Adaption of solar PV installations to Nordic conditions
Large low-angled roofs offer an attractive surface for solar PV installations even in northern conditions where snowy climate prevails. Therefore, guidelines regarding design of the solar PV installation to avoid production losses from snow shading and snow loads, increase energy received by the modules and sustain expected wind loads are needed.
The project goal was to create new knowledge about how large low-angled roofs in northern conditions efficiently can be used for solar PV installations. The knowledge contained by the project is expected to contribute to that solar PV installations mounted on large low-angled roofs in snow-rich regions should not have a snow-related energy production loss of more than 5% on an annual basis and that the majority of large industrial roofs should be used for solar energy production. The project is part of advancing the adaptation of solar PV installations to Nordic conditions.
By creating and verifying a CFD model for solar PV installations installed on large low-angled roofs, the expectation was that the model will be used to evaluate wind loads on designs of solar PV installations both within and outside the project and thereby contribute to increase the installation of solar PV installations on large low-angled roofs.
Large low-angled roofs are an attractive area for installation of relatively large solar PV installations and are found on, among other types of buildings, industrial buildings and sports halls. On roofs with a higher slope, the modules are often installed in the roofs plane, while on low-angled roofs they are tilted up from the roof. This tilt angle is often relatively small, 10–20 degrees, which means that in snow-rich regions snow accumulates on the array and a large part of its production is lost during the winter. A change in the design of the solar PV installation can causes changes in the way the wind load effect the array. The modules are also exposed to a heavy load from the accumulated snow cover.
The overall goal of the project was to create new knowledge for how large low-angled roofs in northern latitudes can be used efficiently for solar production. Through this knowledge, two long-term effect goals are expected to be achieved:
1) Solar PV installations on large low-angled roofs in snow-rich regions shall have a maximum snow-related production loss of 5% on an annual basis.
2) A majority of large industrial roofs are used for electricity production from solar PV.
Within the project, five alternative concepts have been evaluated and compared against a conventional low-slope array. CFD simulations on the developed concepts showed that the more the modules are angled up, the more dragforce they recive from the wind, which means that these must be anchored better. The production calculations showed that all the concepts are expected toprovide an equal or higher production than the conventional low-sloped array. Future climate changes are expected to bring less snow and warmer temperatures, which could lead to reduced snow problems, however, this is not expected in the near term, especially not in the northernmost parts of Sweden.