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DIY Off-Grid Solar Power

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Re: DIY Off-Grid Solar Power

#91

Post by Symmetry »

i_am_proteus wrote: post #89
Syonyk wrote: post #17

Earlier quoted context omitted.

> 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,…

Yep. Unless you've got running water or a high cliffside for wind, the best off-the-grid heat source for cold climates is an acre of woods and an axe. Insulation, too. A lot of sheds and cabins (and single-family homes) could do with more. Saves on cooling bills in the summer, too.

An acre of trees should be enough to give you an average of 4 kW of thermal power year round, way more than you probably need. Though at 1 W/m^2 how much industry an area of trees could support was the binding constraint on industry for a lot of recorded history. Especially there was always pressure to turn forests into farmland.

Re: DIY Off-Grid Solar Power

#92

Post by i_am_proteus »

Symmetry wrote: post #91
i_am_proteus wrote: post #89

Earlier quoted context omitted.

Yep. Unless you've got running water or a high cliffside for wind, the best off-the-grid heat source for cold climates is an acre of woods and an axe. Insulation, too. A lot of sheds and cabins (and single-family homes) could do with more. Saves on cooling bills in the summer, too.

An acre of trees should be enough to give you an average of 4 kW of thermal power year round, way more than you probably need. Though at 1 W/m^2 how much industry an area of trees could support was the binding constraint on industry for a lot of recorded history. Especially there was always pressure to turn forests into farmland.

Could get by on much less than an acre if it were managed, but better to have more land and be able to keep it as unmanaged forest. That'll also produce fresh game and give some buffer on the lumber supply for lean years. How much rain falls is strictly out of my hands.

Re: DIY Off-Grid Solar Power

#93

Post by Epa095 »

CorrectHorseBat wrote: post #84
Epa095 wrote: post #79

Earlier quoted context omitted.

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.

5kW of panels don't produce 5kW in winter, that's the issue I guess.

What does the 5kWh of energy turn in to, of not heat?

Re: DIY Off-Grid Solar Power

#94

Post by jacquesm »

CorrectHorseBat wrote: post #84
Epa095 wrote: post #79

Earlier quoted context omitted.

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.

5kW of panels don't produce 5kW in winter, that's the issue I guess.

Correct, they will produce more.

Solar panels produce the most power on cold winter days. The 'rated power' is for 20 degrees ambient at full (90 degrees, no cloud) incidence at sea level.

Re: DIY Off-Grid Solar Power

#95

Post by jacquesm »

jf wrote: post #15
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 dig a hole for your batteries and store them below the frost line?

What I did in Canada was to dig a bunker into the side of a hill near the house. That solved both the frost and any fluid issues in one go. It was a bit of work though to get that all done.

Re: DIY Off-Grid Solar Power

#96

Post by jacquesm »

madaxe_again wrote: post #62
Syonyk wrote: post #28

Earlier quoted context omitted.

Have you priced LTO? They're rather staggeringly expensive for their capacity. The cycle life is excellent, but they excel in very high C-rate applications (10C-20C), which is the opposite of what you need for off-grid systems. If an off grid system is getting anywhere near C/10 discharge rates, you're going to be in the dark awfully soon. It's old tech, it's boring, but it works fine... flooded lead acid. Don't full…

Yeah, lead wins hands down. This is a few years out of date now, but when speccing out my system I did a bit of analysis of battery types. We went with OPzS, and so far, so good. https://docs.google.com/spreadsheets/d/1w8vPBHkMyY5jvkxtK1Qh...

Recycled Lithium Ion is much cheaper still, but more risky (and less maintenance). You'll have to do some pretty fanatic inbound QA to determine whether all your cells are safe to use. but if you do that and fuse your cells individually you should be able to make that work.

Re: DIY Off-Grid Solar Power

#97

Post by jacquesm »

ctime wrote: post #2

Will Prose seems like a really great person. If you’re interested in what you see on this site, check out his YouTube channel: https://youtube.com/c/WillProwse

I have seen enough of his videos to know that he can be spectacularly wrong (dangerously so) about some of his stuff and if you are not already very knowledgeable about this then you may well end up following some very bad advice.

This guy has far more practical experience and seems to be less error prone, and also does not shy away from showing when he gets it wrong, which is often far more valuable than a polished and edited video:

https://www.youtube.com/channel/UC0pBauLp63yzf6sVdEOIUbA

If you want to learn about DIY off grid power from youtube I'd start here.

Re: DIY Off-Grid Solar Power

#98

Post by [deleted] »

Epa095 wrote: post #79
Syonyk wrote: post #17

Earlier quoted context omitted.

> 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.

[deleted]

Re: DIY Off-Grid Solar Power

#99

Post by jacquesm »

DyslexicAtheist wrote: post #87
Syonyk wrote: post #7

Earlier quoted context omitted.

The problem with him, and people like him on YouTube, is that about 90% of what they say is fine, and 10% ranges from "iffy" to "This is a good way to burn your house down - at some unknown point in the future." The average viewer of that sort of material can't tell the difference, and by the time you can, you're not in need of handwaving entry level information, because you can read the design documents, spec sheets…

sounds a bit gate-keepy to me. People tell me that I shouldn't repair my own car for similar reasons. Instead I should go to the OEM and have it serviced there for 1000,- a pop. This assures I'm getting genuine OEM branded parts with a 800% profit margin while also reducing the time spent on diagnosing the issue because now whole modules get replaced since cost of human labor is expensive. If I would heed that advise…

He has a point, but there is a thing you can do to offset some of this: read all of the comments. Plenty of times there will be someone in the comments pointing out what's wrong in the videos.

The problem with Lithium Ion installations of any size is that the batteries are inherently dangerous and mistakes can easily set you back more than you saved on the whole thing. Unlike say your car where as long as you stay away from suspension, brakes and steering the worst that could happen is that you end up stranded by the road side.

Another issue is that when it goes wrong with Lithium Ion it can go wrong fast and it isn't easy, or sometimes even possible, to stop a thermal runaway once it gets going, especially with densely packed cells, besides the fact that you likely won't be watching your batteries 24x7.

There are some people on youtube that advocate for extremely unsafe practices (Jehu Garcia, for instance) and that have a huge following, so Will Prowse is certainly not the worst that you could run into there. It would also be good if he indicated more clearly what his sponsorship relations are and how that relates to the advice that he is giving, quite a few of his videos feel like thinly disguised ads.

Re: DIY Off-Grid Solar Power

#100

Post by jacquesm »

Syonyk wrote: post #30
kyleee wrote: post #19

Earlier quoted context omitted.

"YouTube is simply the wrong medium to try to teach detailed" YouTube is literally just humans talking, so you are basically saying you don't think humans can teach complicated subjects?

That's an absolutely absurd characterization of both YouTube and actual teaching. YouTube is dominantly entertainment/personality based "edutainment" at best, based on what seems to percolate to the top and be promoted. There's zero feedback outside comments (standard warnings about comment sections apply here). The right way to teach complex subjects is a more interactive process with hands on material/learning/actu…

This is true, but there are definitely positive exceptions to this rule.
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