Solar Cell Achieves 40% Efficiency

Fysiks Wurks found on the U.S. Department of Energy website news of a breakthrough in solar energy efficiency. From the article: "...with DOE funding, a concentrator solar cell produced by Boeing-Spectrolab has recently achieved a world-record conversion efficiency of 40.7 percent, establishing a new milestone in sunlight-to-electricity performance." A page linked from Wikipedia's article on solar energy calculates the land area that would need to be covered by solar collectors at 8% efficiency to meet the world's energy needs (using 2003 figures). At 40% efficiency, it looks like a square 265 miles on a side in the American southwest would do it.

Comments

transport losses?

[toQDuj]

yes, a few hundred miles in the american southwest would do it (anyone objecting to using Texas?), but only if the entire world lived in the american southwest. As it is, energy losses due to transportation are quite significant and hinder an all-out world power source plan.

B.

Re:transport losses?

[dew-genen-ny]

When you say energy losses due to transportation, are you just talking about transmission over wires?

How about conversion to something like hydrogen?

There are lots of desert areas that I'm sure could be used for energy generation, at least it would be better than polluting our way to global death....

Re:transport losses?

[Anonymous Coward]

As it is, energy losses due to transportation are quite significant and hinder an all-out world power source plan.

Also the fact that USA is hostile to the rest of the world and extremely selfish, means no other country could trust it as a source of energy anyway. Example about the area was there just to illustrate, not as a concrete suggestion how energy needs of the world should be solved. There might be even better places in Sahara, but we'd still face the problems of moving the energy efficiently. Luckily, solar energy is quite easy to decentralize, however not suitable for every country.

Re:transport losses?

[nicholas.]

And yet somehow we have no problems tranporting oil to non-oil producing regions. A huge solar farm could produce massive amounts of hydrogen. And hydrogen transports just as easily as oil via the same infrastruture. Cheap, unlimited, nearly clean energy and all we have to do is build it. I bet (no figures nor money to back me up) that we could have built several solar farms for the cost of one war in Iraq --not that I'm getting the two issues confused ; )

Re:transport losses?

[jtorkbob]

Hydrogen conversion has its own inefficiency, so that's out.

That statistic is simply an illustration in any case. Obviously there are some other places in the world where such installations could be put; perhaps some less sunny ones would require more space to reach equivalent capacity.

In any case, I think that a 100% solar earth is unlikely:

* Much of the time it is night, and storing that much juice in batteries is impractical. Things like hydroelectric storage and thermal solar plants could help with this problem, but its a whole different research issue.
* In the event of, say, a major volcanic eruption or meteor impact, world power production would plummet. That could be the least of our worries.

Solar and wind are like the icing on the clean power cake. They are great for the role they serve, but you can't have them for dinner without getting a stomach ache.

Re:transport losses?

[poopdeville]

I think the best use for this technology would be to put it on every roof in in America (and Europe and eventually the world), and use nuclear power as a method to buffer against periods of low sunlight.

While the major volcano/meteor event you mentioned could deplete the nuclear buffer, it would do that (and worse) now.

At the very least, considering the effects on the economy that nearly free energy would have, we could build enough nuclear power plants to completely handle our energy needs in case such an unfortunate turn of events occured. Hell, we could sell of the surplus nuclear energy to subsidize projects like the complete mechanization of food production, -- obviously using our nearly free energy. Or just lower taxes (though I would prefer the former)

Re:transport losses?

[mubes]

With the exception of nuclear power we already have a 100% solar earth to all intents and purposes. It's just the conversion techniques that vary.

Re:transport losses?

[jtorkbob]

I think the best use for this technology would be to put it on every roof in in America (and Europe and eventually the world), and use nuclear power as a method to buffer against periods of low sunlight.

I agree that local micro power is another good peice of the puzzle. My number one goal in life is to eventually live in a home with a net energy surplus. Of course, my penchant for running Linux on old hardware might turn into a barrier to this.

While the major volcano/meteor event you mentioned could deplete the nuclear buffer, it would do that (and worse) now.

Well, given a 'minor' event like Mt. Saint Helens, light blocking would only be a minor concern to the overall energy supply as we have it now. Obviously ash and debris in equipment, supply chain interruption and so on would be another issue entirely.

