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#75 Reply
Posted by
Seekonk
on 21 Jan, 2019 15:24
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Sometimes I wonder if the monitoring systems don't draw more than what is generated. We just had an ice storm and the weather was still in the teens. Surprised at how much was being generated and the ice melted in about 2 hours. If sun can't melt the ice there isn't much to be gained.
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Lol yeah if I go ahead with the Arduino and RPI I do wonder too if it would end up using more power than it produces just for the sake of monitoring itself. The nice part though would be adding the logic to turn the inverter on/off automaticly. Right now it's just off period.
Either way if I do plan to run any load on this I will need to do the ice melt system and add more batteries (to power the ice melt system).
We've had a couple days of solid sun now but because of the snow/ice crust it's simply not producing enough to generate any significant heat at the cells on it's own. It's been around -30 or so which does not help but that's the only time we get sun. Once it gets warmer than say, -20 then it's overcast and probably snowing.
The days are starting to get longer too, there was sun till around 5:30 today.
I think moral of the story is really the easiest way to go for an off grid setup would probably be to have vertical solar panels. I think what I would do is setup 3 arrays, east/west ones that are vertical, and then a south one that is not. Up until the point we get the first freezing rain of the year all 3 would produce. After that only the two vertical ones would produce. I would want to size everything so the 2 arrays can run everything needed. In the summer months I would have tons of excess power which means I could just run A/C all day. Could do a convoluted setup with liquid glycol heated by a wood boiler but probably more complicated than simply having a vertical array.
Would probably also want to automate the snow removal but really if I was to do a ground mount system it would not be a huge deal to do it manually every morning. By the time I actually want to live in an off grid situation it will probably mean I don't have to work, so not like I'd be rushing to get somewhere.
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#77 Reply
Posted by
Berni
on 22 Jan, 2019 06:27
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Yeah a RPi will eat way too much power for monitoring. But a properly designed microcontroller solution can use a few miliwatts of power(Or even 10s of microwatts average). The power hungry part is any sort of long range radio link.
I guess where you live its simply too cold for the sun to do anything to the ice. It tends to get down to -15°C here on a normal winter and i find even that pretty damn cold, everything is frozen solid.
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Yeah the RPI would be so I can get network connectivity to the arduino, ex: web page showing info etc. Probably setup a web cam so I can look at the panels remotely too. Not sure if arduino is fast enough to do ethernet directly.
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#79 Reply
Posted by
Berni
on 22 Jan, 2019 17:04
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If nothing else there are the old SPI to Ethernet chips that let any MCU talk to the world. As for direct Ethernet i been using a STM32F MCU with built in Ethernet RMII interface and could get simultaneous saturated 100Mbit in and 100Mbit back out traffic without the MCU working up a sweat.
But Ethernet by itself is not very power efficient as any piece of networking equipment (Even just a switch) to provide a working LAN will use about as much power as a RPi.
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#80 Reply
Posted by
apis
on 22 Jan, 2019 18:30
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Would probably also want to automate the snow removal but really if I was to do a ground mount system it would not be a huge deal to do it manually every morning. By the time I actually want to live in an off grid situation it will probably mean I don't have to work, so not like I'd be rushing to get somewhere.
If you have a ground mount system couldn't you mount it so you can adjust the angle. It could be between only two states even; vertical for winter and some lower angle for summer? You would only have to adjust the angle twice per year.
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Would probably also want to automate the snow removal but really if I was to do a ground mount system it would not be a huge deal to do it manually every morning. By the time I actually want to live in an off grid situation it will probably mean I don't have to work, so not like I'd be rushing to get somewhere.
If you have a ground mount system couldn't you mount it so you can adjust the angle. It could be between only two states even; vertical for winter and some lower angle for summer? You would only have to adjust the angle twice per year.
Yeah definitely an option too. A full tracking system would be pretty neat too. Probably start with a static system as I'd only be using the property in summer at first, then can grow from there and keep adding modules and getting more complex with moving parts etc. The strong winds we sometimes get here add some complexity as any mechanical parts need to be strong enough to handle it.
