Slashdot Mirror
Caltech Makes Flexible, 86% Efficient Solar Arrays
strredwolf writes "Caltech has released a flexible solar array that converts 95% of single-wavelength incandescent light and 86% of all sunlight into electricity. Instead of being flat-panel, they stand thin silicon wires in a plastic substrate that scatters the light onto them. The total composition is 98% plastic, 2% wire — the amount of silicon used is 1/50th that of ordinary panels. So as soon as they can get these to market, solar could be very viable and cheap to produce." Update: 03/01 21:02 GMT by KD : Reader axelrosen points out evidence that the 80%+ efficiency figure is wrong. MIT's Tech Review, in covering the Caltech announcement, says that the new panel's efficiency is in the 15%-20% range — which is competitive with the current state of the art. And the Caltech panel should be far cheaper to manufacture.
Holy balls. If this article is spot on, they've doubled the efficiency of the current technology (which converts at about 40%) AND done it in such a way that the stuff is cheaper to manufacture AND made it flexible. This is the sort of thing that can have a real (and probably positive) impact on the world we know. Amazing. The only remaining question (I didn't see anything about it in TFA) is how durable this stuff is compared to the current panels.
This sounds like an incredible breakthrough. I thought that the very best solar cells were at about 40% efficiency. http://www.scientificamerican.com/blog/post.cfm?id=new-solar-cell-efficiency-record-se-2009-08-27
This article describes ~80%. What am I missing? I can't understand why the article is written as it is if these are really the highest efficiency solar cells ever created.
As far as I can figure from the article what is says is 95/86 of the light is absorbed, it doesn't say that all of this light is converted into electricity as is stated here on Slashdot. That is also impressive numbers and very interesting, but my guess is that the efficiency of the solar panel is going to be a lot lower than those numbers posted on the parent, most likely at least a factor 2 lower.
All these idiots working on solar panels when what is really needed is overcast panels to get power from gloomy days when you use more light bulbs.
They whose government reduces their essential liberties for temporary security, receive neither liberty nor security.
It's not incandescent light, it's incident light. sigh.
If we set up solar devices so that they can float in water and function as an interconnected grid, we could drape a network of them over the Pacific Garbage Patch so no one would notice it.
so it is still tied to oil. Becoming cheap and widely popular may do more harm than good I fear.
What's that? A concept in search of venture capital? Oh.
From TFA:
The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight.
I know this is being picky but the article says 85% of sunlight not 86% as in the summary.
So what do I win?
That's all I really want to know. If I can put them on my roof for a reasonable price, I'll be one happy wanker, but lab situations just don't necessarily translate so well into real life.
Not having read the article I don't know whether it was mentioned.
Assuiming that production of these is not too difficult, this seems like a very good way to produce power for you and at least one neighbour just by tiling one roof (I'm pulling the figures for that calculation out of my ass, so if you want to comment on that don't go physics nazi on my ass, please). Imagine only one third of the homeowners doing this kind of thing, we could probably have ourselves a very decentralized power grid in no time. Especially you in the US should welcome that, seeing as your grid has a lot of problems with delivery today.
Anyway, I'm really hoping this turns out to be something of real value. It makes me all giddy with anticipation.
http://www.rsc.org/chemistryworld/News/2010/February/14021001.asp
'We have shown the optical absorption efficiency and charge carrier collection efficiency of a silicon wire array cell is comparable to a conventional silicon cell, but a wire array cell uses up to 100 times less silicon due to enhanced light-trapping effects,' says Atwater. Significantly, the wire arrays absorb infrared light more efficiently that conventional silicon surfaces, further improving the performance of the new device.
So the gist is that it's more efficient because it converts infrared, uses some type of clear polymer with alumina "reflector particles" in place of 99% of the expensive (doped) silicon, and is flexible and therefore easier to manufacture.
"I assumed blithely that there were no elves out there in the darkness"
How durable can this device be? It's made up of 98% plastic.
Muchas Gracias, Señor Edward Snowden !
Cost efficient solar energy is only now 20 years away!! Hooray!
Efficiency of solar panel is and always was 14 to 17%.
Every 3 months or so there is a slashdot article claiming breakthrough in efficiency.
Please stop spreading this meme.
Thank you.
When was the last time you find any plastic that can last 10 years under the sun?
