The industrial and commercial roof area is large, the demand for electricity is large, and after the installation of photovoltaic power stations, it can not only meet the daily electricity consumption, but also integrate the excess electricity into the national grid in exchange for revenue.
So how to build small and medium-sized industrial and commercial photovoltaic power plants?
1 Determine the installation capacity
Determine the installation location of the photovoltaic power station, the power station can not exist in the building, trees to form a shadow; according to the available area to estimate the capacity of the power station, each square meter can be installed component capacity of about 100W.
Taking a roof with a usable area of more than 10,000 m² as an example, a small industrial and commercial photovoltaic power station of about 1 MW can be built. (Note: The roof area is for reference only, subject to the actual roof of the building)
"Cement flat roof installation photovoltaic"
"Factory building color steel tile roof"
◆ Cement flat roof
The cement flat roof is required to be designed as a roof, which can not only meet the load requirements generated by the photovoltaic system on the roof, but also facilitate the maintenance of the photovoltaic system in the later stage. Combining the latitude information of different regions and the optimal inclination angle of photovoltaic modules, the optimal power generation can be achieved.
◆ Factory building color steel tile roof
Since the factory house surface is mostly non-upper roof, if you want to consider increasing the photovoltaic system at the beginning of the project, it is recommended to increase the live load of the factory house surface, and the value is recommended to be greater than 0.7KN/m.
The color steel tile roof photovoltaic module adopts the tile method, and the angle adopts the natural inclination angle of the roof. There is a manned passage between the components, which is convenient for personnel to overhaul and maintain.
2 Select the grid connection method
◆ Spontaneous self-use, surplus electricity on the Internet
Income = kWh subsidy + electricity sales income + save electricity bill
The grid-connected mode of spontaneous self-use and surplus electricity is suitable for plants with large electricity consumption during the day, and the higher the proportion of self-consumption, the shorter the cost recovery cycle.
◆ Full internet access
Income = kWh subsidy + electricity sales proceeds
The grid-connected mode of full access to the Internet is suitable for factories with less electricity consumption during the day, and the grid connection is simple, and the full on-grid tariff is enjoyed.
3 Equipment selection
◆ Photovoltaic modules
Select volt components based on project requirements, cost, conversion efficiency, and available area.
The 500W component commonly used in the distributed market can be selected, the component conversion efficiency is 21.2%, and the electrical parameters are shown in the following figure.
◆ Photovoltaic inverter
Depending on the electrical parameters of the component, the operating current at the maximum power point is approximately 12A. You can choose the mainstream inverter on the market - Sunshine SG110CX-P2-CN inverter, this inverter has a maximum DC input of 15A, which can fully adapt to the current high-power components, and support 1.4 and above overmatch, saving initial investment.
Taking the grid connection of 1MW photovoltaic power station as an example, the inverter installation method: every 18 components is a string, and 14 strings are connected to the inverter, only 8 inverters are required.
The specific parameters are as follows:
◆ AC busting box
According to the number of inverters selected for the project, the AC bus box can select multiple sinks - the combiner box. According to the actual needs, you can choose two sinks one, four sinks one.
(1) Bus discharge; (2) Current transformer; (3) Lightning protectors; (4) Branch roads are open; (5) Current/voltmeter; (6) Bus current circuit breaker;
◆ Matching voltage requirements of inverter and component
1) The working voltage of the string is within the MPPT voltage range of the inverter and is greater than the starting voltage;
2) In the same MPPT, the number of components in parallel in different strings is the same, and the specifications of the panels connected in series are the same;
Current requirements: the current after the series parallel connection is not greater than the maximum input current of the inverter;
Cable requirements: The parallel connection of the components requires reasonable cable wiring, minimize the length of the DC cable, and avoid loss.
- Correct connection
Bad connection -
AC and DC cable DC cable requirements: DC cable generally choose photovoltaic certification special cable, photovoltaic array to inverter DC cable length should be as short as possible to reduce the power loss on the cable.
AC cable requirements: AC cable is mainly used for inverter AC side to AC cage or AC grid cabinet. Cable selection reference standard "Power Engineering Cable Design Code" GB 50217.
Copper cable design: SG110CX-P2-CN AC output cable is recommended to use YJV-0.6/1kV 4*70 mm2+1*35mm2;
Aluminum cable design: SG110CX-P2-CN AC output cable is recommended to use YJLHV-0.6/1kV 4*120mm2+1*70mm2
4 System installation requirements
Component arrangement Component orientation: the ideal installation orientation is due south;
Component inclination: the optimal inclination of the system is approximate to the local latitude angle, or according to the roof structure, the component is flat;
Laying on the slope of the roof, the inclination angle can be measured using an angle measuring instrument;
Module spacing between front and rear: The spacing should ensure that the solar cell array is not blocked from 9 a.m. to 3 p.m. on the winter solstice. By using the EXCEL table formula calculation, select the latitude, component width, length, and inclination angle to calculate the appropriate spacing. Take the Guangzhou area (23° north latitude) as an example:
◆ Component installation requirements
1) In addition to ensuring the best inclination and orientation of the components, the construction of the bracket should leave sufficient spacing on the roof as much as possible to achieve convection and reduce the temperature of the components;
2) The material of the bracket is made of stainless steel or hot-dip galvanized steel to play a role in anti-corrosion;
3) The bracket should ensure that the bottom of the component is not less than 15cm above the bottom surface to avoid the component from being immersed in water and splashing down the surface of the component by rain.
Cement flat roof fixed bracket; cement counterweight normal size 300 * 300 * 300mm; if the local monsoon is more, it is necessary to appropriately increase the counterweight.
◆ Inverter installation requirements
1. Try to avoid installing in direct sunlight areas.
2. Try to avoid installing in a position that is susceptible to rain.
3. The installation position needs to be ventilated and heat dissipated well.
Protecting the ground electrical ground prevents damage or even burndown of components or inverters caused by equipment short circuits, leakage of electricity, and protects the human body from electric shock damage when touching charged metal parts.
Electrical grounding systems include: component frame grounding, inverter grounding, distribution cabinet grounding.
Components: The aluminium alloy frame of the component is connected to the bracket and then reliably grounded by means of a lead wire.
Inverter: PE terminal of AC terminal block and PE ground of chassis housing.
Distribution cabinet: use a ground wire to connect to the grounding row or ground the nearest frame.
1
Component indirect grounding
2
Components and brackets are indirectly grounded
3
Bracket with lightning protection belt
Lightning protection grounding photovoltaic power station is installed at the top of the building, easy to be hit by lightning, lightning strike generated by the surge current will damage the inverter and other system equipment, so the power station needs lightning protection grounding, the surge current is directed to the ground to play a role in protecting the system.
Grounding body: The grounding body adopts round steel with a diameter of 10/12mm, the length is generally about 0.6m, and the grounding resistance should not be greater than 4Ω.
5 System configuration (1MW photovoltaic power plant grid connection as an example)
(1MW PV power plant system configuration reference)
◆ What materials need to be submitted for project review
After the construction of the photovoltaic system is completed, it is necessary to provide the power supply company with the materials required for the project review (which may vary in some regions), as shown in the figure below.
◆ Distributed photovoltaic project development process
Finally, the high-definition distributed photovoltaic project development process without watermark is attached for your reference.
Source: PV Box