I kinda have something figured out in my head too, east/west vertical arrays that are mounted right on the wall of a building, this building would house all the power stuff and have overhangs that protect the panels from freezing rain (unless it's driving... but at least it would only get one side). Then an inclined south one against the south wall of said building. Everything all tied in together built for strength.
Actually that's another thing too on an off grid property I'd have room for a wind turbine, so probably build one of those too for excess power in winter.
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#82 Reply
Posted by
Berni
on 23 Jan, 2019 06:23
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Yeah being at such a high latitude in Canada probably makes near vertical arrays a good idea.
Over here its actually more efficient to have a panel laying completely horizontal when compared to completely vertical. Especially since the sun in summer is high in the sky and that's when you produce the most (Tho its only a good point if you give power back to the grid as you will likely be overproducing in summer)
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#83 Reply
Posted by
cologneled
on 23 Jan, 2019 10:50
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it was electrodacuas thread about pv cheaper than natural gas, he actually says its 60 degrees in the text, here is the pic,
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#84 Reply
Posted by
apis
on 23 Jan, 2019 22:02
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Vertical is not so bad in the north during winter when there is snow because the snow cover reflects a fair amount of sunlight into the solar panels. Without the snow its better to have it at some angle, the optimum angle depends on latitude.
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If the panel is about 0.5 m2, a 1 mm ice sheet would be about 0.0005 m3 which is ~0.46 kg of ice.
Latent heat of fusion for water is 334 kJ/kg, so it would require about 153 kJ to melt it.
The heat capacity for ice is about 2.05 kJ/(kg*K) so you need about 940 J per degree C.
So if it's -10 degree when you start you need about 163 kJ to melt it. At 1 kW that takes 163 seconds or a little less than 3 minutes assuming perfect heat transfer. In reality you'll loose a lot of heat to the rest of the system, so you can probably expect 10 min or more at 1 kW per panel.
You wont have to melt it all.
Just a thin layer of water between the solar panel and the rest of the ice is enough, especially if combined with some mechanical force maybe a broom or compressed air into the boundary layer.
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Yeah I imagine if I could get a thin layer of water to form then the rest could slide off, either with help or on it's own. Though still going to take a decent amount of energy to do that, as that thin layer is going to be cooled off by the ice on top so need enough heat for the water to stay as water and not just cycle back into ice. I kind of gave up for now though, went up there a couple times trying to scrape some of it off, but it's a really hard crusty/icy snow, it's not even a solid sheet of ice it's just all messed up.
Sometimes we get some warm days in March and April, so I think I'll just wait till then and then try to chip away at it again on a warm day. I may experiment with the nichrome wire idea though. I should probably try to get on that soon using a piece of cardboard or thin plywood as a test medium as a proof of concept. Then I can pour water on it and throw snow on it and cycle that a few times and try to form a crust like on the panels, then see if I can melt it from below while measuring the amount of energy I'm using. That would determine the size of battery I would need if I want to do this without using grid power.
Probably end up just giving up on the idea though, basically I have to ask myself how much effort and money I want to put into a shed's power system. Though if I did get this going where I can run stuff off it year round it would act as good backup power. With a bigger inverter I could even run my furnace for a bit, if we get a big blackout. Or at very least charge up flash light batteries, phone etc, and keep the wifi going.
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#87 Reply
Posted by
apis
on 04 Feb, 2019 19:31
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If the panel is about 0.5 m2, a 1 mm ice sheet would be about 0.0005 m3 which is ~0.46 kg of ice.
Latent heat of fusion for water is 334 kJ/kg, so it would require about 153 kJ to melt it.
The heat capacity for ice is about 2.05 kJ/(kg*K) so you need about 940 J per degree C.
So if it's -10 degree when you start you need about 163 kJ to melt it. At 1 kW that takes 163 seconds or a little less than 3 minutes assuming perfect heat transfer. In reality you'll loose a lot of heat to the rest of the system, so you can probably expect 10 min or more at 1 kW per panel.
