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Iron pyrite is the top material picked by a University of California at Berkley and Lawrence Berkeley National Laboratory to replace silicon in solar cells. While modestly less efficient than crystalline silicon, its dramatic cheaper in processing costs and very abundant. Adopting it as a replacement to silicon or thin films could dramatically cut costs and enable enough production to supply the world's power needs, according to the team.  (Source: Crystals Guide)
Search for more abundant, lower cost materials should help improve solar cost efficiency

Solar power is an incredibly promising alternative energy technology.  However, the problem with converting solar energy directly to solar power via photovoltaics or other designs is that the cost of producing power is simply not cost competitive with nature's designs -- coal or petrol.

The cost issues are not for lack of efficiency.  Scientists have milked very high efficiency out of the cells, iteratively raising the yield year by year.  However, the high cost of silicon, the primary material for solar panel cells, keeps the costs high even as efficiencies experience dramatic gains.

In order to make solar cost competitive, researchers at University of California, Berkeley, and the Lawrence Berkeley National Laboratory (LBNL) are spearheading the search for a silicon replacement for the solar industry. 

The team surveyed 23 promising semiconducting materials and then pared the field down to the 12 that are abundant enough to meet or exceed the world's yearly energy needs.  From there 9 were selected, which exhibited significant cost savings in raw material costs over crystalline silicon.

Daniel Kammen, UC Berkeley professor of energy and resources, and colleagues Cyrus Wadia of LBNL and A. Paul Alivisatos of UC Berkeley's Department of Chemistry discovered that some superior solar choices may have been overlooked due to the desire to keep the status-quo of silicon.  They believe before solar power can be deployed on a broad scale, the basic science must be reevaluated to ensure that the industry is using the best possible materials, rather than blindly proceeding. 

Wadia states, "The reason we started looking at new materials is because people often assume solar will be the dominant energy source of the future.  Because the sun is the Earth's most reliable and plentiful resource, solar definitely has that potential, but current solar technology may not get us there in a timeframe that is meaningful, if at all. It's important to be optimistic, but when considering the practicalities of a solar-dominated energy system, we must turn our attention back to basic science research if we are to solve the problem."

Today's top solar materials are crystalline silicon and thin film CdTe (cadmium telluride) and CIGS (copper indium gallium selenide).  Silicon is abundant, but costs a great deal to process.  The exotic metals like indium used in thin films are cheaper to process, but less abundant.  If the world switched to all solar, they would quickly run out.  States Professor Kammen, "We believe in a portfolio of technologies and therefore continue to support the commercial development of all photovoltaic technologies.  Yet, what we've found is that some leading thin films may be difficult to scale as high as global electricity consumption."

Wadia adds, "It's not to say that these materials won't play a significant role.  But rather, if our objective is to supply the majority of electricity in this way, we must quickly consider alternative materials that are Earth-abundant, non-toxic and cheap. These are the materials that can get us to our goals more rapidly."

The team's top candidates for a replacement material are iron pyrite, copper sulfide, and copper oxide.  Of them, iron pyrite is the cheapest, being plentiful and easy to process.  While nanoscale science has shown that cells of such unconventional materials will experience modest efficiency losses, the researchers say that these costs will be easy offset by the decrease in raw materials and processing costs.

Professor Kammen concludes, "As the U.S. envisions a clean energy future consistent with the vision outlined by President Obama, it is exciting that the range of promising solar cell materials is expanding, ideally just as a national renewable energy strategy takes shape."

The team's research was funded by the U.S. Environmental Protection Agency, the Energy Foundation, the Karsten Family Foundation Endowment of the Renewable and Appropriate Energy Laboratory.  It appears in the journal Environmental Science & Technology.

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RE: How modest is modest?
By JasonMick on 2/20/2009 12:35:53 PM , Rating: 2
Not to voice foul heresy to my fellow environmentalists, but maybe the roof is not the best place for solar cells ?
(I'm talking a suburban setting, not a urban rooftop setting)

Its already pretty much a foregone conclusion, even among most environmentalists that solar cells in some locations (such as car roofs) are a bad idea due to the limited area and small power generation potential, barring some tremendous efficiency breakthrough.

Maybe is better to have cheap solar deployment in plentiful wasteland, like deserts.

Or maybe use iron-pyrite solar for large scale installation and crystalline silicon for roofs. Such a hybrid approach might be the best solution.

I think the point of the study, though, was to raise the need for careful reexamination of whether we're proceeding in the right direction with solar materials, before we get too far off into silicon technology.

RE: How modest is modest?
By bhieb on 2/20/2009 12:44:05 PM , Rating: 5
... to my fellow environmentalists...wasteland, like deserts.

