Hybrid and battery solutions

With so much interest around home storage solutions it can be easy to get caught up in the hype. Storing energy is an excellent way to enhance your return from your Solar PV system. Hybrid Solar/Battery solutions provide a step towards energy independence however consumers should be aware of its limitations. Whilst almost everyone would like to be independent from the power grid achieving this is still a costly exercise and in most cases the benefit from a cost only point of view does not make going off grid viable.  Lets take a walk through solar hybrid solutions and understand the benefits and limitations of having a hybrid Grid connect solar and battery solution.

 

The Benefits

• Store your excess solar
• Use the power at night and early in the morning when you are home
• Back-up power if the grid fails

 

The lessor known facts

Most hybrid solutions have a limited current rating which means that during peak usage times even if you had enough stored power it may not provide the amount of power required by the home.

Battery lifespan - All batteries have a lifespan, it is important to understand how long the battery will last and the costs associated with recycling at the end of its life

Back up power - Many hybrid solutions are promoted as having a grid fail backup, this means that when the power goes down in your street your backup kicks in and you are up and running again. The important thing to know here is that in most cases the backup power will only run a couple of circuits in your home. This could be a light circuit and a power circuit for instance. In most cases hybrid systems are not large enough to power the entire home.

 

Lithium versus Lead Acid - Lead Acid is a very stable technology that has been around for time eternal. It is able to store alot of energy and discharge it quickly when needed. Its main limitations are the D.O.D (depth of discharge shown as a percentage of total charge e.g 80% for lead acid, 20% usable charge) and the energy density meaning the space it requires for a battery bank. Lithium on the other hand has a higher energy density and down to 7% D.O.D or 93% usable charge and can be very small in comparison to lead acid. Lithium does have some draw backs however. It is not as stable and is effected by heat more so than lead acid, it is not able to be recycled like lead acid and is a rarer element making the cost of the Lithium Ion battery more.

Most commercially ready hybrid systems are integrating with Lithium Ion technology.

 

The limitations

• As mentioned above a hybrid system is not designed to power your entire home, it is designed to supplement your power requirements
• Unlike solar panels that will last for 25 years or more batteries have a lifespan and this needs to be considered when evaluating things
• It will not wipe out your entire bill. Even if you used no power at all you would still have costs on your power bill including your connection charges
• Back-up power will provide limited circuits in most cases

 

 

The two ways to install home batteries

Currently there are two methods used to install battery storage in Australia:

DC Coupled - The first is to use a multimode inverter.  These are also known as hybrid inverters. Their drawbacks are they only work with battery systems they are compatible with and they cost considerably more than regular on-grid inverters.

AC Coupled - The second method involves using a special battery-inverter.  This controls the charging and discharging of batteries no matter what kind of solar inverter is used.  Because it is attached, or coupled, to a cable that carries AC current, this method is called AC coupling.  Because it does not need to be compatible with the solar inverter, battery-inverters are a convenient way to add batteries to an existing rooftop solar system.

 

Types of battery solutions

Hybrid inverter and compatible battery system

This is an integrated grid tie and battery inverter all in one solution. They can either be retrofitted to an existing solar solution by replacing the existing inverter or as part of a new solar installation

Separate battery inverter and management unit with battery system

Typically AC coupled these units operate separately from the Grid tie inverter and control the charging and discharging of batteries

Integrated DC converter and battery system

This system is installed between the solar array and the grid tie inverter and directs the solar to the batteries when charging and then feeds the power from the batteries when the house requires it.

 

Whats best for me?

If you are wanting to install batteries to an existing solar PV system then you can approach it a number of ways

 

Option 1. Replace your existing inverter with a hybrid inverter and install a certified battery system. The advantage here is that you have a fully integrated hybrid system and the inverter meets current standards.

Option 2. Integrate a battery management unit that is compliant with your existing inverter.

 

If your installing both solar and batteries at the same time then a DC coupled hybrid system would be the most effective

 

If you would like to understand the benefit solar and batteries would have for you please contact us and we will be happy to help you assess your needs

 

If you would like to see some hybrid solutions you can go to our products pages here