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c1ue
05-10-10, 04:18 PM
As part of some work I've been doing with a friend considering changing industries, I have been looking further into solar energy - specifically Photovoltaics (PV).

A brief overview:

PV solar energy is the use of semiconductors to create electricity from sunlight. The physics are not directly relevant to those not wonkish, but what is of importance are the following:

1) materials
2) efficiency

On the materials side, there are a number of choices including polycrystalline silicon, monocrystalline silicon, microcrystalline silicon, gallium arsenide and progressively more exotic material types.

By far the most common is silicon.

At this point a brief detour into wonkdom is necessary: the poly, mono, and micro silicon variants provide the substrate or base to the device. Consider it the equivalent of the base of a table or building.

In order to perform, the silicon (of whatever type) is then both doped (impurities added to increase/decrease specific electrical properties) as well as built upon (layers of wires or other structures).

Thin film is another term often used - it merely refers to a different way of laying down the layers. The analogy of thin film vs. 'normal' processing is that thin film is like painting a car without stripping and priming it first: quicker, cheaper, but generally not as high quality.

This brings us to efficiency:

Efficiency is the ratio of how much energy in a given 'amount' of sunlight is actually captured by the PV panel and transformed into electricity.

Industry averages right now are around 20% with actual install base ranges from 12% to 18% (Wiki)

Now for the economics part:

Depending on the material, the actual effective efficiency of a PV panel degrades over time. The reason is that the dopants (impurities) added as well as the structure of the PV device itself will change with temperature changes as well as more fundamental electrical effects.

For poly and microcrystalline devices, this means 50% decrease in throughput over a 30 year time span. This isn't speculation - this is straight out of the labs from someone who has a PhD in this field and has been working creating devices serving this field for 15 years.

Single crystal in contrast will see significantly lower degradation.

In economics terms: an installation serving the typical family (900 Kilowatt hours/month) at install time will see the solar installation failing to meet the family's needs in 10 years or less.

Now consider that the average family must invest in order to afford this installation:

http://www.chelanpud.org/documents/SNAP_ASES_Paper.pdf

According to this study, the cost for a 1 kilowatt installation is about $9000 per KW. Assuming 8 hours a day, 30 days a month, a 25% margin, and a 25% loss due to storage, transmission, or other factors, the required installation is 900/240*1.25*1.25 = 5.86 Kilowatts = 6 Kilowatts = $54000.

This is a chunk of change. But factor in the efficiency decline, and the install cost factor rises considerably.

This is a fundamental problem with the economics of solar energy as a primary energy source.

Fortunately the friend's startup has a much different business model - actually looks very promising even from my point of view.

Andreuccio
05-10-10, 04:34 PM
Best of luck to your friend.

I looked at solar about a year ago. After running the numbers, it didn't much sense to me, even with the government picking up a big chunk of the tab. Declining efficiency as outlined in your post makes it even less attractive.

we_are_toast
05-10-10, 07:06 PM
I'm about 80% solar 20% wind, total cost about $14,000, did the installation myself, before the government rebates. It's sooooo expensive.


MIT researchers print solar cell on paper.

Scientists at the Massachusetts Institute of Technology have successfully coated paper with a solar cell, part of a suite of research projects aimed at energy breakthroughs.
Susan Hockfield, MIT's president, and Paolo Scaroni, CEO of Italian oil company Eni, on Tuesday officially dedicated the Eni-MIT Solar Frontiers Research Center. Eni invested $5 million into the center, which is also receiving a $2 million National Science Foundation grant, said Vladimir Bulovic, the center's director.
The printed solar cells, which Bulovic showed at a press conference Tuesday, are still in the research phase and are years from being commercialized.
However, the technique, in which paper is coated with organic semiconductor material using a process similar to an inkjet printer, is a promising way to lower the weight of solar panels. "If you could use a staple gun to install a solar panel, there could be a lot of value," Bulovic said.