Hell, we could sell of the surplus nuclear energy to subsidize projects like the complete mechanization of food production, -- obviously using our nearly free energy. Or just lower taxes (though I would prefer the former)

Well, that's a different question, one I hadn't considered too deeply. Still, until we develop a 'perfect' single energy source a la Mr. Fusion, there will have to be a wide variety of energy sources in order to have a stable energy system. Nuclear/fossil systems require finite and largely imported fuel. Wind, solar and geothermal require specific geography. Hydroelectric fsks up the ecosystem. Each has its place in the ideal system, however limited.

Re:transport losses?

[Eivind]

Sure. That's actually another *advantage* of solar.

It's a lot more practical to scatter a large numer of smaller solar-plants around than it is to do the same with nuclear, oil or coal-powered plants.

If you do this, for example, by installing them on the roofs of homes you get 2 extra benefits:

• It makes the house less hot. If 40% of the sun is converted to electricity, then that's 40% which is *not* converted to heat. Decreases the demand for AC.
• It produces the most power precisely on the days when the demands on the grid is at its peak. (assuming warm/sunny areas) Which, is optimal if your goal is reducing the strain on the grid.

Re:transport losses?

[Eivind]

But that's just non-useful pedantry.

At a large enough distance, all things are the same. Which removes distinctions which in real life are useful.

For example, the phrase "renewable energy-source" actually has meaning. True, one can claim that *no* energy-source is renewable -- because entropy will always increase, and for example solar-power is nuclear, and infact the sun is going to run out of fuel at some point.

Or you could argue the oposite; that pretty much all energy-sources are renewable; oil coal and gas come from organic matter afterall, so given a long enough time, there's no reason why they shouldn't renew.

But this is just playing word-games. You've told nobody anything new with this. We're talking here and now and on human timescales.

Oil won't renew -- in the next 10, 100 or 1000 years. So for practical purposes it's non-renewable.

The sun won't run out of hydrogen the next 10, 100 or 1000 years, and furthermore it doesn't run out any faster if we install solar-cells. So for all practical purposes, the sun is a constant source of energy.

Re:transport losses?

[JohnFluxx]

As opposed to the cost of electricity for the whole world over then next 30 or so years?

How much is the total electric bill for the world?

Re:transport losses?

[Dr. Spork]

Realistically, I don't think that any nuclear station would need to have down-time. If the public grid was producing enough of its own power, the nuclear plant's energy would go to hydrogen electrolysis. After all, even in an energy utopia, we'll need energy in some sort of a transportable form - say for cars and rockets.

Re:transport losses?

[indifferent children]

Is energy really expensive enough to justify covering your house in solar cells?

Energy as we collect it now, has some non-obvious costs. What does pollution from burning fossil fuels cost us in terms of healthcare? What will sea-level rise cost us? (hint: NYC, LA, DC, Miami, New Orleans, Mobile, and others are very close to sea level, and those are just the US examples.) Would we really have spent $300B and 2,906 American lives (so far) in Iraq if we didn't need to "stabilize" the region that supplies most of our oil?

Part of every dollar that you pay in taxes, at the store, at the hospital, in fact pretty much everywhere, is an energy cost.

Re:transport losses?

[Lopton]

Yes you will keep fissioning at low levels, but it uses way less fuel. Core life is measured based the hours at full power, if you operate at a really low level of power you extend core life drasticaly. There are also many ways to maintain a plant in a stable, shut down condition to where it can be restarted quickly, the Navy has been doing this for many many years. The significant start-up times come when you have to cool the plant down drasticly for maintenance.

Re:transport losses?

[maxwell demon]

The problem with solar panels is PRICE. That is the nut that needs to be cracked. If a panel is only 10% efficient, but not much more expensive than a similar sized roofing slate, it suddenly becomes economical to re-roof the house the next time the roof needs attention. However, it's not even near that price. An 80 watt panel currently costs around GBP£250 which is fantastically expensive. There is no way I could even remotely afford solar roofing at those prices, however much I'd like it. The price per peak watt needs to be about a tenth of what it is now.
  According to the article, the new solar cells would cost about $3/watt. I don't really know the exchange rate between $ and £, but AFAIR it's about a factor of two. That would give £120 for an 80 watt panel. Still not 1/10th, but at least less than half the price.

