The following string design formula is proposed with reference to the "Design Specifications for Photovoltaic Power Stations (GB 50797-2012)", which meets two conditions at the same time: The maximum open-circuit voltage of the PV modules after series connection is lower than the maximum access voltage of the inverter; The MPPT voltage of the PV modules after series connection is within the MPPT voltage range of the inverter. Formula (1) Parameter meaning: Vdcmax: maximum input voltage of the inverter; the denominator parameter has been introduced above. Formula (2) Parameter meaning: Vmpptmin: minimum MPPT input voltage of the inverter; Vmpptmax: maximum MPPT input voltage of the inverter; t′: maximum high temperature at the installation location of the component; t: maximum low temperature at the installation location of the component; Vpm: peak power voltage of the component; Kv′: temperature coefficient of peak power voltage of the component (generally calculated using the open circuit voltage temperature coefficient Kv).  

Choosing the right solar photovoltaic system depends on your specific energy needs, budget, and available space. Residential and commercial systems serve different purposes and have distinct characteristics, making it essential to understand their key differences to make an informed decision.   Residential solar PV systems are designed for individual homes, catering to relatively stable electricity needs. They are typically installed on rooftops, with the roof size directly affecting the system’s capacity. Homeowners can select systems based on monthly electricity consumption, factoring in appliances like air conditioners and refrigerators. Most residential systems aim to achieve a  return on investment  ( ROI ) within a few years, thanks to government subsidies and tax incentives. While monocrystalline panels offer higher efficiency, they come at a higher cost than polycrystalline options. Additionally, smart monitoring systems enable users to track energy production and optimize usage.   On the other hand, commercial PV systems are ideal for factories, offices, and other large-scale facilities with higher and more variable energy demands. These systems often require extensive rooftop or ground-mounted space and involve more complex planning and installation. While the upfront investment for commercial systems is significantly higher, they provide substantial long-term benefits, including reduced energy costs and the ability to sell surplus power to the grid. Advanced technologies, such as high-capacity inverters and optimized configurations, help maximize efficiency and output.   The main differences between residential and commercial systems lie in scale, cost, and installation complexity. Residential systems are smaller, more affordable, and easier to install, while commercial systems are larger, more expensive, and involve detailed planning. Both benefit from incentives like subsidies and tax credits, though commercial projects may also leverage power purchase agreements (PPAs).   By evaluating your energy needs, budget, and space availability, you can select the right system to achieve both environmental and financial benefits. Solar power is a sustainable investment, whether for a home or a business.

Off-grid energy storage: 1. The main function is to convert the DC power generated by solar panels into AC power for load use. 2. Usually equipped with energy storage batteries to store excess power and release it when needed. 3. Independent operation, not dependent on the power grid, suitable for remote areas or areas without grid access. Application scenarios: 1. Mainly used in remote mountainous areas, deserts, islands and other areas without grid access or unstable grid. 2. Suitable for families, small commercial projects or occasions requiring independent power supply.   Hybrid energy storage: 1. It has both off-grid and grid-connected functions. It can convert the DC power generated by solar panels into AC power for load use, and can also be connected to the grid to achieve two-way flow of power. 2. When the power supply of the grid is normal, it can obtain power from the grid to supplement the shortage of solar power generation; when the power grid is out of power, it can switch to off-grid mode to provide power for the load. 3. It has efficient inverter capability and intelligent charging function, which can automatically adjust the charging parameters according to the battery status to extend the battery life. Application scenarios: 1. Applicable to places with grid access and where solar power generation is used to reduce electricity bills or achieve energy self-sufficiency. 2. Applicable to various occasions such as homes, enterprises, and public facilities, especially in areas where grid power supply is unstable or where energy efficiency is desired.

1. Check the DC cables and grounding of the components First, the reason for abnormal insulation impedance is that the DC cables are damaged, including cables between components, cables between components and inverters, especially cables in corners and cables laid outdoors without pipes. All cables need to be carefully checked for damage. Secondly, the photovoltaic system is not well grounded, including the grounding holes of the components are not connected, the component blocks and the brackets are not in good contact, and some branch cable sleeves are flooded, which will lead to low insulation impedance.   2. Rely on the inverter to check string by string If the DC side of the inverter is multi-channel access, the components can be checked one by one. Only one string of components is retained on the DC side of the inverter. After the inverter is turned on, check whether it continues to report errors. If it does not continue to report errors, it means that the insulation performance of the connected components is good. If it continues to report errors, it means that it is very likely that the insulation of the string of components does not meet the requirements. For example, if the Growatt MAC 60KTL3-X LV inverter is connected to an 8-way string and one of the strings is unplugged, if the fault alarm disappears, it means that the string is faulty.   3. When using a megohmmeter or other professional equipment to detect each string on site, use a megohmmeter to measure the insulation resistance of the PV+/PV- to the ground on the component side string by string. The impedance needs to be greater than the threshold requirement of the inverter insulation impedance. In some projects, dedicated insulation measurement equipment can also be used.