...
http://www.cnn.com/2010/TECH/05/06/cnet.mit.print.solar.cell/?hpt=Sbin

And fossil fuels will get so much cheaper as they're rapidly depleted.:rolleyes:

c1ue
05-10-10, 07:36 PM
I'm about 80% solar 20% wind, total cost about $14,000, did the installation myself, before the government rebates. It's sooooo expensive.

And how many kilowatt-hours did you use in a month before going solar/wind?

And is your car electric?

I recently bought an electric scooter - Goped ESR750EX, lead acid - for work purposes.

Works pretty well, and costs 10 cents to recharge.

But then again, I can only go about 8 miles. After the battery dies, it is 7 hours + to recharge.

And there's no space for a 'baby on board' sticker...much less the baby.

As for paper - the printed stuff is cheap to make, no question.

The problem is both efficiency and durability. I suspect after 30 years in the sun, anything printed on paper is going to have some significant deterioration...

After all, vacuum tubes didn't go out of style just because they are big and expensive...the reliability aspect was probably the biggest factor.


And fossil fuels will get so much cheaper as they're rapidly depleted.:rolleyes:

And in 30 years when the depletion becomes a true scarcity factor, will your investment will have repaid itself?

ggirod
05-10-10, 11:14 PM
Sometimes, C1ue, you provide that extra special quote that just cries out for a response. This is one of those times.
After all, vacuum tubes didn't go out of style just because they are big and expensive...the reliability aspect was probably the biggest factor.I guess it would be a good idea to dissect your statement as you might anothers' so here goes...

Reliability: to quote Wikipedia:
In the 1960s, transoceanic cables were coaxial cables (http://en.wikipedia.org/wiki/Coaxial_cable) that transmitted frequency-multiplexed voiceband signals (http://en.wikipedia.org/wiki/Frequency-division_multiplexing). A high voltage direct current on the inner conductor powered the repeaters. The first-generation repeaters are among the most reliable vacuum tube (http://en.wikipedia.org/wiki/Vacuum_tube) amplifiers ever designed.<sup id="cite_ref-7" class="reference">[8] (http://en.wikipedia.org/wiki/Submarine_communications_cable#cite_note-7)</sup> The gutsy engineers who designed these amplifiers for the cable provided power in the form of kilovolts DC at the European landing to a "ground stake" in the new world and connected all of the amplifiers in series between ends, like Christmas Tree bulbs. Any failure along the thousands of miles and the whole thing was toast. Thousands of feet under water, there were no service calls. The lines still mostly work but are uneconomical because they handle so little volume. In spite of thousands of miles with beaucoup amplifiers, THEY NEVER FAILED. We can worship their reliability and workmanship and lament the era passed when the world was simple enough to use them with their bandwidth. They never failed, the world changed. They became a solution to a problem nobody cared to solve that way any more.

Power Consumption: In my college years, about the time that vacuum tubes were still being laid in the ocean, I had the astounding chance to restore a piece of surplus; the analog computer that originally calculated the first moon-orbiting mission in the space program. Filling ten feet of tall equipment racks, the vacuum tubes, servo motors, potentiometers, and associated miscellany required the electricians to install a new circuit into the lab to provide enough power to run the system. After it got enough power, it could only be used in a Minnesota winter, when we turned off the heat and opened windows to provide enough cooling air to keep it running. It worked, I graduated, and I will never forget the first graph that came off the machine. It was a wonderful teaching device. The large tubes, potentiometers, motors, and other components involved in the calculations made the solutions concrete in ways students back then could grasp. A few years later, it would fit into a cigar box ... then a thimble ... then a fingernail. The power would go from kilowatts to watts to milliwatts to do the same thing. Technology advanced and much more powerful solid state hardware was launched into space as the voyager series, which continue to give us data to this day, duplicating the wonder of vacuum tube reliability with integrated circuits. Vacuum tubes never really failed. They simply became redundant because the world and its needs changed.

