Enough sunlight strikes unshaded U.S. rooftops to replace all the coal and some of the natural gas we use to make electricity. Backup via ground source heat pumps, and smart grid technology would allow this variable energy source to displace base-load coal with today's technology. Whether this is the most cost effective way to displace coal is another question. Also rooftop solar is a silver BB rather than a silver bullet: Even after massive efficiency improvements we will need to get many times the power from non-rooftop sources than from rooftops.
According to a 2003 study by the Energy Foundation (PDF), solar PV that converts 15 percent of sunlight to electricity could produce 710,000 Megawatts on rooftops that will be available in 2050. Doug Wood thinks that with concentrating PV using advanced aerospace quality cells we could convert solar at 30 percent rather than 15 percent efficiency. Scaling back to rooftops available today (using 2003 numbers from the same study and extrapolating forward) we could produce around 1.05 billion megawatts today. We normally assume 22 percent capacity factor (PDF) for PV. So that would give us about 2.3 billion megawatt hours, or around 56 percent of today's electrical production -- more than coal provides.
Further, waste heat from this process could provide much of our heating and cooling needs as well. The EF study I cited suggests that about 65 percent of commercial roof space is unshaded compared to about 22 percent of residential roof space. Since some commercial scale chillers run on low to medium temp heat today, with enough storage solar CHP could provide close to 100 percent of commercial heating and cooling. But that much storage takes a lot of capital for a small incremental gain. So more realistically, we would put 16 to 24 hours of low temp Phase Change Material storage and use ground source heat pumps to provide the other 15 percent of low temp needs. As a side effect, the overnight storage would let us run those heat pumps when the electricity was cheapest -- which will prove more important than it might appear at first glance.
The comparatively low mount of residential roof space available means you will only have 200 to 300 square feet of unshaded roof space available per home on average. I don't know if this means some houses provide a lot of available solar space, and others with none or if this is distributed more or less evenly per home. Even in the latter case, you will have a certain number of unshaded south walls, and a certain amount of yard space that could be devoted to solar generation. To be conservative, let's say that 40 percent of residential space heat and hot water could be provided as a side effect of concentrating PV electricity generation. Again, let's add PCM storage and the other 60 percent with ground source heat pumps.
This is for existing buildings. New buildings could be designed to use 70 percent to 80 percent less energy through a combination of better insulation and sealing, passive solar, more efficient air exchange, and more efficient lighting and appliances. New buildings could also optimize the amount of solar oriented unshaded roof space.
Now, since we are talking concentrating PV, we would have almost no control of when it would be generated -- mostly during the five peak hours of sunlight except when it was cloudy. However, we are assuming all space heating and cooling other than solar is switched to ground source heat pumps with PCM thermal storage. So when solar electricity was produced at a time it was not needed, it could run heat pumps to generate heat or cold in storage for climate control systems to draw on later.
Sixty percent of 2005 residential heating and cooling was about 5.7 quad. Fifteen percent of 2005 commercial heating and cooling was about .6 quad. Without climate control efficiency improvements a climate control storage would let a smart grid absorb around 85 percent of solar electricity. If insulation and other improvements reduced climate control in existing buildings about 40 percent, climate control needs could still absorb about half. If we reduce climate control demand further, industry could add PCM and heat pumps to absorb pretty much as much of this as needed. Industry consumes about 33 quads. About 70 percent of this is used by boilers, and about 35 percent of boiler energy is used to produce process heat below 700 degrees Fahrenheit. That is 8 quads, or more than the total solar energy that would be produced. Because lower temperature heat is cheaper to store than high temperature, the high-end of this would be a last resort; climate control would be the cheapest form of energy to store, followed by hot water at or below the boiling point, followed by hot water at not too much above the boiling point. Between residential, commercial, and industrial hot water I suspect we could place most of what space heating did not require without ever needing storage above the boiling point or below the freezing point of water.
What is the bottom line on coal displacement? It would save slightly more electricity than we currently produce via coal, plus around as much again in displace climate control, hot water and low temp water heat. A small amount of this could displace coal use directly. But the majority would displace natural gas currently used for electricity production, climate control, hot water, and process heat. That natural gas in turn could be used to replace coal for base load, as a first step towards phasing out all fossil fuels, with a bit left over to contribute to phasing out oil. In other words total non-solar electricity generation would go down, even with increased demand to run heat pumps, while natural gas currently used to heat buildings would be available for electricity generation. We could completely replace coal based electricity generation with natural gas, and have some natural gas left over.
A very productive short-term use for this extra natural gas would be to make diesels more efficient. Running diesels mostly on natural gas has been very disappointing in practice. Natural gas powered buses, trucks and so on have lost so much in efficiency that you end up gaining little if anything in vehicle miles per Btu. But something has proven better: Take a diesel engine, and inject natural gas equal to 5 percent or 10 percent of the diesel fuel used into the engine. A minor effect is direct fuel replacement. But a major effect is that this natural gas helps burn the diesel fuel much more completely; the oil is more completely consumed. This can boost total energy efficiency by 30 percent to 40 percent. From a greenhouse standpoint the results are even better. Black carbon from diesel is essentially unconsumed diesel. Burning diesel fuel more completely reduces black carbon by much a much higher percent than it reduces energy consumption. Natural gas injection is a comparatively inexpensive modification of a diesel engine -- one we could make to trucks or better still to rail locomotives.
Now physically possible is not the same as feasible. Doug Wood makes a good case for concentrating PV being pretty cheap in actual cell and parts cost. But he does not estimate labor, which in conventional PV is around 2 dollars a watt, or framing material for attaching PV to a roof, which can often run a dollar a watt. Installing a ground source heat pump under favorable circumstances (meaning you have enough land to only need to bury it at a depth of five feet) in a typical U.S. home is around $15,000. Commercial ground source heat pumps can take advantage of certain economies of scale, but they also almost always have to be buried deeper.
