Slashdot Mirror
40% Efficiency Solar Cells Developed
gtada writes "A story published at Physorg.com discusses recently published research into the fabrication of solar cells that surpass the 40% efficiency milestone. Such devices would be the high water-mark to date, and hint at the possibility of even more effective technology. 'In the design, multijunction cells divide the broad solar spectrum into three smaller sections by using three subcell band gaps. Each of the subcells can capture a different wavelength range of light, enabling each subcell to efficiently convert that light into electricity. With their conversion efficiency measured at 40.7%, the metamorphic multijunction concentrator cells surpass the theoretical limit of 37% of single-junction cells at 1000 suns, due to their multijunction structure.'"
There is really no shortage of sunlight anyways. If only solar cells could be made cheaply. I suppose this will be great for satellites though.
not even remotely. plants are efficient at converting photons to an immediate energy source but the vast majority is used to keep the existing tissues alive and functioning. esimates I have seen for the efficiency of converting light, CO2 and water into biomass ranges from less than 1% to 5% depending on the species.
Sigs are too short to say anything truly profound so read the above post instead.
- Efficiency: This article talks about brightnesses of 100 suns. Well what about 1 sun? Or fraction of that (cloudyness)? Are these efficiencies realized then too? If not, does the technology still work at or near where that is?
- Power cost: I've seen it said that many solar cells don't give back the energy required to manufacture them. By that I mean, acquiring the materials (mining, etc), refining them, and manufacturing them all take energy. How many days/months/years would it take to "pay back" the cost of manufacture, in energy?
- Temperature performance differences: How does it perform in low (or high) temperatures? A lot of us live in places where it gets cold for long periods of the year. This also has the associated problems with snow build-up, and getting that OFF of the panels.
- Monetary cost: How much will this cost at the consumer level, for which wattages? How big would they have to be to cover some typical consumer usages?
- Power storage: With solar, it all eventually comes back to storing the power, as they obviously don't operate in darkness. So how much would the batteries cost (initially, and in maintenance) to make this a viable power solution? How much wattage would you need to have enough "storage" for nighttime? Or more practically, for a few cloudy/rainy days in a row?
Some of these issues are universal to ANY solar technology, but some of them are specific to this as well. All need real answers.Solar is by far my favorite power source. But like every other power source, it is really just a byproduct of the actual energetic reaction. I think I can accurately say that solar power is second-hand nuclear power. Following this reasoning the other power sources may be seen as third-hand nuclear power.
As another posted stated, even if you make the solar 100% efficient (wouldn't that be something!) you still have to store or transport it - since on average the sun is hitting half the Earth's surface at any given time (with much of that surface being water).
I have high hopes for solar - but it always strikes me as strange that we already have this amazing technology of nuclear power - it's here now! We HAVE it!
Plus, nuclear power can make a nuclear rocket! I don't know of any solar rockets yet.
Read my Very Short "Stories"
This is good news. I can not wait to have affordable solar cells to power a laptop. On board colar panels until now only can extend battery life for a laptop. There are foldable panels which generate enough power (26 watts) for a power friendly laptop: http://www.ascscientific.com/solar.html For a laptop with solid state harddrive and power friendly CPU, onboard solar cells might soon be enough.
You might want to re-check your calculations. Total world energy usage is ~15 TW. Light at surface averages ~342 W/m.
Land surface is 148,939,100 km
(1.5*10^13 TW / [0.4 *342 W/m]) / 148939100000000 m = ~ 0.07%. Let's double it for extra capacity (and because half the planet is in night), and we're still under 0.15% of the land surface area. Your 8% estimate is large by a factor of 50 or so.
Of course, putting the whole thing in space might make more sense. If you really want pie-in-the-sky thinking, covering the moon with 10% efficient solar cells would provide about 86 times the power the world uses now. Getting it all back to Earth would be the tricky part.
Though I also agree we should be using better nuclear reactors.
Making an acre of algae may be easy, but harvesting it sure isn't... At least no where near easy compared to "harvesting" the results of a solar cell. How much energy would it take to retrieve all the combustible material from your acre of pond?
- You are opposed to the long term radiactive waste? This burns up nearly ALL the energy that is left to cause 1000's of years of radiation.
- Opposed to paying terrorists to blow us up? So am I. This would enable a true electrical society.
- Tired of a yo-yo effect on pricing? So am I. Nearly all of the fuel that would be loaded in these, we have ready to bury in the ground. Once loaded, there would be no change in the fuel price.
- Do not like the safety record of the nuclear industry (though it is actually excellent)? This has the advantage that it is a TOTAL passive safty. The only way that it is going wrong is if you can blow it up (which would require a nuke to do), or if you can bend the laws of physic.
- Do not like the idea of plutonium being produced. Well, this is a breeder reactor so there is plutonium, but wrong kind AND it is all enclosed. NOTHING could get close to it until the entire system is shut down. Permantly.
There is nothing by upsides, relatively few downsides. The biggest one, is that it was killed. Kerry pushed Clinton to not build it. Poppa bush had it MOST of the way built. Even now, W. could re-start the program and within 4 years, we would have an active IFR. Within a decade, we would be starting to build these en-mass. Now, a decade may sound like a LONG time, but it really is not. Once we built 6 of these, then we could accelerate the pace. That would mean within 20 years, we would be putting nothing but these AND alternative power. IOW, we would be in major production BEFORE the fusion reactor is suppose to come on line for a sustainable fusion. The IFR was shutdown for PURE political reasons, not scientific.I prefer the "u" in honour as it seems to be missing these days.
Thank you... One of the things that originally drew me to reading Slashdot was that when someone would make an outlandish comment, someone else would 'run the numbers'. It's good to see that some traditions are not completely dead.
You also need to account for cloudy weather, and the fact that solar cells produce power dependant on the angle of the sun - the quoted efficiency is for noon only, it drops off sharply the rest of the time (cosine function, IIRC), growing worse as you get further from the equator. Also, the fact that a significant of the Earth's land area has long nights and short days for half the year screws things up more (you can't really store the energy from summer for use in winter, and the northern and southern land masses don't balance, you're going to lose out on one of them). Without spending time to look up the real figures, my back-of-the-envelope scribblings comes to about 1/5 of that amount of power. 8% is still too large, but not by that much. The right figure is probably somewhere in the vicinity of 1%.
Lastly, you need to account for the energy cost of producing solar cells, and that one is a real killer. I could easily believe that 8% is the right figure for 10%-efficient solar cells, once that has been factored in. New technologies like the one in the article can only help with this, but we need to keep improving them a lot before solar power is viable as a primary power source (rather than a backup to reduce the load on dirty coal and oil burners).
More practical would be pushing the energy consumers out there - how much is manufacturing and computer hardware that could run quite happily on the moon, and just ship back the products? Dropping manufactured items down to Earth is much easier (although it's still highly effective as a weapon, c.f. Heinlein's "The moon is a harsh mistress"), and the latency of internet access would only be a few seconds.