Just poking fun but I love that you call yourself an environmentalist and use the word wasteland :) No land is a wasteland for a true tree hugger. They would point out that installing large square feet of artificial shade in a dessert dramatically changes the ecosystem. Since shade is a valuable resource to most dessert dwellers, and adding more will cause some to thrive artificially.

RE: How modest is modest?
By JasonMick on 2/20/2009 1:27:51 PM , Rating: 5
There's environmentalists and then there's practical environmentalists.

A desert solar array would not have a crippling effect on most of the desert organisms, as it would have little effect on the sediment, temperature, or vegetation level (or lack thereof). Further, the desert is an ecosystem of limited biodiversity. It makes far more sense to utilize this space while protecting ecosystems like deciduous forests and swamplands, and rainforests. If you want to be practical, focus on protecting the regions with the highest species density -- aside from conservation for the sake of preserve biological diversity and world balance, this also has economic benefits as the millions of creatures there are more likely to contain valuable medical chemicals than the handful of desert creatures. Blind idealism gets good ideas nowhere, its practical idealism that makes a real difference.

I'm by no means advocating scrapping protection efforts for desert creatures, just saying that its an area of lesser biodiversity, something anyone familiar with basic biology knows. There's not many tree's to hug in the desert -- maybe some cacti, but not many trees.
(I make noted exception to areas of dense desert vegetation, such as the Joshua Tree Nation Park)

RE: How modest is modest?
By bhieb on 2/20/2009 1:53:07 PM , Rating: 2
Blind idealism gets good ideas nowhere, its practical idealism that makes a real difference.

Agreed, and as stated just poking fun. Some things have to be compromised on, and the desert is a good place to put these.

Regardless of ones beliefs (Darwin/Intel Design), mankind is the dominate species, and by either definition we can/should use any and all of the planets resources as we see fit. Either because we are "evlovled" to a level that we can do as we see fit until nature corrects the imbalance (a nice ice age or severe global warming would do). Or because we are "allowed" by a higher power to do so until he/she/it smites us for doing it poorly. In either case we can do what we want so we should if it meets our needs. The planet is an inanimate object that will continue to float around in space with or without us. So self preservation is our only real concern, the debate is what is best for us?

RE: How modest is modest?
By bhieb on 2/20/2009 1:57:27 PM , Rating: 2
Wow just re-read that WAY to philosophical for a Friday and really off topic. You can ignore that babble.

RE: How modest is modest?
By Spuke on 2/20/2009 3:49:36 PM , Rating: 1
It's fine with me.

RE: How modest is modest?
By Adul on 2/20/2009 4:54:21 PM , Rating: 2
ever been to the desert southwest?Its not really lacking vegetation here. There is a good amount of plant life, and various desert critters.

RE: How modest is modest?
By Oregonian2 on 2/20/2009 6:44:32 PM , Rating: 2
Yes, the only politically acceptable places for massive solar panels are locations that are already "ruined". Big cities and/or perhaps existing farms (run up the price of corn for additional reasons).

RE: How modest is modest?
By ekv on 2/20/2009 10:55:12 PM , Rating: 2
I wish there were more "practical environmentalists". There are 3 Solar plants scheduled for "remote" areas in a certain west coast state. A couple hundred miles above Joshua Tree National Park in fact. The solar power plants would create many private industry jobs and actually put a bit of power onto the grid.

The latest I've heard however is that there are 2, not 1, but 2 lawsuits by environmentalists to stop the solar power plants. Insanity.

RE: How modest is modest?
By Suntan on 2/20/2009 12:51:57 PM , Rating: 2
I'm a good 1,500 miles from any "plentiful desert wasteland."

The closest open area around me has a bunch of crops growing in it. You want to cover that land up with solar cells?

...More efficiency please.


RE: How modest is modest?
By CommodoreVic20 on 2/20/2009 1:04:11 PM , Rating: 2
I think a better application might be large solar farms that benefit mankind on a greater scale rather than an individual's home.

Desserts seem to be the first place people think but they forget the truly wasted space atop the many industrial warehouse type buildings and stores. Super Walmarts, Super targets, industrial parks with enormous flat roof areas. Stadiums, heck even as roofs over massive parking lots. You don't need to pollute the desserts when we already live in polluted wastelands.

RE: How modest is modest?
By Suntan on 2/20/2009 1:16:28 PM , Rating: 2
That sounds well and good. But don't forget the fact that most existing buildings do not have the infrastructure to deal with the weight on their roofs, nor the electrical system to handle it either.

I suppose it could be mandated and paid for by the government (they seem to be eager to overpay for everything else right now.) But you still have the issue of forcing building owners to do these things because you think it would save the world.

