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Topics Covered
Background
Photovoltaic (PV) Systems Mounted on Buildings
Rooftop Mounted Photovoltaic (PV) Systems
Architectural Concerns with Building-Mounted Photovoltaic (PV) Systems
Integrating Photovoltaic (PV) Systems into Building Architecture
Building-Integrated Photovoltaic (BIPV) Products
Materials for Building-Integrated Photovoltaic (BIPV) Devices
Methods for Integrating Photovoltaic Cells with Building Materials
Market Opportunities for Building-Integrated Photovoltaic (BIPV) Products
Summary
Background
NanoMarkets is a leading provider of market and technology research and industry analysis services for the thin film, organic and printable electronics businesses (which we refer to as TOP Electronics.) Since the firm’s founding, NanoMarkets has published over two dozen comprehensive research reports on emerging technology markets. Topics covered have included sensors, displays, OLEDs, HB-LEDs, e-paper, RFID, photovoltaics, smart packaging, novel battery technologies, printed electronics, organic electronics, emerging memory and storage technologies and other promising technologies. Our client roster is a who’s who of companies in specialty chemicals, materials, electronics applications and manufacturing. NanoMarkets also hosts a blog at www.nanotopblog.com where we discuss technology trends, company announcements and the industry’s on-going progress.c
Photovoltaic (PV) Systems Mounted on Buildings
When the first building-mounted photovoltaic (PV) systems were installed in reasonable volume sometime in the 1980s, they were generally secured onto a rooftop with little regard for appearance. It was the case in those early days that rooftop PV panels were more of a political and social statement than an economical source of power, and those installing them may have preferred the panels to be "out there" and blatantly obvious. But now that PV has become more mainstream--especially in markets such as California, Germany, and Japan--integration of the panels into the architecture of the building is more important. PV panels can still be a political or social statement, but even if they are obviously visible on a structure, they can still look good.
Rooftop Mounted Photovoltaic (PV) Systems
Rooftops worldwide lie over a tremendous amount of land surface, and billions of square meters of new roofs are erected annually. The majority of those rooftops receive daily sun exposure. Exterior walls, too, represent a similar amount of area and again much of that area receives daily sun exposure. When you consider the fact that almost all of those buildings consume electricity (and still more would if it was readily available), buildings are an obvious choice to locate solar panels. And not only for consumption at the host buildings--the vast majority of buildings are already grid connected and thus excess power generated by a building-mounted PV system can be fed into the grid to supply other users with greater electricity demand.
Architectural Concerns with Building-Mounted Photovoltaic (PV) Systems
In addition to these considerations, building rooftops and walls generally serve little other purpose than their structural and architectural ones. That is, there is little opportunity cost to using building roofs and walls with PV panels, aside from any architectural concerns. This is in contrast to open fields, which in the absence of PV power plants could often host farmland, vegetation, parkland, or other structures (some of which may also be suitable for outfitting with PV).
Buildings of all kinds--residential, commercial, even factories--have a long history of aesthetic architectural concerns, and those are important to the construction and upkeep of nearly any building. Construction is expensive and buildings are durable, and the builder, owner, and others want buildings to be attractive. In many (perhaps most) cases, the application of standard PV panels disrupts the lines, patterns, and other aesthetic architectural features of buildings. PV panels are also generally heavy, and there are structural considerations with mounting them on buildings.
Integrating Photovoltaic (PV) Systems into Building Architecture
Accommodations can be made, however. PV panels can be hidden, such as on a flat roof that is not visible from the ground. If sun-tracking systems are used or panels are otherwise mounted at an angle to the roof, panels can be shorter to minimize their obtrusiveness. Panels also can be mounted flush with, or at least parallel to, the roof surface so that unusual visual angles are avoided (though often at the expense of power output due to reduced direct illumination). Additional, non-PV structures can be added to the building to complement the PV panels. And panels can be made more aesthetic and suitable themselves--thinner, lighter, and in attractive colors and designs. For instance, a solar roof tile may have different construction as compared to a standard PV panels, and may be applied flush to a roof and appear similar to a skylight.
