Now, while you don’t need solar battery storage as part of your solar energy system, any excess energy can be sold back to the grid, and the grid will always want it.
The grid will happily pay you for your excess energy, but they’ll never pay you what they charge you – so if you’re buying energy, it’ll cost you more than storing it.
You can also sell energy from your batteries!
Yep, some energy suppliers will buy energy that you’ve stored in batteries.
Plus, while none of us will be going off-grid solely using solar for good while, when we do we will all need battery storage.
The reasons for getting battery storage include:
- Sell stored energy back to the grid.
- Use energy you generate after the sun goes down.
- Avoid peak energy costs buy using stored energy.
- Future proof your home.
Now, selling energy back to the grid still has a bit of stigma attached, as the ‘FiT Years’ are responsible for the UK Solar ‘Wild West’ years – with customers being overpaid for energy and unscrupulous installers selling bad systems.
Well, the world has changed and now the solar industry is much more regulated, so the process of buying and selling energy is much less chaotic.
What is the most popular storage solution on the solar battery market?
Lithium-Ion batteries
These will be the batteries you are offered when you are looking for storage for your solar energy system. There are the most cost effective, reliable and technically sound batteries on the market.
The reason Lithium-Ion batteries have become the main offer on the solar market is because they are used in Electric Vehicles. This means that, because cars need small, reliable batteries, the technology has advanced to the point that batteries that can be charged and discharged 1000s of times
Good stuff:
Low maintenance – Lithium-Ion batteries just work without being messed with.
They have something called ‘high energy density’ – this means they can hold more energy per cubic centimetre than lead acid batteries.
You can use almost all the energy stored in a Lithium-Ion batteries – which is referred to as a ‘high depth of discharge’. The more energy you can use, the more efficient your battery is.
A Lithium-Ion battery can be charged and discharged many, many times – this means they can last for 10 years or more.
Bad stuff:
Lithium-Ion batteries re not expensive but they are more expensive than lead acid batteries – which is the ones you’ll find in your car.
Thermal runaway is something that has been rather overstated in the press, but it can happen on very rare occasions. It means the battery can catch fire. If your battery storage system is competently installed by a qualified, MSC registered installer, there is almost no chance of your battery combusting.
What are Lithium-Ion batteries used for:
Lithium ion batteries are the industry standard in domestic solar installations these days. They hold a good charge relative to their size so they are very cost effective so they are great for powering homes.
What price should I pay for a solar battery?
It’s not very helpful but: it absolutely depends on your inverter, how you want to use your energy, how much you want to store and … well, a million different factors.
What you do need to do is make sure the battery you choose is suitable for your unique needs.
Lithium-Ion batteries
As stated early, these are the main solar system batteries on the market, and you are unlikely to be offered anything else at the moment.
The price of a Lithium Ion battery will be effected by the brand name, materials and it’s capacity.
Prices range, rather unhelpfully for this blog, between £1000 and £11000 depending on the above so we can’t really recommend anything in particular.
How many solar batteries do I need?
Again, the question itself here is a little unhelpful as the answer could one if it’s a 13.5 kWh Tesla Powerwall, or ‘lots’ if it’s a SigEnergy rack system that comes in 5kWh units.
To work out what you need you’d need to work out what energy you use, what energy you want to export and what your home may look like in the future.
Another thing that’s worth looking at is the ‘load’ your home uses. A ‘load’ is the amount of energy you use at one time.
For instance, if you are sat watching telly late at night with one light and no heating, the load on your battery would be very low – this means the battery will discharge at a ‘normal’ rate.
However, if you are using the washing machine, have a few heaters on and all the kids are playing video games, then the load on your battery will be quite high – causing the battery to discharge much more quickly.
If you used the washing machine THEN the kids played their games THEN you put the heaters on – unlikely as the kids will demands heating at all times – the battery will last longer and discharge more slowly.
It sounds strange, but that’s physics for you!
This is how we should all be using energy whether we are into renewables or not – when you have a solar storage system, more intelligent use of electricity will become second nature.
Ofgem state that a typical UK household uses 2,900 kWh a year – if you just wanted to cater to that, a 3.2 battery would serve you well … until you change the heating over electric so always keep an eye on the future.
Some schools of thought say if you have a panel array that produces 3 kWh a day then there is no point having 2 x 3.2 kWh batteries fitted – but we say ‘Fill those batteries with cheap energy overnight!’.
What are solar batteries made from?
In the UK 99.9% of domestic solar energy installations use Lithium Ion batteries.
Solar batteries are no different to any other kind of rechargeable battery in the way they work, but they need to be more robust than the ones you have in your remote control.
Lithium Ion
Inside your Lithium Ion battery there are two plates – a copper one at one end, and an aluminium with the chamber between them filled with an electrolyte, or semi-conductive solution.
In between the panels is a porous separator that, for reason too complicated to explain here, cause a potential difference between the plates,
That creates current and, therefore, energy.
Professor Brian Cox can probably explain it better.
Who installs solar batteries?
Electricians is the comprehensive answer.
Solar storage systems are just electrical circuits at the end of the day, and most qualified electricians would understand how they work and how they are fitted.
