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DIY Off-Grid Solar Power

mobile-solarpower.com

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Re: DIY Off-Grid Solar Power

#71

Post by rebuilder »

Syonyk wrote: post #39
jf wrote: post #15

Earlier quoted context omitted.

Could you dig a hole for your batteries and store them below the frost line?

The problem with holes in the ground for storage of things like batteries is that... they're holes in the ground. The ground, as a general guideline, actively dislikes holes in it and strives to fill them in whatever way possible. Liquid rolling in, soil creep, debris blowing past and building up, it doesn't matter - given a long enough time, a hole in the ground won't exist anymore. You can build a hole that will ho…

I dug a hole in the ground to act as a makeshift cellar. About 1 meter cubed, dug it with a shovel, poured gravel as a floor with a French drain sunk in it, lined the walls with breezeblock, made a lid of plywood and foam insulation board. Erected a kind of tent on top to keep the rain out.

No issues so far, two years in. It’s not terribly cool in the hottest days of summer and does require a small heater if I want to keep it above freezing through winter, but in terms of being difficult or expensive to build, not at all.

Re: DIY Off-Grid Solar Power

#72

Post by londons_explore »

diamondlovesyou wrote: post #70
devwastaken wrote: post #66

Earlier quoted context omitted.

Hypothetically, for the lithium batteries, what if you made a big stainless steel vacuum wall insulated enclosure? Or just a metal box with r-60 value of foam around it? The amount of heat needing to be generated can then be calculated based on the average temp over a longer period of time, and those batteries I don't imagine have to be "warm" exactly.

What about summer? Those batteries also need to stay cool...

A $2 circulation pump and an outdoor radiator...

It's good practice to snake a water pipe around every lithium cell anyway in big packs, because otherwise one bad cell can self-heat to the point of catching fire, even while other nearby cells are cold. The flowing water means the bad cell can't get to the point of fire.

Re: DIY Off-Grid Solar Power

#73

Post by 35mm »

Syonyk wrote: post #39
jf wrote: post #15

Earlier quoted context omitted.

Could you dig a hole for your batteries and store them below the frost line?

The problem with holes in the ground for storage of things like batteries is that... they're holes in the ground. The ground, as a general guideline, actively dislikes holes in it and strives to fill them in whatever way possible. Liquid rolling in, soil creep, debris blowing past and building up, it doesn't matter - given a long enough time, a hole in the ground won't exist anymore. You can build a hole that will ho…

Agreed. It depends what you’re optimising for: $ per kWp or sq M per kWp.

Most people off grid have plenty of space but care about efficiency in terms of cost.

Re: DIY Off-Grid Solar Power

#74

Post by oldsecondhand »

adabaed wrote: post #59

This is a spanish guy who built his own off-grid setup with solar panels and 18650 batteries. As a complete ignorant in electric stuff to me this is amazing. If you know some spanish you can find here a good channel IMO! https://www.youtube.com/watch?v=u3LgbTsIO3A

Making an electric car with them:

https://www.youtube.com/watch?v=JQa5gn-7D74

He also has setups with used laptop batteries.

Re: DIY Off-Grid Solar Power

#75

Post by rklaehn »

This is a nice resource.

I am building an off grid / backup solar install for a house in rural Romania. I want it to be off grid capable, but also be able to use the grid when available.

One thing I am curious about: do the all in one systems like Growatt or MPT also provide voltage stabilization? The grid here has really bad voltage stability.

Sometimes the voltage drops down to 180V (should be 220V in Europe). Some devices like LED lightbulbs and washing machines don't like this at all.

So if these devices provide voltage stabilization, that would be great. I would then buy one and a few batteries, and later add the PV panels. It is going to be about 12kW of roof integrated PV.

Re: DIY Off-Grid Solar Power

#76

Post by rklaehn »

jandrese wrote: post #36
zoba wrote: post #8

I recently set up my own off grid solar system in a tiny cabin that I designed and had built. I used the Solar Controller+Inverter Combos recommended on this site (Growatt) but ultimately switched to ones by Renogy. The Growatt one I purchased has a wifi adapter and app - wifi requirement was a deal breaker when remote. The renogy one has a Bluetooth adapter and app, plus feels better designed (though actually I thin…

Could you insulate the batteries to reduce the heating demand? Instead of heating the entire cabin just heat the battery compartment, and only to the minimum necessary to keep them from being damaged (plus a margin for safety). Maybe even just toss them in an old discarded deep freeze? You could even have one battery in there that is disconnected from the rest of the system so it can be used to jump start the system…

An old deep freeze is probably not sufficient, but packing them into a thick layer of insulation should be fine for the winter. The insulation would have to completely enclose them though, including the bottom.

