An 80 m2 home CALB battery bank and solar setup

Hi!

I'm new here and was wondering if you could suggest a cheap but good quality solar system with CALB cells for an 80 square meters (around 900 square feet) house.

I'm looking for some cheap but good quality solar panels, a 3-5 days lasting battery bank and everything in between (inverters, bms...). Something that is safe for my small home. I'm an average energy consumer: computer, fridge, freezer, electric water heater, electric owen, TV, dishwasher, washing machine, your basic home stuff. Everything works on 220V.

Your help will be greatly appreciated! ?

Do you have a better idea idea of your daily/monthly/annual electricity consumption, and does it vary seasonally? It should be easier then to size the PV+battery system you would need.

Also do you intend to go completely off-grid or will you still have access to an electricity provider for bad weather days? Because the size of the battery bank and generally the whole system can differ by a lot depending on whether you can afford to have your battery empty 5% of the year or 0% of the year. Indeed having an auxiliary electrical power source for these 5% of the year helps a lot to reduce the investment cost.

You can play around with this website run by the EU to have an idea about the sizing of your setup: JRC, input your location, then under "Off-Grid" tab you can fill the PV power, battery bank size, daily consumption etc... You can get such graph to see whether your system would be enough depending on the time of the year:


About the cost, PV power is rather cheap (about 300-500€/$ per 1 kW peak power) while battery banks tend to take a larger part of the budget (250-500€/$ per kWh stored for LiFePO4, depending on DIY or not). Also beware about your local regulations, depending on whether you are tied to the grid or not you can have a cap for the maximum PV power you can install on your own, I know it's the case in France for safety reasons.

But in the end to get a better idea of what would make sense financially you really need to know your electricity consumption.

Thanks for your answer!

My daily consumption would be around 8 kWh (throughout the year), so I guess I'd need 24 kWh battery for 3 days of autonomy. Now, I've found a solar power calculator and this is what it calculated for 2000W of panels:

If I'm correct, I would need 5 x 100ah 48v (5120wh) Battery Kit for US $1,683.00 each and 20 x Rich Solar 100W Poly panels for US $88.99 each.
That's US $10,195.00 just for the panels and batteries.
I wouldn't be tied to the grid because that's still very expensive here in Croatia.
I tried JRC, but didn't get anything that I can understand. You see, my roof is about 30° sloped and oriented to the south. This is what I get when I punch in the numbers:

Seeing all those red bars doesn't seem right...

2kW solar panels would give a maximum of about 10kWh produced assuming 5 hours of sunlight (in summer). Using 8kWh on average, this gives very little left to actually charge your battery, and in winter when you don't have the 5 hours it will be much worse. Your battery size is pretty ok, but you would want to put a lot more solar, or find a way to scale back your usage.

upnorthandpersonal said:

2kW solar panels would give a maximum of about 10kWh produced assuming 5 hours of sunlight (in summer). Using 8kWh on average, this gives very little left to actually charge your battery, and in winter when you don't have the 5 hours it will be much worse. Your battery size is pretty ok, but you would want to put a lot more solar, or find a way to scale back your usage.

Click to expand...

This is where I get confused. In the first of my tables it says that the worst winter generated power for 1 day would be 27.45 Kw. Shouldn't that be enough to charge the battery from empty to full?

I don't trust that table: Let's assume the kW in that table are actually kWh for this. If you generate 27kWh with 2kW solar panels, that means you have 13.5 hours of peak sunlight in winter (which is also in that table). I don't think so. A quick Google told me peak sun hours in winter in Croatia is around 4 hours in January, which would mean a theoretical maximum of 8kWh generated.

djcukor said:

Thanks for your answer!

My daily consumption would be around 8 kWh (throughout the year), so I guess I'd need 24 kWh battery for 3 days of autonomy. Now, I've found a solar power calculator and this is what it calculated for 2000W of panels:
View attachment 4108
If I'm correct, I would need 5 x 100ah 48v (5120wh) Battery Kit for US $1,683.00 each and 20 x Rich Solar 100W Poly panels for US $88.99 each.
That's US $10,195.00 just for the panels and batteries.
I wouldn't be tied to the grid because that's still very expensive here in Croatia.
I tried JRC, but didn't get anything that I can understand. You see, my roof is about 30° sloped and oriented to the south. This is what I get when I punch in the numbers:
View attachment 4109
Seeing all those red bars doesn't seem right...

Click to expand...

Ok that's a good start already! I would be curious to know what the first calculator is, could you share the link? I have a hard time to understand the table it generated. "Kw" seems to be an energy unit but that's not how one would correctly write it: kW is a power unit, while kWh is an energy unit. But it seems to me quite unrealistic that a 2kWp installation would output 20 kWh on a winter day, I think the JRC tool is much closer to reality on this. A solar installation very rarely produces its rated "Watt peak" power, only under full irradiation (1000W/m2) at 25°C (lab conditions). In reality you have much less light in winter, in addition to bad weather. In summer you have a lot of light but even then the panels will heat and their output will be significantly less than the rated Wp power. But then don't hesitate to increase the power of the solar installation as suggested by @upnorthandpersonal.

Also for LiFePO4 batteries you can put the Discharge cutoff limit at 20% rather than 40%, as you can cycle them more deeply than lead acid.

If you still have big red bars in winter, which will be hard to get rid of with 8 kWh daily consumption, you may want to consider adding a second power source, like a generator (or a wind turbine, or whatever could help during a long period without enough sun). You will be able to use it then to recharge your battery on bad days, and it will help to keep your required battery storage small.

Anyway you're talking here about a pretty big setup if you want to power 8kWh daily. Maybe you'll also want to consider how you can reduce that to be able to better fit your needs in an autonomous solar setup. The cheapest electricity is the one you don't consume

Also about the PV panels you should maybe check 300W panels (24V panels), I've seen some at around the same price of the 100W panels (12V panels I guess) that you're mentioning. So even a 9 kWp PV setup should be pretty cheap compared to the battery, around 3-5 k€ I guess.

@astronom here's the link for the first calculator EcoWho.

@upnorthandpersonal, yes, it seems that table doesn't make any sense...

I have to check my numbers, I'm sure I can fit in 6 kWh a day.

I've just written a thread (there: Online tools to size (autonomous) PV setup) trying to compile the tools I came across during my research about autonomous PV systems. There may be some other tools you can use to help sizing your setup, hope this can help.