Breakthrough in solar photovoltaics

An anonymous reader writes "The Holy Grail of researchers in the field of solar photovoltaic (SPV) electricity is to generate it at a lower cost than that of grid electricity. The goal now seems to be within reach. A Palo Alto (California ) start-up, named Nanosolar Inc., founded in 2002, claims that it has developed a commercial scale technology that can deliver solar electricity at 5 cents per kilowatt-hour. " As always, take these claims with a dose of salt the size of the Hope Diamond.

Cost ?

[mirko]

What about the cells themselves, the life duration ?
Could we "coat" a laptop with these in order to enhance its battery life duration ?

Re:Cost ?

[Ruie]

Could we "coat" a laptop with these in order to enhance its battery life duration ?

Yes we can. However it would be called "rooftop"
then - the article lists the size of 120 watt panel as 14 feet by 10 feet.

You'll get a really large screen though.

Re:Cost ?

[suso]

The problem with all this is that a large portion of the country that consumes a lot of power is in areas that don't get enough sunlight per year to be efficient. The midwest for example. I remember seeing a map somewhere that color-coded the US like a weathermap, showing areas that could efficiently support solar energy. Sadly, the only good place for it is in the southwest. Maybe this new technology can do better?

Re:Cost ?

[Proaxiom]

The problem with all this is that a large portion of the country that consumes a lot of power is in areas that don't get enough sunlight per year to be efficient.

Indeed. If only we had some means of moving electricity from one place to another.

Re:Cost ?

[suso]

Alright, point taken. But I somehow wonder if power plants in the midwest would really just close up and start buying their power from the west coast.
It would have to be much cheaper I would think.

Re:Cost ?

[Fulcrum of Evil]

But I somehow wonder if power plants in the midwest would really just close up and start buying their power from the west coast.

Actually, it's just the reverse, thanks to Enron and California's refusal to build new power plants.

Re:Cost ?

[Anonymous Coward]

> Actually, it's just the reverse, thanks to Enron and California's refusal to build new power plants.

California did not refuse to build new power plants, and has in fact been building them like mad ever since it got raped by Enron.

Enron shut down Enron's power plants, Enron moved out of state, became a distributor only, and Enron did so deliberately in order to create shortages. Enron managed to pin this on CA, and to this day, Enron's criminal behavior has gone unpunished by regulators while California seeks to get back the overcharges caused by Enron.

Clear?

Re:Cost ?

[3dr]

I wouldn't pin the entire fiasco on Enron. Enron had its own fraudulent goings-on elsewhere.

Meanwhile, just prior to the California energy crisis, the geniuses there decided to only partially regulate the industry. If I remember this correctly, they fixed the wholesale price while letting the retail price fluctuate. As more private enterprises attempt to sell power (and thus drive the price down) they are unable to pay the fixed wholesale price. They shut down, and at that point, with fewer producers,

Less Pot and More Facts, Please.

[tjstork]

First off, despite what Enron did, the State of California dug itself into a hole because of NIMBY. There was little or no plant construction in California during the 1990s, a time when the population boomed. It was impossible to get permits for new plants and most new construction was tied up in courts over environmental issues. When the crunch did happen, Enron and others wrongly exploited California, but not at all in the way that has been oversimplified by the press or even the idiot Ralph Nader types.

California, because it had not built enough power plants, was importing power from other states.

In order to import power you have to have your own power system suitably balanced. It's not like you put electrons on trucks and wheel them in. To do this, you offer financial incentives to buy or sell power at various points on the grid. To this day, PJM does this on the east coast and you can actually check it out here PJM LMP pricing [pjm.com]

Also, you have to adequate transmission rights to get the power in.

So what Enron did was rather clever. First, they had better software than the California ISO for determining grid imbalances and so they scheduled power deals to manipulate the grid. Import power in the north, export it in the south, boom there is an imbalance, and you can sell the power you exported back to the state for a lot of dough. Then, they would also go and buy up transmission rights into the state (which is actually pretty cheap), and then play games at peak times.

The amazing thing about the whole thing is that gaming California's stupid grid managers WAS LEGAL. That's right. Enron didn't do -anything- wrong by screwing the state of California. The state made its rules for its market place and Enron exploited them, but California should not have made those rules to begin with. To cap it all off, California deregulation stripped utilities of the ability to pass variable costs to consumers. So, if the price of electricity shot up, it should have shot up for consumers as well, and guess what, people turn their air conditioners down, and there is no power crisis. But oh no, California made it so that the utilities could not recover the costs and so they had to sell power at a loss, and all the utilities in California went bankrupt, and Enron made a mountain of money, legally.

The thing that got Enron into trouble was that they were lying on their financial statements, and for that, the company is now bankrupt, her executives are either on trial, and the accounting firm that certified those statements no longer exists.

Re:Cost ?

[ElectricRook]

Actually, it's just the reverse, thanks to Enron and California's refusal to build new power plants.

IMHO, It was California Legislators who prevented private companies from building power plants, and it was California Legislators, that enabled Enron and other trading groups owned by California Legislators who raped California Ratepayers/Taxpayers.

Ever notice no-one ever explored who was behind the energy trading companies?

Re:Cost ?

[Orne]

No, it just has to be cheaper than the cost of the energy losses to transport the power + the cost of the infrastructure. The losses, while low, are not insignificant, plus you have voltage attenuation issues to deal with (see Surge Impedance Loading [google.com])

Given that the cost of EHV transmission is on the order of a US$1 million per mile, and you're talking several hundred miles, and that total cost has to be invested before the first dollar of actual energy can flow... there's a significan prohibitor right the

Cost avoidance

[Engineer-Poet]

(Disclaimer: I've been blogging about Nanosolar [blogspot.com] for a while now.)

You're probably mistaken about generator companies. There probably won't be all that many, unless they are maintaining the panels on the roofs of buildings and carports. If you put the generation right next to the points of use, you don't need any more transmission and distribution equipment and your capital costs go way, way down; the companies which sell power along with a contract to maintain a roof are going to beat the other guys, becaus

Re:Cost ?

[jericho4.0]

But the real benefit of solar is decenteralized generation, which cuts the cost of transmission. This, of course, means that solar will not replace everyones power needs. (I'm ignoring the fact that a persons power consumption is far more than they consume at home)

My girlfriend lives in a solar powered house here in BC (Canada). For 4 months she has to suplement power from the grid, but for the rest of the year, it's enough. That's big savings. Another friend lives in a passive solar house, and only had to fire up his heat for about 2 weeks this winter. And these are spacious houses with lots of windows and all the normal (power saving) appliances.

