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Author: Subject: Solar energy a pipe dream?
smuv
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sad.gif posted on 16-7-2011 at 21:34
Solar energy a pipe dream?


I was discussing solar energy with someone, and it got me thinking I should run the numbers to try to figure out assuming (unrealistically) 100% efficient capture, how much of the earth needs to be covered with solar panels to fulfill global energy consumption. The number I got out, was 17,000 sq miles. Although this works out to be about half of Portugal in area, (or about 0.009% of the earth) is it feasable that we could even build solar panels/concentrators on this order of magnitude?

I know a lot of variables are being left out (such as variance of solar energy by location and efficiency of panels) but still, this is a generous ballpark figure to analyze feasibility.

What are your thoughts? Am I a pessimist?

How I calculated
-Total energy from sun that strikes face of earth each year: 5.5×10^24 J (wikipedia)
-Total world yearly energy consumption (2008): 4.74x10^20 J (wikipedia)
-Surface area of earth: 57510000 sq mi

Formula: Energy consumption/Suns energy * Area of earth

Idiot check: A book (Industrial Organic chemistry) quoted 0.005% of the earths surface, which is lower than what I calculated but still within an order of magnitude.




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[*] posted on 16-7-2011 at 23:08


Solar towers utilizing steam turbines will offer a cheaper and more efficient source of electric power than solar panels.

The earth's surface has plenty of deserted areas to build vast arrays of solar panels. The problem is getting the electric current to populated areas. There are significant loses from resistance over long distances. Superconductive electric lines would be a solution, but the type of superconductors that can handle high current require expensive liquid-helium cooling. Solar panels can be built into commercial building rooftops, and this can provide sufficient power for most non-industrial purposes. Most of the electricity used goes to manufacturing. If there is to be any real progress made in the world at converting to solar power, the western governments need to provide strong incentives to China, as much of the products consumed in the west are actually produced in China. Simply forcing factories to use expensive solar power will just drive all the manufacturing away to other countries that use cheap power from inefficient polluting sources. It is almost completely futile for the governments to think that getting people to use energy-efficient compact fluorescent lighting in their home will make any difference (I also really hate those spiral lights). I do not know why they use fluorescent lighting in schools, it makes it harder for many of the students to concentrate, and it is much less pleasant than the soft glow of an incandescent bulb. There is always LED, but that apparently is "too expensive", even though LED lights last an extremely long time (typically over 20 years) before they burn out.

The main problem is that using solar power is much more expensive. At least five times as expensive as coal-derived power. Taxing carbon dioxide emissions, and putting tariffs on Chinese goods based on pollution, would be the best way to shift to using renewable energy sources. The best way to ensure the use of more renewable resources is to provide strong incentives for large businesses to use less energy, not just to simply use more "efficient" devices.

I think harnessing the energy in ocean waves would be the best option. Waves have a higher energy density, so it would be easier to harness their power. There is also plenty of available coast in the more northern regions in which the weather is more cloudy, making solar panels less effective.




I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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[*] posted on 16-7-2011 at 23:15


Actually, liquid helium cooled superconductors are out-dated, there are already liquid nitrogen cooled ones, although mass producing them is not affordable at the moment (as with the helium cooled ones).
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[*] posted on 17-7-2011 at 01:32


Solar energy is not a pipe dream, though it is not suited for all places and even in suitable places it should not be expected to provide 100% of energy.

The first point to consider is that not all joules are created equal. Naive or disingenuous solar critics may cite the enormous potential energy embedded in oil, and the tremendous difficulty of replacing all those joules with solar electricity. The challenge is daunting, but not as bad as a simple joule-for-joule comparison would suggest. For example, under favorable conditions an efficient small car like the Ford Fiesta can travel 1 kilometer using 0.059 liter (2.05 megajoules) of gasoline. A Nissan Leaf can travel 1 kilometer using 200 watt hours (0.72 megajoules) of electricity. The Leaf makes nearly 3 times better use of its joules because electric motors can turn electricity into motion very efficiently.

Likewise, replacing gas or fuel oil for warming homes and buildings does not require a one-for-one joule replacement by electricity. Heat pumps can use less than 1 joule of energy to add 1 joule to the inside air temperature, at least until the outside air temperature gets very low. Even under very cold conditions ground coupled heat pumps can continue to warm air more efficiently than plain resistive heating.

