• Question: what is the most efficient,energy renewable source? ( taking into thought: cost, material,where to build, pollution produced, amount of energy mad in one go, benefits and negatives)

    Asked by Code: Agent Zero to Thomas Telford, Stephen Hawking, Rosalind Franklin, Peter Medawar, Nicholas Shackleton, Mary Somerville, Mary Anning, John Snow, G. H. Hardy, Sir Geoffrey de Havilland, Frederick Sanger, Francis Crick, Elizabeth GarrettAnderson, Edwards and Steptoe, Dorothy Crowfoot Hodgkin, Beatrice Shilling, Aneurin Bevan, Alan Turing, Ada Lovelace on 6 Dec 2018.
    • Photo: Rosalind Franklin

      Rosalind Franklin answered on 6 Dec 2018:

      I don’t think that there is one single answer to this. It depends on where you are and what your energy needs are. For example, solar power is an excellent renewable energy source for domestic use in places like the southern USA, where the amount of sunlight is high and the peak demand for domestic power is in summer daytime (for air conditioning). It’s nothing like so good in the UK, where the number of hours of sunlight is lower and peak demand is winter night-time (for heat and light). Many industries need a constant level of power 24/7, and very few renewable sources offer this.

      Where it is available, the best source of renewable energy is probably geothermal. Unfortunately the number of places around the world where geothermal energy is available is very small, so this is never going to supply everyone. You’re in business if you live in Iceland, but not many people do.

      Hydroelectric power is very good: it produces no pollution, is controllable, and can provide a constant base load. However, it does cause some environmental damage (because dams have to be constructed) and in many places has not proved to be long-lasting (if the rivers carry a lot of silt, the dams silt up and become less effective). Also, many places in the world do not have the reliable water supply needed for hydroelectric power.

      Wind power is a mature technology, but is not good as a sole source, because the wind is not reliable. Offshore wind is usually better (ocean winds are more reliable than winds on land). The wind turbines have been shown to pose a risk to birds of prey, so they are not totally benign environmentally, and of course the materials used to construct the turbines (as in all cases, but perhaps particularly with wind because you need many small engines, not a few large ones as with hydro power) are not necessarily low-cost environmentally.

      Tidal and wave power have not been as widely studied as solar and wind. Tidal power is reliable and predictable, but can have very high environmental costs as the best sites for tidal power tend to be estuaries, which are important wildlife habitats. Wave power has been rather little studied. It may be good in some places, but clearly isn’t helpful for countries with little coastline.

      Nuclear power isn’t strictly renewable, but is often counted as such because uranium reserves are very high. Its principal disadvantages are the perceived difficulty of disposing of nuclear waste (I say “perceived”, because if it didn’t have such a bad press I think the problem is fairly easily soluble) and the fact that it is mainly suitable for base load: you can’t ramp the power up and down quickly. Nuclear fusion would be better (fusion reactors are more controllable, the fuel is very abundant and the level of radioactive waste much lower), but the technical difficulties are formidable.

      Biofuels are the easiest to implement – existing power stations can be adapted to run on biofuel – but are potentially very environmentally damaging, since people clear rainforest to grow biofuel crops. This is already seen with palm oil.

      I suspect that the best strategy is mixed, with a range of different renewable sources to suit different locations and different demand. Many of the problems with adopting renewable energy sources come down to the issue of energy storage: the source in question can generate enough energy, but not where you want it or when you want it. Therefore, if we want to run on renewables, a lot more research has to be done into better methods of storing energy (that’s why electric cars still haven’t caught on in a big way: the battery packs are expensive and heavy and still don’t provide the range that people want). One problem with this is that battery technology can require scarce resources (such as lithium) or produce toxic waste (such as lead-acid car batteries) or both.

      In summary: this is an important question, but I don’t think there is one clear answer. We need to do more research, especially on energy storage technologies and on designing our technology (e.g. our homes) to use as little energy as possible.

    • Photo: Stephen Hawking

      Stephen Hawking answered on 6 Dec 2018:

      This is a tough question as it involves lots of different parameters, all of which will be subjectively weighted. So the three main competitors are wind farms, solar panels, and nuclear energy (which is sort of renewable).

      Wind Turbines:
      These guys are the great for places that don’t have a lot of sun and are very windy. They have a typical efficiency of about 30% and are now starting to compete with coal driven energy sources. They work by having a fan that is turned by the wind, which generates electricity the same way burning coal does.

      Advantages: Almost 100% clean and renewable energy, relatively quiet, easy to set up.

      Disadvantages: Kind of expensive, requires regular maintenance/replacement (especially offshore ones due to salt corrosion), some people think they’re an eyesore.


      Solar Panels:
      Pretty good in places that have a lot of sun. These work using the photoelectric effect. A particle of light comes from the sun and knocks an electron out of place. This happens multiple times across the panel generating electricity. They are only about 15% efficient.

      Advantages: Pretty cheap, easy to install, will work anywhere there is sunlight, 100% renewable source, small so can fit almost anywhere.

      Disadvantages: Low efficiency, won’t work in dark places.


      Nuclear energy:
      This ones a bit controversial, however at the rate of climate damage nuclear may be a safe stop off, here’s why. Nuclear energy has low emissions and relatively renewable. The main problem is the waste, it needs to be stored for years before it safe to be disposed of. Nuclear energy is made by taking unstable atoms and firing neutrons at them, this causes them to split. This process is called nuclear fission. It has a very high efficiency and can produce enough energy to sustain us. The media like to make nuclear energy seem dangerous, but paradoxically, because of how hyped the dangers are presented; nuclear energy has been forced to be one of the safest methods available.

      Advantages: High efficiency, partially renewable, low emission, can be used as a replacement while we improve cleaner methods, safe!

      Disadvantages: Nuclear waste, is pretty expensive, a lot of people are scared of nuclear physics.

      Personally, I believe that we should short term invest in nuclear energy to reduce the impact of burning fossil fuels while we develop more sustainable and cheaper renewable methods. Then once we have better infrastructure for renewable energy sources (like wind turbines and solar panels), we make the switch from nuclear to completely clean energy.

      Good question!