Design Of Off-Grid Photovoltaic Power Generation System

Off-grid photovoltaic power generation systems are widely used in remote mountainous areas, non-electric areas, islands, communication base stations, and streetlamps. Regardless of day or night, even if there is no grid access, it can still provide a reliable power supply at any time to meet the living and working power needs of residents, schools, or small factories in areas without power, lack of power, and unstable power.

Photovoltaic off-grid power generation systems are divided into small DC systems, medium-sized off-grid power generation systems, and large-scale off-grid power generation systems according to scale. The small DC system is mainly to solve the most basic lighting and DC power charging needs in areas without electricity. The medium-sized off-grid system is mainly to solve the electricity demand of families, schools, and small factories. The large-scale off-grid power generation system mainly solves the electricity demand of the whole village and the whole island.

The design principle of the off-grid photovoltaic power generation system: on the premise of meeting the power demand of the load, use the least photovoltaic modules and battery capacity to save the input cost.

1. Design of photovoltaic modules: peak power of solar cell modules = (load power (W) * load power hours per day * surplus coefficient during continuous rainy periods) / (system efficiency * local average daily peak sunshine hours)

2. Design of PV controller. The control current of the photovoltaic controller = the peak power of the solar cell module / the rated voltage of the battery pack. It should be noted that in high-altitude areas, the photovoltaic controller needs to enlarge a certain margin and use it with derating. Note: The margin refers to the difference between the design maximum limit and the normal operating limit of a certain index of the equipment.

3. Design of off-grid inverter. The capacity of the inverter = (the power of the load (W) * the margin factor required by the inverter) / the power factor of the inverter

4. Design of lead-acid battery. The capacity of the battery pack = (the power of the load (W) * the number of hours of electricity consumption per day * the number of consecutive rainy days) / (the rated voltage of the battery pack * the discharge coefficient of the battery * the efficiency of the inverter)

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