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Solar light. The autonomous energy

The sun bathes the Earth every day with enormous amounts of energy, an energy that will not be exhausted as long as our star lives and when that occur nor you or I will be around to grumble about it. 

If we have any real advantage in south of Spain of having a sun drenched land without much water, is that we could store that energy and convert it into the most useful energy of all “electricity”.

The sun bathes the Earth every day with enormous amounts of energy, an energy that will not be exhausted as long as our star lives and when that occur nor you or I will be around to grumble about it.

A small part of this energy feeds life on our planet, but the vast majority returns to space, unused. However, we have started to harvest the sun's rays and to generate electricity, although using only a tiny fraction of the energy that our beloved star gives us every day.

 

 

Here in this part of Spain we are fortunate that we blessed with a good proportion of that clean energy. Energy that if we could use it more efficiently, our economy would change radically: society would no longer depend on finite energy sources concentrated in the hands of a few. It could also reduce the emission of greenhouse gases, and therefore mitigate climate change.

That is why sun energy is an autonomous energy, a democratic energy. An energy that could liberate us from the monopoly of a few.

 

But…

The problem, is that current technologies to capture the sun's rays are very inefficient: the typical commercial solar panels, made of silicon, are only capable of transforming into electricity less than a quarter of the energy that reaches them. The rest is wasted into heat and is not absorbed. And to generate enough energy, huge amounts of purified silicon are needed, which is not exactly economical, installing solar panels on a roof can cost several thousand euros and will take several years to pay for itself; At these prices, like for alike fossil fuels are still cheaper.

 

To convert solar energy into a competitive source and really available to all, scientists are managing to find alternatives to silicon: photovoltaic materials designed from scratch to be highly efficient in capturing the sun's rays. Most efforts are focused on so-called thin film technologies, solar cells that measure from nanometres to a few micrometres (between a million and a thousand times finer than a millimetre). The idea is that, being so thin, the amount of material used is so tiny that its cost is very economical.

 

The Perovskite solar panel.

They are the material that has awakened most hopes, due to the rapid increase in efficiency (ICIQ) according to the latest research carried out in the Institute of Photonic Science in Castelldefels in Catalonia.

Of these new technologies, those that have roused most hopes are the so-called perovskites. They are a hybrid material, formed by lead, iodine and an organic molecule. Its photovoltaic properties were discovered in 2012 and, since then, in a frenetic race of less than six years to which hundreds of scientists have joined all over the world, have practically managed to equal silicon in efficiency, with a record of 22%. And in less than five years they will get over it.

In less than six years, the efficiency of the perovskites has practically reached that of silicon

The materials and manufacturing process of this type of cells are very economical, but present a serious drawback: the perovskites are soluble in water. And they contain lead, which is highly toxic. If they were used in solar panels at their current development point, they could cause a huge environmental disaster, that is why research is being done to replace lead with another more innocuous element, although for the moment there has been no success.

They also have another problem: they are very unstable and degrade shortly after they start to work, so there is still a long way to go before they become a reality in the photovoltaic market.

 

Integration = economical solar system.

The thin-film solar cells are light and flexible, which will allow them to be integrated in surfaces such as clothes or building materials (IREC)

More secure and stable, although less efficient at the moment, are the so-called kesteritas. They are a totally inorganic material, made of very abundant elements in the earth's crust (containing copper, tin zinc and sulphur or selenium), economical and sustainable to extract, another thin film technology that is already commercially available, but which "contains very rare and precious metals (indium and gallium, which are used to make flat screens), so it cannot be manufactured in mass, While CIGS has a record efficiency of around 22%, the much more recent Kesterites are still just over 12%, according to the National Renewable Energy Laboratory (NREL) of the United States.

 

However, although they do not reach the efficiency of conventional silicon, whose efficiency record has been stagnant for 25% for decades, thin film technologies offer other advantages. The cells are so thin that they weigh very little and are also flexible. That would allow integrating them in buildings, for example, in the form of solar tiles. Also in textile substrates, The idea would be in the future to have most exterior surfaces or even our own clothes capable of recharging batteries of a mobile phone while having a walk in the sun.



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