Scientists make breakthrough solar technology

Oct 21, 2013
Prof Subodh Mhaisalkar (left) and Dr Nripan Mathews (right) are holding the new Perosvkite solar cells made in NTU labs and hopes to develop into a solar cell module, as held by Prof Sum Tze Chien (centre).

In the near future, solar panels will not only be more efficient but also a lot cheaper and affordable for everyone, thanks to research by Nanyang Technological University (NTU) scientists.

This next generation solar cell, made from organic-inorganic hybrid perovskite materials, is about five times cheaper than current thin-film solar cells, due to a simpler solution-based manufacturing process.

Perovskite is known to be a remarkable solar cell material as it can convert up to 15 per cent of sunlight to electricity, close to the efficiency of the current solar cells, but scientists did not know why or how, until now.

In a paper published last Friday (18 Oct) in the world's most prestigious academic journal, Science, NTU's interdisciplinary research team was the first in the world to explain this phenomenon.

The team of eight researchers led by Assistant Professor Sum Tze Chien and Dr Nripan Mathews had worked closely with NTU Visiting Professor Michael Grätzel, who currently holds the record for perovskite solar cell efficiency of 15 per cent, and is a co-author of the paper. Prof Grätzel, who is based at the Swiss Federal Institute of Technology in Lausanne (EPFL), has won multiple awards for his invention of dye-sensitised solar cells.

The high sunlight-to-electricity efficiency of perovskite solar cells places it in direct competition with thin film solar cells which are already in the market and have efficiencies close to 20 per cent.

The new knowledge on how these solar cells work is now being applied by the Energy Research Institute @ NTU (ERI@N), which is developing a commercial prototype of the perovskite solar cell in collaboration with Australian clean-tech firm Dyesol Limited (ASX: DYE).

Asst Prof Sum said the discovery of why perovskite worked so well as a was made possible only through the use of cutting-edge equipment and in close collaboration with NTU engineers.

"In our work, we utilise ultrafast lasers to study the perovskite materials. We tracked how fast these materials react to light in quadrillionths of a second (roughly 100 billion times faster than a camera flash)," said the Singaporean photophysics expert from NTU's School of Physical and Mathematical Sciences.

"We discovered that in these perovskite materials, the electrons generated in the material by sunlight can travel quite far. This will allow us to make thicker solar cells which absorb more light and in turn generate more electricity."

The NTU physicist added that this unique characteristic of perovskite is quite remarkable since it is made from a simple solution method that normally produces low quality materials.

His collaborator, Dr Nripan Mathews, a senior scientist at ERI@N, said that their discovery is a great example of how investment in fundamental research and an interdisciplinary effort, can lead to advances in knowledge and breakthroughs in applied science.

"Now that we know exactly how perovskite materials behave and work, we will be able to tweak the performance of the new solar cells and improve its efficiency, hopefully reaching or even exceeding the performance of today's thin-film solar cells," said Dr Mathews, who is also the Singapore R&D Director of the Singapore-Berkeley Research Initiative for Sustainable Energy (SinBeRISE) NRF CREATE programme.

"The excellent properties of these materials, allow us to make light weight, flexible solar cells on plastic using cheap processes without sacrificing the good sunlight conversion efficiency."

Professor Subodh Mhaisalkar, the Executive Director of ERI@N said they are now looking into building prototype solar cell modules based on this exciting class of materials.

"Perovskite-based have the potential to reach 20 per cent solar cell efficiencies and another great benefit of these is their amenability to yield different translucent colours, such as red, yellow or brown. Having such colourful solar glass will create new opportunities for architectural design," he added.

Explore further: Team of physicists find perovskite can be used in conventional solar cell architecture

More information: Long-Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic CH3NH3PbI3, Science 18 October 2013: vol. 342 no. 6156 344-347.

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Aaron1980
1.7 / 5 (16) Oct 21, 2013
the day when cars recharge themselves parked in the sunshine should not be far away.
sirchick
4.4 / 5 (7) Oct 21, 2013
Non stop breakthroughs in solar power, but still not seeing them marketed much at all for people to go green...to put them on my house roof still isn't cheap enough to be worth the time and effort.
Eikka
1.7 / 5 (11) Oct 21, 2013
their discovery is a great example of how investment in fundamental research and an interdisciplinary effort, can lead to advances in knowledge and breakthroughs in applied science.


Meanwhile the political consensus especially in Europe seems to be that we should rather invest in subsidies for companies and individuals who install and use solar panels, under some sort of scientific trickle-down theory where, if you buy lots of previous generation panels at barely sustainable prices from China, the money will - instead of being mopped up by business magnates - somehow trickle down to the outcompeted companies and academies that are actually trying to advance the field instead of just make money out of it.
antialias_physorg
3.6 / 5 (8) Oct 21, 2013
the day when cars recharge themselves parked in the sunshine should not be far away.