Heating and cooling consume the lion's share of energy in homes and building, and these functions can be performed with solar-thermal inputs as well as solar-electric. Warming water and air can be done much more cheaply with direct thermal absorption systems than with electrical systems. Even air conditioning and refrigeration (absorption refrigeration systems) can be driven by relatively cheap, low-grade solar heat. Further, new structural designs (or simply insulation upgrades in existing structures) can substantially reduce the energetic inputs required for climate control.

According to a technical report by the National Renewable Energy Laboratory, there is sufficient space on existing roof tops in the USA for PV solar to supply 819 terawatt hours annually; for comparison, the USA's nuclear reactors produced about 800 terawatt hours in 2010, out of about 4000 terawatt hours of total electric generation. The base case scenario in the NREL study assumes only 13.5% solar conversion efficiency. Silicon based modules are already commercially available with greater than 20% conversion efficiency. At 20%, the rooftop potential is 1213 terawatt hours, or about 30% of total current electric generation in the USA. The scale of deployment would be vast, to be sure, but it requires no improvements in PV efficiency, no rare elements or complex multi-junction cells, no additional land consumption, and no new long distance transmission lines.

There's already more than enough land, more than good enough conversion efficiency, and more than enough joules for the taking from the sun*. The greatest problem is the variability of solar generation with time and location, which means that supply is poorly matched to demand much of the time. Matching variable renewable supply and demand probably requires some combination of demand management, extra transmission capacity, and energy storage. This is complicated and expensive. I personally expect that in the sunniest regions PV electricity will be less expensive than coal-fired electricity before the end of the decade, but only if it can be used immediately and locally without storage or long-distance transmission. It is an interesting challenge to consider what processes might be designed or redesigned to profitably use cheap electricity that comes from variable and low-capacity-factor generation.

*Note that wind and conventional hydroelectric power are (indirectly) also forms of solar energy.




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[*] posted on 17-7-2011 at 05:38


Quote:
Solar towers utilizing steam turbines will offer a cheaper and more efficient source of electric power than solar panels.


Cheaper? What makes you think so? Plumbing and moving parts for high-temperature working fluids tend to be expensive and have low MTBF. Granted the reflectors are cheaper than a photovoltaic panel, but I don't think you come out ahead.
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[*] posted on 17-7-2011 at 09:19


Quote: Originally posted by bbartlog  
Quote:
Solar towers utilizing steam turbines will offer a cheaper and more efficient source of electric power than solar panels.


Cheaper? What makes you think so? Plumbing and moving parts for high-temperature working fluids tend to be expensive and have low MTBF. Granted the reflectors are cheaper than a photovoltaic panel, but I don't think you come out ahead.


Solar thermal plants scrap steam for photovoltaic

Some large projects are swapping PV for solar thermal because there are more deployed PV systems as data points for risk modeling, PV costs have declined faster than thermal, and PV siting is more flexible. Another point, not mentioned in the article, is that PV needs less water to operate than thermal based plants.

In my opinion, the biggest downside of going to PV from thermal is the missed opportunity for relatively low cost energy storage. Thermal systems that directly heat molten salts can buffer energy at comparatively low cost just by adding larger insulated storage tanks and more salt mixture, so that system electrical output can be matched to demand much better than a simple PV system. At current low penetration rates of intermittent renewables I suppose there's not much material incentive to take demand-matching into account for project ROI.




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[*] posted on 17-7-2011 at 10:28


My neighbor a few houses down just got something like this for his roof.
http://www.npr.org/templates/story/story.php?storyId=1279853...

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[*] posted on 17-7-2011 at 10:45


I guess we will see. I would love solar to provide cheap renewable energy, but the scale needed to deploy it makes me skeptical. We are not talking about building a few solar sites here and there, it would have to be a MASSIVE effort just to make a dent. The quoted all rooftops to = power of nuclear, means that if everyone put solar panels on their roof, you only get 8-9% of U.S. ELECTRICITY generation not energy consumption. Which is really just a drop in the bucket. Another thing is, last I checked in the northeast and other regions of the country, over the lifetime of the solar panel you barely get back the energy required to manufacture it.

I guess in some places, solar makes sense, but I think a lot of people look at it as a silver bullet, and it is simply not.




