Sunday, 11 January 2015

Two new records may mean solar is ready to topple fossil fuels

Over the last 20 years or so, renewable technology has come on leaps and bounds. However it is still not quite competitive enough to become more economically viable than fossil fuels. The US Department of Energy has estimated that solar panels will need to cost about 50 cents per watt to be able to compete with fossil fuels, it currently averages at about 75 cents per watt. Although other countries, such as Spain have actually already reached the point where solar is cheaper than fossil fuels (although the plummeting oil price may have reversed this situation). For more background I wrote this article explaining a little more about what the future holds for green energy in general.

Records for solar panel efficiency are broken on a regular basis by various research institutes and have increased from about 20% in 1989 to over 40% and climbing. The solar panels on NASA satellites for example work at about 45%, however these are terribly expensive and most household solar panels get between 15-18% efficiency but you can get high end ones that reach about 30%, But two very recently broken record stands out from amongst the others.

The first of which was broken in October 2014 by the University of New South Wales when they made commercial solar panels that reached 46% efficiency even under normal conditions. This was done by using 3 panels collecting light energy at different wavelengths and then the spare light energy was directed towards a fourth panel that absorbed some of the previously unused light. This type of set up is compatible with the types of solar power plants that are starting to come online in places like the Mojave Desert.

The Ivanpah Solar Plant in the Mojave Desert could power up to 140,000 homes

The second record was also broken in October and was published in Nature last week. It could be argued that this record is more important than the first. This record is for the highest efficiency recorded for a type of low-cost solar cells called Perovskite. This new way of making solar cells involves spraying a pigment onto a sheet of glass or metal foil, along with other materials to help improve efficiency. These were first used in 2009 and only had about 3.5% efficiency. Not much really came from this new type of solar cell until the end of 2012, where efficiencies began to increase rapidly. This most recent record sets the efficiency to 20.1% and an average of 18.4% (similar to the average solar cells on most households today). they achieved this by blending one of the more commonly used materials (methylammounium lead bromide) with the more unstable, but potentially more efficient, formamidinium lead iodide. The researchers at the Korea Institute of Chemical Technology used this blend to increase the range of wavelengths that these Perovskite cells can absorb and thus improve its efficiency. 

Perovskite cells have rapidly improved in efficiency and rocketed towards comparable performance with typical silicon (green), dye-sensitised (blue) and organic (grey) solar cells

This could lead to commercial solar panels that can produce energy at about 10-25 cents per watt, less than half the calculated price necessary for it to compete with fossil fuels. Additionally, because the Perovskite cells are sprayed onto another material, it could be used to augment traditional solar panels in order to boost their efficiency and thus reduce their running cost (which may encourage more people to adopt the technology if they think there might be a better panel coming out soon). The main advantage for this technology is that it is fairly cheap and simple to produce, and would be easily scalable. 

One potential pitfall would be the use of small quantities of lead, which would have to be shown to not be too toxic. collecting and recycling systems would also have to be introduced to prevent the leakage of lead into the environment, which shouldn't be too problematic as other schemes are in place for things like lead-acid start batteries in cars etc. 

This is happily followed by the news yesterday that Diesol and Nesli DSC have launched a joint venture to start commercial production of Perovskite solar cells by 2018. The future sure does look bright for solar!


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