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back to article Boffins tout solar efficiency boost

A joint project between Sydney University and Germany’s Helmholtz Centre for Materials and Energy claims to offer a low-cost boost to solar cell efficiency. The efficiency question for solar cell developers is how to capture more energy from more photons, since “wasted” photons merely get turned into heat. That’s harder than it …

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Flame

Longevity?

And how long will those organic dye molecules survive the daily assault by the (admittedly low-energy) photons?

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Joke

Triplet-triplet annihilation

Can we really justify killing so many unwitting look-alikes just for a marginal gain in solar cell efficiency? And, do they have to run at each other really fast for the effect to work?

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Anonymous Coward

Boffins devise red sun sunscreen for Superman.

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do the two photons have to hit the dye at the same time or does the first hit increase the energy state of the dye and the dye holds it until the second hit?

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Joke

Time betweem photons

I doubt there is much of a gap between the arrival of photons. Unless it's the middle of a British summer...

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Nev

Check the Graph in the Abstract...

It seems to suggest an increases in efficiency of upto 2%.

Given the already appalling efficiency of such PV devices, that's not really much of an improvement.

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Re: Check the Graph in the Abstract...

"It seems to suggest an increases in efficiency of upto 2%."

Those appear to be the measured efficiency increase in a real cell - and that figure is also mentioned at the end of the article - the higher figure is referring to the theoretical peak efficiency. The group seem to be aware of the gap between the two, and know more work is needed, e.g. from the article..

Professor Schmidt said.

"We now have a benchmark for the performance of an upconverting solar cell. We need to improve this several times, but the pathway is now clear."

"Given the already appalling efficiency of such PV devices, that's not really much of an improvement."

I personally wouldn't say that a 20+ % total conversion rate is appalling, especially given the lack of required effort in creating the incoming flux - and the intial result from a cell giving a 10% relative boost is hardly to be sneezed at. PV devices are already more than efficient enough to be used for power production economically - the economics and logistics of storage are more of an issue.

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Correction - Re: Check the Graph in the Abstract...

Apologies

"and the intial result from a cell giving a 10% relative boost"

is wrong, the 2% was already a relative measure. So much smaller initial increase in that device.

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FAIL

So....

.......a theoretical boost, eh? I can't wait!

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Re: So....

"a theoretical boost, eh? I can't wait!"

The abstract seems to imply that the 1% efficiency increase is in a real device, and the data in the graph looks to be more experimental than theoretical. From the abstract

"We report an increase in light harvesting efficiency of a hydrogenated amorphous silicon (a-Si:H) thin-film solar cell due to a rear upconvertor based on sensitized triplet–triplet-annihilation in organic molecules. .... A peak efficiency enhancement of (1.0 ± 0.2)% at 720 nm is measured under irradiation equivalent to (48 ± 3) suns (AM1.5)."

Without access to the full paper it is not possible to prove this is real data however, perhaps someone who can get hold of it could clarify.

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Meh

Great News

Another 20 or 30 discoveries like this, plus a reduction in manufacturing costs and solar power might be suitable for actual real use...

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Happy

Re: Great News

Solar power already IS "suitable for actual real use"... in countries that actually get sunlight like Spain. Boosting efficiency by 2-5% is all very well, the real breakthrough needs to be in halving the cost of a simple panel with no more than 20% efficiency, then you could just build city-sized arrays in the North African desert and connect them to the European grid.

Now if the UK could work out a way to harness all that kinetic energy from falling rain, we'd be onto a winner!

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Re: Great News

"you could just build city-sized arrays in the North African "

It would be great if Africa could export electricity to the rest of the world, but many more things must happen before this can be realistically planned. One thing is loses when sending power over large distances; there is also sad issue of political instability in large regions of Africa which would threaten such installation. I'm sure there is more.

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@Bronek Kozicki

"loses when sending power over large distances"

This can be remedied by using the electricity locally (for sufficiently tolerant values of 'locally') to create hydrogen, and from there hydrocarbons, for which the infrastructure for storing and transporting is already in place.

The other point you bring up does not have a simple solution. In fact, it may even be exacerbated.

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Go

Re: Great News

@Bronek. Re: losses.

"connecting to continental Europe via special high voltage, direct current transmission cables, which lose only around 3% of the electricity they carry per 1,000km."

From:- "Could the desert sun power the world?"

http://www.guardian.co.uk/environment/2011/dec/11/sahara-solar-panels-green-electricity

As for the dodgy political situation, can you remind me where developed countries get a lot of their oil from? Maybe North African desert solar installations wouldn't be any worse than Middle Eastern oil?

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Anonymous Coward

Re: UK could work out a way to harness all that kinetic energy from falling rain

watermill?

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Happy

Re: UK could work out a way to harness all that kinetic energy from falling rain

Indeed, hydro-electrics, but most of the electricity is needed in the flat, dry bits of the country

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Re: Great News

"connecting to continental Europe via special high voltage, direct current transmission cables, which lose only around 3% of the electricity they carry per 1,000km."

I'm guessing from that comment that there has been some significant advance in electrickery distibution since Edison lost the AC/DC war because it was uneconomic to build DC power stations which could barely manage to distribute within a square mile.

