By Michael Gumm
Building Integrated Photovoltaics (BIPV)
The commonly-used term Building Integrated Photovoltaics (BIPV) has evolved into two distinct product groups. In the first group, people have traditional building products combined photovoltaics at the factory and the new solar building product has the same building envelope characteristics and functions of its non-solar counterpart with the benefit of generating solar power.
Suntech’s MSK design line See-Thru solar glazing is a good example of this type of product, combining window glass with solar to have a dual functional building product that replaces conventional glass curtain wall products, a product of form and function. This is a true building integrated photovoltaic product.
Building Applied Photovoltaics (BAPV)
The second type of building integrated system is starting to be called Building Applied Photovoltaics (BAPV). BAPV is a solar module that is applied directly onto the surface of a conventional building product material. BAPV products are commonly field applied with an adhesive or other form of surface method of attachment. The solar component is adhered to newly installed host building materials or retro attached onto existing building materials. A good example is the Uni-Solar flexible PV module applied to a new or existing metal roof panels or single-ply roof membrane in the field.
Thin-film BIPV and BAPV Market
While both conventional crystalline and thin-film photovoltaic materials can be used in both BIPV and BAPV systems, a few years ago, nearly everyone thought thin-film solar and building photovoltaics would grow to dominate the solar marketplace in both cost and installation, especially with roofing.
Fast forward to 2009 and the looking glass of 2006-2007 became upside down as crystalline not only continues to dominate the marketplace with conventional frame/rack mounted systems, but is priced lower than most thin-film PV systems.
The solar market is being driven by the lowest equalized cost of electricity and the price of crystalline PV modules is continuing to fall in price due to over capacity and the economic crisis of 2008-2009. So the question remains, what is it going to take to reopen and reinvorigate the thin-film BIPV and BAPV market. To answer this question, it is necessary to look at the BIPV and BAPV marketplace over the past few years.
Disconnection between Solar and Building Industry
Part of the problem goes back to the fragmented nature of the solar industry, whose business model focused on OEM sales and had limited experience with building materials. With shortages both on crystalline and thin film in past years coupled with high demand as a number of countries instituted aggressive renewable energy programs, there was little reason to be innovative as most solar manufacturers could sell as much as they produced.
When it came to combining solar with building materials, the process seems to say, let us wait for the building product manufacturers to approach us with a need or let us just stick it to a roof surface. The problem with this idea is simple, conventional building manufacturers are conservative by nature and take time to adapt to new technologies. For years, people had a general disconnect between both industries. The solar industries did not understand the needs of the building industry and the building industry not understanding the solar industry making product integration slow and at times difficult.
It is possible to combine both thin film and silicon crystalline with some conventional building products such as glass glazing or roof tiles. These types of solar-building products have never been cost effective from a product and application standpoint. Besides basic material cost, another high cost system component is the balance of systems with roof tile PV systems. Roof tile PV products are small by design and any solar tile roof system will require many electrical connections, all labor intense. Standard roof tile has always been a more expensive building material, add the cost of solar, plus the higher cost of installation and people have a solar component roof system that will not compete with conventional rack-mounted crystalline panels on cost. People have needed an end user who wants an architectural solution compared to standard rack mounted systems.
Asphalt shingles combined with thin-film solar have been a long sought to dream by many, yet combining thin film with the common low cost asphalt roof shingle provides the same challenges of the solar tile products with the added problem of not having the same longer service life of clay or concrete tile products. High cost of the solar component, coupled with balance of system cost, lower power density per square foot and higher life cycle cost, makes building a solar shingle very challenging.
A few years ago, the general belief was thin-film solar would cost much less than crystalline solar and the solar thin-film industry segment would churn out megawatts of low cost product. Thin-film manufacturers expected to 1-2 dollars a watt less expensive.
Flexible Solar
Thin-film technology has proven to be challenging, the simple fact is that many thin-film materials have been very difficult to move from the lab and pilot production to full commercial scale production with a levelized power output, higher power efficiency and lower cost to make these products competitive in the marketplace. People have seen some CdTe thin-film glass module products such as First Solar reach the marketplace and be competitive, but not BIPV. The one area that has proven to be the most difficult and challenging to be cost competitive in today’s market has been flexible thin-film technologies. Flexible solar represents the best type of solar material to combine with existing conventional building products.
a-Si and CIGS
Only very recently have people seen new types of flexible thin-film products get close to reach the marketplace and so far the most common solar products have been with amorphous silicon. CIGS manufacturers are just starting to overcome the problem finding a suitable low-cost flexible encapsulate with the added resistances to moisture needed by CIGS materials.
Neither amorphous silicon nor CIGS manufacturers are reaching the price points necessary to make BIPV or BAPV products competitive. Until unit watt cost is driven down farther, these products will remain highly specialized.