Rooftops are not the only pervious surface, but they are the main ones that let us do co-generation. What about parking lots? Well the problem with parking lots is that since you don't already have a roof, you need to build one. And since existing parking lights are installed on the assumption of no roof, you need to install new parking lights as well. A roof strong enough to hold concentrators and panels (meaning not a low end carport), plus reinstallation lighting would have to run $15-$20 per square foot before you put in mirrors and PV cells. But maybe I'm overlooking some way of doing parking lot power (and road power) cheaply.
Right now it looks to me like two things are true. Roof top power has a lot more commercial potential, potential to be done cheaply, than is apparent at first glance. But rooftop power will never come close to providing the majority of our needs.
Copenhagen, U.S.A. December 7
Comments
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green8659 Posted 3:57 am
30 Jun 2008
Green | Bowtrol Cleanse | Web Design Indiana
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Jon Rynn Posted 4:33 am
30 Jun 2008
Rooftop PV could all by itself replace coal.
The heat that comes from the PV solar cell s(cogeneration) could provide much of the heating and cooling. 85% of commercial heating and cooling could come from this, with the other 15% from geothermal -- assuming that you are using storage that is fairly cheap, such as phase change materials (PCM). PCM, according to wikipedia, changes a solid to a liquid when it is heated, and when it moves back from liquid to solid, it gives back some of the heat.
This heat, in residential housing, could provide about 40% of heating -- but not cooling as in commercial establishments, because converting heat to cold involves large machinery that only makes sense in large buildings (although this could work in apartment buildings, no?). For residences, the other 60% might come from geothermal.
The geothermal could be powered by some of the PV energy, stored in PCM -- at least, I think that's what you were saying -- can the PCM be used to generate electricity for the geothermal heat pumps?
I'm not sure what you were getting at in the paragraph about quads -- are you saying that some of the PV could be sent back onto the grid, as a way to store it? Or were you saying that the industrial processes below 700 degrees could be run via PV as well?
One other thing -- I think with any kind of decent building density, you would send the geothermal pipes down at least 100 feet, which would be a better long-term solution than just 5 feet, if I understand the technology.
I think that this is the direction we should be going -- thinking about using buildings in addition to the grid to generate most of our energy needs.
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Erik Hoffner Posted 4:45 am
30 Jun 2008
Erik
The Orion Grassroots Network: 1,200+ grassroots groups working for conservation & more
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Jon Rynn Posted 4:50 am
30 Jun 2008
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sunflower Posted 5:01 am
30 Jun 2008
Consider tracking from the ground if space is available.
Fixed latitude +15 degrees
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/ ...
Single N-S axis tracking latitude +15 degrees
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/ ...
High-intensity pv implies 500+suns from point focus concentrators such as a dish or Fresnel lens
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/ ...
Think of a 12 foot diameter C-band TV satellite dish in the yard on a pole, or on a load bearing wall, or many poles over parking lots, along roads, brown fields, and so on.
I rough numbers, a 13 m2 dish would cost $700 materials, $600 labor, and require <200 cm2 type III-V 40% efficient cells at something like $10/cm2 ~ $2000. $3300 for about 4,000 Watts(e) installed system at scale without margin plus inverter and cooling. Type III-V cells are used on the Mars rovers.
Something more aggressive for return on investment is concentrator cooling (displacing electricity) with steam absorption chilling (saves $2000 on cells).
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Jon Rynn Posted 5:16 am
30 Jun 2008
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GreyFlcn Posted 5:39 am
30 Jun 2008
Would a "heatsink" on the solar panels increase their efficiency significantly?
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Erik Hoffner Posted 6:04 am
30 Jun 2008
Erik
The Orion Grassroots Network: 1,200+ grassroots groups working for conservation & more
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sunflower Posted 6:14 am
30 Jun 2008
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amazingdrx Posted 6:20 am
30 Jun 2008
It was in one of your earlier articles, one of the best threads ever! Great job once again.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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amazingdrx Posted 6:22 am
30 Jun 2008
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Jon Rynn Posted 6:24 am
30 Jun 2008
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Jon Rynn Posted 6:34 am
30 Jun 2008
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amazingdrx Posted 6:34 am
30 Jun 2008
It will look like a furnace and connect to solar panels, plumbing, heating, electric outlets, power grid. The builder will just put it in and hook it up.
Buy "Alamagamated Renewable Hotcakes Prefferred" (what Vonnegut might call it?) now, sell into the boom.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Gar Lipow Posted 6:51 am
30 Jun 2008
No stored in the PCM as heat or cold.
> I'm not sure what you were getting at in the paragraph about quads -- are you saying that some of the PV could be sent back onto the grid, as a way to store it? Or were you saying that the industrial processes below 700 degrees could be run via PV as well?
The latter. Industrial processes under 700 F, ideally under 212 F could use PV electricity to generate that low temp heat, and store the heat into Phase Change Materials until needed (within 16 to 24 hours, not long term). The reason 212 F is preferable is that as the temperature you store rises, it gets more expensive to store the heat.
