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| Combination of green roofing and photovoltaic systems  It is now generally accepted that the combination of green roofing and photovoltaic systems provides numerous synergy effects: for example, the weight of the green roof serves as a structural weight for anchoring the solar module. The design allows for load distribution right across the roof, therefore avoiding point loads which would be created if concrete elements were used for anchorage. In addition, it is much more difficult to transport the concrete elements up to the roof area. The green roof substrate, on the other hand, can be easily piped up to the roof.Furthermore, there are still unanswered questions regarding a certain increase in earnings with photovoltaic systems as a result of the cooling effect of green roofs, something that was to date not measurable. ZinCo set about providing the proof and has measured this effect with its own testing equipment over a period of three years. ZinCo set up a measuring system on a test roof in Unterensingen/Germany and over the following three years continuously recorded test values. The test facility consists of three identical solar modules installed in the same location, faced in the same direction and at the same tilt. Modules 1 and 2 are installed on a bitumen waterproofing membrane (one on a low and the other on a high mounting frame). Module 3 was installed on an extensive green roof and on a high mounting frame. A total of 27 sensors measure continuously, among other things, the cell temperature at the underside of each module. In parallel, a weather station measures the current air temperature, wind speed and irradiance. It was generally established that the temperature of Module 3, installed on the green roof, remained closest to the air temperature, while the Modules on the bitumen membrane were considerably warmer. The measured values from the year 2010 were analysed and the result is a difference of, on average, 8 K between the temperature of Module 3 and that of Modules 1 and 2. That means: With a temperature coefficient of 0.5%/K, the solar module on the green roof generates a higher output of 0.5%/K x 8K = 4% compared with a solar module on a bitumen roof. Thanks to the ZinCo tests, it is now possible to quantify the extent of the cooling effect of a green roof on the above-mentioned approximate 8 K as an annual average and to put a figure of about 4% on the resulting increase in output of a solar facility. write your comments about the article :: © 2011 Construction News :: home page |