Muchas Gracias, Señor Edward Snowden !
This is interesting work, but it is in a very immature stage of development. They seem to be no where near demonstrating a practical solar cell, and speculated conversion efficiency numbers like 86% are laughable. One of the fundamental limitations of a cell based on Si wires is that the higher a photon's energy is over the bandgap of Si, the more energy is lost as heat. I believe the theoretical maximum conversion efficiency for a Si solar cell is around 30%, and commercially viable cells are limited to around 20% because of practical issues in creating solid state cells such as making electrical contacts to the device, the high cost of making higher efficency (20+%) Si cells. This work doesn't begin to address such issues. I think it is unfortunate that over-hype like this can take luster off of progress in photovoltaics that seems less spectacular but is much closer to practical realization.
Will they float?
Maybe, but what I really want to know: will it blend?
i'd love cheap energy from the sun, but this won't be it.
If you mod me down, I will become more powerful than you can imagine....
If this is true and accurate, this may be one of the biggest energy science advances since nuclear fission. A >75% efficient solar cell that can be manufactured for, say, $100/kW?
I want to believe this is true, and commercialization is just around the corner... because if it is, this could solve our coal-power CO2 emissions overnight.
A 3x4 meter panel of this stuff would run an average North-American home year-round (heating, A/C, hot water), and it sounds like it could cost $1-2k. Even with $5k worth of support hardware (batteries, inverter/charge controller, transfers) this system would pay for itself in under 5 years.
A government is a body of people notably ungoverned - AC
Here's the actual scientific paper, "Predicted Efficiency of Si Wire Array Solar Cells". That's by the same authors mentioned in the press release. While the thing does trap most of the light hitting it, only a fraction of the energy in that light is converted to electricity. In fact, this thing is currently less efficient than the better commercial solar cells.
From the paper: ... simulated photovoltaic efficency of 14.5%. ... Conclusion: ... "Si wire array solar cells have the potential to reach efficiencies competitive with traditional Si crystalline solar cells."
So, an interesting development, but no big breakthrough. There's a claim that it might be a cheaper way to make solar cells, but everybody who comes up with a new design makes that claim. (Nanosolar comes to mind; their technology is supposed to be cheaper, but so far they've spent half a billion dollars and apparently have only produced sample panels.)
The press release specifically says the 90% or so conversion is the internal quantum yield. That means for each for each photon absorbed, 90% of the energy is converted to work. However, this is still a single bandgap material (silicon) and the maximum theoretical external quantum yield for a single bandgap system is 33%. For the 1.12 eV bandgap of silicon, it is 28%. The advantage that Nate and Harry have here is the use of flexible Si based materials, that can use lower quality Si due to the short charge carrier diffusion lengths of the cylindrical system. This represents an inprovement where the cells can be deployed, ie where felxibility is important, and the chance to reduce the cost of the system through less expensive processes for Si manufacture. Now Nate's group is currently working on water splitting with these, using the high aspect ratios to use lower efficiency (and cost) catalysts, and Harry is making radial n-p++ junctions out of these. Neither system is going to rival the external quantum yields of the flat panel Si systems, much less the current photovoltaic champions, the metamorphic triple junctions from Spectrolab, which currently sits at 42.7%, but there is room for cost improvement with this system.
PhD candidate doing my research in new materials for photovoltaics here.
I'm sick and tired of all this mis-reporting. These are NOT 86% efficient cells. If they were, (and they were inexpensive) it would be the greatest discovery in 50 years and it would have been all over every newspaper in the world 2 weeks ago when this paper was published.
They simply absorb 86% of light that hits them. When you say a cell is X% efficient without qualifying it, it's taken to mean power conversion efficiency [PCE] (optical power in/ electrical power out) That and dollars per watt are the numbers that really matter. Read the Nature Materials paper that drove this and you'll see that theory says this design could be up to 17% efficient. That compares unfavorably to mid to high-end commercial cells on the market today.
I'm not saying that this research is a worthless endeavor, maybe they can hit the maximum theoretically possible PCE and keep the cost down. That might have real-world impact.
The caltech news brief quotes Atwater (the PI for this research) as saying that the photons are not only absorbed, but they're also convertedto charge carriers (which is a good step). The problem he doesn't mention here is, these charge carriers loose all their energy (voltage) before they exit the cell. Solve that problem and we've got a winner.