Also note that in your calculation you also have to add the savings in electricity. That is, you don't have to have equal price to conventional roofing, but you have to have the equal proce of conventional roofing plus the saved payment of electricity in some reasonable amount of time. So if the money saved on your electricity bill in, say, the next three years makes up for the extra cost of solar cell roofing, it's still more profitable to do it. (Well, actually you'll also have to account for the interest you would have gotten for the money during that time, because the money you pay for electricity next year will still give interest this year, while the money you spent on the solar panel will not.)

Re:transport losses?

[QuantumPion]

This isn't quite correct. First, nuclear fuel doesn't get used up if it is not at power. The neutron flux at shutdown, compared to full power, is many orders of magnitude lower. The amount fuel is depleted is called the burnup, and is measured in gigawatt-days per metric ton uranium. Typical fuel is designed to last 40-60 gwd/mtu. If the reactor is at low power, the fuel will not be depleted at a significant rate. However, there are issues with running at low power for extended periods of time, this is because "burning" the fuel with control rods in causes axial asymmetry.

Second, power reactors can remain hot at zero power for extended periods of time (called hot-zero-power or hot-standby). In PWR's, the reactor is designed to operate at a certain temperature (usually around 580 degrees F and 2250 psi). The reactor cannot be operated at colder then 540 degrees or so, due to physics limitations (moderator temperature coefficient, thermal stresses, etc). The way PWR's initially heat up the coolant at the beginning of a cycle is by simply running the coolant pumps. The pumps that circulate the coolant are monstrous (~7000 hp) and can heat up the system to operating temperatures all by themselves. They also keep the water at hot conditions while the reactor is at zero power.

In a world powered entirely by solar panels, large nuclear power plants for use at night or in case of volcano would work just fine. This is because if they were needed, they would be operating at 100% as base load plants.

Re:transport losses?

[Dare nMc]

The best solution, at least in built up areas, would be to have the national grid fed by solar cells, rather than individual houses having them

NO, get rid of that power robbing, terroist target, lightning rod, ice gathering, bird killing, people killing, expensive ass eye sore.

I don't know how many billions of dollars our federal government spends on that grid every year, but anything to minimilize thing would be sweet, even if it takes more energy to produce a solar panel than it ever produced (fairly certain it doesn't.) I still think it would be worth putting solar panels on every roof just to have a single delivery charge, and not a constant drain.

I do think having developments linked is still a good idea, but if the load can be minimized, then the losses, maintaince, EMI emissions will drop to nothing as well. In Tuson now we have self sufficient communities running from solar, and a central connection for load balancing (I assume a central generator/connection to grid is present as well.) So you can supply the surge loads if a AC, and refridge kick on while running the microwave, and TV. That would be covered by your neighbors solar who are out of town/at work, and yours would do the same for them when your out.

Re:transport losses?

[Grayputer]

I think the issue is:

Think in-city clustered 12 story apt buildings. A simple building, 1 apt per floor, say a 1000 sq ft apt. So we have 12 'stacked houses' that have a single 'shared' 1000 sq ft roof. So 1000 sq ft of roof needs to support 12 'houses' of energy. Unlikely. THAT'S why the grid comes in. In clustered/dense city dwelling environments, roof top energy generation will be insufficient to cover the usage. We'll always need a 'grid' in that environment. How we fuel/supply the grid may be debatable but the existance is required due to the space/environmental constraints.

Re:transport losses?

[Anonymous Coward]

Is energy really expensive enough to justify covering your house in solar cells?

Energy as we collect it now, has some non-obvious costs. What does pollution from burning fossil fuels cost us in terms of healthcare? What will sea-level rise cost us? (hint: NYC, LA, DC, Miami, New Orleans, Mobile, and others are very close to sea level, and those are just the US examples.) Would we really have spent $300B and 2,906 American lives (so far) in Iraq if we didn't need to "stabilize" the region that supplies most of our oil? Part of every dollar that you pay in taxes, at the store, at the hospital, in fact pretty much everywhere, is an energy cost.

Wow, nice answer and totally uncalled for. If you really want to see solar displace oil, somebody needs to start selling solar cells that match the cost per watt of oil. There are two ways for that to happen. The first is for the supply of oil to shink (in progress) and drive the price of oil up, and the second is decrease the cost per watt of solar. More efficiency for the same price is a good example as is a decrease in the price of solar.

