Sponsored by Brilliant. Among renewables,
solar energy has been growing rapidly and driving the world towards a low-carbon future.
We've been seeing a wave of innovations in the field, like perovskite solar cells, solar tiles
and roofs, and organic panels. But what if we could harvest solar energy from the windows
and skylights of our homes and skyscrapers, or even from our car windows and cellphone screens?
Let's explore transparent solar panels and how they stack up against conventional panels.
Could transparent solar cells be the future of solar energy? Or is the future not so clear
I'm Matt Ferrell ... welcome to Undecided.
In modern society we see glass everywhere, ranging in size from a small cellphone screen
to huge windows and skyscraper façades. It's estimated that there are 5-7 billion square
meters of glass surfaces in the United States ... so imagine that number for the whole world.
And in most buildings these large areas of glass remain an unused energy potential.
According to the International Energy Agency (IEA),
buildings and the construction sector add up to one-third of the total energy consumption in the
world. That represents 40% of total direct and indirect carbon emissions into the atmosphere.
And even though we've seen some progress there, which I've talked about in a previous video
there's still a long pathway to decarbonize buildings around the world.
Designs that employ passive heating and natural illumination through triple-glazed windows
and use rooftop solar panels look great, but what if we could go one step further? What if we could
tap into all of that solar energy potential passing through the glass façades and windows,
not only to provide natural illumination and heating, but to produce electricity?
Enter transparent solar panels.
Photovoltaic glass, as this technology is also called, is a see-through type of solar panel,
and unlike traditional mono or polycrystalline silicon panels ... which are opaque ... this
new technology is manufactured to provide some level of transparency.
In theory these panels can be employed in anything from small mobile devices
such as cellphones and laptops to huge windows of skyscrapers. But while standard solar panels
absorb visible light to produce power, a truly transparent solar panel works based
on a counter-intuitive idea: capturing invisible light and letting visible light pass through it.
The term "transparent solar panel" makes most of us think of something that's as
transparent as a glass window, which is a little misleading. Technically,
this term can refer to both a panel that's completely or only partially see through,
so let's take a look at the two types of transparent solar panels.
**1) Partially transparent solar panels** These panels are manufactured using a
thin-film technology in which ultra-thin layers of semiconductor material are deposited over a sheet
of glass. Then, another sheet of glass is glued on top to form a tasty semiconductor sandwich.
These ultra-thin layers of semiconductor material (and we're talking about the thickness of a
few microns) is what makes these solar panels become transparent,
and each layer you add increases the opacity just a little bit.
While current silicon panels, like you have on your rooftop, achieve efficiencies above 20%,
the efficiency of standard thin-film solar panels is considerably lower at around 7-10%.
A great application of partially transparent solar panels is in office buildings where
the sunlight is intense, so the panels are installed in order to reduce the sunlight
level that goes into the building. when designing windows and skylights. The SHGC
basically measures the amount of available solar heat that can pass through the glass.
The higher this percentage, the more heat goes into the building.
The SHGC of Onyx's panels, one of the leaders in transparent PV glass for buildings,
range from 10% to 40%, limiting the solar heat that goes into
the building while producing electricity at the same time.
**2) Fully transparent solar panels** The dream of having solar panels that
would look like regular glass started with a group of researchers at Michigan
State University (MSU), which created the first fully transparent solar cell in 2014.
The team created the transparent luminescent solar concentrator (TLSC),
which uses organic salts to capture only a specific portion of the solar spectrum
containing specific wavelengths of invisible light, such as ultraviolet (UV) and
infrared (IR), while allowing normal visible light to pass through.
When sunlight hits the panel the UV and IR lights are turned into a different
type of infrared that glows. Then this new wavelength moves to the edges of the window,
where it's converted into electricity by solar cells.
Since the materials don't absorb or emit light in the visible spectrum, they look transparent
to the human eye. The transparent solar panel created by the researchers achieved an 86%
transparency level. Unfortunately, the efficiency of this prototype was
very low (less than 1%), but they said that there's a potential of reaching 10% efficiency.
Compared to conventional crystalline silicon-based panels, it's obviously a big negative that the
efficiency of transparent solar panels is so low. But when it comes to solar panels,
efficiency isn't everything. The low efficiency of transparent solar panels means that we'd need
a larger area covered in order to produce the same amount of power as a 20%-efficient
rooftop solar array. However, given how transparent solar panels can be integrated
into buildings there's more potential surface area to compensate for this lower efficiency.
An interesting advantage of partially transparent solar panels is that thin-film solar cells
can achieve high efficiencies even when they're not at the optimal tilting angle,
which is great for buildings and skyscrapers where the windows are installed vertically.
Thin-film cells are also more tolerant to heat, having a lower decrease in efficiency
than traditional crystalline silicon solar panels at high temperatures.
Fully transparent solar panels have a clear advantage over partially transparent versions,
since they can turn any glass sheet or window into a photovoltaic cell, they look better,
and have a wider range of use cases. But their big negative isn't just their low efficiency.
Transparent solar panels utilize organic solar cells, which degrade more rapidly
than inorganic solar cells. Thin-film, for example, last from 10-20 years,
while panels based on crystalline silicon have an average lifespan of 25 years.
Although there are still many improvements to be made,
the benefits and wide range of applications ... mainly in
the building sector ... has led companies around the world to explore the technology.
But before getting to where we're seeing this tech show up today, if you're interested in
learning more about the principles behind solar, I'd strongly recommend checking out
the Solar Energy course at Brilliant. It's a fun, hands-on approach that really helped me
wrap my head around some of the central pillars of how solar power works. Everything from the
basics of photovoltaics, to solar thermal power, to photon absorption. It's a really good one.
