EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: tszaboo on August 08, 2019, 06:09:34 pm
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I don't think this was mentioned before.
I was visiting Strassbourg (France)some years ago, and saw this.
The panels are mounted on the side of a flock of flats.
Some notes: There isn't a building close by, to shade these panels.
They are facing south. ( hint for Australians, that's good)
There seems to be some panels on the top of the building (according to satellite image) but there is plenty of space there to put extra panels.
This will create bigger output in winter, than an optimal fixed angle installation.
https://www.google.be/maps/@48.5756815,7.771481,3a,75y,320.97h,97.44t/data=!3m6!1e1!3m4!1sOgYapgZWMuqW3L2Tfs3kvw!2e0!7i16384!8i8192 (https://www.google.be/maps/@48.5756815,7.771481,3a,75y,320.97h,97.44t/data=!3m6!1e1!3m4!1sOgYapgZWMuqW3L2Tfs3kvw!2e0!7i16384!8i8192)
[attach=1]
What do I think? I think vertical installation makes sense. It is better than having a billboard or an ugly gray wall. The two building has 65-65 panels, which would operate at around 70% efficiency (does anyone have a calculator for this?).
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Amateurs!
These guys have covered three sides of a skyscraper https://wonderfulengineering.com/worlds-first-skyscraper-that-is-covered-with-solar-panels/
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There are some flats in China with solar panels on the wall above/below each row of windows in the tower. This kind of thing might well make sense in northern climates where the sun is low in the sky during the season of maximum demand. There are other flats with solar thermal tube assemblies in a similar location.
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Those are probably solarthermal-panels, as mounting them in such a way is quite common.
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Amateurs!
These guys have covered three sides of a skyscraper https://wonderfulengineering.com/worlds-first-skyscraper-that-is-covered-with-solar-panels/
It seems like that was a remedial move after the tower's original construction was screwed up, and the original facing started falling off within months of occupation. I sense some greenwashing, to try to tone down the ridicule about the original facing.
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Those are probably solarthermal-panels, as mounting them in such a way is quite common.
No, if you look closer on Streetview you can see they are photoelectric cells facing south. The roofs are not covered with cells.
I wonder why thy are mounted flat. A slight tilt upward would probably gain much without too much hurting the installation.
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Those are probably solarthermal-panels, as mounting them in such a way is quite common.
Solarthermal collectors seem to be getting badly ignored these days in the race to put up Photovoltaic ones. They have very high thermal efficiency and having a decent supply of hot water in the house is a lot more useful. Electrically heating water takes a surprising amount of electricity especially when that electricity is coming from low efficiency photovoltaic panels.
EDIT: You also don't need space consuming inverters, just a couple of temperature sensors, and an water pump.
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Those are probably solarthermal-panels, as mounting them in such a way is quite common.
Solarthermal collectors seem to be getting badly ignored these days in the race to put up Photovoltaic ones.
True, but they are not ignored by all.
Funnily enough, countries that live off oil like Qatar and Saudi Arabia have whole farms of solarthermal collectors. Meanwhile, countries that use a lot of oil but don't produce any seem to favor PV panels.
Go figure. ;D
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If you live at a higher latitude it may be more efficient to mount the panels vertically versus horizontally. Of course, if you have the option for a fixed mounting you'd want to angle the panels a bit shallower than (90 - average elevation angle of the Sun) over the year. But, on an office building or tower like structure, mounting the panels on the south facing wall (northern hemisphere) or north facing wall (southern hemisphere) -- the problem is that if another building is built next to the Sun side of the building and it blocks the Sun then you're power generation is significantly reduced.
Imagine a building in the northern hemisphere at, say, a 50N latitude on the north shore of a body of water such that no other building can be built that might obscure the Sun. If that building were, say, 100m wide on the sun facing side and 300m tall it might generate as much as 3MW and over an average day perhaps 16-20MWh per day -- that amount of power/energy might well be more than the building needs. Of course, window area would likely reduce the power/energy generated by a third or more. But, there are solar windows that generate some power while providing visibility through them so the net could be 75% of a full coverage system or, in this example, about 12-15MWh/day which could be enough to fully power the building.
Brian
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Those are probably solarthermal-panels, as mounting them in such a way is quite common.
