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 Tags Solar power

 24th January 2008, 10:51 PM #41 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 Matteo: From (partially) remembered university lectures, I was working on incident solar power being about 1kw/m2. There is a site (oregon university from the domain name?) that seems to halve this...
 24th January 2008, 10:59 PM #42 Matteo Martini Banned   Join Date: Dec 2004 Posts: 4,371 Originally Posted by jimbob Matteo: From (partially) remembered university lectures, I was working on incident solar power being about 1kw/m2. There is a site (oregon university from the domain name?) that seems to halve this... Quote: Assume our roof top area is 100 square meters (about 1100 square feet). In the winter on a sunny day at this latitude (40o) the roof will receive about 6 hours of illumination. So energy generated over this 6 hour period is: 300 watts per square meter x 100 square meters x 6 hours = 180 KWH (per day) more than you need. But remember the efficiency problem: 5% efficiency 9 KWH per day 10% efficiency 18 KWH per day 20% efficiency 36 KWH per day At best, this represents 1/3 of the typical daily Winter energy usage and it assumes the sun shines on the rooftop for 6 hours that day. With sensible energy conservation and insulation and south facing windows, its possible to lower your daily use of energy by about a factor of 2. In this case, if solar shingles become 20% efficient, then they can provide 50-75 % of your energy needs Apparently, you can make it "with 20% efficient solar panels" and "with sensible energy conservation and insulation and south facing windows". I do not get if "typical daily Winter energy usage", includes gasoline consumption for your car. Probably not.
 30th January 2008, 01:44 PM #43 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 Matteo, The figures have to exclude the car consumption, as 16kW for 2hours, gives 32kWh. I think the assumption is domestic energy usage. Anyway the figures show why a solar-powered car won't be feasible, even if the it can use stored energy that was ultimately generated photovoltaically. On to the economics, this article has some interesting figures: Photovoltaics: Grid Competitive in Five Years It includes a graph with different scenarios on cost and what seems like reasonable extrapolations (as well as the usual guff aka "wildcard technology currve"). From Deutche Bank. And another blog entry with quite a long discussion comming to a similar conclusion. The interesting thing is that the concensus is not if solar generation is going to be economically viable, but when and by how much... We are at the beginning of an exponential growth in the solar, and other renewable energy usage. Wind power for example is also growing fast: Installed U.S. Wind Power Capacity Surged 45% In 2007 According To AWEA
 30th January 2008, 08:08 PM #44 Matteo Martini Banned   Join Date: Dec 2004 Posts: 4,371 Originally Posted by jimbob Matteo, The figures have to exclude the car consumption, as 16kW for 2hours, gives 32kWh. I think the assumption is domestic energy usage. [..] Reading your links now, however, please note that the battery of the Volt is 16KWh, and you need to fill that battery, not a 32KWh, I think
 30th January 2008, 08:14 PM #45 Matteo Martini Banned   Join Date: Dec 2004 Posts: 4,371 Originally Posted by jimbob On to the economics, this article has some interesting figures: Photovoltaics: Grid Competitive in Five Years It includes a graph with different scenarios on cost and what seems like reasonable extrapolations (as well as the usual guff aka "wildcard technology currve"). From Deutche Bank. And another blog entry with quite a long discussion comming to a similar conclusion. The interesting thing is that the concensus is not if solar generation is going to be economically viable, but when and by how much... We are at the beginning of an exponential growth in the solar, and other renewable energy usage. Jimbob, I do not know how they can claim the price of solar energy has kept falling in the last years, as it has been almost stable since 2001 (http://www.solarbuzz.com/moduleprices.htm)
 31st January 2008, 01:04 PM #46 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 Originally Posted by Matteo Martini Jimbob, I do not know how they can claim the price of solar energy has kept falling in the last years, as it has been almost stable since 2001 (http://www.solarbuzz.com/moduleprices.htm) I am guessing that this is the difference between manufactured cost and installed cost (where I imagine labour makes a large part), or possibly adjusted for inflation?
