The Future of Solar Power
Posted by Science Oxford on May 23, 2011 | comments
A talk and workshop at Science Oxford Live by Lucy Moorcraft and Michael Brown from theSolarSpark.co.uk (review written by Blanka Sengerová)
On 19th May, the lecture room at Science Oxford Live turned into a workshop producing solar powered cells, with much enthusiasm throughout the room.
But first, Lucy of The Solar Spark (1) and Michael of the University of Oxford told us about the new discoveries in the field of making solar powered cells.
Did you know that a Roman emperor, in the olden days, might have had more than 100 slaves to ensure his continued wellbeing and high maintenance lifestyle? How many slaves pedalling in the garage on exercise bikes connected to a generator would it take to maintain the lifestyle of an average UK person today? Remember, you need someone to power all the light-bulbs, the heating, cooker, all the appliances, even the computer you’re now reading this on… Well, it turns out that to maintain our lifestyle, we’d also need over a hundred pedalling people, similar to the number that the Roman emperor would once have had waiting on him…
But of course we don’t have people pedalling for us in the garage; instead we get much of our energy from fossil fuels such as oil and coal. Yet, as you will likely be aware, there are some major problems with using fossil fuels to power our world. One of them is global warming that occurs due to the release of carbon dioxide when burning fossil fuels. Incidentally, the idea that global warming is happening is not new, it has been around for over a hundred years, first proposed by the chemist Arrhenius in 1896. A second problem is the security of our energy – with a large amount of fossil fuels found in the rather volatile Middle East, it is not always easy to be certain that the UK (and other countries) will have access to them. And finally, importantly, once the fossil fuels are gone, they’re gone – our current level of fossil fuel use is equivalent to spending your entire year’s salary in 30 seconds and then having nothing left!
So this is why scientists’ focus has turned towards renewable sources of energy (wind, hydroelectric, geothermal, solar) as a possible solution to the fossil fuel problem. Indeed, if you could use the energy with 100% efficiency, only 10 minutes of the sun’s energy reaching the earth is sufficient to cover one human’s energy use per year. So how does solar power work?
One of the basic solar power applications is the solar heating cell. This is where cold water flows into your cell, is heated up by the solar panel and flows out as hot water, and it is connected to water tanks in central heating systems. The more complex applications involve photovoltaic cells. This is where the solar cell, which is where the sun’s rays are caught, is connected to an electric circuit. In a very very simplified manner, the energy from the sunlight hits the solar cell, which causes electrons to start flowing round the circuit, leading to an electric current. Voilà!
Currently, solar cells are made from silicon, which is highly efficient and very stable but there are some manufacturing issues with it. The cells have to be made in a clean room, increasing production costs and the silicon has to be purified from sand, which requires high temperature. Apart from that, some of the components of currently available solar cells, such as cadmium telluride, are highly toxic. To deal with these, given the increased demand for solar power, new technologies are being developed as we speak. One of these, currently in prototype format, uses titanium dioxide together with polymers and ruthenium dyes to provide a cell which is non toxic, low cost, lightweight and flexible (because it is printed onto a sheet).
In terms of its reduced cost and increased durability (and flexibility), the new technology has potential to make solar power accessible to the third world where it is really sunny (always a plus for solar power!) and where electricity is still not routinely accessible to many people. You can imagine how the solar powered electricity could be used in water purifiers, in refrigerators to store medicines safely, to allow children to read and write into the evening to increase literacy, to improve farming methods and in many many other places. Not only would solar power be beneficial to the developing world, but it can be used by us in the Western world too – Lucy went on to show us examples of how this has been done already with remote controls that don’t need AA batteries and are just left on the windowsill to charge, personal music players charged by sunlight, road signals, and many more.
As the audience waited excitedly for the practical part of the session, Michael, a PhD student working on developing new solar cells, explained his work to us. He works on dye sensitised solar cells. This means that in the solar cell, there is a dye which absorbs the sunlight. The absorption is accompanied by an excitation of the molecule, and it is this excited state of the dye molecule that allows electrons to start flowing round a circuit, leading to current. In a less high-tech manner, this is what we were going to build using a straw, filled with a soldering wire coil and raspberry juice (for the dye), and quite a few other bits and pieces (2). The explanation for how this works can be found on the Solar Spark website (3), and we did manage to power up a calculator using our battery!
Overall, a very enthusiastic pair of speakers (Lucy is soon to be a teacher, so rather unsurprisingly she was very good at explaining the basics) and a very interesting practical sessions – you could see how very absorbed the entire audience got!
1 The Solar Spark website: http://www.thesolarspark.co.uk/
2 How did we make the solar cell in a drinking straw: http://www.thesolarspark.co.uk/teachers/downloads/SolarCellStrawsInstructions.pdf
3 And this is the theory behind the experiment: http://www.thesolarspark.co.uk/teachers/downloads/SolarCellStrawsNotes.pdf
What do you think?