Reliability II: The Russian military may even still use vacuum tube equipment for some of their most critical functions. Electromagnetic pulse from nukes is notoriously difficult to protect against, and solid state equipment robust enough to withstand it is still rare. Vacuum tubes can survive it without a problem, though their other limitations present challenges to military strategy. Modern day survivalists in the US recognize the value of vacuum tube equipment in the Mad Max conditions that would follow an electromagnetic pulse attack against the US. If you see survivalists using hand held transceivers, you better not be taking them seriously. They are clueless. On the other hand, if they show you boat-anchor WWII communications gear, you know they are serious and likely to be able to communicate. Don't underestimate those vacuum tube buggers .. they are tough!

The parallel of vacuum tubes with fossil fuels is sobering. Alternatives to fossil fuels already exist but they are not being adopted very quickly. Fossil fuels and the filthy "externals" they produce like mercury poisoning in our fish stocks around the world, sulfur and other compounds that kill trees if released and toxic drywall if sequestered, CO2, which in adequate quantities threatens humanity ultimately with a repeat of extinctions past, and repeated oil slicks that may just reproduce for us, the Dinosaur era anoxic oceans that gave us oil in the first place. To add to the insult, it is already clear that fossil fuels are a dead end and that their replacement is imperative. They will run out and leave us high and dry after wringing the last drops of life out of human society on the way.

Why do fossil fuels not step aside politely to alternative energies as the vacuum tubes stepped aside in favor of new technologies? The answer is that alternative energy is hard. It is not the quick, easy, swap of a universally better solution for a poorer one. It is a better solution, but it is short term a more expensive one. People go with short term whenever they can. Not only that, but fossil fuels will be profitable in the same way Tobacco was profitable; poisoning people while producing profits. Alternative energy requires that PEOPLE, not technology, change. People need to prioritize energy use that is important and reduce wasteful energy consumption. They need to adjust to change. Maybe, as in the example above, if they don't want individually to spend an insane $54K they should consider

A: whether they REALLY need 900 KWH per month or whether something else might spark their fancy.
B: Maybe a bit of insulation in the house, a light colored roof, solar water heat, passive solar heating, geothermal cooling, or all of the above might be a good idea.
C: Maybe they conserve now, save some money, and invest later when technology is cheaper.
D: Maybe they should get a bid from somebody else who has his head screwed on right and knows what they are estimating.

Or, maybe for the time being they simply buy desert solar energy to support an alternative that is much cheaper and more efficient. Or, maybe they support an idea like wind farms from Maine to Florida so that at any given time a good portion of the installation is getting lots of wind and power to supplement the total output is not required. Already solar and wind energy are proving their worth in appropriate situations and multitudes of solutions exist to solve the remaining problems. The real problem is that people need to invest intelligently now to assure their future. Smart people will. The rest ... well ... Fat chance. The rest will point to arctic solar installations that mysteriously don't work in the winter, solar installations in chronically cloudy locations, or wind farms in the Horse Latitudes that don't quite spin up to full speed much.

I am not easily persuaded to believe in Intelligent Design, but sometimes, in that "foxhole conversion" that comes of reading too many denial comments, I sincerely pray that GOD designed this earth to have less fossil fuel than is required to destroy it by its side effects. That way, the human race's survivors will be able to use their fledgling alternative energy technologies to restart an intelligent presence on this planet when the plunderers are done with it. Hope springs eternal.

c1ue
05-11-10, 01:23 AM
The first-generation repeaters are among the most reliable vacuum tube (http://en.wikipedia.org/wiki/Vacuum_tube) amplifiers ever designed.<SUP class=reference id=cite_ref-7>[8] (http://en.wikipedia.org/wiki/Submarine_communications_cable#cite_note-7)</SUP>

The 1608 vacuum tubes in the submarine cables do not compare with the tens of thousands of vacuum tubes in the actual computers of the era.

