When one thinks of energy storage, the AA penlight rechargeable batteries come to mind, or the battery that powers your car. Yet what is energy storage? Or more specifically, what are home batteries?
I mean, to most of us, a rechargeable battery is a mystery.
We connect it to a battery recharger from our main electrical supply. A few hours later, Bob’s your uncle—you can power all manner of electrical devices!
Seriously, though, what is a battery? It’s a device that stores energy. You take energy from one source and store it for later use.
Batteries work by taking advantage of complex chemical reactions. Some of them are quite dangerous actually! Think of the recent Samsung battery recalls due to exploding batteries.
Who Invented the First Battery?
Despite the potential for a meltdown, without batteries though we wouldn’t have remote controls, fun battery-operated toys for our children, or even golf carts—besides a whole host of other things.
So who can we thank for this ubiquitous and rather practical invention?
The first true battery was developed in 1800 by a guy called Volta. In fact, the term Volt, which describes electrical potential within a circuit, comes from the name Volta.
Volta's battery was a fairly simple device.
It consisted of pairs of copper and zinc discs piled on top of each other, separated by a layer of cloth or cardboard soaked in brine. It was called the Voltaic Pie.
In 1859, the first rechargeable battery came into existence, the lead-acid battery. Unfortunately, the lead-acid battery has seen very little innovation since.
There are serious drawbacks to lead-acid batteries though. They’re downright heavy and bulky actually, they’re corrosive, and you can only use 50% of the energy content stored in the battery.
The rest goes to waste—talk about a bad deal!
Most rechargeable batteries in the world today are based on lithium-ion technology, including most home batteries.
What Is a Solar Battery?
The challenge with renewable energy, and this includes solar PV, is that the electrical energy generated varies depending on a number of factors, such as weather, time of day, and shading.
Not to mention that most people produce power during the middle of the day when most families won’t be there to consume it.
In fact, the majority of residential homes use the most electricity early in the morning and in the evening.
The electrical output of your solar PV system increases as the day goes by and normally peaks during the middle before dropping off in the afternoon. Therefore, you are producing the most electrical power when you probably aren’t home to use it!
Hence the need for energy storage with renewable energy. Incorporating energy storage solutions into your home solar PV system has many advantages.
It allows you to store the clean energy your rooftop solar system produces for you when you need it the most, such as in the evenings or mornings.
It can also supply you with backup power, in case of a grid outage. Or even better, allows you to go completely off-grid and cut your connection to the utility networks!
Taking it a step further though, if you have a passion for living in a remote location where there’s no electricity, energy storage coupled with a solar PV system is the only way to go.
Unless of course, you want to go the whole nine yards and be a real hipster by going back to the Dover stoves and paraffin lamps.
Do you need a battery system with your solar panel though? Well, it’s not for everyone, and it depends on what you want to achieve.
If you live in an urban environment with a reliable electrical supply from the grid and a decent feed-in tariff, then it might be worthwhile to opt for a grid-tied system.
One must also consider the cost of a solar PV system coupled with energy storage.
Solar batteries are expensive, and you will need a larger PV system to supply power to your electrical appliances and charge the batteries.
What Types of Solar Batteries Are There on the Market?
So what types of batteries are available on the market for solar PV systems?
Solar PV systems need a specific type of battery. The most popular option for modern home batteries is lithium-ion technology.
This is because lithium-ion batteries are efficient, and are capable of undergoing multiple charges and discharges, which is necessary for home batteries as they are used every day.
One of the electrodes is positive and the other negative. When energy is being drawn from a battery, the electrons flow from positive to negative—this is known as battery discharge.
When batteries are being charged, the flow of electrons is reversed from negative to positive.
So why are batteries inefficient then? The answer: internal resistance. All conductors of electricity have a certain resistance to the flow of electrons, hence the loss of energy in batteries.
Add to this the phenomenon that each time you use a battery, the overall energy capacity reduces.
What about the other types of battery?
Lead-acid was the first rechargeable battery to be developed and was able to provide energy for longer periods of time. It consisted of layers of cells with a lead grid lattice, in which the lead oxide paste was pressed. A few drawbacks of lead-acid batteries, though, are that they are heavy and have a short lifespan of 4 to 5 years. You can only discharge them to 50% of their capacity, too.
Nickel-cadmium is another type of battery that can be used in solar PV systems. It was developed in 1899 and one major advantage it has over lead-acid is that it has a higher energy density than lead-acid batteries. Meaning you can store more energy in it and it has a longer lifespan than lead-acid batteries. However, it’s still prone to low efficiencies.
The battery contains nickel and cadmium electrodes soaked in a potassium hydroxide solution. A disadvantage of these batteries is that cadmium is a highly toxic corrosive chemical, so the safe recycling of these batteries is expensive.