Do the math:
Solar constant times surface area of a car plastered in solar cells times time parked in full sunlight times efficiency of solar cell (times efficiency of putting that energy into storage and conversion back to useful motion)

Plug in the numbers and see how that isn't nearly enough to get you anywhere.
TheGhostofOtto1923
2 / 5 (6) Oct 21, 2013
Plug in the numbers and see how that isn't nearly enough to get you anywhere
Well you have to take into consideration exploiting ALL the solar energy that falls on a car.

"The new [thermoelectric] material, which is based on the common semiconductor telluride, is environmentally stable and is expected to convert from 15 to 20 percent of waste heat to electricity."

"(PhysOrg.com) -- A prototype of a new type of photovoltaic (PV) cell that generates electricity from visible, infrared and ultraviolet light has been demonstrated by a group of Japanese scientists. It could lead to the development of a highly-efficient PV cell in the future, without needing multijunction cells"
Eikka
1.8 / 5 (10) Oct 22, 2013
Do the math


Assuming your car's roof and hood area combine to 5 square meters, and your incoming solar flux is 1000 W/sq-m and the efficiency of your solar panels is 15% your peak power should be somewhere in the neighborhood of 750 Watts. One hour in the sun will therefore get you approximately 3 kilometers down the road.

In other words, if you park your car outside in the summer, by the end of the afternoon you can do your groceries trip on solar power.

Over the year, you can generate about 1/10th of your peak power, which means you'll generate 2628 kilometers for free, or double that if you live close to the equator.
antialias_physorg
2.3 / 5 (3) Oct 22, 2013
Assuming your car's roof and hood area combine to 5 square meters, and your incoming solar flux is 1000 W/sq-m and the efficiency of your solar panels is 15% your peak power should be somewhere in the neighborhood of 750 Watts. One hour in the sun will therefore get you approximately 3 kilometers down the road.

Those are some unrealistic assumptions. When I googled for the dimensions of a limousine (BMW M3) I came out to about 3 square meters of usable car surface (total surface is irrelevanrt: it's the amount of surface perpendicular to the sun that counts - otherwise you get have to use a variable solar constant as the 800W/square meter (It's not 1000 for most of Europe, Asia or the US) is only reached at midday, summer, totally cloudless, no shadows whatsoever)
antialias_physorg
2.3 / 5 (3) Oct 22, 2013
Over the year, you can generate about 1/10th of your peak power, which means you'll generate 2628 kilometers for free, or double that if you live close to the equator.

Which would be a nice bonus (and I'm all for adding PV to cars) - but 2.6k km is about 1/10th of the use an average person gets out of a car per year.

Currently the PV on some cars is barely enough to run the AC (which is OK, but gives you an indication of whether solely PV driven cars will be in our future - the answer is a simple: No way).
antialias_physorg
2.3 / 5 (3) Oct 22, 2013
This isn't knocking what the guys in the solar challenge do, mind. Those are some great vehicles they're building (and the 'cruiser class' category is just starting to fly.) But unless we reduce some legal hassels for road vehicles (and unless people generally shed some weight) that's not going to be enough.
triplehelix
1.6 / 5 (13) Oct 22, 2013
"In the near future, solar panels will not only be more efficient but also a lot cheaper and affordable for everyone"

I heard this back in the 90's. They're still grossly overpriced and have absolutely terrible capacities and drain faster than a bucket with holes in it.

I have also read that statement, in literally dozens of articles throughout the past 2 decades.

Little hint for those not in scientific industry from someone who is in scientific industry.

There is a big difference between lab scaled success and fully blown commercial mass production success.

Before we all clap our hands, let's see if this scales up to what would actually be used.

TheEyeofTheBeholder
5 / 5 (1) Oct 22, 2013
So at what light frequency wave does this material is most effective at collecting energy?
FainAvis
3 / 5 (2) Oct 22, 2013
I keep my car under cover to prevent its deterioration in bad weather. Your sky charged ride will be trash in a very short while. How does one factor that in when counting the cost?
Aaron1980
1.4 / 5 (9) Oct 22, 2013
we can probably get some power from using the parking lot and roads as well... have some wireless electrical field so that as the car drives down the road or is parked on a pavement it is getting some level of wireless electricity to help power its capacitors.
TheGhostofOtto1923
1.8 / 5 (5) Oct 22, 2013
it's the amount of surface perpendicular to the sun that counts
Not necessarily. Metamaterial-based cells may be able to use light irrespective of angle, allowing for curves and the use of reflected ambient light.