If you want to force me to install solar on the top of my target building, that's fine, but first I get to force you to stop taking showers (need to save water, its a vanishing resource ya know) so from now on, you're only allowed to lick yourself clean like a cat. Because *I* think that will help save the world.


RE: How modest is modest?
By Justin Time on 2/20/2009 1:38:32 PM , Rating: 2
You don't need to FORCE anyone to install solar, just create a tax/rebate scheme that makes it attractive to allocate your available space to generating power that way.

RE: How modest is modest?
By acejj26 on 2/20/09, Rating: 0
RE: How modest is modest?
By lagomorpha on 2/20/2009 10:26:10 PM , Rating: 2
Better idea: Wait until someone figures out a way to make solar energy cheap enough to pay for itself and businesses and consumers won't be able to get them installed fast enough. Personally I prefer the solar sterling engine over cells but we'll see what tech ends up cheaper.

RE: How modest is modest?
By Suntan on 2/20/2009 5:06:04 PM , Rating: 2
Targeted taxation to force people into conforming…Fair enough.

An $800 excise tax on each gallon of “shower water” then.


RE: How modest is modest?
By Spuke on 2/20/2009 7:01:55 PM , Rating: 2
An $800 excise tax on each gallon of “shower water” then.
I think you're taking this a little too far. $20 a gallon wouldn't be out of line.

RE: How modest is modest?
By Suntan on 2/20/2009 7:11:06 PM , Rating: 2
Fine, $20 a gallon... ...but an additional "Shower guzzler" tax on any bathroom that has those fancy multi-spigot shower installations, they use more shower water than any person needs.

Because even though you will pay taxes on the shower water you use, if you still enjoy yourself doing it, we need to get more money out of you.


RE: How modest is modest?
By Starcub on 2/20/2009 1:01:47 PM , Rating: 2
Its already pretty much a foregone conclusion, even among most environmentalists that solar cells in some locations (such as car roofs) are a bad idea due to the limited area and small power generation potential

I'll take issue with this. You could probably put the equivalent of two rooftop solar panels on top of a car. However, even only one would probably be able to pay for itself over the lifetime of the car. In fact, only one might be prefferable depending on what type of battery system the car employs. A Volt or hybrid vehicle with a large battery could recharge to almost full after spending 4 or more hours idle in the sun. It wouldn't be hard to adjust your power charging tech to accomodate a solar charger, you just need to do it so as to take full advantage of the panel.

RE: How modest is modest?
By Lugaidster on 2/20/2009 1:19:28 PM , Rating: 2
A small bump on the car and all your investment goes to hell. Cars aren't viable for something as delicate as a solar panel.

RE: How modest is modest?
By Starcub on 3/18/2009 1:52:40 PM , Rating: 2
On the top surfaces where you would want them they would be vialble. I have a solar bag from Voltaic Systems right now that I've smack the heck out of that worked for a few months until it developed a heat performance issue. However, I suspect this isn't because the panel itself was bad, but the solder joint to the terminal was too fragile. In any case, if they can be used on rooftops, they can be adapted to be used on cars as well.

RE: How modest is modest?
By JasonMick on 2/20/2009 1:35:23 PM , Rating: 2
A Volt or hybrid vehicle with a large battery could recharge to almost full after spending 4 or more hours idle in the sun

Without some hard numbers, I'm inclined to say that there's no way a single (or two) rooftop panels could provide enough electricity to give a Volt a full charge in four hours, on any current commercial battery. That is simply infeasible. If you need proof, look at the solar car challenge -- those cars are ultra-light and aerodynamic (with no stereo, heat, etc as well) and they barely can go for a few hours and are incredibly expensive. No way two solar panels could provide enough to charge a normal sized electric vehicle, even a relatively light one. They might be able to charge its electronics, but not much beyond that.

If such a system was at all possible, someone would surely be bringing it to market.

Maybe someday such a feat would be possible, but to my understanding what you're suggesting is entirely impossible with current technology.

RE: How modest is modest?
By Solandri on 2/20/2009 2:12:25 PM , Rating: 2
The Volt is supposed to have a 16 kWh battery pack.

Sunlight at noon has an energy density of about 800 W/m^2. Figure you can cover the surface of a Volt with 2-4 m^2 of panels. Furthermore, assume they're the latest high-efficiency panels which convert 40% of the sunlight to electricity. That would yield 0.64-1.28 kWh per hour. So you'd need 12.5 to 25 hours of noon-time sun to fully charge a Volt's battery.

If you take more realistic figures of sunlight at a 45 degree angle, 2 m^2 of panels, and 15% efficiency, you get 0.17 kWh per hour. It would take you 94 hours, or over a week to fully charge a Volt's battery.

People vastly overestimate the power they can get from sunlight. Solar energy is abundant, but it's very low density.