But even if that course doesn't make your brain light up, there's going to be something else
you'll enjoy. They have over 60 courses including topics in scientific thinking,
quantum mechanics, and applied science. They've got something for everybody.
All of the concepts are taught through fun and interactive challenges to help you understand
the "why" of something ... not just the "how." It helps to develop your intuition,
which is my favorite part about Brilliant and taps into the way I learn ... and just makes it fun.
Go to www.brilliant.org/Undecided to sign up for free. The first 200 people will get 20% off their
annual premium membership. Thanks to Brilliant and to all of you for supporting the channel.
So back to where we're seeing ... or not seeing ... transparent solar panels spring up.
Onyx Solar is one of the leaders in transparent PV glass for buildings. The
company offers two technologies of solar glass, one based on amorphous silicon
and another on crystalline silicon, with options ranging from 0% transparency up to 38%. Their
panes use layers of heat-treated safety glass and can be customized to fit specific projects
into anything like curtain walls, canopies, or even floors, but I'll step on that in a minute.
An interesting project using their Photovoltaic Skylight is the McDonald's Flagship Restaurant
in Walt Disney, in Florida. The building became a zero-energy building and the first zero-emission
restaurant in the U.S. The system is expected to produce over 2M kWh of electricity over 35 years
and will have a payback time in less than 4 years.
Another product from Onyx is their PV Façade. Among its projects, the company
created the façade for FEMSA's headquarters, which is the largest Coca-Cola bottling
plant company in the world (Monterrey, México). It consists of 370 large-sized grey amorphous silicon
glass modules with a 20% transparency, and can produce about 17,200 kWh of energy. Overall, this
project is expected to have a payback time in less than 1 year and reduce HVAC energy demand by 24%.
But you could also take a huge step into the future ... and onto a photovoltaic
floor ... with the company's PV pavers. They're designed to be used for pedestrian traffic and
can withstand up to 400kg (~880lbs). On top of that, they can be customized in a wide
range of colors and use the same installation procedures as metal framing and wood floors.
One project that's gaining traction is a Manhattan penthouse that used 50 glass pavers
for an innovative and solar harnessing terrace. The photovoltaic system reduced
19% of the penthouse's HVAC demands and produces green electricity at the cost of about $0.012.
Talk about taking a walk on the bright side.
And when it comes to cost, their PV glass costs about $50 per square meter,
while a typical solar panel cost usually ranges from $40-110 per square meter,
and a typical double-pane window costs around $24-45 per square meter here
in Massachusetts ... including material and installation costs.
As cool as those are, transparency levels aren't good enough for applications where
you need clear windows that look like common glass. For that you'd want to look
at the Australian-based ClearVue, which has been manufacturing solar panels that are clear ... with
a minor tint ... and have no visual distortion, achieving a transparency of 70%. Their technology
is composed of several layers, but in short, their glazing system consists of nano and microparticles
scattered over an interlayer of thin film sandwiched within panes of glass.
The price per square meter for a triple-glazed, low-emissive, insulated glass unit from ClearVue
is $400. Comparatively, a common triple pane window ranges from $270-430 per square meter.
One of their projects was the Warwick Shopping Centre Atrium in Perth, Australia.
The installation includes 18 triple-glazed, low-emissive PV glass panes that provide power
to the indoor lighting, outdoor signage and the display of the shopping center.
And according to an article from the company, each solar
window of this building was able to produce approximately 0.1 kWh from 6-7 hours of sun.
Depending on the project, the company estimates the financial payback period can be as low as
a year. The carbon payback is less than 9 years, compared to 100 years for typical
double-glazed windows. They claim that by using inorganic materials,
these PV windows can produce power for more than 20 years, with a 0.5% efficiency loss per year.
But again ... when we come back to efficiency it's not that great. Today, their industry-standard 3.5
x 1.6 meters solar window can give 30 W/m² while a typical 340W solar panel can give about 200W/m².
That means to produce the same power of a rooftop PV system,
we'd need 6 times more area for these transparent solar panels to equal out.
But there's where we get back to some of the really interesting research being done.
Aiming to increase the efficiency, the University of Michigan,
and the team led by Stephen Forrest, has been getting interesting results.
They've been exploring the use of organic materials in the panels,
but the main challenge is how to prevent rapid degradation. To overcome that problem the team
has been adding layers to the sun-facing side of the glass. They tried multiple materials
in various tests, but the latest one with a fullerene material has shown some promise.
They tested this new transparent solar panel under several conditions, like simulated
sunlight that could shine the equivalent of 1 sun up to 27 suns, and temperatures up to 150ºF
(65ºC). The conclusion was that the solar cells could still provide 80% of their power even after
30 years. They've also achieved a 40% transparency and believe it's possible to increase that number
to 60%. And they're also working hard to raise the 10% efficiency up to 15% at higher transparencies.
It's not hard to see that transparent solar panels still have a challenging pathway to full
transparency at higher efficiencies (or at least efficiencies closer to typical solar panels),
and power densities at a reasonable costs for the market.
Today, with an efficiency lower than 10% and power densities of 30W/m²,
this technology still requires a considerably larger area to produce the same amount of power
that rooftop PV systems can give. But it's also important to remember that the
University of Michigan increased the original <1% efficiency in 2014 to about 10% in 2021. That's
significant and pretty exciting ... hopefully the technology becomes more cost-competitive in time.
What do you think? Do you think we'll see transparent solar on most of our buildings ...
maybe even cars, laptops, and smartphones in the future? Jump into the comments and let me know.
And thanks as always to my patrons. Their direct support really helps with producing these videos.
Speaking of which, if you liked this video be sure to check out one of the ones I have
linked right here. And subscribe and hit the notification bell if you think I’ve earned it.
Thanks so much for watching and I’ll see you in the next one.
^onyx_façade:Photovoltaic Ventilated Façade And
Roof