 1st February 2008, 08:19 AM #47 BenBurch Gatekeeper of The Left     Join Date: Sep 2007 Location: The Universe 35.2 ms ahead of this one. Posts: 37,535 If this works and is cheap enough and DURABLE enough, this will be a real aide in avoiding the coming Malthusian Crisis. __________________ For what doth it profit a man, to fix one bug, but crash the system?
 5th February 2008, 04:53 PM #48 Scrubber New Blood   Join Date: Jan 2008 Posts: 1 Who reads the Scientific American? Originally Posted by Cuddles No. Cheapness and efficiency are pretty much interchangeable. It's no good having cells five times cheaper if they're five times less efficient. In fact, for a given product of cost and efficiency, expensive but efficient cells will be better since available space will be less of a factor. Of course, the actual winner depends on the details, and it is hard to see in this case due to the reluctance to by Nanosolar to actually say anything in public (which in itself suggests they are not as good as they are made out to be). However, the figure given in the Wiki article is for efficiency of 14%, with a maximum of 20% for this kind of cell. They say they hope to sell them for \$1 per Watt eventually, which means they are currently more expensive. This means that the figures of 5 times less efficient and 5 times cheaper are likely close to reality, and so these cells are no improvement at all over existing cells, except that they will take up more space, are largely untested and of unknown durability. I am surprised that this discussion does not mention an article in January's Scientific American. It has not reached Australia yet, but I came across it on the web. It proposes vast photovoltaic solar arrays in the deserts accompanied by underground compressed air storage for nighttime supply, and new D.C. powerlines. The fact that there is no mention of it in this thread makes me wonder if I hallucinated the whole thing!
 7th February 2008, 07:31 AM #49 Cuddles Penultimate Amazing   Join Date: Jul 2006 Posts: 18,538 Originally Posted by Scrubber I am surprised that this discussion does not mention an article in January's Scientific American. It has not reached Australia yet, but I came across it on the web. It proposes vast photovoltaic solar arrays in the deserts accompanied by underground compressed air storage for nighttime supply, and new D.C. powerlines. The fact that there is no mention of it in this thread makes me wonder if I hallucinated the whole thing! I don't read Scientific American, but that's certainly not a new idea. It generally doesn't get much consideration because it's not actually a very good idea. Photovoltaics just aren't that efficient. If you're going to build a large solar power stations, you're much better off capturing the heat and using it to produce steam, and there are several solar power plants already in existence, and more planned or being built. I just had a quick look at the article in question, and it really seems nothing more than idle speculation, with very little consideration of reality. Grand schemes like this can never work. Aside from the issue of photovoltaics not being the best solution, you just can't make that many big changes all at the same time. This scheme wouldn't just require replacing the existing infrastructure, it would require building an entire new energy infrastructure to run in parallel with the existing one. The whole idea is just stupid on so many different levels. Edit: Forgot to mention the cost thing. They say that the electricity could be sold very cheaply, but conviently fail to link that to the fact that it would also mean hundreds of millions of dollars in subsidies for several decades, during which there would be no return whatsoever. Good luck getting those taxes past the voters. Last edited by Cuddles; 7th February 2008 at 07:33 AM.
