Author Topic: Solar frickin' wall of block of flats  (Read 3590 times)

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Offline Nauris

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Re: Solar frickin' wall of block of flats
« Reply #25 on: August 09, 2019, 06:40:24 pm »
If you live at a higher latitude it may be more efficient to mount the panels vertically versus horizontally.
It is at 48°, about where the USA Canada border is.

Why wouldn't the pivot point be at 45° latitude? What am I overlooking -- the increasing athmospheric scatter/absorption at low angles?

If you don't consider snow covering panels that pivot point is from pvgis data about 50...53° in Canada and about 60° in Scandinavia. Difference is due to different average cloudiness during different times of year.
« Last Edit: August 09, 2019, 06:47:05 pm by Nauris »
 
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Offline Red Squirrel

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Re: Solar frickin' wall of block of flats
« Reply #26 on: August 10, 2019, 01:43:34 am »
Honestly this is actually kind of smart. The snow/freezing rain won't stick to them, and you get less surface area on the roof for such a building so may as well make use of the walls.   

If I had a big property with enough room for a real solar setup I would put all my panels vertical tbh.  Do east, south, and west facing arrays.  Maybe tilt the south one slightly.  Either way for a good part of the year the ground is covered in snow and the reflection off it from the sun will actually go to the panels. Not sure how much that really helps but it's something. 

I have a 400w array on my shed but they are a lot of work to keep clear, and the first freezing rain of the year puts them out of commission till mid April when it gets hot enough for it to melt on it's own.  The ice is not clear, it turns into a snowy/icy cake and you can't get that crap off.  Even on the car it's hard to take off and you really have to scrape down hard, but don't want to be doing that on solar panels.

I want to experiment with nichrome wire or something to see if whatever energy I have stored in the batteries would be enough to clear at least two of the panels when we do get freezing rain, then at least in winter I would have SOME capacity.    Last winter was my first with solar and I ended up having to go turn off the inverter.  I was producing about 5-10w through the snow.  It was enough to trickle charge the battery but not more than that. 

I want to experiment with thermal collectors one of these days actually.  The evacuated tube ones are expensive, but DIY ones with double pane glass with the pipes inside an insulated box probably won't be that expensive to make.  They are more maintenance though.  Was reading up on glycol based water loops as I was thinking of doing my garage slab and you basically need to flush the whole system and change the glycol once a year or it starts to go acidic and it will start to eat through various components like metal pipe fittings, pump seals, etc.   With pex I guess you could risk it and go with just water, but it will still cause damage if it freezes, and of course be out of commission for the year as the pump won't be able to run anymore. Where the pipe enters the box it will also break the box itself or the pipe will break.
« Last Edit: August 10, 2019, 01:59:49 am by Red Squirrel »
 

Online tszabooTopic starter

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Re: Solar frickin' wall of block of flats
« Reply #27 on: August 10, 2019, 08:41:56 am »
Pvgis says if it is 19.5 kW (65x300W) peak power it makes aprox. 14 MWh per year if vertical and 20 MWh if optimal angle (in Strasbourg).  That is still far from covering all energy use, should have at least covered the whole wall with panels.
Wow that is a very good free calculator. That 30% estimated loss is also spot on.
If you live at a higher latitude it may be more efficient to mount the panels vertically versus horizontally.
It is at 48°, about where the USA Canada border is.

Why wouldn't the pivot point be at 45° latitude? What am I overlooking -- the increasing athmospheric scatter/absorption at low angles?
To be honest, This could make more sense. If you would tilt all panels by 45 degrees, you would get partial shading on the lower panels during the day. Partial shading is bad, because the shaded cells will actually lower the output. Or you need to put diodes on them, making it more expensive.

Technical journalism is as bad as ever though, especially when the writer goes with the name Uber Geek.

"The solar panels generate enough power on an annual basis to power 55 homes with power for one year."

Translation: 'The solar panels provide enough power to supply 55 homes'.
Well, yes and no. The sentence is bad, but it talks about summing the production and summing the consumption.

