Choosing an off-grid solar system can be tricky as they are many times more complicated than the standard grid-connected solar system. The main components of off-grid power systems are solar inverter(ac) or solar charge controller(dc), battery inverter, battery bank, solar panels, and generator, an optional unit.
AC or DC coupled power system
Choosing an AC or DC power source is generally based on the size of the system. A small-scale system with less than 5kW is coupled with DC. In contrast, a more extensive off-grid system can be either AC or DC coupled depending on the type of inverter and compatibility with a different solar inverter or solar charge controllers. Modern multi-mode inverters are both AC and DC coupled, making them a flexible and secure charging option.
Battery chargers or inverters
Batteries are the main working component in an ac coupled off-grid system. The inverter's primary job is to provide pure sine wave ac power and must be able to meet the power requirements of all the appliances. For a machine that demands high peak power during start-off, such as fridge compressors, water pumps, and air-conditioning units, an appropriately sized and designed battery is required. Also, the inverter must be able to provide uninterrupted power under all conditions, including higher temperatures.
A traditional lead-acid battery is the most common and reliable choice for off-grid systems. Lead-acid batteries can last more than 15 years if they are not operated at temperatures higher than 40 degrees Celcius. Unlike modern lithium batteries, these batteries don't shut down at a low voltage or low state of charge. These are compatible with most inverters; however, they have low efficiency, around 80%, and low energy density. Lithium-ion battery, on the other hand, offers high efficiency, 92 to 98%. They have much higher energy density and are lighter and more compact.
Apart from power systems, inverters, and battery options, there are a few specifications to keep in mind while choosing an off-grid power system: Daily average power consumption (in Kwh) of the electric grid. Peak load(kW), maximum power demanded by appliances. The most crucial and obvious point to consider is solar exposure; it depends on locality, orientation, and climate.