While we're on the subject of low-tech solar energy, what's the current state of concentrated solar power (CSP)? The US Department of Energy's SunShot initiative continues to invest in both photovoltaics and CSP, such as plants built with parabolic trough collectors. These are mirrors that focus sunlight on a working fluid like water or air, which in turn drives a turbine to generate electric power. One advantage of these systems is the ability to store thermal energy directly in large, relatively cheap batteries for on-demand generation:
Their solution of storing thermal energy in molten salt isn't exactly low-tech, but other CSP systems use cheaper thermal storage materials like sand or basalt, which avoid the geopolitical and environmental problems of lithium extraction. Of course, PV panels can dump power into thermal batteries too. Maybe PV farms with huge thermal batteries of sand or basalt will be the best long-term grid-scale solution.
My understanding is that photovoltaic panels are ultimately cheaper to operate. Cost is driving a lot of decisions in this space. Less moving parts, no plumbing, etc. So, as a means for generating electricity, that just looks like one is clearly better than the other.
For storage, there are many other ways to store energy and that too is driven by cost. Dumping heat into salts, basalt, etc. are all attractive propositions from a material cost point of view. Converting heat back into energy is somewhat inefficient however. But these systems are great for providing long term energy storage for e.g. heating systems needed in the winter.
Of course, winters in Nevada are pretty short and warm. I visited Las Vegas in the middle of the winter once. It was very warm. Reno is a bit colder but also has short winters.
They claim to be deploying a 4MW demonstrator unit sometime this year. As I imagine it, a system like this one could charge smaller (in-home) batteries that provide immediate power on demand. As the batteries begin to drain, the turbine has time to spin up. The chemical batteries act as a buffer for turbine downtime and/or response time. Sort of like a Prius hybrid powertrain. The required chemical battery capacity would be much smaller than, say, a grid-scale lithium ion battery bank.
Concentrated solar power requires a large amount of precision mechanics, with robust supporting structures. Since the support structures are already a large share of the cost of photovoltaic panels, anything that increases its costs has this obvious downside. (And probably will get less and less investment over time. I wouldn't be surprised if heating something with photovoltaic panels and an electric arc isn't already cheaper than CSP.)
We don't need low-tech options. We have all that tech that we can use right now. Instead, the non-viability of all low-tech options is exactly what led us into this grave global warming situation we are.
It's also interesting where we choose to draw the line for what's considered "low-tech." The most common method for producing monocrystalline silicon was invented in 1915, and doesn't produce that much waste or involve exotic materials:
Oh, ok. I don't think PV fare any worse than CSP on that. In fact, CSP needs so many independent engineering domains that it's probably among the worst things you can choose on that metric.
For generating electricity, in dollar terms the Levelized Cost Of Electricity (LCOE) of PV is definitely much less than CSP. I don't know the current numbers, though. However, it is not clear to me if in terms of impact on environment, which technology is better. Even more unclear is if it makes sense (in terms of environmental impact) to scale either of the technologies to double digit percentage of the world's electricity requirements.
However, when I last did the calculations, passive CSP is much better at hot water generation for industrial applications - leather/textile factories need a lot of hot water or steam. CSP can at least cheaply pre-heat if not fully heat or boil the water.
Concentrated solar has some minor applications for high heat needs, but for electricity it is totally superceded by PV.
Once you start storing lower temp heat, not intended to generate electricity, then its totally abstracted from the input, you just use grid electricity which can be solar, wind, nuclear or industrial waste heat and locate them anywhere, not just desert locations.
But more importantly, there are no real geopolitical or environmental problems with lithium. It's abundant and recyclable. We're using it because the alternatives are so bad for the environment. Literally killing people, plus animals and ecosystems.
Or maybe he's smart enough to know that "I got coup'd because I was going to nationalise some industry" was too much of a "dog bites man" story, and that "I got coup'd for EVs" was going to be more viral and therefore draw more global attention.
Just like we talk about "Banana Republics" rather than "Worker Mistreatment Republics".
Maybe it's the people who don't want to pay the market price for things and respect environmental and worker regulations when they can topple democratic governments for less cash that are the real "geopolitical problem" not the lithium and bananas?
I mean what could we possibly do if a country with Lithium jacked the price up? Buy it from all the other countries with the broadly distributed Lithium deposits? Mine it in our own countries which also have Lithium? Then we're back in the problem situation of having to treat the workers like human beings and pay standard market rates.