The point is that if you want to use variable electricity without electric storage, then you have to be store the product, and the product has to be something that is cheap to store and that makes thermodynamic sense to use electricity for. Cheap to store pretty much means low temperature heat or cool. Using expensive electricity for direct resistance heating is thermodynamically wasteful, cause you are turning high quality power into equal amounts of low quality power. So if you need to use thermal storage to store electricity, the only way it makes sense is if you use that electricity to run a heat pump so that you can back multiple units of heat or cold for each unit of elecricity input. This is call a co-efficient of power or COP. But the higher or lower the temperature rises the lower that COP is. So for heat pumps to gain you much you want the temperature you are storing to range from not too much below the freezing point of water to somewhere to well below the boiling point of water. Industrial demand in that range is very low, but after domestic and commercial space heating, space cooling, and hot water are considered, industrial low temp uses probably could make use of enough heat and cold in low temp ranges to absorb the remaining variable electricity. I think a couple of percent of industrial energy goes to compressed air, which could be another part of the "store the product" game. But remember, this is with only half our electricity coming from variable sources. Much past that and we need to start storing some of the electricity itself.
If we start increasing industrial efficiency greatly and then substituting electricity for most of remaining demand then you are going to increase the need for dispatchable, not variable electricity. (Note that electrifying indusry is done not by direct substition of electricity for fuel, buy by substituting process that can be efficiencly driven by electricity for those that depend upon high temperature heat.)
I have a humongous spreadsheet where I've put together actual scenarios and costs - that is how much it would cost to get off of fossil fuels with no technical improvements and with varying degrees of breakthroughs under various efficiency scenarios. The rest of the week is going to be dead for me as far as Grist goes, cause I've got some deadlines, but I'll try to clean up the spreadsheet so it that it plays well with others and put a narrative in front of it sometime next week
Bear in mind that is post outlines a maximum from rooftops. I was able to apply a few filters to cut out some obvious no-gos, but there are all sorts of gotchas it did not deal with. This should not be looked upon as feasible proposal, but as a limit on rooftop power. A realistic estimate of what we could gather from rooftops will be much lower. But you could take these numbers, add some realistic constraints and come up with the real potential.
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Jon Rynn Posted 7:12 am
30 Jun 2008
And just to clarify, from my spreadsheet, looks like about 20% of natural gas is used for industrial boilers and process heat, so I suppose that could be replaced eventually by renewable electricity.
Thanks, Gar, and I look forward to your public google spreadsheet.
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Gar Lipow Posted 7:38 am
30 Jun 2008
Well ultimately we will need more than a little. But in this context, if this is all we do, no. Because we are phasing out coal. It does not yet phase out natural gas powered electricity. It phases out most peak and load following, with some reduction in baseload, but not all that much. So, say one half of coal baseload is directly replaced. The rest gets replaced by using the natural gas we save to replace that baseload. (We have two source for this. A lot of the natural gas we currently use for peak and load following will be available to run base loads instead. And of course 100% of the natural gas we use to run space heat and hot water will be available to run baseload electricity.
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Jon Rynn Posted 8:00 am
30 Jun 2008
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Gar Lipow Posted 8:01 am
30 Jun 2008
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Jon Rynn Posted 8:18 am
30 Jun 2008
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Colin Wright Posted 2:18 pm
30 Jun 2008
Exactly right about storing solar. Here is Cambridge physicist David MacKay [pdf](thanks to JMG's recent post) on limits to ground source heat pumps:
Can everyone use ground-source heat pumps, without using the summer replenishment trick? A calculation on p.348 gives a tentative answer of no: if we were aiming for everyone
in the neighbourhood to be able to pull from the ground a heat flow of
about 48 kWh/d (my estimate of our typicalwinter heat demand),we'd
end up freezing the ground in the winter. Avoiding unreasonable cooling
of the ground requires that the sucking rate be less than 12 kWh/d.
So when we switch to heat pumps, we should plan to include substantial
summer heat-dumping in the design, to refill the ground with heat
for use in the Winter. This summer heat-dumping could use heat from
air-conditioning, or heat from roof-mounted solar water-heating pan.
Alternatively, we should expect to need to use some air-source heat
pumps too, and then we'll be able to get all the heat we want - as long
as we have the electricity to pump it. In the UK, air temperatures don't
go very far below freezing, so concerns about poor winter-time coefficient
of performance of air-source pumps, which might apply in North
America and Scandanavia, probably do not apply in Britain.
Nay-sayers object that the coefficient of performance of air-source
heat pumps is lousy - just 2 or 3. But their information is out of date. If
we are careful to buy top-of-the-line heat pumps, we can do much better.
The Japanese government has legislated a decade-long efficiency
drive that has greatly improved the performance of air-conditioners;
thanks to this drive, there are now air-source heat pumps with a coefficient
of performance of 4.9; these heat pumps can make hot water
http://www.ecosystem-japan.com/ p.148, part 1 Energy
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amazingdrx Posted 2:26 pm
30 Jun 2008
Yeah Jon plug in this Audi, 60 mile range on plugin. Perfect.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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amazingdrx Posted 2:37 pm
30 Jun 2008
Natural gas would be freed up by geo heat exchange heating. And by solar furnace industrial process heat. Biogas from waste could act as backup for the grid, run through distributed generators, that could be mainly (much more efficient and less costly) solid oxide fuel cell/turbines eventually.
Baseload power from coal and nuclear will fade into the grimey past.
Battery storage in buildings and plugin cars can give emergency resilience to a distributed smart grid. if you are not careful you can fall into the baseload, centralized always cover the maxiumum possible load, 100% dispatchable fallacy.
This just isn't what the grid will need to be as it transitions to full renewable distributed generation and storage.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Biodiversivist Posted 3:00 pm
30 Jun 2008
In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world
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vakibs Posted 9:59 pm
30 Jun 2008
Ofcourse, solar is amazing. But can PV rooftops alone replace all the coal ? US relies on coal for 23% of its energy use currently. This is bound to increase with the popularity of electric vehicles.