However, to avoid any problems in the future with upgrades and exports, ensure the electrician who fits your solar system and batteries is MCS registered.
MCS is, currently, the only government baked regulator for the renewables installers and products.
What is the lifespan of a solar battery?
The best way to determine the lifespan of a battery is to look at the warranty.
No serious company would offer a warranty that they weren’t 100% sure was feasible for the product.
A good quality battery from a tier 1 brad would usually come with a 10 year warranty – so the battery itself will probably last between 11 and 15 years.
Mis-use of a battery will shorten it’s life though – if you store it somewhere to cold, or too hot … if you force charge it too much … or if you damage it physically.
Charging and discharging a battery in the wrong way can also shorten its life but solar energy systems are so well controlled by various apps and other software that this is unlikely to happen.
Pros and Cons of installing batteries.
Pros
Use everything you generate from your solar panels.
Use self-generated energy after the sun goes down.
Plus, you can store energy from the grid and THEN sell your excess energy BACK to the grid when they’ll pay you loads of cash for it!
Cons
The initial outlay can be expensive
They will need replacing twice during the life tie of your panels.
A few energy suppliers won’t take excess energy from batteries.
Will a solar battery save me money?
Yes, a solar battery will save you money.
There’s no hard sell or subterfuge here, it’s simple maths.
Electricity costs, say, 24p per kWh at peak times – you have a battery you either filled with free energy generated by your panels, or with cheap energy from the grid during the night.
If you use the batteries at peak times your either saving 24p per kWh or, if you were paying 9p per kWh during the night you’re saving 15p per kWh.
There’s no way round the fact you’re saving a huge amount every month.
Are there any grants available for solar batteries in the UK?
Not at the moment – but who knows with the new renewable drive here in Blighty.
ECO4 is a government run scheme that is available until 2026 - so there may be funds available there if you want to go green.
Plus, solar systems are completely exempt from VAT and that includes all the bits – from panels to the battery.
What other batteries can be used to store your energy?
Lead acid batteries
These are used in cars with traditional engines.
They can be used in solar energy systems, very popular in the States with DIYers, but the tech is pretty outdated, so you won’t see many of them in the UK.
Invented in the 1800s, they have been a mainstay of electricity storage tall over the world and, as they can almost completely discharge without damage, they are pretty reliable,
Unfortunately, they are also prone to over-charging, they can be easily damaged, they get very hot and, because of this, need a lot of regular maintenance.
Pros:
Much cheaper than almost all other rechargeable batteries.
Because they’ve been around a while they are easy to recycle.
While they need maintenance, it’s simple and can be done by you. .
Cons:
Can not go in confined spaces as they get hot! .
If you damage the casing, they’ll leak acid everywhere.
They need that regular maintenance.
Generally last around 5 years.
Best for:
Certainly not the inside of your home, so maybe outside in an off-grid solar system oor, as mentioned, to get your diesel/petrol car started.
Nickel cadmium batteries
We don’t know what was in the water in the 1800s but they were inventing new types of battery left, right and centre – and one of them utilised Nickel cadmium (Ni-Cd).
Cadmium is very dangerous to humans, so it’s no surprise that in Europe, and a lot of other places, they are either restricted or banned.
Due to their unsafe nature, Ni-Cd batteries are usually reserved for commercial use – like aircraft and utility storage facilities.
Pros:
Ni-Cd batteries operate at extreme temperatures.
Ni-Cd batteries don’t need complex battery management systems
Pretty much indestructible.
Cons:
They’ll kill you!
Use in the UK is very restricted.
Nowhere to recycle.
Ability to hold a charge decreases over time.
Best for:
Industrial or commercial settings where they can be maintained and operated safely.
Flow batteries
Flow batteries VERY new and still in development, but they are available commercially inn some countries.
Water-based electrolyte flows between two chambers inside them – this moving liquid means charged particles can be easily stored and then discharged.
Flow batteries are used to store large amounts of electricity, so they tend to be massive – certainly too big to go in a cupboard under the stairs.
Pros:
Flow batteries can completely discharge without any damage to the battery itself.
Water is fire retardant, so much less chance of thermal runaway!
You’re looking at a 30-year lifespan!
Cons:
They are very expensive.
They may be big, but they don’t hold much energy.
Absolutely massive.
Best for:
Industrial power storage, community solar projects and anyone using a huge amount of power.
Graphene Batteries
Take 2 sheets of graphene, 2 atoms thick, one positive and one negative, and suspend them in distilled water and you’ll have a power differential and therefore a current.
What is Graphene? It’s a super material with some amazing properties which, in a battery, include increased storage capacity and reduced heat.
Graphene is actually Graphite – which you’ll find in a modern pencil.
But, unlike, a pencil ‘lead’, the atoms aren’t all bunched together, they are laid side by side to create Graphene.
Believe it or not, this makes the Graphene 100 times stronger than steel.
As well as being super strong, Graphene is an amazing conductor, so it’s perfect for batteries.
Graphene can also be used in solar panels!
You won’t be seeing many graphene batteries or solar panels as 2 layer Graphene for a panel would cost around £8,000!
Conclusion
A solar energy system will be even more cost effective if you store our excess energy in batteries.