The thing about these techniques is; they're cost efective _now_, if you can aford the capital outlay. Your bills go down, and it pays for itself.

Re:Cost ?

[justin12345]

I imagine that as the efficiency increases, the areas where it becomes feasible increase as well. Even in the short term, as a supplement to the existing power grid it would really decrease costs, both monetarily speaking and in terms of pollution.

I doubt the power monopolies are very happy about this though. If you can buy a machine that generates power, it will eventually put them out of business.

Re:Cost ?

[BeBoxer]

The problem with all this is that a large portion of the country that consumes a lot of power is in areas that don't get enough sunlight per year to be efficient.

I see this all the time. Please tell me why an alternative energy source has to be able to replace 100% of electricity to be viable? No, solar can't do it all. Neither can wind. Or hydro. Or geothermal. Or biofuel. Or nuclear. Or coal for that matter. But if we can get solar, wind, hydro, geothermal, nuclear and biofuel to each pick up 5% or 10% of our energy needs then there is a 25% to 50% reduction in fossil fuel consumption.

Every single /. article about alternative energy gets posts from people dissing it because it can't do it all. Where did this requirement come from? Is single-sourcing all of our energy even desirable? Is it possible? Where does this stupid meme keep coming from?

Is single-sourcing all of our energy desirable?

[StarKruzr]

Absolutely not, and I would mod you up if I could.

I wonder if this is part of the "most Slashdotters are Trekkies" effect which presumes that all power in THE FUTURE is generated by antimatter reactors, and so if we haven't found a power source that can replace everything, it must not be any good.

Morons.

Re:Is single-sourcing all of our energy desirable?

[tigersha]

The other not-so-good meme is that solar energy has to replace everything that is available already immediately.

A set of Solar Panels on the roof of a house (or rather some solar thermal water heater) cannot replace all the gas that a house needs. But it CAN reduct your enegy bill considerably. My dad has a setup like that on our roof and he got a visit from the utilities who thought he has mucked around with the meter. Not so, a few simply black sets of pipies pre heated the water which helped reduce the electicity bill.

I work in a building which (admittedly with the help of a solar research institute) has reduced its energy consumption by 65% by good use of isolation and glazing. I might add that this is in Germany, not exactly the sunniest place in the world, so it works in more northern climes too.

The key here is local power generation and better isolation of the building instead of massive central power stations. For instance, the people in the previous article moans that a notebook cannot be powered by it. No, maybe not. But those cells might increase the duration of your battery by an hour or two and that is useful in itself. Because you get more out of your notebook and reduce consumption of fossil/nuclear powered electricity.

Most solar research does not deal with PV in any case, it deals with better isolation and solar thermal (concentrated rays and such) to reduce reliance on other energy sources.

Anone wants to know more about Solar please visit
ISES [ises.org].

Re:Is single-sourcing all of our energy desirable?

[skogs]

I second this. A while back we had a slashdot article about some solar paint product that produced energy from the infrared band not just the visible band. These panels were much more efficient. Perhaps we can double the technologies up on eachother.

Secondly, cost effectiveness is not just what the power company can do. Remember my power company puts out a little pie chart telling me how much my electricity costs and why.

35% generation

3% Transmission

62% Distribution

If we build solar cells in our own homes at our own costs, we negate the transmission and distribution costs. All we need to do is generate enough to cover our homes/office buildings etc and we have a 65% automatic head start on the power company. Lets build our own infrastructure shall we?

Re:Is single-sourcing all of our energy desirable?

[Anderlan]

I have to take this oppurtunity, since someone has mentioned taking simple measures to decrease CO2, to give props the simplest way anyone reading this can start to do it: go to the lower power light bulbs they sell nowadays. Those twisty kind that go in normal incandescent sockets. (They're also sold with the twistyness covered by a normal looking outer shell.)

They don't have the problems of past low power bulbs. They don't blink. I've never noticed a blink rate, and I've been reading by them for 4 years. They do take 20-45seconds to get to full output. A 60-watt rated bulb (actually 15 or so watts) starts out at what I would say is 40-watt equivalent light, but it gets up to full in less than a minute. That's great, if you need more than 40W incandescent-equivalent light, you're going to have the light on for more than 20 seconds, so don't anyone think about complaining about that.

Everyone that hears me should go out and buy these for their homes. I don't mean to sound demanding. I sincerely desire to know what would be a good reason not to use them, because I can't find one.

These bulbs are sold as long-lasting, or cost-saving, but they need to instead be sold as environmentally friendly, and as using 75% less fossil feuls while their on, 75% less CO2 created, etc, etc.

Re:Cost-effective solar

[afidel]

Any study which shows that solar cells take more energy to produce than they make in their lifetime must have been written in the 1960's because solar cells have been net efficient for a LONG time. The problem has been that they weren't COST efficient. With rising fuel prices and increased efficiency we have known for some time that the balance would tip in favor of solar. The problem is that solar has to be significantly CHEAPER than the utilities on a per unit basis because you have to make back both the cost of electricity AND the oportunity cost on capital. Btw central NJ is barely cold in the dead of winter, try Northern Ohio, Minnesota, or parts of Canada for cold. I'm not saying passive solar heating is bad, it's very good, but it won't supply enough BTU's for heating even a moderate sized home in colder climates.

Exactly: For Example the Sun Goes Out Suddenly-

[purduephotog]

- then where exactly are you going to get your solar power? From glow-in-the-dark stickers left on your ceiling? I don't think so! Or maybe you'll just burn lots of dead plants to make light... still not very efficient....

alternative energies

[N3wsByt3]

I'm all for alternative energies, but the problem is rather the unrealistic views some (especially the greens) have of it.

It's not as much a question of *IF* it helps when their is alternative energy available, but rather the amount it can replace - at least, when you are diosmantling (as happens in my country) nuclear powerplants that provide about 60% of the total power. This was due thanks to the pressure of the greens. No-one seemed to have wondered at that time, where that energy should come from in the future - apart from some nonsensical crap about windmills and the lot.

Ofcourse, it's plainly obvious that those won't do by a long stretch, so then it DOES become important to know how much it can replace. Solar can't do it, not even a tenth of the required energy. Neither can wind. Or hydro. Or geothermal. Or biofuel. And all taken together, they STILL wouldn't replace more then half of what is needed today, let alone in 5 years, when nuclear powerplants are shut down.

In fact, from your entire list, only two CAN have a reasonable chance of providing enough energy now and in the future; and those are nuclear and/or coal.