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[*] posted on 17-7-2011 at 11:30


Solar Stirling motor 3kW infinia
http://www.youtube.com/watch?v=VEpq-WCTOrM

Stirling Dish 500MW solar power plant
http://www.youtube.com/watch?v=OTQ4cFn5sXs

[Edited on 17-7-2011 by Morgan]
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[*] posted on 17-7-2011 at 13:03


Quote: Originally posted by smuv  
I guess we will see. I would love solar to provide cheap renewable energy, but the scale needed to deploy it makes me skeptical. We are not talking about building a few solar sites here and there, it would have to be a MASSIVE effort just to make a dent. The quoted all rooftops to = power of nuclear, means that if everyone put solar panels on their roof, you only get 8-9% of U.S. ELECTRICITY generation not energy consumption. Which is really just a drop in the bucket. Another thing is, last I checked in the northeast and other regions of the country, over the lifetime of the solar panel you barely get back the energy required to manufacture it.

I guess in some places, solar makes sense, but I think a lot of people look at it as a silver bullet, and it is simply not.


Actually, nuclear supplies about 20% of US electricity consumption, and as I mentioned above rooftop solar could provide 30% if you assume the use of higher-efficiency panels instead of the the rather poky 13.5% in the NREL base case scenario. Also as mentioned above, substituting electricity for other forms of energy generally means that you need fewer total joules to get the same amount of useful work done. For example, even in the base case, rooftop solar provides enough electricity to replace all gasoline used by passenger commute in the US, if electric vehicles were substituted for internal combustion engine vehicles.

I don't think there is a single silver bullet that can assure affordable, reliable energy for the long term without terrible side effects. For my part I favor nuclear energy, renewable electricity, and (while it remains available) natural gas -- basically Anything But Coal. I think that solar can provide a significant part of the energy needed to power a comfortable technologically advanced civilization. If you look at a PV solar resource map of the United States, assuming stationary panels, even Arizona gets less than double the annual solar energy that Maine gets. Solar panels can easily repay their manufacturing energy costs, and more, in any state in the continental US. It is the financial payback that is still difficult.

As recently as 2008 I considered PV solar an expensive joke unless you lived in a very sunny place with no electrical grid. It's still expensive, even compared to other forms of renewable energy, but it's made impressive strides in increasing scale and cutting manufacturing cost in the last few years. There are credible, substantial cost-reduction measures still to play out over the rest of the decade. And unlike wind, wave, or hydro power, solar PV can easily scale down to a single building or home, so it can compete directly against retail electricity costs to the end-user rather than against generation costs to a utility.




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[*] posted on 17-7-2011 at 13:15


Quote: Originally posted by Morgan  
Solar Stirling motor 3kW infinia
http://www.youtube.com/watch?v=VEpq-WCTOrM

Stirling Dish 500MW solar power plant
http://www.youtube.com/watch?v=OTQ4cFn5sXs

[Edited on 17-7-2011 by Morgan]


Oh, that's interesting. It looks like the company started right in my town and so did the first commercial demonstration project. 24% conversion is very good and with dual-axis tracking they will be able to capture a lot of solar energy. The main downside is that the siting options are more limited compared with PV, since light diffused through cloudy conditions is useless for it.




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[*] posted on 17-7-2011 at 13:49


Just a razzle dazzle demo/presentation for the general viewing audience - I guess it would be fun to play with.

Jem Melts Rock Using Sunshine
http://www.youtube.com/watch?v=z0_nuvPKIi8
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[*] posted on 17-7-2011 at 14:47


Touche polverone. I'm glad you made those points, makes me feel better about our energy future.

But for sure, that is A LOT of solar panels! But I guess if its cheaper than coal...it will happen.

I like the PV resource map link.

[Edited on 7-17-2011 by smuv]




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[*] posted on 18-7-2011 at 10:23


The economy argument has many flaws. People will buy everything, even if it's very expensive and unnecessary. And people that will use that for their own profit exist. There are quite lots of them, too.

The problem with solar energy is people failing to understand that there are at least three possible energy benefits from it.
First of all, we all use the energy of the Sun, solar or thermal. We grow food using photosynthesis, we heat our homes using infrared rays. Seems like nothing, but it's a lot.
Second thing, there's light to electricity, and the third one is heat, or pure thermal energy.

First one is self explanatory.
Second one is usage of photovoltaic elements, and that's the main problem.
Third is thermal, which can be really, really great for reducing the consumption of electricity per capita, but not everywhere, and not always.

