Good afternoon ,I’m new here so will say welcome to all . I have in total 6kw of grid tied panels and a 6kw wind turbine. Due to me been having maxed out what I can send back to the grid I’m looking at off grid . I have a small farm and use about 40 kw a day max use which is summertime for me . I’m looking to put a further 16 kw of panels on the roof with 2 8kw inverters and here the bit that I don’t fully understand a 50-60 kw battery storage ( 48v 2 volt cells forklift type ones) now my questions are this 1 - how much of the 16kw from the panels could I put into the batteries is there a formula , I wouldn’t want to find out I could only charge at 8 kw say . Question 2 how much power could I take out the batteries? i used maybe 4kw output maximum usage. I mainly run freezers hence why I use more power in summer . So if you could help me on what is the best gear to use . And charge rates of batteries and how to work them out I would be most grateful
Setting up an off grid pv array
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your grid connection maybe maxxed out, but that doesn't stop you installing gear that can be set to zero export that is still grid tied.
Trying to go completely off grid is a bit of a minefield, especially if you have critical gear like freezers to power. The last couple of winters have had long spells of overcast weather without much wind either. Batteries are great, but expensive. If your main use of energy is in the summer, then that coincides with long days and highest outputs from your systems, so you have to question what the batteries will do for you. However, it sounds like you have a couple hanging around, so fill your boots! As for what you can get out of a battery, that is controlled by the inverter, and 4kW is not an issue in that regard. If you install hybrid 8Kw inverters, you could connect batteries to those. You could also use the AC output on the inverter as a Universal Power Supply in the event of a power cut to keep the freezers working. Have a read of some of the battery posts on here, there's a lot of info that should be interesting to you.
Trying to go completely off grid is a bit of a minefield, especially if you have critical gear like freezers to power. The last couple of winters have had long spells of overcast weather without much wind either. Batteries are great, but expensive. If your main use of energy is in the summer, then that coincides with long days and highest outputs from your systems, so you have to question what the batteries will do for you. However, it sounds like you have a couple hanging around, so fill your boots! As for what you can get out of a battery, that is controlled by the inverter, and 4kW is not an issue in that regard. If you install hybrid 8Kw inverters, you could connect batteries to those. You could also use the AC output on the inverter as a Universal Power Supply in the event of a power cut to keep the freezers working. Have a read of some of the battery posts on here, there's a lot of info that should be interesting to you.
Hi Binky
thank you for replying . I don’t have any gear yet but trying to put or get supplied a system that would work for me , The reason for batteries is mainly the freezers in summer when the sun goes down yet its still warm outside . I don’t want to make the mistake of say putting up 16kw of panels if they couldn’t charge the batteries in the day ready for night use .
i have 2 consumer units on the farm one for inside and one for outside and was hoping to connect the outside consumer unit to the battery outfit
A 4kw system with reasonable pitch and facing South can generate around 25 - 30 kw a day in the summer, so scale that up for your array and you should be fine. Ideally you would have the freezers running during daylight hours to reduce pull on the batteries, and your wind turbine will certainly help matters.
Yes my main concern was if I fitted 16kw of panels and two hybrid 8kw inverters then say in the middle of summer on a good day I’d be doing
12-14kw an hour now at my peak usage the farm would be using 4-6kwh
that would be used directly from the panels in the day , now would the 6-8 kw that was surplus be going into the batteries ? I would be hoping to have a 50 -60 kw storage in batteries . Or will the batteries only take so much .? I mean as in charge rate can you put the surplus 6-8 kw into the batteries per hour
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if you have a 'spare' 6-8kWh to feed into the batteries, then you afe looking at say 4kWh charge rate per inverter, which would take about 8 hours to fully charge the battery at 50-60kW. I would think that is a perfectly plausible scenario in the long summer days. Bearing in mind a forklift is usually charged overnight, although I'm not sure how long they really take. I'm not familiar with lead acid type batteries, but 6-8kw inverters seem to be able to output over 100Amp at 48V as a charge rates, sometimes a bit more which is roughly 5kw. You need to read up on the batteries you want and inverter. You may also strugge to get a single phase 8kW inverter, although I see Sunsynk make one. Most single phase units stop at around 6kW.
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