Storing electricity at home

[Van-Wild]

I've got an array of large and surprisingly efficient solar panels on my house, 18 of them to be precise. We had them installed 7 years ago and we get a nice little pay back every quarter, by selling surplus electric back to the grid.

Now, here's what's got me thinking.... the inverter just packed in. It appears ours was designed to only last five years, so it's done us good. The cost of a better replacement will see me pay out nearly a grand, and I'm OK with that as the new one will last a minimum of ten years and is more efficient.

When I get a professional to fit the new inverter, do I also get some deep cycle batteries installed to store my surplus electricity rather than sell it back to the grid? And if I do, what type should I use? Is it worth it? How does it all work? Has anyone done it?

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[TeeDee]

This is a good guy to take a deep dive with on the subject matter

 

[Mesquite]

If you've got a hot water cylinder with immersion heater you could store electricity in the form of hot water

 

[Robson Valley]

I have a bank of deep cycle batteries to store the juice that I don't need immediately. Plate area defines current storage. Fact. So I bought pairs of 6VDC DC batteries and connect them in series for 12VDC. Those are laddered in parallel with other pairs which feeds my inverter.

If and when we have a serious outage in midwinter (night, -20F, snowing and windy), I have invited all my neighbors to bring blankets and pillows and camp in my house because I am damn determined to sail through it

If anything, more storage is the way to go. Your inverter feeds off the batteries, nothing else.

We have no means of selling juice back to the grid. If anything, they do not want it. For fear of their employees getting whacked in a grid failure.

 

[TLM]

I think still at the moment lead batteries are the cheapest and simplest way. Vanadium flow batteries are for the moment for larger uses.

The amount of batteries depends on two things, charging capacity and user need. Both have to be known. It is not exact but still one needs the numbers.

I used to run the cottage on solar panel/diesel generator charged lead acid deep cycle batteries. Works but there is never enough power when you really need it. That's where the generator comes in.

 

[Van-Wild]

This is a good guy to take a deep dive with on the subject matter

Thank you. I'll give that a good watch

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[Van-Wild]

The amount of batteries depends on two things, charging capacity and user need. Both have to be known. It is not exact but still one needs the numbers.

Thank you. How do I work this out and what does it mean?


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[TLM]

Thank you. How do I work this out and what does it mean?

OK, assuming you have 12V DC coming out of SP and 12V batteries and after inverter 230V AC.

User load is the easiest, you count the max amount of power needed to run all the appliances you intend to run from the batteries (at any one moment), you count the continuous power you intend to run. The first gives you the size of the inverter and the second the energy needed (usually in kWh) (often counted over a 24h period for convenience). This is not exact but gives one the first approximations.

Often the batteries are oversized to 1.5 or 2 to the energy need (as the usage is mostly underestimated). The energy used also gives the amount of panels needed for charging. Of course the whole thing can be averaged over a longer period than 24h but that increases the amount of batteries needed quite considerably.

 

[Broch]

The other way to look at it is to treat the main grid as your battery bank

If the price you get paid for the surplus less the price paid for power when you need it is a credit, that's your best option. If it's a deficit, is the cost over five years more than the set of batteries you will have to buy? if it is, it's worth getting batteries, if not, stick to the grid as your storage.

 

[TLM]

Yep, from purely financial view point it works like that.