New concentrator could help solar panels capture more sunlight without tracking | Hacker News Reader

New concentrator could help solar panels capture more sunlight without tracking

cosmosmagazine.com

73 pointssohkamyung40 comments

I get the feeling that generating (say) 10% more power by adding these fancy bits of optics to a set of solar cells would cost far more than (getting the same improvement by) installing 10% more optics-free solar cells.

> 10% more power by adding these fancy bits of optics to a set of solar cells would cost far more than (getting the same improvement by) installing 10% more optics-free solar cells

Surely if you're comparing against fixed solar panels, then it would be more than 10%? For tracked solar panels, costlier installation and maintenance would be traded off with efficiency of the prismatic optics and degradation of materials. Economies of scale might favor the optics if it's cheap enough to manufacture (less components, cheap materials etc.)

If the new optics give X% more power, they compete against "just buy X% more solar panels". (My original "(say)", in front of the "10%", was meant to indicate that the number was arbitrary.)

> Economies of scale might favor the optics if it's cheap enough...

- Quite true. But note that the article describes the inventor of the new optical system as "assistant professor in astronautics and spacecraft engineering". That certainly suggests cost-insensitive, performance-critical applications - such as cubesats.

You're probably right. Given they seem to be using glass, I'd say it's both too heavy for space (?), and too costly for earth. I guess I'm hoping they take this technique to cheaper easier materials so I can slap this on top of a van and get decent power in a variety of different conditions.

Agreed. Unless you have serious space constraints, more cheap panels which last decades is far cheaper and less maintenance than any solar concentrators or solar tracking that will fail long before the panels. I could see those technologies being useful on a trailer for generating power in remote locations, but not for the typical home or solar farm. I'd imagine those lenses would amplify the shading caused by typical dirt and debris, requiring more labor costs.

The other thing is that solar concentrators burn the cells out quicker, it isn't magic free energy. Spending a significant amount more money just to squeeze out more power from the cells doesn't make sense for all applications.

  > solar concentrators burn the cells out quicker

Do you have a source that I could reference for that? Thank you.

https://en.wikipedia.org/wiki/Solar_cell#Disposal

Concentrators are actively trying to put more of the suns energy (an thus UV degradation) on the cells than can be achieved by simply aiming the cell at the sun. It greatly depends on the type of cell being used, with many technologies having a shorter lifespan than polycrystalline and monocrystalline cells, but they don't last forever out in the sun. A panel boxed up in a warehouse isn't likely to have discernible cell degradation in 10 years. A panel flat on a roof having off-axis light will degrade more, one on a solar tracker will degrade more still, with the benefit of more power per unit time during that shortened lifespan. Add in concentrators and it will degrade more still. Much like anything else. I'm getting no sun indoors, get more standing in my yard, get even more standing near water where it reflects back at me and get sunburn (degradation) quicker in that environment.

Obviously it makes sense to aim the panels at the sun, and having a method to seasonally adjust the tilt can be done for very cheap. It can be made to last the life of the panels without repair, and it isn't an outrageous loss of performance if it was forgotten for a few weeks. Active sun trackers can potentially cost more than the panel itself, even more so when factoring in installation and setup. If it fails aiming to one extreme, there will be a substantial loss in power even compared to a panel with a fixed mount. That failure is likely to happen more than a couple times in the life of the panel, unless you replace parts before failure (even more cost), or add concentrators (more cost) to increase output and decrease panel life (more cost yet again). Unless there is a specific reason for all of that cost and complexity, such as space constraints or other factors, then it is cheaper to just lay out more panels. If a new technology comes out where they can stop UV degradation without a large impact on power output, or weight, or cost, then I'll be interested. For my use case I'd rather reduce my energy usage and lay panels in the sun with seasonal cleaning and adjustment.

Thank you very much.

I also opted to just add more panels. There is a finite amount of sunlight hitting my roof, the only advantage to tilting the panels are easier cleaning and passage. If I could tilt a single large panel at x degrees then I could absorb cos(x) more sunlight but the thing would stand up above my roof to a height of sin(x)*roofLength and would blow over in the wind.