I think that's what ppl mean, when they say alternative energies are not real options as yet. Sure, anything that helps is welcome, but in any realistic viepoint, ALL of the above mentionned energysources - apart from nuclear and fossile fuels - even combined together will NOT be make more then a drop in the ever power-hungry ocean, at least in large parts of the western world.

I think the only real solution is fusion. But untill that because viable, the use of coal will rise, alternative energies will remain largely a fringe activity (at least on large scale demand) and closing down nuclear reactions without providing real alternatives remain political idiocies without equal in a socio-economic sense.

Re:alternative energies

[ccady]

What about the deep Sahara desert? There are vast (almost) lifeless parts of the desert which could be "paved over" -- this might have a few benefits: 1) It could bring some much needed economic benefit to the continent, and 2) it much halt some of the unnatural (?) growth of the desert.

I'm partly serious here.

Comprehensive EU plan for CSP in Sahara

[MZdoctor]

A detailed plan for generating electricity in the Sahara already exists. The technology is called Concentrating Solar Power or CSP and has already proved itself on a large scale in the Mojave Desert. The details have been worked out by TREC, the Trans-Mediterranean Energy Cooperation. See http://www.trec-eumena.org/

The results of the EU ECOSTAR CSP program have just been released at a workshop held last thursday in Brussels. The 140-page report can be downloaded from ftp://ftp.dlr.de/ecostar. CSP power stations occupying an area the size of France in the Sahara, using available technology, can produce the current total energy consumption of the whole world.

Re:theory vs practicality

[Waffle Iron]

Isn't it possible that sea-life dependen on the sun, would get affected?

We're talking about less than 1/2 of 1% of the total ocean area. Did anybody consider what would happen before we altered 25% or more of the total land area, or before we started harvesting 90% of the population of various ocean species? Why the sudden interest in side effects?

If the worst case global warming scenarios are correct and a lot of glaciers melt, the size of the oceans will be altered by much more than 0.5% anyway.

Here's my viewpoint: If you put collectors up over 0.5% of the ocean, you create side effects with that order of magnitude. If you release CO2, it continually accumulates in the atmosphere, and it hasn't been determined if natural processes will remove it in any reasonable amount of time. Some scientists predict that its level will double over pre-existing levels; that's a 100% increase in an important climactic variable. The side effects from our current activities will likely to be much greater than anything that would happen with solar collectors.

Will it not become a burden to the sea-routes and a danger to ships?

That's why it's good modern technology has brought us GPS, radar and RFID.

Who would be legally responsable? What if they are layed in international waters?

Some treaties would probably have to be created. Since they would involve something constructive, they would have a more positive tone than the proscriptive Kyoto treaty, and people would be more willing to participate. (We'll see if anybody actually abides by the Kyoto treaty when push comes to shove, or if it's all just talk.)

What is the cost of maintainance? How many will get wrecked by storms? Will it be economical viable?

Those are good questions. There are similar questions about fossil fuels, like would it be economically viable to dig thousands of wells from floating ocean platforms miles into the earth's crust. People did the hard work to find out, and the answer was yes. If people had given up just because the questions existed, we wouldn't have any energy supply today.

You mention wind power and wave power a lot. I agree that they won't ever add up to a large fraction of total energy supply, and that's because there is a limited supply of windy land area and shorelines. Solar collectors don't need to have that limitation. I'm all for fusion power too, but IMO its technical feasibility is currently even more questionable than my "crazy" proposal.

Re:theory vs practicality

[Waffle Iron]

If solar platforms in the oceans is the solution, why not windmill platforms on the ocean?

Because the windiest areas are created by land featues.

But they do have that limitation.

I just got done explaining how they don't. Maybe you can provide some detail to back up your assertion.

Being less "questionable" doesn't make it realistic.

Ok, so we're doomed once fossil fuels run out. Do you have any better ideas?

Re:alternative energies

[bleckywelcky]

Well, to correct a couple things: the impact would be WAY larger than the size of a football field. And second, the "desolate frozen waste" that you speak of is hardly that. People visit these areas every year to enjoy the wilderness, hunt, hike, camp, etc. Many animal species use this land to live, breed, etc - including some endangered species. Even some natives work the land and countryside to survive. It's some of the most beautiful pristine country around and it has been the least impacted by human civ

Indeed - Solar thermal.

[Moderation abuser]

Guess what is by far the largest sources of domestic electricity consumption in cold areas?

Heating.

In hot areas... Cooling.

Neither of which require much electricity to accomplish. It's just easier and we're lazy and stupid.

My hot water tank has an 11kW element, the storage heaters in each room are 3kW each. I burn electricity to make heat.

On the other hand, solar thermal systems are far cheaper than photovoltaics, they're basically black pipes in a glass case. They are also far far more efficient, capturing around 80% of the energy incident on them.

They can produce decent amounts of heat even mid winter in the UK. Enough to heat up my hot water tank to scalding, a few more panels on the roof and I reckon a gas central heating boiler may not even be required. The result is a truly *huge* decrease in the amount of gas and electricity consumed in the home...

You still have a heating element in your water tank, and a gas boiler in your central heating but they spend most of their time inactive.

Big problem? Cost, even though thermal systems can be 80% efficient and are a small fraction of the cost of photovoltaics, the payback period is still 5-10 years.

Good intro:
http://www.galeforce.nireland.co.uk/solar/ index.ht m

Re:Cost ?

[syphax]

Solar Insolation Maps [windsun.com]

Avg. solar radiation is surprisingly uniform. Sure, the southwest is higher, but it's at most 2x anywhere else in the U.S.

Re:Cost ?

[HangingChad]

Right. Just because your winter insolation values are low doesn't mean you can't use solar, it just means you'll have to spend more on your array than someone in sunny New Mexico or Arizona. And you'll need more batteries to get you through the cloudy days.

So in northern climates or overcast areas then you look at either building a really BIG array that costs many thousands of $$$ or supplement with wind turbines (much cheaper cost/watt). Even then in the winter you may need the assistance of a gasoli

Re:Cost ?

[Dastardly]

The real interesting question will be how will the local governments and power utilities react to the sudden loss of revenue when people start dumping them? I could see protectionist regulations (all your electrons belong to us), use taxes on solar systems or very large increases on those remaining tied to the grid. Sooner or later we would reach a new production equilibrium but the infrastructure transition is going to be ugly. Lot of utilities have come to believe they have a right to exist and local government would have to replace the revenue. If these new $1/watt systems landed suddenly, you would see a lot of people cutting the cord. The rest of the technology for the home power cycle is already there.