 23rd November 2013, 04:43 AM #51 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 Originally Posted by Cuddles Yeah, I have to concede that you're probably both right. Efficiency is important if you're planning to use solely solar power, but if it's a choice between getting a small amount of power from your roof with inefficient panels or having nothing at all because you can't afford it, the cheaper ones certainly win. However, this has gone off at a bit of a tangent from the OP. Regardless of what would be best in terms of solar cells, what is actually important is if they can do what they claim. There are an awful lot of claims about what the cost could be once they're available for general consumption, but not much about what they actually are now, and nothing whatsoever about the actual efficiency or reliability. Also, as the article you quote points out, prices of existing solar cells have been plumetting for years, and are still going down. Even assuming these new ones are everything they claim, by the time they are actually available they may not have any advantage over existing ones. Looks as if that's what happened... __________________ OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending
 23rd November 2013, 08:03 PM #52 Charlie Wilkes Illuminator     Join Date: Dec 2009 Posts: 4,177 Originally Posted by jimbob Looks as if that's what happened... My opinion, as someone who lives off the grid with a home power system, is that storage is the big issue. I use lead-acid batteries, and they come with lots of problems. I can see why utilities don't want to pay full rates for solar going back into the grid from distributed sites, because they still have to maintain the plant capacity to generate power when the sun goes down. They can solve this with large solar installations by storing heat to power a steam turbine. But distributed systems will have to use something else. Hydrogen generators and fuel cells have finally become a viable technology, but they are very expensive. If the price comes down, they could be used to generate power 24/7 and the grid could buy or sell it as needed. Here is a working, small-scale fuel cell setup: http://www.siei.org/mainpage.html
 24th November 2013, 03:47 AM #53 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 Originally Posted by Charlie Wilkes My opinion, as someone who lives off the grid with a home power system, is that storage is the big issue. I use lead-acid batteries, and they come with lots of problems. I can see why utilities don't want to pay full rates for solar going back into the grid from distributed sites, because they still have to maintain the plant capacity to generate power when the sun goes down. They can solve this with large solar installations by storing heat to power a steam turbine. But distributed systems will have to use something else. Hydrogen generators and fuel cells have finally become a viable technology, but they are very expensive. If the price comes down, they could be used to generate power 24/7 and the grid could buy or sell it as needed. Here is a working, small-scale fuel cell setup: http://www.siei.org/mainpage.html Not entirely sure about that, Charlie, because that would affect other photovoltaic manufacturers as well. The PV market has recently been in a severe period of downturn* but that seems to be ending, and the fundamental trend is upwards. I agree that storage is a key issue, and one where there is a lot of avenues being explored - which suggests that there isn't a clear winner at the moment. Some of the solutions won't scale up or down easily - an obvious one being the molten sodium salt storage solution for large scale concentrated solar power. Ditto pumped-storage hydro (which is a grid-scale balancing system). In the semiconductor industry (which I regard as being closely tied to the PV market - there are common precursor materials, and the price in one affects the other) there are have been many technologies which didn't get off the ground because their theoretical advantages over silicon were countered by industrial inertia, and the consequent higher rate of innovation in the larger silicon industry. As one of my lecturers said, "Gallium Arsenide - "the technology of tomorrow, and always will be"** *see my earlier comments about similar forces to the semiconductor industry - there are positive feedback loops in the PV market making it an unstable oscillatory system. Over the last few years at work I was getting lots of email alerts auctioning off manufacturing equipment from failed PV suppliers, but these have recently dried up, as the upturn starts. **he'd come from a premature Gallium-Arsenide startup in the 1980's. GaAs/AlGaAs is successful in niche areas, but hasn't yet made a breakthrough - however as Silicon gets closer to its fundamental performance limits, alternatives become more viable. __________________ OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending
 24th November 2013, 01:54 PM #54 Charlie Wilkes Illuminator     Join Date: Dec 2009 Posts: 4,177 Originally Posted by jimbob Not entirely sure about that, Charlie, because that would affect other photovoltaic manufacturers as well. The PV market has recently been in a severe period of downturn* but that seems to be ending, and the fundamental trend is upwards. I agree that storage is a key issue, and one where there is a lot of avenues being explored - which suggests that there isn't a clear winner at the moment. Some of the solutions won't scale up or down easily - an obvious one being the molten sodium salt storage solution for large scale concentrated solar power. Ditto pumped-storage hydro (which is a grid-scale balancing system). In the semiconductor industry (which I regard as being closely tied to the PV market - there are common precursor materials, and the price in one affects the other) there