Everything else cited? It will still be there. Solar is not zero pollution. It just shifts the type and source and spreads it around. Much like coal vs hydro. Do you have any idea what the thermal runnoff is from solar? You want to talk about global warming and healthcare problems? Look no further than the next great energy source. Wars have been fought over far less than potential threats to energy sources. Many more wars will be fought over much less than that as well.

The goal is greater efficiency and sustainability. It is the same reason why farming beats hunting. Right now we are "hunting" energy sources, not "farming" them. That is starting to change, but it needs time (and technology). Just as farming didn't happen overnight, nor will our energy shift. Do what you can to help make it faster, better, or cheaper and it will be here before you know it.

Cost is the issue

[bastiaannaber]

Very nice, but I'd rather see a reduction in cost per watt than an increase in efficiency. It's not like there isn't enough space for for solar cells. Most of the deserts are rather empty. Only if the price per watt drops significantly will we see these things filling up deserts.

Re:Cost is the issue

[Rinikusu]

Erm.. deserts are empty.. of what?

Lots of animals and wildlife flora/fauna live in the deserts. Many of which are endangered. Many of which provide valuable eco-service to the land around them. It might not be prudent to just blot out the sun with solar collectors and think everything's going to be okay.

I'd rather see these on rooftops, supplementing power sources in a more local fashion where their impact will be minimal.

Re:Cost is the issue

[DilbertLand]

Everyone always seems to forget how much energy actually goes into producing a solar cell. It wasn't all that long ago that the electricity needed just to melt the silicon was more energy than the cell would generate throughout it's entire lifetime (they do degrade over time). That doesn't even include all the energy consumed during any additional manufacturing, transportation, and installation.

Re:Cost is the issue

[WindBourne]

So now, you are suggesting that we should put all of America's power generation in exactly one small spot. Yes. Oh yes. I can hear it already:

there is our next target with the new bomb (thank you, george), the Americans make it sooooo easy. .

In addition, as to farmland in the desert, well here is a couple of thoughts:

• There is actually too much unproductive farmland in America. We have a lot of land that is actually very poor, but still in production due to farm subsidies. And desert land is very nutrient poor.
• Here in the West, and more so the SouthWest, we have this issue with water. We are lacking. Plan on sending some our way? We could use it more for our pools and golf courses. And yes, the city folks, esp those from back east, will demand that the water go to them.
• A simple fact is that plants need light. The solar cells use what? Why light. And they all have a back that reflects the unused photons back through the layer so that it might get another chance at being used.

Re:Cost is the issue

[bogjobber]

Looks like someone needs a refresher course in ecology. Deserts are very rich and diverse zones. Remember, a desert isn't just sand dunes. Just because it isn't green and not many people live there (the US West/Southwest) doesn't mean it's a barren wasteland. Also, the reason why the desert isn't farmland is because there is no water. The thing preventing Nevada from being a rich agricultural region is a rather large mountain range, not too much sun. Unless you can find a way of getting more water to the desert (like the Northwest) then it isn't going to produce squat.

Besides, other areas of the country still receive sunshine. I bet when you take into account the costs of maintaining the transmission infrastructure as well as the risks associated with a centralized power source most of the solar stations would be stationed near population centers instead of concentrated in one area.

Re:Cost is the issue

[Big Nothing]

"Very nice, but I'd rather see a reduction in cost per watt than an increase in efficiency. It's not like there isn't enough space for for solar cells. Most of the deserts are rather empty."

I'm sorry, but this should never have been scored insightful. Its obvious at best, troll at worst.

First of all, improved efficiency reduces the investment cost, thus reducing the cost per watt (at least in a proper market economy, which the energy market unfortunately isnt).

Second, COx emissions are not the only environmental threat. In time, studies will more than likely show that covering vast areas of land with shadow-inducing plates (such as solar plants) has a negative impact on local and perhaps regional eco systems. More efficient solar panels mean less land area covered by solar plants, which is a Good Thing ®.

It never seizes to amaze me how people fail to look at the big picture;
* new cars emits less Cox and NOx, but the production of new cars is a significant ecological strain
* biofuel is great in small scale, but greatly reduces the ecological diversity and might pave way for invasive species
* solar plants might provide all the power the world needs one way, but at the cost of placing vast land areas in shadow

Etc.

