Solar Power Systems
Residential off-grid solar system design

Due to differences in the level of economic development, there are still a few remote areas that have not solved the basic power problems and cannot enjoy modern civilization. Photovoltaic off-grid power generation can solve the basic electricity problem of residents in areas without electricity.

The residential off-grid power system is mainly composed of photovoltaic components, brackets, controllers, inverters, batteries and power distribution systems. The electrical design of the system mainly considers the selection and calculation of components, inverters (controllers) and batteries. Before designing, do the preliminary work, because the off-grid system is customized. There is no unified solution. Need to understand the user load type and power, the power consumption during the day and night, and the climatic conditions of the installation site. The photovoltaic off-grid system relies on weather to supply power and is not 100% reliable.

Residential off-grid solar systems must have batteries, which account for 30-50% of the cost of power generation systems. Moreover, the service life of lead-acid batteries is generally 3-5 years and must be replaced afterwards. From an economic point of view, it is difficult to be widely promoted and used, and it is only suitable for use in places where there is no electricity.

Different from 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 consumption and local weather conditions:

According to user load type

Confirm the power of the off-grid inverter with power

Residential loads are generally divided into inductive loads and resistive loads. Loads with motors such as washing machines, air conditioners, refrigerators, water pumps, range hoods, etc. are inductive loads, and the starting power of the motor is 3-5 times the rated power. In order to consider the starting power of these loads when calculating the inverter. The output power is greater than the power of the load. But for ordinary poor families, considering that all loads cannot be turned on at the same time, in order to save costs, the sum of the load power can be multiplied by 0.7-0.9 times. The following table lists the power of common household appliances for reference during design.

Determine the power of the component according to the user's daily power consumption

Off-grid system available power = total component power * average solar power hours * controller efficiency * battery efficiency. The design principle of the module is to meet the daily power consumption of the load under average weather conditions, that is, the daily power generation of solar modules is slightly larger than the daily power consumption of the load. Because the weather conditions are lower and higher than average, the design of solar cell modules basically meets the needs of the worst season, that is, the battery can be fully charged every day in the worst season. But in some areas, the illuminance in the worst season is much lower than the annual average. If the power of solar modules is designed according to the worst-case scenario, the power generation at other times of the year will far exceed actual demand. , Resulting in waste. At this time, we can only consider appropriately increasing the design capacity of the battery, increasing the storage capacity of electric energy, and keeping the battery in a shallow discharge state to compensate for the damage caused by the insufficient power generation of the battery. The worst season. The electricity generated by the components cannot be completely converted into electricity, and there is also the efficiency of the controller and the loss of the machine and the loss of the battery.

The installation angle of the components should consider the user's geographic location, and try to meet the requirements of summer and winter. In China, the orientation of the solar cell is generally south, so that the solar cell has the largest power generation per unit capacity and the most ideal inclination angle. It is the inclination angle that makes the solar cell's annual power generation as large as possible, and the difference in power generation between winter and summer is as small as possible.

Light bulbs, electric fans, hair dryers and other loads use electricity equal to power multiplied by time; loads such as air conditioners and refrigerators work intermittently. The power consumption of the air conditioner has a lot to do with the temperature difference between indoor and outdoor, the area of the room, and the efficiency of the air conditioner. A 1P air conditioner consumes 1-5 degrees for 8 hours at night.

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