Way back when I was a young teenager in the early 1980s, Saturday morning TV viewing was extremely
limited. We only had three channels to choose from back then and between 9am and midday the two
main channels, BBC1 and ITV, both showed fairly inane kids programmes which I found a bit dull!
But the far less popular BBC2 often showed educational programmes from a British
institution called the Open University, and one of the series that captured my young imagination
was presented by a guy called Edward de Bono, who coined the phrase 'lateral thinking' back in the
late 60s. Lateral thinking is all about thinking outside the box to solve problems using an
indirect and creative approach and reasoning that might not be immediately obvious to most people.
It was an approach that really inspired me as a creative person and as a result I've generally
arrived at good solutions to life's challenges only after having exhausted all the bad ones! But
you know - c'est la vie. Anyway, the reason I'm telling you all this nonsense is because every
now and then I see an idea during my research that reminds me of dear old Edward de Bono's process,
and a perfect example is the concept of spherical solar panels. I mean what's not to like about
having a giant glorified glitter ball gently rotating on your roof collecting sunlight from
all angles? So could this represent a radical breakthrough in solar technology or is it
just a very creative idea that might actually prove to be less practical in the real world?
Hello and welcome to Just Have a Think. One obvious limitation of a flat solar PV panel
is that it can only use sunlight that falls directly onto its face. That means you either
miss out on a bunch of otherwise available energy each day or you spend money on solar trackers
to keep the panels pointing in the right direction as the sun travels across the sky.
The spherical solar cell design aims to boost solar power harvesting potential from nearly every
angle without requiring any of those expensive moving parts. The lateral thinking for the design
was actually inspired by nature, which by the way is often an extremely good source of ideas.
In this case it was the humble house fly that provided the blueprint for the concept,
and specifically the eyes. Evolution has selected a location and shape that increases the fly's
angular field of view to about 270 degrees about itself. That's why you keep missing them with
your rolled up newspaper! In the same way the architecture of these spherical solar cells
also increases the angular field of view allowing it to capture sunlight from more directions.
Rolling up silicon photovoltaic cells into a ball is not actually a new idea though.
Japanese firm Sphelar have been developing these tiny PV microbeads since the start of the century
for all sorts of applications including wearable solar fabrics and semi-transparent glass building
blocks, but the research team at the King Abdullah University of Science and Technology or KAUST,
in Saudi Arabia, are working with much larger spherical surfaces that they think could offer
improved efficiency and coverage especially when it comes to collecting reflected sunlight from
back plate surfaces. Their current prototype is about the size of a ping pong ball and initial lab
tests have shown some very encouraging results. And before you go hurtling down to the comments
section to point out that lab test results are not the same as real world results... I know!
But you have to start somewhere don't you? And the laboratory is usually that place, so bear with
me here. Indoor experiments have apparently already shown that these things can achieve
anything between 15 and 100 percent more power output than a flat solar cell with the same ground
area, depending on the back plate materials used to reflect sunlight onto the rear faces. The team
had already carried out previous research showing how to create thinner and more flexible solar cell
designs based on a technique using corrugated grooves. To create this spherical solar cell,
grooves were etched into a flat solar cell to make a pattern resembling a band of elliptical shapes
connecting at the middle. That gave them the flex and bend that they needed to be able to fold the
cell into its spherical shape. By simply shining a solar simulator lamp on both surfaces with no
backing plates or anything like that the team immediately saw a 24% increase in power from the
spherical cell compared with the flat cell. And it got even more interesting as the panels heated up.
Ironically solar panels don't like getting hot, it reduces their efficiency quite significantly,
but it started to become clear that the spherical cells seemed to be dissipating
heat more effectively and the result was at the elevated temperatures the spherical cells produced
39 percent more power. The next experiment was to simulate scattered sunlight instead of
direct sunlight. The differential between the two panels here was even greater with about 60% more
power coming from these spherical cells. But the most dramatic difference and perhaps the biggest
advantage of the spherical design is its ability to receive reflected light onto its rear faces.
Using backing plates made from either ordinary white paper or aluminium paper or even just plain
sand, the power output of the spherical cells was shown to be as much as a hundred percent
greater than the flat cell. The key breakthrough in the team's research process was the development
of that corrugation etching technique. A CO2 laser was used to burn through the protective
polymer covering allowing a reactive ion etching tool to create the grooves in the exposed area of
silicon below. Those are all additional steps in the production process of course, adding
cost to the overall end product. And the loss of silicon surface area where it's been etched away
will diminish the sunlight harvesting ability of the panel somewhat, but the team are convinced
that those costs could be outweighed in certain specific real world applications. For starters
you don't need the expensive automated solar trackers that I mentioned earlier,
and in very hot regions like deserts where more and more solar installations are being located
these days that heat dissipation advantage could be extremely significant. Plus the spherical shape
minimizes the accumulation of dust and sand which is the blight of flat panels in hotter countries
so there'll be no need to pay people to wash the panels down each day
or install some kind of mechanical system to do the job. The trickiest and most time-consuming
step for the Saudi researchers was to manually fold the etched cells into the spherical shape.
The cost of employing a workforce to perform that task would most likely be prohibitive
but the teams say they're designing and developing ways to automate the process using robotic hands
that can operate 24 7. The plan is to build and test large arrays of the spherical cells with the
help of KAUST alumni teams all over the world, from California to New Zealand. The arrays will
vary in size from 10 to 100 square meters and the data gleaned from the trials will provide
vital information on real-world functionality and cost benefits compared to existing operational
flat panels. So will we be seeing utility-scale solar photovoltaic globes scattered across the
land anytime soon? Well maybe not. That market is already huge and growing exponentially, largely as
a result of dirt cheap flat panels being churned out in mind-boggling quantities over in China.
But this kind of flexible tech may well find a place in more niche applications.
The research team at KAUST are already working on new shapes that resemble tents or umbrellas
and they're also investigating the possibility of integrating their flexible solar cells onto the
irregularly shaped surfaces of drones to provide a more effective and longer-lasting power source.
That sort of lateral thinking may also see these cells on a whole host of other products including
vehicle body work, uneven building surfaces and mobile devices. As always in the metaphorical
'wild west' that is the sustainable technology revolution, the proof will be in the pudding so
to speak. In other words we'll need to see some sort of quantified cost summary of all those
extra processing steps before any judgments can be made about the commercial potential of this idea.
But if they can make the numbers stack up then we might just have an innovation that would have made
dear old Mr de Bono very proud. No doubt you've got your own views on the viability of spherical
solar, so why not jump down to the comments section below and leave your thoughts there.
That's it for this week though. Just to let you know I was invited to take part
in a chat with the folks over at the Our Voices podcast recently and you can listen to that at
their website or wherever you normally get your podcasts from, and you can also watch
it at their YouTube page. I'll leave links to all those in the description box below here.
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