What is building-integrated photovoltaics (BIPV)?
Building-integrated photovoltaics (BIPV) is a specific type of solar shingles that provide solar energy solution. Solar shingles have another name, “photovoltaic shingles.” These are solar panels that are designed to appear like and work as traditional roofing materials, including asphalt shingle or slate, and generating electricity at the same time.
There are quite a few variances of solar shingles, such as shingle-sized solid panels that often replace conventional shingles in a strip, semi-rigid designs comprising silicon solar cells that have a similar size as traditional shingles.
Several companies produce solar shingles, though the three major manufacturers of solar roof shingles are SolarCity, RGS Energy, and CertainTeed. Other notable companies in the US are Atlantis Energy Systems (asphalt and slate systems) and SunTegra Solar Roof Systems.
What Exactly is Building-Integrated Photovoltaics (BIPV)?
A Building-Integrated Photovoltaics (BIPV) system is about integrating photovoltaics or PV modules into a building envelope, such as the facade or the roof. A BIPV system works as both as a building envelope material and power generator and can save materials and electricity costs, minimize or reduce the use of fossil fuels and emission of ozone-depleting gases, and add aesthetic value to the building.
When applying the BIPV, the PV elements become an integral part of the building, which often serves as the exterior weather layer. PV specialists and innovative designers in the US, Europe, and Japan are now exploring innovative ways of implementing solar electricity into their projects. As a result, a whole new dimension of Solar Electric Architecture has started to emerge.
A majority of BIPV systems are usually tied to a utility grid. However, BIPV may also be used in stand-alone, off-grid systems. An advantage of grid-tied BIPV systems is that, with a favorable utility policy, the storage system is actually free. The system is also 100% efficient and unlimited capacity. A grid-tied BIPV provides benefits to both the building owner and the utility. The on-site production of solar electricity is usually the highest at or near the peak load time of a building and the utility. The solar energy reduces energy costs for the building owner, while the exported solar electricity provides support to the utility grid during the period of the highest demand.
The term “building-applied photovoltaics (BAPV)” is often used to refer to retrofit photovoltaics, which is integrated into a building after completing the construction. Most building-integrated installations are actually BAPV. There are some manufacturers and builders that can differentiate a new construction of BIPV from BAPV.
History of building-integrated photovoltaics (BIPV)
Photovoltaic applications for buildings came into the market in the 1970s. Initially, aluminum-framed PV modules were connected to or mounted on, buildings that were located in remote areas and did not have access to an electric power grid. In the 1980s, application of PV module add-ons to roofs began. These PV systems were mainly installed on buildings that were connected to a utility grid in areas having centralized power stations.
In the 1990s, BIPV products were specifically designed for integrating into a building envelope became commercially available. In 2011, the US National Renewable Energy Laboratory, in its economic assessment and a brief overview of the history of BIPV, suggested that there could be significant technical challenges to overcome before the installed cost of BIPV becomes competitive with PV panels. However, there is a common perception that with growing commercialization, BIPV systems will become the support system of the zero energy building (ZEB) European target for 2020.
Despite the technical promise of BIPV, there are social obstacles that came in the way from becoming widespread, such as the conservative culture of the building industry and integration with high-density urban design. Experts suggest that enabling the long-term application of BIPV depends on rolling out an effective public policy as much as technological development.
In late 2016, Tesla (TSLA) initiated the acquisition of SolarCity, a solar panel manufacturer, and installer. Subsequently, the electric auto manufacturer revealed the reason for developing a new residential solar product, the solar roof. The tiles consisted of the roof had solar cells. A single roof tile will not produce much energy, but when they are installed in numbers, together they can potentially generate electricity equal to that of regular solar panels.
Even though Tesla’s solar roof stimulated the solar industry, it could hardly be called revolutionary. At the time of Tesla’s launch of solar tiles, solar shingles were already available commercially for more than a decade, and the technology was patented in the 1970s. Earlier, Dow was one of the biggest companies in the solar shingle business. In 2011, Dow started manufacturing its Powerhouse line of solar shingles. Similar to Tesla’s solar tiles, hopes for the Powerhouse were high. Even “Time” named the Powerhouse as one of the inventions of the year when it was launched as a prototype in 2009.