RE: How modest is modest?
By JasonMick on 2/20/2009 2:25:35 PM , Rating: 2
Kudos, couldn't have calculated it better myself :)

One other tiny point to raise is that only the best lab cells are 40 percent efficient and if I recall that's concentrated solar. Top of the line commercial photovoltaic is around 20 percent so with your calculations it would take 25 to 50 hours for a volt to charge in OPTIMAL sunlight conditions.

An average hour in the sun might return about 1/100 of the battery charge needed. I don't see this as being cost effective for an installation costing $2,000 plus dollars and cutting down on your aerodynamics.

Solar farms are a great idea if solar can become cheaper by new materials and efficiency/manufacturing/installation improvements. Like you said, the energy is plentiful, just not dense.

Solar power for cars is about equally as much fun as flying cars and equally as practical.

RE: How modest is modest?
By ayat101 on 2/21/2009 1:20:09 AM , Rating: 2
... another thing to consider is how much the added weight of the solar cells and charger adds to the energy use of the car.

RE: How modest is modest?
By highlandsun on 2/21/2009 5:54:28 PM , Rating: 3
All negligible. You wouldn't sue crystalline silicon cells on a car, they're too fragile. You'd use thin-film cells, which would add less mass than a coat of paint. And on that score you'd make the car lighter because you wouldn't be painting the surface where the cells are mounted.

As for a charger: you're taking the DC output from a solar array and feeding it to a DC battery. You're not getting anywhere near an amp of output from the array, and if you arrange the parallel/series connections correctly you don't even need to do any voltage conversion. As such, the complexity here is also negligible.

But as already pointed out, none of this is worth doing because the amount of power you can collect from this surface area is also negligible.

Personally, I would still do it, because I drive a black car in Southern California, and it gets way too hot sitting out in the summer. A rooftop mounted solar array to drive the car's ventilation system while it's parked would be excellent. The array itself would keep things cooler simply by absorbing sunlight and turning a fraction of it into electricity instead of directly into heat. I used to have a contact at Sanyo Solar who sold me thin-film amorphous-silicon cells, but they seem to no longer be selling products to individuals, otherwise I would have done this already. And no, none of the clip-on-the-window solar powered fans are large enough/move enough air to keep the car cool, I've tried several.

RE: How modest is modest?
By MrTeal on 2/21/2009 11:38:36 AM , Rating: 2
You can get the latest and greatest triple-junction cells and get 40% efficiency for normal light. Of course, covering 2 m^2 would triple or more the price of the car, but what's several tens of thousands of dollars between eco-friends?

Thanks for posting a realistic number for solar conversion. I see people posting way too often that they'll cover their roof in 100 m^2 of 40% efficient PV cells, seeming to think that they can just go to wal-mart and pick them up, instead of the millions it would actually cost. Monocrystalline Si can get into the low 20s. Standard poly Si that almost all home installations use are stuck in the mid teens.

Alright, enough ranting.

RE: How modest is modest?
By Starcub on 3/18/2009 2:05:34 PM , Rating: 2
Without some hard numbers, I'm inclined to say that there's no way a single (or two) rooftop panels could provide enough electricity to give a Volt a full charge in four hours, on any current commercial battery.

On a Volt, no, you probably couldn't, but on a hybrid you might -- it depends on how you balance power charging and draining. My main point was that you would need a battery large enough, or a power charging scheme that would leave enough energy uncharged for the battery to make up the difference in an 4-8 hour charging cycle. The sun outputs the vast majority of it's energy in the 4 hour space around noon time.

So, even (especially) on a Volt, it might be worth it to install the panels anyway depending on where you live, and how you use your car, and what it would cost to adapt the panels to your car. It depends on how much energy they save you over the lifetime of their usefullness.

RE: How modest is modest?
By randomly on 2/20/2009 2:26:34 PM , Rating: 2
Even covering the top of the car with solar cells won't get you a recharge in 4 hours.

You'll get an average 0.7kwh per square meter per day out of high efficiency panels (17%. That's assuming an unobstructed view of the sky for the full day. You need 8Kwh to recharge a Volt. It's going to take days to accomplish that.

If you must use solar the money is better spent putting the panels on your roof where they will generate far more energy than on your car.
Solar cells on a car won't even come close to paying for themselves during the life of the car. They may take more energy to make than they will ever return.

RE: How modest is modest?
By tastyratz on 2/20/2009 2:34:46 PM , Rating: 2
I contest that statement as well.

While rooftop deployment is not exactly always an ideal situation, if the panels can be made cheap enough and environmentally friendly, it would be in a homeowners best interest to supplement their electrical usage through solar panels.

We might not be looking at a full on replacement through that method, but think of the reduction of draw on the electric grid if people could supply 10-20% of their own power?

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