are have been many technologies which didn't get off the ground because their theoretical advantages over silicon were countered by industrial inertia, and the consequent higher rate of innovation in the larger silicon industry. As one of my lecturers said, "Gallium Arsenide - "the technology of tomorrow, and always will be"** *see my earlier comments about similar forces to the semiconductor industry - there are positive feedback loops in the PV market making it an unstable oscillatory system. Over the last few years at work I was getting lots of email alerts auctioning off manufacturing equipment from failed PV suppliers, but these have recently dried up, as the upturn starts. **he'd come from a premature Gallium-Arsenide startup in the 1980's. GaAs/AlGaAs is successful in niche areas, but hasn't yet made a breakthrough - however as Silicon gets closer to its fundamental performance limits, alternatives become more viable. My experience with polycrystalline panels is that they have an indefinite service life with no maintenance, and that counts for a lot. They are also a lot cheaper than they used to be. Once they have a really large installed base and they account for > 10 percent of the power in certain regions, it may be possible for companies to enter the marked with incrementally better PV technologies. But storage is ultimately what holds solar back, IMO. As of now, the solar power model seems to be distributed. I'm all for it, but only if it really helps to solve a problem instead of making people feel greener than they really are. In AZ the power company wants to pay lower rates for solar power, and they want to charge customers a grid fee. The counter-argument is that subsidies are necessary to move toward a more sustainable energy model. But with the storage problem unsolved, are we moving toward anything or are we just kidding ourselves on a large scale, as is the case (IMO) with ethanol? Can we have distributed generation and centralized storage with molten salt/pumped hydro, or does that just get ridiculous (which would be my superficial take)? Are you familiar with Nocera's lectures on this? He is a proponent of fuel cells and distributed power.
 24th November 2013, 04:11 PM #55 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 Distributed storage with plug-in hybryd cars is an approach that might be interesting. As an aside, the fab where I work has its own uninterruptable power supply: flywheels the size of a two-story house spun up in a vacuum, and with enough kinetic energy for about half an hour's use, and two marine diesels that are guaranteed to cut in within half a minute of an outage. Apparently we get a tariff reduction if we agree to go off-grid at times of peak demand. __________________ OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending
 24th November 2013, 08:43 PM #56 Charlie Wilkes Illuminator     Join Date: Dec 2009 Posts: 4,177 Originally Posted by jimbob Distributed storage with plug-in hybryd cars is an approach that might be interesting. As an aside, the fab where I work has its own uninterruptable power supply: flywheels the size of a two-story house spun up in a vacuum, and with enough kinetic energy for about half an hour's use, and two marine diesels that are guaranteed to cut in within half a minute of an outage. Apparently we get a tariff reduction if we agree to go off-grid at times of peak demand. I don't think electric cars are going to pan out unless they come up with something better than chemical storage batteries, or at least chemical storage batteries that have a service life beyond anything that is available now. I will be interested to see how these \$80k Tesla cars are doing in 5-10 years. I hope my misgivings turn out to be wrong. Interesting about the flywheels... I didn't realize they had been commercialized at all. That might be a good automotive technology, in about 100 years.
 25th November 2013, 02:41 PM #57 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 Originally Posted by Charlie Wilkes I don't think electric cars are going to pan out unless they come up with something better than chemical storage batteries, or at least chemical storage batteries that have a service life beyond anything that is available now. I will be interested to see how these \$80k Tesla cars are doing in 5-10 years. I hope my misgivings turn out to be wrong. Interesting about the flywheels... I didn't realize they had been commercialized at all. That might be a good automotive technology, in about 100 years. Pretty sure that flywheels are a bad automotive technology. They store rotational kinetic energy, and thus there is a lot of angular momentum and lots of mass. Fine for stationary systems, although I do find it a bit steampunk for our use (which is a cool thing). I agree with you about full electric vehicles, I'm hopeful for fuel cell technology - supercapacitors are improving rapidly, but their energy density still is low. To me, the time to recharge full-electric vehicles is a bigger problem than the range* makes them impractical as the sole vehicle for many people in my opinion. They could be fine for commuting however** *With an ICE, it is very quick to get a few hundred miles additional range in about 5-minutes. **The median commute distances in the US and the UK are surprisingly short, last time I looked both were under 10-miles, which means my 12-mile cycle to work is further than most people's car commutes. If the climate is good and one doesn't want to use muscle power alone, then E-bikes and pedelecs are probably more fun, cheaper and practical than an electric car for commuting. Cycling is more reliable than cars on my route - usually slower, but very predictable journey time. __________________ OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending Last edited by jimbob; 25th November 2013 at 02:42 PM.