There are companies, such as Heliogen, that are working on the next generation of CSP with higher temperatures and the use of lower cost thermal storage. It will be interesting to see how their systems work at scale.
The unsolved problem here is that they kill birds in a pretty unpleasant way, setting them on fire. I'm going to ignore utilitarian arguments about what else kills birds, the general public doesn't like the idea of birds being immolated by the fiery rays of the Sun and neither do I.
I don't think it would take many drones to eliminate this, though. Birds don't like coming near drones and when you have a huge tower with oversight of the region you need to protect, finding the birds well before they combust seems tractable.
Much of the historical information in this article comes from the September 1909 issue of Modern Electrics magazine in an article called "Harnessing Sunlight." The HathiTrust has a public scan of it here:
I always enjoy reading this magazine, but always saddened when they (unwittingly?) give support to climate change denier talking points.
It's entirely possible for a tech to be more sustainable than another tech, yet not be perfectly sustainable.
Gas can be better than coal, wind can be better than gas and so on without having to continually harp on the exceptions and edge cases to the point that the truth gets lost.
Solar panels are recyclable and have become much more sustainable over the decades. To say otherwise is absurdly wrong.
edit: they link to one of their own articles about PV sustainability, which contradicts what they said in the preceding paragraph, so it might just be really bad writing:
> Meanwhile, solar cells are becoming more energy efficient, and the same goes for the technology used to manufacture them. For example, the polysilicon content in solar cells -- the most energy-intensive component -- has come down to 5.5-6.0 grams per watt peak (g/wp), a number that will further decrease to 4.5-5.0 g/wp in 2017. [2] Both trends have a positive effect on the sustainability of solar PV systems. According to the latest life cycle analyses, which measure the environmental impact of solar panels from production to decommission, greenhouse gas emissions have come down to around 30 grams of CO2-equivalents per kilwatt-hour of electricity generated (gCO2e/kWh), compared to 40-50 grams of CO2-equivalents ten years ago. [7-11] [12]
The question revolves more around whether they are actually recycled.
From the article:
>Silicon cells can only be recycled by a combination of thermal, chemical, and metallurgical steps. That is an expensive process with an impact on the environment. Although you can find statements claiming that around 10% of solar panels are “recycled", they are more likely to be “downcycled”. The modules are shredded, and the resulting material is used as a filler material in asphalt and cement industries.
They're mostly glass and aluminium which can be and are widely recycled.
Oh no, does that involve thermal steps? It probably involves those suspicious sounding "metallurgical" steps too, what even is that, it sounds positively diabolical.
Wait, chemicals? No one told me they had chemicals in them. I never touch anything with chemicals in it. Totally banned them from my life. They are well known to cause cancer apparently.
>The industry is new and still growing, with researchers examining how to commercialize recycling to economically recover most of the components of a solar panel. Elements of this recycling process can be found in the United States, but it is not yet happening on a large scale.
The question revolves around the existence of suitable recycling plants and whether the capacity of these plants is enough (particuarly in times when a "first generation" of panels is progressively approaching an "end of service life").
> Many of these components can be recycled. Glass composes most of the weight of a solar panel (about 75 percent), and glass recycling is already a well-established industry. Other materials that are easily recyclable include the aluminum frame, copper wire, and plastic junction box.
Which is almost exactly what I said, with a few extra details and less sarcasm about "chemicals'.
There are no doubts that some parts (glass, aluminium) can be recycled.
The BIG doubt is IF they are actually recycled (as in the main article probably largely "downcycled").
As per the EPA site (and also the other thread I linked to), they are NOT recycled (at the moment), or - even if they are - they are not - yet - recycled on a large scale.
Here it is an article by MIT (2021) stating how only about 10% of discarded panels are recycled:
Another alternative to silicon cells that is actively being researched is perovskites:
> Perovskite solar cells hold an advantage over traditional silicon solar cells in the simplicity of their processing and their tolerance to internal defects. Traditional silicon cells require expensive, multi-step processes, conducted at high temperatures (>1000 °C) under high vacuum in special cleanroom facilities. Meanwhile, the hybrid organic-inorganic perovskite material can be manufactured with simpler wet chemistry techniques in a traditional lab environment.
The mentioned advantage seems dubious considering that the only cell type for which that is currently true is those using lead, for which the toxicity issue isn't solved. Trading the complexity of the cleanroom facility for the complexity of lead containment doesn't appear to be a good choice. The tin based cells might look interesting though.
This sounds like too interesting of a story to be hidden for so long. Are there any scholars in this field on Hacker News who can shed some more light on whether this is legit?