There is (was?) a company that made terra cotta tile shaped concentrators that were laid on top of solar panels. They claimed this used something like 30% less PV panels for the same output, and that, because the panels were shielded from UV / precipitation, increased the usable lifespan by a decade or so.

I think they went under back when Tesla was false-advertising their roof prices to suppress competition in the market, but I’d love to be proven wrong.

Always been the main problem with concentrated solar.

It's the right mindset. Cheap panels that can be mass manufactured and installed in places where there is plenty of room to do that are a great way to delivering lots of power cheaply.

The economic efficiency of the panels is function of how many square meters they take, how expensive those square meters are, how costly it is to maintain and service the setup, how long they last, and how expensive it is to buy and install them, etc. It's not just about the watt/square meter.

Less moving parts means less complexity, less things that can break, and overall lower cost. 10% more power at 2x the cost is a net negative.

There are probably applications where 10% more power at 2x the cost make sense, like on a satellite or a solar powered aircraft, maybe.

How much more mass, though? Mass is likely to be at a premium anywhere you can't just also slap down a few more cheap cells, e.g. where there's not much space.

Good points by you and your sibling poster. Maybe this tech really would have a hard time finding a niche when considering mass along with cost/performance characteristics, given other premium or economic options. Maybe on the roof of an expensive high rise it would make sense? On boats? Hard to say.

Indeed, though there are other places of the design space to look. For example in satellites, triple junction cells (generating power from additional parts of the spectrum) are worth the much higher cost as they weigh the same as standard cells, thus generating more power without increasing launch cost.

In terms of total kWh per year cheap panels win. In terms of the value per year morning and evening power is becoming increasingly valuable due to the duck curve. Tracking solar panels still aren’t viable, but large instillations will sometimes aim a percentage of panels to the east or west to shift power at the cost of total kWh per year maximize value produced.

So, 20% more cost for 10% more power could be worth it even outside of space constrained applications.

Cheap panels’ output drops as temperature goes up.

I hadn’t thought of it until just now, but that should flatten the duck curve.

Another way to flatten the duck curve is to buy smaller inverters and more panels.

I'm not sure I understand your statement that tracking solar panels aren't viable. The vast majority of utility scale solar PV installations in the United States use single axis tracking systems. These orient the modules on a north south axis, which then tilts from east to west throughout the day. Energy capture over an equivalent optimized fixed-tilt system is significant. The land area required is larger, however.

Most smaller or behind the meter systems such as carports or rooftop mount solar use fixed tilt, and fixed tilt is also used in certain types of terrain or where costs for tracking are prohibitive.

Yes single axis tracking are common, but dual axis racking isn’t.

Horizontal Single-Axis Solar Tracker’s are normally aligned north south, but shifting slightly off axis from pure north vs south can increase output in the morning or evening.

Tilted Single-Axis Solar Tracker’s are closer to the performance of dual Axis trackers, but have a similar question do you pick a tilt angle to maximize annual, summer, or winter output.

The duck curve is heavily misunderstood.

The repositioning of panels to capture more morning and evening light is a real thing. At the theoretical extreme it can make the PV output a square wave.

But, that actually makes the duck curve worse, since the duck curve is about the gradient of that switchover.

But the duck curve has never really been an actual problem so it's kind of academic. And if it was we have solutions to it.

The gradient is one issue, the other is sending wholesale prices to zero for extended periods most days. That messes with the economy of baseline power generation especially nuclear.

Yes, I suppose cheap energy can be seen as a problem if you're an energy seller, not a buyer or user.

Buyers will eventually face a related issue.

To simplify if nuclear/geothermal or whatever was 10c/kWh if sold 24/7 but if wholesale prices are 1c for 8 hours a day then base load generation needs to make up 8x9c = 72c over the other 16 hours. Now prices would hypothetically jump from 10c for those 16 hours to 14.5c for those 16 hours.

It should still be a net savings for the average consumer, but if your business model is based on cheap electricity at 10am to 4am that might flip to 10am to 4pm.

