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【Second】Comprehensive understanding of distributed photov

Ø  Design installer


38.Distributed photovoltaic power generation system is composed of several parts?

The distributed photovoltaic power generation system consists of photovoltaic modules, grid-connected photovoltaic inverters, bidirectional metering watt-hour meters and related parts.


39.How to obtain local solar energy resource data?

The first and crucial step in the design of photovoltaic systems is the analysis of solar energy resources and related meteorological data such as local solar radiation and precipitation where the project is installed and used. Weather data, such as wind speed, are key data for the design system. Currently, weather data from anywhere in the world can be accessed free of charge: the NASA Meteorological Database.


40.How to choose the grid-connected voltage of distributed photovoltaic grid-connected system? 

The grid-connected voltage of distributed photovoltaic system is mainly determined by the installed capacity of the system. The specific grid-connected voltage needs to be determined according to the power grid company's access system. The general household uses AC220V to access the power grid. Commercial AC380V or 10 kV can be selected to access the grid.


41.What determines the inclination of the photovoltaic array installation?

The installation inclination of photovoltaic array is generally determined by the latitude of the installation location, and there is a slight difference between different regions, generally, the angle of installation in our province is 26 degrees plus or minus two degrees.


42.How is the installation direction of the photovoltaic array determined? What is the impact on power generation?

Because the main reason of affecting photovoltaic power generation is the amount of sunshine, the module should be installed in the direction of the most abundant sunshine, and the different installation angles also have an effect on the generation of photovoltaic module.


43.How to choose photovoltaic module?

According to the specific situation of the installation site, different types of photovoltaic modules can be selected. The effective utilization area of the installation site determines the size of the assembly specifications. If the unit area wants to install a larger capacity, it can choose high-efficiency components. According to the appearance of the existing building can also choose different border components, according to the site of the series and parallel connection mode fixed component length, the selection of components need to consider the installation area, installed capacity. Cost and other factors, generally speaking, should choose good reputation, good quality, certification, quality assurance after-sale service, with fire-proof components.


44.How to choose the inverter? 

Generally according to the requirements of the system to configure the corresponding power segment of the inverter, the power of the selected inverter should be matched with the maximum power of the photovoltaic cell square array. Generally, the rated output power of PV inverter is close to the total input power, which can save cost.


45.How to consider the color, light transmission, size and shape of photovoltaic modules for distributed photovoltaic power generation projects combined with buildings?

Color can be chosen as close as possible with the building color, for light transmission should be considered to make full use of the building space and area, reasonable choice of size and shape, a good balance and optimization, as well as professional technical design.


46.Should wind speed be taken into account in the design and installation of photovoltaic arrays? How to consider the requirements of building load and wind resistance when installing distributed photovoltaic?

When installing photovoltaic arrays on the roof of buildings, the loads on the roofs of buildings must be taken into account, and the effects of turbulence and velocity changes on the security of photovoltaic arrays caused by the turbulence and velocity changes caused by the airflow in the buildings must be considered at the same time. The safety of photovoltaic arrays and surrounding life and property can only be ensured by taking full account of the local wind conditions, landforms, topography and the relative position of the buildings planned to install photovoltaic arrays in the surrounding environment.


47.How to determine the installed capacity of household photovoltaic power generation system? 

The installed capacity of the household photovoltaic system depends on the load of the equipment, the style of the roof and the area of the roof, and with the approval of the power grid company, the optimal installation capacity is determined. The average flat roof installation is about 70 watts\ per square meter.


48.How to estimate the power generation of distributed photovoltaic grid-connected system? 

To estimate the power generation of photovoltaic system, we need to know the local effective sunshine time, system efficiency, system installation capacity. We can also consult the photovoltaic system installer to get more accurate power generation.


49.After the distributed photovoltaic system is connected to the grid, how to distinguish between the current power consumption in the home from the power grid or the solar cell components in the home? 

After the installation of the distributed generation system, the grid company will carry out the inspection and acceptance of the grid connection, and after the acceptance, two (or two-way) meters will be installed in the owner's home. The two meters measure the electricity consumption of photovoltaic system separately. Since the subsidy standard of "all Internet access" mode is higher than that of "spontaneous use" mode, it is suggested that "all Internet access mode" be adopted.


50.Will PV systems work after installation if continuous rain or haze? Is there a lack of electricity or a power outage? 

