New materials, composites, semiconducting, porous, crystalline, amorphous materials for solar energy conversion seem to feature regularly in the daily scientific news feeds this writer reads every day. Indeed, I've written about many of the developments over the last two-decades-plus as a science writer. From the latest development in shiny silicon to organic alternatives that hope to outlast them and offer flexibility to boot.
A couple of points that arise are that you need a high enough voltage together with a high enough current to give you a high enough power. Wattage being the product of voltage and ampage, of course. Unfortunately, neither current nor voltage is commonly high even under the most intense direct, overhead sunlight and the efficiencies of many of the experimental materials being developed as photovoltaics are never particularly efficient. After all, even the best, most pristine devices are pushing it to extract an efficiency of more than a few percent. Cutting edge research is talking about absolute efficiencies of 20 %, but realistically offering something around 15 %.
Here's a quick grab-bag of this cutting edge solar headlines I clutched at from a few of the news wire services:
"Photovoltaics among fastest growing industries in the world", "Novel technique to synthesize nanocrystals that harvest solar energy", "NIST measurement advance could speed innovation in solar devices", "Researchers Develop New Low Cost, High Efficiency Solar Technology", "New Solar Panels Made with More Common Metals Could Be Cheaper and More Sustainable". There are many, many more and all presumably very worthy in their efforts. However, there is a niggle, isn't there, when it comes
I remember discussing with Cambridge University chemist Jeremy Sanders, a novel supramolecular compound on which his team were working, back in the early 1990s. I even wrote about this wheel of steroidal molecules for New Scientist's technology news pages. This was fundamental chemical science, but there were hints that such materials might be able to trap solar photons and pass them along a chemical chain to release electrons. They could act like the photosynthetic antennae in the chloroplasts of green leaves. Ultimately, I thought they might be incorporated into a photovoltaic-type device and be used to generate electricity.
Sanders' team may have mentioned such distant but fairly plausible applications in their grant proposals and even in the introduction to their research paper on these compounds, but it was Sanders too that pointed out a fundamental truism of trapping solar energy that in some ways casts a shadow on certain aspects of the whole quest to find better materials. The fact is that for plants solar energy conversion is all about making food, for us it's about generating electricity, but it is currently a major headache to find ways to store electricity that simply don't cancel out many of the benefits of using a sustainable approach to generation like solar.
Moreover, as Sanders told me all those years ago, using the warmth of the sun as a heat source, for heating water is always going to be more efficient. Although solar electricity may be focused on charging up laptops and running TVs it's bizarre that there are some settings in which it is even used to supply power to electrical heating elements to warm water. Instead of encrusting the roofs of our homes with expensive and fragile silicon panels or even hankering after their flexible organic counterparts, maybe the focus should have been on cutting that biggest of energy hogs, water heating, by developing systems that can capture the sun's infra-red energy directly and cut out that electron chain.
David Bradley blogs at http://www.sciencebase.com and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".