two percent solution?

Glenn points out a fellow who notes the potential of solar energy:
“If 2 percent of the continental United States were covered with photovoltaic systems with a net efficiency of 10 percent, we would be able to supply all the U.S. energy needs,” said Bulovic, the KDD Associate Professor of Communications and Technology in MIT’s Department of Electrical Engineering and Computer Science.
Um, ok. Glenn notes “Two percent is a LOT of land”, but that’s understating the case a bit I think.
Let’s do some math! (I was told there would be no math. Shhh!)
According to this page, the total land area of the U.S. is 3,537,379 square miles. Take away Alaska and Hawaii to get the continental U.S., and you are left with 2,959,005 square miles. Two percent of that is…
Fifty-nine thousand, one hundred and eighty square miles. That’s 59,180.
For perspective: Over half of the fifty states are smaller in area than 59,180 square miles. The closest in size to that number are Iowa (55,869), Michigan (56,804), and Georgia (57,906).
So: who’s for paving over Georgia?
Because unless I’m missing something, that is what we’re talking about: literally paving over that much area, and I have to assume utterly destroying any flora, fauna, or other living things that are unlucky enough to have been previously occupying it. Unless they happen to, you know, not require sunlight.
Now that would be one hell of an Environmental Impact Study.
Professor Bulovic seems to have thrown out this statistic as a positive for solar energy, but he’s obviously never negotiated with a local zoning board. If that’s the best future we can hope for with solar as our primary energy source, I suspect even the most strident environmentalists will cry out, “Bring on the coal!”


Update: Commenter Eric points out that I shouldn’t be subtracting Alaska, as Bulovic said continental U.S., and he’s right. I’m not updating as the point is still valid (more so!)
Update: Lots of good discussion (and more math!) in the comments. And reader Ric sends in the following, which was a bit too HTML-heavy for the comments section:
Let us begin with data. The U.S. Energy Information Agency estimates total energy usage for the United States for 2004 at 99.74 quadrillion BTU. Converting to watt-hours using Convert.exe gives 29.23 quadrillion watt-hours. A quadrillion is 1015. To make things simple, round up to 3×1016 watt-hours.
The year is 365.242199 days long. If we divide that 3 x 1016 watt-hours by 365.242199, we get about 8.2 x 1013 watt-hours used per day. That energy must be collected while the sun is shining, of course.
The Solar Constant, the amount of energy reaching a flat surface perpendicular to the sun’s rays at Earth orbit, is 1.367 kilowatts per square meter. Atmospheric attenuation of incident solar radiation is from 30% to 90% depending on cloud cover. If we assume that we are in a sunny area with minimum attenuation, the amount of energy reaching the surface is 0.7 x 1.367 = 0.957 kw/m2 or 957 watts per square meter.
It’s fairly obvious that an array big enough to collect 8.2 x 1013 watt-hours is going to be too big to turn so that it always faces the sun. The United States is mostly well above the Tropics, so in order to get one meter of area perpendicular to the Sun’s rays we must have more than one meter of surface area; to be specific, the effective area is n cos alpha, where alpha is the latitude of the site. Most of the nice clear areas are in the desert Southwest, and a good average for the latitude there is 32 degrees. 957 watts per square meter times cosine of 32 degrees gives 811 watts per square meter.
The Sun rises and sets, and the angle of the Solar radiation varies according to a sine wave. Since we can’t move the array, we have to calculate the average energy arriving, which is 0.707 (root mean square of a sine wave) of the peak. 811 times 0.707 gives 574 watts per square meter.
If the solar collector is 10% efficient (we’ll get back to that) we thus recover 57.4 watts per square meter.
Checking the average hours of daylight we discover that the worst case is December, with only about 10 hours of daylight at 32 degrees latitude. Our solar collector has to keep up, so it has to collect the 8.2 x 1013 watt-hours in only 10 hours, at an average rate of 57.4 watts per square meter. That makes the area of the array 1.43 x 1011 square meters. That’s a bit over 55,000 square miles, close to what the Professor came up with.
And there are kickers.
Only 10/24 of that energy will be consumed as it’s generated. We have to store 14/24 of that for use when the Sun isn’t shining. 4.8 x 1013 watt-hours is a lot of energy to store.
Lead-acid batteries store about 41 watt-hours per kilogram. So we need about 1.17 x 1012 kilograms, or 1.17 billion tonnes, of lead-acid batteries to store the energy. Around 3 million tonnes of lead are mined each year, so that’s only a little less than four hundred years of world production. Lead-acid batteries in deep-discharge service last about five years, so the best way to maintain the array would be to round up to 1.4 gigatonnes of batteries; at any given time, 230 megatonnes of batteries would be undergoing reprocessing.
The EPA’s gonna love it, don’t you think?
Note that NiCADs are even worse. NiMH is better at 95 watt-hours per kilogram, but if you think lead is a problem, go look up nickel production. Lithium-ion is even better at 128 wh/kg, but if the production figures don’t give you pause you should look at the safety data pdf.
Oh, by the way, the power’s being produced in the Southwest. Power demand is largely in the Northeast. Add 20% (minimum) for transmission losses. Over that large an area, add another 10% for occasional cloud cover, and a further 20-25% for losses due to dust and dirt on the solar arrays.
And — those solar cells are 10% efficient, remember? Roughly 20% of the loss is in reflection, light reflected back into space from the array. The rest of it, 70% of the incident light or roughly 5.75 x 1014 watts, is heat. How much power will the fans to carry it away use? Will they have blue LEDs inside? Methinks the site will be popular with hang glider enthusiasts, provided they don’t mind being warmed a bit by the reflected light…
Do try to think things through a bit. Wishing isn’t physics.
Regards,
Ric