Product Service Life
Another area that needs attention is product service life. Coming from the roofing industry, I know the outside environment presents a formidable challenge for any product manufacturer to overcome. Long-term performance, with ultraviolet radiation from the sun, accelerated heating, aging, moisture, wind, ponding water, microbe attacks and owners’ neglect make it difficult to create building materials that will last with the 20-to-30-year service life claims of the solar industry, especially with polymer based solar products that are applied directly to these building material surfaces.
The average commercial low slope commercial roof service life is less than 20-years, reflecting the difficulty of creating low cost building products that perform in all climates. High slope roofing is no different, unless the roofing systems are metal and tile and even then, these types of roofs will require good design, proper long life underlayment components and careful attention to detail during the installation process.
Interest and Standards
Going forward the biggest driver to bring about change with BIPV and BAPV is the new interest of conventional building material manufacturers’ interest in solar. A little late maybe, people are seeing the roofing industry to move rapidly towards embracing solar and work with solar manufacturer to see how best to combine both systems together and transform more conventional roofing material into solar active products.
Matching the right solar materials and the right roofing materials is extremely important. Considering the high cost of a BIPV or BAPV product, real world testing, both in the labs and on the roof will need to be an ongoing process. New national standards for building codes, fire ratings and wind uplift need to be updated and reflect the new solar active building materials.
Bankability
For example, when flexible thin-film solar products are combined conventional roofing material, synconizing the service life of both products is the key to widespread market acceptance. One often forgotten component needed to sell any solar product is finance, with leasing and Power Purchase Agreements (PPA), the most common method of finance. Bankability is extremely important for any solar product and solar project. Any company financing solar is going to look at performance and service life of the solar-building material products and the balance sheets of the product providers.
Considerations for Manufacturers
The roofing manufacturer will have to be concerned with long-term adhesion between their roofing products and solar panels. Other important considerations include chemical compatibility of the roof membrane polymers and adhesives. Adhesives that will work with EPDM and TPO membrane can destroy PVC-based roofing materials. Interaction with adhesives and asphalt, and proper adhesion to granule surface materials is a concern.
The amount of heat transferred from the darker surfaced solar product to the roofing membrane, water flow for good drainage, ease of system application for the installer, inter-connectivity for balance of systems and of course reducing liability through a good warranty and maintenance program are included as well.
The roofing manufacturer may need to use thicker roof membranes to insure long-term performance and to reduce the effects of accelerated heat aging from the heat transfer from the solar modules to the roofing material. Other options may include thicker insulation and a additional layer of a harder surfaced overlayment board between the roof insulation and roofing membrane to provide a flatter and harder surface to reduce ponding water and degradation of the insulation due to increased foot traffic from other trades and the additional maintenance needed for the roof and solar installation.
Solar manufacturers need to look at adhesives to integrate their products with conventional building systems, new methods to combine and either integrate or adhered the solar materials to a roofing membrane at the factory or in the field. With the cost of both thin-film materials and crystalline coming down to historic levels, installation cost, both a system and balance of systems is the next area to be addressed.
Labor Cost for Installation
In the past, labor for installation represented a small percentage of the overall cost and that no longer holds true today. Labor cost to install the solar component system can equal or exceed the cost of the photovoltaics. In the case of roofing, bigger sheets of material are always better and the same holds true for BIPV and BAPV thin-film flexible modules. Wider and longer modules reduce labor cost and require less cabling to string together, bigger modules drive down labor cost and speed up installation time.
The same disconnect seen in the past between industries at the manufacturer levels which exist between the contractor trades involved in solar and roofing. The solar contractor market until recently was composed of many small regional contractors whose focus has been on steep roof solar installations, with limited experience with low slope roof systems other than rack-mount solar installations. Roofing contractors have not been actively involved in solar. The experience of both types of contractors needs to fully integrated, each learning from the other. Specific installation details need to be worked out so the installation process becomes more standardized.
Installation on Old Buildings
Another area of concern is what to do with existing roof or building envelope surfaces. For example, what do you do on a roof that is 5-to-7 years old or older? Do you really want to install a building applied photovoltaic module to an older building surface, knowing the service life of the roof will be for far shorter than the performance life of the solar modules? Imagine going back to an owner and asking him to replace a perfectly good roof, still under warranty. How do you convince a finance company to finance the installation?
Of course, one solution is to develop lower cost solar modules with a 15-year service life than the 25-30 year performance life available today. With the cost of solar coming down, perhaps PV modules made with a shorter performance life and even lower cost makes sense if you can balance the performance life with the length of financing.
Manufactures are going to have to strive to drive down cost, both in product cost and cost of installation. Electricity after all is a commodity and at the end of the day, the customer and the company providing the project financing are going to have to look at system cost. To make BIPV and BAPV more commonplace, both the solar and conventional building products manufacturers are going to have to work together closely from an installation point and solar manufactures are going to have to drive down cost even father to meet the promises made years ago.
Michael Gumm is Founder of SolarPower Restoration Systems, a company developing new BIPV systems and installation methods (http://www.solarpower-restoration.com/).
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