Ever since Charles Fritz coated the semiconductor Selenium with a thin layer of gold to make the
first solid-state photovoltaic cell way back in 1879 science bods all over the world have
been developing the process to make it more efficient more practical and less expensive.
Modern panels are about 20 times as efficient as those first prototypes and recent mass production,
mostly in China has brought prices down to extremely competitive levels. Solar PV panels
are perfect for rooftops and ground mounted arrays and of course they're already playing
a major role in the transition away from fossil fuels towards more sustainable electricity grids,
but there are millions of surfaces in our modern world that are not quite so conveniently flat and
many of them also get exposed to sunlight every day. No doubt you've heard the statistics about
the mind-blowing amount of sunlight that reaches our planet but it doesn't hurt to remind ourselves
every now and then that the amount of power from the sun striking the earth in one single
hour is more than the entire world consumes in a whole year. Unsurprisingly then a whole sphere
of research has grown up to find ways to build solar PV technology into thinner and more flexible
materials that might be able to take advantage of all those currently under utilized and
awkwardly shaped surfaces. Thin film cells have been used in things like solar powered calculators
since the 1970s. Nowadays we're starting to see flexible panels appearing on some
electric vehicles and in a few very sophisticated building integrated systems but it's still far
from mainstream and that's a shame because if someone can really nail it then flexible thin
film photovoltaics could be mopping up the sun's energy all over the place providing immediate
localized energy to drive our modern technologies with zero carbon emissions at the point of use.
Well now a UK company called Power Roll reckon they've come up with a revolutionary new way of
fabricating highly efficient flexible photovoltaic rolls that could just fit that bill perfectly...
Hello and welcome to Just Have a Think. Power Roll are a specialist materials architecture company
based in County Durham up in the north east of England. They've teamed up with a physicist
and inventor by the name of John Topping who has extensive expertise in the production of
vacuum coated materials used in the food packaging industry - you know things like those
snack wrappers with metallized internal surfaces. Apparently John had a bit of an epiphany moment a
few years back when he realized that it it might be possible to combine those very inexpensive roll
to roll vacuum coating systems with the latest microscale printing and embossing technologies
to come up with a process that could manufacture solar photovoltaic films at the same speed and
with the same mass production economies of scale as food wrappers. I caught up with the Chief
Executive of Power Roll, Neil Spann, via Zoom a few weeks ago to learn more about how the process
works. A typical solar panel is made up of a transparent conductive oxide or TCO layer
on top of a semiconductor - typically silicon. The top section of silicon is infused, or doped,
with another element like phosphorus and the bottom section is doped with something like boron.
When photons hit the silicon layer they knock electrons free and for reasons that are outside
the scope of this video the two doped materials act like electrodes on either side of a battery
and facilitate the movement of those electrons out of the photovoltaic sandwich
and into an electrical circuit. We looked at exactly what causes this to happen
in an earlier video about perovskite solar panels so if you're keen to get the detail
then you can click the link up there to jump back to that one. The Power Roll system effectively
turns that sandwich arrangement on its side. The starting point is a pretty standard polymer
substrate like PET, into which tiny micro structures are embossed creating v-shaped
channels or grooves in the material that are no more than one or two microns thick. That's about
one-fiftieth of the width of an average human hair and about a fifth the width of a human blood cell.
A 10cm by 10cm square can contain 17,000 of these channels running parallel to each other
across the width of the panel. A vacuum coating system applies the electrodes and
electron transfer layers equivalent to the horizontal layers in a standard silicon cell
effectively creating negative and positive electrodes. Power Roll has developed a unique
proprietary technique to ensure an even coating and to make sure that the two materials can't
come into contact with each other at the base of the groove, because that causes a short circuit
which you don't want! Then a solar absorbing ink is printed into the middle part of the groove.
That arrangement does away with the need for the expensive TCO layer.
Light just comes straight in, hits the ink, and contacts with the electrodes on either side.
There's a single vault of potential difference in each groove based on the current solar ink
the power roll is using and the architecture of the construction means the grooves are physically
connected together in series - in other words negative to positive. You may remember from
school physics lessons that connecting batteries in series adds up their voltages. That means a
piece of material that's only 10cm wide can have a potential difference across it of 17,000 volts.