You wont have to melt it all.
Just a thin layer of water between the solar panel and the rest of the ice is enough, especially if combined with some mechanical force maybe a broom or compressed air into the boundary layer.
That is why I made the calculation for only a thin (1mm thick) sheet of ice. Water has a huge latent heat of fusion as well as a large heat capacity so it takes a lot of energy to melt.
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Been trying to stay on top of clearing the snow as best as I can, the layer of crusty snow remains but they still produce enough to trickle charge the battery. Beats trying to carry the battery to the house while on snow shoes.
Today was a very warm day, and some of it has actually started to melt. I have maybe about 30% panel exposure on all 4 modules now.
Went on the house roof to shovel some snow off, and came to the conclusion that solar on my house is just not realistic though. Just too much snow to deal with. Going to wait till I eventually buy an off grid property, then I can do a proper ground mount system that is vertical or at least tilted very steep.
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#89 Reply
Posted by
Berni
on 21 Feb, 2019 06:08
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Yeah your location is probably not the best for solar in general since when the panels do work they don't get a lot of sunlight per day.
Got nicely warmed up here in the past weeks, been outside in a T shirt.
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How about trying a hammer and taping in the ice to break it?
I would not try the chemical as they will cause corrosion especially to connection joints for the wires.
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Kinda sketchy going up there or trying to use a ladder at this point. Would not want to use any kind of brute force though to risk damaging the panels.
This is how they looked like last time I went there. We got another 20-30cm of snow since though with another 40cm or so on the way and have not had a chance to go back out there.
If curious this is what the side of the house looks like after I shovelled part of the roof:
They are announcing freezing rain now so back to square one after that.
But yeah if I want to live off grid I'll want to have them on a ground mount system and have them tilted mostly vertical. Though with a big enough property I'd also have room for a wind turbine and I'd probably want a backup generator to top up batteries.
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Where's your house? All I see is snow. Where I live we just visit the snow, we don't live in it.
I do see your issue. And I suppose you have a layer of ice on the panels.
For someone who does not live in the snow, can I ask some dumb questions?
You shoveled the snow off the panels, correct? And there's a layer of ice covering the panels?
If you did nothing, when would things thaw?
Does the black color of the panels cause the snow/ice on the panels to melt faster than the rest of the roof?
It would take a heck of a lot of energy to melt the snow with a resistive heating element.
Do you think applying RainX before the next freezing rain storm would repel the water so it would not "stick" to the panels?
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#93 Reply
Posted by
ahbushnell
on 23 Feb, 2019 15:15
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Freezing rain will cause lots of problems with wind turbines also. The biggest one is that except in that unicorn incident where the rain freezes identically on all blades of the prop/turbine the balance will be shot and there is real danger of the machine tearing itself apart if it isn't shut down.
Your climate makes it very tough. Fortunately there is a lot of the world that doesn't have to deal with that. Even cold places. Where I grew up averaged five feet of snow a year, but only had freezing rain once a decade or so. A little broom work would deal with the problems. Where I am now gets regular freezing rain, but also regular warm ups so there are only a couple of days a year where ice accumulates. Maybe the simple solution is a move to someplace easier. I know that you don't have to leave Canada to improve on what you describe.
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#95 Reply
Posted by
Berni
on 24 Feb, 2019 09:25
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Freezing rain can cause quite a havoc here in central Europe too.
A few years ago there was a case of freezing temperatures flowed by a big rain storm. This caused a good 1cm of ice to build up on anything, cars, signs, trees, overhead cables etc. Usually its just a annoyance ot having to scrape and defrost your car for a good half hour before you can drive to work. But this much ice becomes so heavy that trees start falling one after the other, offten falling across roads and cutting off the more remote areas from the world when it all happens at once. Some trees fall onto overhead electrical lines, in some cases enough ice builds up on the wires themselves to make them snap or break the insulators, this even brought down one or two big 400kV lines with quite a spectacle associated with it. Some places ware left without power for days or even weeks, whole country was in chaos outside of any major cities.