For photovoltaics, 30% is an improvement over the 20% efficiency that is available in the market. But can these panels be mass produced to cater to all the rooftops in the USA ?
Eliminating rooftops not facing southward, and those which lie in shade, how much rooftop area can be reasonably provided per person in the USA ?
David MacKay has done such an analysis for Britain (Britain has a higher population density than USA) and allocated 10 square metres of solar PV rooftops per person. In the post above, the author assumes 300 sqft = 28 sq meters per American home. It should translate to not more than 10 sq mt per person.
MacKay concludes that solar PV over rooftops could obtain just 4 KWH per person per day in Britain. Indeed, a similar analysis for solar thermal heating over rooftops produced a better figure of 10 KWH per person per day.
To put this number in perspective, Average American energy requirement is 300 KWH per person per day. In this, coal accounts for 23%, that is 70 KWH per person per day.
Even after increasing the efficiency of solar panels from 20% to 30%, their effect would be limited. I cannot expect more than 15 KWH per person per day. How can one make such an irresponsible claim that solar PV rooftops replace coal ?
I would be glad if somebody does the arithmetic for USA and rebuffs MacKay's argument. But I think it is unlikely. This is even before we take into account the economical cost of laying solar rooftops over all houses.
Looking at the solar cheerleaders in the comments, I get an impression that they love natural gas more than solar itself. How can relying on natural gas (even in co-gen plants) make for a sustainable policy ? How long will this last ?
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Gar Lipow Posted 12:32 am
01 Jul 2008
The U.S. is a much sunnier climate than the U.K. and has more square feet per person, especially in large commercial buildings, which tend to be one or two stories with flat roofs. So we have more PV potential per square foot of roof space, and significantly more square feet of roof space per person. The study also assumes that on unshaded east-west roofs flat solar is framed in, losing some efficiency and increasing costs but putting in solar where it could not otherwise go.
Also all coal in the U.S. is burned to make electricity, much of it in old grandfathered plants. You have to burn about three units of coal to produce one unit of electricity delivered to the user. So producing 7 quads of electricity replaces about 21 quads of fuel that generated that electricity, some of it coal, some of it natural gas that can be burned instead of coal. Almost another 8 quads of heating fuel displaced can generate the other 2 quads. (Another way to look at in is that 35% of our primary energy is used to produce electricity, but electricity represents about 13% of delivered energy. And that is with significant nuclear and hydro.) So solar on rooftops could indeed replace coal. You would need large wind and solar plants to replace the rest of our energy.
That said you are also ignoring some important points from the post:
Whether this is the most cost effective way to displace coal is another question. Also rooftop solar is a silver BB rather than a silver bullet: Even after massive efficiency improvements we will need to get many times the power from non-rooftop sources than from rooftops.
...physically possible is not the same as feasible.
If you read the post carefully it is outlining a limiting case, not making a proposal. It is a pushback against opponents of big wind farms and concentrating solar plants to show that even in the maximum case you can't rely on rooftops for all your power. It also showed that rooftops have significant potential. Something important to note when you read these posts: posters don't choose titles.
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amazingdrx Posted 12:45 am
01 Jul 2008
Every assumption needs to have a link to a scientific survey. Starting with roof area. Why would roof area per person be an accurate measure?
The huge mall of america in Minnesota has no furnaces, body heat from vistors and solar coming through the windows and waste heat and heat storage in building mass heats it all winter. How mant people would a building that size house?
In an apartment building the heating/cooling load is less per person. And in a taller building the south facing wall space tends to be larger. Why can't geo heat exchange go down deeper into the ground or cover larger areas not used for housing?
Geo heat exchange freezing the ground? That was one of MacKay's unsupported statements. Where did he get his heat flow figures? For fuel free heating/cooling it would be well worth it to install extra underground heat exchange outside cities if necessary.
Figures don't exagerate, but exagerators figure. MacKay and fans have a negative POV on renewables so they exagerate to make it look impractical. That makes their favored option, central nuclear power, seem necessary. It's the old false dilemna fallacy.
Disguised as a math problem to distract from the false assumptions.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Jon Rynn Posted 12:53 am
01 Jul 2008
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Jon Rynn Posted 12:55 am
01 Jul 2008
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Jon Rynn Posted 12:57 am
01 Jul 2008
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amazingdrx Posted 1:02 am
01 Jul 2008
Good eye Jon! You must be wearing sunglasses. That one blinded me.
$33 per day per person for electricity? 4000 bucks per month for a family of four?
Exagerators figuring.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Jon Rynn Posted 1:10 am
01 Jul 2008
I think it may be the case that economies of scale are at work, because when you have a large building, or a large set of buildings, it becomes more practical to drill down 100 feet or so, which I think is probably a much better depth than the 5 feet figure I've seen for single family homes. For instance, there is a development of dozens of townhouses here in Evanston using geothermal heat pumps, I assume they went pretty far down.
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vakibs Posted 2:01 am
01 Jul 2008
I agree that 15 KWH per person per day is an achievable target for solar PV roof tops. Being larger and sunnier, USA should go for it !
300 KWH is an obscene number which just tells us how wasteful of energy USA currently is. MacKay estimates that 125 KWH is a more reasonable number (this includes all forms of energy+food+gadgets etc in an energy efficient world). If solar PV rooftops make up for 15/125=12% in a futuristic energy plan, we still need to figure out about the remaining 88%.
The answer is that we will use wind and solar farms to fill up the gaps.
But if the gaps don't get filled up, it means that we will still be burning coal, sweet coal. This for industrial electricity generation.. for coal liquification plants to obtain gasolene.. and for coal based electricity generation in plug-in vehicles.