The fundamental issue with nano-structured designs like this is the surface area of the P-N junctions in them. Large surface area means high dark current which means low voltage output. Low voltage output means low PCE. Unfortunately, nothing in this research solves that problem.
86% collection efficiency? Holy cow, that's amazing. Now, if we can just electrolyze water cheaply enough for fuel cells to solve the time-of-use problem, we could free up megatons of metals that currently make up the power grid for other uses.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
reading these slashdot comments reveals a whole lot of confusion about solar cell efficiency.
photons with energy less than the bandgap of the conversion material will not be converted to electrons. photons with energy greater than the bandgap will only convert at the bandgap energy. the high effieincy multijunction cells attempt to address this. multi-exciton generation can happen if the photon is several times the bandgap energy, and there is some hope that quantom dot cells will be able to achieve high efficiency this way though the most effienct qd cells currently get like 5% effiency.
electron-hole recombination happening within the material instead of through the cathode and anode will cause a photon to be released. the higher absorption of the cells in TFA will help keep this photon trapped in the cell, but if it loses energy, it will be less than the bandgap and not be converted again. multijunctions can address this effect somewhat by absorbing the new lower energy photon. high temparature operation also helps increase the likelihood of the electron-hole pair making it to the cathode-anode. the highest effiency cells so far have been achieved by concentrating the lightbeams and then splitting the beams into different colors to be absorbed by different sections.
if you put panels on your roof and you live in a place with cloud cover then it won't be worth using a heliostat system to track the sun so you will suffer loss of the cosine of the angle between your panel and the sun. without tracking the sun you aren't going to be using rainbox concentrators either so you are necessarily using lower efficiency cells too.
Guess someone should try to see what it's like when it uses 6% of the materials then :)
http://www.technologyreview.com/energy/24665/?a=f
It's EQE is 77-85% (above the band-gap).
It's IQE is 90-100% (above the band-gap).
But it's energy conversion is similar to other commercial panels; about 20%.
High absorption and high QE is not enough to get high conversion rates.
You still have the band-gap (the minimum frequency which a photon needs to be able to free an electron from silicon) which excludes up to 30% of all photons, and almost all photons above the band-gap which do free an electron have more energy than is necessary to do so, so the excess is wasted as heat.
Unfortunately the only things to get excited about here are the low cost and flexibility.
who are not in the business of selling power
This is way too good to be true so I'm posting my personal list of typical solar pitfalls previous "solar weasals" have neglected to mention or highlight about their breakthrough technologies. The solar cells are fragile and will only last a short time. They don't cover full spectrum very well for example they may absorb 100% visible but 0% infrared and therefore their effeciency WRT capturing all available energy from the sun while still impressive is cut in half. Use rare exotic materials or are similiarly not suitable for mass production at scale. (IE worthless) The numbers reported only work for concentrated light..IE light that is many hundreds of times brighter than normal sunlight and require solar concentration which implies sun trackers and poor peak conversion effeciencies throughout the cycle of a typical day. Solar cells are not capable of operation at volatges required to produce useful energy or suffer damage..etc when linked in parallel/series groupings needed to produce useful energy. They make subtle factually accurate but weasely misleading claims about effeciency and usefulness most people will fall for. I *HOPE* none of the above apply to the Caltech work. At the very least not day dreaming about changing the world is a positive sign but not speaking directly about conversion effeciencies has certainly raised all kinds of flags in my mind. Its not just what they say...its what they don't say thats often important. I'm still waiting for my surface plasmon powered 500 tetrahertz cell phone CPU that runs for a month at 100% utiliziation between charges.
I guess big oil, energy and coal companies are already in talks about take-over on the new startup.
Just to prevent it from ever entering the market.
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
The roads must roll.
Help stamp out iliturcy.
I keep reading hear on wonderful advancements in the field of solar cells. Like the chick who made solar cells with a pizza oven (is she single, btw?).
But still nothing happens and I can't see people who really deploy solar cells on their roofs - mostly because it takes them 20 years to return the investment (and I think that they die shortly after that)
When is this going to be a reality?
Why is this taking so long?
hemi
How black would these be? They need to get the absorption up to 99.9% so I can have my car painted that color.
