this episode is sponsored by ergir the cost of solar panels has dropped dramatically in recent
years however we've reached a point where lowering these costs further isn't enough to make these
systems cheaper and increasing efficiency has to become more important in determining the system's
total cost but there is a problem increasing efficiency is very hard and expensive luckily
there's also a solution we just concentrate all that light shining down onto a smaller
more efficient solar cell so the smaller size and increased efficiency offset the cell's higher cost
so why don't we just do that I'm Ricky and this is Two Bit da Vinci.
solar energy could single-handedly power the world without breaking a sweat we get about 173 000 terawatts of constant power from
the sun which is more than 10 000 times the power we would need to cover the worldwide consumption
of roughly 15 terawatts but to harness all that energy we need to build better and cheaper solar
panels cost is one of the most common factors that limit the real world application of many
promising Technologies including renewable like wind and solar we've known how to turn light
into electricity for almost 70 years now yet at first this Tech was prohibitively expensive
it's only in the past two decades that prices have dropped enough to make the technology commercially
competitive and now we have the massive worldwide adoption which is bringing prices down even
further while already cheaper than colon oil the U.S Energy Information Administration estimates
solar will become even cheaper than combined cycle natural gas electricity Generation by
2027. what drove the initial decreases in cost was the Improvement of large-scale
manufacturing which makes solar cells more accessible that price continued to decrease over
the years and today it only makes up a fraction of the total cost of a PV system adding only around
37 to 94 cents per watt of electricity produced so to further decrease costs it's not enough to just
make these cells cheaper we need to make them more efficient more efficiency will mean fewer
panels for the same output therefore saving on the panels themselves but also reducing all the other
Associated costs like installation maintenance and system balancing but there's a major obstacle in
PV cells increasing efficiency is really expensive jumping from efficiency around 18 to 20 percent
increases the cost per watt from 50 cents to 88 cents per watt that's a huge increase in cost for
just a couple of percent points of efficiency other panels reach even higher efficiencies
like the sun power maxion 6 which produces 440 Watts at 22.8 percent efficiency but those cost
nearly 40 percent more than standard panels so that efficiency comes at a huge price for
for most use cases it comes down to the best bang for the buck a perfect secular sponsor this week
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you can level up your setup and use links in the video description huge thanks to Air Gear and you
for supporting the show but if you want to go all the way in terms of efficiency you have to choose
multi-junction solar cells these cells work by sandwiching different layers of semiconductors
from groups three to five on the periodic table to create multiple PN Junctions each one optimized to
absorb a specific wavelength band allowing us to use more of the available energy these cells
are already commercially available but can cost 400 times more than your typical utility scale
solar panels they're so expensive in fact that they're basically reserved for space applications
only we've already did a whole video on these record-breaking PV cells a few weeks ago where I
explained in detail how multi-junction cells work and how they're made you can check out that video
if you haven't already links in the description but I'll bet by now you're wondering how could
paying 400 times more for an output that's only about twice what you'd get with a normal panel
possibly make any sense that's where concentrated PVS come in in essence a concentrated photovoltaic
or cpv is a device that collects light from a large surface area and concentrates it onto a
small PV cell it works the same way how we used a magnifying glass to burn through wood and paper
when we were kids concentrating light allows us to generate more power with a smaller PV
cell but it turns out that it also improves the cell's performance so it's a win-win that will
finally bring the best PV cells in the world to the mass Market in a cost-effective way for you
and me to enjoy now cpvs come in several different designs depending on whether we use MERS or lenses
for example mirror collectors can have different shapes like parabolic through collectors parabolic
dishes and mirror arrays in the case of lenses the most common are fresnel lenses but there's a new
special 3D printed design created by researchers from Stanford that'll get back to in just a minute
and you'll also find other exotic Optics that combine lenses and mirrors we can classify cpvs
according to the level of light concentration this is usually expressed as a multiple of suns
which is the average iridescence per square meter at solar noon near the equator and is equivalent
to about 1 000 watts per meter squared so then two suns will be equal to 2 000 watts per meter
squared 10 cents would be 10 000 watts per meter squared and so on depending on how many suns The
Collector Shines on the PV cell we can have three types of cpvs low concentration cpvs that go from
1 to 10 Suns medium concentration cpvs that go from 10 to 100 and high concentration cpvs that
magnify light to 100 Suns and more a common question is why is concentrated light onto a
smaller area any good if in the end we're still using the same amount of light from the sun well
it turns out there's actually quite a few benefits to doing so the biggest benefit of concentrating
sunlight as opposed to shining PV cells directly is that you can use a much smaller cell to capture
the same amount of light and don't forget for now lenses and other concentration materials
are probably a lot cheaper than the PV cells themselves so take light from Big area Shrine
down to a smaller cell win-win this alone helps bring solar panel cost down significantly since
surfaces like mirrors and lenses are much cheaper than photovoltaic surfaces especially compared to
multi-junction cells for reference validary green power sells a fully mounted 7.2 square
meter panel with 30 efficiency and a two axis Sun tracking system for only 90 cents per watt
which is 4 cents cheaper than a standard utility scale PV module mounted on a one axis tracker I
mentioned earlier second although silicon is the second most abundant element on Earth the group
three to five semiconductors used to manufacture high efficiency multi-junction solar cells are
in much shorter Supply concentrating light and minimizing the size of the PV cells helps us use
less material making these panels Greener cheaper and easier to find and produce at high scale