The harsh reality is that there is no quick fix, there is no gratis lunch.

Re:Cost is the issue

[Eivind]

It was quite some time ago. Today, a solar-cell produces 4-17 times as much energy over its useful lifespan as is spent manufacturing and installing it. That's decent, and the number is climbing steadily. It's time to let that old worn-out argument against solar die.

Re:Cost is the issue

[James McP]

Different scale, purpose, and intent. Not everyone can jam a 70' tower in their yard; there are permits and zoning issues. I can put a couple hundred square feet of cells on my roof with no problems. Today's cells produce about 1kW per 100sf and the area would only decrease.

Plus I can't buy a residential wind turbine for $1/w. For a turbine (installed) in the 1-5kW range it costs about $3/w, with a big chunk of the cost being the tower & installation. $3/w is the same as the solar listed.

I haven't found a turbine for $2/watt until I hit the 20KW level. $40,000 is a lot to recoup and 20kW is a lot of residential power. I'll note that a 20KW turbine is only about about 2% more than 10kW turbine, so wind scales real well once you commit to spending $40,000+.

Which means that individuals will still find solar to be more appealing than wind because a) no tower, b) no moving parts, c) no moving parts located at the top of a 70' tower. Communities will likely find wind to be more appealing because a) it scales well, b) it requires fairly small land area, c) wind is generally more available, especially if you are willing to build a 100' tower.

So stop being a downer on solar, it's really like watching BSD & Linux fanatics going at it. If nothing else, the wind industry should be promoting solar to help get uniform nationwide grid-tie legislation passed.

Downsides

[ChowRiit]

I'm all in favour of clean energy, I think it's a laudable goal, but we shouldn't be patting eachother on our backs just yet.

Firstly, these solar cells are no doubt incredibly expensive - any high efficiency ones are. Secondly, they're probably made using rare and/or exotic materiels, making manufacturing in bulk tricky, and thirdly there's likely to be a lot of pollution created in the manufacturing process for by-products et cetera (it's a problem with less efficient cells too, but the more efficient ones are generally more pollutions).

Lastly, there's another issue. What happens when the sun goes behind a cloud? You need to be able to cover the entire slack in an instant, because you NEED a constant power output. That means you NEED enough GAS powerplants to power the whole world too, as they're the only type of power plant you can literally turn the dial and turn up the output.

Me, I'm going to be sitting here hoping that the test fusion plant they're building in France works, because from what I've learnt lately, if it doesn't, we're screwed.

Re:Downsides

[Atlantis-Rising]

Er, ever heard of batteries? It's perfectly possible to have capacatance stations built into the grid that serve as temporary UPS units for when the power slacks. Similarly, if you spread the generating stations out roughly evenly around the planet and build in enough extra capacity, (maybe 5%, I'm talking out of my ass here) the chances of cloud covering enough of that generator grid to cause a severe power loss are probably negligable.

Presumably, you'd want the capacitance spread out across the grid- not only to prevent brownouts due to lack of power production, but also to temporarily handle spikes in load and to handle temporary grid failures. Neighbourhood or even house-scale capacitance units wouldn't require much storage and could effienctly handle temporary spikes in load, like the use of (for example) a microwave or vacuumn cleaner.

Of course, if you're splitting up capacitance that way, why not split up generation that way too? Just use the power grid as a way to ship excess power around to handle temporary generation losses.

Energy from the sun at maximum potential is what, 1 KW per square meter? My house's roof is probably 15-20 square meters; 12 KW on a sunny day is great. I have absolutely no idea at the moment how much power I'm actually using, on average, (including nights, etc) but I'll bet this won't be enough to cover it. That's okay. Even if it covers half of it...

Still does not solve much

[WindBourne]

The issue is not one of generation. There is actually plenty of energy production (and more is coming on line with new wind and geo-thermal). Our problem is one of energy production when it is needed. Since solar (and most alternatives) will NEVER be able to produce 24x7 or even 8x7, then you need a way to save the energy. As it is, USA feds has been trying to force more research down the path of hydrogen. But the earliest will be around 2025 ,and that depends on having some MAJOR advancements in cost economics that make this solar cell efficiency games look like child's play. IOW, this route will not be happening.

