1 | h1

10KW Off-Grid Solar System

Off-Grid Solar Power System

Can you go off-grid with a 10kW solar system in Australia?

Are you interested in going off-grid with solar power? Choosing a suitable off-grid solar energy system is more challenging than installing a regular on-grid solar system.

Let’s take a look at some things you need to consider when considering going off-grid in Australia.

There are different types of systems. The quality of the solar inverter also plays a critical role in designing the best off-grid solar system. Reliability is a key concern.

And, finally, there are various brands of solar equipment available in the Australian solar market, and some are better suited to certain applications.

Going Off-Grid

Designing a reliable and efficient off-grid solar energy system is not as simple as many people might think.

Providing power for a small cabin or caravan might not present much of a challenge. But powering an entire house or commercial premises using an off-grid solar power system is a much bigger proposition.

You’ll need to hire an experienced solar system designer and installer to get the job done right.

When you install a solar battery storage system, it needs to be done by a licensed and qualified electrician in this type of work.

Off-grid systems are larger than regular domestic solar energy systems. They have a large energy storage capacity and use high voltage to operate.

If not designed and installed correctly, there is the potential danger of fire or a fatal electric shock. It is essential that any off-grid solar system you have installed complies with all relevant industry standards and regulations, to ensure safe operation.

Off-Grid Solar Systems: 5 Main Components

There are 5 main components in an off-grid solar system:

  1. Multi-mode Inverter/charger
  2. Solar charge controller (DC) or solar inverter (AC)
  3. Solar battery bank(s)
  4. Solar panels
  5. Back-up generator

Coupling – AC or DC?

There are two types of off-grid solar systems: AC coupled, and DC coupled.

What does AC or DC coupled mean?

It refers to the type of electrical connection that links the solar panels to the solar battery storage system or any other type of energy storage device. This can be either Alternating Current (AC) or Direct Current (DC).

A system that uses AC coupling might use a solar inverter, wind turbine, or generator as the source of generation.

In a DC-coupled system, the source might be a Maximum Power Point Tracking (MPPT) solar charge controller or even a micro-hydro system.

The capacity of the solar power system governs whether to use AC or DC coupling. Normally, small solar energy systems (5kW or less) use DC coupling and a solar charge controller.

Large off-grid solar power systems use AC or DC coupling. It depends on the kind of solar inverter/charge controller (multi-mode solar inverter) chosen for the system.

It is important to consider the compatibility of a solar inverter (AC) or a solar charge controller (DC) when designing the system.

Many multi-mode solar inverters today operate in AC and DC coupled modes. This helps build a system that is extremely secure and flexible, offering more than one charging option.

Off-Grid Solar Systems: The Basics

A small off-grid system can be used with a caravan, boat, or small home. The system uses a solar charge controller (solar regulator) to connect the solar panel(s) and solar battery storage.

The solar charge controller ensures that the battery charges correctly and doesn’t overcharge. You can use the output from this type of system to power a basic DC lighting circuit.

A small off-grid solar system uses a basic battery inverter to produce AC power. You can get inverters in different sizes, rated from 150W to 3kW or even higher.

There are two types of charge controllers that use DC coupling. A PWM solar controller and an MPPT solar controller.

If you build a large off-grid solar system, you’ll probably need a maximum power point tracking (MPPT) charge controller, with a 100A rating.

MPPT charge controllers are more powerful than PWM solar charge controllers.

An MPPT solar charge controller is the most effective and efficient way to charge and manage a solar battery system which usually consists of a high capacity lead-acid or lithium battery.

Essential Factors to Consider When Sizing an Off-Grid System

  • Solar exposure – geographic location, climate, panel orientation, shading factors
  • Average daily electricity consumption (kWh)
  • Average steady load (kW) – this is the average load the system must be able to supply
  • Maximum load (kW) – this is the maximum (peak/surge) power drawn by appliances
  • Options for backup power supply – during grid shutdowns/blackouts or extreme weather

After you consider the above factors, you will have a better idea of which type of battery inverter or charger (multi-mode inverter) to choose.

This is the most important component in the solar system. A multi-mode inverter or battery inverter/charger can work in both on-grid and off-grid mode.