finally I already hinted at how concentrating sunlight improves cell performance but this
is more than just about delivering more power the cell's efficiency also increases with more
concentration notice how the conversion efficiency of this record holding TV cell made by frondhofer
ISC increases from just under 40 percent at one cent to 47.6 percent when radiated with 665 Suns
this is the single biggest perk of concentrated PV cells I mean increasing efficiency by about
eight percent just by shining a brighter light starting to make sense isn't it at this level of
concentration a typical panel which is roughly two square meters in size will concentrate two
thousand watts of solar energy onto a square roughly 2.16 inches on the side around 55
millimeters also a cell would produce 952 watts of electricity while a typical solar panel of
the same size would produce only 400 watts of electricity so that's one 665th of the size and
2.38 times the output from the concentrated solar cell that's an improvement of 1582 times compared
to the average 20 efficient cell this is simply amazing and makes concentrated photovoltaics an
absolute no-brainer I can already imagine you wondering so then why are we concentrating light
on all solar panels well as you can probably imagine concentrated photovoltaics have plenty
of engineering challenges to overcome first because of the carefully aligned Optics usually
involved a very important part of getting a cpv to work properly is to make sure that it
receives direct sunlight but as you know the Sun never stays put it describes an arc from east to
west every day and that Arc also shifts north to south and Back Again throughout the year according
to the season and the hemisphere you're in this generally means that concentrated photovoltaics
need to track the sun constantly every day of the year requiring heavy and expensive two-axis
tracking systems this increases installation and maintenance costs and makes it next to impossible
to install on your roof for example however a group of researchers from Stanford came up
with a clever solution they designed a system that concentrates light with a special 3D printed lens
they call axially graded index lens or agile got to give them for the marketing which is something
like an inverted pyramid with its tip lopped off this special lens takes light coming from almost
any direction through the top surface and guides it down the pyramid toward the PV cell this not
only eliminates the need to track the Sun but also captures and concentrates diffuse like sky
scattered by clouds in the atmosphere something no other technology manages no tracking and no
moving Parts also means you can install them on your roof however there is always a trade-off
their current agile design can only concentrate light to three Suns so it's a low concentration
system and it loses 10 percent of the incoming light which eats into the overall efficiency
considerably that said this is just a prototype and they may come up with a larger and better
agile lens in the future that can overcome some of these hurdles a team from Penn State University
took a slightly different approach to tackle the issue of solar tracking on concentrator PVS they
decided to fix the Optics and instead move the PV array to align the cells with a moving focal
point of the reflected light second as any kid knows concentrating sunlight into a small surface
area generates a lot of heat and this brings all sorts of problems to PV cells first of all the
PV cell's efficiency decreases with temperature based on the following equation you can see that
in the following graph in some k cases of PV cell that starts off with an efficiency as high as 25
percent at low temperatures ends up at only around seven percent at 200 degrees Celsius additionally
some PV cells can also suffer permanent damage if heated above a certain temperature this means
that if the concentrator is too high the panels need to be cooled low concentration cpvs don't
usually require any cooling at all and medium concentrator cells are usually fine with passive
cooling using cooling fins and heat sinks but for high concentration solar cpvs active cooling is a
must this can be a curse or a blessing because by extracting generated heat and using it for
something else we get a hybrid system with an overall efficiency that can easily surpass 65
percent or more so win-win all round another issue to consider is that solar tracking and
active cooling systems add complexity to the system making it more likely to fail and require
more maintenance all this adds cost that makes operating these systems more expensive than your
typical rooftop panel I mean those are literally set it and forget it there's really nothing else
you have to do maybe clean them like once or twice a year finally there are other issues that may
come up with non-uniform temperatures which can lower the overall efficiency of cells connected
in series and the fact that access heat can lead to a shorter lifespan of the system will result
in a higher lcoe or levelized cost of energy I honestly think that if the guys at Stanford and
there are a bunch of smart guys I'm sure they can can turn their 3D printed agile lenses into
high concentration photovoltaics and reduce their losses this could be huge for the future of solar
imagine getting twice the power for the same size panel you're using now while using less
semiconductor material harnessing even diffuse light without having to track the sun it almost
sounds too good to be true so I can't wait to see if it makes it to the market so really this comes
down to a simple trade-off today's PV cells are non-concentrated which means they just one to one
every square of light coming in it captures but they're not very efficient only around 20 percent
that means one in five of the photons of light coming then is actually producing electricity
how do we get that up well using more exotic materials but those cost way more if you think
about the solar that they use on the space station or satellites in space they're crazy expensive
they use really exotic materials but they have to because they have to be really efficient but here
on Earth in order to sell a 10 kilowatt system of 29 panels to a residential home buyer you'd
have to get the cost under control and this might be the way to do it and that cool 3D printed lens
idea is really interesting because you don't need to have moving Parts the minute you have moving
trackers that really limits where you can put them you can't put them on a roof because the
roof is going to limit the the movement so you'd have to have like a ground Mount system and that
could make sense for parking lots and other structures but for homes that lens concept
is really fascinating and this is an entire topic that I think we should continue to cover as future
breakthroughs happen and we will so that is a look at concentrated cpvs take a look at this
video next I think you're going to like and until next time I'm Ricky and this is stupid DaVinci