Solar inverters play a critical role in converting direct current generated by solar panels into alternating current suitable for household or industrial use. One of the key challenges in maintaining the efficiency and longevity of inverters is managing heat dissipation effectively.     During operation, inverters generate heat due to energy conversion losses and electronic component activity. If this heat is not dissipated efficiently, it can lead to overheating, which in turn reduces the system’s efficiency and shortens the lifespan of components. To address this, modern inverters employ various cooling strategies, including passive cooling, active cooling, and hybrid methods.   Passive cooling systems rely on natural convection and radiation, utilizing heat sinks and optimized airflow design. These systems are low-maintenance and energy-efficient but may struggle in high-temperature environments. Active cooling systems, on the other hand, use fans or liquid cooling mechanisms to enhance heat dissipation.     In conclusion, efficient heat dissipation in inverters is crucial for maintaining their performance and durability, especially as the demand for renewable energy systems continues to grow.

1. Analysis of lithium-ion battery capacity attenuation Positive and negative electrodes, electrolytes and diaphragms are important components of lithium-ion batteries. The positive and negative electrodes of lithium-ion batteries undergo lithium insertion and extraction reactions respectively, and the amount of lithium inserted in the positive and negative electrodes becomes the main factor affecting the capacity of lithium-ion batteries. Therefore, the balance of the positive and negative electrode capacities of lithium-ion batteries must be maintained to ensure that the battery has optimal performance.   2. Overcharge 2.1 Negative electrode overcharge reaction There are many types of active materials that can be used as negative electrodes of lithium-ion batteries, with carbon-based negative electrode materials, silicon-based, tin-based negative electrode materials, lithium titanate negative electrode materials, etc. as the main materials. Different types of carbon materials have different electrochemical properties. Among them, graphite has the advantages of high conductivity, excellent layered structure and high crystallinity, which is more suitable for lithium insertion and extraction. At the same time, graphite materials are affordable and have a large stock, so they are widely used.   When a lithium-ion battery is charged and discharged for the first time, solvent molecules will decompose on the graphite surface and form a passivation film called SEI. This reaction will cause battery capacity loss and is an irreversible process. During the overcharging process of a lithium-ion battery, metal lithium deposition will occur on the negative electrode surface. This situation is prone to occur when the positive electrode active material is excessive relative to the negative electrode active material. At the same time, metal lithium deposition may also occur under high rate conditions.   Generally speaking, the reasons for the formation of metal lithium leading to the change in lithium battery capacity decay mainly include the following aspects: first, it leads to a decrease in the amount of circulatory lithium in the battery; second, metal lithium reacts with electrolytes or solvents to form other by-products; third, metal lithium is mainly deposited between the negative electrode and the diaphragm, causing the pores of the diaphragm to be blocked, resulting in an increase in the internal resistance of the battery. The influencing mechanism of lithium-ion battery capacity decay varies depending on the graphite material. Natural graphite has a high specific surface area, so the self-discharge reaction will cause the lithium battery capacity loss, and the electrochemical reaction impedance of natural graphite as the negative electrode of the battery is also higher than that of artificial graphite. In addition, factors such as the dissociation of the negative electrode layered structure during the cycle, the dispersion of the conductive agent during the production of the pole piece, and the increase in the impedance of the electrochemical reaction during storage are all important factors that lead to the loss of lithium battery capacity.   2.2 Positive electrode overcharge reaction Positive electrode overcharge mainly occurs when the proportion of positive electrode material is too low, resulting in an imbalance in the capacity between the electrodes, causing irreversible loss of lithium battery capacity, and the coexistence and continuous accumulation of oxygen and combustible gases decomposed from the positive electrode material and the electrolyte may bring safety hazards to the use of lithium batteries.   2.3 Electrolyte reacts at high voltage If the charging voltage of the lithium battery is too high, the electrolyte will undergo an oxidation reaction and generate some by-products, which will block the electrode micropores and hinder the migration of lithium ions, thereby causing the cycle capacity to decay. The change trend of the electrolyte concentration and the stability of the electrolyte is inversely proportional. The higher the electrolyte concentration, the lower the electrolyte stability, which in turn affects the capacity of the lithium-ion battery. During the charging process, the electrolyte will be consumed to a certain extent. Therefore, it needs to be supplemented during assembly, resulting in a reduction in battery active materials and affecting the initial capacity of the battery.   3. Decomposition of electrolyte The electrolyte includes electrolytes, solvents and additives, and its properties will affect the service life, specific capacity, rate charge and discharge performance and safety performance of the battery. The decomposition of electrolytes and solvents in the electrolyte will cause the battery capacity to be lost. During the first charge and discharge, the formation of SEI film on the surface of the negative electrode by solvents and other substances will cause irreversible capacity loss, but this is inevitable. If there are impurities such as water or hydrogen fluoride in the electrolyte, the electrolyte LiPF6 may decompose at high temperatures, and the generated products will react with the positive electrode material, resulting in the battery capacity being affected. At the same time, some products will also react with the solvent and affect the stability of the SEI film on the surface of the negative electrode, causing the performance of the lithium-ion battery to decay. In addition, if the products of the electrolyte decomposition are not compatible with the electrolyte, they will block the positive electrode pores during the migration process, resulting in battery capacity decay. In general, the occurrence of side reactions between the electrolyte and the positive and negative electrodes of the battery, as well as the generated by-products, are the main factors causing battery capacity decay.   4. Self-discharge Lithium-ion batteries generally experience capacity loss, a process called self-discharge, which is divided into reversible capacity loss and irreversible capacity loss. The solvent oxidation rate has a direct impact on the self-discharge rate. The positive and negative active materials may react with the solute during the charging process, resulting in capacity imbalance and irreversible attenuation of lithium ion migration. Therefore, it can be seen that reducing the surface area of ​​the active material can reduce the capacity loss rate, and the decomposition of the solvent will affect the storage life of the battery. In addition, diaphragm leakage can also lead to capacity loss, but this possibility is low. If the self-discharge phenomenon exists for a long time, it will lead to the deposition of metallic lithium and further lead to the attenuation of the positive and negative electrode capacities.   5. Electrode instability During the charging process, the active material of the positive electrode of the battery is unstable, which will cause it to react with the electrolyte and affect the battery capacity. Among them, structural defects of the positive electrode material, excessive charging potential, and carbon black content are the main factors affecting battery capacity.