In 2016, however, just a few months before Tesla’s announcement that it was acquiring SolarCity, Dow stopped producing the Powerhouse. There were various speculations as to why the Powerhouse was discontinued. Analysts gave an opinion that solar shingles were not cost-effective; they generated less power and did cost more than regular panels of equal wattage. Also, corporate reshuffling was another reason for an abrupt end of the Powerhouse.
Compared to Dow, Tesla’s business model was no more efficient. Tesla took over SolarCity to have more control over the assembly and installation of its solar roofs. Dow had a similar strategy when it acquired NuvoSun in 2013 for a steady supply of the CIGS cells is used in the Powerhouse.
Even though Dow failed initially, the excitement around solar shingles remained as one of the emerging building-integrated photovoltaics (BIPV) technologies. Besides other BIPV products like transparent solar cells that can be mounted on building windows, solar shingles will potentially capture a greater portion of the solar market with the improvement in technology.
Similar to Dow, DuPont (DowDuPont, after a merger) has similar faith in solar shingles that it is willing to take a chance. The company announced that it intends to develop a new version of the Powerhouse. Instead of CIGS thin-film technology, the Powerhouse will now use crystalline silicon solar cells found in standard solar panels.
Other than the big players in the market, there are few competitors in the solar shingle market these days. However, according to California-based solar startup PowerScout, the rapid drop in the cost of solar means the industry as a whole is likely to grow substantially in the near future.
Types of building-integrated photovoltaics (BIPV)
There are four major types of BIPV products:
1) Crystalline silicon solar panels for ground-mount and rooftop power plants. Nearly 90% of photovoltaics in the world today are based on some variation of silicon. In 2011, around 95% of all shipments by US manufacturers to the residential sector were crystalline silicon solar panels.
The silicon used in PV has many forms. The major differentiating factor is the purity of the silicon. Though the question may arise, “what does silicon purity really mean?” It means the more perfectly aligned the silicon molecules are, the better the solar cell will be when it comes to converting sunlight into electricity
2) Amorphous crystalline silicon thin-film solar PV modules which could be hollow, light red, blue, yellow, as glass curtain wall and transparent skylight. Due to the low electrical output, solar cells based on amorphous silicon have usually been used only for small-scale applications such as pocket calculators. However, the latest innovations have brought in more attractive options for some large-scale applications as well.
Several layers of amorphous silicon solar cells can be combined with a manufacturing technique called “stacking.” It results in higher efficiency rates, which is around 6-8%. Only 1% of the silicon used in crystalline silicon solar cells is required in amorphous silicon solar cells. However, stacking is an expensive technique.
3) CIGS-based (Copper Indium Gallium Selenide) thin-film cells on flexible modules laminated to the building envelope or the CIGS cells are mounted directly to the building envelope substrate. Compared to the other thin-film technologies, CIGS solar cells have the maximum potential in terms of efficiency. These solar cells comprise a lesser amount of toxic material cadmium, which is found in CdTe solar cells. Commercial production of flexible CIGS solar panels began in Germany in 2011.
The efficiency rates for CIGS solar panels typically vary in the range between 10% and 12%. Many thin-film solar cell types are still in the research and development stages. Some of these cells have huge potential, and it is likely to be evident in the future.
4) Double glass solar panels with square cells inside. Double glass BIPV panels can be customized. In fact, there is a wide range of custom option available.
The size of the glass may vary as well. The largest size glass is limited by the old-fashioned lamination machine. Therefore most BIPV manufacturers offer panels of around 2 to 3×4 meters maximum.
BIPV Technology and how it works?
Building Integrated Photovoltaics (BIPV) technology integrates photovoltaics (PV) into a building envelope. The PV modules have the dual functions of building layer by replacing traditional building envelope material and power generator. By eliminating or avoiding the cost of conventional materials, the increasing cost of PV is reduced, and its life-cycle cost is improved. Sometimes, BIPV systems have lower total costs compared to PV systems that required separate, dedicated, mounting systems.
The complete BIPV system has the following elements:
1) PV modules, which could be thin-film or crystalline, transparent, semi-transparent, or opaque;
2) A charge controller to regulate the electricity in and out of the battery storage bank;
3) A storage system for storing electricity generally consists of the utility grid in utility-interactive systems or several batteries in stand-alone systems;
4) A piece of equipment for power conversion including an inverter to convert the DC output of PV modules to AC, compatible with the utility grid;
5) Backup power supplies, for example, diesel generators; and
6) Appropriate mounting hardware, cable, and safety disconnects.
