9 ms·

Researchers shed light on higher energy yields in vertical PV systems

66 points by perfunctory 3y ago

stephen_g 3y ago
Interesting, definitely a surprising result. I did wonder when I saw a thumbnail of a video discussing this on YouTube (but I didn’t have time to watch it) - I thought “Surely that only works for bifacial panels” so makes sense that the article confirms that that’s what they were testing. The other factor is that (compared to where I live in Australia at least, but also all of the US too) the Netherlands is quite far from the equator, so I expect there would be a crossover point a bit closer to the equator where you start to get less efficiency than standard angled horizontal panels? Although perhaps with some reflectors on either side it might still work with a vertical bifacial panel (in areas closer to the equator), maintaining the cooling advantage?
- tonyarkles 3y ago
  Yeah, I'm quite curious about the overall tradeoff here. I'm at about 51 deg N and the solar elevation angle gets very very low during the winter (only 16 degrees elevation at noon) but high in the summer (63 degrees elevation at noon). Because of how low the sun is we end up with very long shadows even mid-day in the winter. Would love to spend the time breaking down: - land area required for tilted vs. vertical - net production over the year - equipment cost for bifacial panels vs single-face panels Anything that helps solar cost/performance is a huge win around here because we have max energy consumption in the winter when solar doesn't produce a whole lot.
- jacquesm 3y ago
  I'm curious about how well this performs in winter when the sun is low in the sky and you have a pretty big deficiency. Usually you use what ever angle the roof is at (typically 30 - 45 degrees) and leave it at that. By adding a vertical component you may be able to substantially offset the summer/winter difference. Vertical panels won't do much in the summer but that's fine, you'll have a surplus anyway. But in winter you need every little bit. But from a ROI point of view those would be pretty expensive KWh, because the total produced versus the capital expense won't be very high. And in plenty of places the local authorities might have something to say about covering the outside of the building with panels. I'm going to play around with this here to see what it does.
  - Phenomenit 3y ago
    I live in the edge of a row of townhouses and have a huge wall doing nothing but cooling the house. I’ve been thinking about having vertical panels on the wall and my fear is exactly what you described, that all RoI calculations are based on producing a lot of power during the summer half of the year and I that I will not recoup the money but the problem is that when it’s sunny outside everybody is producing electricity and the prices are low so I think the RoI don’t really take this in to account. My wall is on the sout side and gets sunlight all day, is much larger than my roof, doesn’t get covered with snow. The prices electricity are usually 10-20x higher during the winter and our consumption is also 10x higher. I don’t know it just seems to make more sense to put them on the wall.
    - jacquesm 3y ago
      I think you should factor the savings on AC in the summer and heating in winter as well into your calculation. For that to be most efficient the air would need to be trapped behind the panel, I don't think you need to worry about overheating so much because they are going to be running at a low fraction of their theoretical capacity. There is a fair chance that including savings on heating and cooling it will actually work out but I haven't run the numbers in detail. But it certainly is an intriguing proposition, even if it would work only on South facing walls.
      - Phenomenit 3y ago
        We don’t have AC installed so our only major energy cost during the summer is hot water . Yeah it’s definitely worth doing som maths. One major pain point though is that we need a permit for vertical panels because it affects the look of the house.
        jacquesm 3y ago
        > we need a permit for vertical panels because it affects the look of the house That's fairly common, but usually only on the front of the house. And on extra buildings like a garage or a garden shed such restrictions may not apply. This is pretty trick and it varies enough from one place to another (even within the same country, province or state) that it is worth researching before embarking on such a project.
munchler 3y ago
If, like me, you don’t know what PV stands for: A photovoltaic (PV) cell, commonly called a solar cell, is a nonmechanical device that converts sunlight directly into electricity.