The transition would be tough, but I would hope that they don't go to prtectionist. They need to switch to transmission, storage, night production, and middle man. Businesses use a lot more power than they have roof space, typically during the day when you are not home and your home system will be producing more power than you are using. So, the utilities job is to purchase that power (it can be in exchange for night power) and deliver it to businesses during the day. The utility would also provide power at night. If large scale storage is more efficient than local storage and the solar build out was big enough utilities would also become central storage such that they would store excess daytime production for delivery at night.

Likely (and it exists currently) you pay a connection fee and any excess power used. In the future, there will probably be a connection fee that encompasses storage if that is available, a rate for power to the home beyond what is generated, and perhaps the wholesale rate for when day generation exceeds night use that could defray the connection and storage charge. As businesses will be paying for that power a portion should go to the generator.

Re:Cost ?

[EvilTwinSkippy]

I am a resident of the "North East." Our peak electricity usage is on sunny days during the summer. That's when everybody cranks up their air conditioning to dump the energy the sun delivered to their roof out into the outside air through the miracle of air conditioning.

This peak demand electricity is the costliest to produce. That's when you bust out the natural gas turbines, and start running your boilers and reactors at full tilt. A field of solar cells, at the right price, would really lower the cost of delivering electricity during these peak times.

I recall a news story a few years ago about a resident in my home town (Philly) who outfitted his roof with solar cells. All of his appliances were DC powered, and during some seasons of the year his meter flowed backward; he was producing more power than he was pulling off the grid.

Re:Cost ?

[DaChesserCat]

First off, most households which have PV also have an inverter. They may run some things off DC, because there is inherent inefficiency in an inverter, but they still produce AC for stuff like the washer and dryer. HomePower magazine had a article several months ago about wiring some 24V or 48V DC into the home, and which items could be run reliably from it (the answering machine used a simple $5 DC step-down voltage converter from Radio Shack, and his motion-sensitive lighting outside still had AC-powere

Re:Cost ?

[diablomonic]

no the article makes a mistake (claiming 120 watts per square inch heheh id love to see that, considering less than a watt of solar power falls on a square inch in direct sunlight) what it should have said (i assume) is 120watts per square meter, which makes sense since they claim 12% efficiency, and 12 % of the 1 KW that falls per square meter in strong sunlight is 120watts

this implies that the sheet 10 X14 feet produces around 1.5 killowatts, and costs around 500 bucks!!!!! GIMME GIMME I WANT ONE

Re:Cost ?

[Locutus]

If they can pull this off, it'll definately have an impact at that price. We paid ~$500 EACH for our 18 Sharp 165W panels( 3'x5' ) and expect about 10 years for payback. That's 1.6KW for ~10'x14' of panels but at a cost of ~$5000.

A 10x reduction in cost would be great but there is still the problem of roof space. An increase in power density would make this a no-brainer and somewhere, there's a group who said they can get 50% efficiency out of their solar tech and are working on effective manufacturing techniques. THAT will be the bubble bursting move IMO. If it happens.

LoB

Re:Cost ?

[jdray]

I suspect I'd be interested, too, though I'm not sure just how much.

I live in Portland, and, per the Insolation Map linked above, we get about 4 kWh/m^2/day on average. If you figure on using a twelve (3x4) square meter panel, that's 48 kWh/day. At 12% efficiency, you're at 5.76 kWh/day of actual generated electricity.

Since it's an average, you can figure on that output year 'round. So, 5.76 * 365 days is 2102.4 kWh/year. At $0.09 per kWh (the going rate for electricity here), that's $189.22 per year

Re:Cost ?

[Dastardly]

Your average solar panel is warrantied for 25 years. So, 10 years is less than half the warranty period of a typical solar panel. Oh, and there are installations that have been working for 30 years or more. Mostly national park stuff, or hand me downs for public operations. i.e. some company had the panels 30 years ago after 10-20 years they upgraded, and donated it to public parks or something where it has been sitting and working for 20 years or more.

So, yes we do not know the lifetime of a solar panel because there doesn't appear to be data for end of life failure of solar panels. That is an important distinction because there have likely been failures of solar panels, but end of life failure would see a lot of panels of the same installation time failing near the same time.

Re:Cost ?

[$eth31]

Of course, even with THAT large of a screen, there'll still be people who INSIST on using 800x600

Re:Cost ?

[Xoro]

Well, it said 12% efficiency, so I'd assume they meant per square *meter*, since 120 W/sq m corresponds to 12% efficiency.

120 Watts per square inch would rock, though -- it's about 200 times the theoretical maximum.

Re:Cost ?

[hankwang]

While it is impractical to drive the entire machine from solar power, it should be possible to get around 7W from coating the back of the screen in solar cells, giving a nice boost

Good luck while using your laptop with TFT screen while sitting outside in bright sun light, while squeezing a mirror between your legs in order to direct the sunlight to the back side of the screen...

Re:Cost ?

[Etherael]

How about the top of the stratosphere, supported by a helium floatation device? easier to reach than orbit, closer to the surface, below the mesosphere where the microasteroids typically burn up... still above the ozone layer where the majority of UV light is absorbed?

Re:Cost ?

[EsbenMoseHansen]

Or how about putting nuclear power plants on the surface of the earth where they might be hooked up to homes and institutions?

How about nuclear power plants in the stratosphere, supported by a helium floating device?

Re:Cost ?

[dheltzel]

Seriously, solar power is ridiculously overrated. The energy density of sunlight at the earth's surface is simply too low to be practical. Way too much real estate would have to be used to make any realistic amounts of power, and at those scales, upkeep becomes prohibitively expensive.

Shhh!

Don't tell the plants. If they find out that sunlight is impractical as a power source, we'll be in a real pickle, a real pickle, I tell ya'

Per Square _inch_?

[compwizrd]

The flagship product, Nanosolar SolarPly, is a 14 feet x 10 feet solar electricity module delivering 120 watts per square inch at 110V.

Something seems fishy about this. Isn't the amount of sunlight hitting the earth only about a KW per sq. M?

Re:Per Square _inch_?

[pe1rxq]

It varies between 3 and about 6 KW per sq. M

Jeroen

Re:Per Square _inch_?

[Anonymous Coward]

According to this [solarserver.de] (and several other sites [google.com]), it's about 1.4 kW/m^2 (at 1 AU, perpendicular to direction of Sun, in space). This is 0.9W/sq. in. or 130W/sq. ft.