Battery Inverter/Charger

If you install an AC-coupled off-grid solar system, the battery inverter or charger needs to have the capacity to provide sufficient AC power for the anticipated load (the appliances connected) under normal operating circumstances.

Also, the battery inverter/charger controls the charging of the battery. And it monitors the energy flow that comes from other sources (solar, hydro, wind, or back-up generator).

How do I choose the best inverter/charger?

You need to choose a battery inverter or charger that has sufficient capacity to power the appliances you regularly use such as air-conditioning units, fridges, and water pumps. These appliances normally generate a high surge in power when they start running.

Inverters/chargers of inferior quality often fail due to the power load when you run multiple appliances together.

The power rating of the inverter/charger must be enough to supply power continuously under all operating circumstances.

This includes taking into account higher temperatures. The inverter/charger must be rated correctly to compensate for any temperature de-rating that occurs (when the operating temperature is 45°C or more, its efficiency begins to reduce).

High temperatures during summer can cause some cheaper inverters to fail, especially if they are transformerless models.

A professional solar power designer or installer can create a ‘load table’. This will help to determine the correct size and type of inverter in line with your consumption needs. The load table can also help in designing the optimal size of the solar array, solar battery storage, and the backup generator needed for your solar installation.

Battery Options for Off-Grid Solar Systems

Lead-Acid

Traditionally, deep-cycle systems using lead-acid batteries have been commonly used in off-grid solar systems. They proved to be effective and reliable and could have a useful working life of 15 years or longer. Especially if they were not required to operate at a temperature higher than 40°C and never completely discharged.

Lead-acid batteries need to follow a precise cycle to optimise the charging of the battery. They also require special temperature sensors to make adjustments in the voltage settings.

Many reputable inverters/chargers used for off-grid systems allow you to program the charging voltage settings and sensors to provide optimal charging in all operating conditions.

Deep-cycle lead-acid battery systems are still common, as they have some advantages over using lithium batteries.

The main advantage of a lead-acid battery is that it does not shut down in low voltage scenarios or when in a low charge state.

Why is this important?

In an emergency or the event of backup generator failure, a lead-acid battery will continue to provide power until it is completely discharged. The downside is, if this happens frequently, it will shorten the useful battery life of the installation.

Lead-acid batteries also offer these advantages:

  • They are compatible with most solar inverters
  • Proven technology
  • Safety, extremely low risk when sealed (AGM/Gel)
  • The battery will continue to operate in a low charge state or low voltage situations
  • Longevity, if not discharged totally
  • Easy recycling

But there are a few disadvantages to consider when using lead-acid batteries:

  • Efficiency is approximately 80% (lower than for lithium batteries)
  • They are heavy and have a low energy density
  • Limited usable capacity – Max 40% depth of discharge (DoD)
  • Lack of modularity – unable to scale up or down once installed
  • Unable to sustain partial charge over a long time
  • Battery life can reduce considerably if regularly operated in high temperatures

Lithium-Ion Batteries

Lithium-ion batteries for solar storage systems have gained popularity in recent years. They offer greater efficiency (92-98%) than lead-acid batteries. Also, they are compact, don’t weigh much, and are scalable.

Unlike lead-acid batteries that are installed with a specific capacity, lithium-ion batteries do not have this limitation. You can add more capacity in the future, which makes lithium battery systems more flexible and easier to work with for solar installers.

Lithium-ion batteries have a greater energy density than lead-acid batteries. Therefore, they are relatively lightweight and smaller.

The greatest advantage lithium-ion batteries offer is that they can maintain a low charge state, or partially charged state over a prolonged period with no adverse effects.

With lead-acid batteries, sulfation can be a problem. This is when the battery electrolyte begins to break down. This is not a problem associated with lithium-ion batteries.

Also, you can charge lithium-ion batteries using a high charge rate; a 70% faster charging time compared to a lead-acid battery is not uncommon.

Lithium-ion batteries offer these advantages:

  • 97% (approx) efficiency
  • Compact and lightweight – high energy density
  • Can handle high rates of charging/discharging
  • Low or partial charge states do not cause degradation
  • Modular – capacity can be scaled
  • Safe to use – low risk

But there are some disadvantages to consider:

  • High temperatures (˃ 45°C) can cause a shutdown
  • Low temperatures (˂ 5°C) can cause a shutdown
  • High surge/peak load may lead to ‘tripping.’
  • Recycling is more challenging
  • Must work with a solar inverter that is compatible

Which is the Best Off-Grid Battery Choice?