Regarding photovoltaics, in most cases you get a bad Chinese product that was made by heavy industry that sucks ass when it comes to basic filtering and containing the pollution. Greenhouse gasses, heavy metal, hydrogen fluoride emissions, etc.
That product, applied in the temperate geographical zones inhabited by soccer moms and hippies will probably never work long enough to pay itself off - in joules of energy. In dollars it will, of course. As I've said, people will buy everything. Economy is a bitch.

Putting PV in, let's say London, is laughable. It's a terrible economic burden, and somewhere on Earth, tons of coal were turned to toxic smoke and soot just to make a soccer mom think she's "enviromentally conscious".

The amount of pollution that is produced for PV (per joule) greatly exceeds the one from coal energy. Yeah, coal produces lots of pollution, but also gives a lot of energy. PV in temperate zone produces massive pollution, but gives bits and pieces. And it doesn't work at night, so you have to use chemical batteries, which are ridiculously inefficient, require heavy pollution to be produced, and have a short lifespan.

And to think there are actually so called "green activists" that support PV together with electric cars (which are enviromentally viable only in certain cases) is scary, because they're gaining power and influence.


Light-to-electricity has also one problem, from an engineering standpoint, which you forgot to mention. When such "renewable energy sources" reach some 20-30% of the whole net energy production, the system starts to fail because each of these power plants require too much backup.
And guess which one is it? Gas. When cloud obscures the sunlight, there's a sharp drop in the produced energy, and if you want your country/city to have a proper operating machines and appliances, you have to ensure there are no gaps and peaks in voltage and frequency. Something similar happens with windpower, although that source is much more viable and less bullshity. There were some power drops and surges that knocked power gridswhich was caused by such excessive relying on unstable sources.

So if you give 100 kW using sunlight, you need 100 kW of gas waiting to quickly jump in. Double the initial pollution.


PV is great if it's too expensive to lay a powerline to a remote location which has plenty of sunlight and doesn't require lots of energy. And it's great for leveling peak consumption in places in the tropics and close to it.
But trying to use it for the base of the power system in a temperate country is incredibly stupid from an engineering, energy and enviromental standpoint.

Experts in the power industry know it, just as the professors at faculties. Those people often do a facepalm when confronted with hippie BS.

And yeah, I'm not one of those capitalist "let's burn all the fossils and spend everything" kind of guys. I really am pro-enviroment, but I've got a brain, too.
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[*] posted on 18-7-2011 at 12:45


I think you have it backwards. Energy payback is not hard to get from PV systems, but financial payback is. Financial payback currently requires remote off-grid applications or government incentive schemes like feed-in tariffs. It is unfortunately difficult to evaluate the "real" cost of energy from different sources because all energy producers enjoy various direct and indirect government supports everywhere but Somalia, and in different ways so it's hard to normalize for comparison. Different technologies also aren't held to the same standards in controlling their negative externalities. Coal plants, for example, annually contribute to tens of thousands of premature deaths from smokestack emissions. Over the last 25 years, even including Chernobyl and Fukushima, nuclear power has directly and indirectly killed fewer people than coal power does every year. But most people seem to fear cancer from radiation more than cancer from smoke, so coal gets a free pass.

On the matter of PV energy payback times:

This 2004 NREL study, based on older yet data, estimates about 3.7 years for energy payback using insolation levels equal to the average for the continental United States.

This 2005 study estimates maximum energy payback times of 2.2 years for silicon PV in southern Europe.

IEEE Spectrum: How Free is Solar Energy? Even in Moscow energy payback time for current silicon PV is just over 3 years. If systems last less than 20 years they still have a healthy energy payback ratio. In Phoenix, Arizona the energy payback time is under 2 years.

On the matter of dirty PV production: it is true that producing PV systems requires toxic chemicals and produces negative environmental externalities, particularly when production is located in jurisdictions with weak or poorly enforced environmental regulations. But so does producing the industrial equipment for any energy generation scheme. Gas turbines, diesel engines, and coal plants don't grow on trees either, and over their life cycles they have worse environmental externalities per kilowatt hour of energy produced.

I am one of those crazy people who supports electric and plug-in hybrid vehicles and hopes to see increased PV electrical production. I see them as complementary moves. Electric vehicles can substantially reduce demand for expensive, dwindling, and politically volatile oil, and they can take better advantage of intermittent renewables than most electric loads. If I have an electric vehicle that I use for errands and commuting to work, I only care that its battery is topped up each morning when I go to use it. I don't care when during the day or night it is recharged. The vehicle can charge when renewable sources are peaking/less expensive and defer charging when electricity is less available/more expensive. I agree that the electric grid cannot tolerate a large fraction of intermittent renewables without storage at present, and perhaps not ever, but it's going to take a while for the USA to even approach the 20% limit.