                                                                                                Preface As an important equipment in the field of modern energy conversion and transmission, the careful design and reasonable composition of the inverter-boost integrated silo are the key to achieving efficient and stable operation. The inverter-boost integrated cabin, as the name suggests, integrates the two key functions of PCS and boost into a compact and efficient cabin. This integrated design brings many significant advantages. The following takes a 2MW inverter-boost integrated silo as an example to analyze the internal composition and design. 1. Composition of the inverter-boost integrated warehouse The inverter-boost integrated warehouse adopts a standard container design, which is flexible in deployment and convenient for operation and maintenance. It can generally adapt to 500kW and 630kW energy storage converter PCS. The built-in transformer can adapt to voltage levels of 35kV and below, and supports local and remote monitoring. The inverter-boost integrated warehouse integrates energy storage converters, boost transformers, high-voltage ring network cabinets, low-voltage distribution boxes and other equipment in one container. It has a high degree of integration, reduces the difficulty of on-site construction, and is easy to transport, install, use and maintain. It has built-in emergency lighting system, fire protection system, access control system, and heat dissipation system. There are fireproof partitions inside the box, ventilation openings on both sides of the box, and heat dissipation ducts specially designed for PCS, which can effectively ensure the normal operation and safety of the equipment inside the boost integrated warehouse. 2. Design of the main circuit of the inverter-boost integrated warehouse From the perspective of space utilization, the integrated cabin greatly saves the floor space required for equipment installation. Compared with traditional distributed inverter and boost equipment, it integrates complex circuits and components into a cabin, which not only reduces the connection lines between equipment and reduces line losses, but also makes the entire system more concise and beautiful, and is easy to layout in a limited space. The 2 MW containerized energy storage boost transformer system mainly consists of a container body, four 500kW energy storage bidirectional converters, a 1250 kVA, 10 kV/0.38 kV transformer, a 1250 kVA, 10 kV/0.38 kV transformer, a 250 kVA, 10kV/0.38 kV isolation transformer, and supporting high-voltage switch cabinets, low-voltage distribution cabinets, and local monitoring system cabinets.   Two energy storage bidirectional converters are used as a group. The DC side of each group of energy storage bidirectional converters is connected to the energy storage system, and the AC side is connected to the secondary side of the 1250 kVA, 10 kV/0.38 kV transformer. The high voltage side of two 1250kVA transformers are connected in parallel to a 10kV high voltage switchgear. The total output of the system is 2MW, 10 kV three-phase AC, and energy can flow in both directions on the DC side and the AC side. 3. The high-voltage side of the high-voltage system uses a 10kV high-voltage switch cabinet to access the park's 10kV busbar, with one in and two out. One way is to supply power to two 1250 kVA transformers in parallel through a high-voltage circuit breaker, and the other way is to supply power to a 250kVA isolation transformer through a load isolation switch plus a fuse. The ring network cabinet is equipped with an isolation switch, a fuse, a circuit breaker, a lightning protection device, a live indication device, a fault indication device, a current transformer, and a comprehensive protection device. The comprehensive protection device controls the circuit breaker tripping by monitoring system parameters to achieve local and remote operation. 4. Local monitoring system The local monitoring system is installed in the local monitoring cabinet, with a programmable controller as the core, and is used to realize the status acquisition and system communication of transformers, high and low voltage switches, converters, fire equipment, air conditioners, lighting equipment, security equipment, etc. It has a human-computer interaction interface to display the status and parameters of the 2 MW container-type energy storage booster system. 5. Energy Storage Bidirectional Converter The energy storage bidirectional converter is the core component and is an important guarantee for achieving efficient, stable, safe and reliable operation of the 2 MW containerized energy storage boost converter system and maximizing the utilization of wind and solar energy. Combined with the on-site use environment and actual operation requirements, the energy storage bidirectional converter is designed to achieve grid-connected and off-grid operation functions.   The energy storage bidirectional converter is connected to the large power grid for a long time. The battery system is charged when the park load is small, and the battery is discharged when the park load is large. The energy storage bidirectional converter is required to have the function of grid-connected operation, realize independent decoupling control of active power and reactive power, and be able to coordinate with the superior monitoring system to realize various applications of the power grid system in the park.