Managed Lithium Battery Systems

The best systems incorporating lithium batteries use a battery management system (BMS). This setup uses a dedicated link to communicate directly with the inverter. The battery and inverter must be compatible with the system to operate correctly.

The big problem is when the communication link drops or is interrupted. In such cases, the battery or inverter normally shuts down to prevent either overcharging or discharging of the battery.

One documented example of this problem involves the B-BOX PRO battery manufactured by BYD. Sometimes, when operating at temperatures lower than 5°C, it simply shuts down.

But the B-BOX PRO is still a popular choice for a managed lithium-ion battery system in on-grid solar systems. Why? Because the B-BOX Pro is compatible with many brands of off-grid and hybrid solar inverters like Selectronic, SMA, and Victron.

You can avoid any potential problems associated with B-Box Pro batteries and low-temperature operating conditions. The Chem RESU battery (48V) from LG is a popular choice to install in smaller off-grid solar systems. It’s adequate for a small off-grid solar system but not ideal for larger systems because of its limited 5kW continuous rate of discharge.

If you intend to install an off-grid system larger than 5kW, consider the Chem rack mounted batteries from LG which offer much larger capacity.

Self-Managed Lithium-Ion Batteries

You can choose from various self-managed lithium-ion battery systems on the market. Popular brands include Powerplus Energy, GenZ, Simpliphi, and Discover AES. These self-managed battery systems use a BMS but there is no need for a dedicated communication link to work.

Many of these self-managed lithium-ion batteries are modular. This means that you can build large scale battery storage up to a maximum of 500kWh.

Similar to the managed battery systems, the integrated BMS manages battery charging, monitoring the charge state, temperature, and voltage of the battery cells.

Self-managed lithium-ion battery systems offer one big advantage. You can easily retrofit this type of system to replace a lead-acid solar battery storage system. It’s easy because self-managed lithium-ion battery stems do depend on a dedicated communication link or other similar requirements.

Which Brands are Recommended for Off-Grid Solar Systems?

Based on market feedback from off-grid solar installers and customers, installing a self-managed lithium-ion battery system is the best choice. It offers the most effective and reliable solar storage solution for off-grid solar systems.

The big drawback with most managed lithium battery systems is that they depend on a communication link. And this can be lost or interrupted, especially when operating at low temperatures or in a low charge state.

In contrast, systems using high-quality self-managed lithium-ion batteries are not prone to such problems. Their modular nature and flexibility mean that you can scale up your system and build larger capacity solar storage when you want.

This is a better option for off-grid solar systems. You can also retrofit a lithium battery system.

Leading manufacturers of self-managed lithium-ion battery systems include PowerPlus Energy, GenZ, Simpliphi, and Discover AES.

Lead-Acid Battery System

There are certain circumstances when a high-quality lead-acid battery system might still be a good choice for an off-grid solar system.

Lead-acid battery systems are built using technology that is proven and extremely reliable. They are also compatible with a wide range of off-grid solar inverters/charge controllers.

In terms of reliability in extreme temperatures, a solar storage system that uses lead-acid batteries will not shut down automatically. Also, lead-acid batteries are easy to recycle using recycling technology currently available.

The Battery Inverter/Charger – The Beating Heart of Any Off-Grid Solar System

An off-grid system uses a multi-mode inverter/charger to manage battery storage, solar power, and any generator or UPS.

The multi-mode inverter/charger acts as a central management unit. It can operate in AC-coupled mode with a solar inverter or DC-coupled mode with a solar charger. Or in both modes.

Most early off-grid solar systems used a very basic battery inverter and a separate battery charger. Such basic inverters had limited capacity and were typically rated at 2kW or less. They could only power a light load such as low-energy appliances (fans, lights, or small pumps).

But today most multi-mode inverters or chargers can handle a maximum of 20kW. They have the capacity to deal with high loads. So running appliances with high energy consumption is no problem.