If a single apartment is using all the panels, with a large enough battery pack, they will get away with free power.
I think just the panels are for the building itself only saving some money for the landlords.
This is very likely run by the city as a green project. Nobody does batteries in Europe, because it doesnt make sense. Grid is available 99.999% of the time, and electricity from the battery is more expensive than the grid.
I wonder what is the ROI of those molten salt water heater batteries though.
 

Offline Miyuki

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Re: Solar frickin' wall of block of flats
« Reply #28 on: August 10, 2019, 09:46:34 am »
This is very likely run by the city as a green project. Nobody does batteries in Europe, because it doesnt make sense. Grid is available 99.999% of the time, and electricity from the battery is more expensive than the grid.
I wonder what is the ROI of those molten salt water heater batteries though.
It depends on country, at big scale it have no sense, but for end users it have, because end users in some countries pays high prices on energy to support "renewables"
And today prices of LiIon and LiFePo are low it makes financial sense
 

Offline Marco

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Re: Solar frickin' wall of block of flats
« Reply #29 on: August 10, 2019, 12:39:12 pm »
I want to experiment with nichrome wire or something to see if whatever energy I have stored in the batteries would be enough to clear at least two of the panels when we do get freezing rain, then at least in winter I would have SOME capacity.

You could also try ice rejecting coatings, recently read a paper with recipes consisting of commercial PU resin with vegetable oil. Seems DIY'able, would just need to replace their use of Vytaflex with Clear Flex.
 

Offline Nauris

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Re: Solar frickin' wall of block of flats
« Reply #30 on: August 10, 2019, 02:24:13 pm »
I want to experiment with nichrome wire or something to see if whatever energy I have stored in the batteries would be enough to clear at least two of the panels when we do get freezing rain, then at least in winter I would have SOME capacity.   
Quite many panels are rated up to 20A reverse current, maybe that could be used to heat it?

I want to experiment with thermal collectors one of these days actually.  The evacuated tube ones are expensive, but DIY ones with double pane glass with the pipes inside an insulated box probably won't be that expensive to make.  They are more maintenance though.  Was reading up on glycol based water loops as I was thinking of doing my garage slab and you basically need to flush the whole system and change the glycol once a year or it starts to go acidic and it will start to eat through various components like metal pipe fittings, pump seals, etc.   With pex I guess you could risk it and go with just water, but it will still cause damage if it freezes, and of course be out of commission for the year as the pump won't be able to run anymore. Where the pipe enters the box it will also break the box itself or the pipe will break.
That is only if you use pure glygol, if you use good automotive antifreeze it has all sorts of additives to prevent that. It should last decades.
Greenhouse farmers here use used antifreeze from scrap yards in their heating loops. It really doesn't get any cheaper than that and apparently works well enought.
 

Offline Red Squirrel

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Re: Solar frickin' wall of block of flats
« Reply #31 on: August 10, 2019, 04:21:23 pm »
Yeah had thought of backfeeding but that gets a bit more complex, need big relays and stuff to switch power from controller to a power supply etc.  I'd probably do the separate heater that way as it melts (assuming the idea works) then the panels can start generating right away which would contribute to the power being used to melt the snow.  I'd probably put a temp sensor on each panel and use a constant temperature power supply with some constraints.  Nice thing with such a load is I can just do PWM.  Probably run it off the inverter or just have a separate boost converter.   Probably want to blast it with like 1kw until you reach the desired temp (like +5c or something) and do one panel at a time.

Thought of using automotive coolant too if I did water loops, probably what I'd end up doing.  Just harder to get that stuff in bulk. Then again not even sure where to buy glycol either.  Not like you can just walk into a store and buy a 55gal drum of it.   Probably do a heat exchanger setup so the indoor portion can use just water then you don't need as much actual coolant.   I have a random section of double pane window glass in my basement that is a good size to do a small prototype panel.
 