The full name of the energy storage battery BMS management system is Battery Management System. The energy storage battery BMS management system is one of the core subsystems of the battery energy storage system, responsible for monitoring the operating status of each battery in the battery energy storage unit to ensure the safe and reliable operation of the energy storage unit. The BMS battery management system unit includes a BMS battery management system, a control module, a display module, a wireless communication module, electrical equipment, a battery pack for powering electrical equipment, and a collection module for collecting battery information of the battery pack. Generally, BMS is presented as a circuit board, that is, a BMS protection board, or a hardware box. The basic framework of the battery management system (BMS) includes a power battery pack housing and a sealed hardware module, a high-voltage analysis box (BDU) and a BMS controller. 1. BMU master controller Battery Management Unit (BMU for short) refers to a system for monitoring and managing battery packs. That is, the BMS motherboard that is often said, its function is to collect the adoption information from each slave board. BMU management units are usually used in electric vehicles, energy storage systems and other applications that require battery packs. BMU monitors the status of the battery pack by collecting data on the battery's voltage, current, temperature and other related parameters. BMU can monitor the battery's charging and discharging process, as well as control the rate and method of charging and discharging to ensure the safe operation of the battery pack. BMU can also diagnose and troubleshoot faults in the battery pack and provide various protection functions, such as overcharge protection, over-discharge protection and short-circuit protection. 2. CSC slave controller The CSC slave controller is used to monitor the module's single cell voltage and single cell temperature problems, transmit information to the main board, and has a battery balancing function. It includes voltage detection, temperature detection, balancing management and corresponding diagnosis. Each CSC module contains an analog front-end chip (Analog Front End, AFE) chip. 3. BDU battery energy distribution unit The battery energy distribution unit (BDU for short), also called the battery junction box, is connected to the vehicle's high-voltage load and fast-charging harness through a high-voltage electrical interface. It includes a pre-charging circuit, a total positive relay, a total negative relay, and a fast-charging relay, and is controlled by the main board. 4. High-voltage controller The high-voltage controller can be integrated into the mainboard or can be independent, real-time monitoring of batteries, current, voltage, and also includes pre-charge detection. The BMS management system can monitor and collect the state parameters of the energy storage battery in real time (including but not limited to single cell voltage, battery pole temperature, battery loop current, battery pack terminal voltage, battery system insulation resistance, etc.), and perform necessary analysis and calculation on the relevant state parameters to obtain more system state evaluation parameters, and realize effective control of the energy storage battery body according to specific protection and control strategies to ensure the safe and reliable operation of the entire battery energy storage unit. At the same time, BMS can exchange information with other external devices (PCS, EMS, fire protection system, etc.) through its own communication interface and analog/digital input and input interface to form linkage control of each subsystem in the entire energy storage power station, ensuring the safe, reliable and efficient grid-connected operation of the power station.

