality in BIPV requires allocation methods to partition environmental burdens between electricity production and building functions; recommended approaches attribute impacts from active PV components (e.g., semiconductors) to energy output, while passive elements (e.g., glass, framing) are allocated to envelope roles, or use system expansion/substitution to account for replaced materials.[81] Impact assessment employs categories such as global warming potential (GWP100 in kg CO₂ eq), cumulative energy demand (CED), acidification, eutrophication, human toxicity, resource scarcity, and water use (via AWARE method), with mandatory inclusion of climate change and optional others based on relevance.[81] Interpretation involves sensitivity analyses for key parameters like recycling rates (defaulting to recycled content credits) and degradation rates (typically 0.5-1% annually), highlighting uncertainties in long-term performance and end-of-life recovery, which can reduce net impacts by 10-20% through material reuse.[81] This framework reveals that BIPV often exhibits higher initial embodied impacts than rack-mounted PV due to integration materials but achieves environmental parity or superiority when envelope substitution and extended building lifetimes are factored in.[81]Empirical GHG Emissions, Resource Use, and Net Effects
Lifecycle greenhouse gas (GHG) emissions for building-integrated photovoltaics (BIPV) systems, assessed via life cycle analysis (LCA), typically range from 40 to 200 g CO₂ eq/kWh of electricity generated, with crystalline silicon modules yielding 70–120 g CO₂ eq/kWh for facade applications and lower values (around 40–50 g CO₂ eq/kWh) for optimally oriented roof integrations.[82][75] These figures account for upstream manufacturing (dominated by silicon purification and frame production), installation, operation, and end-of-life phases, but exclude building-specific adaptations unless specified; emissions are higher for vertical facades due to reduced annual yield from suboptimal irradiation.[83] Resource intensity in BIPV exceeds that of conventional building envelopes due to photovoltaic-specific materials, including silicon (core semiconductor), silver (conductors at ~15 mg/Wp), copper (wiring and busbars), and potentially indium or cadmium in thin-film variants, leading to 2–3 times greater metal depletion potential per square meter compared to standard glazing or cladding.[84][85] However, BIPV's multifunctionality—serving as both structural elements and power generators—offsets some incremental use by displacing separate PV mounting hardware and reducing overall material needs for energy-producing buildings; recycling recovers over 90% of metals like silver and copper in modern processes.[81] Net environmental effects favor BIPV over time, with energy payback times (EPBT) of 1.2–3.2 years for horizontal roof integrations and 2–7 years for facades in mid-latitude climates (e.g., 1.1–2.4 years optimal for monocrystalline silicon in sunny regions like Chile, extending to 7.1 years in low-irradiance northern Europe).[86] Carbon payback times (CPBT) follow similarly, often under 2 years in high-yield scenarios but up to 60+ years in poor orientations without grid decarbonization credits.[86] Over a 25–50 year lifespan, BIPV yields net GHG savings of millions of kg CO₂ eq per building (e.g., 14.8 million kg for apartment retrofits via displaced grid power), surpassing conventional envelopes plus add-on PV by minimizing transmission losses and land footprint, though upfront embodied impacts necessitate low-carbon manufacturing grids for full realization.[83][81]| BIPV Configuration | EPBT Range (Years, Monocrystalline Si) | Key Factors |
|---|---|---|
| Horizontal Roof | 1.2–3.2 | High irradiation; e.g., 1.2 years in sunny climates |
| South/West Facade | 1.8–4.0 | Orientation-dependent; shorter in equator-proximal sites |
| North Facade | 3.5–7.1 | Low yield; longest in high-latitude regions like Norway |