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[*] posted on 18-7-2011 at 14:11


I am very skeptical regarding the graph where m(CO2)/kWh is lower for PV than the one for nuclear power. That seems like a joke. I'm not buying it. Fission is orders of magnitude more efficient, and its carbon footprint should be way smaller than PV's.
PV carbon footprint depends on the place where it's utilized, and even if you put it in Dubai, it shouldn't be close to fission. It's way less than coal, but can't be close to fission.
And I disagree with the energy return. It can't be close to 2-3 years. Few years ago, it was "more than 10 years". Usually close to 15. During the 80's, it was over 20.
AFAIK, it's close to 5 years, if there's enough sunlight through the year. That is the fact which is always missing.

Those things break apart easily, if there's lots of rain. I'd imagine a high quality PV running for a decade or more in an arid area, but in Frankfurt, Paris... 5 years tops, and then water creeps inside.

I am pro-PV, but only where it's viable, complementary and if used by the experts' directive, not money, like it often happens.
That is during the day in places where enough sunlight is plentiful, but limited to the peak thirst for power. PV's can not be the base of power production. The base is coal, hydro (if available) and fission. It is simply impossible to supply a modern city using just, or predominantly PV. It is too weak, too expensive and too unreliable.

I really dislike coal, but that is the only option for a country that doesn't have much hydropotential left, and its citizens are unfortunately furiously opposing fission.
Coal has that nasty drawback that it really causes a whole bunch of seemingly hidden deaths. The stacks send not only chemical poisons, but also radionuclides. Way, way more than any normal operating fission plant. Not many people know that. They usually think that the steam from cooling towers in NPPs is actually burned uranium, and the smoke from CPPs is "just some smoke". Trust me, there are tons of fools like that, and those are government voters.


I'd really like to see solar thermal gaining more usage. Passive decentralized heating. Of course, where and when it is viable.
For example, here where I live, on the Adriatic coast, we have really hot and arid summers. I'm suffering trough one right now. So why not using solar heaters on roofs? Those things are pipes and black paint, some glass, a boiler and a pump, essentially You get really hot water without any aditional expense.
They pay off in few summers at most. But people are usually lazy as hell, or don't have the money for initial investment. That's where government should jump in. Funny idea, I know. ;)


I see the energy future as a blend of coal/fission/hydro base, gas and wind for the middle and upper middle, and solar (thermal or PV) for peaks and reducing the usage of gas. Coal will not be abandoned, and won't be exhausted soon, that's for sure.


Regarding electric cars, I'm sure you're aware of the fact that power doesn't grow on trees, and it's not "made by wall plugs". Using an electric car only transfers the problem elsewhere. If the base was predominantly fission, and the batteries were a lot better, those cars would be very enviromentally friendly. But in America today, with the majority of power being derived from coal, and batteries being crappy as they still are, they aren't. They only lower the local smog, but the total CO2 production is even higher, because the energy chain gains one more link.

[Edited on 18-7-2011 by Endimion17]




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[*] posted on 18-7-2011 at 14:56


Quote: Originally posted by Endimion17  

Regarding electric cars, I'm sure you're aware of the fact that power doesn't grow on trees, and it's not "made by wall plugs". Using an electric car only transfers the problem elsewhere. If the base was predominantly fission, and the batteries were a lot better, those cars would be very enviromentally friendly. But in America today, with the majority of power being derived from coal, and batteries being crappy as they still are, they aren't. They only lower the local smog, but the total CO2 production is even higher, because the energy chain gains one more link.


This is not true. In the USA, coal provides just under half of all electricity generated. It is also a decreasing fraction of new generation capacity being added. Even if 100% of electrical energy is supplied by coal, electric or hybrid electric vehicles still have modestly lower lifetime CO2 emissions than pure internal combustion engine vehicles. See Life Cycle Assessment of Greenhouse Gas Emissions from Plug-in Hybrid Vehicles: Implications for Policy

Coal plants can run at higher thermal efficiency than automotive internal combustion engines. Electric vehicles also do not need to keep engines idling while stopped. These factors may account for an electric vehicle "running on coal" still emitting less than a typical gasoline powered vehicle.

