Solar power

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Bonde
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Re: Solar power

Post by Bonde »

@sky
Another factor that is kind a part of 1. is location of the panels.
Our panels are placed on our barn pointing straight south. Ideally we would also like a few panels pointing south-west to supply power for late afternoon/early evening.
The panels could also effect the value of the home negatively if you have a beautiful roof. But I would guess that panels rarely deducts more value than they add.
I would also check that there are not any local regulation against panels. I Denmark some neighborhoods have regulations for the color of the roof.

Roark
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Re: Solar power

Post by Roark »

I don't know if this has been mentioned yet, but one of the most important questions is whether you've had your roof reshingled recently. You don't want to put panels on top of a roof that needs to be redone in the next twenty years. Wait until your roof needs to be redone first, then start thinking about PV.

I am personally waiting for those solar tiles that are supposed to last 40 years. They provide the function of an even longer lasting shingle, but also produce electricity. When those come out, when it comes time to redo a roof, many people will just choose solar tiles on a financing scheme.

sky
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Re: Solar power

Post by sky »

Video discussing the extremely low cost of solar power, and the impact of a solar/wind/battery electric system. In particular, overbuilding the solar capacity creates excess capacity that can provide "free" energy on days with solar gain when batteries are full.

https://youtu.be/fsnkPLkf1ao

ZAFCorrection
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Re: Solar power

Post by ZAFCorrection »

https://www.sciencedirect.com/science/a ... 2122000478

Depending on your geography, it seems pumped storage hydro might be a good alternative to batteries. Could be the need for scale is such that at least a few houses would need to rely on it for it to be cost-effective. One could also use their system for water storage. As a hedge against systemic economic decline (Retropia assumption), two water reservoirs + pump/generator might be a more useful long-term investment than batteries. Though, it is also my recollection that in a low-tech future, lead-acid batteries should still be refurbishable.

vexed87
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Re: Solar power

Post by vexed87 »

I have a 3x100W solar array which is in part inspired by Kris De Deckers low tech magazine apartment setup. Solar PV without a task is wasteful, so you need to always make hay while the sun shines. It's not cost effective unless you put all that energy to good use. My system paired with a 1200Wh portable solar generator battery, complimented with a few standalone solar lanterns which I read by at night. It's enough to keep a laptop, a few extra LED down lights and essential medical equipment running for a few days. I bought it to insure against rolling blackouts which may be occurring across Europe this winter. It's almost certainly more carbon intensive way to power my equipment, especially when the batter is charged by mains, but paired with the panels it adds resilience to our energy consumption, and this protects our non negotiable energy use in a SHTF situation beyond short term blackouts. My wife's health and my income depend on our equipment not being interrupted, so that's a factor in the purchase decision. Yes, the outlay is significant, but the peace of mind is priceless. Relative to the cost of a standard American household energy use, this system is tiny and costs pocket money. It amortises to around £80/year, about 60% of one month's winter energy use at home. Clearly there's a lot of waste here at home.

Disconnecting from the grid and using very little energy forces me to evaluate wasteful energy habits. When I'm not charging the solar generator, I can have the panels heat water or charge my ebike. It's been a fun experiment, so far I haven't needed to rely on the system, but it's there waiting when I need it, which technically makes it very environmentally unfriendly, as I'm not using it to capacity. I'm working though ideas on how I can utilize it in my daily routine, without risking it being empty when we need it most, but until the blackouts start, it's hard to put anything into practice.

This system isn't big enough to provide thermal comfort or cooking, for that I use biomass. I have built a methanol heater which doubles as a stove, and have 2m3 of firewood on hand to cook with in a cob oven or Kelly kettle. I can use all of these to warm hot water bottles in the event central heating stops functioning.

This was the inspiration for the methanol heater. Methanol can be bought from industrial sources, but it's also possible to obtain from wood gasification. I plan to give that a go some day. https://youtu.be/pl0GOc2gLl0

jacob
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Re: Solar power

Post by jacob »

vexed87 wrote:
Tue Nov 08, 2022 6:03 pm
This system isn't big enough to provide thermal comfort ...
I'm kinda wondering if that is actually the case. Consider https://www.homedepot.com/b/Workwear-He ... 5yc1vZcerj and the likes ... and that you're already running on 12V. LowTechMag had an article on this too.