How it Works?
The BIPV system is used to replace the conventional roof, shade, and façade material, and blends into the building, becoming unnoticeable. Implementation of the BIPV system brings in the potential to reduce installation costs, improve aesthetics, and address roofing-warranty issues.
The following four parts in the BIPV are crucial for its successful integration with a building:
1) The elements in a building such as a roof, skylight, glass, canopy, exterior wall finish, or sunshade.
2) The collector, which the part that reacts to sunlight and allows it to convert into electricity.
3) The conductor is the part that carries electricity generated by the collector surface through a conductive material.
4) The converter or combiner, which is the electricity that can be used directly to a usage point, like a solar power calculator. The power generated from many panels can be conducted to a combiner box and routed through cables to distribution (in case the equipment uses direct current), or passed through a converter system to convert from DC to AC.
The Solar Systems used in BIPV
The following solar systems are used in BIPV:
- Thin-film systems are used for flat and standing-seam metal roofs and spandrel glass that is used in skylights or as a canopy over a building entrance. These panels generate less electricity per square foot than conventional panels. They provide financial benefit in terms of reduced cost if they replace other building materials. Also, these panels have more aesthetic value.
- Conventional framed panels can be part of the building façade, providing shade for windows, or working as an architectural element. These panels may be thin and long, square, or rectangular. These solar systems usually produce more electricity per square foot than other systems.
- Transparent solar systems, which are a variance of thin films that work as organic dye and metals besides silicon. These solar panels can be transparent or translucent, and allow nearly 50% of visible light through.
- Ultraviolet systems, which are capable of converting ultraviolet light into electricity. These panels allow larger surfaces for glass and for combining electricity generation, lighting, and temperature control.
Even though BIPV works well on almost any building, there are few things to consider before using it. First, at the design level, it needs to be decided about fitting PV modules into the architecture aesthetically. Then comes the deployment of the PV for optimal performance at the site and location of the building. Finally, doing all of this in a cost-effective way.
Other elements to consider while integrating BIPV are:
- The total electricity load of a building.
- Available surface area for BIPV.
- The total potential of electricity that can be generated by BIPV.
- The efficiency of the solar panels.
- The solar orientation of the building, which is if the location has enough sunlight for investing in the system.
- Availability of incentives, credits, or financing options.
- If the electricity will be used directly to a DC compatible equipment or to be converted into AC.
Features of BIPV help integrate into various assemblies on a building envelope:
- Solar cells can be installed into the facade of a building, complementing or replacing conventional view or spandrel glass. Oftentimes, such installations are vertical, which reduces access to available solar resources. However, the large surface area of buildings can be useful to compensate for the reduced power.
- Photovoltaics may be installed into awnings and saw-tooth designs on a building facade. They provide more access to direct sunlight while providing additional architectural benefits such as passive shading.
- Using PV in roofing systems can directly replace batten and seam metal roofing and conventional 3-tab asphalt shingles.
- Using PV for skylight systems can be both economical and interesting in terms of the design feature.
Incorporating BIPV into a building changes the whole efficiency and cost equation. It is because the system and the overall building cost are also directly linked to the energy efficiency targets of the building. Achieving those targets can often be difficult, maintaining the balance between optimal efficiency and cost. This is why integrating solar energy in the building, along with several energy-saving measures with the help of BIPV, can help achieve the efficiency target.
In recent years, there has been a clear market trend to introduce more BIPV in the construction of new buildings. The first reason is due to new building regulations, and the second reason is improved efficiency and flexibility of solar cells. It has made integration of PV panels in the buildings, in roofing, and also in facades much easier.
Installing PV systems integrating with BIPV on roofs and façades can produce more than 50% of electricity to meet the present-day demand. To achieve this, however, the integration also needs to be made of existing buildings by changing the existing building material, particularly in residential dwellings in cities and towns. However, some property owners and architects may still have doubt whether the integration of the BIPV system into buildings will be economical and meet the aesthetic requirements of the buildings.