 26th November 2013, 10:25 AM #58 Cuddles Penultimate Amazing   Join Date: Jul 2006 Posts: 18,538 Originally Posted by jimbob To me, the time to recharge full-electric vehicles is a bigger problem than the range* makes them impractical as the sole vehicle for many people in my opinion. This news is particularly interesting. Only around half the range of a current diesel car, but as you say if you can fill up in a few minutes that's much less of a problem. The main problem, as the article notes, is the lack of infrastructure. Also that none of the cars are actually available yet, but claiming they'll be here next year is at least closer than they've been before. Quote: If the climate is good and one doesn't want to use muscle power alone, then E-bikes and pedelecs are probably more fun, cheaper and practical than an electric car for commuting. Cycling is more reliable than cars on my route - usually slower, but very predictable journey time. Doesn't even need a good climate, just look at China. In the big cities, you'll probably never see an ICE bike, and very few pedal ones, they're pretty much all electric. There's no technological or economic reason they haven't caught on in the West, it's purely societal.
 26th November 2013, 10:55 AM #59 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 I remember in the early 1990s reading about vanadium batteries that were recharged by topping up the electrolyte. the wiki article explains why they haven't caught on. Cuddles, Hydrogen (or methanol) fuel cells do have many potential advantages as far as I can see. __________________ OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending
 26th November 2013, 12:15 PM #60 Modified Philosopher     Join Date: Sep 2006 Posts: 6,401 Originally Posted by jimbob Pretty sure that flywheels are a bad automotive technology. They store rotational kinetic energy, and thus there is a lot of angular momentum and lots of mass. The angular momentum can be overcome with gimbal mounts or paired flywheels. Energy storage density is better than batteries if you don't need containment. The main problems at this point are getting magnetic bearings to work reliably under the g-forces a car goes through, safety - which means either a lot of extra weight needed for containment or a lot of danger, and probably cost. Safety is a big issue. If the flywheel shreds, you have a huge release of energy in a very short time - basically a bomb.
 11th January 2014, 08:31 AM #61 jimbob Uncritical "thinker"     Join Date: Jan 2007 Location: UK Posts: 18,717 Originally Posted by Modified The angular momentum can be overcome with gimbal mounts or paired flywheels. Energy storage density is better than batteries if you don't need containment. The main problems at this point are getting magnetic bearings to work reliably under the g-forces a car goes through, safety - which means either a lot of extra weight needed for containment or a lot of danger, and probably cost. Safety is a big issue. If the flywheel shreds, you have a huge release of energy in a very short time - basically a bomb. Yes, and you have to have a large amount of angular inertia, so I can't imagine that cornering would be much fun. (Paired flywheels probably being a better idea than gimball mounts due to the additional mass). Thinking a bit more about the various different schemes for energising a car. If you want to drive for several hours and only spend a short time refilling (similar to current petrol cars) then I think that chemical energy is the only option. To make the sums easy - suppose you want to be able to drive and only spend four minutes re-energising every two hours. If you transfer electrical power to the car, then you need 30-times the average power use of the car plus a bit for waste (you need just over one joule per joule transferred). If you transfer fuel, with several MJ/kg energy density, then you need far less to transfer from say a pump to the car, maybe several micro-Joules per Joule and well under one mili Joule per Joule. This means that the power requirements for the "pump" are far more benign. __________________ OECD healthcare spending Expenditure on healthcare http://www.oecd.org/els/health-systems/health-data.htm link is 2015 data (2013 Data below): UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending

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