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67 replies on “two percent solution?”

  1. Be that as it may, that 2 percent includes industrial energy use. Maybe you should look closer at whether re-roofed family homes would be creating a positive surplus or not. Cause if so, all you’d have to worry about is industry and large buildings (which could also use more efficient systems still), which would change the economics of all our energy policies.

  2. People always seem to forget that power generation/transmission needs to match demand as closely as possible at all times. They get a little leeway from things like lightbulbs, etc, but power companies have to plan ahead and predict how much power they need to be generating at any given moment, and constantly adjust that amount or everything grinds to a halt. Individual homes or businesses can reduce the power they draw from utilities, run their own machines, or charge batteries or whatnot with solar power, but its inherent unpredictability makes it unsuitable for use by your local power company in anything more than a supplemental role.
    Because of this, numbers comparing possible solar power generation to generation by public utilities are generally pointless.

  3. Screwball: Agreed; I’m all for figuring out if there’s a way to replace existing roofing material with energy-generating stuff. Investigating that is obviously smart, and depending on if the economics work, possibly worth implementing.
    The 2% number simply underlines the fact that there is simply no way solar can ever be seriously considered as the primary energy source for the U.S. — unless we start talking about solar power satellites, which is another technology entirely…

  4. If you take out Hawaii AND Alaska, you have the contiguous United States. For the continental United States, you have to leave Alaska in.

  5. I don’t disagree with your calculation but I do disagree with the conclusion.
    There is about 3.5 million square miles in the US. But about 42% or 1.5 million square miles of that is farmland. Is it not quite easy to imagine a small percentage of farmland being turned over to energy production? In fact, it is already starting, with farmers scrambling to produce ethanol and biodiesel feedstocks. Ethanol is problematic, since it is not clear it produces more energy than is consumed in its production.
    Nevertheless, once the “Model A” of commerical solar collector is fielded, I predict that farmers will field arrays all over the country.
    Of course, we’ll see.

  6. A little more math. If each “average” roof of a residential dwelling was 2000 sq feet (usable and pointing towards the sun) that is roughly 0.0000714 or 7.14 to the -5th power square miles. You would need 22,756,947,899,159,664 (again, roughly) homes to make up the 59,180 square miles of solar collectors. I may have the math wrong, but I don’t think that there are any where near enough roofs.