- whycome 3y ago
  There are so many fields that find their way onto HN yet each one acts like their domain-specifc jargon or acronym is common knowledge.
  - taneq 3y ago
    Yeah, it's a real (A)GKDM. (A "(possibly accidental) gatekeeping dick move" :P )
    - yonatan8070 3y ago
      Someone should implement a "DeJargonify" button that looks through a dictionary of acronyms and shows you a table of ehat they mean I use Hacki on Android, could be a fun project to try adding that if I get time to do it
- jvanderbot 3y ago
  Today you're one of the 10,000! https://xkcd.com/1053/ https://xkcd.com/1053/
exabrial 3y ago
Summary (roughly, I skipped some things): while tilted panels produce more voltage, their efficiency drops due to heat absorption. Two sided vertical panels allow for better cooling, and on average produce more power, roughly 2%ish, albeit more expensive to produce.
jvanderbot 3y ago
The moneyshot is > “For a standard system, we observed that under high irradiance conditions, the increase due to the light is offset by the decrease due to the higher operating temperature,” Van Aken stressed. “However, for the vertical system, we observed that the operating temperature is not increasing so much and the voltage increase and decrease are more or less balancing.” Facing the bright sun increases temperature enough to offset the gains in voltage (since temperature increases presumably increase resistance if my EE101 classes hold in this era). Not facing the sun? Less heat -> more total power throughput.
- woleium 3y ago
  So we could get the best of both worlds (optimal light incidence angle and heat dissipation) with floating solar on a pond or lake?
  - ReptileMan 3y ago
    Or pipes of cold water running under the panel to generate heat for showering
    - HPsquared 3y ago
      Combined heat and power!
      - bloomingeek 3y ago
        Wow and wow! I've been wanting to jump into a home solar system, I just think there's to many inefficiencies. Hopefully this is the way solar will evolve in the near future.
        Taek 3y ago
        Don't let perfect be the enemy of good, solar already makes a lot of sense and is good for the environment.
    - 3y ago
wongarsu 3y ago
I imagine installation costs are also substantially lower since the panels rest on a much simpler structure. Cleaning the panels should also be easier in this configuration. I wouldn't be surprised if these findings lead to vertical solar systems becoming a popular option, especially in places as far from the equator as Denmark.
- pfdietz 3y ago
  The output can also be timed for better value (for example, increasing production in winter vs. summer, or peaking early and late for N/S aligned modules.) Combinations of different orientations can smooth output over a day or year, which could reduce the mismatch between module output and inverter capacity.
myself248 3y ago
It's not mysterious, it's that thermal convection is much stronger when the panels are vertical, and production is strongly correlated with lower temperature. Angled mounts tend to have obnoxious cross-members that block the airflow that should otherwise be sliding up the back of the panel, particularly on roofs where there's basically a bed of hot air trapped underneath with no good way to escape. That boosts the panel temperatures even further than you'd assume given simply lower convection based on their angle alone. Vertical mounts cannot have framing in these places, so they don't.
- tonyarkles 3y ago
  > It's not mysterious, it's that thermal convection is much stronger when the panels are vertical I agree that, when you factor in semiconductor physics, it's not a mystery but it isn't necessarily an intuitive result for most. I've been working in aerospace for 5 years and one of the things that has been very clear to me is that peoples' intuition about things breaks down very quickly when there's non-linear factors involved in an analysis. In aero it's primarily square-law/cube-law tradeoffs; in semiconductor physics it'll be more exponential. For this particular problem you've got an exponential (semiconductor behaviour as a function of temperature) multiplied by a trig function/dot product (cosine of the angle of the sun relative to the normal of the solar panel), with a bit of natural thermal convection thrown in for good measure. Modelling this (digital twin, as they call it) is feasible but it's not something most people are going to have a good intuition on with respect to where the sweet spot is going to be.
  - CyberDildonics 3y ago
    The average person's intuition and 'mysterious' are two different things. One is someone with no knowledge assuming the wrong thing, the other is experts not able to figure something out.