Guess it wouldn't be right to call these things "panels", when they are furry. Dang that's a clever idea.
This is my sig.
Why keep banging out heads into the PV wall when you can have cheap hybrid panels that convert 75% of incident energy?
http://www.greenoptimistic.com/2009/04/21/zenithsolar-solar-panels/
Settle for your 20% PV electricity and focus on capturing waste heat.
Is this a problem? Someone posted a funny reply about getting hot water being a feature not a bug, but if it combines producing electricity with hot water, then it is indeed extremely useful a domestic power AND heating unit.
Since the unit is plastic, then presumably having water also pumping through it would be simple.
Donte Alistair Anderson Roberts - hi son!
Karma: Chameleon
at this rate, i expect a story on slashdot next month (after 5 such stories of this subject matter in the interim) about solar panels that function at 375% efficiency, make you coffee in the morning, and solve the israeli-palestinian conflict on its days off
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
Ok, I really have to admit that I totally don't understand what the significance of solar panel efficiency actually means, so I wonder if someone can enlighten me as to what exactly it means when a solar panel is X% efficient? Any kind of "for preschoolers" explanation would be greatly appreciated, such as what "100% solar power conversion efficiency" actually would mean and how that imaginative 100% number is actually reached would also be good. Anyone up to explaining that?
But usually Godwin's Law is invoked with a comparison to the Nazi's as evil. Here it's a reference to not-Nazi's as not-evil.
My brain hurts.
Infuriate left and right
I commented on the submission yesterday and explained that the summary is wrong. But it seems noone bothered to read it.
"as soon as they can get these to market, solar could be very viable and cheap to produce." And if a frog had wings his ass wouldn't bump the ground when he hops.
I appreciate Slashdot acting like an old Popular Mechanics here, but I wouldn't get too excited just yet. As somebody pointed out in another forum, when you compare ethanol with gasoline in terms of efficiency, if all we had was ethanol primarily from "corn" (U.S. term, UK term is "maize") and then someone invented gasoline, we would be raving about the improvement in efficiency and economy. IOW, I will believe cheap, efficient solar power when I see it on the neighbor's roof. Until then, this is one more expensive quest for a pot of gold at the end of a rainbow. In the meantime, we could be practicing more energy efficiency.
FWIW, I knew W was full of crap with that whole "hydrogen economy" nonsense back around 2005. That was an absurd sop to deflect a little criticism that he was as much a tool of Big Oil as his Old Man. Make note that I served in Iraq during Operation Desert Storm and when it was over, George H.W. Bush was sitting on a 91 percent approval rating based on a war we had to fight to maintain a steady supply of petroleum for the Western Powers and Japan. From the desert, I wrote my Senators and lobbied them to get a bill going to get us to start weaning off Mideast Oil. That S.O.B. Bush didn't raise a finger, nor did our Congress and eventually Western wealth transfer begat Osama Bin Laden, 9/11, Iraq War II, and Afghanistan. Wouldn't you think a 91 percent approval rating might have been enough political capital to change things a little? It may even have made Bush the Elder seem like the President of the U.S.A. instead of President of the New World Order since he rightfully earned a reputation for being allergic to domestic policy. His detachment had a lot to do with getting booted in '92. A review of the stock market back in '90 - '91 reveals that Big Oil shot up and helped a lot of folks in that business recover from the very hard times they went through in the late '80's. Though I was a conservative and a combat veteran, I campaigned for Bill Clinton in '92 as I was so disgusted with Bush the Elder. Still am. God save us from another Bush.
Most of us know in our heart of hearts that our troops are in Iraq and Afghanistan because of the continued grip the Mideast has on Western economies. In World War II, the U.S. national speed limit was 35 mph and gasoline was rationed with coupons. This was done to make sure the military had plenty of fuel. If some shared sacrifice was called for now, I think most Americans would grumble, but go along with it for the sake of untangling from the Iraq and Afghan Wars. How about bringing back the 55 mph speed limit of the '70's and '80's? What about a tax based on the weight of a vehicle? If we cut back on petroleum use, we help our independence and the environment at the same time. Now that's what I call "conserve-atism".