  7. 1)This all assumes that solar energy can’t go above ten percent efficiency. Solar cells currently (no pun intended of cource) start costing a LOT more when you go for higher efficiency, but in the last few years some types with theoretical efficiencies of 50% or more have been demonstrated. Obviously there could be quite a gap between theory and affordable product, but the point is that amount of land used is not an inherent showstopper for solar.
    2) Solar power doesn’t have to come anywhere close to 100% of energy needs to be very useful in a variety of ways, including pushing down prices of other fuels by cutting demand for them.

  8. gmroper-
    Yes, I am afraid your math is wrong. Your 2000 sq feet of roof area (probably a factor 2 too high) is about 1/10,000 of a sq mile. So for a collecting area of 59,180 sq miles, you would need about 600 million homes (roofs). There aren’t that many, but as you can see it is not as large a number as you computed. More to the point, if you use other land, like farmland, it becomes more imaginable.

  9. Efficiencies slightly above 20% are common on satellites, I think. The panels are expensive, but currently available. Presumably cheaper if you buy in bulk. (If 59,180 square miles isn’t bulk, I don’t know what is.)
    As far as gmroper’s math, I get 824,921,856 homes.
    (As a sanity check, I think about the night time photos of the United States that I’ve seen. The lit up areas is probably comparable to Georgia.)
    That number makes this vaguely approach reasonable, when you consider there are a lot of large industrial buildings and Wal-marts that would also be in on this. And there’d absolutely have to be some non-solar power generation abilities for night time, anyways. There only needs to be enough solar to generate the difference between the daytime peak and the nighttime peak.
    There is also the possibility that less total power would need to be generated, since by distributing power generation to everyone’s roof, we’d be generating closer to the usage areas, and thus lessening transmission losses.

  10. There are about 350 Million homes in the USA and the average home size is 1350 sqft and if you add in the roofs of business and indusdiral you can almost get to the 59,000 sq miles you need….this is a viable option.

  11. According to U.S. Census data for 2000, there were about 100 million occupied housing units in the U.S. Assumming 1/2 of them face south, and assumming they can hold on average 1000 sq. ft. of collectors, we would end up with about 1,800 sq. miles of rooftop collectors.

  12. Vast areas of the western USA are semi-arid and government owned. Nevada is the best example: 48 million acres or roughly 75,000 square miles. http://www.blm.gov/nhp/pubs/rewards/1997/nv.html.
    You have to see it to believe how desolate it is.
    If the cost/KW for solar power were competitive, finding land is not such a huge issue. If the goal were huge centralized facilities, transmission infrastructure might be a significant cost.
    However, if it were cost effective, the most likely deployment model micro-deployment.
    There are roughly 78,000, 000 single family homes in the US. At 1,000 SF per, though would contribute over 3,000 square miles.
    Don’t forget the interstate highway system solution. If each right-of-way was a quarter mile wide, then the 160,000 mile system might contribute 40,000 square miles assuming the cost of the elavated scaffolding were not prohibitive.
    http://www.fhwa.dot.gov/hep10/NHS/index.html

  13. The total amount of surface area covered by man-made structures in the contiguous US is 43,480 square miles. That’s buildings, highways, parking lots, everything. That would be an area of solar panels that could cover every thing man has built in the US, plus many thousands of square miles extra, to give a better idea of the scale of the project.
    (The 43,480 figure is from this study: http://www.agu.org/sci_soc/prrl/prrl0423.html)
    And that’s not even considering the fact that solar is still many times more expensive than coal, and, ahem, isn’t very effective at night.

  14. Mr Harr, I believe you estimate of the number of American homes is a bit high. Recent news stories have been talking about the US population reaching 300 million sometime this fall. I don’t see how there could possibly be 350 homes amongst them.

  15. Steven-
    I believe the claim is that this will provide all of our US energy needs–it includes transportation (oil) which is the bulk of it.
    Presumably, the idea is that the collectors during the day make electricity, that in turn produces hydrogen.
    As to electricity: peak power production (daytime) is the greatest present need (which is reflected in the traded cost of electricity). As to nighttime, there are several competing technologies for energy storage. Solar is produced over a 4 to 8 hour span, on average, depending on where you are in the US. Storage has to be part of any commercial product.