AxelHeyst
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Re: Solar power

Post by AxelHeyst »

300W x 6 hours of sun * 0.71 factor (fixed panel angle set to latitude) = 1278 Wh harvestable on a winter day. Oh nice, that's what the battery size is. Lithium or AGM though? So either 600Wh or 960Wh available on a full charge.

let's say you only need electrically generated heat for four hours, two hours at night and two in the morning. You can run it at 150w (AGM) or 240W (lithium) for those four hours. Hm, I can't see on first glance what the wattage of those heated jackets are, but I bet just intuitively you could stay toasty with 150w on the inside of your insulation layers. Probably overkill.

That jacket says their 3AH lithium battery lasts 12 hours at low setting. Assuming it is 12v, 3Ah is 36 Wh. Running twelve hours that's 3 watts if they run it all the way down, if they limit it to 20% discharge then thats 36Wh*0.8= 28.8Wh, for three (edit: I mean twelve) hours that's 2.4watts.

Nahh, 3 watts is way too low to stay warm, right? Seems low to me. Maybe that's why it's the low setting. I goof up my math somewhere?

If that is close to right, 150w for four hours is plenty for one or two nerds to stay warm in a cold apartment. :lol:

edit: halfway to DIY is heating pads like this, that you can just plug in to USB and stuff under jackets you have. Further down the rabbit hole is heat tape, I lost the link to that, involves getting a controller and some other stuff.
Last edited by AxelHeyst on Wed Nov 09, 2022 6:53 pm, edited 3 times in total.

Slevin
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Re: Solar power

Post by Slevin »

AxelHeyst wrote:
Wed Nov 09, 2022 5:54 pm
That jacket says their 3AH lithium battery lasts 12 hours at low setting. Assuming it is 12v, 3Ah is 36 Wh. Running twelve hours that's 3 watts if they run it all the way down, if they limit it to 20% discharge then thats 36Wh*0.8= 28.8Wh, for three hours that's 2.4watts.

Nahh, 3 watts is way too low to stay warm, right? Seems low to me. Maybe that's why it's the low setting. I goof up my math somewhere?

If that is close to right, 150w for four hours is plenty for one or two nerds to stay warm in a cold apartment. :lol:
Erm I think you calculated the per hour, not for a three hour segment.
If I'm following your math, we assume we discharge 28.8 Wh, so per hour for 12 hours that's 28.8/12 = 2.4. So its 2.4 watts per hour, which still seems very low. 7.2 watts for 3 hours. Still ridiculously tiny

AxelHeyst
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Re: Solar power

Post by AxelHeyst »

Slevin wrote:
Wed Nov 09, 2022 6:26 pm
Erm I think you calculated the per hour, not for a three hour segment.
If I'm following your math, we assume we discharge 28.8 Wh, so per hour for 12 hours that's 28.8/12 = 2.4. So its 2.4 watts per hour, which still seems very low. 7.2 watts for 3 hours. Still ridiculously tiny
(I had said three hours originally but I meant to say 12 hours).

28.8Wh / 12 hours is 2.4 watts, not 2.4 watts per hour. I don't know what watts per hour means, as that breaks down to Joule per second per hour :| . That would imply... acceleration? An acceleration in the flow of energy? Nah, that's not what's happening here.

28.8Wh means there's enough juice to run 28.8 watts for an hour, or 2.4 watts for twelve hours.

*(For added fun we can contrast how the unit Wh (watts*hours) is written with how the unit Btuh is written, which actually means btu's / hour, as in hour is in the denominator. But that makes sense, because one btu is 1055 Joules, so a btuh (btu/hr) is units of joules/time, which is the same kind of unit as watt, J/s. Which is why in the US you can find air conditioner unit capacities given in btuhs, tons (a ton is 12,000btuhs), or watts).