If you want to talk about centimeter size metal connectors - then certainly vacuum tubes are great.

But clearly centimeter sized metal connectors wouldn't work for anything beyond simple repeater amps. The ENIAC machines were a prime example:

http://www.linfo.org/eniac.html


The high burnout rate (on average several tubes per day) did turn out to be a major problem, resulting in the computer being nonfunctional about half the time. However, as most of these failures occurred during the warm up and cool down periods, when the tubes were under the greatest thermal stress, it was soon realized that the solution was to keep the computer running continuously, thereby reducing the number of tube failures to only about one every two days.


So if you want to compare a tube amp used in a stereo system vs. a transistor in almost everything else, you are welcome to do so. It is completely nonsensical though.


Vacuum tubes never really failed.

They failed all the time. They still fail - except of course in a power amplification environment where the metal leads are in the centimeter range and are very reliable.

As both a power engineer AND an IC designer, I know the difference quite well. Unfortunately you apparently do not.


The Russian military may even still use vacuum tube equipment for some of their most critical functions.

The Russians use vacuum tubes because they don't have the access to military grade semiconductors. And that is due to export restrictions on the type of equipment my friend produces.


whether they REALLY need 900 KWH per month or whether something else might spark their fancy.

The 900 KwH is the average household usage in the US.

If you wish to drive that downward, be my guest. But you'll find it tough sledding to get people to make do with less. More importantly, by forcing the use of alternative energy, you effectively discriminate against the poorer part of the population.

Much as rich people can get by eating fully certified organic food - $20/pound beef vs. $5/pound beef is irrelevant from an upper middle class/upper class disposable income standpoint - so too can rich people continue to consume 10000 kwH whether the price is $0.09 or $0.50 per kwH.

Similarly all of the lovely technologies you put forward require major capital investment; money the average American simply does not have.

Forcing everyone to pay subsidies to alternative energy then disproportionately squeezes the less wealthy to subsidize the more. The people enjoying the solar subsidies aren't the poor, but they are the ones paying for higher energy bills - and unlike income taxes, energy costs are NOT progressive.

So ignore the realities of the economics if you want - the above is straight from the people who make the equipment which makes the solar panels.

You'll note that the degradation noted above is not for ALL solar, it is for all solar not using single crystalline substrate.

But then again, that costs more.

As for me - I'll note you failed to disprove a single technical point I made concerning the physics of solar photovoltaic generation.

Every single ad hominem rant was some bizarro agenda where alternative energy is better than fossil fuels even when it isn't - because it is 'green'.

Only when truly better alternatives are found will people change; trying to force everyone to adopt frankly immature and half-baked (literally) solutions will fail and very possibly destroy the social agenda that comes with it.

The company my friend is going to work for has the right focus and the right mindset - and I hope it is successful.

But equally this company attempts to do NONE of the pie-in-the-sky things which you apparently hope solar can do.

Ghent12
05-12-10, 05:12 PM
I think the central lesson is that photovoltaics are merely a source of energy and not a magic bullet. They "make sense" in applications where other sources of energy are somewhat less viable, such as in satellites and Hawai'i.

Only faith can make them more valuable than they really are...

RebbePete
05-14-10, 09:20 AM
According to this study, the cost for a 1 kilowatt installation is about $9000 per KW. Assuming 8 hours a day, 30 days a month, a 25% margin, and a 25% loss due to storage, transmission, or other factors, the required installation is 900/240*1.25*1.25 = 5.86 Kilowatts = 6 Kilowatts = $54000.


We're in the process of getting a similar system installed (actually, closer to 7 kW). We're getting monocrystalline panels and paying about $15K less up front than your quoted price. With incentives in our area of the country (Maryland) that include Renewable Energy Credits and grants, the final cost after all the immediate (i.e., one year or less after install) rebates and credits is about $10K. That's right - the government incentives reduce the cost of the system by about 75%! :cool: Payback is anticipated to be 5-7 years assuming a 7%/year increase in electric rates (which I think is very conservative).