I welcome alternative analyses of PV power and electric vehicles from peer reviewed sources, but simply saying "I am very skeptical... I'm not buying it... It can't be..." isn't very good evidence.




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[*] posted on 18-7-2011 at 14:59


I did a similar calculation and arrived at a similar number. 10,000 square miles of solar cells placed in Arizona to replace the fossil fuels in the USA. A square mile of anything seems like a lot! By comparison there are 3.7e6 square miles of roads in the USA.

Those energy payback times are misleading. That is the time to get back the energy used to create the cells. The more important number is the amount of time to pay for the cost of the cells, which is on the order of 20 years (I live in San Jose CA and the online estimator told me that including a 30% rebate from the government and rate increases from the utilities, it would take it would take 17 years to reach break even). Given that the estimated life of the panels is also around 20 years they may never pay for themselves.

As fossil fuels are depleted their cost will go up and solar will become more competitive and we will see more solar power put into use.

It looks like energy was at its cheapest (in terms of labor expended per joule or BTU or KWh or??
back in the 60s and the price will only go up from here. (Unless there is a breakthrough in Fusion which looks unlikely.)
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[*] posted on 18-7-2011 at 16:27


Its interesting to consider just the electric grid alone.
Wiki states 39KWH per person per day in the USA.

At 5 hours insolation and a currently impossible 20% efficiency to make the numbers easier that's a minimum of 40 square meters of solar per person just for the electric grid alone. 60 square meters is more reasonable.

the solar cells themselves aren't expensive, I recently bought 3 kilowatts worth of 17% efficient cells for $800. its the glass, EVA, frame, shipping and labor to manufacture them that costs money. But if you build them yourself with surplus glass, they will pay for themselves even in the pacific northwest at 3-4 hours of insolation per day.
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[*] posted on 18-7-2011 at 16:43


Quote: Originally posted by Polverone  
This is not true. In the USA, coal provides just under half of all electricity generated. It is also a decreasing fraction of new generation capacity being added. Even if 100% of electrical energy is supplied by coal, electric or hybrid electric vehicles still have modestly lower lifetime CO2 emissions than pure internal combustion engine vehicles. See Life Cycle Assessment of Greenhouse Gas Emissions from Plug-in Hybrid Vehicles: Implications for Policy

Coal plants can run at higher thermal efficiency than automotive internal combustion engines. Electric vehicles also do not need to keep engines idling while stopped. These factors may account for an electric vehicle "running on coal" still emitting less than a typical gasoline powered vehicle.


I stand corrected. Coal is 21.58%, according to EIA in 2009.
http://www.eia.gov/emeu/aer/pdf/pages/sec1_3.pdf

But my biggest concern is all of the fossil fuels. If you combine all of them, you get over 80%. AFAIK, that's how much France produces nuclear power alone.

Could you tell me, cause I don't have the time to study the whole paper, is the life cycle of the batteries included in the study, or just the vehicle alone?


Quote: Originally posted by Polverone  
I welcome alternative analyses of PV power and electric vehicles from peer reviewed sources, but simply saying "I am very skeptical... I'm not buying it... It can't be..." isn't very good evidence.

I'm just expressing my concern, and I base it on my knowledge of energy densities of various sources and their availability.
What might be viable in 20 years for arid Dubai, will never be for a foggy London, no matter what kind of PV we produce.
Because it isn't all in the technology that is "just waiting to improve and become competitive". It's got something in the sheer facts about the sources themselves.
I've got a friend who works abroad in one lab. Thin film deposits and his research is partially in the PV domain. He's one of the most pessimistic people I know regarding light-to-electricity. Cold shower, and I mean freezing cold shower.
That doesn't mean things won't change, but technology is one thing, and the energy source is another one.

I'd be very happy if we had efficient and cheap fusion, and electric cars with very dense energy storage. But we don't.



Quote: Originally posted by gregxy  
I did a similar calculation and arrived at a similar number. 10,000 square miles of solar cells placed in Arizona to replace the fossil fuels in the USA. A square mile of anything seems like a lot! By comparison there are 3.7e6 square miles of roads in the USA.

It is a lot. It's like one third of Ireland!
And it solves nothing. Those are the numbers for PVs running during the day, in the sunny, arid zones, and there aren't plenty of those in the populated areas. When you do more realistic calculations, you get disturbing figures.

