Is solar energy the best renewable source of energy?

Question

Here is my thinking on renewable resources. Biomass is the absolute worst way to go because it releases CO2 and damages habitats.

Geothermal is not far behind but is for a different reason. Geothermal is stable but has a low power output. Geothermal energy is better used as heat than electricity.

Water power can mean damage to aquatic and thus land habitats but more importantly, there is a minimum useful flow rate.

Wind power has a maximum useful speed and is unreliable.

Solar power is unreliable but as long as sunlight isn't at 0, it is useful.

In other words, the more reliable the source of energy, the worse for either producing electricity (geothermal) or for the environment (water and biomass). And the less boundaries the better when it comes to an already unreliable source.

But is my reasoning true? Is solar power really the best choice for renewable energy?

Answer 1

The validity of your assumptions depend very much on your location and on the amount of energy you want to generate. Some small-scale solutions do not suffer from the same drawback as large-scale solutions.

Biomass

The CO2 emitted by burning biomass is CO2 from the atmosphere that was taken up by plants and trees. This means that energy from biomass can be generated CO2-neutral, provided the biomass that is burned is replaced by the same amount of new trees and plants (and ignoring the use of non-renewable energy for transporting the biomass). There can be other drawbacks of biomass like atmospheric pollution, or edible biomass competing with food/feed and driving up prices. However using crop residues or manure to generate methane (in a biodigester) for example and do not have these disadvantages. In this case economic viability can be a problem depending on the scale and availability of biomass.

Geothermal

Geothermal is indeed very efficient for providing heat and less so for providing energy, but that doesn't mean it's totally unsuitable. For example in Iceland 29% of the generated electrical energy comes from geothermal sources and 9 out of 10 households are heated with geothermal energy. Obviously in other countries with less volcanic activity geothermal energy is more costly.

Hydro-electricity

I agree with you that hydro-electricity is one of the most environmental unfriendly renewable energy sources. It disrupts river flows, hinders procreation of certain types of fish, and causes methane emissions by flooding areas with vegetation. But these problems apply primarily to new to-be-built dams. Small scale hydro-electricity can solve most of these problems, and existing dams in Norway are much more environmentally friendly than dams in the tropics.

Wind and solar power

Both wind and solar power are efficient and cost-effective and have good scaling capabilities. That's also the reason these two are the fastest growing renewable energy sources. Obviously they are only suitable for regions with plenty of sunshine or wind. It's assumed that solar power is not efficient at high latitudes, but some researchers are trying to prove otherwise. The biggest drawback of both wind and solar is that energy storage is costly and difficult, but the expectations are that the popularity of both energy sources will stimulate research for better and cheaper battery technology.

Conclusion

There isn't a single, renewable energy source that will solve all our problems. All renewable energy sources have their pros and cons and which type of renewable energy is best depends very much on the local circumstances and the scale you want. Often a mixture of different renewable energy sources is the best solution. In many cases solar and wind energy are the good options because they can compete with and even outperform non-renewable energy sources in terms of cost.

Answer 2

My interest here is in biomass. I say for my region of the country or world biomass is about as renewable as u can get! I am mowing my 1 acre of grass and compressing the dry clippings into pellets for burning in my stove during Winter. I once calculated how many pounds of cellulose material this is. I also planted a small patch of sunflowers which should grow to over 6' plus produce some oil in the seeds. This should be a lot more biomass per unit of land than grass. This is true use of solar energy since the Sun gave the plants energy to grow. All the CO2 going into the air during Winter is no more than what was absorbed during the Summer. As a wide scale solution in an urban environment almost clearly there would be unacceptable smoke from this. Maybe some smokestack scrubbers could be used.

Another efficient use of solar energy is to make zinc air rechargeable batteries with removable zinc plates that can be replated during the Summer when excess solar energy can be collected by solar cells. The plates could be stored separately until ready to use again in Winter when much less solar is available.

Answer 3

Renewables shouldn't be thought of as an either / or proposition. If we're thinking about an entire economy you want a variety of sources at a variety of scales, with a variety of storage systems.

The availability of individual solar panels, wind turbines etc. can vary a lot over time. But with a sufficiently distributed network the availability becomes much more predictable and reliable.

This report is old (2010) but presents a study showing just how reliable an economy scale supply of renewable energy would be.

http://www.greenpeace.org/international/en/publications/reports/renewables-24-7/