Dummy's guide to spray-on solar cells
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Perovskites. They've been generating a LOT of buzz in the solar industry. The World Economic Forum has hailed them as one of the world’s most exciting technologies. Scientists are using it to develop “revolutionary” solar materials. But what exactly is this exotic-sounding material? And is spray-on solar a real thing? Read on to find out.
We live in a world where solar pioneer Frank Shuman’s vision is coming to fruition. Solar energy is rapidly becoming commercially viable and sometimes even cheaper than non-renewable power sources. Countries like Germany and Iceland have announced deadlines for transitioning to 100% renewable energy.
The existing silicon-based photovoltaic cells have played a big part in the rise and rise of the solar industry and they will keep having a big role to play. But cutting-edge solar technologies like perovskite solar cells are tipped to take solar power to the next level.
Named after the Russian mineralogist ‘Lev Perovski,’ perovskite is a calcium titanium oxide mineral. It is rarely found in nature, but perovskite can be made by combining easily available elements.
Perovskites were first discovered in 1839. But it was only 10 years ago, in 2009, that a research team in Japan announced the first-ever application of perovskite for producing solar cells.
A solar cell, as you are probably aware, uses the photovoltaic effect to convert sunlight into electricity using a semiconducting material. For decades, the solar industry has relied on silicon to produce this effect. The perovskite solar cell, on the other hand, uses perovskite as the semiconducting material.
The switch from using silicon to perovskite may not sound like a big change, but it actually has the potential to have a transformative effect on the solar industry. Read on to find out how.
There are certain distinct qualities that make a perovskite solar cell special.
When perovskite was first used to make a solar cell in Japan, it was highly unstable and had a power conversion efficiency of 3.8%. Recently, OxfordPV a leading researcher and manufacturer of perovskite solar cells, has built cells that can reach an efficiency of 28%.
This incredible increase took only 10 years. To put things in perspective, the standard silicon solar cells reached 6% efficiency in 1954 and a peak efficiency of 25.6% in 2014. That took 70 years and there is little room for the efficiency of silicon solar cells to grow further. On the other hand, these are still early days when it comes to realizing the full potential of Perovskite solar cells.
Solar cells made with silicon, used in 90% of all solar panels, are hard to manufacture.
“Silicon has to be pure and perfect to have the characteristics we covet,” says Joseph Berry, a senior scientist at NREL, in an interview to Spectrum. “One of my colleagues likes to say that if you were looking for the ideal material for solar, you would never pick silicon,” says Berry.
On the other hand, perovskites are what you could call ‘defect tolerant.’ The material does not need extreme care when manufactured.
The ‘defect tolerant’ characteristics make it possible for perovskites to be manufactured through various low-cost methods. This results in a drastic reduction in production costs.
Joseph Berry of NREL predicts the cost of production for perovskite solar cells could be 10 times lower than the cost of making standard solar panels.
Not only is it more efficient and cheaper to manufacture, but the perovskite crystal structure is also highly flexible, lightweight and semi-transparent. These qualities exponentially add to the possible ways in which perovskite cells can be used in the future.
Transparent and flexible solar cells that can be used as window glazing, painted on walls or spray coated over almost anything. This right here is science fiction becoming reality in front of our eyes.
But of all possible applications of flexible perovskite material, spray-on solar cells is the most promising.
They are exactly what they sound like: perovskite solar cells that can be sprayed on to a surface. These perovskite cells are in their liquid form allowing them to be sprayed on to a surface, hence: spray-on solar cells.
This process of spraying solar cells on to a surface has been talked about in the scientific community for many years. But it has seen real-world application in just the last few years.
The first ever spray-on solar cell was developed at the University of Sheffield in 2014. A perovskite-based mixture was sprayed and spread to form a sun-harnessing layer.
As exciting as this sounds, we can’t start spraying roofs and cars with perovskite cells just yet. The technology is still in its nascent stages.
The first practical applications of spray-on solar might be to produce sheets of solar panels with solar cells sprayed on them. The spray-painting process wastes very little material and can be scaled to high-volume manufacturing — similar to graphics printing.
The spray-on solar cells developed by the University of Sheffield have achieved an efficiency of 11%. That’s still well behind silicon solar cells, which can reach up to 25% efficiency.
For perovskite technology to become viable, the efficiency of the cells needs to increase.
As with most early technologies, perovskite cells and spray-on solar face many challenges at this stage.
One big problem with current perovskite cells is that they are not made of fully disposable materials. Perovskite contains a small amount of lead. Although only a small amount, it makes them less than ideal for the environment.
Non-toxic, organic forms of perovskites are being experimented with and some have shown potential to replace lead entirely.
Another disadvantage of perovskite solar cells is their durability. It simply isn't as strong or long-lasting as the traditional silicon solar technology.
The characteristics which give perovskite their flexibility also hinders them. Perovskite cells are soluble, hence they are likely to wear down much more quickly than more solid silicon material.
For now, these drawbacks will hinder any large scale adoption of the perovskite solar cells. It’ll be interesting to see how long it takes researchers to find the necessary solutions
The scientific community has taken note of the powerful possibilities that the perovskite solar cells represent. In 2016, the World Economic Forum named perovskite cells as one of its top 10 emerging technologies.
Perovskite solar cells are likely to revolutionize solar energy generation by providing a cheap and flexible source of producing clean energy.
But the technology will take time to mature and overcome its current functional drawbacks.
Presently, you can maximize your savings and help the environment by installing standard silicon solar panels. With the 26% federal tax credit, and net metering available in most states, getting solar panels installed for residential and business properties currently offers a great return on investment. You can always upgrade your solar systems with perovskite solar cells when they become commercially available.
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