Now, sticking 17,000 volt materials onto the sides of bus shelters and letter boxes
is probably not a great idea, so the next step in the parallel process is to physically separate
the channels into microscopic modules or cascades as they're known. It's a patented technique that
Power Roll call delineation. The grooves can be split into as many or as few cascades as necessary
depending on the voltage required by a given application. So, for example by splitting 17,000
grooves into 340 cascades each cascade will have a potential difference of 50 volts which sounds a
bit less fatal doesn't it? The separated cascades are then connected back up in parallel which keeps
the voltage the same but increases the current. That means the size of the current is derived
not just from the length of each conductive groove but also by how many parallel connected cascades
there are on the panel. Another crucial proprietary element of the process is a technology
that ensures extreme accuracy in the separation between the cascades, again eliminating the risk
of unwanted cross communication. The panel gets a final protection coating, and that's it. Done. All
that's required now is for wires to be attached to either side to produce an electrical circuit
and of course some photons from sunshine to start knocking those electrons out of their comfort
zone. One of the beauties of this configuration is that if one cascade is in shade or gets damaged
it doesn't affect the other cascades either side of it - they just keep on generating
regardless. You could literally nail one of these things to a wooden post and it'd keep working,
although that's obviously not going to be the recommended installation procedure!
Instead a highly adhesive backing film will be supplied to do the job. According
to the folks at Power Roll their process is completely unique and extremely inexpensive
because it's based on the smart combination of already existing technologies.
The embossing technology is the same as the systems used to create the little holograms
on your credit and debit cards. The vacuum coating technology comes straight from the food packaging
industry, and the ink printing technology is well established in many different sectors.
Working out how to combine all three together effectively has taken a great deal of development
work though, and the Power Roll process is now patented in 70 countries around the world.
Full scale production films will be produced in widths of either 30 50 or 100 centimetres,
and a typical panel will be up to 10 metres in length. The business model here
is not to directly compete with existing rigid solar PV panels. The efficiency of the parallel
film is currently about 11% with a development path towards 16%. No, the main goal is really to
drive down the cost of production and provide a solution that can easily be replicated anywhere
in the world energizing previously inaccessible surfaces to produce very useful local electricity.
Power Roll have been working with test houses in the U.S and Europe including the American
National Renewable Energy Lab, or NREL. Test data suggest that a roll of film light enough for an
average person to carry in their arms would have a generating capacity of 20 kilowatts.
That opens up all sorts of applications that are only really limited by the imagination,
not just in industrialized countries but in developing nations as well.
In remote off-grid locations they could become a very inexpensive
and portable carbon-free replacement for diesel generators and kerosene lamps. They'd also be a
perfect fit for tensile structures like the roof of the Millennium Dome in London for example,
or perhaps more usefully on tents in refugee camps that are sadly becoming more and more
commonplace as climate change and regional conflicts continue to flare up around the world.
The production of the film itself does of course have a carbon footprint mainly in the
PET material used as the substrate, but there are no high temperatures involved in any of the steps
and overall it's a high speed low energy process. Compared to traditional rigid silicon PV panels
it only has about one 20th of the carbon impact. The levelized cost of electricity has also been
analyzed and assessed to be 45 percent lower than rigid PV panels which translates into about half
the payback time of a traditional solar PV installation. The next step for Power Roll
is full testing to achieve global industry accreditation. One of the results of that testing
will be a certified operational lifetime, but Power Roll's own fairly rigorous internal tests
have shown this to be a very robust product with a projected lifetime of between 10 and 15 years.
Power Roll will maintain a production and research and development facility
here in the UK and then license the technology to manufacturing partners around the world.
Partnering with companies in other territories is a smart strategic move. It accelerates the
speed of global distribution and utilizes local expertise to reach otherwise inaccessible markets.
It also affords some protection against patent infringement and counterfeiting
which will almost certainly become a challenge as the technology gains in popularity.
The UK pilot plant will be finalized in 2021 with larger volume production and commercial
licensing commencing in 2022 and mass production in multiple geographic locations during 2023.
As we transition to a more sustainable future we'll need every viable renewable technology
available over the coming decades. Decentralized distributed power sources like this one will
play a big role in that effort and they have huge potential to transform lives all over the world.
As always if you've got experience in this industry or views about this technology
one way or the other then why not jump down to the comment section below and leave your thoughts
there. That's it for this week though. I'm having a snoop around the COP 26 climate conference up
in Glasgow for the next few days, so there'll be no video next weekend, but I'll be back with
another dive into the world of climate change and sustainable energy on Sunday the 14th of November.
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