  16. I agree with Robert–land cost is not a huge issue.
    A square mile, at 1/10 coverage and 20% efficiency (which I think is more realistic), could produce 50 megawatts of electricity.
    To be commercially viable, a large array would need to have a capital cost in the range of $1 to $3 per watt.
    At those cost levels per square mile ($50 to $150 million), the land costs of, say, $1.5 million is fairly trivial.

  17. This would work best for the English because “the sun never sets on the British empire.”

  18. Also, recall, photovoltaic cells would have to be kept clean. Clean of snow in winter. Clean of dust in summer. Clean of calcium left behind by rains.
    The third largest killer in the US is accidental falls. Think: who is going to clean these surfaces? How often? Where are they going to stand when they clean it? How many old folks are you willing to lose from falling off the roof as they try to clean up the panels? How many old folks will add to their winter chores like shoveling the walk, and shoveling the driveway?
    Put up a ladder, then shovel the roof while you stand on an icy sloped surface 12 to 20 feet above the ground. Right. Undertakers would experience a boom in their business.
    If I was to design or build a new house, I would think about adding some photovoltaic cells to the roof, located about shoulder distance above a flat roof, tipped a bit toward the sun. For us to make significant progress toward solar power using roofs, we would have to scrap most of our investment in houses, to build the “new solar house”.
    Not a quick solution anyways.

  19. Also, recall, photovoltaic cells would have to be kept clean. Clean of snow in winter. Clean of dust in summer. Clean of calcium left behind by rains.
    The third largest killer in the US is accidental falls. Think: who is going to clean these surfaces? How often? Where are they going to stand when they clean it? How many old folks are you willing to lose from falling off the roof as they try to clean up the panels? How many old folks will add to their winter chores like shoveling the walk, and shoveling the driveway?
    Put up a ladder, then shovel the roof while you stand on an icy sloped surface 12 to 20 feet above the ground. Right. Undertakers would experience a boom in their business.
    If I was to design or build a new house, I would think about adding some photovoltaic cells to the roof, located about shoulder distance above a flat roof, tipped a bit toward the sun. For us to make significant progress toward solar power using roofs, we would have to scrap most of our investment in houses, to build the “new solar house”.
    Not a quick solution anyways.

  20. I hate to sound like Kos, but screw solar. We need more nuclear plants, and we needed them 10 years ago. Why are we to the left of France (who get almost all their power that way) on this issue?

  21. Your 2% figure is also helpful in accessing the practicality of ethanol since the total energy gained from a crop used to produce ethanol can’t be larger than the total solar energy that falls on it.
    Given the real energy inefficiencies of production it is clear that the ethanol push is nothing more than a giveaway to big agriculture.

  22. I haven’t kept up on the technology as much as I should, but I use solar to heat the pool and jacuzzi, (trust me, the results are not as great as the salesman promised), and the surface area required is just about as large as the pool itself. Also, due to the blasted roundness of the earth, keeping a consistent temperature is impossible. I somehow doubt that remarkable progress has been made in the two years since I installed the system.
    BTW, “This would work best for the English because “the sun never sets on the British empire.”, is the funniest thing I’ve read all day. I assume, by extension, that all solar panels in Japan must face east.