Due to new production processes, BIPV systems have evolved into an innovative and attractive building material in urban as well as rural areas. The variety of colors, textures, and formats that are currently available in PV modules are providing more flexibility for integrating the system into roofs and façades. This can be applied to all types of buildings as well as renovation projects, starting from farmhouses to high-rise buildings, and from minor maintenance measures through to end-to-end renovation.
Even though the amount of the initial investment in a renovation project with BIPV is higher than the cost of renovation without a PV system, this solution yields significant benefits both in terms of economic and energy efficiency. Building owners or investors can expect a satisfactory return in the long run, particularly if building-integrated PV is implemented early in the planning stage and is then optimized based on various factors. The amortization period for both primary non-renewable energy and greenhouse gas emissions is much shorter than the anticipated service life of a building-integrated photovoltaic system.
Depending on the types of buildings, the method of installation and the energy storage system, it is possible for a renovated building with BIPV integration to reach a self-sufficiency rate of up to 87%. However, at the same time, it depends on the factor; for example, if the fossil-fueled heating system is replaced by a heat pump.
Integration of PV modules into roofs and façades are more widely accepted these days than traditional roof-mounted systems. A survey carried out among house owners showed that there is a clear preference for modules that fit in with the architecture, availability of different color options (particularly red and black) in renovation projects in Switzerland or in Europe. It means the majority of the house owners are ready to pay more for BIPV systems than for non-integrated solutions.
Compared to the non-transparent BIPV modules, the semi-transparent modules with the improved performance of visible light transmission has generated more interest in recent years. When a semi-transparent PV module is integrated into building curtains, efficient visible light transmission can lower the energy consumption of indoor lighting. By using appropriate design, it is even possible to reflect the solar radiation in an indoor environment. It, in turn, will reduce the usage of the building’s cooling energy directly and can improve the thermal and visual comfort of the building. To get visible light transmission, this type of PV module mostly has the thin-film solar panel technology.
Customized BIPV solutions for high-end construction projects may remain expensive. However, by designing on a project-by-project basis, BIPV can help achieve cost-effectiveness and energy-efficiency through the usage of standard PV panels.
BIPV has its own advantages, which are:
- It is a green energy solution with no carbon emission. There is no negative impact on the ecosystem. Also, BIPV is recyclable energy, and we have plenty of it.
- BIPV can save space when integrating with a building during a renovation project. The system is often put on the roof or wall of a building. This is particularly important in cities where space is precious.
- BIPV helps in conserving the energy of a building. The smart junction box in the system absorbs the sunlight and converts it into electricity. The system also optimizes energy to a great extent due to which the temperature of the outer part of the building decrease and put less the pressure of the air conditioner inside.
- The cost of installing BIPV is still high, which often discourages building owners from using this technology and rather go for standard solar panels.
- The solar system is not quite stable as it largely depends on the weather as sunlight is not always available due to changing weather. To avoid this issue, it is important to have an efficient energy storage system to store solar energy as a backup.
The bottom line is BIPV systems can be designed to blend with and complement traditional building materials and can help create an aesthetically pleasing and hi-tech appearance. Beautiful and highly visible “green” building is both appealing and energy-efficient.
Related articles about building-integrated photovoltaics (BIPV)
Last month on April 20th, we hosted our first Clean Tech Kingpinsevents at the NEXUS Green Building Resource Center in downtown Boston.
It was a huge success! We had about 40 people, I met with someamazing people working on really innovative project. We saw 4presentations from true leaders in the industry and a great question and answer sessions after the presentation.
Two pieces of good news. First, we caught it all on tape and I’ll bereleasing each presentation with an overview of what was discussedstarting today. Second, we’re going to make Clean Tech Kingpins aregular bi-monthly event that will serve as a place for young clean tech pros to recharge, find inspiration, connect with and becomes friendswith their peers, and learn from current industry experts. So staytuned!
Here’s who we had speak, and the order I’ll be writing about eachdiscussion:
- Les Fritzemeir CEO and Founder Wakonda Technologies
- Paul Sellew CEO and Founder Harvest Power
- Chuck Lewin President New Generation Energy
- Jon Abe VP of Business Development Nexamp
Without further adieu, here is Les’s discussion on the current solarPV market, their opportunity, business model, and the future of building integrated solar PV. Enjoy!