Nowadays, as a high yield and almost zero risk investment method, home photovoltaic is widely accepted by residents. Many people want to build it, but they feel confused about how to build it. Below, I will provide a detailed analysis of the design and construction process of home photovoltaic power stations.
Determine installation capacity
Determine the installation location of the photovoltaic power station, and ensure that there are no buildings or trees obstructing the power station to form shadows; Based on the available area, the capacity of the power station is estimated to be around 60-100W per square meter of installed components on the ground and flat roof.
Select grid connection method
With a usable area of 50m ² Taking the roof as an example, a 5kW power plant can be built.
Determine whether to use single-phase or three-phase grid connection based on the form of power grid connected to the household.
Select grid connection mode
Spontaneous self use of surplus electricity for grid connection: That is, the electricity generated by photovoltaic power is supplied for personal use, and the unused electricity is sold to the grid. This mode is suitable for households with high daytime electricity consumption, as the higher the proportion of self use, the shorter the cost recovery cycle.
Revenue=electricity subsidy+electricity sales revenue+electricity cost savings
Full grid connection: In this case, all the electricity generated by photovoltaic power is sold to the grid and not used at all. In this case, the local photovoltaic power generation benchmark grid connection price is used to purchase all the electricity generated by the power station.
Revenue=electricity subsidy+electricity sales revenue
The full grid connection mode is suitable for households with less electricity consumption during the day, and it is simple to connect to the grid, enjoying full grid electricity prices.
Select photovoltaic modules
Select single crystal or polycrystalline components based on project requirements, cost, conversion efficiency, and available area.
Select inverter
The household power station system has a grid connected voltage of 220V and a total component power of 6050Wp. Based on the maximum DC input power of the inverter, a suitable inverter is selected.
Select grid connected distribution box
Composition of internal components in the distribution box:
1. Inverter side switch
2. Self resetting overvoltage and undervoltage protector
3. Lightning arrester switch
4. Lightning arrester
5. Grid connected isolation switch
Choose an AC/DC cable
DC cable requirements: DC cables are generally selected for photovoltaic certification, and currently commonly used are PV1-F1 * 4mm. The length of the DC cable from the photovoltaic array to the inverter should be as short as possible to reduce power loss on the cable.
AC cable requirements: Generally, YJV type cables are selected for AC cables. Based on the maximum output current of the inverter, the cable current carrying capacity can be queried to determine the cable model.
5kW inverter configuration 3 * 4mm ² Copper core cables can meet the current carrying requirements.
Component layout
Component orientation: The ideal installation azimuth is due south
Component inclination angle: The optimal inclination angle of the system is approximately the local latitude angle, or according to the roof structure, the components are laid parallel to the roof slope, and the inclination angle can be measured using an angle measuring instrument.
The spacing between the front and rear rows of components should ensure that the solar cell array is not obstructed from 9am to 3pm on the winter solstice. By using the EXCEL table formula, selecting latitude, component width, length, and inclination angle can calculate the appropriate spacing. Taking the Guangzhou region (23 ° N) as an example:
Select bracket
Support requirements:
1. In addition to ensuring the optimal inclination and orientation of the components, the construction of the bracket should leave sufficient spacing on the roof as much as possible.
2. The bracket material is made of stainless steel or hot-dip galvanized steel for anti-corrosion purposes.
3. The bracket should ensure that the bottom of the component is no less than 15cm above the bottom surface to avoid component immersion and rainwater splashing onto the surface.
Inverter installation environment
Inverter installation requirements:
1. Try to avoid installation in direct sunlight areas
2. Try to avoid installing in a location that is prone to rain
3. The installation position needs to be well ventilated and heat dissipation
ground protection
The importance of grounding: Electrical grounding can prevent damage or even burning of components or inverters caused by equipment short circuits and leakage, and protect the human body from electric shock when touching live metal parts.
The electrical grounding system includes: component frame grounding, inverter grounding, and distribution cabinet grounding.
Component grounding: The aluminum alloy frame of the component is connected to the bracket, and then reliably grounded through the down lead.
Inverter grounding: The PE end of the AC wiring terminal and the PE grounding of the chassis casing.
Grounding of distribution cabinet: Use a grounding wire to connect to the grounding bar or ground the nearby frame.
Lightning protection grounding: Photovoltaic power stations are installed on the top of buildings and are prone to lightning strikes. The surge current generated by lightning strikes can damage system equipment such as inverters. Therefore, the power station needs to be grounded for lightning protection, guiding the surge current underground to protect the system.