The vast majority of residential and industrial and commercial photovoltaics install photovoltaic modules on the roof, which not only helps owners save electricity bills, but also optimizes the use of roof space and cools the roof.
01 Which installation method is used?
Different roofs have different methods of installing photovoltaic modules. Common installation methods include add-on, ballast and pile foundation.
If the roof is of the color steel tile type, the add-on type is generally considered, and the components are laid directly on the color steel tiles. Especially since the general color steel tile roofs do not have parapets, the tiled type has the best windproof effect and is the safest; In addition, the color steel tile roof also has a certain inclination angle. Although it may not be the optimal inclination angle for photovoltaic power generation, the modification cost caused by increasing the inclination angle also needs to be comprehensively considered. For cement roofs, which are usually flat, the common installation methods are ballast type and concrete foundation pile type, as shown in the picture above. Many times, building owners do not allow drilling into concrete flat roofs, either because they are concerned about the strength of the old building or because they do not want to change the waterproofing properties of the roof. This is why it is better to choose ballast or concrete foundation installation. Since the ballast type is not anchored to the roof, windproofing can be considered on the sides, especially for cement roofs without parapets. The main purpose of the concrete base is to ensure that the support system remains intact even during stormy seasons. It ensures a good installation without causing roof leaks, and also improves the efficiency of the solar modules and reduces the shading of the parapet from the sun.
02 Flat roof does not mean tile installation
Installing photovoltaic modules in a tiled manner on a flat roof seems to be the most natural way. Not only can the installation amount/area be maximized, but it is also possible to use photovoltaics as a roof ceiling to increase the space area. But in fact, installing photovoltaics on a flat roof does not mean that you should also set its inclination to 0 degrees. We need to consider many factors and should avoid flat installation, including: l Flat-panel modules are easy to accumulate dust, and dust accumulation may Causes 10% or even 30% loss of power generation; l It is more inconvenient to clean, and the accumulated water is difficult to flow out; l Compared with tilted installation, the power generation will be reduced; l The investment return period will be longer; l It may not be removed by natural rainfall Dust accumulation; There will be a significant difference in power generation between tilt-mounted and purely tiled photovoltaic arrays. If you are not willing to use the optimal inclination angle for installation, the installation inclination angle should be as high as possible.
03 Flat roof installation must consider wind speed
During the design phase of a solar system, the maximum wind speed that may occur locally must be considered, especially in areas with wind speeds exceeding 180 kilometers per hour. If there is no parapet to block the wind and no wind protection is considered between the arrays, the instantaneous wind speed caused by airflow in local areas will far exceed the actual wind speed. At this time, the selection of brackets, structural design, ballast or concrete foundation strength design must rely on the advice of professional organizations. Even the tiling of color steel tile roofs must be scientifically analyzed.
04 Risk of water leakage in flat roof installations
Standing water is common on flat roofs. Because the roof is flat, water has nowhere to go, or drains more slowly and stays on the roof longer, so any gaps or holes in the roof become places where water can accumulate. At this time, the flat roof with a photovoltaic system installed has become the biggest risk of water leakage for flat roof photovoltaics due to the damage to the waterproof layer that may be caused during the installation of brackets and concrete pile foundations. If it is a color steel tile roof, it is better to use clamps to install it than to drill holes in the color steel tiles; if the color steel tiles are not suitable for connecting with clamps, using structural adhesive is also an option. If holes must be drilled, you need to ensure that all holes All properly sealed against water.
05 Mechanical units on flat roofs need to be considered
One of the challenges in designing and installing PV on cement flat roofs is the various mechanical devices on the roof of the existing building, such as outdoor air conditioning units, drainage pipes, exhaust fans, ventilation facilities, water tanks, railings, roof structures, HVAC systems and water pipes, etc. These existing equipment not only affect the layout of rooftop photovoltaics, but also affect the spacing and arrangement of brackets. They may also cast shadows on the photovoltaic arrays or affect future operations and maintenance. Some designers will consider installing photovoltaics above these facilities to protect them from wind and rain. However, another problem brought by this is the height design requirements and wind protection requirements, as well as the difficulties in operation and maintenance.