Slevin
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Re: Solar power

Post by Slevin »

@AxelHeyst right. Makes sense, I haven’t done enough electronics in a hot minute apparently!

vexed87
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Re: Solar power

Post by vexed87 »

jacob wrote:
Wed Nov 09, 2022 9:19 am
I'm kinda wondering if that is actually the case.
That's a fair point Jacob, I was thinking more along the lines of it being unable to support conventional space heating in a 100m2 home. But there is certainly some scope for heating the person, in fact before investigating the Kelly kettle and hot water bottle combo, I was thinking of getting a low wattage travel kettle so not to trip the inverter. Err yes it's not just a DC system, it does both, but I mostly use the DC to avoid conversion losses, AC has 1500w surge limit)

The problem, here at least, heat demand is greatest when the sun offers least power, so I wanted to decouple my thermal comfort from my electric supply so I didn't need to oversize the PV or batteries. That way I preserve capacity for gadgetry with no other generation source, I'll run the numbers and if I can keep 3 bodies warm on what capacity I have left, I might yet shoe horn it in.

I've looked into heated gilets previously, but held off mashing the buy button as I only found products made by no name Chinese vendors, many reviews on Amazon leave complaints on build quality. Maybe I need to visit some reputable merchants. Since these are not mainstream products, there doesn't seem to be a wide range of choice, that said most of the complaints seem to be of loose wiring, which should be easy to isolate and fix.

AxelHeyst
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Re: Solar power

Post by AxelHeyst »

Well you inspired me vexed, I found some stuff that looks like it'll work and I ordered it. 12v 7w heating strips marketed at medical device makers (4 for $16), size 1"x2", and a couple temp controllers (two for 8$) because these things are specced to hit 150C to 200C. Decent reviews.

Will report back once I've got it going. My studio is currently 32F/0C or thereabouts in the morning so will be a good test case.
Last edited by AxelHeyst on Fri Nov 11, 2022 7:28 pm, edited 1 time in total.

rube
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Re: Solar power

Post by rube »

I gave approval to the quotation to install a 4350 Wp system on one of our rentals. Since it part of an HOA (and much higher roof than an ordinary house) it was more complicated. Hopefully the installation early next year will go smoothly.

I'll try to use the experience of this rental to also arrange installations at the other rentals (all HOA).
Last edited by rube on Thu Nov 10, 2022 10:03 pm, edited 1 time in total.

steelerfan
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Re: Solar power

Post by steelerfan »

I have panels. Truthfully I would have to do a deep dive analysis on whether solar panels are really worth it. I would note I also have had EVs for the last 7 years at this point. My system is grid tied with no battery backup. I bought the system last year (8500 kw) thru SunRun. I went with SunRun because they are established and had a warranty that guaranteed production levels. The cost after the tax credit was a little under 27K. My system generates more electricity than I consume even after charging the car. Miles driven is pretty low though. My consumption meter shows a net credit after a year and a half. Primarily I made the decision to buy to reduce my carbon footprint and lock in my electricity costs as the rates increases will be irrelevant. Concerned that in the future the power company could do something to no longer make it feasible. In that event I would consider installing a power bank and put some of the house in a closed loop if possible. But again the decision was somewhat philosophical.

Would estimate payback will be about 12 years but who knows. It really depends on how rates develop. Currently my electricity usage is around $2500K per year and assume this will increase over time. Lots of variables such as my son moving out this weekend. His gaming rig sucks power LOL. He also works from home as do my wife and I.

As far as the battery fire risk that seems to be a concern. I have a bolt which had a massive recall for fires and I am due to receive a new replacement battery free of charge in the future. I will push that out as long as possible as perhaps the ranger will improve over time. FWIW my brother in laws jeep caught on fire as well - so there haha.

vexed87
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Re: Solar power

Post by vexed87 »

@AxelHyest, please report back! I can't take any credit though! 😅

WFJ
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Re: Solar power

Post by WFJ »

OP,

Do a cash flow analysis, but as you will find, the variables that you will be extrapolating are impossible to estimate. Any estimate will likely give contradictory answers (unless you live in a sunny place with high energy costs, the house I grew up in had solar panels that heated our water supply in the late 70's or early 80's).

Simple variables to predict are; cost/source of your homes external power today and every year in the future, your energy use today and every year in the future, power yield of current solar panels today and yield of solar panels every year in the future, potential revenue for selling excess energy today and every year in the future, environmental costs to produce a solar panel today and every year in the future, how many years you will live at current residence, and of course the pesky cost of capital today and every year in the future, just to get started and provide a rudimentary estimate.

AxelHeyst
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Re: Solar power

Post by AxelHeyst »

vexed87 wrote:
Fri Nov 11, 2022 12:00 pm
@AxelHyest, please report back! I can't take any credit though! 😅
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