How do photovoltaic power stations deal with high temperature weather? On August 5, the Central Meteorological Observatory continued to issue an orange high temperature warning. According to data from China Weather Network, southern my country is experiencing a round of fierce high temperature and hot weather. Large-scale high temperature weather in the south will continue, with the core area remaining in the Jiangsu, Zhejiang and Shanghai areas. With strong sunlight and high temperatures, will the power generation efficiency of photovoltaic power stations that use solar energy to generate electricity also increase? The answer is no. Under normal circumstances, the ideal operating temperature of photovoltaic power generation components is about 25℃. For every 1℃ increase in temperature, the output power will decrease by about 0.35%, and the power generation of photovoltaic power stations will also decrease by about 0.35%. That is, after the temperature exceeds 25℃, the higher the temperature, the lower the output power, and the power generation will also decrease accordingly. In addition to photovoltaic components, the high temperature caused by the weather will also cause the efficiency of inverters and other electrical components to decrease. Generally, the operating temperature range of civilian-grade electronic components is -35℃～70℃, and the operating temperature of most photovoltaic inverters is -30～60℃. Improper installation or heat dissipation will force the inverter and electrical components to start  derating operation or even shut down for maintenance, resulting in power generation loss. Due to the influence of weathering and ultraviolet radiation, electrical components installed outdoors will also age quickly. To ensure that photovoltaic modules have good power generation in hot weather, the first thing is to maintain air circulation for modules, inverters, distribution boxes and other equipment. Avoid excessive number of modules blocking each other, which will affect the ventilation and heat dissipation of the photovoltaic array. At the same time, ensure that the area around photovoltaic modules, inverters, distribution boxes and other equipment is open and free of debris to avoid affecting the heat dissipation of the power station. If there are debris piled up next to the equipment that blocks or oppresses the power station, it must be removed in time. When installing a photovoltaic power station, the inverter and distribution box are installed in a shaded and rainproof place. If there is no shelter in the actual environment, they can be equipped with a canopy to avoid direct sunlight, which will cause the equipment temperature to be too high, affecting the power generation and equipment life. At the same time, a cooling fan can be installed on the equipment. In order to ensure the safety of photovoltaic power stations and avoid equipment failures and possible disasters caused by high temperatures, regular inspections of photovoltaic power stations are also essential. It is necessary to pay attention to the temperature difference problem that causes hidden cracks in components when cleaning components in high temperatures in summer. It is necessary to avoid high temperature periods and clean them in the early morning or evening when the temperature is lower.

Positive electrode materials The method of using materials with excellent conductivity to coat the surface of the active material body to improve the conductivity of the positive electrode material interface, reduce the interface impedance, and reduce the side reactions between the positive electrode material and the electrolyte to stabilize the material structure. The material body is bulk-doped with elements such as Mn, Al, Cr, Mg, and F to increase the interlayer spacing of the material to increase the diffusion rate of Li+ in the body, reduce the diffusion impedance of Li+, and thus improve the low-temperature performance of the battery. Reduce the particle size of the material and shorten the migration path of Li+. It should be pointed out that this method will increase the specific surface area of ​​the material and thus increase the side reactions with the electrolyte.   Electrolyte Improve the low-temperature conductivity of the electrolyte by optimizing the solvent composition and using new electrolyte salts. Use new additives to improve the properties of the SEI film to facilitate the conduction of Li+ at low temperatures.   Negative electrode materials Selecting appropriate negative electrode materials is a key factor in improving the low-temperature performance of batteries. Currently, the low-temperature performance is mainly optimized through negative electrode surface treatment, surface coating, doping to increase interlayer spacing, and controlling particle size.