Air-conditioning units, pool pumps, and water heating systems draw a high level of current when starting up, and represent a continuous high power load on a system. But with a good multi-mode inverter/charger, there is no problem with such appliances.

The downside – an inverter/charger that can handle such loads costs more than one used in a regular on-grid solar system or a hybrid energy system of low capacity.

Expect to pay between $1,500 and $6,000 for a 48V rated inverter/charger capable of charging 8kW.

Best Choice for 10kw Off-Grid Solar Systems – Multi-Mode Inverters

You should consider using one of the following recommended inverters in your off-grid solar energy system.

These are the top 3 choices evaluated for a range of factors including reliability, flexibility, power rating (peak and continuous), AC source control, monitoring, software for managing energy, and service.

  1. SP PRO series from Selectronic
  2. Multiplus/Quattro from Victron Energy
  3. Sunny Island from SMA (Germany)

The inverters listed above come with various ratings for power output (kW). So you can buy one that best fits your power consumption needs, considering typical continuous load and surge load conditions.

You can also use any of these inverters/chargers in both AC coupling or DC coupling modes with a compatible solar inverter/controller.

Power Comparison – Off-Grid Inverters

Inverters for use in off-grid systems come with various power output ratings. Their typical continuous output rating ranges from 2.4kW to 20kW.

Inverters can normally handle more than double their rating for short periods, to handle surges in load or decrease in output performance due to extremely high temperatures.

Calculating the correct surge rating needs care because it’s an essential element of designing an off-grid system.

Choosing an appropriate inverter will prevent the system from tripping off or initiating a total shutdown under exceptional load conditions.

Best Choice Inverter for an Off-Grid System with 5kw+ Power Output

1. SP PRO multi-mode inverter by Selectronic

We compared the top brands of multi-mode inverter models and their specifications and output power ratings for a range of operating conditions.

The result – the Selectronic SP PRO range of inverters comes out on top. They have the best rating for 30-minute output and surge/peak power.

But that’s not all, there are three more factors which put the Selectronic inverters in a class above the competition:

  • Dedicated software for optimal energy management
  • 15kW, 63A pass-through power capacity
  • High rate of charging

Of course, top quality inverters come at a price. The Selectronic SP PRO series of inverters don’t come cheap! They are among the most costly in the Australian solar market.

You need to consider the price as just a fraction of the overall investment necessary to install a fully operational off-grid solar system.

It’s worth paying to get the reliability, advanced features, performance, and warranty for 10 years provided by a Selectronic SP PRO inverter.

Specifications

  • Multi-mode inverter/charger with AC/DC coupling
  • Off-grid solar storage, alternative backup power source
  • Transfer switch power: 3.0-20kW
  • Pass through power: internal 15kW (external 28kW)
  • Battery compatibility: Lithium-ion, lead-acid, sodium-ion, flow
  • Battery system voltage: 24-120V

Product Features

  • High transfer switch power rating
  • High surge/peak power output rating
  • Battery temperature sensor for extended battery life
  • Battery voltage monitoring, mid-string sensing for precise charging of the battery (AGM and GEL lead-acid)
  • AC coupling management with Fronius Primo or ABB solar inverters
  • Powerful and easy-to-use software provides monitoring with remote access
  • Safer start-up through pre-charge function
  • Compatible with most lithium-ion batteries
  • Autostart, monitoring, and control for generators
  • Works in AC/DC coupled modes
  • 3 phase compatible with separate solar inverter/DC regulator
  • Off-grid and hybrid compatible with ABB or Fronius solar inverter approved by Selectronic
  • Dual AC sources need extra generator contactor
  • Remote internet monitoring needs Select.live from Selectronic

Price – from AUD $4,500 (4.5kW)

2. MultiPlus by Victron

Best choice for 2-5kW off-grid system

Multiplus hybrid inverter charger

This Dutch company is known internationally as a manufacturer of a wide range of high-quality products. These include battery chargers, battery monitors, inverters/chargers, sinewave inverters, charge controllers, DC/DC converters, and transfer switches.

Victron manufactures extremely cost-effective multi-mode inverter models. The company has an enormous range of inverters of various capacities, including the MultiPlus II inverter/charger.

