These three pictures are taken from the second chapter of the Guidance Atlas of Building Photovoltaic System Design. The pictures include Main electrical technical parameters of photovoltaic modules, Photovoltaic module installation point, Photovoltaic system installation site diagram.
Open Circuit Voltage(Voc)
Under certain temperature and irradiance conditions, the terminal voltage of the photovoltaic module in the no-load (open circuit) condition
Maximum Power(Pm)
Under standard test conditions, the maximum value of the product of current and voltage on the volt-ampere characteristic curve of the photovoltaic module
Maximum Power Point
The point corresponding to the maximum power on the volt-ampere characteristic curve of the photovoltaic module
Peak Power
Power generation of photovoltaic modules under peak sunshine conditions
Maximum Power Voltage
Under standard test conditions, the voltage corresponding to the maximum power point on the volt-ampere characteristic curve of the photovoltaic module
Maximum Power Current
The current corresponding to the maximum power point on the volt-ampere characteristic curve of the photovoltaic module under standard test conditions
Fill Factor
The ratio of the maximum power of the photovoltaic module to the product of the open circuit voltage and short circuit current.FF=Pm/(lsc* Voc)
Module Efficiency
The maximum power of the illuminated photovoltaic module is the percentage of the radiation power incident on the total area of the module, that is, η=Pm/(A*Pin), where A represents the total illuminated area of the photovoltaic module and Pin represents the incident light power per unit area.
Photovoltaic Module Installation Point
When installing building photovoltaics, the following factors usually need to be considered
Photovoltaic module angle:
The module angle (tilt angle) will affect the power generation efficiency and should be optimized according to the local latitude and light conditions. It is generally recommended to adjust within the latitude ±5°.If it is a fixed bracket, it is usually set at the optimal tilt angle.
Photovoltaic module bracket:
The bracket material (aluminum alloy, stainless steel, galvanized steel, etc.), corrosion resistance and wind load capacity need to be considered. Building power stations need to consider the building's load-bearing capacity.
Module spacing:
The spacing between modules should avoid mutual shading to ensure the best lighting conditions.The solar altitude angle on the winter solstice needs to be considered during calculations to avoid shadows.
Foundation and roof drainage organization:
Roof photovoltaic installations need to ensure smooth drainage to avoid water accumulation affecting the photovoltaic system and roof waterproofing layer.
Lightning protection and grounding facilities:
A lightning protection grounding system needs to be set up, including lightning strips, lightning rods and a good grounding grid.PV modules, brackets, and electrical equipment should all be connected to the grounding grid, and the grounding resistance is generally required to be less than 4Ω (refer to local standards for details).
Connection between foundation and structural layer:
When installing on the roof, chemical anchors, embedded parts or clamps should be used to fix to avoid damaging the roof waterproof layer.
Waterproof layer setting:
When installing photovoltaics on the roof, minimize the fixing method that penetrates the waterproof layer, or use waterproof sealant to seal the penetration point.Avoid direct contact between the bracket and the roof to reduce the risk of water corrosion.
Foundation stiffness:
It is necessary to ensure that the foundation is strong enough to resist the influence of external forces such as wind load and snow load to prevent the photovoltaic array from shaking or displacement.When calculating the foundation, factors such as local wind speed and earthquake intensity should be considered.
Position of protective layer:
In the roof photovoltaic system, the protective layer (such as waterproof coating, thermal insulation layer, etc.) should be set above the roof structural layer to avoid damage to the waterproof layer.
Photovoltaic system installation site diagram
The following figure shows different forms of building integrated photovoltaic (BIPV) applications, suitable for different building types and scenarios. The following is a brief introduction and characteristics of each application
1. Photovoltaic Skylight
Features: Combining lighting and power generation functions, usually using translucent photovoltaic glass or double-glass components.
Application: Suitable for large-span building roofs such as shopping malls, airports, stations, greenhouses, and stadiums.
2. Flat Roof PV System
Features: Install photovoltaic systems on horizontal roofs, and fixed brackets or adjustable brackets can be used.
Application: Suitable for flat roof structures such as industrial plants, commercial buildings, and residential buildings.
3. Metal Roof PV System
Features: Suitable for metal corrugated sheets or color steel tile roofs, generally using clamps to fix components to reduce perforation of the roof.
Application: Large-area metal roofs such as factories, warehouses, and logistics parks.
4. Sloped Roof PV System
Features: Install photovoltaic components directly along the roof slope, generally using tile hooks to fix, without damaging the roof structure.
Application: Villas, residential buildings, schools and other buildings.
5. Photovoltaic Canopy
Features: It can be used as a sunshade for building entrances, bus stops, parking lots, etc., and can provide power generation and rain protection.
Applications: Commercial building entrances, parking lots, stations, etc.
6. Photovoltaic Curtain
Features: Flexible photovoltaic film or translucent photovoltaic glass is used as curtain material, which can provide shade and generate electricity.
Applications: High-rise buildings, office buildings, residences, etc.
7. Photovoltaic Shading Wall
Features: Photovoltaic modules are used as sunshade components for building exterior walls, which can reduce indoor temperature and provide electricity.
Applications: Glass curtain wall buildings, commercial centers, office buildings, etc.
Photovoltaic system installation site diagram