Solar panels generate DC electricity which must be converted to alternating current (AC) electricity for use in our homes and businesses. This is the primary role of the solar inverter. In a common ‘string’ inverter system, the solar panels are linked together in series, and the DC electricity is brought to the solar inverter which converts the DC power to AC power which can then be used in the home or fed into the electricity grid.
Solar inverters are very sophisticated pieces of equipment that need to operate in extreme outdoor environments for up to 10 hours a day. In order to prolong the life of a solar inverter and improve its efficiency, it should be mounted in a sheltered location and out of direct sunlight. The ideal location is in a garage or undercover area that is close to the electrical switchboard.
String' solar inverters which are the most popular type of solar inverter. These inverters are connected to a string of solar panels linked together in series. String inverters are the most common type of inverter used in the UK, Europe, Australia, & Asia,
Hybrid inverters are used for both solar and battery storage. Most can also provide limited backup power in the event of a blackout. See the basic introduction and guide to the many different hybrid inverters and energy storage systems available including well known hybrid inverters from SolarEdge, Goodwe, Redback and SMA. Hybrid inverters work with lithium battery systems which can be of the same make, as shown in the image, or a third party battery manufacturer which is compatible with the inverter. OPEX/CAPEX.
Hybrid inverters generate power exactly the same way as common string solar inverters but have battery connections and other features built-in to enable energy storage for later use. This ability to store energy enables most hybrid systems to also operate as a backup power supply during a blackout, similar to a UPS system. During a blackout, some hybrid inverters can also operate in off-grid mode for a prolonged amount of time provided there is enough solar energy to recharge the energy during the day. However, dedicated off-grid solar systems should be designed and installed with specialised off-grid inverters which can handle larger surge loads.
: The 5 Main Parts Of An Off-Grid System
Off-grid systems are built using either AC or DC-coupled power sources. AC-coupled generation sources include common solar inverters, wind turbines or backup generators (gen-sets), while DC-coupled sources include MPPT solar charge controllers or micro-hydro systems. Whether a system is AC or DC-coupled is generally based on the size of the system. Most small-scale systems are DC-coupled and use efficient MPPT solar charge controllers. Larger off-grid systems can be either AC or DC-coupled depending on the type of off-grid inverter-charger used, and compatibility with different solar inverters (AC) or solar charge controllers (DC). Most modern inverter-chargers can be both AC and DC-coupled. .
Small-scale off-grid solar systems and DIY systems used on caravans, boats, small homes and cabins use MPPT solar charge controllers, also known as solar regulators, which are connected between the solar panel/s and battery. The job of the charge controller is to ensure the battery is charged correctly and more importantly, not overcharged. .
With the above considerations in mind, the key component of an off-grid power system is the main battery inverter-charger often referred to as a multi-mode inverter as they can usually operate in both off-grid or on-grid modes.
One of the most significant benefits of lead-acid batteries is unlike modern lithium batteries; the battery will not shut-down at a low voltage or low state of charge (SOC). This is important, especially in emergencies or when a backup generator fails. Lead-acid batteries can be discharged down to 0% state of charge if needed for backup, but it is not recommended as it can severely reduce the life of the battery..
Over the last few years lithium-ion battery systems have become extremely popular due to their high round trip efficiency (92% to 98%), compact size, lightweight and scalability. In contrast, lead-acid battery banks have a fixed size or capacity whereas lithium systems do not suffer this limitation
high-performance lead-acid batteries are still an excellent choice for off-grid systems. Lead-acid is a well-proven and reliable technology that is compatible with virtually all off-grid inverters and solar charge controllers. Lead-acid battery banks can also be more reliable in some situations as the battery will not automatically shut down in extreme temperatures or when a low state of charge is reached. In addition, they can be easily recycled using existing infrastructure.
Modern off-grid solar systems use battery inverters-chargers to manage batteries, solar, and backup power sources such as a generator. The inverter-charger is the heart and brain of an off-grid system. Its primary job is to supply pure sine wave AC power, and it must be able to meet the power requirements of the appliances under all conditions. Inverter-chargers sometimes referred to as multi-mode inverters, are the central energy management system and can be either AC-coupled with solar inverter/s or DC-coupled with solar charge controller/s..
an off-grid power system, the battery inverter-charger must be adequately sized and selected according to the appliances it will be running. Some equipment such as water pumps, fridge compressors and air-conditioning units require very high surge (peak) power during startup, and this is where many cheaper inverters can fail.