Photovoltaic cell module can also generate electricity in a certain low light, but due to continuous rain or haze weather, the solar radiation illumination is low, if the operating voltage of photovoltaic system is not up to the start voltage of the inverter. Then the system will not work, grid-connected power generation system and distribution network is running in parallel, when the photovoltaic system can not meet the load requirements and do not work, the grid power will be automatically replenished. There is no problem of power shortage or power outage.


51.Will there be insufficient power when it is cold in winter? 

The power generation of photovoltaic system is really affected. The factors that directly affect the power generation are the radiation intensity and the duration of sunshine and the working temperature of the solar cell module. It is inevitable that the radiation intensity will be weak in winter and the duration of sunshine will be short. It is also normal that distributed photovoltaic generation is connected to the power grid, so long as the power grid has electricity, there will not be power shortage and power outage.


52.Will distributed PV access affect power quality? 

The power quality is the power quality in the power system. The main AC / DC converter of the system is the inverter. The inverter is put into operation only after passing the test of the power quality tester, so it will not affect the power quality.


53.Can you store the power generated by a distributed photovoltaic system during the day for night lighting? 

The power generated by distributed generation systems during the day can be stored for night lighting, which requires the addition of electrical elements such as controllers and batteries, which store the power generated by photovoltaics in batteries during the day. At night, the controller releases the stored power from the battery for lighting, and in the absence of energy storage equipment, the power system will stop working if the power grid is cut off. However, if the grid-connected inverter is replaced by an intelligent microgrid inverter (grid-connected and off-grid hybrid inverter), the system can still operate normally. 


54.Do you need additional wiring to install photovoltaic systems on existing buildings? How do I connect to an electrical system already in my home? 

The circuit of photovoltaic system is divided into DC part and AC part. These two parts need to be wired separately. The AC part is connected to the power grid and the node is located in the user side meter position. Finally, an electrical system is connected to the user's home. 


55.Where are the monitoring devices for distributed photovoltaic grid-connected systems, and will they occupy valuable indoor space? 

The monitoring device of distributed photovoltaic grid-connected system is divided into large photovoltaic power station monitoring, off-grid photovoltaic roof system monitoring and housetop photovoltaic system monitoring. Photovoltaic monitoring system can be installed outside without occupying indoor space. It can realize the data acquisition and data transmission to remote service platform for data storage and analysis with a variety of hardware products and supporting accessories. Finally, the system is feedback to the user in the form of report chart and other forms. 


56. What information does the design engineer require from the customer when designing the system according to the customer's requirements? 

The information required by the customer during the system design is divided into options and strong options, including the location of the project installation, the surrounding environment of the building, the year of construction, the type of roof, and the load on the roof. Access voltage levels and roof photos, optional sections include average monthly power consumption, roof panel structure CAD drawings, roof surface conditions, meter box photos, etc. Of course, the more detailed the optional part is, the more reasonable the optimal design is, and the better the power generation is. 


57.After the system is built, what units will be accepted? What should we pay attention to during the acceptance? 

The acceptance is mainly organized by the power grid enterprises, focusing on grid-connected electrical performance, construction quality of the project, component authentication, inverter authentication and technical parameters, lightning grounding, fire safety, component fire protection certification and so on.


58.How did the installation process proceed? 

The installation process of distributed photovoltaic grid-connected generation system is: basic construction, installation of support, installation of components, installation of converters, inverters, distribution cabinets and other electrical equipment, installation of connection lines. Installation of grid access systems and metering devices. 


59.What are the electrical safety requirements to be noted during the installation process? Can leakage of electricity produce dangerous eyelid to person? 

As long as there is sunlight, the photovoltaic module will have electricity, so when there is sunlight is unable to cut off the power supply, and because of the series voltage and accumulation, the corresponding voltage to the ground will be very high. Therefore, the installation process should strictly comply with the installation instructions provided by the system supplier, completed by the professional installation personnel, the wiring part of the equipment are installed using professional connectors, the protection level is set as IP65. Electrical equipment is also protected by air switches. 


60.How to meet the requirements of building insulation and sound insulation when distributed photovoltaic and building combine? Does it affect indoor lighting?

Different glass materials and structures are used to control the insulation and sound insulation. The indoor noise of distributed system equipment is determined by the agreement between the user and the manufacturer to meet the needs of the majority of users. Design insulation and insulation with architecture to meet the individual needs of different users. Using different battery chip and arrangement to adjust the transmittance, the lighting area will be set aside when the distributed and the building are combined, and the indoor lighting will not be affected.


