7 ms·

I'm not sure I like this. It seems that we're very clearly in the area of diminishing returns when it comes to solar panels. https://upload.wikimedia.org/wikip

I'm not sure I like this. It seems that we're very clearly in the area of diminishing returns when it comes to solar panels. https://upload.wikimedia.org/wikipedia/commons/4/42/Efficiency_chart_rev_05-2012.png https://upload.wikimedia.org/wikipedia/commons/4/42/Efficien... The conclusion of that chart seems to be : concentrated solar power (even on small scale) is unbeatable, and tops out (realistically) at ~40% efficiency. So now we should probably work on very, very cheap lenses if we want to advance solar panels, and quick ways to make small, very cheap panels.

deleted 10y ago
[deleted]
Arnt 10y ago
Why? AFAICT, there are three ways to double the output of a solar cell: Double the area, double the efficiency, and move the cell to somewhere with twice as bright sunlight and install a cable. That one option presents intractable problems doesn't seem to matter very much when either of the two others are available.
- Tharkun 10y ago
  I suppose it's a matter of cost, which will likely depend on location. Cheap lenses might be more feasible in densely populated areas. A big, fat, copper cable attached to very large and very cheap panels will likely be more cost effective in sparsely populated areas.
  - dotancohen 10y ago
    Cheap lenses won't work for solar panels on a car, boat, or other vehicle.
    - Tharkun 10y ago
      Can you elaborate on that?
      - Arnt 10y ago
        I presume he means that cheap lenses will not be able to deal with a moving vehicle's quick changes of orientation.
- petra 10y ago
  Area isn't unlimited in the residential market, place is fixed and installation is expensive.
  - taneq 10y ago
    That's why you need to install the cable.
  - Arnt 10y ago
    Those are places where people buy their vegetables instead of growing them.
- contravariant 10y ago
  Well, really there are only two, capturing more sunlight, or capturing sunlight more efficiently. Since we need sunlight for other things as well it's better if we don't waste it, but right now that doesn't really seem to be a limiting factor (there are still plenty of roofs without solar panels).
danmaz74 10y ago
I don't know if we're already at diminishing returns, but to estimate that you need to compute the economic returns, not just the conversion efficiency. As yearly production escalates, even small increases to the "conversion efficiency"/"production cost" can yield high total returns on the investment.
- jacquesm 10y ago
  > As yearly production escalates, even small increases to the "conversion efficiency"/"production cost" can yield high total returns on the investment. It won't matter. Investment is hardly ever looked at in terms of total returns but only in terms of annual ROI as a percentage of the original outlay.
  - danmaz74 10y ago
    By "total" returns I didn't mean "lifetime" returns, but returns on the whole production to which the new technology can be applied (be it yearly, monthly, or whatever). My point is that, if we're building (or upgrading) bigger and bigger production plants, even a small improvement to the process can bring in big annual ROI.
lovemenot 10y ago
Cheap lenses can provide far less concentrated light than similarly cheap mirrors, since the latter are not constrained by having to sit atop a solar cell. As long as space is not a major constraint, controllable mirrors in array should handsomely beat lenses.
Tuna-Fish 10y ago
This is the current version of that chart: https://www.nrel.gov/pv/assets/images/efficiency-chart.png https://www.nrel.gov/pv/assets/images/efficiency-chart.png This cell is the blue dot "Kaneka". Multijunction cells are very expensive to make. The reason the multijunction cells in that chart all have concentrators is that without them, the cost is ridiculously too much to even consider. This particular cell is noteworthy because it is cheap enough that you can eschew the added cost and complexity of the concentrator and just use more cells and potentially still be cheaper.
- jacquesm 10y ago
  > potentially That's the operative word here. And that is far from a run race with this particular technology, it is going to be close enough that it bears watching but not so good that it is a slam dunk winner.
  - nojvek 10y ago
    To be honest it's a lot more economical to have cheap large mirrors on your roof directing sunlight towards a concentrated spot of PV cells of higher efficiency that are somewhat expensive. You could use some of that energy to have tiny motors that track the sunlight. This would net in more energy and less cost per square meter right?
    - jacquesm 10y ago
      I've done a lot of experimenting with that. Here are some of the (surprising!) results: - you only need one motor to aim a whole array of mirrors if you're willing to make some exotic gears - the lifespan of the cells will shorten measurably - you will need to cool the cells if you don't want them to die very quickly - there will be a serious fire risk