Building-Integrated Photovoltaic (BIPV) Products
Going beyond simply modifying the architecture of a building and/or the panels themselves to make PV panels appear like they belong, the next step is to use the building materials themselves as the PV panels, or conversely to use the PV panels themselves as the building materials. Building-integrated PV (BIPV) products of such an approach are in production, or at least in development, using all of the major PV technologies.
Materials for Building-Integrated Photovoltaic (BIPV) Devices
While such materials-level BIPV devices are naturally more costly than the PV panels that are not so intimately incorporated, they have the cost-related benefit that they substitute for traditional building materials, rather than being in addition to them. This raises the possibility that BIPV building materials may compete with the high end of traditional building materials. For instance, PV-incorporated shingles or roofing metal may be competitive with slate or other high-end roofing materials.
Methods for Integrating Photovoltaic Cells with Building Materials
There are different ways of merging PV cells with building materials. Most PV modules are encapsulated in glass and thus it is not too much of a stretch to design modules to substitute for other architectural glass. Semi-transparent modules may substitute in windows, skylights, atria, etc. and still allow some light through: while the PV cells necessarily absorb (and usually block) much of the light, spacing between the cells can transmit light in appealing patterns. Some PV cells--especially thin-film PV (TFPV) cells--can even transmit some of the incident light through. This light that is transmitted instead of absorbed will be colored depending on the wavelengths of light absorbed by the cell, generally appearing reddish in color.
Another approach is to use PV tiles that are designed to mount onto--or even to have a backing made of--construction materials. This can work for roofing, siding, and other cladding. In many cases these materials will not be subjected to bending, so rigid cells or even whole modules encapsulated in glass may be used. TFPV cells with flexible substrates and encapsulation materials potentially offer the ability to incorporate PV cells onto bendable building materials.
In some cases, this approach can be taken still further, so that the building materials themselves are actually used as substrates for TFPV cells. In this manner, some BIPV materials may not even appear to contain PV cells at all. This can provide much broader appeal to building owners who are especially particular about the look of their buildings. Furthermore, TFPV cells themselves have little weight beyond the substrate and encapsulation materials, and therefore have the potential to be the lightest-weight products in the BIPV class, as compared to traditional building materials plus the applied (or simply accompanying) PV modules.
Market Opportunities for Building-Integrated Photovoltaic (BIPV) Products
BIPV represents an opportunity for many businesses and homeowners to install PV electrical capacity without making the building look like a power plant. By offering this capability, BIPV gives PV in general a broader appeal. Of course, traditional PV modules will always dominate the PV market in dedicated solar farms and perhaps even on flat rooftops where appearance and incorporation into a building's architecture are not as important. But with the expected growing acceptance and incidence of mounting PV systems visibly on buildings will come an even stronger need to incorporate those systems architecturally into the buildings.
Naturally enough, the best markets for BIPV products are generally also the best markets for PV devices overall. In Europe, government incentives are a dominant factor in PV penetration, and Germany is the clear leader, followed by Spain. In Asia, Japan has the largest market for PV and BIPV, largely due to the high cost of grid electricity, and China's PV demand is growing rapidly. In the U.S., PV and BIPV are concentrated in California, where state policy has created significant incentives. New Jersey is the second-largest market because of a combination of policy and grid electricity prices.
Summary
There is an important distinction between the BIPV market and non-building-integrated PV installations. BIPV is inexorably linked to the construction market; BIPV products are most cost-effective with new construction. Even retrofits of existing structures with BIPV products are connected to the construction market, although those are not as big a growth opportunity. By contrast, utility customers are generally more interested in developing solar power plants, which can generally be mounted on the ground, or at most on top of a very large building. The BIPV and conventional PV markets could diverge in certain circumstances, such as large increases in PV demand by utilities in the midst of a deep slump in construction.
Source: " Building-Integrated Photovoltaics Markets 2009 and Beyond", Market Report by Nanomarkets
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