Off-Grid Power Systems

Off-Grid Systems: How Do They Work?

Electricity from the solar panels powers daytime loads with surplus generation recharging the batteries. Overnight, your house electrical loads are powered by your batteries. If you don’t have enough electricity from either your solar panels or your batteries, your system will automatically turn on the backup generator to supply the shortfall.

There are a couple of approaches to integrate solar;

AC-Coupled solar (shown on the roof of the house in the image below) is when DC solar electricity is converted to AC electricity by an inverter, and sent to your household appliances through your switchboard. The battery inverter/charger converts the AC electricity back to DC to charge the battery bank as needed.

DC-coupled solar (shown on the ground frames in the image below) is when DC solar electricity is sent through a regulator or charge controller directly to the battery bank first. The battery inverter/charger then converts this to AC electricity and sends it to your appliances as needed. 

Both AC and DC coupled solar have their pros and cons, and you can even include both options in your system design if preferred.

Off-Grid Power System Design & Load Profiling

Our off-grid expert consultants will assess your energy requirements, considering any expected growth or reduction in your future energy needs. It sounds time-consuming, but our team has been doing this for over a decade and can complete an Energy Load Profile quickly and painlessly. We’ll also assess and determine with you the best location to install your equipment and then recommend ideal stand-alone solar system designs.

All off-grid power system components and sizes are carefully chosen for many factors, including; functionality, capacity, performance, longevity and cost. Your Energy Load Profile information, or specific energy demand, forms the basis of equipment and system design recommendations.

Energy Load Profile

Completing an accurate energy load profile is an essential part of correctly designing an off-grid stand-alone solar system ensuring your wise investment and power reliability. The load profile is a list of all your appliances and utilities that require electricity with an estimate of their usage frequency (e.g. how many days per week, and hours per day). Once we have this information our accredited system designers will review and confirm your energy requirements to progress to our tailored system design phase, accurately recommending appropriate stand-alone power system options and sizes for your needs.

If you’d like to fast-track things and get a quote quickly, you’re welcome to pre-fill your Energy Load Form, found here, before contacting our team.

Our Considerations

Stand-Alone System Location
Your equipment location is very important when designing an appropriate off-grid power system. We will discuss what will work best for your site while paying careful attention to system performance, longevity, and compliance.

Solar Array
There are a number of approaches to integrating solar. It must be capable of producing enough electricity (kWh) to replace what is used by your site on any given day – especially on days of poor weather. Our design software considers local weather data, solar panel orientation and inclination to precisely calculate expected solar yields to best determine your ideal solar size.

Off-Grid Batteries
Selecting a battery with the right chemistry, configuration, capacity, and power output is incredibly important to ensure your system’s stability, reliability, and longevity. Our design consultants will consider our range of leading off-grid-compatible batteries to find what will be best for your application.

Inverter/Charger
The inverter/charger needs to be carefully sized to accommodate the continuous and surge power (kW) requirements of your site and appliances. As part of our Energy Load assessment, we will discuss what appliances could operate simultaneously to determine your ideal inverter/charger capacity.

Generator
While our typical off-grid system design approach doesn’t place heavy reliance on backup Generators, they still play an important support role, and careful thought and planning is needed when it comes to their installation and operation. The generator should be installed as close as practical to the stand-alone power system equipment while also considering noise level and adequate safety protection when in operation.

System Configuration Options

Here are a few system configuration options available for off-grid system design. Your system designer will be able to explain which design they’ve recommended for your project, and why.

System Configuration Overview Table

AC Coupled Off-Grid System (Managed Solar)

Your solar inverter converts DC power produced by your solar array to usable AC power which directly powers

your appliances with surplus generation recharging your off-grid systems batteries via the inverter/charger. In the absence of solar, your off-grid systems batteries discharge to meet your energy demands via the inverter/charger with any shortfall provided by a backup generator. This latest system design provides the most efficient daytime power to your appliances, with solar production capable of power layering with battery power in the event of high daytime loads. Uniquely, ‘managed’ solar inverters are controlled by direct data connection ensuring your systems power output remains clean and stable when solar generation is regulated.