If you want to see what needs to be done about our dependence on petroleum, just look for the occasional Charles Krauthammer piece on it. He makes the same recommendations about every 5 years, the centerpiece of which is a flexible tax on gasoline that seeks to wean us off cheap oil while keeping the price of gasoline fairly steady.
In principio erat Verbum.
Consider the following reasons:
Here's a quick back-of-the-envelope calculation. First, assume:
Given all of this, you must recover 10% of the initial cost each year. Electricity costs you $0.20/KWH, you install an array with a maximum output of 10KW. Given seasons, clouds, etc, if you live in a reasonably sunny climate, you might average 60KWH/day, or 22MWH/year. That corresponds to a maximum savings of $4400/year, meaning that you could spend $44,000 for your 10KW solar array. The cheapest manufacturers quote prices in that range (not including installation). Which means that solar power can, just barely, make sense for an idealist.
Moreover, lots of power companies do not really want to buy your excess power, and certainly not at full retail price. Hence, depending on where you live, there may be additional barriers to overcome.
Enjoy life! This is not a dress rehearsal.
well they sort of signed their own death warrant. no one 'major' will allow this. it and they will be buried like all other interesting projects. :). Ta-Ta.
so enjoy the spotlight... err the spot from laser light
Slashdot editors are snookered again by B.S. press release.
If you'll send me $100, I'll send you up to $200!!!
She was like chocolate when she drank... semi-sweet at first and then increasingly bitter.
The original article is poorly written (no, not even close to 86% you stupid twats) and kdawson is equally foolish for echoing this garbage. This is why this site sucks. Brain-dead slashdot editors, time and time again, post shitty articles that make extraordinary claims which end up being completely false or misleading.
I don't understand why the break-even time on solar has to be on the order of a handful of years for it to be economically feasible.
The break-even time for nuclear is over a decade, and it's pretty long for hydro projects too. So why do we insist that solar has to turn a profit Real Quick Now?
Part of the the reason people seek a short break-even time is, incredibly enough, the success of solar research.
The rapid advancement of any technology always gives an incentive to hold off; I know people who refused to upgrade their computers for several years because price drops or performance increases were always just a few months around the corner. In isolation it may be economically viable to place solar panels on your roof, but the cost per watt of solar power just keeps dropping. It's potentially cheaper, and certainly less risky, to hold off on buying solar panels until the next batch of innovations hit the shelves. One way to mitigate that risk is for solar to turn a faster profit.
Slashdot, please think of the children that will be disappointed by this article.
Us grownups can see through the PR-speak, but kids can't.
We can see that this loose talk of high efficiencies is just that-- only part of the story.
It's swell that these gizmos have a 97% absorption efficiency, but that's only the front end.
The actual cell, which converts the light to electricity, is no different-- about 16% efficient, due
to the many mismatches in energy levels and the unavoidable phonon products.
Plus the business about needing less silicon is not spreadsheet-worthy. The actual bulk silicon is not a large part of the cost.
Even if they got the silicon usage down to 0%, the cost would not come down very much if at all.
Also the economic predictions are unrealistic. Nothing that's better has ever sold for less than 5% under the price of the competition. No company can afford to leave money on the table.
The frog still gets the same effect when hopping. Also, you might want to start crossing cold fusion off the auto-mock list: http://www.lenr-canr.org/acrobat/BarnhartBtechnology.pdf
Just like clockwork, there's another article on slashdot containing 'if they can get to market, solar panel prices could plummet!', which is nothing more than disingenuous wharrgarble. I see these articles every 2-3 months, and it's still Way Too Friggin' Expensive to pick up solar panels at my local store.
Call me when a 15 amp @ 14.1v isn't $1000 or higher, and we'll talk.
Solar panels often have a limited return-on-investment because they also have a limited lifespan. The efficiency and energy output of a solar panel declines over time, estimates are often at 1% per year. While nuclear, coal, hydro, and other power generation mechanisms have modular, maintainable, repairable parts, solar panels are usually an all-or-nothing replacement option. So if you invest in solar panels that generate 10 kWh of electricity on a bright shiny day when they are installed, they will probably only generate 8 kWh after 20 years. YMMV, and different manufacturing techniques will produce different results, which can be modeled theoretically, but as every good engineer should consider, the best way to measure degradation is to measure output (for a manufacturing technique, statistical sampling of manufactured batches, etc) for a number of years to determine how much degradation occurs. Solar panel manufacturing is still very much a "wild west" technology, with new innovations coming out faster than hard data on reliability and efficiency, which doesn't make solar any less cool, it just makes it more difficult to accurately estimate ROI or energy savings.
