Understanding Different Solar Solutions By Dustin Haddock and Rob Haddock
A standing seam metal roof (SSMR) is the most highly favored photovoltaic (PV) mounting platform for both prac- tical and economic reasons. The meth- ods of mounting the array and the longevity of the completed system are factors that enable metal to surpass any other roof type. When looking at a com- plete system of metal and PV there are a few things to consider to get the most bang for your buck. When planning a rooftop power generator,
choosing the most appropriate PV technology for your roof; maximizing roof space to get the most effi cient and affordable layout; and securing it to the roof in a manner that is consistent with the original design of the roof are the factors that will further ensure tremendous cost savings. The most common PV technologies can be broken into two groups: thin fi lm and crystalline.
12 METAL CONSTRUCTION NEWS June 2012
There are some very distinct advantages and disad- vantages each technology offers as they relate to the standing seam metal roof market. Thin fi lm is commonly perceived as the stuff
that sticks on, but this type of fl exible thin-fi lm “laminate” is only one category within the spec- trum of thin-fi lm alternatives. It is actually only about 2 to 3 percent of the total market. Amor- phous silicon (a-Si), cadmium telluride (CdTe) and copper indium gallium selenide (CIGS) all fall within the thin-fi lm category. All three are commonly sup- plied in a rigid glass module that is mechanically attached to the roof. One of the benefi ts within the thin-fi lm cat-
egory (as compared to crystalline) is that it is more productive in low light, such as early morning, late evening and overcast conditions. Typically the fl ex- ible amorphous silicon laminate modules are more
commonly used within the metal roofi ng industry. Due to weight considerations the glass substrate formats are seldom used on roofs. Although current- ly under bankruptcy protection, a company called UniSolar, Auburn Hills, Mich., dominates the fl exible thin-fi lm laminate market. Its product is offered in two sizes: 15 inches by 18 feet or 15 inches by 9 feet. One of the downsides of this technology is if the roof panel length does not coordinate in intervals of 9 feet there can be a tremendous amount of roof space loss, minimizing possible power output. For example, a 25-foot roof panel length would
result in the use of the 18-foot laminate. Since we are only able to use 18 feet of a 25-foot panel, 7 feet per panel is lost. In addition, because these laminates apply to the pan of the roof panel, there may also be space loss due to the roof panel’s width. The above example which further utilizes a 24-inch-wide roof