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Asked by Sharkhead to Jackie, Michele, Oliver, Yelong on 19 Mar 2015.
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Oliver Brown answered on 19 Mar 2015:
A little research suggests that the most efficient method is a hydro turbine (a.k.a. a ‘water-wheel’) which can be 85-90% efficient! Next in field is a particular type of gas turbine which can hit 60% in perfect conditions , otherwise everything apart from solar is somewhere between 35-40% efficient. Solar’s at the bottom with a maximum 20% efficiency.
Since semiconductor optoelectronics is my jam I can add here that that’s because Silicon, the purest and most readily available semiconductor has an ‘indirect bandgap’. That is to say, light hitting the Silicon has to transfer some energy to the Silicon lattice itself in order to get an electron from the ground state in to the conduction band (from where it can be used to power a device). There are direct bandgap semiconductors available, in which all the photon energy can be transferred to electrons, but they’re much more difficult to make, but people are working on it as well as other ways of making more efficient solar cells, so expect that 20% to rise!
I guess the important point here though, is that all these numbers are a lot lower than people expect — power generation is pretty inefficient no matter how you do it.
References:
Got all the percentages from this site: http://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/
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Jaclyn Bell answered on 19 Mar 2015:
Other than the fossil fuels we are currently using up, the most cost-effective way of producing power that I can think of is nuclear energy. There is still a lot of research in to fusion power – which is when we fuse two light atomic nuclei together to form a heavy nucleus. This process gives off a lot of energy as heat which we can use to generate electricity, and although it is non-renewable, it would provide more energy than anything we are currently using today! It gives off only very little radioactivity so there is no need for special storage of by-products or anything, and no environmental risk of leakage, etc as the reactor will switch off immediately if theres a problem.
To enable nuclear fusion we first have to pump in a lot of energy to force nuclei to fuse – the nuclei don’t want to fuse and are like two magnets repelling each other – and so it take a lot of energy! However, even though we have to pump a lot of energy in to the system to start off with, the energy released is a lot more than we pumped in – so to me it seems like a win-win situation 🙂
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