....That's the only question of interest.
Regards;
Solar PV is roughly 20x-100x more expensive than coal or nuclear power.
Really? Did you also subtract the subsidies coal and nuclear power get? Yes, they both get subsidized as well.
If I was Obama, I'd toss a billion or so at this scientist and see if he couldn't get mass production of it up and running.
Ah if only... If I were President of the USA I'd veto all subsidies and let a freer market pick winners and losers. As it is now venture capitalists have been investing in different technologies for years, from Sergey Brin and Larry Page investing in Nanosolar to Elon Musk, founder of Paypal and CEO of SpaceX, investing in Tesla Motors.
I mean, as long as we're spending billionS keeping teachers temporarily employed (because their states can't afford them right now), right?
I hate it that the feds have to give the states the money but it was the feds who mandated a bunch of new regulations with No Child Left Behind and other laws. If the feds stayed within it's Constitutional limits federal taxes could be significantly reduced if not totally eliminate the federal income tax. States and local governments could then raise their own taxes if they so chose to. Of course that's only part of the problem. States like California went on a spending spree during the roaring '90s. Then when the economy tanked they lost a lot of revenue. Then there's CA's teachers unions. Try to fire an underperforming teacher and watch the years speed by before they are fired. About the only way to fight the unions is by allowing school choice with charter and private schools getting matching funding. Then watch as the bad public schools are emptied out so the teachers can be fired.
Falcon
Should there be a Law?
I thought the theoretical limit for solar to electrical conversion was about 40%?
This 86% inside that 40% limit? I thought they were talking about radiation absorption in which case the power would be much less and the panels would heat up and likely pose another issue (unless you can run water behind them and use it as a heater which is the best use for solar anyhow.)
What about that new thing I saw on the BBC last year which was working on radio-like antennas for the IR wavelength?? Seemed to me to be a good idea.
Democracy Now! - uncensored, anti-establishment news
I've observed that traditional solar cells produce the highest output when the panels are cool. If these perform the same way, using them to heat water or something else to draw off excess heat might be necessary to achieve maximum electrical generation.
Heating water may be a bonus, or, plain and simply better. Solar thermal, hot water, systems work better in some places than PVs do.
Falcon
Should there be a Law?
The problem with current panels isn't the efficiency. More efficiency is welcome but the real problem with solar panels is the cost. It takes too many years to recoup the very heavy initial investment. If the price can be made such that the panels pay for themselves with 2 or 3 years then they make solar power a real alternative to the grid.
No the initial cost isn't a problem either. The problem is people's expectation. They want it paid off last year. Think the coal or nuclear power plant has been paid off after 10 years? Without subsidies they may never be paid for. Here's an investment opportunity in Southern Africa with a minimum expected payback period of 25 years.
Falcon
Should there be a Law?
Google cache version: http://bit.ly/ck4eUh
1. total cost (panels are expensive
Coal fired and nuclear power plants aren't expensive? Neither coal companies nor the nuclear power industry have their hands out begging for government assistance? Cost Is Chief Barrier to 'Clean Coal' and the Nuclear power industry is Hooked on Subsidies. "Nuclear power appeals to state planners, not market actors."
2. the Return on Investment is low (extreme cases - 10 years, but typically more than 20).
The payback period can be much shorter than that. In one survey New Jersey had a payback period of 1.5 years. New York had a payback period of 3 years and Delaware 6 for residential applications.
Falcon
Should there be a Law?
you are worth more to the banks as an energy consumer than as an energy producer.
Solar power in cities
Off grid solar power
Solar power for rural properties
Falcon
Should there be a Law?
The ability to communicate and run your refrigerator in, say, a hurricane-induced blackout makes the system more valuable than simply what it can displace from your electric bill each month.
The problem with this, islanding, is that it's dangerous to utility workers. If the power from the utility comes out and workers are sent out for repairs they can get electrocuted. To prevent this the inverter has to disconnect from the grid. Grid-tie inverters are made to disconnect and turn off though. So if you still want power then a second inverter, or more, has to be used to connect the storage batteries to the building wiring with that one then feeding the grid-tie inverter.
