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)

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.