The biggest difference between an off-grid system and a grid-connected system is whether the PV system is connected to the grid or not. Grid-connected systems are calculated on the basis of return on investment, whereas off-grid systems are based on the basic need for immediate power supply, so they have a different focus when it comes to selecting components.

Photovoltaic modules

At the beginning, PV modules were only used in off-grid systems and small PV systems. Later, along with the large-scale development of grid-connected PV applications and the yearly updating of PV module technology, the conversion efficiency of modules has been greatly improved. Especially for some grid-connected power stations, more efficient modules are needed to improve the ROI ratio due to the full utilization of site resources. Of course, off-grid systems in general, due to the relatively large installation scenarios, do not have high requirements for component conversion efficiency, so conventional components are often the first consideration in selecting components for system design.

PV Off-grid Inverter

The AC load is the point of consideration. Generally, loads are divided into three categories: group loads (lights, heaters, etc.), inductive loads (air conditioners, motors, etc.), and capacitive loads (computer mainframe power supplies, etc.). Among them, due to the inductive load start-up current required for the rated time 3 ~ 5 times, and the general off-grid inverter 150% -200% of the short-term overload capacity can not meet the requirements, so the inductive loads need to be particularly considered inverter expansion design (off-grid inverter access to inductive loads, at least 2 times the inductive loads need to be more than the system design).

Photovoltaic storage battery

1. lead-acid/colloid batteries: energy storage systems generally choose maintenance-free sealed lead-acid batteries, with outstanding self-discharge performance, excellent anti-sulfuration performance, and strong overshoot resistance.

2. lead-carbon battery: a technology evolved from the traditional lead-acid batteries, which can significantly improve the life of lead-acid batteries by adding activated carbon to the negative electrode of lead-acid batteries, which can instantly charge at high capacity and can stop the negative electrode sulfation phenomenon. However, as a technological update of lead-acid batteries, its cost is slightly higher;

3. Lithium ternary / lithium iron phosphate batteries: compared with the above two types of energy storage batteries, lithium-ion batteries have a higher power density, more charge/discharge cycles, better depth of discharge and so on.

Above, a brief introduction to the photovoltaic energy storage system - photovoltaic off-grid system of some of the basic applications, and in the selection of the basic configuration of the equipment to give some suggestions for the photovoltaic industry personnel to understand and reference.