The solar cells you see on many roofs today are built out of silicon, the same stuff that powers your computer and smartphone. The reasons for this are many but it mostly comes down to silicon’s durability, semiconductor properties and ease at which we can mass produce them thanks to our investments in semiconductor manufacturing. However they’re not the only type of solar cell we can create, indeed there’s a different type that’s based on polymers (essentially plastic) that has the potential to be much cheaper to manufacture. However the technology is still very much in its infancy with the peak efficiency (the rate at which it can convert sunlight into electricity) being around 10%, far below even that available from commercial grade panels. New research however could change that dramatically.
The current standard for organic polymer based solar cells utilizes two primary materials. The first is, predictably, an organic polymer that can accept photons and turn them into electronics. These polymers are then doped with a special structure of carbon called fullerene, more commonly known as buckyballs (which derive their name from their soccer ball like structure). However the structures that form with current manufacturing processes are somewhat random. This often means that when a photon produces a free electron it recombines before it can be used to generate electricity which is what leads to polymer cell’s woeful efficiency. New research however points to a way to give order to this chaos and, in the process, greatly improve the efficiency.
Researchers at the USA’s Department of Energy’s SLAC National Accelerator Laboratory have developed a method to precisely control the layout of the polymers and fullerene, rather than the jumbled mess that is currently standard. They then used this method to test various different arrangements to see which one produced the highest efficiency. Interestingly the best arrangement was one that mimicked the structure we see in plants when they photosynthesize. This meant that the charge created in the polymer by a photon wasn’t recombined instantly like it usually was and indeed the polymers were able to hold charge for weeks, providing a major step up in efficiency.
Whilst this research will go a long way to solving one of the major problems with polymer based solar cells there are still other issues that will need to be addressed before they become commercially viable. Whilst a typical silicon solar cell will last 20 years or more a polymer one will only last a fraction of that time, usually only 4 years or so with current technology. For most solar cells that amount of time is when they’ve just paid back their initial investments (both in terms of energy and revenue) so until they get past this roadblock they will remain an inferior product.
Still research like this shows there’s potential for other technologies to compete in the same space as silicon, even if there are still drawbacks to be overcome. Hopefully this research will provide further insights into increasing the longevity of these panels at the same time as increasing their efficiency. Then polymer panels could potentially become the low cost, mass produced option enabling a new wave of investment to come from consumers who were previously locked out by current photovoltaic pricing.
I’m sure I’m not alone in being someone who loves playing around in the sand at a beach even though I’m pushing 30. My friends and I always seem to end up building some kind of sand castle whenever we all make our way down there even though we usually have no intention of doing so. There’s probably some nostalgia at work there, I mean almost everyone has great memories of playing the sand as a child, but I’ve also been told it’s actually quite therapeutic something a cursory stroll through Wikipedia appears to verify. However bringing the beach with you is usually frowned upon (What do you mean I can’t make sand castles on the carpet??) but it seems like there’s a pretty awesome substitute in the form of Moon Sand.
It’s a pretty awesome substance, one that’s been around for some time from what I can gather, as it emulates the properties of wet sand pretty well without requiring water. I haven’t been able to track down the exact polymer that they use (confusingly the hydrophobic sand I blogged about also carries the name moon sand) but it seems a workable substitute can be made with good old fashioned corn starch. That does require water however which leads me to believe that the polymer they use has some non-Newtonian properties to it as that’s exactly what you get when you mix corn starch and water. If I could find the exact polymer they’re using (searching for non-toxic non-Newtonian polymers didn’t give me any viable leads) so if you happen to know what it is I’d be keen to hear from you.
One of the interesting points that came up in my research to this is people wondering whether or not this would be anything like real moon sand. Strangely enough the surface of the moon is coated in a layer of what you could classify as sand but it’s formed quite differently and it’s called regolith. Sand on earth is made by rock being slowly eroded away, typically by some form of moving water. Regolith on the other hand has rather violent origins with its primary mode of creation being through impacts on the surface by meteors. That’s why you don’t have regolith on earth as the amount of impacts required to generate it simply don’t happen (thankfully) due to our atmosphere. The moon on the other hand isn’t so lucky and gets bombarded constantly with generates the layer of dust upon it.
However that regolith isn’t composed of worn particles like sand is, instead the base structures are typically jagged and this actually became an issue with the early sample return missions to the moon. Those jagged particles stick to everything they and actually punctured the vacuum membrane on the sample return jars, contaminating them. More interesting still is that regolith appears to be highly reactive as Armstrong and Aldrin (and many other astronauts) reported smelling gunpowder after completing their moon walks something that wasn’t reported by scientists studying the samples back home. Moon Sand by comparison is quite inert and not at all abrasive.
Now I just need an excuse to buy some of this. I mean it’d be completely normal for a near 30 year old to do this, right?