      - ballenf 10y ago
        Are there cells designed for higher intensity than others -- ones that can handle the extra light and maintain efficiency?
petra 10y ago
Insolight is a startup commercializing cheap plastic lens, that both focus and track the sun(hard to do with fixed lens, requires some optics magic). Panels made from those will have 36.5% efficiency, with only a 30% increase in total installation costs - that's their goal at launch.
Brakenshire 10y ago
> I'm not sure I like this. It seems that we're very clearly in the area of diminishing returns when it comes to solar panels. I don't follow this argument. The median panels used in actual installations have increased in efficiency from about 16% to about 18% over the last 10 years (while the prices have more than halved). First, the chart you link to is for 'hero' cells, using expensive technology to test the limits of a particular material, it is only tenuously linked to industrial production. There's lots of leeway for improvement in industrial production, which is what matters to the economy. Second, improvements in efficiency are only one part of cost reductions. In the time that the cost of panels has dropped perhaps 50 fold you're only talking about a 1/3 to 1/2 increase in efficiency. Third, there's always potential for other materials or structures to come to the fore. If we could find a cheap way of producing multi-junction cells then the ~30% theoretical efficiency limit disappears. So, there's plenty of scope for continued improvements.
- londons_explore 10y ago
  > If we could find a cheap way of producing multi-junction cells I really don't see why this is impossible. Hire a bunch of specialists, make robots build the cells end to end, then build a bunch of those robots. Anything a human can make one of, it should be possible to make a robot build millions of with zero incremental human labour, as long as you invest enough upfront for the robots.
mangecoeur 10y ago
A fundamental limitation of concentrating systems is they only work well with direct solar irradiance - it's very hard to concentrate diffuse solar rays coming from random directions, as you have on any overcast day. This dramatically reduces the potential generated power in locations that don't have consistently clear skys (i.e. most places). So a high efficiency flat panel with a promising route to commercialization and built by a reputable company is a great step.
- jacquesm 10y ago
  > A fundamental limitation of concentrating systems is they only work well with direct solar irradiance - it's very hard to concentrate diffuse solar rays coming from random directions, as you have on any overcast day. It's impossible. That said, every type of solar panel works best with direct solar irradiance, what you can get from scatter off clouds and on overcast days is a pittance even in the best situations compared with direct light. So this isn't nearly as big a step (yet) as it is made out to be, it may work out commercially but that is definitely not clear at this moment, and if it does work out commercially then it remains to be seen how much of that efficiency gain ends up reducing the per KWh installed cost of the panels. Any net gain of course is good.
averagewall 10y ago
Efficiency isn't quite the important thing for solar as it is for fuel burning engines since all the sunlight is used up at the same rate no matter how much power you capture from it. We could get much cheaper panels with no better efficiency and that would still be excellent. More important than energy efficiency is price per unit energy. You could have an inefficient but cheap solar cell that's more economical than an expensive efficient one (eg. active tracker vs fixed - the less efficient option is usually more economical). Though when installation costs dominate, then you really do want smaller panels so you can spend fewer man-hours nailing them up.
_rpd 10y ago
Isn't the conversion efficiency basically irrelevant except for specialized applications like spaceflight where every gram counts? 8% thin film solar cells will be the market winner if their marketplace ROI is superior - $ per Watt and lifetime.
- the8472 10y ago
  If installation costs per m² dominate because moderately-efficient panels already are dirt-cheap then using a more efficient panels that are a bit more expensive can save overall costs if you can get the same power with fewer m² and thus lower overall costs. And even if you drive down installation costs so you can roll out cheap cells en masse you'll eventually run into a space limit for some applications. There's only so much sun-facing rooftop on each building.
pjc50 10y ago
Aren't we at the stage where "balance of system" costs are starting to dominate: wiring, mountings, inverters, installation labour and so on? Or is that only true for house-scale systems?
JoeAltmaier 10y ago
Or very, very large arrays in space!