So the article has got something badly wrong...either they've got the units wrong - 120W/m^2 sounds plausible, 120W/sq. ft. is theoretically possible but extremely unlikely as it would require 90% efficiency, 120W/sq. in. is totally impossible for Earth based solar - or they're being taken for a ride.

Re:Per Square _inch_?

[Phanatic1a]

It most certainly does *not.* Insolation at *Earth's orbit* is only 1.3 kilowatts per square meter, so it can't possibly be greater than that at the Earth's surface without some kind of focusing array.

6 kilowatts per square meter? That's a 'you must be on crack' figure.

Here [uoregon.edu] are some actual numbers:

On average the extraterrestrial irradiance is 1367 Watts/meter2 (W/m2).

[...]

Near noon on a day without clouds, about 25% of the solar radiation is scattered and absorbed as it passes through the atmosphere. Therefore about 1000 w/m2 of the incident solar radiation reaches the earth's surface without being significantly scattered.

Note that that's *peak*. Averaged over, say, a year, which includes periods where the sun doesn't shine at all ("night"), as well as periods where it's not high noon on a cloudless day, and average insolation falls quite a bit. This site [apricus-solar.com] claims a yearly average for central Australia of 5.89 kilowatt-hours per meter per day, which (if my conversion is right), breaks down to an *average* insolation of 245 watts. So just flat-out double that to get rid of the night time, and you're getting an average value of about 500 watts in one of the sunniest, hottest places on the planet.

Some basic math

[i41Overlord]

I've heard it stated that the amount of energy in sunlight on Earth's surface is between 1 and 6 KW per square meter, probably being closer to 1 KW per square meter.

There are 1550 square inches in 1 square meter. Even if there was (optimistic) 6 KW/sq meter of sunlight hitting the Earth, you'd only have 3.9 watts per square inch.

So their claim of over 100+ Watts per square inch is obviously an error. I don't think they'd even claim that since it doesn't even come close.

They also claim that their panels are 12% efficient, so a more realistic figure would be 1 KW of sunlight per square meter, equalling about .65 Watts per square inch, with 12% efficiency would be about .08 watts per square inch made by these solar panels.

Re:Per Square _inch_?

[irhtfp]

It varies between 3 and about 6 KW per sq. M

Those figures you're looking at are per day. See here [nrel.gov] for an excellent set of maps.

Re:Per Square _inch_?

[Betelgeuse]

Hmm. . . Good point. . . It says here [solarserver.de] that it's 1.47 kW/m^2 . . .

The only thing I could think of is that it's maybe one of those numbers is per Hz, or something. . .

Anyone else know?

Re:Per Square _inch_?

[Zoyd]

Hmm. . . Good point. . . It says here [solarserver.de] that it's 1.47 kW/m^2
That website says: "The maximum value on earth is between 0.8 and 1.0 kW / m^2."

Can't tell from the web site

[jfengel]

I'd belive 120 watts all told, which I believe would actually be a pretty good output; as stated it's ludicrous. Sadly, their website doesn't say; it hasn't been updated since November.

The article is reasonably well written, though I'm not used to getting major engineering announcements from The Hindu. (Presumably an Indian paper is reporting on events in Palo Alto because of the number of Indians working on the project.) Maybe they just botched the rewrite of the press release. Odd that I can't find t

Re:Per Square _inch_?

[Monkelectric]

Its more then fishy. Why is it published in "The Hindu" ? 120 watts per square inch? I could power my computer with 3 square inches. My whole house with a square foot of the stuff.

This is either the biggest breakthrough in our modern age, or complete bullshit. Im inclined to belive its bullshit :)

Metric Conversion and Stonehenge

[billstewart]

Sorry, but it's hard not to visualize the scene in Spinal Tap where the dwarves are dancing around the really short dolmen that was supposed to be 18 feet tall instead of 18 inches...

This sounds like the kind of mistake made by somebody who's used to working with the metric system writing down the wrong name for unfamiliar foreign antique measurement systes, rather like most of us tend to misread things measured in pecks per square furlong or whatever.

Re:Metric Conversion and Stonehenge

[Hognoxious]

the scene in Spinal Tap where the dwarves are dancing around the really short dolmen that was supposed to be 18 feet tall instead of 18 inches...

I hope your post gets modded up to 11.

Re:Per Square _inch_?

[OdieWan]

From the Nanosolar FAQ [nanosolar.com], we get the suggestion it's actually around 100Wp/m^2, or about 10% efficent. (Wp means "Watts at Peak Sunlight")

Q: What is the expected cost per square meter of typical Nanosolar solar cell module?

A: A square meter of (an array of interconnected) Silicon solar cells (a "module") has a product cost of approximately $300 (or $2.75/Wp) from today's cost leaders in Silicon. Nanosolar solar sheets/modules are based on much thinner cells (up to 1000x thinner in their active layer) and

Re:Per Square _inch_? [THAT'S CORRECT]

[ryanvm]

No, that's correct - it is 120 watts per square inch. What they don't tell you is that you have to install a 300 foot diameter magnifying glass over your house.

Re:Per Square _inch_?

[syphax]

Yeah, this is definitely wrong.

Peak ncident solar radiation is typically ~ 1 kW per square meter. That the article claims efficiency of 12%, so the 120 watts is per square meter (under strong sun). It's interesting to me that this thing delivers at 110V.

Affordable solar has been on the horizon for a long, long time. There's a good amount of activity at present (Konarka [konarkatech.com] is another interesting company); let's hope someone is actually able to deliver soon.

Also, let me pre-emptively respond to a few post

Re:Per Square _inch_?

[maxwell demon]

120 watts per sqare inch would indeed be 186kW/m^2, much more than the sun delivers.

If we assume they actually meant that the complete panel had 120W, at the size given it would make 9.2W/m^2, which would be an efficiency factor of about 1%. (10W per kW incoming sunlight). I don't know what the typical efficiency factor of other solar cells is, but I'd be surprised if they are all below 1%.

Or maybe it's actually 120 W/m^2 (which would make an efficiency of about 12%)? After all, confusion between metric a

Two lousy links for nanosolar

[doinky]

on google news. This is setting off the crackpot alarm big-time, as much as I want to believe.

Re:Two lousy links for nanosolar

[Vollernurd]

Stock-pumping, perhaps? Hell, I'd buy. But then again I get all my stock tips from Slashdot.

Let the fun begin!