"Design of photonic metamaterial multi-junction solar cells
One of us (D.T.C) has shown the eectiveness of light channeling and trapping produced by cavity modes (CMs). He has found, both theoretically/numerically and experimentally,7{9 that CM-produced light trapping can lead to exceptionally high light amplications within the conned spaces of 1D cavities (gratings), allowing charge-separation domains to be bathed in a constant supply of photons, even under low light conditions."
Osiris1
3.7 / 5 (3) Oct 24, 2013
We have a transport bus made into a motor home. It is BIG, 40ft long, 8ft wide and 12 ft high. Now we think we can put about 2500 watts of solar panel on 'Rosa' and have them feed her electrical system, a 12KW computer controlled inverter that keeps 12 @ 120Amp-Hr, 12V batteries in 3 gangs of 4 ea (48V inverter). This could keep Rosa going just about all nite in cold areas without calling in the back up 13KW, 3cyl diesel generator. It is also nice that Rosa can also be plugged into our house thru a 50 Amp landline and her inverter has ability to actually SELL power back to the power company. We live in SoCal where the rates are thru the roof and 'tiered' to five levels. This will make sure the 5th and 4th tiers NEVER drive us to 'tears' again.
Eikka
1 / 5 (4) Oct 25, 2013
Which would be a nice bonus (and I'm all for adding PV to cars) - but 2.6k km is about 1/10th of the use an average person gets out of a car per year.


But you won't be driving that much in an electric car for the plain reason that you can't go very far on a charge. In an urban environment where electric cars are the most useful and gasoline vehicles make the least sense, you don't travel 26,000 km a year but more like 10,000.

Currently the PV on some cars is barely enough to run the AC


That's because the panels are barely big enough to cover the rear spoiler. The cost of covering a car's surface with panels of today's prices would pay you another car.

for the dimensions of a limousine (BMW M3) I came out to about 3 square meters (..) it's the amount of surface perpendicular to the sun that counts


PVs don't just turn off when out of perpendicular. You get about 10% power reduction for every 15 degrees off perpendicular up to about 30 degrees, and then more.
Eikka
1 / 5 (4) Oct 25, 2013
For example, take a BMW 7 series car: http://www.cardim...ns-0.jpg

The upward facing area is roughly 1.9x4.9 meters or 9.31 square meters minus the windows. If all the body panels were coated in some sort of thin-film photovoltaics I wouldn't hold it a miracle if you did get effectively 5 square meters of collection area at any given time.

Because you have to remember the sun rarely shines from straight up, so even the doors would be collecting energy throughout the day. Anti-reflective coatings also improve on the ability to collect sunlight from odd angles.
antialias_physorg
not rated yet Oct 25, 2013
Because you have to remember the sun rarely shines from straight up

Which means that at those times the upward facing parts aren't getting the 100% of the solar constant as the rays come in at an angle. At any time other than midday you're producing les than optimal amounts of energy (unless your car is higher than it is wide...which is an unusual configuration only found on some minivans).

Getting a parking space that guarantees sunlight during even part of the day (or at all) is a bit an iffy proposition. Certainly in cities I don't see that happening at all (which are arguably where many cars are parked during the day because people's jobs are there)...Parking garages are a bit of a poser, too.
TheGhostofOtto1923
2.3 / 5 (3) Oct 25, 2013
Which means that at those times the upward facing parts aren't getting the 100% of the solar constant as the rays come in at an angle
-Except for a metamaterial overlay which covered the entire car. Angle would not affect function except that projected area would be reduced. But other surfaces would gain, and so you would have to figure the aggregate projected area of all surfaces per a given altazimuth, to determine your potential.
Straw_Cat
5 / 5 (1) Oct 26, 2013
Some of you sure work hard at explaining why solar power isn't going to be an option in transportation.

A more exciting challenge would be to think of ways to make it work. For instance, your parking areas could be covered with a solar panel roof, and power drawn from the larger area that entails. As a byproduct, the car will sit in the shade. The solar collectors will work from around sunrise to sunset, not 8 hours, and the 'extra power' can be stored in batteries to recharge the car or run nearby buildings, etc.
Or, if you ride the bus, bus stops could have solar panel roofs, which will help recharge the bus when it reaches the stop. This kind of structure has, or is, already been developed by researchers/ engineers. In the 60-90 seconds a bus is stopped to allow passengers to enter/ exit, the bus is recharged by a flash charging system.
bearly
5 / 5 (1) Oct 26, 2013
When they sell a cell that is 20% or better in efficiency and sells for 1/5th the price of the junk they sell now, I will get involved. Only then !
Feldagast
1 / 5 (3) Oct 26, 2013
Ok tired of these stories, again when can we start buying what they promise?
Eikka
1 / 5 (2) Oct 26, 2013
At any time other than midday you're producing les than optimal amounts of energy


That's rather irrelevant anyhow, because we're more interested in how much energy in total you'd be able to generate throughout the day, which can be estimated to be roughly 10% of your peak output and that includes all the incident light. Just pointing a PV panel at the clear blue sky will generate about that much power.

DonGateley
1 / 5 (1) Oct 27, 2013
If we could stack all the solar "breakthroughs" I've read about in the last 20 years all our fossil fuel plants would be converted to data centers by now and converting electricity to heat (entropy?) instead of converting organics to electricity.

It won't be solar that makes that happen, it will be fission from fissiles. We've just gotta get over it and get on with it.