Mono Solar Panel

Typical design of Residential Off-Grid Solar System

2018-08-06 11:44:54
Due to the differences in economic development levels, 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 residential photovoltaic off-grid power generation system mainly consists of photovoltaic modules, brackets, controllers, inverters, storage batteries and power distribution systems. The system electrical scheme design mainly considers the selection and calculation of components, inverters (controllers) and batteries. Before the design, the preliminary work should be done well, because the off-grid system is customized. There is no unified solution. It is necessary to understand the user load type and power, the power consumption during the day and night, and the climatic conditions of the installation site. Photovoltaic off-grid systems rely on weather for electricity and have no 100% reliability.

The Residential Off-Grid Solar System must have a battery and occupy 30-50% of the cost of the power generation system. Moreover, the service life of lead-acid batteries is generally 3-5 years, and it has to be replaced afterwards. From the economic point of view, it is difficult to get a wide range of promotion and use, and it 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:

According to the user's load type
And power to confirm the power of the off-grid inverter
Residential load is generally divided into inductive load and resistive load . The load with motor such as washing machine, air conditioner, refrigerator, water pump, range hood is inductive load , motor starting power is 3-5 times of rated power, in calculating inverter In order to take into account the starting power of these loads. The output power of the inverter is greater than the power of the load. However, for the average poor family, considering that all loads cannot be turned on at the same time, in order to save costs, the sum of the load powers can be multiplied by a factor of 0.7-0.9. The list below is the power of common residential appliances for reference during design.

Confirm component power based on user's daily power consumption

Power available for off-grid systems = total component power * average solar power generation hours * controller efficiency * battery efficiency. The design principle of thecomponents is to meet the daily electricity consumption of the load under average weather conditions, that is , the daily power generation of the solar modules is slightly larger than the daily power 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 be fully charged every day in the worst season of illumination. However, 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 far exceed the actual demand at other times of the year. , causing 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, and make up for the damage caused by the lack of power generation in the worst season. The amount of power generated by the component cannot be fully converted into electricity, but 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 geographical location of the user, and try to meet the requirements of summer and winter. In China, the azimuth of the solar cell generally selects the south direction, so that the solar cell unit capacity has the largest power generation, and the most ideal tilt angle. It is the inclination angle that makes the solar cell's annual power generation as large as possible, and the difference between the winter and summer power generation is as small as possible. 

Loads such as light bulbs, electric fans, and hair dryers use electricity equal to power multiplied by time ; loads such as air conditioners and refrigerators work intermittently. The power consumption of air conditioners and the difference between indoor and outdoor temperature, room area, and air conditioner efficiency are Great relationship, 1 1P air conditioner, 8 hours at night, power consumption 1-5 degrees.

According to the user's electricity consumption at night
Or expect standby time to determine battery capacity
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, it is necessary to ensure the normal operation of the system within a few days, and the number of consecutive rainy days should be considered. For general loads such as solar street lights, etc., it can be selected within 2 to 3 days according to experience or needs. For the average poor family, the main consideration is the price, so don't worry about the rainy days, when the sun is good, use it more. Use less when the sun is not good, not when there is no sun. When selecting a load, try to use energy-saving equipment such as LED lights and inverter air conditioners. The design of the battery mainly includes the design calculation of the battery capacity and the design of the battery pack series-parallel combination. In photovoltaic power generation systems, most of them use lead-acid batteries. Considering the battery life, the discharge depth is generally between 0.5 and 0.7. Battery design capacity = (load daily average power consumption * continuous rainy days) / battery discharge depth.


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