Solar Panels have proven vital for moving us closer to a net zero reality while also bringing
down our energy bills. Over the last few decades we’ve seen solar panel costs drop significantly.
But, the technology has hit a bit of a ceiling in terms of efficiency, which can be a problem
if we want better solar for our homes, and more solar energy powering our grids!
But that ceiling has just been smashed by a team of researchers who have made the most
efficient panels of all time using innovative Quantum Well technology.
But… what are Quantum Wells? How do they improve solar efficiency? And
what impact could this laboratory breakthrough have on you and me?
In order to better understand this new breakthrough,
let's take a quick refresher on today’s typical solar panels.
The solar panels you’d put on your roof use monocrystalline silicon as the main component
materials. Since residential solar debuted in the 1980s, the price per watt has fallen a jaw
dropping 99%! And while the technology has also seen improvements since it was first developed,
that progress has stagnated in the last few decades.
Researchers at the US National Renewable Energy Laboratory
have been working toward creating more efficient panels for decades.
Their last big breakthrough in 2020 saw panels reaching efficiencies of 39.2%. But their latest
panels push those efficiency levels even further — to 39.5% — a new world record.
Now, you might be thinking … 39.5% doesn’t sound very efficient. But let’s look at how
these panels compare to your typical solar panel.
Even today’s high efficiency perovskite panels top out around 25%. But your typical
home solar panels run around 20%. Solar efficiency is measured using what’s called
“one-sun illumination,” a standard metric for measuring light intensity,
where one sun corresponds to the standard illumination at 1 kW/m2. I guess if you
lived on Tatooine, the metric would be different, since they have two suns.
Using this metric, a standard 2 meter square panel operating at 20%
efficiency would generate roughly 400 watts of electricity.
Again, 20% efficiency may not sound like much — but consider
that a typical car engine only runs somewhere between 12% and 30% efficient.
But these breakthrough panels — nearly double the energy efficiency
of standard silicon based panels. Under that same one-sun metric,
that same 2 m2 panel using these experimental cells would generate roughly 790 watts!
Imagine being able to produce the same amount of electricity as today’s solar systems but using
only half of your roof’s surface area? This could
be excellent for smaller homes, or in cities where buildings are taller but have less roof space!
Then there’s grid scale applications. Using more efficient solar panels could free up usable land
while still producing the same amount of energy. Or they could
produce nearly double the amount of power using the same amount of land
which could definitely make a more sizeable dent in the energy market!
Right now, wind is generally considered the most efficient energy source.
And while a number of factors determine the overall efficiency of a given technology,
in general, Solar tends to rank far lower than other renewables. Now,
this typically doesn’t matter since you can fill an entire field with solar panels. But
just think of the reach solar energy could have if we could double its efficiency!
Now one thing to point out is that experimental panels using more highly concentrated light have
reached higher efficiencies — above 40%. But real world applications use standard concentrations of
sunlight, so for that metric, these panels are by far the most efficient ever made!
There are a few key components that set these panels apart.
A traditional solar cell uses doped silicon, that means silicon mixed with ​​with impurities
such as gallium and arsenic atoms that increases its ability to capture and convert solar energy.
A solar cell typically has two layers — an n-type (negative) with a high concentration of electrons
and a p or positive type with, you guessed it, a low concentration of electrons.
When sunlight hits the n-type layer, electrons flow from one side to the other,
creating an electrical current that can be captured and used for power. This type of
solar cell is known as a single-junction solar cell, as it has one single boundary/junction
between the n-type and p-type layers, known as a p-n junction. This single bandgap is tuned
to capture certain wavelengths of light, which is one reason why their efficiency is so limited.
The new panels address those limitations by using multiple junction points — three
to be exact. Each junction uses different materials that concentrate on a particular part
of the solar spectrum, meaning fewer wavelengths escape and more is converted
into electricity. The layers are based on what are known as III-V materials — a
group of elements on the periodic table that serve as excellent semiconductors.
Lower, also called narrower, bandgap materials will convert longer wavelength,
lower energy photons. Higher, or wider bandgap materials will convert shorter wavelength,
higher energy light. Cells made from multiple materials can have
multiple bandgaps and will therefore respond to multiple light wavelengths,
capturing and converting some of the energy that would otherwise be lost to relaxation.
But the innovations don’t end there. The middle layer of these cells uses a
material called Gallium Arsenide due to its near-perfect material quality even though
it has a higher bandgap than is typically considered optimal for the global spectrum.
This essentially means that the balance of photocurrents between the three layers doesn’t sit
quite where it should, according to Ryan France, senior scientist and cell designer at NREL.
To make up for this sub par bandgap, the researchers modified them using quantum wells.
No — that’s not where Ant Man gets his drinking water from.
This approach was key to the huge increase in efficiency. The physics here
is a bit complex and certainly beyond the scope of a ten minute YouTube video.
But basically, the team used thin nano-structures of carefully selected conductive materials
and sandwiched them between the cell materials. This allowed the team to fine tune the bandgaps,
especially in that middle layer, to absorb even more of the light spectrum,
optimizing performance. The middle layer contained up to 300 quantum wells in total.
So while this breakthrough is truly remarkable, there’s one glaring
question — how will these solar panels impact everyday consumers like you and me?
We can’t wait to dive into that, but before we do, let’s hear from today’s sponsor…
The researchers acknowledge that these panels won’t likely
see commercial applications for quite some time. The main reason, as always, is cost.
Right now, producing these multijunction panels costs roughly $10 per watt! As of 2022, the The
Solar Energy Industries Association estimates that the cost for a typical 6 kW solar system
comes out to around $2.50-$3/ watt, costing anywhere between $14,000 and $18,000.
A similar sized system using these new panels would cost upwards of $60,000!
Even at nearly twice the efficiency — that’s far too great a price hike to make these panels
worth it, at least for now. So then — why does this breakthrough matter?
Well, it's important to think of technology with the larger picture in mind. In the 1950s when
solar technology was beginning to emerge, cells operated at around 4% efficiency and
cost over $300 per watt! Back then, they were really only used in satellite technology. It
would be another three decades before residential solar would become available.
In fact, one market for these solar panels could be space vehicles and satellites.The
ISS currently uses triple junction cells with around 30% efficiency. This could be a
promising application as more and more companies plan to launch telecommunication satellites,
develop commercial space flight, and even set sights on the Moon and Mars.
While that may not seem like it impacts us here on Earth, the fact that there’s already a potential
market for this technology is a good sign. The more commercially viable a product becomes,
the more can be produced at a commercial scale, which can ultimately bring down prices.
Even since 2009, the price of residential solar has dropped
dramatically — from around $8.50 per watt to the current $2.50.
Researchers from Toyota and electronics giant Sharp Industries are also looking
into potential applications for triple junction solar cells — for example,
solar vehicles Higher efficiency could certainly bring that closer to reality.
Ultimately, we understand that breakthroughs like these may
not have a direct impact on us today, but will benefit us in the long run.
And in this case, it will probably look like 5-10 years before this technology,
or some variation of it, finds its way into the marketplace, as opposed to decades.
The team at NREL is already working on a few different
methods to drastically reduce these costs.
As we mentioned earlier, there are many new technologies in development right now
to help improve solar efficiency. One showing a lot of promise is
perovskite solar cells. You can learn more about them by watching this video!
But what do you think? Are you excited about this new solar efficiency breakthrough? Or do
you think it's more pie in the sky greenwashing fantasy? Sound off in the comments below!