But these arguments are not even needed, because no one rational would expect that PV can replace all of the coal. We aren't talking about it either.

What America needs is to finally start respecting the RRR. Reducing the impact and consumption, reusing and recycling what is viable (most isn't, but that's another story). The most important thing is the reduction. All the recycling green hippie movement is utter crap if people don't reduce consumption of resources, and energy is one of them. Yet, we don't see that happening. It's "living the high life" for the most part of the inhabitants, compared to the world.

[Edited on 19-7-2011 by Endimion17]




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[*] posted on 18-7-2011 at 16:47


Quote: Originally posted by johansen  

the solar cells themselves aren't expensive, I recently bought 3 kilowatts worth of 17% efficient cells for $800. its the glass, EVA, frame, shipping and labor to manufacture them that costs money. But if you build them yourself with surplus glass, they will pay for themselves even in the pacific northwest at 3-4 hours of insolation per day.


Right now the cells themselves account for just over half of system costs, and the balance just under half. It's expected that cells will be just under 50% of system costs by next year because cell costs are declining faster than balance of system costs.

To aggressively reduce solar prices further it is not just the cells that have to get cheaper. It also requires cheaper and more standardized installation permitting processes, and less expensive inverters, mounting, and packaging.

Higher-efficiency cells can kill two birds with one stone. Using higher efficiency cells fits more generating capacity in a fixed area like a single roof. The cells themselves may command a price premium, but can offset that increase by reducing costs for packaging, framing, and installing a kilowatt of capacity. Gradual improvements from process tweaks also allow manufacturers to increase production (as rated by peak watts) without additional capital or labor costs, which means better profit margins for the manufacturer in the short term and lower prices for everyone in the long term.




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[*] posted on 18-7-2011 at 17:15


Quote:

Could you tell me, cause I don't have the time to study the whole paper, is the life cycle of the batteries included in the study, or just the vehicle alone?

The life cycle of lithium ion batteries is included.

Quote:

I'm just expressing my concern, and I base it on my knowledge of energy densities of various sources and their availability.
What might be viable in 20 years for arid Dubai, will never be for a foggy London, no matter what kind of PV we produce.
Because it isn't all in the technology that is "just waiting to improve and become competitive". It's got something in the sheer facts about the sources themselves.
I've got a friend who works abroad in one lab. Thin film deposits and his research is partially in the PV domain. He's one of the most pessimistic people I know regarding light-to-electricity. Cold shower, and I mean freezing cold shower.
That doesn't mean things won't change, but technology is one thing, and the energy source is another one.


If your friend works in thin film technology I am not surprised that he is pessimistic ;)
For at least 10 years the promise of thin film has been high conversion efficiency combined with low production cost, but it has been very difficult to translate into commercial success. Only First Solar has been a big success, and there isn't enough tellurium available for everyone to imitate First Solar.

Boring conventional silicon PV still has more than 80% of the market, and commercial silicon cells are available with higher efficiency than any commercial CIGS or CdTe thin-film devices. It is hard to tell if thin-film will ever surpass silicon PV in market share. Silicon may already have too large a head start in terms of process experience, manufacturer ecosystems, and economies of scale. It also has the advantage of not requiring expensive and possibly supply-limited elements like indium and tellurium.

I don't think that PV solar can replace 100% of electricity consumption in any currently developed nation. Certainly not in London! But solar cells already have a lifetime positive energy payback even in London's dismal insolation. The question of economic payback is much harder to project. I wouldn't be terribly surprised if PV declines in price over the long term so that it becomes economically attractive even in London (although there isn't enough insolation for London to get a large fraction of total electricity from PV even if it has the lowest marginal cost).




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[*] posted on 18-7-2011 at 17:34


People keep repeating that solar power can never completely replace coal power. I find this illogical. If solar power can provide 10% of our power needs, is it really that much harder for it to provide 100% of our current consumption? It is merely one order of magnitude difference. Relatively little of the resources in society go toward developing solar power. It would not really be too much of a stretch to improve current efforts twenty-fold. But again, I stress that the best way to reduce our impact on the environment is to reduce our consumption. Better urban designs that would minimize the need for cars (and reduce commuting times) are also important.

Making solar panels more efficient may likely prove increasingly difficult, as incremental improvements take much research, and all the easy strategies have been used. I have read of one design that additionally harnesses the waste heat from the panels using thermoelectric coupling. There is also photothermolectric panels that could utilize much of the short infrared spectrum. This needs more research, but seems very promising. The real savings will come from scale of production; as more solar panels are produced, the price per unit will dramatically fall in the long term (unless future panels require rare-earth elements).

