[HN Gopher] Researchers shed light on higher energy yields in ve...
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Researchers shed light on higher energy yields in vertical PV
systems
Author : perfunctory
Score : 53 points
Date : 2024-02-09 13:19 UTC (9 hours ago)
(HTM) web link (www.pv-magazine.com)
(TXT) w3m dump (www.pv-magazine.com)
| stephen_g wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| > 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 wrote:
| 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.
| jvanderbot wrote:
| Today you're one of the 10,000! https://xkcd.com/1053/
| whycome wrote:
| 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 wrote:
| Yeah, it's a real (A)GKDM.
|
| (A "(possibly accidental) gatekeeping dick move" :P )
| exabrial wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| Or pipes of cold water running under the panel to generate
| heat for showering
| HPsquared wrote:
| Combined heat and power!
| bloomingeek wrote:
| 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 wrote:
| Don't let perfect be the enemy of good, solar already
| makes a lot of sense and is good for the environment.
| jonhohle wrote:
| CoolPV is a system like this for heating pools.
| defrost wrote:
| and reduced evaporation of water storage.
|
| This already being done on dams in the UK and Spain (or was
| it Portugal? Maybe both.)
| cmrdporcupine wrote:
| Or building solar farms in places that have cold winters and
| cool summers, but lots of sun? e.g. the great plains of North
| America.
| woleium wrote:
| i imagine the 2% benefits will be outweighed by the energy
| distribution cost. even at very high voltage those wires
| are resistors
| wongarsu wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| > 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.
| jacquesm wrote:
| 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.
| CyberDildonics wrote:
| 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.
| schiffern wrote:
| The cited "digital twin" software[0] doesn't model convection
| (it just uses wind speed and an empirical factor), which is
| why it gives a higher predicted temperature than the physical
| model.
|
| [0] https://www.sciencedirect.com/science/article/pii/S187661
| 021...
| dboreham wrote:
| If you run PV/battery systems you pretty soon notice that in
| extreme cold events the controller can shut down charging
| because panel output becomes so high that the batteries will
| be overcharged.
| jacquesm wrote:
| The panels themselves are usually made from aluminum U profile
| and close to the edge there is a substantial amount of trapped
| air if the panel is at a bad angle. Given that most panels are
| at a bad angle this will cause the top edge cells to all be
| over temp and since they're all in series that drops the
| efficiency of the whole panel. So the cross members certainly
| don't help but the panel construction itself could do with some
| more ventilation near the top. I wonder if cutting some slots
| in the top members would drop the cell temperature in a way
| that it would show up on a measurement, this is pretty easy to
| test.
| madaxe_again wrote:
| Indeed - I saw the title and thought "because convection" - I
| actually reinstalled my PV array last year with exactly this in
| mind, as while it was at an optimal angle for insolation, I was
| finding that yield was being hampered by them getting
| devilishly hot - the summer before last, when we hit 47C air,
| really underlined the issue, as the panels were getting up to
| over 85C.
|
| The increase in yield from going near vertical (80 degrees was
| the best I could achieve using existing mounting gear), has
| been about 20% - I say about as I haven't done a scientific
| study of it, just looking at year on year comparisons for
| cloudless days, and the panels are 60 C cooler, which is far
| better than I had hoped for.
| schiffern wrote:
| Yes my first thoughts too.
|
| "Oh, it's convection."
|
| "Hey, I wonder what the best _in-between_ angle is, balancing
| both temperature and cosine loss. "
| myself248 wrote:
| So, a lot of the recent attention is on bifacial east-west
| arrays because they produce a complementary duck curve
| throughout the day. In that case, pure vertical makes
| sense, and production just takes a dip at local solar noon
| and recovers soon after.
|
| But for traditional south-facing panels, I'd argue that
| straight vertical is still optimal, at least for higher
| latitudes. Vertical panels are extremely good at shedding
| snow. They produce more in winter when you need every watt
| you can get, and less in summer when the sun is high in the
| sky and you don't need all that extra power anyway. As soon
| as you tilt the panels to minimize cosine loss, you open
| yourself up to snow buildup which can dwarf any cosine
| gains.
