Solar Tarp – foldable, portable solar power.

California based Lipomi Research Group are working on creating a solar tarp – which would have myriad uses for society. Let’s learn more about how these upgraded solar panels could help parts of the world where they don’t have access to regular electricity – and some of the technological challenges they’re facing trying to complete the project.

About the Solar Tarp technology

Prototype Solar Tarp Sample - University of California
Prototype Solar Tarp Sample – University of California (source: theconversation.com)

The Lipomi Research Group are focused on “identifying ways to create materials with both good semiconducting properties and the durability plastics are known for – whether flexible or not”.  They’ve been tinkering with perovskite solar cells, which are 1/1000 the thickness of a silicon layer in a solar panel. 

Darren Lipomi of the Lipomi Group, who is also a Professor of Nanoengineering at the University of California, said that their goal is to create flexible solar panels which are as efficient as conventional silicon but don’t have some of the drawbacks of it.

The goal is to develop flexible solar panels which are thin, lightweight, and bendable. Lipomi is calling their idea a ‘solar tarp’ – which refers to a solar panel which can be expanded to the ‘size of a room’, but balled up to the size of a grapefruit when not in use. The issues here are finding a molecular structure to make the solar panels stretchable and tough – this involves replacing the silicon semiconductors with materials such as perovskite. 

They’re also taking a look at polymer semiconductors / organic semiconductors (based on carbon, and used in place of perovskites or silicon in a solar cell). These aren’t as efficient, but are far more flexible and extremely durable.

According to The Conversation, the sunlight that hits the earth in a single hour contains more energy than the whole planet uses in an entire year – so there’s plenty more work to do on improving how we utilise the sun! We’ll keep an eye on the solar tarp project and let you know when it reaches the next stage.

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Perovskite Solar Panels Rolled Out (Saule/Skanska)

Poland based Saule Technologies have signed a distribution agreement with the Skanska group to roll out perovskite solar panels in 2018. This is the first company to bring the technology to market and it’s an exciting step forward for alternatives to the efficiency limited (read about the Shockley-Queisser limit) conventional silicon based solar panels.

Saule Technologies and Perovskite Solar Panels

Perovskite Solar Panels - Saule Technologies and Skanska Group in Poland
Perovskite Solar Panels – Saule Technologies and Skanska Group in Poland (source: skanska.pl)

We’ve previously written about research into perovskite solar cells and Greatcell’s $6m grant towards Perovskite Solar Cell research. But this is the first time they’ve been offered to the public – so it’s a huge step forward for the technology.

Saule Technologies are a Warsaw based start-up who will partner with multinational project development and construction firm Skanska AB to bring the semi-transparent perovskite solar modules to commercial office buildings. According to PV Tech, the first panels will be installed on office buildings in Poland later this year. 

On a press release on their website, Skanska said they have over €20 million in grants for their research and are currently building large-scale, prototype production line. They have been “working on the application of ink-jet printing for fabricating free-form perovskite solar modules since 2014”, so it’s exciting to see their research enter the next phase. 

“It is not a science-fiction vision anymore. Working with talented scientists from Saule, we are now turning fiction into reality and creating buildings which are more energy efficient and carbon neutral. Up to now this has not been possible on a large scale. Climate change is one of the biggest challenges the modern world is facing and it contributes to extreme weather events that are increasing in frequency and severity around the world. As such there is increasing legislative pressure to run businesses in a sustainable and attentive manner,” said Katarzyna Zawodna, CEO of Skanska’s commercial development business in CEE.

View the video below to learn more about manufacturing perovskite solar panels and the ink-jet printing/crystallization process:

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Perovskite Solar Cell Efficiency

Perovskite solar cell research is continuing at a fantastic rate, with the March issue of academic journal Science reporting that a collaboration between UNIST (Ulsan National Institute of Science and Technology) and the Korean Research Institute of Chemical Technology (KRICT) was able to reach 21.2% efficiency with a hybrid organic/inorganic perovskite solar cell.