The historical account may be accurate. The commentary on present day technology is inaccurate. The article criticizes modern solar technology as toxic and unsustainable.
According to the article, the best iteration of Cove's invention achieved 5% solar-to-electricity conversion using an antimony alloy. Modern silicon solar panels achieve over 20% solar-to-electricity conversion using silicon. Silicon is non-toxic and is more than a million times as abundant in the Earth's crust as antimony [1]. Silicon solar cells do not contain toxic compounds. Modules made with silicon cells may contain toxic compounds if they were older ones manufactured (pre-RoHS) with lead based solder or glass frit containing lead, but the same issue would apply to antimony based solar modules; the cell material is not related to the soldering technology. Every other criticism of silicon given in the article (mining, complex machines, global supply chains, fossil fuels used upstream) would equally apply to a hypothetical antimony-based solar industry of comparable scale.
Low Tech Magazine is a great source for introducing modern audiences to old forgotten technologies. But it has apparently run short of forgotten technologies that may actually be better and has fallen into a rut of exaggerating contemporary-technology drawbacks and minimizing the problems of old technologies.
"Silicon solar cells do not contain toxic compounds. "
This is absolutely untrue. The silicon is just the starting base, you still need to dope the cells, often with an arsenic compound (Indium-Gallium Arsenide, Gallium Arsenide, etc.)
In the EU and California, solar panels are exempt from RoHS requirements.
I used to manufacture solar panels for Sunspark Technology in California. You can't get the same kind of conductivity using tin bus ribbon without sacrificing usable cell area, as you need a wider, flat strip of tin, compared to lead. The newest "invisible bus bar" panels are using silver wire. These cells, when I worked there pre-COVID, were dumping ~11A at full light exposure. The inter-string bus bars were lead-coated copper, as were the string to junction box interconnect ribbons. 60/40 was used in the junction box. We manufactured panels for everyone, including Jinko, that behemoth of a solar corporation.
Solar panels very often have toxic stuff everywhere.
Indium gallium arsenide and gallium arsenide are compound semiconductors that are far too expensive for use in mass market panels. They are used as cells or components of multi-junction cells for satellites and a few other high value applications. Commercial silicon cells are doped with phosphorus and boron or gallium.
On further reading I find that you are correct about RoHS exemptions for lead in solar modules:
Commercial cells doped with boron are meant for use in low-light applications due to higher efficiencies in lower/diffuse light, and are not very suited to direct-sunlight applications due to the tradeoff. Indium and Gallium-doped single-crystal silicon still wins in efficiency. Phosphorous I have not seen in any of the roughly 5 million cells I've handled as part of QC. I've heard of nanoparticles of phosphorous helping perovskite-based cells, but that's about it. I've never handled one in commercial production.
Not saying you're wrong, but here's some of the claims that the article makes about the advantages of antimony Schottky vs n-p silicon solar cells:
> In the 1970s and 1980s, scientists investigated Zn4Sb3 for use in photovoltaics and concluded that the material’s “obvious advantages are apparent simplicity and relatively low temperature of the preparation procedure.” [23] The melting point for Zn4Sb3 is 570 degrees Celsius, while it’s 1,400 degrees for silicon.
> Silicon modules are sandwiched between two laminate encapsulant layers (usually EVA, an ethylene/vinyl acetate copolymer). These layers are essential to ensure module service lifetime. [1-3] To recycle the silicon – the most valuable component of a solar panel – these layers need to be separated, but burning them also destroys the modules. Silicon cells can only be recycled by a combination of thermal, chemical, and metallurgical steps. That is an expensive process with an impact on the environment. [...] In contrast, the solar cells built by George Cove were entirely recyclable. They required no protective layer and did not even contain solder.
> Schottky cells do not require a high-temperature phosphorus-diffusion step, which ordinarily creates the n-layer of the p-n junction in silicon today. This alone reduces the energy input into the solar cell production process by 35%.
... and a point that maybe that efficiency of Schottky cells (irrespective of composition) hasn't really been explored:
> Scientists also reached 17% experimental efficiency for a graphene/silicon Schottky cell, up from 1.5% ten years earlier.
There are a couple of problems with the implications given by the quote
Schottky cells do not require a high-temperature phosphorus-diffusion step, which ordinarily creates the n-layer of the p-n junction in silicon today. This alone reduces the energy input into the solar cell production process by 35%.