  - jacquesm 3y ago
    The air near the top is 100% trapped, there is no way for it to escape and it's the hottest air under the panel. Overlap with the cells is anywhere from 1/2" to 1.5" so that's a sizeable fraction of the cells. Probably close to 25 to 30% or so.
aqme28 3y ago
Wow, I was just talking to my dad about this. He runs a startup that builds PV-embedded vertical masonry[1], and they have been getting significantly higher-than-expected yield on their installations. Though in their case they were mostly theorizing ground reflections [1]: (https://www.solablock.com/ https://www.solablock.com/, looking for investors!)
- taneq 3y ago
  Are the PV panels mounted directly on the masonry? ...oh wait clicks link yeah maybe the masonry is acting as a heatsink for the panels as well?
  - aqme28 3y ago
    They're embedded in the masonry. When you buy a CMU, you get one unit. Yes, this has better thermal properties, and this also makes them more durable and theft/vandal resistant.
- wongarsu 3y ago
  That's a cool project. One advantage solar masonry might have is the high thermal mass of masonry. The bricks average out day and night temperatures, and probably keep the panels a lot colder than they would be on their own.
  - jacquesm 3y ago
    And as an extra bonus they slow the heat exchange with the outside air so it works as insulation both in summer and in winter.
  - Workaccount2 3y ago
    If anything I would think that the poor thermal conductance of the masonry would make this inferior to simply mounting panels over the exterior with an air gap.
    - deleted 3y ago
lostmsu 3y ago
So probably adding active cooling (e.g. fan) to existing installations would help even more.
- Aspos 3y ago
  A wind catcher turbine of some sort?
- fnordpiglet 3y ago
  This was exactly my question, have people looked at the various thermal management techniques used in computing? Heat pipes on the backplane and fan cooled heat sink blocks could go a long way.
DemocracyFTW2 3y ago
Spoiler: vertical panels can rid themselves of excess heat more efficiently, thus operating temperatures are lower and, hence, output better. Vertical panels will also be more susceptible to damage from high winds but less susceptible to precipitation of water and dust, so my guess would be that the fixed slant orientation for PV panels in temperate latitudes will stay with us irrespective. I'm starting to think about having water pipes running along the backsides of the panels to cool them and obtain warm or hot water...
- estiaan 3y ago
  I’ve seen people cooling solar panels by using coreflute/Fluteboard at the back of a panel and circulating pool water through the channels. I think I saw this on Linus Tech Tips weirdly enough, not sure though
1970-01-01 3y ago
IIRC, there was a boy that did a similar experiment and was lambasted for measuring voltage instead of power: https://www.zdnet.com/article/why-13-year-olds-solar-power-breakthrough-wont-work/ https://www.zdnet.com/article/why-13-year-olds-solar-power-b... https://web.archive.org/web/20160308193750/http://www.wsj.com/articles/SB10001424052970203550304577138511287470508 https://web.archive.org/web/20160308193750/http://www.wsj.co...
maxglute 3y ago
This seems like something that should have been verified in lab/field decades ago, before billions in mass solar roll out. I'm assuming it is and large scale solar infra are optimized according to site conditions?
- heavenlyblue 3y ago
  The markets stay irrational longer than you can stay solvent
mrbgty 3y ago
Curious why they don't seem to be stacking them up or making them taller? Wind? Shade? If they were on a pole allowing the wind to turn them, could you get both wind and solar power at the same time?
hankman86 3y ago
Here in Australia, News Corp (owned by the same Murdoch family who is also behind Fox News) is currently running a campaign against agricultural solar. A key “argument” being that installing solar panels on fields makes it impossible to grow crops there.
- estiaan 3y ago
  I live in Aus as well, and I don’t expose myself to News Corp at all. Can you explain to me what the heck the issue is? We have so much space and we don’t need that much more solar, how is anyone’s crops at risk? Is this just a complete non issue? Like i agree that solar panels shouldn’t be installed over the top of crops but is that even a thing that is happening? Don’t the farmers have almost complete control of what goes on their property anyway? So confused
  - triceratops 3y ago
    News Corp is anti-renewable energy. No need to look for a deeper explanation than that.