deleted 10y ago

[deleted]

Arnt 10y ago

Why? AFAICT, there are three ways to double the output of a solar cell: Double the area, double the efficiency, and move the cell to somewhere with twice as bright sunlight and install a cable. That one option presents intractable problems doesn't seem to matter very much when either of the two others are available.

Tharkun 10y ago
I suppose it's a matter of cost, which will likely depend on location. Cheap lenses might be more feasible in densely populated areas. A big, fat, copper cable attached to very large and very cheap panels will likely be more cost effective in sparsely populated areas.
- dotancohen 10y ago
  Cheap lenses won't work for solar panels on a car, boat, or other vehicle.
  - Tharkun 10y ago
    Can you elaborate on that?
    - Arnt 10y ago
      I presume he means that cheap lenses will not be able to deal with a moving vehicle's quick changes of orientation.
petra 10y ago
Area isn't unlimited in the residential market, place is fixed and installation is expensive.
- taneq 10y ago
  That's why you need to install the cable.
- Arnt 10y ago
  Those are places where people buy their vegetables instead of growing them.
contravariant 10y ago
Well, really there are only two, capturing more sunlight, or capturing sunlight more efficiently. Since we need sunlight for other things as well it's better if we don't waste it, but right now that doesn't really seem to be a limiting factor (there are still plenty of roofs without solar panels).

danmaz74 10y ago

I don't know if we're already at diminishing returns, but to estimate that you need to compute the economic returns, not just the conversion efficiency. As yearly production escalates, even small increases to the "conversion efficiency"/"production cost" can yield high total returns on the investment.

jacquesm 10y ago
> As yearly production escalates, even small increases to the "conversion efficiency"/"production cost" can yield high total returns on the investment. It won't matter. Investment is hardly ever looked at in terms of total returns but only in terms of annual ROI as a percentage of the original outlay.
- danmaz74 10y ago
  By "total" returns I didn't mean "lifetime" returns, but returns on the whole production to which the new technology can be applied (be it yearly, monthly, or whatever). My point is that, if we're building (or upgrading) bigger and bigger production plants, even a small improvement to the process can bring in big annual ROI.

lovemenot 10y ago

Cheap lenses can provide far less concentrated light than similarly cheap mirrors, since the latter are not constrained by having to sit atop a solar cell. As long as space is not a major constraint, controllable mirrors in array should handsomely beat lenses.

Tuna-Fish 10y ago

This is the current version of that chart: https://www.nrel.gov/pv/assets/images/efficiency-chart.png https://www.nrel.gov/pv/assets/images/efficiency-chart.png This cell is the blue dot "Kaneka". Multijunction cells are very expensive to make. The reason the multijunction cells in that chart all have concentrators is that without them, the cost is ridiculously too much to even consider. This particular cell is noteworthy because it is cheap enough that you can eschew the added cost and complexity of the concentrator and just use more cells and potentially still be cheaper.

jacquesm 10y ago
> potentially That's the operative word here. And that is far from a run race with this particular technology, it is going to be close enough that it bears watching but not so good that it is a slam dunk winner.
- nojvek 10y ago
  To be honest it's a lot more economical to have cheap large mirrors on your roof directing sunlight towards a concentrated spot of PV cells of higher efficiency that are somewhat expensive. You could use some of that energy to have tiny motors that track the sunlight. This would net in more energy and less cost per square meter right?
  - jacquesm 10y ago
    I've done a lot of experimenting with that. Here are some of the (surprising!) results: - you only need one motor to aim a whole array of mirrors if you're willing to make some exotic gears - the lifespan of the cells will shorten measurably - you will need to cool the cells if you don't want them to die very quickly - there will be a serious fire risk
    - ballenf 10y ago
      Are there cells designed for higher intensity than others -- ones that can handle the extra light and maintain efficiency?

petra 10y ago

Insolight is a startup commercializing cheap plastic lens, that both focus and track the sun(hard to do with fixed lens, requires some optics magic). Panels made from those will have 36.5% efficiency, with only a 30% increase in total installation costs - that's their goal at launch.