61.How does photovoltaic power combined with buildings protect against lightning? Lightning is mainly divided into two kinds of hazards, direct lightning and indirect lightning strike. Direct lightning protection: the installation of metal lightning-arresting wires on tall buildings can release huge thunderstorm cloud charges. Lightning protection: add lightning protector in photovoltaic system, that is, install lightning protection module in confluence box, inverter and other electrical equipment to protect against indirect lightning strike. 


62. What is a bidirectional meter? Why do you need a bidirectional meter?

Two-way metering watt-hour meter is the watt-hour meter that can measure electricity and generate electricity, power and electricity are all oriented, from the perspective of electricity consumption, the calculation of electricity consumption is positive power or positive electric energy, and the generation of electricity is calculated as negative power or negative energy. The meter can read forward and reverse electricity through the display and store the data. The bidirectional meter is installed because of the presence of electricity generated by photovoltaics that cannot be consumed entirely by the user, while the remaining electricity needs to be transmitted to the power grid, which requires a number to be measured. When photovoltaic power generation can not meet the needs of users, this needs to measure another number, ordinary single block meter can not meet this requirement, so it is necessary to use intelligent meter with bidirectional meter metering function.


Ø  Running maintenance section


63.What are the common failures of distributed photovoltaic systems? What are the typical problems with each component of the system? 

Because the voltage does not reach the starting value, the inverter can not work, can not start, because of components or inverter caused by low power generation, system components may appear typical problems such as junction box burning. The component is partially burned. 


64.How to deal with common faults in distributed photovoltaic systems? 

The system can contact the installer or operator to explain the system problem when there is a problem during the warranty period, and the installer or operator maintenance chamber can answer the problem according to the user description. If it is not possible to troubleshoot the failure, special personnel will be sent to the site for maintenance. It is suggested that the operation and maintenance center be set up at the county level and the maintenance station be set up in villages and towns to facilitate timely maintenance and handling of abnormal faults.


65.How long is the life of a distributed photovoltaic system? 

The earliest photovoltaic power station in the United States was built in 1954, the earliest solar panel in China was used on the satellite in 1971, and the earliest photovoltaic power station was built in 1989. It is 26 years ago. The design life of photovoltaic system without battery is 20-25 years. 


66.How to reduce the maintenance cost of PV system? 

It is suggested that the products with good reputation and good after-sales service can reduce the incidence of malfunction and the users should strictly abide by the manual of the system products. Monitor and maintain the system regularly. 


67.How to deal with the late maintenance of the system, and how often? How to maintain? 

According to the instructions of the product supplier, the main maintenance work of the system is to wipe the components. In the larger area of Rain Water, there is generally no need for manual wiping. Non-rain season about once a month, dust fall large areas can increase the number of cleaning, heavy snow in large areas should be timely to remove heavy snow, to avoid the impact of electricity generation and snow after the uneven production. Clean up sheltered trees or debris in time.



68.Do you use clean water for cleaning photovoltaic modules and wipe them with clean water ? Do not have the risk of electric shock when wiping with water ? 

In order to avoid electric shock injury to the person and damage to the components under high temperature and intense illumination , it is recommended that the components should be cleaned at a later time in the morning or in the afternoon . It is recommended to clean the surface of the photovoltaic module with a soft brush , clean and gentle water , never use detergent , washing powder , etc . , so as to avoid damage to the photovoltaic assembly , and to avoid damaging the surface of the glass , and the components with coated glass should be careful not to damage the glass layer . 


69.How to use downtime properly ? 

The system shall be maintained in the early morning or in the evening when the light weak system is not running , and the insulation gloves shall be used for protective measures before maintenance . 


70.How to find out whether a photovoltaic module in a photovoltaic array is caused by reason ? 

When the user finds that the power generation amount of the same time system is reduced or compared with the power generation system which is adjacent to the same time system , the system may be abnormal , and the user can timely find out whether a certain component in the photovoltaic array has failed through the abnormal fluctuation of the monitoring data in the bus box , and then contact the professional personnel to diagnose the system by using the specialized equipment such as the clamp type table and the thermal imager , and finally determine the components of the problem in the system . 


71.Does the shading , leaves and even the shade of the bird ' s dung affect the power generation system ? 

In order to avoid the hot spot of the series branch , the solar module is damaged . In order to avoid the hot spot of the series branch , it is necessary to install the bypass diode on the photovoltaic assembly . In order to avoid the thermal spot of the series branch , it is necessary to install the DC insurance on each photovoltaic assembly string , and the shielding of the solar cell can also affect the power generation even without the thermal spot effect . 


72.In order to prevent the photovoltaic assembly from being impacted by heavy objects , the photovoltaic array can not be added with the iron wire protection net ?

