Solar cell efficiency could double with novel 'green' antenna

August 18, 2015
solar cell

The use of solar energy in the U.S. is growing, but panels on rooftops are still a rare sight. They cost thousands of dollars, and homeowners don't recoup costs for years even in the sunniest or best-subsidized locales. But scientists may have a solution. They report today the development of a unique, "green" antenna that could potentially double the efficiencies of certain kinds of solar cells and make them more affordable.

The researchers are presenting their work at the 250th National Meeting & Exposition of the American Chemical Society (ACS).

"Most of the light from the sun is emitted over a very broad window of wavelengths," says Challa V. Kumar, Ph.D. "If you want to use to produce electric current, you want to harvest as much of that spectrum as possible."

But the silicon solar cells people buy today are not very efficient in the blue part of the light spectrum. So Kumar's team at the University of Connecticut built an antenna that collects those unused blue photons and then converts them to lower energy photons that the silicon can then turn into current.

"Many groups around the world are working hard to make this kind of antenna, and ours is the first of its kind in the whole world," he says.

Commercial solar cells do a good job of converting light from about 600 to 1,000 nanometers (nm) into electric current but not from the 350 to 600 nm range. That's part of the reason solar cells on the market today are only about 11 to 15 percent efficient. High-end panels can reach 25 percent but are unaffordable for most customers. Lab prototypes can reach even higher efficiencies but are difficult to scale up.

Converting the mostly unused portion of the light spectrum to wavelengths solar cells can use in an affordable way is far from a simple task. To tackle this problem, Kumar turned to organic dyes. Photons in light excite dye molecules, which can then, under the right circumstances, relax and emit less energetic but more silicon-friendly photons.

But to get dye molecules to work together, they need to be wrapped individually and densely, while satisfying certain quantum mechanical requirements. To address this issue, they embed the dyes inside a protein-lipid hydrogel by mixing them together, warming them up and then cooling them to room temperature. With this simple process, the material wraps around individual , keeping them separated while packing them densely. Rather than creating a radio-like antenna, however, the procedure results in a thin, pinkish film that can be coated on top of a solar cell.

"It's very simple chemistry," Kumar says. "It can be done in the kitchen or in a remote village. That makes it inexpensive to produce."

These antennas are made with biological and non-toxic materials that are edible in theory, Kumar says. "Not that you would want to eat your solar cells, but they should be compostable so they won't accumulate in the environment," he says.

Now his team is working with a Connecticut company to figure out how to apply the artificial to commercial . In other projects, they also are figuring out ways to use the versatile hydrogel for drug delivery and white light-emitting diodes.

Explore further: Reshaping the solar spectrum to turn light to electricity

More information: Edible or digestible artificial light antennas: Hydrogels of dye-loaded bovine serum albumin and medium chain fatty acids, the 250th National Meeting & Exposition of the American Chemical Society (ACS).

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Eikka
3 / 5 (6) Aug 18, 2015
Too bad the current solar energy subsidy models don't allow inventions like these to enter the market.

Subsidizing the purchase and output of solar panels rather than the R&D and commercialization of technology means that the buyers put their money on the solar panels that offer the biggest return - least money spent per subsidies paid. That means they keep buying the older types of panels that are being pushed out onto the market in huge quantities on the cheap by the Chinese factories.

The newcomers have an uphill battle because they start off more expensive than the competition, and so nobody buys the panels, and so they never get the money to expand and become cheaper.

That's why very little of the subsidy money ends up with people and companies who are actually pushing the technology forward towards affordability and practicality. They need to sink a whole lot of capital to get in on the game, but nobody's paying.

Eikka
2.5 / 5 (6) Aug 18, 2015
It's ridiculous that our politicians are spending tens of billions of dollars a year subsidizing solar energy, in the US and in Europe, when the same money could be spent in kickstarting better technology that could be cheap enough to be competitive on its own merits - which has to happen anyways or we're just screwed.

The current solar subsidies are not sustainable - we can't afford a whole power system that costs hundreds of dollars per MWh - and without the subsidies the current solar power generation is not feasible, so it's completely pointless to keep pumping money that way.