  23. There are lots of problems with the statement in question. First, let’s throw out the contention that we have or want to have ALL our power come from solar. Of course, we don’t! It’s dangerous for a country this size to depend on one source for anything. Besides, Dale makes a great point: “Solar power doesn’t have to come anywhere close to 100% of energy needs to be very useful in a variety of ways, including pushing down prices of other fuels by cutting demand for them.”
    Second, even if we covered 2 percent of the country with solar cells, that takes care of only part of the problem. As others have pointed out, those cells have to be cleaned and maintained. Power needs at night can’t be met unless the panels are combined with energy storage of some form. And there’s the question of getting the power from the source to the need, and the loss that always occurs in that handoff.
    One naturally thinks of space-based collectors, but costs of installation and maintenance, not to mention how to get the juice back to Earth, constitute major roadblocks. I wonder if offshore solar collectors might be a partial answer. We already get oil and gas from offshore, so perhaps solar collectors could turn sunlight into hydrogen using available water. The hydrogen would then be shipped to wherever the power was needed.
    In relation to this, the NY Times recently ran a piece on various efforts beginning to get serious attention, to combat global warming by reflecting the sun’s rays back into space through various means. Certainly a bunch of large offshore solar collectors would have a modest impact in this regard.
    All our energy comes from solar already. We rely on the middlemen of coal and gas to provide us with it. Solar power is all about eliminating the middleman.

  24. It’s worse than that.
    Since the solar energy is intermittent, most of it has to be stored as hydrogen or something similar.
    Typically the conversion efficiency is 50% or worse.
    Then you have to convert the hydrogen back to electricity. Again the conversion efficiency would be lucky to be 50%.
    So it’s not really 2% of the US to pave over. It’s more like 8%. And it’s worse than that too. You have to account for the enormous energy investment in paving 8% of the US with solar panels; of building tens of thousands of miles of hydrogen pipelines; of building hydrogen conversion and generating plants…
    It is possible that Prof Bulovic factored all this in, but I doubt it. I would be interested to know.

  25. There are about 350 Million homes in the USA and the average home size is 1350 sqft and if you add in the roofs of business and indusdiral you can almost get to the 59,000 sq miles you need….this is a viable option.
    …but only if the sun shines 24 hours a day.
    Vast areas of the western USA are semi-arid and government owned. Nevada is the best example: 48 million acres or roughly 75,000 square miles.
    And they’re occupied by all kinds of endangered species, like the desert tortoise. Good luck winning all the lawsuits brought by environmentalists.
    There is about 3.5 million square miles in the US. But about 42% or 1.5 million square miles of that is farmland.
    Sorry, not even close. About 18% of American land is arable according to the CIA World Factbook.
    As to electricity: peak power production (daytime) is the greatest present need (which is reflected in the traded cost of electricity). As to nighttime, there are several competing technologies for energy storage. Solar is produced over a 4 to 8 hour span, on average, depending on where you are in the US. Storage has to be part of any commercial product.
    Peak power production in winter is about 7 PM, after the sun sets.
    And there’s no way I know of to store that much energy over the course of 8 hours and then to convert it back to electricity over the next 16 hours. Yes, “storage has to be part” of this, but I don’t see how it will be done. Making a million times as much solar cell surface area as has been made total up to now is the easy part.

  26. Ah, heck, the comment system stripped out all my italic tags, making it impossible to differentiate the stuff I was quoting and the stuff I myself said. grumble…
    The underlying commentary here is, “This really should be easy. All we have to do is thus-and-so and then take care of a few measly details, and then the problem will be solved.”
    Mencken said, “There is always an easy solution to every human problem — neat, plausible, and wrong.”
    This is **not** an easy problem susceptible to an easy solution.

  27. “You have to see it to believe how desolate it is.”
    That’s what they say about the Coastal Plain of ANWR. Proposed development there would amount to 3.13 square miles, or roughly 0.005% of the area solar would (hypothetically) require. But we’re told over and over again that that’s just too much land to risk for copious domestic oil; so I have to believe that 19,000 times as much land is an even bigger risk.

  28. Besides, all those shiny solar cells might appreciably up the albedo of the Earth — giving a help on the ol’ Global Warming thing.

  29. But, on the other hand, if I put photovoltaic on MY roof, I can install a two-way Edison meter and Edison will send ME a check every month.
    Round numbers:
    Cost of PV system: $20k
    Tax credits: $10k
    Edison Bill: $90 month
    x12 months
    ==========
    approx $1000 per year
    Ten year return on investment,
    plus “Screw the Terrorists!
    The high prices are just the producers gaming the system. They can only game the system when demand is within 3-5% of supply. Then, they play with the supply and we get screwed. If we drill in Alaska, offshore, get Iraq pumping, Libya pumping, plus Nigeria and Venezuela might get straightened out. We have a glut of enery.
    Let them eat sand.