A more efficient (and cheaper) technology would make a small solar power backup system closer to a gas generator as far as ease of use and energy density.
Some people use a small generator as their backup for when there's little sun and or wind. Converting the engine to run on alcohol or biodiesel allows you to make your own fuel for it.
Falcon
Should there be a Law?
Only because coal is subsidized and it is allowed to pass external costs to others.
If I could pay less than 10k and have a 10 year pay back time
You can pay less than that, you may or you may not find it worthwhile though. And today the payback period is less than 10 years. For residential systems New Jersey has a payback period of 1.5 years. "New York and Delaware are next in line with payback in 3-6 years, and California, Maryland, Massachusetts and Wisconsin all tied for fourth at seven years."
The fact that governments keep trying to shift this cost to individual households tells me that it just isn't worth it.
First, I'd rather taxpayers be subsidized before megacorporations are. What I really want is for the federal government to stop all subsidies and return the money back to taxpayers. Then allow them to decide what they will pay for themselves. As it is now though your electricity from coal and nuclear power is subsidized. Chevron's CEO agrees to lobby with Sierra Club to end coal subsidies. And here's Rep Edward Markey crowing about how My Climate Bill 'Has Huge Subsidies For Clean Coal! Huge!'. In that speech he lists some of the subsidies large power companies including coal and nuclear power get. It comes to tens of billions of dollars. If however you add up all the subsides geothermal, solar, wind and other alternative and renewable energy sources get, it doesn't add up to $! Billion.
Fact is is conventional energy sources are massively subsidized with taxpayer money.
Falcon
Should there be a Law?
http://www.greenoptimistic.com/2009/04/21/zenithsolar-solar-panels/
Solar thermal to heat water as your link bring up has a better payback period than solar PVs do for many people. Of course what has the quickest payback period is increasing insulation.
Falcon
Should there be a Law?
Right now, solar cells are so expensive, they take something like 15 or 20 years to pay for themselves, so most property owners don't see a big incentive. Lower that price to 10 years or 8 years, or even lower, and suddenly the demand for these things will skyrocket.
The payback period for solar is already under 10 years. New Jersey has a payback period of 1.5 years, "New York and Delaware are next in line with payback in 3-6 years, and California, Maryland, Massachusetts and Wisconsin all tied for fourth at seven years." Of course, if because of this everybody went out and started buying solar energy systems, the cost could go up, higher demand drive prices up. Then again because of economy of scale and competition prices could go down even more.
Falcon
Should there be a Law?
At the risk of beating a dead horse, I take issue with the Update on the post. The researchers have not made a solar panel or a solar cell. They have made a sheet of "photoactive" material and have measured how it absorbs light. The MIT Tech Review article says "Computational models suggest that the material could be used to make solar cells that would convert 15 to 20 percent of the energy in sunlight into electricity". Such models are highly dubious when actual solar cells have not been demonstrated, and major identifiable hurdles need to be crossed before that happens. Although I agree with other posters that it is significant that very little Si is required in this material, it is hard to say much about manufacturing cost either before a working device or device architecture exists.
Why so seriously skeptic?
Because Nanosolar has supposedly been shipping for three years and there are no visible installations.
Just because they have pictures of a factory interior doesn't mean they have a factory that delivers working product at the claimed cost. It's all too common to see some minor advance in materials science hyped into something becoming real cheap, real soon now. Most of the roll-to-roll processes for making solar cells don't work.
Not all of them, though. Uni-Solar Ovonic really does have a working roll to roll process for making flexible solar cells. You can order their products, they have a dealer network, and they have many installations. Nanosolar has none of that. Just hype.
Amen to that. I put $400 worth of insulation in my attic last year and cut my heating and cooling effort by 30% - paid for itself in 12 months.
If only more people knew about it. Of course you run into people like Dick Cheney who said that while conservation might be a "personal virtue," conservation alone was not "a sufficient basis for a sound, comprehensive energy policy." Too many people hear stuff like that and believe it.
Falcon
Should there be a Law?
Efficency is only part of the equation what is the ammount of power produced per square foot?
-Eric
I speak from a more pragmatic point of view (as someone who works with hundreds of teachers every year) - teachers unions are almost entirely counterproductive to the process of education.