| beAbU wrote:
| Did you factor in possibly improving the incident angle of
| the sunlight? Solar benefits massively the more perpendicular
| the incoming sunlight is.
| vosper wrote:
| I'm hoping to get solar on my next house, which we're designing
| now. Is there a way to install roof panels that improves
| convection / reduces temperatures, like using a different
| mounting system, if that's a thing?
| beAbU wrote:
| Buy 2x extra panels. Honeslty the gains you might get by
| optimising panel placement (beyond matching to your
| hemisphere and latitude) will be outweighed by the additional
| cost. Domestic applications is not big enough to really give
| you significant gains in this department.
|
| Make sure they face the right way (south for Northern
| hemisphere), and match the angle with your latitude. If you
| have a pitched roof thats +-10 deg in the correct angle, just
| lay them flat on the roof.
|
| Edit: forgot to add, a while back there was an article here
| about a company that proved it was viable to lay the panels
| flat on the ground for massive solar farm installations. The
| savings from less installation labour and materials went to
| installing more panels. And they still came out ahead. Solar
| is getting cheap enough that the math gets weird. Your answer
| is almost always "just add more panels" unless you are
| seriously space constrained.
| vosper wrote:
| Thanks, that makes sense.
|
| I don't know anything about rooftop solar mounting systems,
| I will show my ignorance here: I was imagining that perhaps
| you could attach the panels to rails running vertically
| rather than horizontally, to allow for convection airflow
| below the panels.
|
| Or if the rails are horizontal perhaps they have holes in
| them to allow some airflow.
|
| I'm sure this has been thought of and doesn't work some
| obvious reason I just don't know about.
|
| Edit: As I expected, this has been thought of:
| https://solarstone.com/blog/natural-ventilation-and-
| effect-o...
| sbierwagen wrote:
| Actively cooled panels exist:
| https://hydrosolar.ca/products/ahtech-72sk-hybrid-
| photovolta... The extra cost makes them not worth it, but if
| you wanted the absolute maximum amount of power from a
| limited amount of space, you could do it.
| aqme28 wrote:
| 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/, looking for investors!)
| wongarsu wrote:
| 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 wrote:
| 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 wrote:
| 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.
| aqme28 wrote:
| Doesnt an air gap have an even lower thermal conductivity?
| Conductive heat transfer is usually much higher than
| convective.
| tonyarkles wrote:
| I have so many questions! While digging into the Applications
| section these look like conventionally-sized CMUs, the image on
| the front page looks like panels/blocks that are large enough
| to require a crane to lift? If that's the case, how fragile are
| they?
|
| CMUs and other pre-cast concrete "lego blocks" have intrigued
| me for a long time. These look like they've got more robust
| interlocking features than conventional cinderblocks too? The
| idea of being able to order (even without the solar) say 8'x4'
| pre-cast "CMU-style" walls, have them show up on a flat deck,
| stuff rebar and mortar into ready-made holes, and grout between
| the blocks seems like it could dramatically speed up a lot of
| exterior construction. Being able to get them ready to wire for
| solar is delicious icing on the cake!
| aqme28 wrote:
| They don't need a crane. Maybe a confusing rendering for a
| future idea.
|
| They make tiles and cinderblocks, and yes, they have some
| interlocking features. And yes, the idea is that installation
| will be way easier and cheaper than first building a regular
| wall and then attaching vertical solar to that after the
| fact.
| taneq wrote:
| 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 wrote:
| 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.
| neon_electro wrote:
| Please ask your dad or whoever does the work on that website to
| update the home page so that the content does not do the
| reverse of its "intro animation" just because you scrolled back
| in the direction of the top of the page.
|
| I was more distracted by that behavior and totally failed to
| get any value out of visiting your site.
| lostmsu wrote:
| So probably adding active cooling (e.g. fan) to existing
| installations would help even more.
| Aspos wrote:
| A wind catcher turbine of some sort?
| DemocracyFTW2 wrote:
| 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...
| 1970-01-01 wrote:
| 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-b...
|
| https://web.archive.org/web/20160308193750/http://www.wsj.co...
| maxglute wrote:
| 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?
| mrbgty wrote:
| 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?
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