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A long awaited solar power milestone for unconcentrated silicon PV cells has been reached, thanks to steady improvement and research

While many traditional fossil fuel technologies show slow growth in efficiency and design, solar power has instead yielded steady and rapid advances.  While many question why a "killer app" solar product has not yet reached the market after years of hype, it is hard to deny the fact that solar costs both subsidized and unsubsidized have been dropping dramatically, being halved every 10 years. 

With current costs ranging from 15 to 20 cents per kWh, and wholesale coal power costs between 1.5 and 2.5 cents per kWh (and nuclear in a similar range -- 1.7 cents per kWh by estimates from the Nuclear Energy Institute), solar still has a ways to go and likely a few decades before being ready for full deployment.  Still, few technologies show the rapid growth in efficiency solar has and few utilize such a common resource as silicon, so the value of ongoing solar research is apparent.

UNSW's ARC Photovoltaic Centre of Excellence reported a significant milestone this week, with the announcement of the world's first 25 percent efficient unconcentrated solar silicon cells.  They had previously held the 24.7 percent efficient silicon cell record, but were denied the 25 percent milestone due to gaps in the understanding of sunlight and its effect on silicon.

New research has led to revisions in how incident light efficiency is calculated.  As a result, their record-holding design has reached the 25 percent mark, a "magic" number according to many industry experts.  The cell, designed by Professors Martin Green and Stuart Wenham has a wide lead over competitive offerings, according to the Centre.  UNSW holds six solar world records now.

Centre Executive Research Director, Scientia Professor Martin Green described how the new research improved the understanding of the efficiency.  He states, "Since the weights of the colours in sunlight change during the day, solar cells are measured under a standard colour spectrum defined under typical operational meteorological conditions.  Improvements in understanding atmospheric effects upon the colour content of sunlight led to a revision of the standard spectrum in April. The new spectrum has a higher energy content both down the blue end of the spectrum and at the opposite red end with, dare I say it, relatively less green."

While suggesting less green of anything may seem like heresy in the alternative energy industry, it’s good news for the Centre as it means their cells are operating more efficiently than expected.  The Centre's cell posted larger gains than its competitors following the revision.  It is now 6 percent more efficient than the next most efficient competitor, according to Professor Green.

The Centre's cell is approaching the important 29 percent efficiency threshold -- the maximum theoretical efficiency for a first generation silicon photovoltaic solar cell.  Dr Anita Ho-Baillie, who heads the Centre's high efficiency cell research effort, says the new research is a big boost "because our cells push the boundaries of response into the extremities of the spectrum."

She states, "Blue light is absorbed strongly, very close to the cell surface where we go to great pains to make sure it is not wasted. Just the opposite, the red light is only weakly absorbed and we have to use special design features to trap it into the cell."

Professor Green states, "These light-trapping features make our cells act as if they were much thicker than they are. This already has had an important spin-off in allowing us to work with CSG Solar to develop commercial 'thin-film' silicon-on-glass solar cells that are over 100 times thinner than conventional silicon cells."

The biggest goal of UNSW is now to adapt the ultra-high efficiency cells for mass production which should lead to more cost reductions.  ARC Centre Director, Professor Stuart Wenham, adds,"Our main efforts now are focused on getting these efficiency improvements into commercial production.  Production compatible versions of our high efficiency technology are being introduced into production as we speak."

The center has a close relationship with the world's biggest solar manufacturers, thanks in part to Dr Jianhua Zhao and Dr Aihua Wang, who fabricated the record-setting cell and have since left the Centre to establish China Sunergy, one of the world's largest photovoltaic manufacturers.  Professor Green describes, "China was the largest manufacturer of solar cells internationally in 2007 with 70 per cent of the output from companies with our former UNSW students either Chief Executive Officers or Chief Technical Officers."

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RE: 25% = 24.7%
By omnicronx on 10/24/2008 10:53:39 AM , Rating: 3
Yes, it'll persist til then but then there would be no advances in the field of solar or other types of energies.
A solar farm outside of the city I live in which takes about as much space as the closest nuclear facility and is only going to output 110MW (at around 10-15% efficiency) power compared to the nuclear plants 3GW (which is considered a small plant). Now even if these solar cells had 100% efficiency, it would still not produce half the electricity that a 20 year old nuclear plant can.

I really just don't understand what all the fuss with solar is about, its never going to totally replace other forms of power. Nuclear is safe, and any spent radioactive materials really do not compare to the disposal of old solar panels, which is bound to happen on a mass scale, and nobody ever talks about.

RE: 25% = 24.7%
By menace on 10/24/2008 6:14:25 PM , Rating: 2
I agree with your assessment though take exception at calling 3GW a "small plant".

The largest reactor in the US is Palo Verde 2 at 1.335 GW
The whole site has three reactor units and generates 3.2 GW on average. I think you would have to say that is a "large plant".

I never thought much about how to dispose of old cells. I might think there would be recycling potential. If nothing else crush it up and use it as concrete aggregate.

RE: 25% = 24.7%
By TA152H on 10/24/2008 10:29:38 PM , Rating: 1
Never say never. Solar power could replace all other forms in the future, who knows?

There are already a number of ways it is better than nuclear. And one big way it is not. It's less efficient/most expensive. On both accounts that's changing.

But, your big fallacy about waste is this. I don't mind sleeping with solar cells on my house, or even solar waste in my garbage can. You feel the same way about nuclear waste? It's not the volume, it's the problems with the waste that is a problem. I think finding a use for silicon shouldn't be too difficult. In worst case, you bury it and it causes no harm. Spent nuclear fuel? Not so easy.

Plus, nukes are relatively safe, but even so, they are not as safe as solar power. Chernobyl? Three Mile Island? Being unlikely and impossible are two different things. People are always going to be a little afraid of nukes because the potential danger is very great, if also very unlikely. There have already been disasters, and consequences.

Also, at least for the near future, you can't put a small nuke in your house and address your electricity bill. It's just not a choice an individual has. You can add solar panels, or windmills, or even geothermal power in many instances. So, solar does have a place. I won't predict the future, it's a fools errand, and say how much it will be, but it clearly has advantages and research is clearly justifiable, especially with the costs coming down so quickly, and efficiency still moving up.

I know this sounds horrible, but I hope the oil prices go up some, so we'll stop being oil pigs and invest in more nukes, and alternatives. For the short term, nukes are really the only answer to increase power, and increase it quickly. Solar can't ramp quickly enough, and neither can air or hydroelectric, or any of the other completely safe types. But long term, things that make the Earth safer, rather than more dangerous, can hopefully be our future, or a greater part of it.

RE: 25% = 24.7%
By teldar on 10/26/2008 9:36:43 PM , Rating: 2
See the only problem with that, is how is nuclear going to drive your car. Everyone wants to lump energy together. We use oil to drive and coal/sun/nuclear to power our houses.

For that basic dichotomy to change, we're going to need ultracapacitors or much much better batteries. Oil should be cheap and we need oil algae.


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