Small Distributed Solar Power Station Series: Key Points for On-site Survey

The roofs of residential buildings are mainly tile roofs and concrete roofs. For the preliminary on-site survey of buildings intended for the installation of distributed solar power stations on the roof, the following points should be noted.
For on-site survey, you need to prepare a tape measure over 20 meters long, a laser distance measurer (which can be purchased online at a reasonable price), a compass or a compass app on your mobile phone, and paper and pen, etc. If you need to go up to a sloping roof, it is recommended to wear anti-slip shoes and bring a safety rope.

I. Key Points for Building Survey

A. Tile Roof

Inquire about the year of building completion and the ownership.
The orientation and azimuth of the roof. Measure on site with a compass and also check with Google satellite maps.
The inclination angle of the roof. Measure the width of the roof and the width of the building to calculate the inclination angle of the roof. Generally, the inclination angle of roofs in the south is greater than that in the north, and in the Shanghai area, the inclination angle of roofs is around 30°.
The type and size of the tiles. Common tile types in residential buildings include Roman tiles, hollow tiles, double-groove tiles, asphalt tiles, flat tiles, fish-scale tiles, Spanish tiles, and slate tiles. If it is difficult to measure the size of the tiles on site, you can also look up the size online after determining the type of tiles. The size of the tiles, especially the thickness, determines the selection of parts such as hooks for the bracket system.
Consider the shading situation of the roof. Accurately measure the dimensions of the surrounding obstacles of the roof, and later use shadow analysis software to model and create a simple diagram of the usable area of the roof. Shadows on solar panels can greatly affect the power generation.
Lift some tiles to check the roof structure, and pay attention to record the size and spacing of the main beams and purlins. The hooks of the bracket system for tile roofs are installed and fixed on the purlins.

B. Concrete Roof

The year of building completion, ownership; the orientation and azimuth of the roof.
Measure the height of the parapet wall, and later conduct shadow analysis to determine the installable and usable area.
Check the waterproofing condition of the roof surface. On the principle of not damaging the roof waterproofing structure, consider whether the installation of the bracket is by self (negative) weight or expansion bolt fixing. The standard load-bearing capacity of a civil concrete roof should be greater than 3.6KN/m². Under the consideration of short-term wind load and snow load, the load of the bracket system is also less than the load-bearing capacity of the concrete roof. To avoid any damage to the waterproofing structure of the building after the installation of the photovoltaic system, the self (negative) weight bracket installation method is preferred.

II. Key Points for Electrical Survey

Check whether the incoming power supply is single-phase or three-phase. Civil villas generally have three-phase incoming power. Photovoltaic power generation systems with single-phase output are preferably connected to the phase with higher electricity consumption of the three-phase common incoming line switch. If conditions permit, it is best to use a three-phase inverter or three single-phase inverters.
Inquire about the average monthly electricity consumption or electricity cost and the main electricity consumption period. This serves as a reference for the installation capacity of the photovoltaic system.
Check the capacity of the owner’s incoming main switch. Considering the profit issue, the output current of the photovoltaic power generation system should not be greater than the capacity of the household switch. Under the current subsidy policy, the profit is maximized when all the generated electricity is used by itself.
With the principle of convenient wiring and saving, consider the installation position of the inverter and the grid-connected cabinet. The installation position of the inverter and the grid-connected cabinet should also take into account the issues of heat dissipation, ventilation, and protection from water and sun.