  30. The 42% of US land in farmland came from a website that compiled farm statistics:
    http://www.nemw.org/farmland.htm
    Of course, the CIA factbook number may be correct. But for purposes here, 18% or 42% doesn’t make for a showstopper.
    As to storage, among other technologies see
    http://www.premiumpower.com/. Pumping water vertically for later hydro conversion is also used for energy storage.
    As to peak electrical demand, I was referring to summertime and AC usage. Your point about wintertime peak demand is interesting.
    I don’t see commercialization proceeding via rooftop installation. Large arrays will be maintained by utilities.
    I agree completely that solar is not the whole solution. Absolutely, we need to expand significantly nuclear power usage. If nothing else we need to build new nuclear plants just to replace the very old ones we have presently.
    In the end, these things will either be commercially viable or not.
    Peak oil and later peak natural gas will force many changes. None of them will be immediate or easy.

  31. See any of several books by Vaclav Smil of MIT for more information on comparing various forms of energy. I especially recommend “Energies” if you are reasonably numerically astute (like simple algebra). It is full of carefully crafted energy equivalents and cost estimates. The short answer is that in the foreseeable future solar will only be a part of our total energy budget.

  32. Setting these up offshore on the equator producing hydrogen would eliminate the loss of arable land issue. At any rate, we need a combination of many sustainable energy production methods. Wind is another way of harnessing solar energy that is becoming more cost effective each year. In Texas and New Mexico, turbines are popping up at an significantly accelerating rate.
    Why not go for solar micro-power on rooftops, wind energy in isolated areas in the Midwest, and radical increases in efficiency. The US has embarrassing fuel efficiency requirements, and our coal fired plant are significantly inferior to the tech used in Europe now. Even China has much better fuel effciency requirements than the US! Your elected offical who sold out to cro-magnon Detroit is to blame.

  33. I cannot see this as a singular solution.
    To me, there has to be a blend, or conglomerate, solution.
    Solar, Wind, Geothermal, Hydrogen and Nuclear.
    The first two are sporadic. The rest are not.
    We fell short by not devising a national design plan years ago.
    We have to diminish the span of time (and permits) that it takes to create and build more energy producing plants.
    Period.

  34. hmmm, is not 66% of the world covered by water? While it would be a construction feat that would dwarf the Panama canal in scope, I dont actually think it would be harder to execute than the Panama canal. Build a floating island of modular units which can gather tidal, current, or wave power, while gathering solar power from the top side.
    Surely we can find somewhere in the atlantic that blocking out a Georgia or 2 size area from sunlight will not adversely effect the environment, if not, we can build it as a matrix and expand the square miles as necessary. An initial funding of say, 100 or 1000 square miles (whatever the bean counters determine the breakover in maintenance costs is) should let it establish itself and grow from its own profit.
    with all that said, the whole thing would probably be better if it was distributed in small chunks across roof tops or small sun farms by individuals…hmm, if they could create a material that also made a decent driving surface they could get dual use out of roadways.