Without the incentives, we wouldn't be doing it. I'm jumping now since, considering the sorry condition of state and local government finances, I doubt the incentives will last more than another year or two. I don't know how cap and trade on the federal level will affect this, but it probably won't hurt!

- Pete

c1ue
05-14-10, 09:49 AM
Pete,

Thanks for the color.

Is your system in the 20% efficiency range?

Is it a focused solar or ambient solar system?

If the efficiency were 30% and the subsidies were 25%, would you still install a system? And what would the payback time be?

p.s. I hope you have also considered protection systems for your investment. If people are willing to steal copper sheathing off roofs of churches...

RebbePete
05-14-10, 10:16 PM
1. No, I believe the average is around 15%. The panels are by Schueco.

2. Ambient solar

3. I can't do that kind of math in my head! Aww, I'll give it a shot... Hmm... twice the efficiency, but 1/3 the subsidy. Let's say I could then get it for around $20K up front, with a $5K subsidy, means $15K. I probably would still do it.

4. Right now my protection system is manufactured by Smith and Wesson. ;) The system is roof top as opposed to pole mount, so stealing it would take some effort. In a "Mad Max" scenerio, things could get interesting. I'm not expecting anything quite that bad, however. If electricity gets scarce, I plan to share some with my neighbors so they have a stake in keeping everything right where it is.

- Pete

c1ue
05-15-10, 08:49 AM
Pete,

Again, thanks for the info.

My analysis with my friend concluded that a 30% minimum solar efficiency is necessary for the industry to survive without massive subsidies.

Anything over 25% so far seems to involve focused - i.e. using a lens to concentrate sunlight, as well as multi-junction (i.e. can capture energy from multiple wavelength ranges).

Jeff
05-16-10, 03:34 PM
I think it's important to view solar power, and PV specifically, in the event of a black swan. Nothing is ever obvious at the margins when emerging, but all of the analysis goes sideways in the face of $400 bbl oil. If the bandwidth on the internet had expanded at a linear rate from the time when EJ and I first worked on it, we'd be looking forward to 1 megabit backbones any day now.

Owning gold is especially interesting when civil war breaks out, and PV is most interesting when oil goes bonkers. It's all about hedging the expected with the unforseen or hard to imagine. (That's why I'm posting this from a beach on Maui;-) Who could have imagined?)

Rajiv
05-16-10, 05:37 PM
C1ue,

One factor that I find missing from calculations, is the land area requirements for coal plants. A rule of thumb is one hectare per MW of installed capacity. This will become increasingly higher as one moves to burning poor quality coals as India and China have already done (I am not talking of mining operations, but only the land requirements for power generation.) At 15%, efficiency the land requirements are identical. However, in solar PV generation, the land can be spread out and be "multi-use." I do not think that most comparisons today take that into account. Also, the land required for coal plants is typically prime agricultural land, in riverine tracts. For PV any land will suffice -- of course desert areas work the best.

Also, the current costs of construction of a coal fired power plant are approaching $2M per MW of installed capacity. The running costs of the power plant are over and above this.

c1ue
05-16-10, 08:09 PM
I think it's important to view solar power, and PV specifically, in the event of a black swan. Nothing is ever obvious at the margins when emerging, but all of the analysis goes sideways in the face of $400 bbl oil. If the bandwidth on the internet had expanded at a linear rate from the time when EJ and I first worked on it, we'd be looking forward to 1 megabit backbones any day now.

Transmission rates for data are a very different matter than energy generation. Just as television was able to go from 1 channel to the present hundreds and thousands, so too is information transfer scalable from kilobits to terabits.

Power generation, however, doesn't work that way. A fiber optic trunk line, even built out to the house threshold, is a low 4 digit cost per person.

A conversion to solar energy is at least 1 order of magnitude larger. Adding in electrified transport pushes it closer to 1.5 orders of magnitude.

