Photovoltaic modules, off grid inverters (including photovoltaic controllers/inverters), energy storage batteries (lead-acid/colloidal/lead carbon/ternary lithium/lithium iron phosphate, etc.), photovoltaic brackets, cables, and distribution boxes are all important components of photovoltaic off grid systems.

The biggest difference between off grid and grid connected systems is whether the photovoltaic system is connected to the grid. Grid connected systems are calculated based on investment returns, while off grid systems have a basic demand for essential power supply, so they have different focuses when selecting components.

pv module

Initially, photovoltaic modules were only used in some off grid systems and small photovoltaic systems. Later on, with the widespread application of photovoltaic grid connection and the annual updates of photovoltaic module technology, the conversion efficiency of modules was greatly improved. Especially for some grid connected power stations, due to the need to fully utilize site resources, more efficient components are particularly needed to improve the investment return ratio. Of course, in general, off grid systems do not have high requirements for component conversion efficiency due to the relatively large installation scenarios, so conventional components are often the first consideration when selecting components in system design.

Off grid photovoltaic inverter

Taking communication load as the consideration point. General loads are divided into three categories: group loads (lights, heaters, etc.), inductive loads (air conditioning, motors, etc.), and capacitive loads (computer power supply, etc.). Among them, due to the fact that the current required for the start-up of inductive loads is 3-5 times that of rated loads, and the short-term overload capacity of 150% -200% of off grid inverters cannot meet the requirements, the expansion design of inverters needs to be specially considered for inductive loads (when off grid inverters are connected to inductive loads, at least twice the system design of inductive loads is required).

Photovoltaic energy storage battery

1. Lead acid/colloidal batteries: Energy storage systems generally choose maintenance free sealed lead-acid batteries, which have outstanding self discharge performance, excellent sulfur resistance, and strong overcharge resistance.

2. Lead carbon battery: a technology evolved from traditional lead-acid batteries, which significantly improves the lifespan of lead-acid batteries by adding activated carbon to the negative electrode. It can be charged instantly with large capacity and prevent negative electrode sulfation. But as a technological update for lead-acid batteries, its cost is slightly higher;

3. Ternary lithium/lithium iron phosphate batteries: Compared to the two types of energy storage batteries mentioned above, lithium-ion batteries have higher power density, more charge and discharge cycles, and better discharge depth.

Above, a brief introduction has been given to some basic applications of photovoltaic energy storage systems - off grid photovoltaic systems, and some suggestions have been given on the selection of basic equipment configurations, which can be used as a reference and understanding for personnel in the photovoltaic industry.