As an idea, if a ship were to be electric with battery + solar as the energy source... the ship would be space constrained and obtaining more power with reduced mechanical complexity may be worth it in such industrial settings.

Unsure if this is what they're going for, but my initial question to myself was "Where does this make sense?" for the same reason you've highlighted.

Agreed. People somehow miss this point when discussing space based solar arrays that beam power back to Earth.

Is beaming power through atmosphere even feasible? If it is feasible, why aren't we beaming power at least across sea like Mediterranean for example, where laying cable will be expensive. I always thought space beaming power is just science fiction thing.

Straight down from space is more feasible than through the atmosphere over the horizon.

From what I can tell, space solar power would be competitive in those places where the alternative is to fly in fuel for generators. For example military forward operating bases, isolated Northern communities, et cetera.

I think the atmospheric attenuation problems for a horizontal path are much worse than vertical, not to mention the horizon which would mean many relay stations along a surface path to bend the beam along the curved surface.

However, a bigger problem or question to me is what wavelengths can carry useful amounts of energy and be kept in a narrow beam to have high transmission and conversion efficiency from source to collector. Everything from microwaves up to visible light is going to be quite susceptible to atmospheric moisture. Even microwave and infrared communication links can suffer with rain, clouds, or fog.

If you can get down to radio frequencies, I don't know whether a narrow beam is really possible. I've seen some hints at the development of rasers (coherent, stimluated emission like lasers and masers but down into "radio" frequencies). But I am not a physicist and do not really understand how such an emission would behave. Could a useful amount of energy be targeted on a "small" receiving antenna without leaking out to other accidental recipients...?

Also, for power levels useful to the utility grid, any beam alignment or scattering errors would mean extremely lethal and destructive energy going off-target. Straight down from space, you might delineate a concentric safety exclusion zone around and above a ground station. If beaming horizontally, wouldn't you have to exclude a large wedge of ground and a huge conical section of airspace both before and after the ground site?

It might be interesting for rooftop solar where space is limited and installation costs make up a large part of the expense.

It’s likely going to make your roof much heavier though, being made of glass. And that’s usually a bad thing.

So unless they find a different lighter material with which they can create the same kind of lens, it probably won’t be suitable for many kinds of roofs.

I don't know where you live, or what your roofs are made of. But the 1.6m x 1m panels we have weigh only 20KG.

That's much lighter than the tiles they replaced.

Wouldn't the voids allow active cooling / water heating at the same time?

If so that certainly increases the utility in a domestic setting at least.

If this reasoning was correct, the same would surely apply to tracking solar panels, no? Yet tracking solar panels are all over the place.

As the concept was presented originally in 2015 [1], and based on the fabrication portion, the authors seemingly spent 7 years to get to this point [2]. If in 10 years we are still using multi-junction, rare earth metal based panels, as an optimistic outlook on this work, solar panels could potentially reduce the amount of rare earth/minable materials required and instead use larger areas of solar concentration.

[1] https://ur.booksc.me/book/55710391/7ba74d [2] https://www.nature.com/articles/s41378-022-00377-z#Sec6

Cool. Imagine when it can be installed on existing panels.

I have a 5.5 kW panel system that gets me around 30kwh daily in summers which is probably the best l can get on a stationary roof east facing.

They did not give any specifics as to the improvement in efficiency, is it 10%?

Isn't large portion of the tracking aspect simple geometry and decrease in cross section are based on sin(angle)? No kind of concentrator can solve this limitation without also increasing dimensions and spacing requirements between panels. Are there any other significant effects causing decresase in solar energy conversion in addition to the losses caused by sin(angle) decrease in cross section area? Something like decrease in light to energy conversion efficiency when light density is bellow certain threshold or increased amount of reflected light based on angle ?

This was my reading of it. The win is that you get to reduce the amount of PV and replace it with cheap glass. I might have missed something though...

And how do you clean these optics?

Do they still provide 110% optical efficiency while dirty? Or damaged/scratched from frequent removal/reinstall for cleaning?

I wonder how well an inverted pyramid of these optics would perform in a solar thermal application.

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