The thing I wonder about is whether, as solar power becomes much more predominant, whether it will become controversial. This has been the case with wind farms. People are complaining it obstructs the natural scenery, and the turbine blades kill many birds. Solar panels on all the houses might be less pleasant to look at. The best place for panels is on the roofs of already ugly commercial blocks and factories, in any case, most of these flat roofs are not even vissible, except from a plane above.

[Edited on 19-7-2011 by AndersHoveland]




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[*] posted on 18-7-2011 at 18:02


Quote: Originally posted by AndersHoveland  
People keep repeating that solar power can never completely replace coal power. I find this illogical. If solar power can provide 10% of our power needs, is it really that much harder for it to provide 100% of our current consumption? It is merely one order of magnitude difference. Relatively little of the resources in society go toward developing solar power. It would not really be too much of a stretch to improve current efforts twenty-fold. But again, I stress that the best way to reduce our impact on the environment is to reduce our consumption. Better urban designs that would minimize the need for cars (and reduce commuting times) are also important.


I think you answered your own question. Solar will not provide energy equal to 100% of current consumption not because it is physically impossible, but because A) it is not going to be the best option everywhere, even among renewables and B) even if you're giving up all fossil fuels, it's cheaper to economize on consumption first than to build out non-fossil energy sources as a 1-for-1 replacement of oil, gas, and coal.

I think that solar PV has a better shot than competitors about overcoming NIMBY opposition. It doesn't make noise, it's not visible from far away, and in normal operation or failure it doesn't pose any great health risks to nearby animals* or humans.

Solar and wind have the additional unfortunate problems, mentioned earlier, of being intermittent and at least somewhat unpredictable. This means that you cannot continue to operate a stable electrical grid with a large wind/solar component without building in storage mechanisms or excess dispatchable generating capacity, which greatly increases the cost. If someone invents an inexpensive, rapidly responsive, non-geography-dependent storage mechanism for renewable energy I'll go from cautiously optimistic about solar to downright bullish. But in discussing the future potential of solar or other energy sources I don't like to assume any big breakthroughs.

*At least if it's deployed on roof tops or brownfield sites. Deploying it on large scale in remote areas may indeed harm animals due to the ground shading, new transmission line corridors, and new access roads.




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[*] posted on 19-7-2011 at 01:03


NIMBY's are the least concern. If you spend some money on education of people, they will understand and won't make a fuss out of it. But if you let them live in ignorance and fear, you get the situation with fission in America, where towns use old power plants from the 70's instead of building passive safety, new generation reactors like France does (and earns a whole lot of money by selling the energy to dumb Italy which halted its nuclear power program because of fear, like radionuclides from France couldn't ever cross the border... dumbasses).

PV can't replace coal in the most of populated places in Northern Temperate Zone because the energy source is unpredictable and has extremely low energy density.
And it doesn't work at night. People seem to forget that their efficiency, which is poor and today reaches almost 30% for the most expensive and newest and best laboratory samples (the ones on the market are usually 10% if their wafer quality is good) is only when the Sun is high in the sky and there are no clouds. And that is not the case. In real life, you have clouds, low Sun, atmospherilia gradually eating the panels and greatly reducing their lifetime, dust, etc.

And each kW of PV requires a kW of gas. Because making so much batteries that could provide a whole town/country the power at night is ... I don't know how to express myself properly... ludicrous. :D
Batteries are things for emergency backup for some devices and machinery untill the diesel generators kick in. Not for supplying the country during the night.

PV can not be an alternative source. Alternative means "to replace with", and they can not serve that purpose.
PV can only be a substitute and yes, I agree with using them as a substitute where and when viable in energy, economy and enviromental sense.
They are complementary energy sources and can not be the base od the power system. Ask anyone working in the energetics. They'll laugh at the idea of PV base system. Not because they're dumbasses with a habit, but because they understand the problems which are way more complex than we talk about here and deal with power grid stability (wind farms wreck havoc with power grids!). It's not just plug and play. People at electricity distribution centers work their asses off in winter and especially summer.

One of the biggest problems with PV, if you ask common folk that doesn't concern with energy and enviroment viability is economy. I don't know much about it, but as I've heard it's problematic.




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