Offline Circlotron

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Re: Solar frickin' wall of block of flats
« Reply #32 on: August 10, 2019, 11:39:14 pm »
I think the idea of a solar panel overlaid on a thermal collector might be interesting. In the winter months hot water could be passed through the tubes to defrost the solar panels and in the summer the solar collectors would make warm water as well as reducing the temperature of the solar panels, therefore keeping them in a more efficient range. With mine, in summertime after the sun comes out from a number of minutes behind the clouds the power goes up to 1500W for a short time before gradually sinking back to 1100W as the panels heat up again.
 

Offline Red Squirrel

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Re: Solar frickin' wall of block of flats
« Reply #33 on: August 12, 2019, 03:01:48 am »
Yeah could be interesting, not sure if the energy usage to run the pumps would be worth it, but maybe it would.

Another thing I thought of if I did the nichrome wire idea would be to actually enclose the back in foam insulation, but have fans.  In winter you don't run the fans but in summer you could.  Again not sure if the power usage to run the fans would be worth it. Though if the panels heating up reduce their life span, then that alone makes it worth cooling them, so they last longer.  Another option for summer might be a mist system that just mists water on them.  Doubles as a way to clean them, but I think any of these solutions just add more complexity than is needed.

My ideal setup would be a large ground mount setup that is inclined more then that would take care of all the issues including snow.  I need a bigger property. :P
 

Online tszabooTopic starter

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Re: Solar frickin' wall of block of flats
« Reply #34 on: August 12, 2019, 08:26:30 am »
Yeah could be interesting, not sure if the energy usage to run the pumps would be worth it, but maybe it would.

Another thing I thought of if I did the nichrome wire idea would be to actually enclose the back in foam insulation, but have fans.  In winter you don't run the fans but in summer you could.  Again not sure if the power usage to run the fans would be worth it. Though if the panels heating up reduce their life span, then that alone makes it worth cooling them, so they last longer.  Another option for summer might be a mist system that just mists water on them.  Doubles as a way to clean them, but I think any of these solutions just add more complexity than is needed.

My ideal setup would be a large ground mount setup that is inclined more then that would take care of all the issues including snow.  I need a bigger property. :P
We had a neighbor who had the idea of cooling the roof by spraying water on it.
So water evaporates,  leaves calcium back, which is PITA to get out of your roof. Or your from your panels.

I think we did the calculation on the solar roadway topic. Melting snow with electricity on solar panels has negative  energy budget, because melting takes a huge amount of energy.
 

Offline ciccio

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Re: Solar frickin' wall of block of flats
« Reply #35 on: August 12, 2019, 11:11:01 am »
Years ago I visited a friend  living in Strasbourg.  The building was a municipal building, and heating and hot water were supplied by a big central unit serving more than one building, maybe the whole neighborhood.
We have one example here in Italy in the town of Brescia where the surplus heat coming from a very big trash incinerator https://www.a2a.eu/it/gruppo/i-nostri-impianti/termoutilizzatori/brescia is used by a lot of houses and offices (I think about 70% of 200.000 inhabitants of the city)
Maybe the panels are simple PV units connected to the distribution network.

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Offline Red Squirrel

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Re: Solar frickin' wall of block of flats
« Reply #36 on: August 12, 2019, 06:27:34 pm »
Yeah could be interesting, not sure if the energy usage to run the pumps would be worth it, but maybe it would.

Another thing I thought of if I did the nichrome wire idea would be to actually enclose the back in foam insulation, but have fans.  In winter you don't run the fans but in summer you could.  Again not sure if the power usage to run the fans would be worth it. Though if the panels heating up reduce their life span, then that alone makes it worth cooling them, so they last longer.  Another option for summer might be a mist system that just mists water on them.  Doubles as a way to clean them, but I think any of these solutions just add more complexity than is needed.

My ideal setup would be a large ground mount setup that is inclined more then that would take care of all the issues including snow.  I need a bigger property. :P
We had a neighbor who had the idea of cooling the roof by spraying water on it.
So water evaporates,  leaves calcium back, which is PITA to get out of your roof. Or your from your panels.