Nickel-iron batteries consist of nickel(III) oxide-hydroxide positive plates and iron negative plates, with an electrolyte of potassium hydroxide. It is a robust battery and tolerant to abuse such as over-charging and over-discharging. It’s often used in backup situations where it can be continuously charged.
Some disadvantages, though, are its poor charge retention and the high cost of manufacturing.
Enter the lithium-ion battery. The lithium-ion battery is a new technology. It’s lighter than lead-acid batteries, you can store more energy in it and you can use more of the energy stored. The lithium-ion battery was invented in 1980 by a guy called Professor John Goodenough.
It’s not confined to only 50% discharge like lead-acid batteries—it can be discharged up to 95%. It also has a much higher energy density than other types of batteries and is lighter.
To illustrate, a lead-acid battery can store only 25 watt-hours per kilogram.
Yet a lithium-ion battery can store a whopping 150 watt-hours of electricity in 1 kilogram of a battery. That’s why it’s set to revolutionise everything that runs off batteries, from cell phones to electric cars and renewable energy.
It’s also a safe technology and has a longer lifespan, yet the technology is still quite costly.
Another disadvantage is that lithium-ion batteries are more sensitive to high temperatures, which results in faster battery degradation.
However, many battery manufacturers have improved their technology to withstand Australian temperatures.
The future of batteries has never looked more exciting thanks to massive investments into battery research and development.
Batteries are already being developed in the lab that can be charged in minutes instead of hours and have much higher energy densities with longer lifespans.
Some of these technologies include the solid-state lithium-ion battery and gold nanowire batteries!
Lithium-Ion and Zinc-Bromide Battery Manufacturers
There are many lithium-ion battery manufacturers that develop modern batteries. Some of them are more well known than others.
The most popular include the following:
The LG Chem Resu range of lithium-ion batteries is a home energy storage solution that you can use in conjunction with your home PV system. It comes in a variety of different energy storage sizes, ranging from 3.3 kWhs to 9.8 kWhs.
A major drawback of the LG Chem lithium-ion battery is that it isn’t designed for off-grid use, but thankfully it can be used a backup power supply in case of a power outage.
The LG Chem Resu battery comes with a 10-year warranty. LG will replace the battery if it loses more than 40% of its energy storage capacity during this period or malfunctions.
And here we thought Mercedes Benz only manufacture high-end luxury cars!
Mercedes Benz now also manufacture small-scale lithium-ion batteries for home energy storage.
Their battery pack, like LG Chem’s, is sized for day-to-day home electricity usage.
The Mercedes Benz battery comes with a 10-year warranty. They will replace it should it malfunction during this period or lose more than 20% of its energy storage capacity.
Z-Cell, a homegrown Aussie battery technology, is unique in that it isn’t a lithium-ion battery but rather a zinc-bromine battery. The Redflow Z-Cell battery is the only zinc-bromine flow battery available on the market. It has some unique advantages over lithium-ion: it can lie dormant for long periods of time without using any electrical discharge, and its storage capacity won’t deteriorate over the lifetime of the product.
The Redflow Z-Cell battery can also be used for completely off-grid applications. It has a 10-kWh energy storage capacity with a continuous output of 3 kW. The battery also has a 10-year or 30 000 kWh warranty, whichever comes first.
Last but definitely not least: the Tesla Powerwall. The Tesla Powerwall entered the scene a few years back. Elon Musk promised to scale up and commercialise the production of lithium-ion batteries to make them more cost-competitive.
The Tesla Powewall is now into its second generation, with a third generation in the pipeline. Let’s look at some of the specs of the Tesla Powerwall 2. It’s most probably the sexiest looking battery you will see around.
It can be installed indoors or outdoors and comes in a 14-kWh energy storage size. You can also connect multiple Tesla Powerwalls to increase the capacity, making it a scalable solution.
The Powerwall 2 also includes an integrated inverter that converts the DC power generated from the solar PV system to AC power that you use in your home. It has some cool features too, such as being able to monitor and control the energy usage through an iPhone or Android smartphone.
It also holds 70% of its energy storage capacity after 10 years and has a 10-year warranty. The Tesla Powerwall 2 can also be used in off-grid mode.
It can be quite daunting to decide if one should opt for an energy storage solution and, if so, which battery technology and how many.
Much of this depends on what you want to achieve. Do you want to increase your daily self-consumption and decrease your reliance on the grid? Or do you want to go completely off-grid?
Planning how much energy storage you require for your home is quite a complex and tricky process.
If energy storage is something you want to look at, then it’s worth talking to a reputable solar PV installer that can help you make the right decision.
If you want to see how much solar or battery storage could save you over the next 5 years, then take our solar saving calculator quiz below!
Or talk to an Instyle Solar expert about the best solutions for home energy storage or PV-panels.
Otherwise, head back to the solar blog to find even more great educational content.