What Are Hybrid Solar Systems? Inverters, Batteries, Benefits and More

    Introduction

    Most households and businesses consider only two options while going solar—grid-connected solar system and off-grid solar system. But there is a third option—hybrid solar system, which combines the best features of grid-tied and off-grid systems. Hybrid solar systems offer you the benefits of grid-connected systems, like the ability to earn feed-in-tariff credits and also the convenience of being off-grid.

    While hybrid solar systems usually cost half the price of an off-grid system, they are more expensive than purely off-grid solar systems. However, the benefits of solar battery storage are encouraging more and more people to purchase hybrid solar systems. This article will take you through the basics and benefits of an Australian hybrid solar system at home and your workplace.

    Using only a hybrid inverter: What is a ‘battery ready’ solar system?

    A hybrid solar system is the same as a grid-tied solar system, but it uses special hybrid inverters and batteries to store solar energy for later usage. Traditionally, the term ‘hybrid’ means two different power sources such as wind and solar, but in the solar industry, it is used to refer to a system that uses a combination of solar panels and batteries to interact with the electricity grid.

    Battery-ready solar systems use a hybrid inverter instead of a regular string solar inverter. Most modern hybrid inverters come with a built-in battery charger and connection. They make it easy for you to add a battery in the future, although if you can’t add batteries at the initial installation, finding compatible batteries after a few years may become difficult as the technology is advancing rapidly.

    Will you need hybrid inverters to add batteries?

    No, you don’t need a hybrid inverter to add batteries to your system. You can add a battery to any grid-tied solar system using an AC battery system. There are many such popular AC batteries available in the market and more alternatives are also becoming available. As inverter and battery technologies are evolving exponentially, it may not be always worth spending extra money on ‘battery ready’ systems. You may consider a battery ready system only if you are going to add a battery within 2 years of initial installation because if you wait too long, the system may become outdated. 

    Advantages of hybrid inverters over traditional solar inverters

    The latest hybrid inverters can manage the charging of batteries and energy inputs from multiple sources. Their programmable features and integrated components can help you achieve maximum cost savings and higher efficiency. For instance, you can program the hybrid inverter so that the batteries can be charged via solar panels or the grid. Similarly, you can add multiple power sources, such as generators and wind turbines. Hybrid inverters also make it much easier and cost-effective to move from grid-connected to hybrid solar systems

    Why store solar power in a battery?

    Many distributor networks and governments have decreased the feed-in-tariff rates. This means traditional grid-connected solar systems have become less appealing as most people are working during the and are not home to self-consume the solar energy as it is generated, thus it is fed back to the grid at a negligible sum.

    Whereas, the solar battery storage in a hybrid system stores the surplus solar energy to provide backup power when you are home during the evening and when the grid goes down. This can be a perfect fit for a common Australian household, although, for most businesses that operate during the daylight hours, the regular grid-connected solar system would still be an economical choice.

    Here are some more advantages of having a battery storage system installed:

    • Allows you to store excess solar energy or you can say off-peak (low cost) electricity
    • Allows the usage of stored solar energy during peak evening time, known as self-consumption or load-shifting
    • Reduces power consumption from the grid
    • Enables advanced energy management

    Types of hybrid solar systems

    Hybrid solar systems usually fall into one of four major categories:

    1. Using basic hybrid inverters with no backup power

    This is the most economical option that uses a simple hybrid inverter containing a solar inverter and battery inverter-charger with clever controls to determine the most efficient usage of your stored energy. It works like a grid feed solar inverter only, but also allows the storage of solar energy in a battery system for self-consumption.

    The major drawback of this type of inverter is that it does not have a grid isolation device, which means it cannot supply electricity when there is a power blackout from the grid side. It can be a great economical choice if grid stability is not an issue in your area.

    1. Multi-mode hybrid inverter with backup power

    Multi-mode hybrid inverters, also known as advanced hybrid inverters, have backup power capabilities either built-in or as a separate add-on unit. Under the standard operating condition, it supplies power to the appointed power circuits, charges the batteries and feeds the excess power back to the grid.

    If the grid becomes unstable or goes down, the unit will automatically switch over to battery supply in less than 1 to 3 seconds to operate independently from the electricity grid. While some multi-mode hybrid inverters have full backup power ratings, most of these systems have very limited backup capabilities that can run only basic circuits during blackouts like lighting and fridge. 

    1. All-in-one battery energy storage system (BESS)

    Technically known as a Battery Energy Storage System (BESS), is a more recent trend in which hybrid inverters are packaged together with a battery system in one complete unit. They come in a variety of capacities and usually are the size of a medium-size fridge. These systems can easily be retrofitted to the existing solar system.

    There are mainly two types of BESS systems—those with AC-coupled battery systems and those with DC-coupled solar inverters. 