Luckily my area was not hit too bad, we lost power for half a day a few times and you had to watch out when driving on roads that go trough forests, but that's about it. We kept the house warm with a fireplace in the living room, but we still had water and cellphone reception all the time. Its a very rare thing, people don't even recall this ever happening here before.
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Where's your house? All I see is snow. Where I live we just visit the snow, we don't live in it.
I do see your issue. And I suppose you have a layer of ice on the panels.
For someone who does not live in the snow, can I ask some dumb questions?
You shoveled the snow off the panels, correct? And there's a layer of ice covering the panels?
If you did nothing, when would things thaw?
Does the black color of the panels cause the snow/ice on the panels to melt faster than the rest of the roof?
It would take a heck of a lot of energy to melt the snow with a resistive heating element.
Do you think applying RainX before the next freezing rain storm would repel the water so it would not "stick" to the panels?
I have a broom with a long pole so I take the snow off every couple days, basically whenever I get around to it. I bought snow shoes so I just snow shoe to the back yard, saves me from having to shovel a path. At the start of the season I was shovelling a path then gave up on that idea. We don't get freezing rain here that often, they get it more down south in like Toronto area, but when we get it, that ice is there for the season. Worse is when it's a mixture of rain and snow, it creates a sort of crust. Happens to the car too. Pretty much have to let it run for an hour or so to get rid of that, as nothing else will get it off.
If I did nothing at all, like never cleared the snow period I pretty much have to wait till April-May before I'd see the panels again. If I was to use resistive heat it would mostly be just to help get rid of the crusty layer, as yeah there is no way I could melt a full blown snow fall. Though on warmer days, I have found that the panels can help melt the snow a tad. We don't really get much warm days though. I'm thinking if I automated the removal or at very least had something I can trigger manually by looking at a web cam, I would maybe have slightly better luck too, as I'd be able to stay on top of it more. Depending on my work shifts I'm not always going back there.
I'm reluctant to apply any kind of chemicals as others mentioned some may react weirdly with the aluminium, or maybe even the adhesives used.
Never considered how wind turbines would be affected by freezing rain too but yeah I guess it makes sense. Would mess up all the mechanical parts. Though if I was building a wind turbine I could try to take that into account as well with my design. Though really if I get a big enough property I can just do the original idea of having more solar panels and having them vertical. Where I am now I just don't have enough room without shadows to do much, the shed ones are the best I can really do. Even those arn't optimal as they face west.
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#97 Reply
Posted by
george80
on 24 Feb, 2019 11:04
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I always thought hell had more fire and a redish colour to it, but there you go. It's white and cold beyond belief and no doubt has endless problems with just everyday living. Must be where the REALLY bad people are sent!
I'm going to be a good boy so I don't have to go near any place like that hell on earth!!
I'll bet people that live in that white hell go out and burn old tyres at night to try and Hurry GloBull warming along as fast as they can to save them from that torture.
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Haha the nice thing is there's less people here so it's less crowded and real estate is not through the roof. (though snow might go through the roof lol). Also beats the +30C's that some places get. You can dress for cold but can't do much for extreme heat.
This is a tad on the extreme side as we have not had this much snow in at least 10 years though.
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#99 Reply
Posted by
george80
on 24 Feb, 2019 12:20
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Haha the nice thing is there's less people here so it's less crowded and real estate is not through the roof. (though snow might go through the roof lol). Also beats the +30C's that some places get. You can dress for cold but can't do much for extreme heat.
Well you got me on all those points... except 1.
The plus 30's we had here just a few weeks ago were actually 47's. That's C not F.
Now that is hell.
Untill this last week, hasn't been under 30 here, even the few days it did rain, for 3 months.
Predicted 26 Tomorrow then back to 33 min for the next 6 days.
Wish to heck we could get some decent rain though. Haven't had anything bar dew ( which was weird this time of year) since early November.
This is a tad on the extreme side as we have not had this much snow in at least 10 years though.
Thats Globull warming at work!!