Perovskite (wiki), a raw material which can be used to harvest solar energy and can be combined with liquid solutions to allow broad application (i.e. the conventional rigid shape of the solar panel could be superseded by something like a ‘spray’ application of a perovskite-based solution), is paving the way for solar technology. Researchers at the ANU (Australian National University) have achieved 26.4% efficiency using a stacked configuration of silicon and perovskite solar cells. The Duong from ANU’s Research School of Engineering heralded the achievement as ‘…a step closer to a low-cost alternative (to silicon based cells)’. It’s important to note that this efficiency was created ANU’s cell size was 0.18cm² (a research size – far from commercially viable). UNSW achieved 12% efficiency for a ‘full size’ 16cm² solar cell last December. Solliance, a Dutch/German/Belgian R&D team, achieved 12.6% in R2R (roll to roll) perovskite solar cells in March.

Perovskite Solar
Perovskite (image: Wikipedia.com)

Although still a far way from the 26.3% efficiency achieved by the Kaneka Corporation using silicon solar panels, it’s important to note that due to the Shockley-Queisser limit silicon panels will never reach greater than 1/3 efficiency. Using perovskite to manufacture solar cells could potentially double this limit – with the added bonus of being inexpensive and using less energy to manufacture. The hybrid organic/inorganic perovskite solar cell discussed at the start of this article (iodine/lead/methyl-ammonium crystalline structure) boosts the efficiency of the panel so that it can carry 2/3 of the energy from light without losing so much to heat.

The fact that this compound can also be applied through myriad techniques such as spraying, dipping, printing, and doctor-blading means that it has a much wider range of application. ‘Solar cells are no longer limited to rigid structures such as panels’, says Dr Anita Ho-baillie, head of Perovskite Solar Cell Research at the Australian Centre for Advanced Photovoltaics (ACAP) at UNSW.

Perovskite’s potential in terms of solar cells was first discovered by Japanese researchers in 2006 and Dr Ho-Baillie says she thinks perovskite solar cell efficiency will be able to reach 24% by the end of the year. There’s still a long way to go for perovskite to surpass silicon as the material of choice for solar cells, but progress is steady and as soon as they break the ‘magical’ 30% barrier it’ll become the material of choice for solar panels, if not before.

 

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Kaneka Corporation create Solar Cell with record-breaking 26.3% efficiency.

Japanese chemical manufacturer Kaneka Corporation have created a solar cell with 26.3% photo conversion rate, a 2.7% efficiency increase on the previous record of 25.6%. This may not seem like much but it’s a little more impressive when you note that silicon based solar cells are currently thought to have a ‘theoretical limit’ for energy conversion. This means that no matter how good technology becomes, silcon will never break 29% – i.e. we’re starting to get closer to the ‘end-game’ of our optimisation of silicon solar cells (and need to start looking at alternatives, which is happening).

The technology was funded by a Japanese government program and develops “industrially compaible cells” by implementing layered silicon inside individual cells to minimise band gaps – this approach is called thin-film hetereojunction (HJ) optimisation. It’s not pioneered by Kaneka, but they have managed to optimise the technique by using low resistance electrodes at the rear of the cell and amorphous silicon with an anti-reflective layer on the top.

Kaneka Corporation Solar
Side view of a solar panel using layers of silicon through HJ (thin-film heterojunction) (courtesy of Kaneka Corporation)

The Kaneka Corporation, based in Osaka, haven’t begun mass production of the panel yet but we’ll be sure to let you know as soon as they’re available. The researchers, led by Mr Kunta Yoshikawa, published their findings in Nature Energy and noted that “further work is required before the individual cells can be assembled into a commercially available solar panel.”

26.3% isn’t the greatest photo conversion rate we’ve achieved but it is, to date, the highest commercially feasible result. In terms of theoretical results, back in 2014 researchers from UNSW Engineering managed to crack 40% by using a ‘solar tower’ with an optical bandpass filter.

In other news there has been a significant breakthrough – also at UNSW – with regards to high performance perovskite solar cells. Read our article on that to see how we could push solar technology further by using perovskite ‘liquid solar cells’ – one of the top 10 emerging technologies of 2016 (as per World Economic Forum)

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