As you say "Correlation is not causation."
Falcon
Should there be a Law?
When I'm trying to give a workshop to improve teachers' technical skills in the educational world, and the union blocks it, that's a direct hit to their ability to teach.
Does that happen everywhere all the tyme, or just in some places? Just because one or two unions may do that does not mean they all do. Nor does it mean they don't want teachers to improve.
Remember for it to be science it has to have reproducible effects, and if just in one case the effect isn't the same then either the hypothesis predicts it needs to be adjusted to account for different outcomes or it's false. I bet there are plenty of places with teachers' unions who don't have the effects you say, like almost every state that ranks above the below average North Carolina schools.
Falcon
Should there be a Law?
Good luck to you! I'm in school right now for Electrical Engineering, and am dreading the fallout from my loans. I'm interested in working in RE somehow as well, not necessarily as an installer but maybe designing components. (I'm actually going to start on a homemade inverter pretty soon, not for intertie of course.) I think there will be a great opportunity for this sort of industry pretty soon, as the cost goes down and more people become aware of just what you can do. Just keep at it, the future will be pretty exciting.
Thanks. Years ago my major was Computer Engineering, so if I go with a major study area of Electrical or Electronic Engineering now I'll still study engineering. Thing is is I'll have to retake a number of classes such as chemistry, math, and physics. Of them all I had left to take was Thermodynamics. But because of bad memory I'd have to review if not retake them all. I'd be basically starting all again. As for working in RE many people start out as installers but as they work, and learn, they start designing as well. Going that route you know what can be done, which reminds me of a friend in college. He was a steel worker on skyscrapers before starting college as an Architectural Engineer and he used to say that if someone on a crew of his came up and said they could not be do something in his plans he'd try to do it himself and if he could it then he'd fire that person.
Just keep at it, the future will be pretty exciting.
Oh I believe things will be interesting. My problem is that I'm so tired. I've been fighting for a life with meaning for more than 10 years but as I said before I'll tired and don't really have much hope anymore. There are only two things that keep me going, trying. One is, as my therapists have said, stubbornness. I have had therapists and neurologists say I only lived because I was stubborn. The other thing is that although I no longer do I used to believe in reincarnation. Occasionally I'd think of ending the pain and suffering but then think that if reincarnation were true then I'd have to come back and go through it in another life. I know it's not rational or logical but neither one could touch it, the fear.
Falcon
Should there be a Law?
Thermodynamics for a CE? I guess it varies by school but I didn't realize many places had that as a requirement (or still did, at least). You might want to look around, you never know what another school might be willing to transfer.
I don't recall if Thermodynamics was required for a CE degree but there was one more physics class that was required. Now I did have all the math classes needed. However because to get a minor in physics I only needed to take 2 more physics classes and the same for math I decided to take those 4 more classes. So I would have ended up with a degree in CE and minors in math and physics.
Depending on how it's looked at, if I knew in high school what I know now I'd have done better or worse than a major and 2 minors. If I knew then what I know now I'd have done a double major. In high school I wanted to do both computer engineering and a marine science, marine bio or oceanography perhaps. I loved and took classes in both. As part of the marine biology class and club I was in a group of us went to Mote Marine Laboratory on a field trip. Before leaving there a couple of us were pulled aside and asked if we wanted to work there during the summer. We were told that if we did and we wanted to major in a marine science in college they'd help us get in and pay for it. By then I had basically decided I wanted to design computer systems though, so I turned it down.
Obviously people believe a lot of things. Who knows, maybe we do reincarnate? But the truth is the only thing we can be sure of, the thing we don't need to 'believe' in because we know it, is that we're here - 'I think therefore I am.' There's a time and a place for stubbornness, and I suppose when it comes to something like that.
Back when, before my accident, spirituality was important to me. Spirituality not religion. And though I still recall what beliefs I had I no longer believe them. As I've said here and other places I am agnostic, "a" without and "gnosis" knowledge. Thing is, with living I always believed and told my family I'd rather be disconnected and have all the lines and tubes pulled so that I'd die if it came to being a vegetable or dying. I don't recall it but one of my sisters' told me that after I came out of the coma I was in in the hospital I screamed at everyone to let me die.
Falcon
Should there be a Law?