Q1： How to calculate the PV module quantity in series and parallel for DC input of String Inverter?
A PV module parameter, inverter parameter and temperature & conditions of installation area, these 3 aspects shall be considered together and conclude the result. About parallel quantity, avoiding useless wire, we shall put all input wires into the circuit to make sure maximum using of inverter. About series quantity, we shall make sure that the total voltage of all modules in the maximum series shall not be higher than the maximum DC input voltage which allowed by inverter. The total voltage of all modules in series will be great influenced by the module parameter and temperature & conditions of installation area. We shall deal with problems case by case. For example, the common 60-piece polysilicone component, the inverter using temperature is between -25 and +60℃, the parallel quantity of 600V DC input is between 9 and 13 pieces, of 1000V DC input is between 18 and 22 pieces.
Q2： How to estimate the capacity of PV power station according to the area of building roof deck?
A The estimation of PV power station capacity is a complicated system engineering. Besides the area of building roof deck, we shall also consider the structure of building roof, longitude and latitude, sheltered situation around the building and other aspects. All professional EPC company will adopt specilized software to assist calculation. For the convenience of all EPC company to estimate the capacity as soon as possible, we show some experice for reference. As for plain roof deck, we can do the perfect slanting installation. Different areas vary widely.The proposed estimate range is around 60～100W/㎡. As for colorful steel tile roof(slanting), photovoltaic module shall be installed according to the roof slope, less influenced by building roof structure.According to different spare area, we can estimate it between 100～120W/㎡.
Q3： How to estimate the power yield according to PV power station capacity?
A The computational formula of power yield of PV power station is L=W×H×η, where W refer to the capacity of PV power station, H refer to peak sunlight hour, η refer to total efficiency of PV power station. According to peak sunlight hour in days, monthes or years what H refer to, we can calculate separately the power yield in one day, one month or one year. According to practical experice, the total efficiency of large ground PV station can commonly arrive at 80%. According to different programs, there are big difference among distributed roof power stations, the total efficiency of that can commonly arrive at 75%. We take Shenzhen as an example, the average peak sunlight hour in July is 4.97h per day, the total peak sunlight hour in whole July is 154h, the total peak sunlight hour in whole year is 1427h, so that the daily power yield of 1MW station in July shall be 1000kW*4.97h*75%=3727kWh，monthly power yield shall be 1000kW*154h*75%=115,500kWh，yearly power yield shall be 1000kW*1427*75%=1,070,000kWh.
Q4： What will cause low efficiency of PV power station?
A “There are 9 aspects will influence the total efficiency of PV power station, list as below: 1. Yearly average loss due to temperature;
2. The loss due to miss matching of PV modules;
3. The loss due to dust, snow, shelter from objects and other objective aspects; 4. The loss due to some solar radiation are not available;
5. The loss due to DC circuit;
6. The loss due to the transfer efficiency of inverter;
7. The loss due to the efficiency of transformer;
8. The loss due to AC circuit;
9. The loss due to malfunction and maintenance of system.”
Q5： What are common communication methods of distributed PV program and how about the installation conditions?
A “For now, there are several kinds communication methods of distributed PV program adopted to the PV string inverter, list as follow:
1. RS485, apply to great program and inverters are installed together;
2. Ethernet，apply to scattered small program and there is network server around inverter; 3. WiFi, apply to personal or office building where are covered by wifi signal;
4. GPRS, apply to remote countryside, isolated island, wilderness and other places where are not covered by communication wires ( facilities) . ”
Q6： Can Senergy Inverter connect to thin-film module?
A “Generally,there are 2 kinds of thin-film module:Amorphous and CIGS. Their different structure leads to different solutions.
Amorphous: Since its structure is different from the crystal system (single crystal and polycrystalline) module’s,a low frequency transformer must be installed between inverter AC output terminal and electric supply and be grounded in PV + or PV – terminal.The isolation can prevent TCO from being corroded when amorphous is connected to transformerless inverter.At present, there are also amorphous module (such as FIRST SOLAR)on the market,which needs no low-frequency transformer.In this case,please contact the module suppliers.
CIGS: Since CIGS does not have (serious) TCO corrosion problems, most modules on the market are available to connect to our inverter. However, for your safety, please confirm again with the module supplier before you match it with transformerless inverter.
Q7： Are any restrictions on inverter installation environment? What are the dos and don’ts?
A “The Senergy inverter is made of an single-piece formed aluminum alloy,so it is robust and durable, which is advantageous especially in the harsh environment.And the surface enamel has a special coating with a higher weather resistance quality than average products. So there are almost no restrictions on the installation environment.It can fit high humidity environment, seaside, henhouse and pig house,farm, and even outdoor.
To get the best results, the following things should be paid attention to.
1) avoid direct sunlight: the direct sunlight will cause the inverter body temperature to rise. When the temperature is too high, the inverter will start self-protection mode-reducing output power, resulting in power generation loss;
2) ensure heat elimination and ventilation: some machine will be installed inside a box, leading to lack of cooling space. It will also cause the inverter body temperature to rise and reduction in power output.”
Q8： If lost the standard DC connector of PV inverter, can I use compatible type?
A “You’d better to use the standard DC connector provided by Senergy, since long-term effective connection of the metal terminals are not guaranteed by these claimed compatible connectors, that is why most of filed issue caused by using compatible connectors are usually happen after running a long time.
Meanwhile,if you match shell and seal from different manufacturers, their dimension difference even tolerance may cause ingress protection degraded from original IP grade, thus the internal condition inside the connector may be destroyed and the connector get failed.”
Q9： What kind of load can be connected to off-grid inverter?
A “Off-grid inverter with square wave or modified sine wave output (such as P serie) can only support resistive load, such as incandescent lamp, electric furnace (except induction cooker), etc. It is not suitable to connect capacitive load or inductive load, such as air conditioning, fan, refrigerator and so on.
Off-grid inverters with pure sine wave output (such as M serie) is able to connect either capacitive loads or inductive loads, provided that they are not overloaded. ”
Q10： Why PV inverter generate a low amount of power?
A “There are many factors can affecting the PV inverter power generation, while mainly originating from external factors, please check the follows at first:
1) whether the PV module is shaded
2) Is there any connection open or loosen among PV strings
3) whether the grid voltage is out of range, which will cause the PV inverter being off grid
If you have confirmed that external DC and AC connections are good, check the status of alarm indicator on inverter or check the content of status bar in mobile App, if there is an alarm, please call 400-930-3930 to contact customer service of Senergy.”