Solarthermal collectors seem to be getting badly ignored these days in the race to put up Photovoltaic ones. They have very high thermal efficiency and having a decent supply of hot water in the house is a lot more useful. Electrically heating water takes a surprising amount of electricity especially when that electricity is coming from low efficiency photovoltaic panels.
EDIT: You also don't need space consuming inverters, just a couple of temperature sensors, and an water pump.
These are PV.
In most climates, collectors dont make sense anymore. It is cheaper to add a few panels to a pv installation, and have an electric boiler. It costs about 3500 EUR here, to make hot water of a family of 4, 4 sqm system. The same buys you a 10 panel system.
Also, you need a heat exchanger, regular maintenance, complicated control for hot water for heating and shower, etc... PV is just a lot easier to do.
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.
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Those are probably solarthermal-panels, as mounting them in such a way is quite common.
Solarthermal collectors seem to be getting badly ignored these days in the race to put up Photovoltaic ones. They have very high thermal efficiency and having a decent supply of hot water in the house is a lot more useful. Electrically heating water takes a surprising amount of electricity especially when that electricity is coming from low efficiency photovoltaic panels.
EDIT: You also don't need space consuming inverters, just a couple of temperature sensors, and an water pump.
Inverters are not a big space eater -- how are you going to store the heated water? Does the inverter consume more space than the water storage tank? Yes, homes have water heaters now and most have a storage tank, but to store the amount of water needed the tank would almost certainly need to be larger -- conventional water heaters do not store a days worth of heated water and in fact tend to only have about 1-2 showers worth of storage. Additionally, many new homes use on-demand or tankless water heaters.
Brian
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Those are probably solarthermal-panels, as mounting them in such a way is quite common.
Solarthermal collectors seem to be getting badly ignored these days in the race to put up Photovoltaic ones. They have very high thermal efficiency and having a decent supply of hot water in the house is a lot more useful. Electrically heating water takes a surprising amount of electricity especially when that electricity is coming from low efficiency photovoltaic panels.
EDIT: You also don't need space consuming inverters, just a couple of temperature sensors, and an water pump.
These are PV.
In most climates, collectors dont make sense anymore. It is cheaper to add a few panels to a pv installation, and have an electric boiler. It costs about 3500 EUR here, to make hot water of a family of 4, 4 sqm system. The same buys you a 10 panel system.
Also, you need a heat exchanger, regular maintenance, complicated control for hot water for heating and shower, etc... PV is just a lot easier to do.
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.
Yes, the US Canada border is right around the 48-50 degree north line so most of Canada is above 50N while most of the US is below 50N. A good bit of Europe is right around 50N with the UK and Scandinavia being above or well above that.
https://www.energy.gov/eere/articles/five-fun-facts-about-nrel-s-new-solar-windows-innovation (https://www.energy.gov/eere/articles/five-fun-facts-about-nrel-s-new-solar-windows-innovation)
https://pv-magazine-usa.com/2018/11/21/a-15-efficient-solar-window-that-delivers-120-of-us-electricity/ (https://pv-magazine-usa.com/2018/11/21/a-15-efficient-solar-window-that-delivers-120-of-us-electricity/)
It appears that the efficiency of some of these solar windows is greater than I though -- above 11%.
Brian
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Solar collectors have important limits on how cheap they can get, PV will get to the point where it has a negative cost as a facing material relative to any alternative. Glass isn't the cheapest facing material, but it's functional and with the electricity it's going to be a non brainer.
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Yes, the US Canada border is right around the 48-50 degree north line so most of Canada is above 50N while most of the US is below 50N. A good bit of Europe is right around 50N with the UK and Scandinavia being above or well above that.
Only two significant Canadian cities (Edmonton, Calgary) are north of of the 50th. Probably 80+% of the Canadian population lives south of 50N
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Yes, the US Canada border is right around the 48-50 degree north line so most of Canada is above 50N while most of the US is below 50N. A good bit of Europe is right around 50N with the UK and Scandinavia being above or well above that.
Only two significant Canadian cities (Edmonton, Calgary) are north of of the 50th. Probably 80+% of the Canadian population lives south of 50N
Yes, in the east the main cities are more like 45N even as the large landmass of Canada is mostly above 50N. Still, 45N is in the ballpark of 50N and would be right at the point were vertical surpasses horizontal mounting of solar panels/windows. The main problem with exterior wall/window solar is that you have to be unobscured by other buildings so in an urban setting only those buildings at the southern edge (northern hemisphere) will get full Sun while other buildings further north will get less Sun. But, if you do have such a location you might be able to generate all the energy needs of the building.