This inverter/charger represents excellent value for money. It is low cost and works well with systems that are DC coupled. Also, Victron supply remote access, control, and great monitoring options for systems.

Setting up the system is easy, and there is an extensive choice of system configuration options and add-ons available.

Specifications

  • Inverter/charger (AC/DC coupling)
  • Off-grid solar storage, alternative backup power source
  • Power output range: 0.7-4.0kW
  • Transfer switch power: 3.6-11.5kW
  • Battery compatibility: Lithium-ion or lead-acid
  • Battery voltage: 12V-48V

Product features

  • Budget inverter/charger
  • Medium-high surge/peak output power
  • Transfer switch power capability
  • Temperature sensing for extended battery life
  • Autostart, monitoring, and control for generators
  • AC coupling compatibility with a Fronius Primo or ABB solar inverter
  • Dual AC outputs for non-critical loads (only high-power models)
  • Programmable software and App with remote Wi-Fi access
  • 3 phase and parallel connection compatible for higher output power (needs independent solar inverter/DC regulator)

Price – from AUD $1,600 (2.4kW)

3. Sunny Island by SMA

Best choice for off-grid systems in extreme environments

Germany’s SMA is among the leading manufacturers of solar energy technology worldwide. It’s well known for its high-quality solar inverters.

And the Sunny Island range of inverters has been well proven in extreme environments and they perform well even at temperatures below zero.

Specifications

  • AC coupled inverter/charger
  • Off-grid solar storage, alternative backup power supply
  • Power output: 3.3kW-6.0kW
  • Transfer switch power: 11.5kW
  • Battery compatibility: Lithium-ion, lead-acid
  • Battery voltage: 48V

Product features

  • High transfer switch power capability
  • High surge/peak output power
  • Battery temperature sensor for extended battery life
  • Software for remote monitoring
  • Autostart and monitoring of generator
  • Dual AC input (generator and grid)
  • IP54 rating – weatherproof
  • AC/DC coupling
  • 3 phase parallel connection compatible for higher power output
  • Needs independent solar inverter/DC regulator
  • 100% off-grid capability with SMA inverter or similar compatible inverter
  • Needs external auto transfer switch for battery backup

Price – from AUD $3,800

Final Thoughts

So, is it possible to achieve energy self-sufficiency using a 10kW off-grid solar system and battery storage?

Let’s assume that you install a 10kW off-grid solar system, and you can’t benefit from any feed-in tariff (FiT). This means that your best bet is to consume as much of your solar energy as you can. Financially, this is a smarter move than exporting it to the power grid.

Whether or not you can really disconnect from the grid depends on:

Location – There’s a big difference between Darwin and Hobart in terms of the amount of daily sunshine. Darwin gets the most sunlight and Hobart the least.

Roof orientation and angle of tilt – The most efficient setup in Australia is a roof that faces north, with an angle of tilt approximately equal to the latitude of the location. This setup generates the most solar power.

Daily electricity consumption – Do you consume less than 10kWh of electricity per day on average? Minimal consumption will make it easier for you to install a suitable self-sufficient off-grid solar system with battery storage.

Daytime electricity consumption – Do you consume a lot of electricity during the day? If your consumption coincides with sunlight hours, you won’t need to install such a large solar battery storage system. You’ll probably consume most of the solar energy you generate.

Total solar electricity produced – Energy self-sufficiency means having enough battery storage to run your home for maybe three or four days, whether because of a blackout or poor weather. Without a sufficiently large off-grid solar system, you’ll be reliant on a backup generator, which adds to the overall cost.

Is Going Off-Grid with a 10kw Solar System Possible?

The short answer is yes. But a lot depends on your level of electricity consumption, and when you consume it.

With a low level of consumption, a 10kW off-grid solar system will allow you to survive off-grid. Even if your level of consumption is higher, such a system will still be able to run your household in emergency situations, but for a shorter period.

One final point: we looked at the price of inverter/chargers earlier, but the overall installation cost of a 10kW solar system suitable for going off-grid will be in the range of $10,000 to $15,000.

Another option is to go for an on-grid solar and battery storage system. You will still achieve a high degree of energy self-sufficiency but always have the benefit of using the power grid as a backup energy source.