Certainly if you've got the dough, putting in 20 kilowatts of solar energy is a nice backstop.

But very few people have this luxury.

For that matter, the money used to install 20 kilowatts of solar energy could equally build, stock, and maintain a 30 foot sailboat for escape...

And in 30 years, you're going to have to do it again.


One factor that I find missing from calculations, is the land area requirements for coal plants. A rule of thumb is one hectare per MW of installed capacity. This will become increasingly higher as one moves to burning poor quality coals as India and China have already done (I am not talking of mining operations, but only the land requirements for power generation.) At 15%, efficiency the land requirements are identical. However, in solar PV generation, the land can be spread out and be "multi-use." I do not think that most comparisons today take that into account. Also, the land required for coal plants is typically prime agricultural land, in riverine tracts. For PV any land will suffice -- of course desert areas work the best.

Also, the current costs of construction of a coal fired power plant are approaching $2M per MW of installed capacity. The running costs of the power plant are over and above this.

Ah, now you're starting to get into the right frame of mind.

If you are talking central electricity generation, solar power outside of a few areas compares very poorly with pretty much any other energy source.

For example: While the Southwest US has excellent insolation, the hottest areas also tend to be the driest - and equally tend to have very few people living in them. Thus basing huge solar plants in the Mojave is no different than building coal plants in Northern California: the electricity generated has to be transmitted significant distances to population centers.

And just how effective is solar energy in the context of an urban area? Where land area per person is far less than in the suburbs?

The analysis above was used primarily to understand the retail solar market - 30% efficiency is the baseline at which solar energy is reasonably competitive without government subsidies for individuals.

For commercial generation, however, efficiencies must be much higher. 40% is a minimum threshold there and even then a lot of additional assistance is needed to be competitive (i.e. carbon offsets).

Rajiv
05-16-10, 08:38 PM
In general, I would agree with your assessment of PV under the current economic conditions. However, I remain sceptical of both coal and nuclear, because both are based on very optimistic raw material projections. The economies of both technologies rapidly deteriorate as the coal quality degrades, and as the quality of uranium ore degrades. Also, much of the cost of electricity from coal is based on power plants that have already depreciated the construction costs, and thus are paying only maintenance and fuel costs. Cost of new coal plants given what will be increasing limitations on the availability of high quality coal, IMO makes coal far less attractive.

Also, 30% and higher efficiency PV is coming down the pike. Rose Street Labs is already inpilot production for 30% efficiency cells. As they continue developing the Indium Nitride technology further, efficiencies of 50% to 70% may be possible.

See Rose Street Labs Press Release (http://www.rosestreetlabs.com/RSLE Tandem Press Release.pdf) and the original research at LBL - An unexpected discovery could yield a full spectrum solar cell (http://www.lbl.gov/Science-Articles/Archive/MSD-full-spectrum-solar-cell.html)

RebbePete
05-17-10, 08:03 AM
Also, 30% and higher efficiency PV is coming down the pike. Rose Street Labs is already inpilot production for 30% efficiency cells. As they continue developing the Indium Nitride technology further, efficiencies of 50% to 70% may be possible.

See Rose Street Labs Press Release (http://www.rosestreetlabs.com/RSLE Tandem Press Release.pdf)and the original research at LBL - An unexpected discovery could yield a full spectrum solar cell (http://www.lbl.gov/Science-Articles/Archive/MSD-full-spectrum-solar-cell.html)

But, can you get the relatively exotic materials (like indium) in sufficient quantities to make enough cells to put a dent in electrical generation needs? :confused:

No matter what, the problem with solar (or, with wind for that matter) is, what do you do when the sun isn't shining (e.g. at night or on a cloudy day)? In my mind, the biggest problem with PV systems isn't the PV cells themselves, but the energy storage medium. Our system at home is a grid-tied system, which relies on the grid itself having the capacity to backstop us on low solar yield days.