This is why I think it is irresponsible to make claims such as "solar roof tops will replace coal".
@Gar
Thanks for clarifying the mismatch of 23% coal usage in USA, and the actual electricity produced.
@amazingdrx
I don't believe that MacKay is a pronuker. He debunks a lot of anti-solar propaganda in his book. He even suggests a few purely solar plans.
I am a pronuker, btw. I just love to get converted to solar, but I am not yet convinced of its potential. I think MacKay should be congratulated for his efforts. Sustainable energy is a big mystery for the general public, due to the lack of common units for comparison. MacKay made a good start by explaining with the unit of KWH-per person-per day.
We need to improve on this obviously, and I hope that a common language will evolve to discuss the issues of energy and environment.
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vakibs Posted 2:10 am
01 Jul 2008
25% of electricity usage in China is apparently for exports. And most of this electricity comes from burning coal.
China is the most prolific coal consumer in the world (more than the USA). And coal is getting burnt there at an ever increasing pace.
Replacing coal will not be that easy..
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Jon Rynn Posted 2:16 am
01 Jul 2008
By the way, I suppose 300 kwh is all energy -- although all electric energy is only about 3 times the 12 kwh per person per day I was using, I don't think oil is much more than electricity, and natural gas either -- but the main point I want to make is that the worlds of electricity and oil, at least in the US, are pretty much completely distinct (I realize that in much of the world oil generates much more than the 1% of electricity in the US). In particular, the US transportation system is almost completely oil-based. And talk about waste, I'm sure we are the champions of transportation waste, with 3 thousand billion vehicle passenger miles in the US per year.
Now, I wish we had India's rail network, which I was informed by an Indian fellow on a rail trip I recently took, is the world's largest. If we did, and if we made much of it high-speed, and added light rail (and this could happen before pigs learned to fly), then I think we could drastically reduce our oil dependence. I hope India doesn't make the same transportation mistakes as the US.
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amazingdrx Posted 2:28 am
01 Jul 2008
And all the distributed fuel cell/turbine generators would be compatible with natural gas/biogas. Allowing natural gas to be phased out eventually as biogas takes over.
Some day soon maybe portable truck and train mounted solid oxide fuel cell/turbine backup generators, that can run on bioga/natural gas will be mass produced for trucks, tractors, and trains. Replacing internal combustion.
Converting diesel engines to run on natural gas is a good way to transition to an all renewable electric transportation energy system, backed up by biogas. We have 20 years to go 100% renewable, it can be done. And create wealth at the same time, that will give families financial security, and fight inflation.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Gar Lipow Posted 2:29 am
01 Jul 2008
No, the claim is that solar roof tops "could" replace coal. The post is about physical potential, makes it clear that is about physical potential and is accurate.
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MAD MAC Posted 2:49 am
01 Jul 2008
Victory in Pattani
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vakibs Posted 2:20 am
02 Jul 2008
India has a good rail network, largely thanks to the British colonial system. This had been run by coal at the time the British left. It is only recently hooked up to the electric grid. Several chunks of the network are still unhooked, and they run by diesel or even by coal.
The major transport problem for India are its cities. The concept of urban planning is virtually non existent in India, most of the urban development is dictated by real estate prices. Thus, Indian cities seriously lack basic amenities of transport, accomodation and sanitation.
This prompts the rich and the middle class to migrate to the suburbs, and we are trailing the the mistakes of USA in this aspect. More cars add up to the congestion and pollution. Metro-rail projects are either nonexistent or heavily underfunded.
Indian cities provide good case-studies for inefficient energy usage (and inefficient water usage). The sad thing is .. it is ten times more difficult to educate the public in India than in the USA. The politicians don't even bother to speak about these issues, as the majority would not understand them anyway.
And what is the point of trains or metro-rail if the major power production will be by coal ? India has about the same amount of coal as China , but it is not burning as aggressively as China does. But this is probably only a matter of time.
Despite the tropical potential, I don't see Indian government investing in costly technologies such as solar panels. India also has huge Thorium reserves, but massive nuclear plant construction has capital costs. There is not enough money in the country to provide the capital.
So the tragic answer would again be coal. India's coal reserves will last for 200 years, so there is a severe political argument in favor of more coal. "Why should we buy solar panels, or construct nuclear plants when the money thus saved can be spent in health and education ?" , they ask.
I think it is very important to keep looking for technologies which will scale to India and China. We should speak of global sustainable energy, instead of each single country. After all, the earth is one single sphere.
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Jon Rynn Posted 4:31 am
02 Jul 2008
I think that the rich countries -- US, Europe,Japan -- should help India and China jump start their solar and wind industries -- although I believe India has one of the larger wind companies, I believe they just bought one of the German ones. You're right, it's one planet, and the rich countries have contributed much more than their share of carbon to the atmosphere, time to clean it up!
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Gar Lipow Posted 6:21 am
02 Jul 2008
..rough numbers, a 13 m2 dish would cost $700 materials, $600 labor, and require <200 cm2 type III-V 40% efficient cells at something like $10/cm2 ~ $2000. $3300 for about 4,000 Watts(e) installed system at scale without margin plus inverter and cooling. Type III-V cells are used on the Mars rovers.
A new inverter would add about $800 would it not? With concentrators cutting the number of solar cells you need, it makes sense that inverter cos
So $4,100 for 4,000 watts. Add cost of either a cooling system with no added value or a more expensive cooling system that produces hot water and maybe some of your space heating as well. Still this damn close to the $1 a watt range, certainly well under the $1.50 a watt range.
