Due to the difference in economic development level, there are still a small number of remote areas that do not solve the basic electricity problem and cannot enjoy modern civilization. Photovoltaic off-grid power generation can solve the problem of basic electricity consumption for residents in areas without electricity or electricity.
The household photovoltaic off-grid power generation system is mainly composed of photovoltaic modules, brackets, controllers, inverters, batteries and power distribution systems. System electrical scheme design, mainly considering components, inverters (controllers), battery selection and Calculation. Before the design, the preliminary work should be done well, because the off-grid system is customized, there is no unified solution, you need to understand the user load type and power first, the power consumption during the day and night, the climatic conditions of the installation site. Off-grid systems, electricity depends on the weather, no 100% reliability.
Off-grid systems must be equipped with batteries and occupy 30-50% of the cost of the power generation system. The service life of lead-acid batteries is generally 3-5 years, and then replaced afterwards. From the economic point of view, it is difficult to get big The promotion of the scope is only suitable for use in places where there is no electricity.
Unlike off-grid systems and grid-connected systems, components and inverters are not configured in a certain proportion, but are designed according to the user's load, power usage and local weather conditions:
1. Confirm the power of the off-grid inverter according to the user's load type and power.
Household loads are generally divided into inductive and resistive loads, washing machines, air conditioners, refrigerators, pumps, range hoods, etc. Loads with motors are inductive loads, motor starting power is 3-5 times the rated power, in calculating the inverter For the power, the starting power of these loads should be taken into account. The output power of the inverter is greater than the power of the load. But for the average poor household, considering that all loads cannot be turned on at the same time, in order to save costs, The sum of the load power is multiplied by the coefficient of 0. 7- 0. 9. The following list is the power of common household appliances, for design reference.
2, confirm the component power according to the user's daily electricity consumption
The amount of electricity available in the off-grid system = total power of components * average hours of solar power generation * controller efficiency * battery efficiency. The design principle of the components is to meet the daily electricity demand of the load under average weather conditions, that is, the solar module The amount of electricity generated per day is slightly larger than the daily electricity consumption of the load. Because the weather conditions are lower than and above the average, the design of the solar cell module basically meets the needs of the worst season of illumination, that is, the battery can also be used in the worst season of illumination. Basically, it is fully charged every day. But in some areas, the illuminance of the worst season is much lower than the annual average. If the power of the solar modules is designed according to the worst case, then the power generation will be at other times of the year. It is far more than the actual needs, resulting in waste. At this time, we can only consider to increase the design capacity of the battery properly, increase the storage of electrical energy, and make the battery in a shallow discharge state, to compensate for the damage caused by the lack of power generation in the worst season. The power generation of the components cannot be completely converted into electricity, but also the efficiency of the controller and the loss of the machine and the battery. Loss.
The installation angle of the components should consider the geographical location of the users, and try to meet the requirements of summer and winter. In China, the azimuth of solar cells generally chooses the south direction, so that the solar cell unit capacity can generate the largest amount of power, the most ideal tilt angle. It is the tilt angle that makes the solar cell's annual power generation as large as possible, and the difference between winter and summer power generation is as small as possible.
Light bulb, electric fan, hair dryer, load, electricity equals power multiplied by time; air conditioner, refrigerator load, is intermittent work, air conditioning power consumption and indoor and outdoor temperature difference, room area, air conditioning energy efficiency Great relationship, 1 1P air conditioner, 8 hours in the evening, power consumption 1 - 5 degrees.
3, determine the battery capacity according to the user's night power consumption or expected standby time
The task of the battery is to ensure the normal use of the system load when the amount of solar radiation is insufficient. For important loads, to ensure the normal operation of the system within a few days, consider the number of consecutive rainy days. For general loads such as solar street lights, etc. Can be selected within 2~3 days according to experience or needs. For the general poor families, the main consideration is the price, then you don't have to think about the rainy days, when the sun is good, you can use it more. If the sun is not good, use less. If there is no sun, don't use it. Whenever possible, use energy-saving equipment, such as LED lights, inverter air conditioners. The design of the battery mainly includes the design calculation of battery capacity and the design of series and parallel combination of battery packs. In photovoltaic power generation systems, most of them use lead-acid batteries, consider To the battery life, generally take a discharge depth of 0. 5- 0. 7 between. Battery design capacity = (load daily average electricity consumption * continuous rainy days) / battery discharge depth.
4, 5kVA household system design
Customer's electricity demand: lighting 200 watts per day for 6 hours, refrigerator 50 watts for 24 hours a day, one inverter air conditioner for 12 hours, TV 50 watts for 10 hours a day. There are washing machines, desktop computers, rice cookers, Electric fans and other irregular home appliances, customer installation location in Diqing, Yunnan.
1, the total load power
200 watts of lighting, 50 watts of refrigerator, 750W of air conditioner, 50 watts of TV set, 300W of washing machine, 200W of desktop computer, 1200W of rice cooker, 100W electric fan, total 2850W, use Guruwatt SPF 5000 control inverter machine, output power 0. 0KW.
2, daily electricity statistics
Illumination 1. 2 kWh, refrigerator 1 degree, air conditioner 2 degrees, TV 0. 5 degrees, washing machine count 1 degree, desktop computer 0. 5 degrees, rice cooker 1 degree, electric fan 0. 5 degrees, average total 7 7 degrees, in fact, an average of about 6-10 degrees per day. Yunnan Diqing light conditions are good, an average of 4.5 hours per day, the design uses 9 280W components, a total of 2. 52kW, an average of 11. At 34 degrees, the off-grid system is less efficient, generally about 0.8, and the average available electricity is 9 degrees per day, so basically it can meet more than 99% of the electricity demand.
3, calculate the battery
Most of the household appliances are used at night. It may be only about 20% during the day. In order to increase the battery life, the battery capacity can be increased appropriately. The daily charge and discharge depth is low. This project uses 4 12V250AH colloidal lead-acid batteries. The total capacity is 12000VAH, and the available electricity is about 8.4 degrees. The average power is 6 kWh at night, and the depth of discharge is about 50%.
