New solar cells offer you the chance to print out solar panels and stick them on your roof

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This roof in Newcastle has become the first in Australia to be covered with specially printed solar cells.
University of Newcastle, Author provided

Paul Dastoor, University of Newcastle

Australia’s first commercial installation of printed solar cells, made using specialised semiconducting inks and printed using a conventional reel-to-reel printer, has been installed on a factory roof in Newcastle.

The 200 square metre array was installed in just one day by a team of five people. No other energy solution is as lightweight, as quick to manufacture, or as easy to install on this scale.

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Our research team manufactured the solar modules using standard printing techniques; in fact, the machine that we use typically makes wine labels. Each solar cell consists of several individual layers printed on top of each other, which are then connected in series to form a bank of cells. These cells are then connected in parallel to form a solar module.

Since 1996, we have progressed from making tiny, millimetre-sized solar cells to the first commercial installation. In the latest installation each module is ten metres long and sandwiched between two layers of recyclable plastic.

At the core of the technology are the specialised semiconducting polymer-based inks that we have developed. This group of materials has fundamentally altered our ability to build electronic devices; replacing hard, rigid, glass-like materials such as silicon with flexible inks and paints that can be printed or coated over vast areas at extremely low cost.

As a result, these modules cost less than A$10 per square metre when manufactured at scale. This means it would take only 2-3 years to become cost-competitive with other technologies, even at efficiencies of only 2-3%.

These printed solar modules could conceivably be installed onto any roof or structure using simple adhesive tape and connected to wires using simple press-studs. The new installation at Newcastle is an important milestone on the path towards commercialisation of the technology – we will spend the next six months testing its performance and durability before removing and recycling the materials.

The solar cells can be installed with little more than sticky tape.
University of Newcastle, Author provided

We think this technology has enormous potential. Obviously our technology is still at the trial stage, but our vision is a world in which every building in every city in every country has printed solar cells generating low-cost sustainable energy for everyone. This latest installation has brought the goal of solar roofs, walls and windows a step closer.

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Ultimately, we imagine that these solar cells could even benefit those people who don’t own or have access to roof space. People who live in apartment complexes, for example, could potentially sign up to a plan that lets them pay to access the power generated by cells installed by the building’s owner or body corporate, and need never necessarily “own” the infrastructure outright.

But in a fractured and uncertain energy policy landscape, this new technology is a clear illustration of the value of taking power into one’s own hands.The Conversation

Paul Dastoor, Professor, School of Mathematical and Physical Sciences, University of Newcastle

This article was originally published on The Conversation. Read the original article.


Semitransparent solar cells: a window to the future?

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Looking through semitransparent cells – one day these could be big enough to make windows.
UNSW, Author provided

Matthew Wright, UNSW and Mushfika Baishakhi Upama, UNSW

Can you see a window as you are reading this article?

Windows have been ubiquitous in society for centuries, filling our homes and workplaces with natural light. But what if they could also generate electricity? What if your humble window could help charge your phone, or boil your kettle?

With between 5 billion and 7 billion square metres of glass surface in the United States alone, solar windows would offer a great way to harness the Sun’s energy. Our research represents a step toward this goal, by showing how to make solar panels that still let through enough light to function as a window.

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The economics of renewable energy are becoming increasingly favourable. In Australia, and many other parts of the world, silicon solar cells already dominate the rooftop market.
Rooftop solar power offers an increasingly cheap and efficient way to generate electricity.

But while great for roofs, these silicon modules are opaque and bulky. To design a solar cell suitable for windows, we have to think outside the box.

When we put a solar panel on a roof, we want it to absorb as much sunlight as possible, so that it can generate the maximum amount of power. For a window, there is inevitably a trade-off between absorbing light to turn into electricity, and transmitting light so we can still see through the window.

When thinking about a cell that could be fitted to a window, one of the key parameters is known as the average visible transmittance (AVT). This is the percentage of visible light (as opposed to other wavelengths, like infrared or ultraviolet) hitting the window that travels through it and emerges on the other side.

Semitransparent solar cells convert some sunlight into electricity, while also allowing some light to pass through.
Author provided

Of course we don’t want the solar window to absorb so much light that we can longer see out of it. Nor do we want it to let so much light through that it hardly generates any solar power. So scientists have been trying to find a happy medium between high electrical efficiency and a high AVT.

A matter of voltage

An AVT of 25% is generally considered a benchmark for solar windows. But letting a quarter of the light travel through the solar cell makes it hard to generate a lot of current, which is why the efficiency of semitransparent cells has so far been low.

But note that electrical power depends on two factors: current and voltage. In our recent research, we decided to focus on upping the voltage. We carefully selected new organic absorber materials that have been shown to produce high voltage in non-transparent cells.

When placed in a semitransparent solar cell, the voltage was also high, as it was not significantly lowered by the large amount of transmitted light. And so, although the current was lowered, compared to opaque cells, the higher voltage allowed us to achieve a higher efficiency than previous semitransparent cells.

Having got this far, the key question is: what would windows look like if they were made of our new semitransparent cells?

Do you see what I see?

If your friend is wearing a red shirt, when you view them through a window, their shirt should appear red. That seems obvious, as it will definitely be the case for a glass window.

But because semitransparent solar cells absorb some of the light we see in the visible spectrum, we need to think more carefully about this colour-rendering property. We can measure how well the cell can accurately present an image by calculating what’s called the colour rendering index, or CRI. Our investigation showed that changing the thickness of the absorbing layer can not only affect the electrical power the cell can produce, but also changes its ability to depict colours accurately.

A different prospective approach, which can lead to excellent CRIs, is to replace the organic absorber material with one that absorbs energy from the sun outside the visible range. This means the cell will appear as normal glass to the human eye, as the solar conversion is happening in the infrared range.

However, this places limitations on the efficiency the cells can achieve as it severely limits the amount of power from the sun that can be converted to electricity.

What next?

So far we have created our cells only at a small, prototype scale. There are still several hurdles in the way before we can make large, efficient solar windows. In particular, the transparent electrodes used to collect charge from these cells can be brittle and contain rare elements, such as indium.

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Solar power alone won’t solve energy or climate needs

If science can solve these issues, the large-scale deployment of solar-powered windows could help to bolster the amount of electricity being produced by renewable technologies.

The ConversationSo while solar windows are not yet in full view, we are getting close enough to glimpse them.

Matthew Wright, Postdoctoral Researcher in Photovoltaic Engineering, UNSW and Mushfika Baishakhi Upama, PhD student [Photovoltaics & Renewable Energy Engineering], UNSW

This article was originally published on The Conversation. Read the original article.