[chris09876]

Everyone feels the same way about this - quite doubtful (but still somewhat optimistic inside). Wouldn't it be great to be able to charge your cell phone by exposing it to some sunlight? Solar energy has a lot of 'potential'. Even with its current state, it does have some uses. Eventually, one of these 'breakthroughs' might have some merit, and give the technology the push it needs to become more mainstream.

interesting

[slobber]

The semiconductor paint can be applied to a flexible substrate , such as a polymer sheet , through a simple web printing process, to create an array of ultra-thin solar cells.

Does this mean I can turn my roof into one huge solar panel by "painting" solar panel on it?

From TFA

[Joe12Pack]

"The breakthrough has come through the application of nanotechnology to create components via molecular self-assembly, including quantum dots (10nm large nanoparticles) as well as nanotemplates with structural order extending through all three dimensions." Even more exciting, the raw material used in this process is snake oil.....

These are probably dye-sensitized semiconductors

[hankwang]

The company's website is a bit low on details that would make the reader understand what it all is about. The article in The Hindu isn't much better and mostly copies the hollow phrases from the site.

From what I read on the website: nanostructured materials, estimated lifetime of 25 years, made of "nontoxic semiconductor paint" suggests that it is about dye-sensitized solar cells [google.com]. These are based on small TiO2 particles, the same that is used as a pigment in white paint. These do not absorb visible light by themselves, but can catch and transport electrons from certain light-absorbing dyes. These solar cells were invented around 15 years ago; the necessary components of such a solar cell, TiO2, dye, solvents, sandwiched between two glass plates, are relatively cheap, but the yield is still below 10% (sunlight power to electrical power).

Apparently, this company has found a way to mass-produce cells based on this principle using plastic films instead of glass. The glass was the most expensive component; the problem with plastic films is that it is hard to make them last a long time while still being impermeable to oxygen and the liquid solvent inside the cell.

Re:These are probably dye-sensitized semiconductor

[VendingMenace]

Actually, i don't think that the glass was the most expensive. Most of the cells used ruthenium dyes for their light absorbing dyes. Ruthenium is not exactly cheap. Moreover, it is not even all that plentiful. I remember hearing once at a conference that the amount of ruthenium expected to be in the earth's crust is only enough to make enough solar cells to cover the state of north dakota or something like that.

I think this is the main problem with solar cells. Until someone comes up with an effecient dye based on a more abundant metal there is no possible way that solar cells can become ubiquitous.

Though it is unclear from the site what sort of dyes this company is using -- perhaps they have found a new one. Though i suspect if they had it would be all over their site. I gather, rather, that they are just using the "nano" buzzword to make their stuff sound new and cool. Oh well.

OH, by the way i am not a solar cell scientist -- but i do work down the hall from a few. Cool.

Re:These are probably dye-sensitized semiconductor

[hankwang]

I remember hearing once at a conference that the amount of ruthenium expected to be in the earth's crust is only enough to make enough solar cells to cover the state of north dakota or something like that.

Hmm. The abundance of ruthenium [webelements.com] is about 1 ppb in the crust, so that would be about 10^14 kg. IIRC, you need only a few mg of pure Ru per square meter, so I don't think this is the issue. Of course, it might be hard to extract that kind of amounts from the crust, but that is a different story. My old 198

Re:These are probably dye-sensitized semiconductor

[hankwang]

There is a host of organic compounds that absorb light. Do you think your car painted with Ruthenium?

I don't own a car, but there is probably not much ruthenium in my bikes. :)

Dyes in dye-sensitized semiconductor photovoltaics need to satisfy different requirements than those in paint. Most importantly, it should release an electron to the semiconductor when it absorbs a photon and should have a low probability of recapturing that electron from the semiconductor. How DSSC cells operate is very different

Doesn't look like a scam...

[Stile 65]

Their management team looks top-notch (ex-Intel, NIST, etc.); their partners include Sandia, Stanford, and Berkeley; and their investors include Stanford and Sergey Brin and Larry Page.

I think these guys are for real.

Check out their news page

[qwasty]

http://www.nanosolar.com/articles.htm [nanosolar.com]

They've got government contracts, funding out the wazoo, etc. They're not just a garage shop with fancy website.

Re:Doesn't look like a scam...

[Ogemaniac]

This company is the real deal. The product, of course, is overhyped (I bet the 5 cent/kWh is in the Arizona desert!), but this company is one of the serious major players in this field. Actually, I just saw a mention of them this morning in a peer-reviewed journal.

Re:Doesn't look like a scam...

[HiThere]

OK. But that doesn't mean you should believe what a PR flac puts out. (Well, the report is that they aren't claiming superefficient cell, merely very cheap ones...with the efficiency not specified. And possibly not the lifetime.)

It seems they're printing solar cells on plastic film "cheaply". This may not be too durable, but if it's cheap enough there could be lots of uses for it.

The energy industry is not a meritocracy

[Jooly Rodney]

Look, I haven't even RTFA, but isn't it the case that having a the best (i.e., cheapest, most efficient) technology doesn't guarantee you squat? (At least in the U.S.) Even if it's easy to implement, won't existing energy concerns have it in their best interests to block its adoption?

Do not question this source

[bigtallmofo]

Before anyone questions the unimpeachable reputation of "The Hindu" - "Online Edition of India's National Newspaper", please keep in mind that they've brought significant news to us in the past.

How many of us would not be alive today had they not warned us about mysterious monkeymen [hinduonnet.com]?

Exciting.. Where Do I Sign?

[tetrahedrassface]

Big claims require big evidence. I surely hope that the price can be set at at the 5 cents/kwh, but something nagging in the back of my mind says not yet.

However if it is indeed true, it should not be a huge surprise. The cost of solar has been falling in recent years.

I did speak to a solar firm about putting in enough to run my house ( 69 kwh/month ) the cost to install was going to be around 75,000 dollars, and in my area electricity is still to cheap to justify the cost.

However if I can install at this super low 5 cents/kwh, I just might bite the bullet. That is roughly 2 cents/kwh cheaper than my utility sells juice for!

Good article!

Re:Exciting.. Where Do I Sign?

[Damvan]

Ummm, No.

First of all, that 69 kwh/month has to be wrong. Nobody uses that little electricity.

If it is correct, my $25,000 solar system will produce 69 kwh of electricity in 4 sunny days, so no, you don't need $75k worth of equipment. For 69 kwh/month, about $2k worth of equipment at the most.

Grain of Salt

[soloport]

Not too good with reverse-logic, are we?

The reference is to a grain of salt because, with just a grain of salt, one wouldn't eat much of what's being served.