Brian
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Yes, the US Canada border is right around the 48-50 degree north line so most of Canada is above 50N while most of the US is below 50N. A good bit of Europe is right around 50N with the UK and Scandinavia being above or well above that.
Only two significant Canadian cities (Edmonton, Calgary) are north of of the 50th. Probably 80+% of the Canadian population lives south of 50N
Yes, in the east the main cities are more like 45N even as the large landmass of Canada is mostly above 50N. Still, 45N is in the ballpark of 50N and would be right at the point were vertical surpasses horizontal mounting of solar panels/windows. The main problem with exterior wall/window solar is that you have to be unobscured by other buildings so in an urban setting only those buildings at the southern edge (northern hemisphere) will get full Sun while other buildings further north will get less Sun. But, if you do have such a location you might be able to generate all the energy needs of the building.
Brian
If you look at the picture, there is about 3x8x3=72 apartments and 65 solar panels in one building. That is not going to be even close to "all the need". In fact I dont think any apartment building could provide enough solar to break even. Most standalone houses barely have enough capacity for their electricity need, excluding heating, which needs more power.
And to return for solar collectors for one more second: I was talking about home systems. Large scale systems have totally different economics.
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Solarthermal collectors seem to be getting badly ignored these days in the race to put up Photovoltaic ones. They have very high thermal efficiency and having a decent supply of hot water in the house is a lot more useful. Electrically heating water takes a surprising amount of electricity especially when that electricity is coming from low efficiency photovoltaic panels.
A heat pump water heater (for hot water, not space heating) uses on the order of 300-500W. Pretty easy to power even on a 12V system.
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At least you are less likely to have a bus driving over them. ;D
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Ahhh thats the problem, got hit by the bus!
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I don't think this was mentioned before.
I was visiting Strassbourg (France)some years ago, and saw this.
The panels are mounted on the side of a flock of flats.
Some notes: There isn't a building close by, to shade these panels.
They are facing south. ( hint for Australians, that's good)
There seems to be some panels on the top of the building (according to satellite image) but there is plenty of space there to put extra panels.
This will create bigger output in winter, than an optimal fixed angle installation.
https://www.google.be/maps/@48.5756815,7.771481,3a,75y,320.97h,97.44t/data=!3m6!1e1!3m4!1sOgYapgZWMuqW3L2Tfs3kvw!2e0!7i16384!8i8192 (https://www.google.be/maps/@48.5756815,7.771481,3a,75y,320.97h,97.44t/data=!3m6!1e1!3m4!1sOgYapgZWMuqW3L2Tfs3kvw!2e0!7i16384!8i8192)
(Attachment Link)
What do I think? I think vertical installation makes sense. It is better than having a billboard or an ugly gray wall. The two building has 65-65 panels, which would operate at around 70% efficiency (does anyone have a calculator for this?).
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.
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Amateurs!
These guys have covered three sides of a skyscraper https://wonderfulengineering.com/worlds-first-skyscraper-that-is-covered-with-solar-panels/
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'.
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I am at 50 north and vertical solar panels according to calculation makes sense as it flattens power production during year (makes more in winter and lower in summer, in year total it is similar amount of energy, but is better for real utilization)
But not have connected installation yet to measure real results
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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.
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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?
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Solar collectors have important limits on how cheap they can get,
True, and likely the main reason why they are not deployed more.
PV will get to the point where it has a negative cost as a facing material relative to any alternative. Glass isn't the cheapest facing material, but it's functional and with the electricity it's going to be a non brainer.
Well, I'm not sure about that though.
And if that becomes true cost-wise, I'm not sure either about the respective qualities of PV as a facing material. For instance as to their resistance to fire, and other criterions... Cost is a thing, but if we are going to make all buildings a fire hazard, this can't be that good.
One question I also have is whether PV panels don't tend to heat up facades/roofs more than many other materials, which in countries where heat is a problem, and A/C has enormous costs, would probably not be worth it. I'd be interested in having the POV and experience of people having panels on their house's roof. Is the house temperature rising because of them or does it have no measurable impact?
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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.
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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.
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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.
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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
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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 (https://advances.sciencemag.org/content/2/3/e1501496) 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.
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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.
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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.
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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.
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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
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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.
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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 (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.
Best regards
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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.
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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?
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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.
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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.