Do not get me wrong. These solar cells are most likely a good thing. Of course, it depends on how the true cost relative to other methods. But this country needs to quit subsidizing oil and coal as well as have a multi-prong research in energy storage to really make the alternatives happen.

Re:Still does not solve much

[magman]

You've got it completely wrong... One of the main benefits of the solar production is that it's distributed and produces during peak hours. In other words, the power is generated when it's needed and you don't have to transport it to the areas where it's being used. Think air conditioning In Japan it's already cost effective to install solar panels without subsidies, in other parts of the world you generally need subsidies to get it working economically. But this business is growing at a rate of 40% each year worldwide, it's only a matter of time!

God, geeks are so incredibly stupid

[Anonymous Coward]

1. Deserts are not empty. They have an ecosystem.

2. There is no reason at all to fill a desert with solar cells, and then transport the energy across to the other side of the planet. Solar cells are installed locally, like on your roof, or in your back yard, on every roof across the planet. Most of the electricity consumed would be as Direct Current right from your rooftop, with an inverter converting for those appliances you still insist on retaining that us AC.

3. For dense city sitatuions with high rises who's energy needs can not be met by rooftops, etc., electricity can be sent via conventional AC lines across the conventional power grid from say no more than 50 miles away. Not the other side of the world.

4. Those who produce an excess of electricity beyond their need, sell it into the grid.

Re:where the facts?

[jannic]

What kind of facts do you expect from an article which contains units like kilowatt/hour, instead of kilowatt x hour? That really looks like the author was only interested in economics, not in scientific facts.

Thermal is slow to start - but you can be prepared

[dbIII]

Actually - that's not true at all. Coal fired plants using pulverized coal can do so

It takes quite a few hours to build up steam from a cold start and it wears everything out quickly by thermal fatigue if you have a lot of restarts. What does happen is something called spinning reserve where coal is being burned and the turbines are spinning but the generators are not connected. The generators can be attached by a very large clutch and more pulverised coal can be fed in to bring things up quickly - I'm too out of touch to know how quickly now and worked in new plants of an old design. With hydro you just turn on the tap and things happen quickly - thermal needs time (which includes oil and nuclear too for people who forget that nuclear is stream power).

Anyway - the troll way above was doing the "one true energy" thing which you only get from idiots or salesfolk. Just becuase photovoltaics are not a drop in replacement for every base load power source on earth does not make them useless. In remote areas they have proven themselves for decades.

PROGRESS WE BE SCREWED!

[brunes69]

Yeah.

And what about all the buggy whip makers!

Who is thinking of THEM!

Re:PROGRESS WE BE SCREWED!

[Silverstrike]

Solar cells will come down in price too, of course, and presumably get more efficient.

Yea, if only they could manage that! We could have a spirited argument on Slashdot article about it!

vandals could easily damage your solar cells

Well, when they're making them more efficent (sometime in the future, obviously), they could also work on making them indestructible as well! Like my windows.

They'd also become less efficient over time and likely just need repair from general aging problems, and in the end you're probably losing more money than by using national power.

Yes! Obviously they'll go bad, because everything has a short lifespan....ya know, like my house's foundation. It's only got 6 months left!

Ok, ok, enough of that. Seriously though. Did you read the SUMMARY? Did it even occur that maybe you should look up the lifespan of a solar panel before MAKING UP statistics? (40+ years, according to a cursory Google Search for "solar panel lifespan"

Please stop, its just painful.

Hello terrorist target

[yetanothertechie]

Good points in parent post. Here's another...

Of course you'd never want to put all of the collectors in one place...a few well placed munitions or a nuke from some rogue regime and there goes our power. Pretty effective way to incapacitate the nation, or throw the world into chaos if the power was being supplied throughout the world. Ever heard of offsite backup? Same principle. The collectors would have to be spread out in case of attack or natural disaster.

Re:Grandpa was a Buggy Whip Salesmen

[anvilmark]

Thank you for so graphically describing how a small % of people can come to own the vast majority of the world's wealth, the subject of another discussion.
Circumstance dealt him a series of "losing" hands, but he didn't bitch and moan and expect someone else to "make it right". He worked, very hard I'm betting, and became wealthy.

Based on what's I've read in that other discussion, he must have been a very wicked and greedy man.

I salute him.