Commercial 100kw 100kva 1MW Monocrystalline Mono Solar Power Kit For FARM

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Off-grid system types - AC or DC coupled

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 less than 6kW 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 multi-mode inverters can be both AC and DC coupled , which creates a very secure, flexible power system with multiple charging options and can enable black-start operation if the main inverter shuts down, the backup generator fails or the batteries are depleted.

Basic layout of a DC coupled off-grid system - The most versatile and modular off-grid configuration

Basic layout of a  AC coupled off-grid system - Well suited for modern off-grid homes and businesses

Off-Grid Battery Options

Lead-Acid

Until recently, traditional  lead-acid deep cycle  battery systems were the most common and reliable option for off-grid systems. Lead-acid batteries are a proven technology and can last up to 15 or more years if they are not held at elevated temperatures (above 40 degC), and are not regularly discharged too low. Lead-acid batteries require precise battery charging following a specific charge cycle plus temperature sensors to adjust voltage settings. Most well known off-grid inverter/chargers  offer programmable charge voltage settings along with sensors to precisely charge under all conditions. Lead-acid deep cycle batteries are still widely used and offer several advantages over lithium.

Lead-acid deep cycle battery options - 2V, 6V or 12V options and various types - Gel, AGM, Flooded
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.

Advantages

Compatibility with most inverters.
Proven and trusted technology.
Safe, very low risk (sealed Gel/AGM).
Battery will not cutout at low SOC or low voltage**
Long life (if not over discharged)
Easily recycled.

Disadvantages

Lower efficiency - around 80%
Low energy density - Very heavy
Usable capacity limited - Max 40% DoD on regular basis
Not modular - Fixed size once installed
Cannot sustain partial state of charge for long periods
High temperatures can drastically reduce battery life
** Cutout voltage & SOC based on inverter settings and rate of discharge.

Lithium-Ion

More recently lithium-ion battery systems have become extremely popular due to the high 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. This flexible sizing allows for additional capacity to be added at a later stage, which is a real bonus for both installers and customers alike.
Lithium batteries have a much higher energy density compared to lead-acid and are therefore lighter and more compact. A huge advantage of lithium is the ability to sustain a low state of charge (partial state of charge) for a prolonged amount of time without any negative effects such as sulfation which is a common problem with lead-acid batteries. Also, extremely high charge rates can be achieved using lithium with charging times up to 70% faster than lead-acid.

 

Advantages

Very high efficiency - Approx 97%
Very high energy density - Compact and Lightweight
High charge and discharge rates allowed
No degradation issues with partial state of charge
Modular and scalable systems (upgradable)
Safe and low risk (if charged correctly)
Most lithium batteries come with a 10 year warranty

Disadvantages

Can shutdown at high temperatures (45+ degC)
Can shutdown at low temperatures (below 5 degC)
Can 'trip off' under continuous high surge loads.
More difficult to recycle at end of life.
May not function without a compatible inverter.
 

 

Wide application flexibility - mounts for all roof types
Extensive pre-design for fast assembly and installation
Superior durability and longevity