66 points by perfunctory 3y ago

Interesting, definitely a surprising result. I did wonder when I saw a thumbnail of a video discussing this on YouTube (but I didn’t have time to watch it) - I thought “Surely that only works for bifacial panels” so makes sense that the article confirms that that’s what they were testing. The other factor is that (compared to where I live in Australia at least, but also all of the US too) the Netherlands is quite far from the equator, so I expect there would be a crossover point a bit closer to the equator where you start to get less efficiency than standard angled horizontal panels? Although perhaps with some reflectors on either side it might still work with a vertical bifacial panel (in areas closer to the equator), maintaining the cooling advantage?

tonyarkles 3y ago
Yeah, I'm quite curious about the overall tradeoff here. I'm at about 51 deg N and the solar elevation angle gets very very low during the winter (only 16 degrees elevation at noon) but high in the summer (63 degrees elevation at noon). Because of how low the sun is we end up with very long shadows even mid-day in the winter. Would love to spend the time breaking down: - land area required for tilted vs. vertical - net production over the year - equipment cost for bifacial panels vs single-face panels Anything that helps solar cost/performance is a huge win around here because we have max energy consumption in the winter when solar doesn't produce a whole lot.
jacquesm 3y ago
I'm curious about how well this performs in winter when the sun is low in the sky and you have a pretty big deficiency. Usually you use what ever angle the roof is at (typically 30 - 45 degrees) and leave it at that. By adding a vertical component you may be able to substantially offset the summer/winter difference. Vertical panels won't do much in the summer but that's fine, you'll have a surplus anyway. But in winter you need every little bit. But from a ROI point of view those would be pretty expensive KWh, because the total produced versus the capital expense won't be very high. And in plenty of places the local authorities might have something to say about covering the outside of the building with panels. I'm going to play around with this here to see what it does.
- Phenomenit 3y ago
  I live in the edge of a row of townhouses and have a huge wall doing nothing but cooling the house. I’ve been thinking about having vertical panels on the wall and my fear is exactly what you described, that all RoI calculations are based on producing a lot of power during the summer half of the year and I that I will not recoup the money but the problem is that when it’s sunny outside everybody is producing electricity and the prices are low so I think the RoI don’t really take this in to account. My wall is on the sout side and gets sunlight all day, is much larger than my roof, doesn’t get covered with snow. The prices electricity are usually 10-20x higher during the winter and our consumption is also 10x higher. I don’t know it just seems to make more sense to put them on the wall.
  - jacquesm 3y ago
    I think you should factor the savings on AC in the summer and heating in winter as well into your calculation. For that to be most efficient the air would need to be trapped behind the panel, I don't think you need to worry about overheating so much because they are going to be running at a low fraction of their theoretical capacity. There is a fair chance that including savings on heating and cooling it will actually work out but I haven't run the numbers in detail. But it certainly is an intriguing proposition, even if it would work only on South facing walls.
    - Phenomenit 3y ago
      We don’t have AC installed so our only major energy cost during the summer is hot water . Yeah it’s definitely worth doing som maths. One major pain point though is that we need a permit for vertical panels because it affects the look of the house.
      - jacquesm 3y ago
        > we need a permit for vertical panels because it affects the look of the house That's fairly common, but usually only on the front of the house. And on extra buildings like a garage or a garden shed such restrictions may not apply. This is pretty trick and it varies enough from one place to another (even within the same country, province or state) that it is worth researching before embarking on such a project.

munchler 3y ago

If, like me, you don’t know what PV stands for: A photovoltaic (PV) cell, commonly called a solar cell, is a nonmechanical device that converts sunlight directly into electricity.