To take something with a dose of salt "the size of the Hope Diamond", well, one could conceivably eat the whole thing -- wait for it... -- hook, line and sinker.

Re:Grain of Salt

[smallpaul]

Most peole believe that the grain of salt is the antidote to the mistruth. The true meaning is lost in the mists of time so you might be right or they might be.

According to Word detective [word-detective.com]:

"It's fitting that you've been looking for the origin of this phrase "forever," because "with a grain of salt" has been around nearly that long. It's actually a translation of the Latin phrase "cum grano salis." There seems to be a bit of a debate about the significance of the Latin phrase, however. Etymologist Christine Ammer traces it to Pompey's discovery, recorded by Pliny in 77 A.D., of an antidote to poison which had to be taken with a small amount of salt to be effective. Everyone else seems to bypass that explanation and trace "with a grain of salt" to the dinner table, where a dash of salt can often make uninspired cooking more palatable. "With a grain of salt" first appeared in English in 1647, and has been in constant use since then. The amount of salt metaphorically needed to make an unlikely statement acceptable often varies from a few grains to a few pounds. With all the flapdoodle being thrust at us these days, I'm surprised there isn't a national salt shortage."

Snake Oil? Snake Oil? They have pictures

[pklong]

This isn't snake oil. They have pictures up here [nanosolar.com].

Heard it all before!

[Zog The Undeniable]

Nuclear energy was, we were told, going to be too cheap to meter when the UK Calder Hall reactor was opened in the 1950s. Now the industry is propped up by government subsidies.

Actually, I *am* a fan of nuclear energy; the economic case is only poor because the clean-up requirements are absurdly expensive - considering that coal-fired plants spew an order of magnitude more radioactive fallout across the countryside.

Still too expensive

[Martin Blank]

Even at five cents per kWh, it's more than 40% more than the target cost for other methods, which is around 3.5 cents per kWh. That's the range where gas, coal, and oil plants live, and where nuclear is striving to be (Westinghouse's 1000MW AP1000 reactor design is the only approved one that may reach that, and it came about because the AP600 wasn't efficient enough).

Anything much more than that without ample tax incentives (and maybe not even then) just isn't going to happen on a large scale.

...without infrastructure costs...

[cirby]

The 3.5 cents/kwh you see for a modern power plant is for the cost at the plant, not to the customer. You have to add in the costs of supporting the network, billing, and transmission losses.

Solar power at your house for 5 cents/kwh is a lot cheaper than 3.5 cents/kwh a hundred miles away (which ends up being about three times that to the customer).

Well...

[Quiet_Desperation]

They gots themselves a DARPA contract. Having been involved in an effort to get one of those, it's not the easiest thing in the world.

http://www.nanosolar.com/pr2.htm [nanosolar.com]

$30 / square meter?

[frosh]

If this cost # is true, then the cost of this solar panel is approximately the same as the cost of ashphalt shingles. And if *that* is true, there would be no reason to put any sort of roof on a house except for a roof made of this stuff...

Breaking News: Attorney General Declares ...

[burgburgburg]

that NanoSolar, Inc. is a terrorist front organization. All of the employees, their relatives and close neighbors have been summarily rendered to the country of their origin (for those born here, it was determined that their country of origin would have been Syria).

Also, the AG has written the binding opinion that anyone trying to exploit technology supposed developed by NanoSolar, Inc. would be open to physical coersion up to and probably including limb removal that would not legally be considered to be torture.

Go about your business. Nothing to see here.

It's all about funding

[bigtrouble77]

If you check out their site you'll see immediately that they are seeking finantial backers. I'm sure their intention is to create some buzz to attract more investers. Unfortunately for them, making outlandish claims may have a reverse effect.

Slashdot needs Science Editors

[StCredZero]

It doesn't make it better to continue to post both crap and legitimate articles and to put "take it with a grain of salt" at the end. Whether or not Slashdot science links are snake oil or legit news seems to be random. Basically, not enough of the editors can tell the difference. Slashdot needs a qualified science editors!

Their site lacks details

[telemonster]

Their website lacks simple details. If you look at other sites that sell BP solar panels, they say "You can expact this many KwHr from a 20 2'x4' panels." They show pictures of the 14x10 array, but it doesn't actually commit the output of it. It says the per square inch figure. The commercial page mentions installations of 1Kw or more... 1Kw would be 10 square inches of their product. Very odd. If normal solar panels were less expensive I'd be all for it. If every house had a 2Kw array, it would definitly help reduce load during peak times in the summers, and reduce overall consumption. I did some research, and if I were to pay $60,000+ (new price) for a solar array, after 30 years I could expect to have saved $30,000. Groan.

Taking care of some things in one post.

[WOV]

OK, since this is a solar photovoltaics post:

Someone is going to claim that solar will never be practical, because it is 10 - 15% efficient, while internal combustion, etc. is 30%+. Please, consider that you have to *buy the energy* that goes into that 30% efficienct machine, while the 15% efficient solar panel gets it all free - then run the numbers. The only cost that matters is the dollars per Watt capital cost of the cells upfront (which is still too high, but coming down.)

Someone is going to claim that solar panels produce less energy over their lives than it takes to manufacture them. This has not been true for about 40 years. [energy.gov]

Someone is going to claim that solar panels are a toxic danger to human health. Please consider that they are manufactured using identical processes to microprocessors, are easier to disassemble for recycling, and last 20 - 30 years plus, as compared to the five year or so length for most consumer electronics.

Someone is going to claim that solar only makes sense in certain parts of the United States. Keep in mind that, for instance, Albany, NY gets 80% of the solar radiation of Reno, NV. Since you pay twice as much for electricity in Albany, solar panels actually make more sense there. (Remember, most solar panels go on rooftops and spin meters backwards - you get retail price ($.08 - $.15 / kWh,) not wholesale ($.02-$.04) like a power plant.

Someone is going to claim you would have to blanket the desert with solar panels to make a workable power plant. Is this what you do with a distributed, smart, resource, that can occupy unused roof space anywhere? Did we take all of our microchips and assemble them into one giant supercomputer in the desert? Solar panels belong in a distributed network of generators - at the end of the wire, and putting them there is cheap and practical.

Someone is going to claim the solar industry can never meet real-world power demands. Check any industry publication for an interesting statistic - in 1996, 100 megawatts of solar were manufactured. Jan - Dec. 2004 saw about 1100 MW (about $ 6 billion worth) manufactured. Still pretty small, but an amazing growth rate.