  35. Energy production and policy has become something of a fun sport for me the past few months, and I could not resist running the numbers as I have been grinding through them at a fair clip for a few months, now.
    This is dull, but goes through it all: http://ajacksonian.blogspot.com/2006/07/nanotechnology-to-energy-rescue.html
    If you hate math, going through conversion factors and all that fun stuff, here is the upshot:
    Insolation for the 2% of US is 2.67 E14 kWh/yr
    Take 10% and you get 2.67 E13 kWh/yr
    Total energy consumed by the US in 2004 2.92 E13 kWh/yr
    So within the ballpark *if* you can make an industry that will actually deliver that. And this is the total energy use of the entire United States from all sources, including current electrical systems. For 2004. The use trendline is *up*.
    The only place to really put this, however, is where the sun shines 24 hours a day (give or take on orbital mechanics and such), which is space. Either doing this on Earth or in space requires a heavy industrial retrofit to the Nation, or a new industry from space based sources, not only for storage and distribution, but for moving slowly away from other sources of energy. The ramp up speed seen with the current photovoltaic industry has been miniscule, even for anamorphic crystals, compared to National need.
    For those looking to any bio replacement, I have run the numbers hard on those. Just for gasoline we need 125 billion gallons of gasoline. Brazil produces 4 billion gallons of ethanol and uses up tropical rainforest at a harsh rate to do so. The conversion rate of sunlight to ethanol is about 9.39% *before* cost of retrofitting pipelines and distribution systems is included and actual transport is also included. Somehow trading middle eastern petro authoritarian regimes for unstable third world agrarian regimes does not seem really impress me. Also, that is with *corn*, for sugarcane the actual percentage drops, although the production is annual and not seasonal.
    No matter which way you turn there are problems. Choose a new method and you require a major National retrofit, even if it takes decades. And if you choose an terrestrial solution, the NIMBY and BANANA folks will be lodging all sorts of things to make sure everything is done just right, out of sight, out of mind, don’t ruin the visual ‘viewshed’ or be sending too much money to one group over another… and I can hear the charges of exploitation of 3rd World Nations if you go ‘green’… mmmmmm… loverly, these folks that want to live in caves.

  36. And how much maintenance work will something the size of Georgia need each year?
    Will these cells be mounted on sun trackers? If not, are you sure they’ll hit 10%? If they are, how many billion motors have to be checked each day, and how many million have to be replaced each year? How many square miles of cells will have to be replaced each year due to natural wear, tear, and damage from things like hail?
    Heck, by the time you get done designing the arrays, finding the land, creating the magical multi-TwH storage/generation system for overnight, and figure out how to load-balance with the grid, you might as well put the whole thing in space and hope that laser or microwave power transmission keeps increasing in efficiency and launch costs drop by a few orders of magnitude. 😛
    Solar has *a* role. That role is not going to be primary for some time to come. Same thing with wind. The controllability and order of magnitude just isn’t there.

  37. I’m amused that people who think building nuclear power plants is an environemtal disaster have no problem with covering the earth with windmills and photovoltaic systems.
    So how many species will die as a result of this massive change to the surface of the planet?
    I’m reminded of 1970s “split wood not atoms” environmentalism. The cure is worse than the disease.

  38. I’ve seen a couple cases where solar is great… on a small scale. An individual house can run at near break-even, despite the hefty costs of the storage device and .
    But you need backup for nights and winter (cloudy cover isn’t as harmful as you’d expect, strangely), which means either a huge battery (bad chemicals, extra cost), or a power network you can tap into. A global network can’t really ‘tap into’ anything.
    Oh, and a couple things I don’t think anyone else has picked up on yet…
    First, you can’t just pave over Nevada and be done with it, simply because power distribution doesn’t work in your favor. You have to ramp voltage up and down too often, and line inefficiency starts to be killer.
    Solar panels have a short lifetime, average of ten years. Imagine replacing 2% of the continental US every 10 years.
    They are really nasty for the environment. All of the efficient (greater than 5%) tend to involve the use of caustic chemicals. Big no-no.
    I say go nuclear, with hydrogen for small-scale or for transportation. Sure, it’s not efficient… but we’ve got enough power to last us til we can go hydrogen (and that should last us til the sun burns out). Make some reactors to transmute the transuranics back down to (unfortunately useless) uranium isotopes, drop ’em where we mined the uranium from, and we don’t even have to bother with spent fuel repositories.

  39. In fact, that’s about 38 million acres. Given that the sun doesn’t shine all day and other factors, that 10% net could be high. It’s not clear, though, as some uses (A/C, store and office use) are largely coincident with sunlight.
    SO, it’s unlikely that you gat everything from solar. But you could get a great deal from solar, and in economics margin is everything. Drop US oil imports by 20% and prices crater.
    Of the available alternative methods, solar has quite a bit going for it. It is about break-even over time, economically, and is HERE, which a lot of other things aren’t (hydrogen) or politically acceptable (unlike nuclear).
    People I know who have done the grid-connected solar thing are quite happy, having insulated themselves for 20 years from any electricity rate increases at a small present disadvantage. A good deal, unless you expect energy prices to fall soon.
    Yes, it isn’t for people in Buffalo with trees blocking their roofline, and zoning people can be such fools, but it is definitely worth looking into.
    So is nuclear, but that’s trying to “ride the horse sideways” right now.