So am I right Turnkey with inverter and cooling (and no hot watt water or space heating) well under $1.50 a watt. A more exensive system that uses the waste heat for hot water and space heating would double the effective output without doubling the price, so with solar CHP $.75 per watt (with a about half that power being thermal rather than electrical).
Add 50 cents per watt for margin. Could you deliver turnkey systems for that price? Because even if you lack the capital for mass production, there are a lot of people out there in our part of Washington State who probably be happy to pay $2.00 per watt for a turnkey solar electric system, or $1.25 per watt for a solar CHP system. (counting the thermal as though it were electric). Probably the pure electric would be more popular, cause of the lower upfront cost and the lack of need to change plumbing. Even though the pure thermal is the best buy, it would probably be least popular because you don't have the glamor of "look I'm running solar electric".)
Also is $600 labor for the whole - turnkey?
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sunflower Posted 9:10 am
02 Jul 2008
The objective of cost effective solar energy is to rapidly scale the displacement of fossil fuels. Industrial inertia to scale is mitigated by a gold rush of profits with minimum requirements of growth capital -- scale without tooling.
That gold rush will be chasing the lowest hanging fruit first, heavy energy users of oil and gas for low grade heat -- users surrounded by empty low-cost land under a sunny sky. An example is a meat packing plant in Yuma Arizona cleaning equipment with hot water, or a brewery in Fort Collins Colorado surrounded by alfalfa. This is very simple profitable solar, a $100 billion market in the US alone, and installs the profitable base for growth.
A niche market of solar thermal hotels, schools, farms, and homes will emerge and grow, followed by concentrator photovoltaics, concentrator thermal electric, and finally base-load solar power with region-wide district heating/cooling and seasonal heat storage.
More on hope. Concentrator pv can be done at 1000 suns with future cells at 50% efficiency so future solar power will cost much less. The one thing I've noticed is that solar always becomes less expensive with time while fossil fuels become more expensive with time. Join the green rush.
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stopgreenpath Posted 4:28 am
03 Jul 2008
all the energy models other than point-of-use renewables externalize huge costs onto the planet, the economy, homeowners and ratepayers while privatizing profits in Big Energy (yes, including Big Solar and Big Wind).
conservation has been an afterthought in 99% of buildings so far, ergo the incredible waste and consumption we are currently facing. unless and until ALL costs are accurately borne by energy producers, consumers and sellers (including all costs related to reduced reliability from lengthy transmission, which fails on a regular basis), local, point of use residential/ commercial PV, thermal and wind don't appear to make sense, but once the REAL costs of lost ecosystems, lower reliability, lost water, lost job opportunities, lost income streams to homeowners/ business owners, lost homes to Big Powerlines and pricing/supply manipulations are accounted for, there is only one solution.
the greenest energy is that which you needn't ever produce.
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MAD MAC Posted 4:50 am
03 Jul 2008
The days of the US being able to pull off a Marshal Plan are about to come to an abrupt end. The increasing cost of oil is going to be devastating to the global economy.
Victory in Pattani
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odograph Posted 7:42 am
05 Jul 2008
But the average homeowner? My gut says a managed corporate solar farm will beat them every time.
Just to give you the chance to convince me though, tell me what fraction of US home rooftops are actually suitable for solar: either flat, or south facing. Does anyone have a study?
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Jon Rynn Posted 7:55 am
05 Jul 2008
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odograph Posted 8:33 am
05 Jul 2008
Two previous estimates of the total available roof space for PV in the United States are 6 and 10 billion square meters, even after eliminating 35% to 80% of the total roof space due to shading and inappropriate orientation [6,7]. The lower value also does not include certain industrial and agricultural buildings. While fairly rough estimates, these values provide some idea of the potential resource base. Assuming a typical PV system performance of 100 watts per square meter (W/m2) (equivalent to an average insolation of 1000 W/m2 and a 10% AC system efficiency), this rooftop area represents a potential installed capacity of 600 to 1000 GW. At an average capacity factor of 17%, this installed capacity could provide 900-1500 terawatt-hours (TWh) annually. This represents about 25% to 40% of the total U.S. electricity consumption in 2004.
My comment:
25% to 40% is respectable, but not a firm number rivaling coal. From a quick stop at the EIA I learn "Based on primary energy source, coal-fired capacity represented 43 percent (260,990 megawatts) of the Nation's existing capacity (Figure 1).[2004]"
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odograph Posted 8:40 am
05 Jul 2008
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Jon Rynn Posted 8:50 am
05 Jul 2008
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Jon Rynn Posted 8:54 am
05 Jul 2008
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Gar Lipow Posted 12:41 pm
05 Jul 2008
You forgot, I was taking into consideration the use of concentrating solar, which lets you use more expensive more efficient cells because you need fewer of them. At double the cell efficiency 25%-40% turns into 50% to 80% which does indeed rival coal. But again, I am NOT saying this is feasible. I'm pointing out this as an upper limit on power from rooftops. In practice you never get close to maximum from anything (except sometimes harm).
I can't believe I was too subtle. I was pointing out there was no way rooftop power could ever provide all or most of our energy - by showing the what happens if you make the most optimistic reasonable assumptions.
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amazingdrx Posted 1:50 pm
05 Jul 2008
I thought that was way to mild, but then when it seemed possible that conservation could cut energy use in half, that was about right for wind. 40% of the new lower energy demand.
If you look at the estimate from the study Jon linked to, rooftop solar PV/heat cogeneration could supply the rest. Add in CSP on factory roofs and large buildings excluded from the study too. Those are roofs, south facing walls count too.
That is with various storage methods like building mass heat/cold storage, water pressure storage for plumbing systems, high temperature CDP storage, emergency battery storage in buildings, and backup power sources like biogas/natural gas.