I think we did the calculation on the solar roadway topic. Melting snow with electricity on solar panels has negative  energy budget, because melting takes a huge amount of energy.

Never thought of that, the minerals in the water would eventually just cake on the panels.   And yeah the amount of heat required to melt snow is insane.  With tilted panels at least there is a chance of simply melting enough of it so the rest slides off, but even then.

My city installed heated steps on city hall.   Probably a liability thing to show they tried, if someone slips and falls. Either way, it's BS from a tech standpoint.  They end up having to shovel them every morning anyway.   I forget how much they had paid for those in was like 700k or something insane like that.
 

Offline SiliconWizard

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Re: Solar frickin' wall of block of flats
« Reply #37 on: August 12, 2019, 06:30:56 pm »
My city installed heated steps on city hall.   Probably a liability thing to show they tried, if someone slips and falls. Either way, it's BS from a tech standpoint.  They end up having to shovel them every morning anyway.

Not only that, but melted snow can be much more slippery as well?
 

Offline ChunkyPastaSauce

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Re: Solar frickin' wall of block of flats
« Reply #38 on: August 12, 2019, 06:50:42 pm »
Yeah could be interesting, not sure if the energy usage to run the pumps would be worth it, but maybe it would.

Another thing I thought of if I did the nichrome wire idea would be to actually enclose the back in foam insulation, but have fans.  In winter you don't run the fans but in summer you could.  Again not sure if the power usage to run the fans would be worth it. Though if the panels heating up reduce their life span, then that alone makes it worth cooling them, so they last longer.  Another option for summer might be a mist system that just mists water on them.  Doubles as a way to clean them, but I think any of these solutions just add more complexity than is needed.

My ideal setup would be a large ground mount setup that is inclined more then that would take care of all the issues including snow.  I need a bigger property. :P
We had a neighbor who had the idea of cooling the roof by spraying water on it.
So water evaporates,  leaves calcium back, which is PITA to get out of your roof. Or your from your panels.

I think we did the calculation on the solar roadway topic. Melting snow with electricity on solar panels has negative  energy budget, because melting takes a huge amount of energy.

Never thought of that, the minerals in the water would eventually just cake on the panels.   And yeah the amount of heat required to melt snow is insane.  With tilted panels at least there is a chance of simply melting enough of it so the rest slides off, but even then.

Also the melt will refreeze as soon as it departs a heated panel, so the roof will probably have ice damming problems.
 

Offline Deodand2014

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Re: Solar frickin' wall of block of flats
« Reply #39 on: August 13, 2019, 03:10:02 am »
Yeah could be interesting, not sure if the energy usage to run the pumps would be worth it, but maybe it would.

Another thing I thought of if I did the nichrome wire idea would be to actually enclose the back in foam insulation, but have fans.  In winter you don't run the fans but in summer you could.  Again not sure if the power usage to run the fans would be worth it. Though if the panels heating up reduce their life span, then that alone makes it worth cooling them, so they last longer.  Another option for summer might be a mist system that just mists water on them.  Doubles as a way to clean them, but I think any of these solutions just add more complexity than is needed.

My ideal setup would be a large ground mount setup that is inclined more then that would take care of all the issues including snow.  I need a bigger property. :P
We had a neighbor who had the idea of cooling the roof by spraying water on it.
So water evaporates,  leaves calcium back, which is PITA to get out of your roof. Or your from your panels.

I think we did the calculation on the solar roadway topic. Melting snow with electricity on solar panels has negative  energy budget, because melting takes a huge amount of energy.

Never thought of that, the minerals in the water would eventually just cake on the panels.   And yeah the amount of heat required to melt snow is insane.  With tilted panels at least there is a chance of simply melting enough of it so the rest slides off, but even then.

Also the melt will refreeze as soon as it departs a heated panel, so the roof will probably have ice damming problems.

Somewhere in my collection of 1970s era NASA solar energy documents is discussion of running liquid silicone through the panels to a heat exchanger so that you don't have the risk of ice forming in the collector.
 


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