  40. Blueyes–
    No one who is connected to the grid now uses a storage battery with solar. You feed into the grid in the day, and take back at night, with the meter running the same rate both ways. Usually you break even or better. Most modern panels last much longer than 10 years, BTW. The cost of installation is about 7 or 8 years electricity given the available subsidies (which you and I pay for). Even without the subsidies it’s 10-12 years power cost. You aren’t going to get rich at it, but it is HERE and NOW and an economic push.
    Again, you don’t have to replace all the US’s energy with it. 5% would do wonders to prices.

  41. A mention of margin being everything in economices brought me to this stream of thought.
    Cycles are everything in economics. If we were to develope cold fusion and everyone had thier very own “unlimited” power source, I think that we would find ways to use that power, and eventually find ourselves at the same quandary that we are at today, searching for more power or more of the commodity that supplies that power.
    If we did have cold fusion, from a ubiquitous commodity, we would develop air thrust flying cars, or anti-gravity flying cars that used tremendous amounts of power to manipulate the magnetic field. All I am saying is that if we had cheap energy we would use that energy to raise our standard of living until the energy wasnt so cheap, so I guess the trick is to develop energy generation technology which has long wavelengths from crest to trough between the golden age and the dark age, and then be born early in the golden age.
    Or engender innovation so that golden ages are expanded with new technology.
    There is no holy grail of energy creation.

  42. Lets not forget that there will be substantial savings in efficiency by generating the power locally (no transmission losses for homes or small businesses) and also by conversion of the bulk of transportation (presumably) to electrical based technology (several times more efficient than internal combustion technology). So it is likely that the 2% number is too high, and 10% efficiency is too low to a goal to shoot for. Conventional cells do that now.
    Combine that with wind and nuclear, along with clean coal and biomass, and you can put a real dent into the problem.
    You could store some energy by pumping water uphill etc.

  43. There will never be a “hydrogen economy.” It’s a scam. Don’t buy into it.
    There is no such thing as a “tank” or “pipe” for hydrogen, only various densities of filters. The hydrogen molecule is so tiny that it worms its way through the spaces between atoms of any other material to escape — and many of the escaping atoms form unnatural partnerships, called “hydrides,” with the material they are passing through. One of the characteristics of hydrides is near-zero mechanical strength, so the container gets brittle and weak.
    The problem is made worse by the low energy density, which necessitates either extremely high pressures or cryogenic techniques to cram the stuff into a small enough space to be useful. High pressures aggravate the leaking and hydride-forming problems, and cryogenics have costs (including some fairly hideous dangers) all their own.
    The only reliable way to confine hydrogen is the ball-and-chain technique: anchor it to something big and heavy so it can’t float away. The ideal thing to use for a leg-iron is a carbon atom. Benzine/hexane, heptane, and octane have a lot of energy per unit mass/volume and are liquids, easy to confine, at most normally-encountered temperatures and pressures.
    Uh-oh. Did I just reinvent hydrocarbon fuels? Yep. They weren’t picked in the first place for their delightful aromas.
    Regards,
    Ric

  44. I don’t think the 2% number is correct. The last time I worked it out I came up with a land area the size of New Mexico. Might want to figure it out from the bottom up.

  45. There’s an awful lot of fancy figuring going on in this post and all the comments.
    Y’all are way smarter than me.
    The one thing I haven’t seen anybody figure into the equations is how y’all are going to get ME out of MY house to pave over MY property.
    THAT could get right costly …..
    🙂
    PS – We Georgians like our 2nd Amendment rights – so immenent domain won’t cut it 🙂

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