By the way, even in a city, you can put enough cells on the roof to make a significant contribution to electrical needs. In Baltimore, a lot of the city is "row houses" which open up the prospect of a "communal" solar array that extends across multiple rooftops. In a grid-tied environment, perhaps the savings of the system could be divided among the property owners on whose roofs it resides.

- Pete

c1ue
05-17-10, 11:50 AM
Also, 30% and higher efficiency PV is coming down the pike. Rose Street Labs is already inpilot production for 30% efficiency cells. As they continue developing the Indium Nitride technology further, efficiencies of 50% to 70% may be possible.

I'll look into Rose Street Labs - the question of multi-junction and focused vs. vanilla/ambient solar is not a purely academic question.

Focusing matters because you're basically harvesting the sunlight from a larger area. Instead of say 2 square meters of solar cell at 20% efficiency, you might have 1 square meter of solar cell at 40% efficiency but still covering 2 square meters. The actual energy output per square meter is identical. Obviously this is a simplification - but this is why focused vs. ambient matters.

As for multi-junction: multi-junction means far more complex solar cells. What a lot of people don't internalize is that solar cells are gigantic. Typical semiconductor devices are sub-micron sized (45nm production now); typical solar devices are centimeter sized.

Thus even as the semiconductor side is affected less and less by material costs (as opposed to processing costs), the solar side will always be affected by materials costs. And the materials costs for silicon are highly subsidized by the semiconductor industry.

But the turning point for this is coming. I actually believe the costs for solar will continue to drop for as many years as a decade after which costs will soar; the semiconductor side is now seeing that 3D integrated circuits is actually cheaper than simply making smaller transistors.

To be clear - it isn't true 3D: it is making 2 chips which interconnect across the tops of their respective layers - like putting to pie plates top to top. Memory makers are already doing this.

Why is this? Because while the packaging is more complex (than normal packaging), a new packaging plant costs maybe $1B to $2B vs. a $5B state of the art IC plant. Similarly the performance gains from such an approach are actually more easily reaped using 1 or 2 generation old technology than the latest and greatest.

Bottom line: a company like Intel - which presently has 5 IC plants - could likely get by with 1 packaging and 1 IC plant. The remaining 4 will go out of business - but in the meantime will depress solar prices.

Once those 4 plants disappear though and replicated across the industry - along with a major downsizing of the semiconductor equipment manufacturers (80% less customer base is unavoidable), the solar panels will greatly increase in price both due to supply issues and due to the fact that any sem/solar manufacturing is inherently an energy hog.


But, can you get the relatively exotic materials (like indium) in sufficient quantities to make enough cells to put a dent in electrical generation needs? :confused:

This is actually less of an issue than you might think. The reason these materials are not actively mined is primarily because the market for them is small. I really doubt much more than 1 ton of indium is used in the entire world. That's why the sources today are primarily as offshoots of some other type of mining.

But conversely the small usage means even a massive increase in price won't affect final product much. After all, the price of gold increasing from $270 to $1230 hasn't impacted the prices of ICs which use gold leads.


By the way, even in a city, you can put enough cells on the roof to make a significant contribution to electrical needs. In Baltimore, a lot of the city is "row houses" which open up the prospect of a "communal" solar array that extends across multiple rooftops. In a grid-tied environment, perhaps the savings of the system could be divided among the property owners on whose roofs it resides.

In the US, even most cities are really not that dense.

How many square meters is the 7 KW installation that you put in?

The building I live in has roughly 25 families in it; I doubt it has more than 700 square meters of rooftop. This is probably enough for a full on solar installation even if we were all willing to cough up the $1M. The numerous high rise condos nearby though are all 40 stories or more with perhaps 4 to 6 families per floor.

But the majority of residential housing in SF is much less dense.

The real point though is that even if solar-fication was practical for the entire US (it is not), the cost would be $4T (100M families times $40K).

And would have to be replicated in 30 years.

And still backed up by conventional energy.