The sooner it stops the faster we can get to the real business of making clean energy in an affordable, sustainable way.
Eikka
1.4 / 5 (5) Aug 18, 2015
There's also another argument in favor of subsidizing the technology directly instead of the buyers:

We get to choose which companies we give the money to. That means we can choose to support domestic production of solar panels instead of giving all the money to the Chinese, which means creating jobs, which means lower social costs and that covers part of the high cost of the technology.
EyeNStein
3.5 / 5 (2) Aug 18, 2015
I would be surprised if their bio degradable organic dyes survive in hot, brightly lit, UV rich environments.
An inorganic phosphor (As normally used in their above mentioned white LED's) to convert blue/violet to 600nm orange might better survive the lifetime of a silicon panel.
denglish
1.5 / 5 (2) Aug 18, 2015
Its good to see that we're getting better at this alternative energy.
RM07
2.5 / 5 (4) Aug 18, 2015
Eikka, whether you realize it or not, there are dozens of unintended consequences of having public bureaucrats pick winners and losers in the private sector.

Who's smart enough to pick the winners? We just need better central planning? Smarter people? How about hire the whole Harvard faculty to benevolently run the country and do what's best for us?

Don't you think corporations would "buy" politicians through political donations, which now might influence "industry-wide subsidies", but in your system would result in *direct* cash returns?

It would create what's known as Crony Capitalism.

And despite the dangers, we're already trying it, by "loaning" money for causes the ruling power supports, which is why Solyndra's spectacular failure was in the news a few years ago.

The free market sorts these things out by itself, more efficiently than any central planner ever could. Solar is nearly on par pricewise with conventional fossil fuels, and is only getting cheaper.
Tessellatedtessellations
3.7 / 5 (6) Aug 18, 2015
RM07 The Great and Mighty Invisible Hand of the Free Market gives handjobs to the very wealthy and chokes the daylights out of the common man. If The Hand is so great, why are 99% of people economically worse off than people were prior to the 1980's?

Death to The Hand!
greenonions
5 / 5 (5) Aug 18, 2015
Solar panels are a hot commodity globally - http://cleantechn...15-2016/

Production prices are down to about 40 cents U.S. per watt, and falling. Gigawatts of capacity are going up all around the world - http://cleantechn...15-2018/

If this development actually holds up in the real world (lots of testing before that happens) - then - 20 cents a watt - and it is game over for any other energy source.
EyeNStein
3 / 5 (2) Aug 19, 2015
But at 20c a watt could you still trust the resulting PV panels on your roof?
They have to retain high quality of materials, construction and testing; to withstand hot/cold cycling and still remain moisture proof for the 20 years it takes to pay back for their installation.
The $50 panel may be a great disposable commodity price but it costs more than that to keep replacing them every few years.
RM07
1.5 / 5 (4) Aug 19, 2015
Tessellatedtessellations, their is no system in the history of the world fairer than the free market. Everyone has an equal opportunity, and that possibility of being rewarded for hard work and risk is what drives people to innovate, create new markets, and thus create jobs. Feel free to embrace your socialistic class warfare and spend the rest of your life angry and jealous, but you'll not be inventing a better system.

Greece, Ireland, Italy, Portugal, and Spain are leading the fall after 50-100 years of socialism. As Margaret Thatcher once said, "the problem with Socialism, is that eventually you run out of other people's money to spend." Keep at it. You'll get it.
EyeNStein
5 / 5 (3) Aug 19, 2015
The free market is not so good either.
To plagiarise Thatcher: "The problem with capitalism is it eventually runs out of other peoples lives to spend."
Our goods are so cheap because they are made by people who don't have the rights, income nor healthcare that we take for granted.
We may have abolished slavery but it has been re-born as a sanitised import/export process in the "free market".
Free for whom?
Eikka
4 / 5 (1) Aug 19, 2015
Eikka, whether you realize it or not, there are dozens of unintended consequences of having public bureaucrats pick winners and losers in the private sector.


I am aware. The obvious solution is to spread the subsidy evenly across the field, to universities and independent research facilities doing energy research. Beyod that, you simply have to take some risks and admit that some of the companies will fail.