What does solar cost now? About 1/20 what it did in the 1970s, but still about twice as much as grid electricity. Once you buy the panels, and finance them with, say, a home equity loan, you're looking at $.18 - $.25 /kWh. Getting closer every year, but still not quite there.

Finally, a comment on the article. Yeah, Nanosolar is pretty neat, but I think that Konarka [konarkatech.com] is quite a bit further along - and doesn't share nanosolar's tendency to overpromise. Here's what needs to happen. Their efficiency is fine, don't care - a 5% or 10% efficient cell, as long as it's less than $1.50 / Watt, the world will beat a path to your door. However, their longevity is not there. A normal silicon solar panel lasts at least 20 years, these things last more like 5 right now. Hence their strategy of putting them in consumer electronics that have about that lifetime anyway.

To be a real power generation source, they need to get that lifetime up by a factor of 4 - doable with the right encapsulants, some chemistry, getting rid of liquid electrolytes, etc. I bet one of these poeple will be at $.10 / kWh in five years - but the conventional silicon cells can probably get there in about 8, with manufacturing and scale improvements. So it's a real race...we'll see who pulls it out.

Re:Taking care of some things in one post.

[IronChef]

Someone else will claim that despite how the numbers may work out, solar power will always be for hippies.

Re:Taking care of some things in one post.

[Big_Breaker]

Lots of great points. I work for one of the largest renewable energy companies in North America, and I'd like to mention a couple of things you touched on that are worth some extra mention.

Similiar to hydro, solar's cost component is primarily in the upfront cost of equipment rather then the uncertain "trailer" of fossil fuels. Coal - the dirtiest fuel you can imagine - is currently extremely available for next to nothing, however. Natural gas prices fluctuate a great deal but natural gas power plants are relatively cheap to setup and can be run at opportune times when power is extremely profitable. These plants are often called "peakers" for that reason. I mention the timing aspect because it is especially important to analyzing solar. Why you say? Because
solar's timing stinks.

Direct solar energy availabilty does not line up well with electricity consumption. This means that as solar power approaches "free" the part of the system that stores the solar energy becomes the dominant cost component. There also aren't many great ways to store energy from PV panels. Chemical batteries deteriorate, are usually toxic, heavy, expensive and space hogging. Demand forms of energy production like hydro and natural gas do not have this limitation and can be respond to customer needs rapidly. Coal is slower but can be moderated with the demand curve to an extent.

Another key point is that photovoltaic cells produce direct current and not the alternating current required for most consumer and industrial needs. A small amount of energy storage and an inverter are necessary to transform the energy from a solar panel into something useful. This becomes important again when talk turns to distributed production. The fixed cost of the electronics simply does not scale particularly well. I wish it were simpler to just hoist some PV panels on everyone's roof but it isn't.

Re:Taking care of some things in one post.

[WOV]

I think it's closer to the truth to say you just aren't comprehending what I am saying. I never said solar was free. Solar's *ENERGY COST* - what you pay to get energy out of it - I set at that $.20 / kWh sort of range. None of that is fuel cost.

A solar panel, you have to buy and install the panel. You must also maintain it. That is your cost. You HAVE A CAPITAL COST. You have maintenance costs, too. You have to pay money to get solar energy. How many ways do I have to say it? But there IS NO FUEL

Google founders invested

[bmarklein]

Their investors [nanosolar.com] are well-known and have funded or founded some very "real" companies. They include Benchmark Capital (who funded eBay), USVP (who provided initial funding for Sun), and the founders of Google (Brin and Page).

There's a patent: #6,852,920

[Animats]

The web site looks weak, but Nanosolar has an issued patent [uspto.gov] which describes how they claim to do it.

First, by "manufactured by printing", they don't mean a roll to roll process like a printing press. They propose to deposit materials with an inkjet-like mechanism.

Second, what they call "nanotechnology" is surface chemistry. There are ways to make semi-regular structures by bulk chemical means, and that's what they're doing. They did throw a reference to "bioengineered self-assembly" in, but that's not how they do it. The processing looks much more like processes you'd do in a wafer fab. There are common fab processes like electrodeposition, chemical removal of support substrates, and heating in an inert atmosphere.

The basic idea is to address the reasons that solar cells are inefficient. In bulk materials like silicon, only a small fraction of the photons do anything useful. Most of the photons are at the wrong wavelength. And many of the photon interactions that do occur don't result in an electron being delivered to the output. They're trying to fix both of those problems.

Their policy seems to be to shut up until it works. It might work, or it might not. They're not selling stock, and they're not issuing press releases. They have VC funding and some money from DARPA.

Dose of Salt... why post?

[lbmouse]

As always, take these claims with a dose of salt the size of the Hope Diamond.

Slashdot
Hearsay for nerds. Stuff that never happens.

Immediately, we need a New Rule:

[Catbeller]

New Rule:

(which congress should pass but never will)

Oil companies should not be permitted to buy this
company, or the patents.

Guess who owns nickel-metal hydride battery patents? Yup. Exxon-Mobil. No electric cars here, move along, nothing to see.

If there is a threat to their business model, energy companies will buy out the corporation which developed the tech and drown it in the nearest toilet.

You lie, your feet stink, and dont love jesus.

[thelizman]

I know its popular to bash oil companies, but its also disingenuous, especially when you lie.

The patent for NiMH batteries is held by ECD Ovonics, which is owned by Texaco and Mobil.

The question a thinking individual might ask is why are oil companies interested in developing better, more efficient batteries when it would mean less oil being consumed to keep them charged. The answer is simply this - oil companies dont' care about oil. Oil is just a highly profitable commodity. What oil companies care abou

Re:hope diamond my ass

[delta_avi_delta]

Actually, I'm not certain that that's where the expression comes from at all. To be taken with a grain of salt comes from the latin "cum grano salis", and was used by Pliney in describing Pompey's discovery of an antidote for poison that had to be taken with a small amount of salt to work. Since in Roman times, they believed that salt was linked to intelligence, the phrase "cum grano salis" was adopted and came to mean "(take) with a little common sense", which is similar to the "be skeptical" meaning of

Re:Would these add to global warming?

[narcc]

Don't solar panels produce heat as a by-product?


So does the sun...

That used to be true

[thelizman]

Neither solar nor nuclear... [w]ill fit the US economic model. They favor centralised power generation, which favors high density cities, trains and trams, rather than suburbs and automobiles...

That's not necessarily true any longer. Most larger power coops will actually buy power from their customers. In the desert southwest, for instance, power companies have realized a cost savings from customers who use solar and dump their excess back into the grid. Since the power companies don't have to maintain