whycome 3y ago
There are so many fields that find their way onto HN yet each one acts like their domain-specifc jargon or acronym is common knowledge.
- taneq 3y ago
  Yeah, it's a real (A)GKDM. (A "(possibly accidental) gatekeeping dick move" :P )
  - yonatan8070 3y ago
    Someone should implement a "DeJargonify" button that looks through a dictionary of acronyms and shows you a table of ehat they mean I use Hacki on Android, could be a fun project to try adding that if I get time to do it
jvanderbot 3y ago
Today you're one of the 10,000! https://xkcd.com/1053/ https://xkcd.com/1053/

exabrial 3y ago

Summary (roughly, I skipped some things): while tilted panels produce more voltage, their efficiency drops due to heat absorption. Two sided vertical panels allow for better cooling, and on average produce more power, roughly 2%ish, albeit more expensive to produce.

jvanderbot 3y ago

The moneyshot is > “For a standard system, we observed that under high irradiance conditions, the increase due to the light is offset by the decrease due to the higher operating temperature,” Van Aken stressed. “However, for the vertical system, we observed that the operating temperature is not increasing so much and the voltage increase and decrease are more or less balancing.” Facing the bright sun increases temperature enough to offset the gains in voltage (since temperature increases presumably increase resistance if my EE101 classes hold in this era). Not facing the sun? Less heat -> more total power throughput.

woleium 3y ago
So we could get the best of both worlds (optimal light incidence angle and heat dissipation) with floating solar on a pond or lake?
- ReptileMan 3y ago
  Or pipes of cold water running under the panel to generate heat for showering
  - HPsquared 3y ago
    Combined heat and power!
    - bloomingeek 3y ago
      Wow and wow! I've been wanting to jump into a home solar system, I just think there's to many inefficiencies. Hopefully this is the way solar will evolve in the near future.
      - Taek 3y ago
        Don't let perfect be the enemy of good, solar already makes a lot of sense and is good for the environment.
  - 3y ago

wongarsu 3y ago

I imagine installation costs are also substantially lower since the panels rest on a much simpler structure. Cleaning the panels should also be easier in this configuration. I wouldn't be surprised if these findings lead to vertical solar systems becoming a popular option, especially in places as far from the equator as Denmark.

pfdietz 3y ago
The output can also be timed for better value (for example, increasing production in winter vs. summer, or peaking early and late for N/S aligned modules.) Combinations of different orientations can smooth output over a day or year, which could reduce the mismatch between module output and inverter capacity.

myself248 3y ago

It's not mysterious, it's that thermal convection is much stronger when the panels are vertical, and production is strongly correlated with lower temperature. Angled mounts tend to have obnoxious cross-members that block the airflow that should otherwise be sliding up the back of the panel, particularly on roofs where there's basically a bed of hot air trapped underneath with no good way to escape. That boosts the panel temperatures even further than you'd assume given simply lower convection based on their angle alone. Vertical mounts cannot have framing in these places, so they don't.

tonyarkles 3y ago
> It's not mysterious, it's that thermal convection is much stronger when the panels are vertical I agree that, when you factor in semiconductor physics, it's not a mystery but it isn't necessarily an intuitive result for most. I've been working in aerospace for 5 years and one of the things that has been very clear to me is that peoples' intuition about things breaks down very quickly when there's non-linear factors involved in an analysis. In aero it's primarily square-law/cube-law tradeoffs; in semiconductor physics it'll be more exponential. For this particular problem you've got an exponential (semiconductor behaviour as a function of temperature) multiplied by a trig function/dot product (cosine of the angle of the sun relative to the normal of the solar panel), with a bit of natural thermal convection thrown in for good measure. Modelling this (digital twin, as they call it) is feasible but it's not something most people are going to have a good intuition on with respect to where the sweet spot is going to be.
- CyberDildonics 3y ago
  The average person's intuition and 'mysterious' are two different things. One is someone with no knowledge assuming the wrong thing, the other is experts not able to figure something out.
- jacquesm 3y ago
  The air near the top is 100% trapped, there is no way for it to escape and it's the hottest air under the panel. Overlap with the cells is anywhere from 1/2" to 1.5" so that's a sizeable fraction of the cells. Probably close to 25 to 30% or so.