Skeptics you are on the ropes. You don't have a factual argument to stand on. Just repitition, which Colbert points out, does create truthiness.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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MAD MAC Posted 4:27 pm
05 Jul 2008
For sure, some technologies will improve energy efficiencies. But others (like wide screen TVs) use a lot more energy than those they replaced.
So for planning purposes, planners should assume and increase, not a decrease, in demand and plan accordingly.
Now, if the price of power, based on supply availability, increases, that will force a decrease in consumption. No question there. But an increase in energy cost will have an inflationary impact across the board that will hurt every sector of economic growth. That has to be considered when discussing any energy planning.
Environmentalist have a single objective in mind - the environment. But energy planners have to look at not only the environment but also other requirements, especially economic impacts.
In my view, if attacked aggressively, the environment could actually be a great engine to spur economic growth. Within the United States Federal dollars could be directed towards environmentally friendly, sustainable energy sources. Once money is in the game, all kinds of smart people will be in the hunt to get it. People like money - this should be exploited, not spurned.
Victory in Pattani
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odograph Posted 11:10 pm
05 Jul 2008
The energy folks like to draw changes like this as wedges, with contribution from A (solar) growing while the contribution from B (coal) falls.
We want to achieve this this solar transition with maximum speed and return on investment.
Speaking as someone in Southern California, I think the best way to do that is with large scale installations, and professional operation. PV on large buildings might work, but I think we should be mainly looking out here at desert solar farms. The desert is only 100 miles away. Heh, it qualifies for a "100 mile energy diet."
I'm pushing back Gar not because I think home solar is bad (especially when it is homeowner funded), but because I think it is a shallower curve.
Dollar for dollar, year spent for year spent, I think it will give us less energy ... a shallower wedge.
And I really think the rational answer has an uphill battle ... because rooftop solar has so many irrational pulls for the population. "It's right there." "You can see it." "It's a house of the future."
But for every $ invested will it give you the best 10 or 20 year production?
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Jon Rynn Posted 12:38 am
06 Jul 2008
Mad Mac -- I think that what should be argued is that after the wind/solar electrical system, nation-wide, has been installed, electricity will be cheaper than it is now and also much more reliable (because the grid will have been rebuilt, and much of the solar/wind will be decentralized). So you should be able to sell it on economic grounds.
The problem is constructing it in the first place, which is why Federal and local governments should provide easy financing.
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odograph Posted 12:55 am
06 Jul 2008
With current technology what would it cost to replace SoCal's coal use (SCE consistently "predicts" < 10% of total, but then "uses" > 30%, see bottom right, page 2 of PDF) with rooftop solar, and then with desert solar?
I mean, you say "it might be worth the added expense just because of the "tactile", personal aspect" ... but what are we talking about as a premium? 10% 100%?
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amazingdrx Posted 1:22 am
06 Jul 2008
Since it isn't in mass production yet, those costs are guesstimates.
Low information voters are better than disinformation voters. The 27% bush faithful disinformation voters only produce frustration and spread limboob propaganda.
As Jon points out, this is a gradual transition (that won't even start unless/until america is mcbushless), as mass production and installation takes over and commodity fuel prices soar, wind and solar drops and fossil energy gets ever more expensive.
In order to take the best course in terms of GHG and the economy, extrapolation is necessary. The old saw, "let the 'free' market decide", is obsolete without an actual free market.
Only direct subsidies to consumers who purchase solar panels and geo heat exchange heating/cooling systems and other GHG saving technology will free up markets.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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odograph Posted 1:34 am
06 Jul 2008
I'm also skeptical about how many we'll get ;-)
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Gar Lipow Posted 1:43 am
06 Jul 2008
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Jon Rynn Posted 1:49 am
06 Jul 2008
So, whatever makes it work, make it work. It's worth it to get away from coal.
As to whether the money -- actually, think resources, factories, labor -- would be better spent on, say, CSP, that's easy, do both! To come back to reality a little more, at this point, I think it makes sense to try every possible permutation, and see what actually works, that is, push for pv on roofs, CSP, wind, geothermal, see what you get money for.
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odograph Posted 2:10 am
06 Jul 2008
Bad ol' me, I'm flying to Alaska tomorrow. To arrive at the Ted Stevens Anchorage International Airport galls me no end, but I have been to carbonfund.org
I'll look it up when I get back.
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amazingdrx Posted 2:21 am
06 Jul 2008
If it is defined as emergency power that is there no matter how much renewable energy is available.
Keeping factories and homes running as they are now, before conservation or geo heat exchange and heat/cold storage, is a job for coal and nuclear power.
A transition to a new pardigm, a renewable distributed generation and storage smart grid, will allow the centralized 100% dispatchable sources to be shut down.
High energy demand factories, like foundries and glass and metal recycling, will have to time their operations to the grid, instead of the reverse. Most could be shifted to use solar furnace CSP and molten salt storage. In less sunny areas factories could import electric power from the nearest wind farm along a high voltage DC transmission system.
And anyway, those old natural gas turbine generators and even old piston engines will always be around for ultimate emergencies, if we convert coal (sour oil, tar too) to natural gas undergound, with natural bacteria. Natural gas doesn't wear the generators out very fast.
Talk all you want about replacing our centralized 100% dispatchable (until a summer air conditioning high load blackout, hehey) grid with a 100% dispatchable renewable power grid. But it will never be cost effective. Adjusting only the supply side of energy is problematic, even with fossil/nuclear power, the demand side must be adjustable too.
If homes and buildings need to go to emergency battery/natural gas cogeneration backup for hours or even days with inadequate wind, sun, water, and biogas power. So be it.