It is not recommended to install the wire protection net because the wire protection network installed along the PV array may cause local shadows on the assembly , forming a hot spot effect , affecting the power generation efficiency of the entire PV plant . In addition , the impact on the general condition does not affect the performance of the assembly due to the passing of the qualified photovoltaic assembly through the ice ball impact experiment . 


73.Do you want to replace the damaged device immediately after the sun ?

If it is not possible to replace it immediately , if it is to be replaced , it shall be carried out in the morning or later than in the afternoon , and the maintenance personnel of the power station shall be contacted in a timely manner , and the professional personnel shall go to the replacement . 


74.Is it necessary to disconnect the photovoltaic power generation system due to thunderstorm and lightning protection ? 

The distributed photovoltaic power generation system is equipped with lightning protection device , so it is not necessary to disconnect . For safety insurance proposal , it is possible to choose to disconnect the circuit breaker switch of the bus box , cut off the circuit connection with the photovoltaic assembly , avoid the direct lightning generated by the lightning protection module from being removed , and the operation and maintenance personnel shall timely detect the performance of the lightning protection module to avoid the harm caused by the failure of the lightning protection module . 


75.Do you need to clean the PV power generation system after the snow ? How can the PV module handle the ice after the snow is frozen in winter ? Can you step on the assembly for cleaning ? 

If heavy snow is accumulated on the rear part of the snow , it is necessary to clean it , and the soft goods can be used to push down the snow . Be careful not to scratch the glass . However , it is necessary to clean the components without stepping on the components , so that the components can be hidden and damaged , and the life of the assembly is affected . Generally , it is recommended not to wait for the accumulated snow to be excessively thick and re - cleaned , so as to avoid excessive icing of the assembly .



76. Can distributed photovoltaic systems resist hail damage? 

Qualified components in photovoltaic grid-connected systems must pass through the frontal maximum static load (wind load, snow load, 5400PA). The maximum static load on the back of 2400PA and the hail with a diameter of 25mm are strictly tested at the speed of 23m / s, so the photovoltaic system will not be harmed. 


77. How to deal with the temperature rise and ventilation of solar cells?

The output power of photovoltaic cells will decrease with the increase of temperature. Ventilation and heat dissipation can improve the efficiency of power generation. The most commonly used method is natural wind ventilation. 


78. Is PV system harmful to users? 

Photovoltaic power generation system is based on the principle of photovoltaic effect to convert solar energy to electricity, no pollution, no radiation, inverters, distribution cabinets and other electronic devices are tested by EMC (electromagnetic compatibility). So there is no harm to the human body. 


79.Are there any noise hazards in photovoltaic systems? 

Photovoltaic power generation system converts solar energy into electric energy without noise impact. The noise index of inverter is no more than 65 decibels and there is no noise hazard. 


80. What should we pay attention to in the fire prevention and fire protection of the household distributed photovoltaic power generation system? 

It is forbidden to pile up inflammable and explosive items near the distributed power generation system. Once fire occurs, the loss of personnel and property is incalculable, except for basic fire safety measures. In particular, photovoltaic systems are reminded of their self-detection and anti-fire functions to reduce the possibility of fire, in addition to the need to reserve fire prevention and maintenance channels every up to 40 metres. And there must be an easy-to-operate emergency DC system break-off switch. 


81.After the breakdown of grid-connected photovoltaic power generation system, who should users report to for repair? is there a national unified service telephone?

Photovoltaic system failure should be the first time to feedback the problem to the installer, the installation chamber in the shortest time to make fault handling, suggest to choose a large brand, good reputation installers. At the same time, the operation and maintenance center can be set up. The trouble is overhauled by the operation and maintenance center.


Ø  Quality monitoring section


82.Why should we pay attention to the quality control of distributed photovoltaic system?

First of all, distributed photovoltaic power generation systems are mostly combined with buildings. If there are problems in the quality of the system, it may not only cause damage to the internal equipment of the power generation system, but also endanger the safety of the distribution station of buildings and the surrounding personnel. Secondly, distributed photovoltaic power generation systems are mostly for their own use, if the system quality problems may cause damage to the electrical equipment. The second distributed generation system is to generate electricity to obtain economic benefits. If there is a quality problem, the power generation and life of the whole system will be affected, and then the whole system will be affected.


83.Does passing each component mean that system integration does not need to be tested?

Although photovoltaic power generation system is composed of various components, the qualification of each component does not mean that the system integration is qualified. The overall design and configuration of the system, safety and operation performance need to be tested and verified.