The PCS (Power Conversion System) energy storage converter is a bidirectional current controllable conversion device that connects the energy storage battery system and the power grid/load. Its core function is to control the charging and discharging process of the energy storage battery, perform AC/DC conversion, and directly supply power to the AC load without a power grid. The working principle is a four-quadrant converter that can control the AC and DC sides to achieve bidirectional conversion of AC/DC power. The principle is to perform constant power or constant current control through microgrid monitoring instructions to charge or discharge the battery, while smoothing the output of fluctuating power sources such as wind power and solar energy. The PCS energy storage converter can convert the DC power output by the battery system into AC power that can be transmitted to the power grid and other loads to complete the discharge; at the same time, it can rectify the AC power of the power grid into DC power to charge the battery. It consists of power, control, protection, monitoring and other hardware and software appliances. Power electronic devices are the core component of the energy storage converter, which mainly realizes the conversion and control of electric energy. Common power electronic devices include thyristors (SCR), thyristors (BTR), relays, IGBTs, MOSFETs, etc. These devices realize the flow and conversion of electric energy by controlling the switching state of current and voltage. The control circuit is used to achieve precise control of power electronic devices. The control circuit generally includes modules such as signal acquisition, signal processing, and control algorithm. The signal acquisition module is used to collect input and output current, voltage, temperature and other signals. The signal processing module processes and filters the collected signals to obtain accurate parameters; the control algorithm module calculates the control signal based on the input signal and the set value, which is used to control the switching state of the power electronic device. Electrical connection components are used to connect energy elements and external systems. Common electrical connection components include cables, plugs and sockets, and wiring terminals. The electrical connection components must have good conductivity and reliable contact performance to ensure the effective transmission of electric energy and safe and reliable. The grid-connected mode of the energy storage converter PCS is to achieve bidirectional energy conversion between the battery pack and the grid. It has the characteristics of a grid-connected inverter, such as anti-islanding, automatic tracking of grid voltage phase and frequency, low voltage ride-through, etc. According to the requirements of grid dispatch or local control, PCS converts the AC power of the grid into DC power during the low load period of the grid to charge the battery pack, and has the function of battery charging and discharging management; during the peak load period of the grid, it inverts the DC power of the battery pack into AC power and feeds it back to the public grid; when the power quality is poor, it feeds or absorbs active power to the grid and provides reactive power compensation. Off-grid mode is also called isolated grid operation, that is, the energy conversion system (PCS) can be disconnected from the main grid according to actual needs and meet the set requirements, and provide AC power that meets the power quality requirements of the grid to some local loads.   Hybrid mode means that the energy storage system can switch between grid-connected mode and off-grid mode. The energy storage system is in the microgrid, which is connected to the public grid and operates as a grid-connected system under normal working conditions. If the microgrid is disconnected from the public grid, the energy storage system will work in off-grid mode to provide the main power supply for the microgrid. Common applications include filtering, stabilizing the grid, and adjusting power quality.

01What is a photovoltaic cable?   Photovoltaic cables are mainly used to connect solar panels and various solar system equipment, and are the basis of supporting electrical equipment in solar systems. The basic structure of photovoltaic cables consists of conductors, insulation layers, and sheaths.   Photovoltaic cables are divided into DC cables and AC cables: Photovoltaic DC cables are mainly used for connection between modules, parallel connection between strings and between strings and DC distribution boxes (combiner boxes), and between DC distribution boxes and inverters. Photovoltaic AC cables are mainly used for connection between inverters and low-voltage distribution systems, connection between low-voltage distribution systems and transformers, and connection between transformers and power grids or users.   Photovoltaic cables need to withstand long-term erosion from natural conditions such as wind and rain, day and night exposure, frost, snow, ice, and ultraviolet rays. Therefore, they need to have characteristics such as ozone resistance, UV resistance, acid and alkali resistance, high temperature resistance, severe cold resistance, dent resistance, halogen-free, flame retardant, and compatibility with standard connectors and connection systems. The service life can generally reach more than 25 years.   02What is a bidirectional meter?   A bidirectional meter refers to a bidirectional meter, which is a meter that can measure electricity consumption and power generation.   In a solar system, both power and electric energy have directions. From the perspective of electricity consumption, power consumption is counted as positive power or positive electric energy, and power generation is counted as negative power or negative electric energy. The meter can read the positive and reverse electric energy through the display screen and store the electric energy data. The reason for installing a bidirectional meter in a household solar system is that the electricity generated by photovoltaics cannot be consumed by all users, and the remaining electric energy needs to be transmitted to the power grid, and the meter needs to measure a number; When solar power generation cannot meet user needs, it is necessary to use the power of the power grid, which requires another number to be measured. Ordinary single meters cannot meet this requirement, so it is necessary to use smart meters with bidirectional metering functions.