You can't make an omelette without breaking some eggs. The problem is that people latch on to the failures and refuse to see the big picture. Solyndra for example failed because of cheap Chinese state subsidized solar panels flooding the market for the express purpose of killing European and US competition.

Who's smart enough to pick the winners?


Same can be asked of the private investors in any line of business. Why are they smart enough to handle money?

Or are they rather just lucky?
Eikka
4 / 5 (1) Aug 19, 2015
It would create what's known as Crony Capitalism.


It already is crony capitalism. The ample subsidies mostly benefit the rich big business owners who can afford billion-dollar solar/wind farm projects and use them to avoid taxes. Look at what Warren Buffet is doing for an example:

The CEO of Berkshire Hathaway Energy, Greg Abel, said that the company has been able to put so much money into renewable energy because it can use tax credits to offset profit at other businesses.

http://www.justme...-billion

It takes little to guess who really keeps lobbying for more and more subsidies.

This is a problem because these old-tech projects cost the taxpayer an incredible amount of money for the energy they produce, and there's absolutely no incentive to use better technologies because it's all about short term profit.
Eikka
4 / 5 (1) Aug 19, 2015
Another point in case:

http://www.bloomb...n-energy

Warren Buffett's company invests in solar power to write off taxes and collect government subsidies, while lobbying to stop people from installing their own rooftop panels to make himself more room in the market.

If that's not crony capitalism, I don't know what is.
Eikka
3 / 5 (1) Aug 19, 2015
The free market sorts these things out by itself, more efficiently than any central planner ever could.


The problem is that it isn't a free market with our current energy subsidies. If you want to make the free market argument, you should support removing the subsidy structures anyhow.

Eikka
2 / 5 (1) Aug 19, 2015
If this development actually holds up in the real world (lots of testing before that happens) - then - 20 cents a watt - and it is game over for any other energy source.


Again you ignore that the raw production cost of has very little do with how much solar energy costs, because more than half the cost is due to installation and maintenance, and other supporting infrastructure which will have to include storage as well.

The decreases in production costs are making diminishing returns. Diminishing returns means that no matter how cheap the panels themselves become, the real cost of operation will not become arbitrarily low. If the panel cost is about half of the total price now, then no matter how cheap they get, the real cost can't drop by more than 50% and that's still too expensive.

That's why it's essential that the technology itself is made better: more efficient, longer life, easier deployment, less maintenance - because that affects the whole cost of deployment.
Eikka
1 / 5 (1) Aug 19, 2015
Production prices are down to about 40 cents U.S. per watt, and falling.


http://3.bp.blogspot.com/-UBQ8IKe_H2s/Uqfr825dh-I/AAAAAAABBTs/F4IE3a9E--o/s1600/12-11-2013a.png

It takes $2-3 per Watt to get the panel from the factory through the supply chain and onto your roof, installed, wired up and operational with taxes and fees paid, so whether the panel costs 20 or 40 cents is almost irrelevant.

Then you have to take into account the cost of the load following power generation capacity that has to keep online to accomodate the solar power in the grid.

Summa summarum: cheap solar power is not actually cheap.
Da Schneib
5 / 5 (2) Aug 19, 2015
...which is why Solyndra's spectacular failure was in the news a few years ago.
Actually, Solyndra failed for two reasons:

1. They were unable to get production costs down fast enough: "In Solyndra's quarterly employee meetings, employees were told that the company was losing money, and that production costs, while declining, were still higher than the also-declining market prices for solar panels." https://en.wikipe...tigation

2. The Chinese "dumped" solar panels onto the market at below-production-cost prices to capture the market: "The Department of Commerce slapped high tariffs on solar products from China and Taiwan yesterday in a decision intended to address dumping and unfair subsidization of imports to the United States." http://www.greent...-tariffs
jeremy_h
2 / 5 (1) Aug 19, 2015
If the panel cost is about half of the total price now, then no matter how cheap they get


Actually, it's even worse than that. The cheaper you can get is in California and they average 4.61 $/kW for installation over 10 kW (and 5.32 $/kW under 10 kW).
https://www.calif...s.ca.gov

At 55 cents/kW, your balance of systems is 88% of the cost, so essentially even if you gave them for free, it's unlikely to reach grid parity in non-sunny countries without subsidies.
Sure, inverters can decrease in cost from economy of scales but humans and land acquisition don't follow a learning curve.