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Re: Great News

@John, you guess correctly!

http://en.wikipedia.org/wiki/High-voltage_direct_current

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Re: Great News

Edison's problem was not that DC is inefficient but that given the absence of DC transformers he had no way to distribute it at high voltage.

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Anonymous Coward

"Another 20 or 30 discoveries like this, plus a reduction in manufacturing costs and solar power might be suitable for actual real use..."

Solar has it's uses but providing reliable 'grid' power is not really one of them unless you hook it up to a storage system (thereby increasing it's costs even further).

It does not really matter if you make it 20% more efficient in somewhere like the UK as we just don't get as much sun and unless you don't want to use your lights when it gets dark....

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Ru

Bear in mind that

At the times when solar flux is plentiful, there's demand for aircon precisely during the times at which solar cells are most effective. This applies to gloomier latitudes as much as it applies to the Sahara.

I'll bet that daytime grid load exceeds nighttime, too, so solar is available at the point at which it is most useful... pretty stark comparison to wind power there.

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"One thing is loses when sending power over large distances"

It's about 2000km as the crow flies between north Africa and London.

Wikipedia says:

"Depending on voltage level and construction details, [HVDC] losses are quoted as about 3% per 1,000 km"

"The longest HVDC link in the world is currently the Xiangjiaba-Shanghai 2,071 km (1,287 mi) 6400 MW link connecting the Xiangjiaba Dam to Shanghai, in the People's Republic of China.[2] In 2012, the longest HVDC link will be the Rio Madeira link connecting the Amazonas to the São Paulo area where the length of the DC line is over 2,500 km (1,600 mi).[3]"

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Ru

Re: "One thing is loses when sending power over large distances"

Trickier to build HVDC links across the Med than it is to build them overland.

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"As the crow flies"

From Africa to England? Everyone knows it's swallows that do that, so maybe we should be looking into how many electrons can be stuffed into a coconut.

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Anonymous Coward

Re: "One thing is loses when sending power over large distances"

Use the shortcut at the Strait of Gibraltar.

And for a laff, bring it ashore at Gibraltar itself just to annoy the Spanish.

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Joke

Re: "As the crow flies"

Is that an African or European swallow?

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Megaphone

Re: "One thing is loses when sending power over large distances"

"bring it ashore at Gibraltar itself just to annoy the Spanish."

Good! then you can send the leccy to the rest of Europe with a fleet of pigeons carrying rechargeable batteries. * :-D

*: ¡Gibraltar español!"

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Headmaster

Re: "As the crow flies"

Laden or un-laden?

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Boffin

@Ru

"Trickier to build HVDC links across the Med than it is to build them overland."

7.7 nautical miles. Way less than the 300 nmi that the NorNed link spans. And Tunisia-Sicily is still below 100nmi.

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Boffin

Laden or un-laden?

That coconut's full of electrons. How can you suggest it's un-laden?

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Re: Laden or un-laden?

So before loading they are unladen, after loading they are laden.

Does that mean after being emptied they would be bin-laden?

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Sauce for the goose...*

*: ¡Ceuta maroc!"

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Wouldn't bet against the Helmholtz guys.....

Very bright peeps indeed, saw them a couple of weeks back. And they're getting a tonne of govt money too.

Although this article does explain one thing that hugely confused me: why several of them speak English with an Oz accent.....

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Happy

Err, limiting factor.

I seem to recall the average Solar Cell 100% theory limit is roundabout 1000W/m2 for this planet? A lot of area and investment would be required - or maybe Tesla knew better?

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Re: Err, limiting factor.

It all depends on where you are. 1000W/m^2 is regarded as Standard Test Conditions, and is what the specified output of the solar cells will be reached under, but there have been a few occasions this month where my own installation has exceeded STC output, and that's in Scotland... Certainly if you were to use the same panels on the Isle of Wight, they'd produce significantly more given the same cloud coverage.

I've been trying to find a solar insolation map to tag onto this, but they all deal with average kWh/year, which I suppose makes sense. Ho-hum.

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Even if PV's were 100% efficient

They would still be bloody useless.

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Pint

Re: Even if PV's were 100% efficient

@itzman - I wonder if yer post has bounced off a satellite with solar panels on the way to my screen? I must admit I'd like to call solar panels bloody useless as well but they do actually seem to do something? Beep

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If I understand this...

But isn't this essentially a fluorescent solar cell? If I recall correctly, fluorescent bulbs (including the CFL) bulbs use a fluorescent coating to absorb x number of IR photons and release Y number of viable light photons.

Is the break through then that they are using organic dyes instead of mercury-based shenanigans? If so, I can't wait for a CFL that doesn't require a hazmat suit to clean-up after a break.

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Anonymous Coward

Or my personal favourite

MEMS micro-aligners over each cell.

They tune with applied voltage and track the Sun so the entire panel doesen't need to move, but because they focus light onto the tiny quad junction cells underneath less active material is needed.

Also it occurs to me that downconverting UV to visible would also help, perhaps combine all three and make a 70% efficient panel.

Use liquid metal to cool the cell(s) and a vacuum thermoelectric to generate power from the wasted heat.

AC/DC 6EQUJ5

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