• Latest System Design 
• Efficient Solar Direct To Load 
• Direct Data Controlled Solar 
• Clean & Stable Power Output

AC Coupled Off-Grid System (Unmanaged Solar)

Your solar inverter converts DC power produced by your solar array to usable AC power which directly powers

your appliances with surplus generation recharging your off-grid systems batteries via the inverter/charger. In the absence of solar, your off-grid systems batteries discharge to meet your energy demands via the inverter/charger with any shortfall provided by a backup generator. This latest system design provides the most efficient daytime power to your appliances, with solar production capable of power layering with battery power in the event of high daytime loads. ‘Unmanaged’ solar inverters are controlled via Frequency Hz Shifting when solar generation is regulated affecting power output quality which can impact sensitive appliance operation.

• Latest System Design 
• Solar Inverter Ratio (1:1)
• Efficient Solar Direct To Load 
• Frequency Hz Controlled Solar

AC/DC Coupled Off-Grid System (Managed Solar)

This system has dual solar inputs connected via solar inverter(s) to the AC switchboard (AC coupled) and via solar charge controller(s) to the battery bank (DC coupled). AC coupled solar inverters are controlled via direct data connection from the inverter/charger, while solar charge controllers are directly connected to the battery bank self-regulating according to battery bank voltage. In the absence of solar, your off-grid systems batteries discharge to meet your energy demands via the inverter/charger with any shortfall provided by a backup generator. This system design maximises system performance, while maintaining a clean and stable power output when solar regulates due to ‘managed’ solar inverters.

• Optimal System Design & Redundancy 
• Leading System Efficiency & Power Layering 
• Direct Data Controlled Solar Inverters 
• Clean & Stable Power Output

AC/DC Coupled Off-Grid System (Unmanaged Solar)

This system has dual solar inputs connected via solar inverter(s) to the AC switchboard (AC coupled) and via solar charge controller(s) to the battery bank (DC coupled). AC coupled solar inverters are controlled via Frequency Hz Shifting from the inverter/charger, while solar charge controllers are directly connected to the battery bank self- regulating according to battery bank voltage. In the absence of solar, your off-grid systems batteries discharge to meet your energy demands via the inverter/charger with any shortfall provided by a backup generator. This system design maximises system performance, with a slight variation to power output quality when solar inverters are regulating which can impact sensitive appliance operation.

• Optimal System Design & Redundancy 
• Leading System Efficiency
• Daytime Power Layering 
• Frequency Hz Controlled Solar Inverters

Managed or Self-managed Batteries – Which is Best?

The main difference between managed and self-managed lithium batteries is where the BMS is located – either within the battery itself (self-managed), or as a separate piece of hardware (managed). For more detailed info, check out our article here.

Self-Managed Battery Advantages

• Modular and versatile
• Inbuilt redundancy, battery module failure bypass
• Wide compatibility and can directly replace existing VRLA batteries

Self-Managed Battery Disadvantages

• Slower charging
• Less accurate SOC monitoring

Managed Battery Advantages

• Fast and accurate charging
• Highly accurate SOC monitoring

Managed Battery Disadvantages

• Battery fault results in shutdown & power loss 
• Battery group communication loss results in shutdown & power loss 
• Reliant on identical battery module firmware

Our consultants are off-grid power system experts and have an in-depth understanding of battery configuration and operation. We will discuss and recommend the most suitable option for your project.

Grid Connection Cost

Determining the cost to connect grid electricity to your new property or new build is an important first step when deciding whether to live on or off-grid.

Often the power lines will appear quite close to your dream block of land but when you begin to chat with your electricity distributor about the cost of getting power connected you can get a nasty (expensive) surprise.

It is not uncommon for a quote to connect to mains power to be in the tens or even hundreds of thousands of dollars. This can make an off-grid power system a much more affordable option upfront and of course, long term.

Off-Grid Energy Australia can assist you in obtaining an accurate cost of connecting electricity to a new property with the electricity distributor for your area. Just contact our friendly team.