Brakenshire 10y ago

> I'm not sure I like this. It seems that we're very clearly in the area of diminishing returns when it comes to solar panels. I don't follow this argument. The median panels used in actual installations have increased in efficiency from about 16% to about 18% over the last 10 years (while the prices have more than halved). First, the chart you link to is for 'hero' cells, using expensive technology to test the limits of a particular material, it is only tenuously linked to industrial production. There's lots of leeway for improvement in industrial production, which is what matters to the economy. Second, improvements in efficiency are only one part of cost reductions. In the time that the cost of panels has dropped perhaps 50 fold you're only talking about a 1/3 to 1/2 increase in efficiency. Third, there's always potential for other materials or structures to come to the fore. If we could find a cheap way of producing multi-junction cells then the ~30% theoretical efficiency limit disappears. So, there's plenty of scope for continued improvements.

londons_explore 10y ago
> If we could find a cheap way of producing multi-junction cells I really don't see why this is impossible. Hire a bunch of specialists, make robots build the cells end to end, then build a bunch of those robots. Anything a human can make one of, it should be possible to make a robot build millions of with zero incremental human labour, as long as you invest enough upfront for the robots.

mangecoeur 10y ago

A fundamental limitation of concentrating systems is they only work well with direct solar irradiance - it's very hard to concentrate diffuse solar rays coming from random directions, as you have on any overcast day. This dramatically reduces the potential generated power in locations that don't have consistently clear skys (i.e. most places). So a high efficiency flat panel with a promising route to commercialization and built by a reputable company is a great step.

jacquesm 10y ago
> A fundamental limitation of concentrating systems is they only work well with direct solar irradiance - it's very hard to concentrate diffuse solar rays coming from random directions, as you have on any overcast day. It's impossible. That said, every type of solar panel works best with direct solar irradiance, what you can get from scatter off clouds and on overcast days is a pittance even in the best situations compared with direct light. So this isn't nearly as big a step (yet) as it is made out to be, it may work out commercially but that is definitely not clear at this moment, and if it does work out commercially then it remains to be seen how much of that efficiency gain ends up reducing the per KWh installed cost of the panels. Any net gain of course is good.

averagewall 10y ago

Efficiency isn't quite the important thing for solar as it is for fuel burning engines since all the sunlight is used up at the same rate no matter how much power you capture from it. We could get much cheaper panels with no better efficiency and that would still be excellent. More important than energy efficiency is price per unit energy. You could have an inefficient but cheap solar cell that's more economical than an expensive efficient one (eg. active tracker vs fixed - the less efficient option is usually more economical). Though when installation costs dominate, then you really do want smaller panels so you can spend fewer man-hours nailing them up.

_rpd 10y ago

Isn't the conversion efficiency basically irrelevant except for specialized applications like spaceflight where every gram counts? 8% thin film solar cells will be the market winner if their marketplace ROI is superior - $ per Watt and lifetime.

the8472 10y ago
If installation costs per m² dominate because moderately-efficient panels already are dirt-cheap then using a more efficient panels that are a bit more expensive can save overall costs if you can get the same power with fewer m² and thus lower overall costs. And even if you drive down installation costs so you can roll out cheap cells en masse you'll eventually run into a space limit for some applications. There's only so much sun-facing rooftop on each building.

pjc50 10y ago

Aren't we at the stage where "balance of system" costs are starting to dominate: wiring, mountings, inverters, installation labour and so on? Or is that only true for house-scale systems?

JoeAltmaier 10y ago

Or very, very large arrays in space!