aqme28 3y ago

Wow, I was just talking to my dad about this. He runs a startup that builds PV-embedded vertical masonry[1], and they have been getting significantly higher-than-expected yield on their installations. Though in their case they were mostly theorizing ground reflections [1]: (https://www.solablock.com/ https://www.solablock.com/, looking for investors!)

taneq 3y ago
Are the PV panels mounted directly on the masonry? ...oh wait clicks link yeah maybe the masonry is acting as a heatsink for the panels as well?
- aqme28 3y ago
  They're embedded in the masonry. When you buy a CMU, you get one unit. Yes, this has better thermal properties, and this also makes them more durable and theft/vandal resistant.
wongarsu 3y ago
That's a cool project. One advantage solar masonry might have is the high thermal mass of masonry. The bricks average out day and night temperatures, and probably keep the panels a lot colder than they would be on their own.
- jacquesm 3y ago
  And as an extra bonus they slow the heat exchange with the outside air so it works as insulation both in summer and in winter.
- Workaccount2 3y ago
  If anything I would think that the poor thermal conductance of the masonry would make this inferior to simply mounting panels over the exterior with an air gap.
  - deleted 3y ago

lostmsu 3y ago

So probably adding active cooling (e.g. fan) to existing installations would help even more.

Aspos 3y ago
A wind catcher turbine of some sort?
fnordpiglet 3y ago
This was exactly my question, have people looked at the various thermal management techniques used in computing? Heat pipes on the backplane and fan cooled heat sink blocks could go a long way.

DemocracyFTW2 3y ago

Spoiler: vertical panels can rid themselves of excess heat more efficiently, thus operating temperatures are lower and, hence, output better. Vertical panels will also be more susceptible to damage from high winds but less susceptible to precipitation of water and dust, so my guess would be that the fixed slant orientation for PV panels in temperate latitudes will stay with us irrespective. I'm starting to think about having water pipes running along the backsides of the panels to cool them and obtain warm or hot water...

estiaan 3y ago
I’ve seen people cooling solar panels by using coreflute/Fluteboard at the back of a panel and circulating pool water through the channels. I think I saw this on Linus Tech Tips weirdly enough, not sure though

1970-01-01 3y ago

IIRC, there was a boy that did a similar experiment and was lambasted for measuring voltage instead of power: https://www.zdnet.com/article/why-13-year-olds-solar-power-breakthrough-wont-work/ https://www.zdnet.com/article/why-13-year-olds-solar-power-b... https://web.archive.org/web/20160308193750/http://www.wsj.com/articles/SB10001424052970203550304577138511287470508 https://web.archive.org/web/20160308193750/http://www.wsj.co...

maxglute 3y ago

This seems like something that should have been verified in lab/field decades ago, before billions in mass solar roll out. I'm assuming it is and large scale solar infra are optimized according to site conditions?

heavenlyblue 3y ago
The markets stay irrational longer than you can stay solvent

mrbgty 3y ago

Curious why they don't seem to be stacking them up or making them taller? Wind? Shade? If they were on a pole allowing the wind to turn them, could you get both wind and solar power at the same time?

hankman86 3y ago

Here in Australia, News Corp (owned by the same Murdoch family who is also behind Fox News) is currently running a campaign against agricultural solar. A key “argument” being that installing solar panels on fields makes it impossible to grow crops there.

estiaan 3y ago
I live in Aus as well, and I don’t expose myself to News Corp at all. Can you explain to me what the heck the issue is? We have so much space and we don’t need that much more solar, how is anyone’s crops at risk? Is this just a complete non issue? Like i agree that solar panels shouldn’t be installed over the top of crops but is that even a thing that is happening? Don’t the farmers have almost complete control of what goes on their property anyway? So confused
- triceratops 3y ago
  News Corp is anti-renewable energy. No need to look for a deeper explanation than that.