Reducing the solar cell energy inputs by 35% is a clear win only if the cell output does not fall commensurately. A record 17% efficiency for a Schottky cell compares to over 24% record efficiency for PERC cells made with conventional high temperature phosphorus diffusion:
"Trina Solar claims record 24.5% efficiency for 210mm PERC cells"
That means that the best Schottky cell generates about 69% as much energy as the best PERC cell while taking about 65% as much energy to manufacture. The Schottky cell generates about 7% more output energy per unit of input energy -- a pretty marginal improvement.
There is a more promising alternative to high temperature diffusion cells already in mass production: the heterojunction solar cell. It was originally commercialized by Sanyo (later acquired by Panasonic) but its patents have recently expired so several manufacturers now make heterojunction devices.
Major solar manufacturer Longi just set a cell efficiency record of 26.5% with a heterojunction design:
Heterojunction cells are processed at low temperature because the delicate amorphous silicon layers cannot withstand high heat:
"Silicon heterojunction (SHJ) solar cells have typically a low process temperature limit (~250°C) because high-temperature annealing processes can degrade the passivation of the hydrogenated amorphous silicon (a-Si:H) due to the hydrogen effusion during the annealing."
Given the combination of low temperature processing and high efficiency found in heterojunction cells, I am personally doubtful that the Schottky barrier cell can offer superior energy return on energy invested for solar power systems.
Just want to reiterate I have no dog in this fight, and thank you for this interesting counterpoint. Probably the one surviving argument of the article is recyclability. I presume multijunction cells are hard to recycle vs something more low tech and maybe hobbyist level approachable (which is the whole shtick of that publication)
You have to wonder if some of these MEG solar designs will ever make it out of the lab. Could they be combined with a Schottky design to increase the receptive wavelength range?
It's clearly trivial (in an industrial sense anyway) to manufacture silicon solar cells, do we care about the melting point, or should we focus on the EROI?
The science is correct. I'm not aware of much application of it commercially as of yet, up until relatively recently the higher efficiency of the silicon PN junction process has made better use of the surface area.
However, a major area of advancement on the horizon is multi-junction panels. These stack different semiconductors which each harness different wavelengths of light to harness more of the sun's relatively wide band of light.
I'm not sure exactly what junction chemistries we'll see in these going forward, but I'm sure the industry will be trying out just about every configuration we can manufacture.
Surprising case of photoshopping explained at the very end. Smithsonian Magazine has the same photo but without the man in it! I can't tell which is the original but one of them is fake!
My vote: both original, but taken several minutes apart. Look at the man's legs. They are blocking some wires and tape - which you can't see at all in the picture with the man. In the picture without the man, the wires and tape were added.
If you photoshopped the man out, you wouldn't also add the wire and tape.
Look at the reflection of the man in the solar panels. The reflection is great - far better than what I would expect from 1905 technology. Also, the caption of that photo says it "contains Mr. Cove", so the photographer included a picture of a human in the picture.
I suppose the original may have included a human, but not that human.
> George Cove did not understand how his solar generator worked, and neither did anyone else at the time. It was only with Einstein’s work on the photoelectric effect (in 1905) and later work in quantum mechanics (1930s and beyond) that the concept of a semiconductor bandgap was realized.
Global antimony production is about 5x global silver production, and antimony is only about 3x more abundant in Earth's crust. This ZnSb semiconductor probably would not scale well.
Looks like Cove ran into some powerful opposition in NYC.
"Like the coal and oil, water power is not within the reach of the average man. If he is to use it in the future he must buy it from the capitalist as he does now from the coal baron or the oil king. It is difficult, however, to see how any commercial corporation or combination can monopolize the direct rays of the sun." (Quote attributed to Winthrop Packard, 1909. See Ref#19 in [0])
Ah, the naivete. Turns out that all you need to do is pay the government to do it for you. Some states make it outright illegal to disconnect from the power grid, for example.
https://www.energy.gov/eere/solar/linear-concentrator-system...
The Crescent Dunes CSP plant in Nevada had a number of stumbles, but appears to be generating power again:
https://en.wikipedia.org/wiki/Crescent_Dunes_Solar_Energy_Pr...
Their solution of storing thermal energy in molten salt isn't exactly low-tech, but other CSP systems use cheaper thermal storage materials like sand or basalt, which avoid the geopolitical and environmental problems of lithium extraction. Of course, PV panels can dump power into thermal batteries too. Maybe PV farms with huge thermal batteries of sand or basalt will be the best long-term grid-scale solution.