84.How to select qualified system accessories products, how long does the warranty take?

It is suggested that the system accessories products approved by the state should be selected, the specifications, models and technical parameters of the system accessories products should be attached to the design requirements of the whole system, and generally speaking, the components should be guaranteed for five years. The inverter must be guaranteed for at least two years.


85. What kind of product certification is required to obtain state subsidies?

In the link of grid access acceptance, it is necessary to ensure that the completed photovoltaic power generation system meets the corresponding safety standards and quality requirements before passing the acceptance inspection. The main equipment in the photovoltaic power generation system includes components and confluence boxes. Inverters and so on are required to have the corresponding domestic certification.


86.Distributed photovoltaic grid-connected system quality problems, what supplier will follow the maintenance procedures, about how long will it take?

After the quality problem of distributed photovoltaic grid-connected system, the maintenance personnel need to judge the problem point and give feedback to the supplier. The supplier usually sends engineers to the site to confirm the quality problem and solve the problem. In case of quality problems caused by critical equipment, the supplier will contact the equipment manufacturer, and the equipment manufacturer engineer will generally come to the site for maintenance within a week.


87.How do owners roughly judge the merits and demerits of their photovoltaic systems? How to find solutions to suspected quality problems in the system?

The owner may make a preliminary judgment from the following aspects: first, check the appearance of the system, such as components, arrays, confluence boxes, etc. If the problems are found, appropriate measures can be taken to solve them in time. To check whether the system components used by the power station construction contractor have quality certification certificates, and to conduct on-site tests on the safety of the system, such as the continuity of the ground wiring, insulation, and whether there are lightning protection devices, etc. It is also necessary to test the electrical efficiency of the system. If problems are found, the power plant construction units should solve the problems in a timely manner.


88.How to judge whether the distributed photovoltaic grid-connected system is stable, whether the power quality meets the requirements, and whether it will damage the household appliances under the condition of the system fault?

The distributed photovoltaic grid-connected system generally has the function of data monitoring, it can be used to analyze the monitoring data to judge whether the system is running stably or not, if the power quality analysis can also be used to test the power quality in the power station and network. See if meets the national standard requirements, general photovoltaic system failure will have the protection device to cut off the power supply, therefore will not cause the damage to the household appliance.


89. Is the power generation monitoring data of the distributed photovoltaic grid-connected system the same as the metering data of the meter? How big is the error?

The power generation monitoring data of the distributed photovoltaic grid-connected system and the metering data of the meter are not necessarily the same. For example, if the same electricity metering equipment is used at the same node, and the accuracy is the same, then the data should be the same. But the monitoring equipment used in the PV grid-connected system is often the equipment used by the system construction units themselves, while the meter metering equipment is often the equipment in the power sector, so there may be some gaps in the data obtained by the different devices. The amount of error depends on the specific circumstances, and the settlement of electricity and subsidies is based on the installation of the power sector measuring equipment.


90. How to monitor the power of Internet when connected to the Internet?

 At present, grid-connected photovoltaic power generation systems are mainly monitored by installing electric energy meters approved by local power departments at parallel sites. In addition, the local power debugging center can monitor the power of each grid-connected photovoltaic system through remote communication, and the owner can also build a simplified information system to monitor and optimize the power of the Internet.


91. Can the power generation of the system be monitored online?

The power grid enterprises cooperate with the department in charge of energy and carry out the measurement, information monitoring and statistics of the distributed generation within the coverage of the instinctive power grid. If the corresponding monitoring system is installed in the photovoltaic system, the generation of electricity can be monitored online. In addition, the monitoring system can also realize on-line monitoring of key equipment parameters, power quality, environmental parameters and so on.


92. What are the current licensed photovoltaic systems and product testing and quality certification agencies in China?

Certification bodies are: Beijing Jianheng Certification Center and China quality Certification Center.

The main testing institutions are: the quality testing Center of Solar photovoltaic system and Wind Power system of the Chinese Academy of Sciences, the State Center for quality Supervision and Inspection of Solar Photovoltaic products, and the 18th Institute of China Electronic Science and Technology Corporation. China Aerospace Science and Technology Corporation 811 Research Institute, Shenzhen Electronics quality testing Center, Yangzhou Optoelectronic products testing Center, etc.


Ø  Cost-effectiveness and Business models


93.How do you estimate the investment in a household distributed photovoltaic system? How long does it take to recover costs?

Investment in the installation of household distributed photovoltaic system depends on the installation capacity and system investment. The hardware of photovoltaic system (including photovoltaic module, grid-connected inverter, wire, mountin