Sparks

Turning wine into electricity

 By Eniday Staff

Generating electricity from lees, the deposit that forms when wine is fermented… On the face of it, it sounds like something out of a tutorial for over-imaginative DIY fans. But it’s actually a serious thing; serious enough to deserve an official presentation at Vinitaly last year…

CHEERS, a project to produce innovative photovoltaic cells, was started by Ca’ Foscari University of Venice, the universities of Udine and Malaga and the company Vinicola Serena, one of the biggest wine producers in the Conegliano area of the Veneto. The cells in question are DSSC (dye-sensitised solar cells), also known as Grätzel cells after their German inventor, who first crafted them in the laboratories of the University of Lausanne. They work by imitating in part the mechanism of photosynthesis.
The base material is a special dye that is sensitive to light and comes from complex natural processes. There are thousands of these photosensitive organic dyes existing in nature, some of them in fruit, above all berries and grapes.
Grätzel cells work differently from traditional silicon ones. In those, to summarise very briefly, the photons cause electric charges to separate within the silicon crystal, suitably dosed with other atoms, and thereby generate a flow of electrons. This is how electricity is produced using the photovoltaic effect.
In the case of organic cells, by contrast, the basis is a surface made of transparent, conductive material, on top of which a very fine layer of titanium oxide nanocrystals is placed, itself covered by a photosensitive dye. Without getting into a technical explanation of what the cell is made up of, in simple terms, when light hits the molecules in the dye, they send out electrons to the titanium oxide layer, which in turn sends out electrons to the conductive glass below. To obtain electricity, all you have to do is collect the flow of electrons.

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Structure of a dye sensitized photovoltaic cell (Maslisko, Wikimedia)

Simple… and complicated

But why then have these solar cells not been used for other things? It’s due to their efficiency levels and to choosing the most suitable materials. Let’s look at the second reason first. The plant kingdom is full of photosensitive dyes. You’ll find them in every fruit, every flower and every leaf. They vary in amount, concentration and easiness to extract in useful quantities. The task is in fact so complicated as to require the use of large mainframes designed for artificial intelligence. American and British researchers at the Argonne National Laboratory and Cambridge University, respectively, are grappling with this challenge. After selecting 10,000 potential substances for catching light energy, or photon catchers, they simulated the extraction process for each of these, using the conductive glass and titanium oxide. They put all the data into the calculation and modelling systems, which resulted in a small group of the best materials in terms of absorbing light energy and practical use. The best among these were the pigments taken from wine lees, which are available in large quantities, and berries, which are far less common than vines.

Efficiency is the other reason why it is difficult to use Grätzel cells more widely. Surfaces exposed to both artificial light and sunlight being equal, a silicon cell generates dozens of times more energy than a Grätzel one. When the Sun is covered, however, the comparison is almost inverted and the Grätzel is able to generate far more energy than the silicon. And that’s not all. Cells built on organic pigments can also be used to store energy, albeit indirectly and counterintuitively. If exposed to artificial light, at certain frequencies, Grätzels still produce electricity. This means at least some of the electricity used for public and domestic lighting could be recovered. And all this from the residues that come from producing the noblest of drinks. In this case, it’s fair to say that “nothing gets thrown away”!

READ MORE: Tailor made solar panels by Luca Longo

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Eniday Staff