Volume 45, Issue 4 - April 2010

SolarInsights



Form Over Function
A New Way to Look at the Function of BIPV

by Teodor Galitev


Building integrated photovoltaics (BIPV): the name itself may sound complicated and daunting, but this term for one of the most logical uses for solar electric systems, or photovoltaics (PV), is a term glass companies should get to know.

PV is a natural match with buildings. Energy-efficiency can go only so far and the rest (or most of it) of the energy can be supplied by a solar electric system. A PV system can bring the building down to net-zero electric energy consumption—the true and complete definition of energy independence.

One of the greatest disadvantages of the modular designs for solar electric systems is the aesthetics. This can be solved by hiding or masking the solar panels so they are not visible. This option is not always possible, however, and the solar modules may very well be seen as potentially obtrusive to the aesthetic design on your roof or facade.

 

Obtrusive Design
Solar module designers have made repeated efforts to change the appearance of the standard PV panel design, but without modifying the purpose of the product itself, it is impossible to create this desired BIPV product. BIPV in general needs to serve a double purpose: (1) to be an aesthetic feature of the building and (2) to generate power.

BIPV can be defined as a building material that generates electricity and has the same structural and physical characteristics as the material that is being offset. With this in mind, the most important function of the BIPV material is to serve as a building material.Generating power is a secondary function.

This single point of power generation as a secondary function is why BIPV is so fundamentally different from the PV solutions that have come before it.


"This single point of power generation as a secondary function is why BIPV is
so fundamentally different from the PV solutions that have come before it."



In general, any building material that can be replaced with a solar module with the same structural characteristics as the building material qualifies for use as BIPV. There already are a vast number of applications of this technology, and it’s my personal opinion that many more have not been discovered yet. Because this is a paradigm shift for PV design, there exists vast potential within the glazing world to come up with beautiful and innovative BIPV applications that fit seamlessly into architectural design criteria—while also moving us toward conditions where a structure is able to generate it’s own power.

Recognizing that power generation is the secondary function of BIPV we can qualify these building components as follows: roofing, facades, glazing, and art and architecture.

 

Types and Application
Roofing is one of the earliest and most common applications of BIPV. The goal is to match the roofing materials, including slates, shingles, tiles and other materials, to provide a seamless transition from one roof surface to the other. Any such transition has to be done in a way that does not compromise the integrity of the roof. The BIPV roofing material should provide adequate weather protection and a long-lasting roof. A BIPV warranty typically is the same as the regular solar panels warranty—generally 25 years at 20 percent less power. Since we can expect the solar portion of the BIPV roofing material to last 25 years or more, the roof integrity needs to be built to withstand at least 25 to 30 years. You do not want to replace the roof while under warranty.

In some cases, hot water collectors are mounted under the roofing material to add to the overall energy-efficiency of the building. Using PV with hot water collectors is not a new idea, however, hiding all of the ugly materials without compromising integrity and aesthetics is a revolutionary move. We will be seeing many more such applications as BIPV continues to grow in market share.

Facades are most commonly seen in commercial applications such as high-rises and other large buildings. Typically the façade material is replaced with a glass solar module that is mounted the same way as the offset material.

Glass has fantastic characteristics and is one of the most cost-effective building materials. Making the solar module does add cost, but compared to some of the materials that can be used—such as granite, sandstone and marble—a façade BIPV solar module is cheaper and has the double function of generating power. Facades will work everywhere, however they will see more sun and be more efficient in places such as the Northern U.S., Canada and Europe.

Glazing, or the use of glazing to mount the solar module, is a fast-growing application. We have seen glass companies, mullion extruders and fabricators promote and invest in such products. The glazing industry is well able to handle both small and large BIPV projects. Since glass is one of the most cost-effective building materials, the applications for this industry are vast. There is no denying that we are continuing to see more and more all-glass facades on buildings.

Any of the glass units can be replaced with a BIPV module that has the same structural and energy efficiency characteristics as the original glass. The BIPV glazing module is suitable for vertical, sloped and horizontal glazing applications. Insulating glass (IG) units can be used in locations that are adjacent to conditioned spaces.

The typical module is custom-designed with a specific size, strength and efficiency in mind. The designer has to make sure that the electrical connections are protected and to code. Typical electrical output boxes can be mounted on the back of the module, but with wider IG usage of BIPV we are seeing edge connections that are made while installing the BIPV module, and the installer hides the wires into the mullion. These kinds of systems are safer and, in my opinion, represent the direction that BIPV inevitably is going to take.

Art and architectural BIPV is a category that covers all of the other possible applications for BIPV. From artistic outdoor shower glass to shading and loggia type applications, it’s clear that where there is glass and glazing, there can be BIPV. To build such a project all of the above methods are utilized in an artistic and architectural manner.

 

Operation and Economics
The operation of these integrated systems generally is the same as a standard module system. A solar module array is configured in some manner and connected to an inverter that then converts the DC to AC and connects to the electrical circuits of the building. There is one major difference, however: here the solar module’s primary function is to perform as a structural and aesthetical building material.

Up until now, BIPV materials have been considered too inefficient to warrant the cost. Yet this way of thinking does not represent the reality of the value one sees in BIPV upon a closer look. Manufacturers often compare the BIPV materials to the their standard module, omitting the obvious “next level” of design, aesthetic and structural benefits and features that BIPV provides.

In my experience, BIPV materials are non-comparable to the standard module since you can never have a standard module that performs as a building material. The standard module is built only with power generation in mind and makes no provision for a structural contribution to the design.

The economics of this BIPV building material is relatively simple: it’s the cost of the offset building material plus the power generation.

Teodor Galitev is the vice president of design and engineering of NEOptions in Fountain Valley, Calif., and has been responsible for the design, development and installation of more than 250 BIPV systems. Mr. Galitev’s opinions are solely his own and not necessarily those of this magazine.


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