- 20 cents a watt -

Silicon solar panels use on average 7.5 g/W of poly-Si and at the current price of 15 $/kg, you need 11.25 cents of base material, that's 56% of the price you ask. Basically at 20 cents/W, you have don't even have a complete cell, look at cell price per watt, it's 30.8 cents/W.
http://pvinsights.com
greenonions
5 / 5 (3) Aug 19, 2015
Eikka - I only have a second right now - but you put a 3 year old graphic up - to discuss the price of solar - in a world in which prices are falling rapidly http://cleantechn...-report/

Come on - get serious. And - as you say - soft costs are still at least 50% of the cost of installation - which means there is a lot of room there to reduce costs as well.
greenonions
5 / 5 (3) Aug 19, 2015
jeremy -
Basically at 20 cents/W, you have don't even have a complete cell, look at cell price per watt, it's 30.8 cents/W.


But this article is talking about a technology that will double the efficiency of panels. So panels are heading down in price already, and with the addition of this technology - it would seem very reasonable to think that we may hit 20 cents a watt in the near future. The fact that the cost of the panel is such a small part of the overall cost - is a really good thing. It means there is a lot of room for cost reduction in the soft costs. Many are working on this issue as we speak. http://cleantechn...s-heres/
jeremy_h
2 / 5 (1) Aug 19, 2015
Hi greenonions,
it would seem very reasonable to think that we may hit 20 cents a watt in the near future

I wouldn't be so optimistic when looking at this tech, it still uses poly-Si, which is an incompressible cost and is at its cheapest.
So at today's spot price, you have 56% just in material cost, so if you want 20 cents/W for the module, you need to squeeze manufacturing costs for the cell and manufacturing cost for the module in the remaining 44%, that's only 8.8 cents for all steps.
Right now, if you look at the site linked above, you see the module's cost being 24 cents/W and the cell's cost at 19.5 cents/W.
To fit them in the 44%, they must drop to 4.85 cents/W and 3.96 cents/W respectively, that's around 5 times less than what they are. This is strongly unlikely that someone finds a way to divide by 5 the cost of manufacturing of all the elements in a few years.
greenonions
5 / 5 (3) Aug 19, 2015
I wouldn't be so optimistic when looking at this tech,


I am sure you would not. Let's wait and see shall we? If this technology pans out - it will halve the cost of panels (plus what ever cost it adds - as it is an additional process). So let's wait and see shall we? There are always armchair engineers - willing to write some numbers on a napkin - and claim that this or that cannot be done. The doers are out there doing it - which is why we have brought the cost of panels down by 50% in the last 5 years. http://costofsola...5-years/

Your assertion that the cost of silicon is incompressible is flawed. If we can increase the efficiency of panels - we effectively use less material - hence reducing the cost of the silicon. Just one example of many coming - http://www.photon...ID=56835
Da Schneib
5 / 5 (3) Aug 19, 2015
Every little bit helps. I doubt at this late date there's going to be any single really game changing discovery in solar; but the little improvements add up. Japan proved that by nearly killing the US auto industry in the 1970s. I'd say there're a lot of people who've forgotten that, and those who forget history are generally doomed to repeat it, in this case that means getting made to look stupid again.

Why dis it? What have you done lately to improve the situation is a question every naysayer should be answering for themselves; of course, they're naysayers precisely because they ignore that.
Da Schneib
5 / 5 (3) Aug 19, 2015
...it still uses poly-Si, which is an incompressible cost and is at its cheapest.
In fact, this tech doesn't use polysilicon at all. It's universally applicable to all frequency-limited solar cells. Silicon solar cells aren't the only ones that are frequency limited.

Another naysayer myth destroyed.
Zzzzzzzz
3 / 5 (4) Aug 21, 2015
Factor in the true and complete cost of power from fossil sources and solar will blow it away. That is what a real market would do.

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