    1. Advanced AC-coupled hybrid systems

    Before the cheaper hybrid inverters fled the market, most hybrid solar systems comprised two different inverters—a standard solar inverter and a sophisticated multi-mode battery inverter. These inverters work together to form an AC-coupled system.

    Here, the solar inverter must be the same brand or compatible with the interactive or multi-mode inverter for optimum battery charging. The bidirectional/interactive inverter acts as a battery inverter-charger and completes the power management system. It also uses clever programmable software to optimise energy usage. Interactive inverters operate in the same way as off-grid inverters, but they control the grid connection.

    As you can see, there are a wide variety of batteries available in the market from several battery manufacturers. You should be able to make out how long you can expect the batteries to last because no battery manufacturer is warranting the batteries for over 10-years.

    Adding batteries to the current regular solar power system

    If you already have a grid-connected solar power system, you can add batteries to convert it into a hybrid system. However, make sure that your system size is at least 6.6kW to ensure compatibility with the solar battery storage and to generate enough electricity to charge your batteries in winter and overcast weather.

    If your system’s size is under 6.6kW, consider adding more panels unless your household is efficient with a small battery pack. The easiest way to retrofit batteries to your existing solar system is to use AC coupling. This means you will not need to alter the existing solar wiring and simply connect the battery into the house’s existing 230V AC circuit. This is a classic example of a BESS hybrid system.

    How much does a hybrid solar system cost?

    The extra money you can expect to pay for a hybrid system compared to a standard on-grid system depends on how many batteries you want. A hybrid solar system would cost more than double the price of a regular on-grid system.

    A good-quality installation of a 6.6kW solar system costs about $7,000. Add 10kWh of the usable solar battery storage system, which is a decent amount for an average Australian household. Then you can expect to pay $18,000 for the complete hybrid system.

    Is hybrid solar worth the extra money? Benefits of installing a hybrid solar system.

    Hybrid solar systems may not be an excellent choice for an economic investment yet, although it is worth investing in for many benefits mentioned below:

    • Uninterruptible power supply (UPS): Buying a hybrid solar system would mean that when the grid goes down, your system will keep flowing electricity. In the event of a grid failure or blackout, while a standard grid-tied solar system will shut down to protect the line workers making repairs to the wires outside, the hybrid solar system will safely disconnect your house from the grid. You can continue to run certain appliances using batteries and solar during the daylight hours. Also, during the night, when energy is not being generated, batteries will provide backup so that life goes on without interruption.
    • Get your electricity bills further down: As we consume 70% of the power in the evening, it makes sense to store it using solar battery storage and use it later. Also, it would be unfair to send your generated solar electricity into the grid for half or even less of what you pay your electricity retailer. So, by investing in a battery, you can reduce your power bills to $0.
    • Hybrid solar systems are fully programmable: The best thing about hybrid systems is they can balance and control the available sources of energy. 
      • Suppose that power produced by your solar array is insufficient to supply your daytime loads and to charge your batteries. Then, the system will charge your batteries via the grid when a lower off-peak electricity rate is available.
      • When your electricity usage crosses a certain level, retailers may charge you higher electricity rates for this increased level of demand. Here, hybrid solar systems can offer you ‘peak lopping’, which means you can draw stored energy from the batteries to help balance the power usage.
    • Hybrid systems will help you overcome ‘export limits’ and system ‘size limits’: Some local electricity network operators like to control everything. They will have more regulations than usual and tight restrictions on maximum solar system sizes. They would claim that their grid cannot handle additional electricity than larger solar systems provide, although it wouldn’t be an issue to install a 10kW air conditioner that pulls a significant amount of power from the same grid.

    This often leads to homeowners being forced to settle with a much smaller size of solar power system than they need to offset their power bills. Hybrid inverters can be configured to have a maximum export rate that is significantly less than what your system can generate when the sun is outshining. For instance, if you have a 10kW solar power system, you can export only 2kW of energy while diverting the remaining 8kW power to your batteries.

    • Make the most of your electricity tariff: The electricity distributor network has introduced ‘time of use’ tariffs in some states, which means electricity from the grid will cost more during periods of peak demand. The hybrid solar system allows you to set it such that when prices are high, you will draw power from your batteries or solar panels. Also, if your batteries need a top-up during winter or overcast weather, you can program your system to charge your batteries using off-peak tariffs only. 

    With the help of some special hardware, you can even configure the charging and discharging pattern of your solar battery storage to adjust their charge/discharge periods according to the change in pricing structures in the future.

    Conclusion

    The first step to ensure that a hybrid solar system fits your energy consumption profile is to make your household or workplace energy efficient. It’s not always about money. So, if you are ready to invest in a hybrid system, it will empower you with energy security and self-sufficiency. It will provide an uninterrupted power supply and future-proof your energy demands against the rising costs of electricity.