Shut high energy factories down for a few days, as happens anyway with storm and summer heat grid overload, and run everything on emergency backup natural gas.
What if volcanic winter sets in for a few years? No solar, but adequate wind. What if wind storms knock out most of the wind power?
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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amazingdrx Posted 2:29 am
06 Jul 2008
A 20 to 50 hp backup generator in each plugin hybrid vehicle made in flex fuel version to run on natural gas/biogas or liquid fuel, would be close enough to match the total grid generation capacity we have now.
Plug in the vehicles to a gas line and let the smart grid start and stop them as necessary. There's an ultimate emergency distributed backup plan.
Mass produced solid oxide fuel cell/turbine generators (maybe 10 years away) for cars and trucks, would even make this 70% efficient.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Gar Lipow Posted 3:15 am
06 Jul 2008
If they are running on fossil fuel or biomass, not better environmentally that centralized power. The fetishism of distributed power over low carbon power. If they are running on hydrogen from electrolysis, NOT a least cost path, or a second or third least cost path.
Yeah we need everything, but there physical limits and practical limits.
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amazingdrx Posted 3:30 am
06 Jul 2008
Nano storage developments make portable tanks very small and safe too, to replace backup liquid fuel.
To answer bio-d's critique of serial hybrids, the backup generator could connect directly to the drive train through an (speed sensing) electric clutch, for economy cruising after plugin in battery power is exhausted.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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amazingdrx Posted 3:35 am
06 Jul 2008
The hope is it won't impell a big natural gas guzzller economy with big trucks and SUVs burning gas instead of oil.
It is 1 dollar per gallon equivalent to a gallon of diesel. That could push a big conversion industry starting in long haul trucking.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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amazingdrx Posted 3:49 am
06 Jul 2008
I meant 230x the density of the (bio, natural) gas in free air. It means a similar sized tank in your car, at atmospheric pressure (no "bomb" effect), to the one you have now, would take the car just as far. On natural gas, as it would on gasoline.
With flex fuel biogas/natural gas or gasoline or diesel could be used in the same vehicle.
The vestigial gas guzzling system would eventually fall away as technology evolves, hehey.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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GreyFlcn Posted 4:09 am
06 Jul 2008
The problem with distributed Solar is that it doesn't provide reliable power, and it doesn't provide night-time power.
CSP in deserts is both reliable, (Hardly any cloudy days a year), and can provide night-time power (Thermal Heat Storage)
And it can do all that for less than it costs to build new coal fired power plants.
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MAD MAC Posted 4:58 am
06 Jul 2008
But clearly when invested at the corporate and government level, massive wind farms in areas with consistently good wind, and massive solar power stations in areas with good, consistent sunlight, are the way to go. In the long run, if we can combine this with nuclear power,we can end up with energy that perhaps is even cheaper than what we have today. Of course that won't be true in the short or medium term, but might well prove true down the road.
Victory in Pattani
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vakibs Posted 10:01 pm
10 Jul 2008
This probably means that solar PV would be close to achieving 50% efficiency in the future, increasing the energy density to 40 W/m^2.
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amazingdrx Posted 12:51 am
11 Jul 2008
10 sun PV concentration has reached 38% already, according to NREL tests. And the cooling isn't really a drawback, it is a plus, producing cogenerated heat.
IBM had a breakthrough with cooling recently, getting the same power from one tenth of the PV cells with 10 sun concentration. Where was the NREL 38% efficiency in the IBM test? Not sure. 30 times the power per cell area of regular flat panel PV should be possible.
This still looks good for converting glass to solar PV concentrating collectors. There's a lot of solar power hitting those skyscrapers!
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Xunergy Posted 10:13 am
26 Aug 2008
TME Layer technology does exactly that. TME Layer is a low cost sheet material that when placed in front of southern walls in Northern Hemisphere (or northern walls in Southern Hemisphere) will block direct summer sunlight but allow essentially all the winter sunlight, as well as much of diffuse light in all seasons to go through. In Spring/Autumn, it will allow a portion of the direct sunlight to go through - at low altitude locations, it blocks most of the direct sunlight, while at high altitude locations, it allows most sunlight to go through. It can be used in southeastern and southwestern sides as well (or northeast and northwest in Souterhn Hemisphere), although not as effective as on south side. It can also be used on northern, northeastern or northwestern sides (or southern, southeastern and southwestern in Southern Hemisphere), although in that case, the function is really to block direct Summer sunlight and direct Spring/Autumn sunlight. Besides, it can be used to block the direct summer sunlight in skylights on northern roofs (or southern roofs in Southern Hemisphere).
We have put together a one-page website http://www.tmelayer.com and plan to put more information there in the near future.
We try to provide solutions to energy and environment related problems
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Xunergy Posted 10:46 am
26 Aug 2008
We (Xunergy PV Systems http://www.xunergy.com) have developed a static CPV technology that can concentrate sunlight to 5x sun for monofacial cells (or 10x for bifacial cells). We'd be glad to see such a high efficiency for such a low concentrating factor. I guess the cost of such cells is still an issue, though.
However, I can see how the color glass technology developed at MIT can be combined with ours: using colored glass to concentrate the higher frequency lights and using our CPV technology to concentrate the red and IR lights. That may allow the efficiency of the solar cell to reach 40-50% using the conventional, expensive multi-junction cells.
We try to provide solutions to energy and environment related problems
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Xunergy Posted 11:26 am
26 Aug 2008
in that post should be
"That may allow the efficiency of the solar cell to reach 40-50% without using the conventional, expensive multi-junction cells."
We try to provide solutions to energy and environment related problems
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