Maybe best to have them sit on a thick layer of insulation on the bottom, and a box that can be removed during the summer months so the batteries don't overheat.

Another a bit weird idea would be to somehow put them next to a compost heap, which produces low temperature heat for a long time (years) including during the winter.

Re: DIY Off-Grid Solar Power

#77

Post by cfn »

rklaehn wrote: post #75

This is a nice resource. I am building an off grid / backup solar install for a house in rural Romania. I want it to be off grid capable, but also be able to use the grid when available. One thing I am curious about: do the all in one systems like Growatt or MPT also provide voltage stabilization? The grid here has really bad voltage stability. Sometimes the voltage drops down to 180V (should be 220V in Europe). Some…

Offgrid inverters either get the power from the batteries/charge controllers or they get the power from the grid (usually to charge the batteries - they are called charger-inverters, look at the Outback VFX series for an example). This means that either you get the unstable grid power or you get the stable solar/battery power. Maybe there are inverters that somehow compensate and correct the power but I doubt it since they would be fighting the rest of the grid.

I would suggest that you add solar with a small battery bank and use the grid for overnight and for dark day charging. This way you have the best of both worlds as you only need a big battery bank if you need a lot of power when there is no sun.

P.S. Start with a 48 system since you are going for so much solar power. It is safer and cheaper in the long run.

Re: DIY Off-Grid Solar Power

#78

Post by rklaehn »

Syonyk wrote: post #44
jandrese wrote: post #36

Earlier quoted context omitted.

Could you insulate the batteries to reduce the heating demand? Instead of heating the entire cabin just heat the battery compartment, and only to the minimum necessary to keep them from being damaged (plus a margin for safety). Maybe even just toss them in an old discarded deep freeze? You could even have one battery in there that is disconnected from the rest of the system so it can be used to jump start the system…

You can insulate them to reduce heating demand, and it will help to an extent (undo that before summer to avoid cooking them), but for an unattended system, it's never going to work out very well. If the system is a year round cabin, the solution is easy enough - keep them in the heated space (which you'll have propane/kerosene/biomass heaters for), and it's not a real problem. But unattended stuff... you really just…

I agree that the difference between winter and summer is very large, like night and day.

But, 2kWh or even less should be plenty to keep a well insulated battery compartment from freezing.

On very cold and clear winter days you are going to get more than that, and on cloudy days it is usually not that cold.

Re: DIY Off-Grid Solar Power

#79

Post by Epa095 »

Syonyk wrote: post #17
zoba wrote: post #8

I recently set up my own off grid solar system in a tiny cabin that I designed and had built. I used the Solar Controller+Inverter Combos recommended on this site (Growatt) but ultimately switched to ones by Renogy. The Growatt one I purchased has a wifi adapter and app - wifi requirement was a deal breaker when remote. The renogy one has a Bluetooth adapter and app, plus feels better designed (though actually I thin…

> Still not sure how I’ll ultimately get around this. If it's portable, your option works well. For year round off grid use, there's something to be said for sealed lead acid, or flooded lead acid - they don't care about being cycled while cold (capacity is down and the voltage sags a good bit), and as long as they don't get too deeply discharged, they don't freeze. A single panel, facing south, absolutely vertical,…

Is 5kW not enough to heat the cabin? I guess it must be really cold where you are. Modern heat pumps should unproblematic handle -25°C (air to air), and provide 4-5kWh of heat for each kWh of power used.

Re: DIY Off-Grid Solar Power

#80

Post by cfn »

Syonyk wrote: post #5
mym1990 wrote: post #3

This is super awesome! I do some overlanding/longer roadtrips in backcountry but have yet to gather the courage to install a solar system. Certainly bookmarking this for future reference :D

If you're going to do solar on an RV, you really should read Handy Bob Solar too [0]. The site formatting sucks, it's very much wall-o-text, and he's absolutely right in everything he says and rants about regarding RV solar. Far too many solar installers just treat a system as the entry to people coming back for more, when the problem is that they don't know enough to adjust it properly for the stuff that was install…

Nice, someone with a non standard/officially approved opinion is a loony and is served with such epithets as "f*ck is with the antivax covid-hoax propaganda".
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