In my opinion alternative energy is same what you mentioned i.e. energy from any source except fossil fuel. Renewable energy is from the source which is always available and non-perishable like solar energy etc. The sustainable energy is from renewable source and economically feasible and environmentally safe.

Hi Akinlabi,

In my opinnion, are quite simmilar therms but used to reflect different characteristics of the energy: sources, environmental impact and usability over time.

Alternative energies are those alternative to the ones that produce contamination i.e. do not originate from fossil C sources or radiactive materials.

Renewable can be seen as end-less, the pertrol sources are finite and once you use it there is no way to re-use this, the same for radiactive materiales, on the contrary if you produce electricity from the wind sun or waves you can assume that your energy source is "infinite".

Sustainable energies are those that you can get from a giving source and maintaining the potentiallity over-time trespassing your life span and transferred unaltered for future generations

Hope this helps

The term sustainable suggests to me something that can be carried forward forever, ideally with no loss (perfectly sustainable).

The term renewable suggests to me something that can be remade at any point. Something renewable may or may not be sustainable. IOW, it may or may not be possible to remake something forever (with no loss).

The term alternate suggests to me something that is not part of the current norm.

Hi Akinlabi,

I totally agree with your definitions of alternative and renewable energy. However, for sustainable energy, if you look from another angle, the term focuses on three aspencts - people, environment, and economy equally. Clean coal might be considered a form of sustainable energy for society if you weigh the three aspects.

Thanks

@Fang...

Coal can't be sustainable energy source.. availability of coal is 'finite'.. unless you are thinking about 'charcoal'.

Mr Weimer got us good definition here, but maybe a bit short so many details still debating...

for a sustainable energy, we have to take in account the economical and social counterpart, in addition of the environmental (and ressources) impact, each of them need to be viable in long term run to be sustanaible...(and ressources need to be infinite or renewable)

renewable energy is quite simple, it's renewable when the regrowth/production/reapparition rate his equal or greater than the consumption rate....(so it's can be use indefinately) biomass energy is renewable, gaz energy isn't (the reapparition rate is too long)

The question about which term to apply to a given product, not just an energy source, certainly needs to be considered across all aspects of its use ... social, economical, political, environmental, safety, and so forth. I would add to the list the term recyclable and include timescales.

Sustainable: After each use, it can be carried forward to be used again exactly as it was to start, ideally forever and with no loss. Perfectly sustainable would be the ideal case.

Renewable: After each use, it can be remade or reconstituted to be used again at exactly the same usage standards. Perfectly renewable would be the ideal case.

Recyclable: At some point, after being used, it can be recast for some other use. Fully recyclable would mean everything in the original is reused for something else.

Alternative: It is not the current norm or predominant item in use.

Finite (Limited) or Infinite: By any practical measure, it will or will not last forever.

The terms can apply in different ways. An alternative product need not be sustainable or recyclable. Alternatively speaking, an alternative energy source should absolutely not be call alternative solely because it is renewable or sustainable.

The fundamental issue with any energy source is, once it is used, it disappears. This really means, at the purist level of thinking, even sunlight or wind is not "captured and regenerated again exactly as is". Therefore, at the purist level, even these two sources are just as unsustainable as oil or gas. The difference here is, oil and gas are a finite resource, while sun and wind representan infinite supply by practical comparison.

So, if we list energy sources and suggest that many of them are unsustainable, non-renewable, and non-recyclable (in the purist sense because they disappear), we might then say this ...

Fossil Fuels: not alternative, finite

Bio-Fuels: alternative, infinite

Syn-Fuels: alternative, renewable?, infinite

Nuclear: recyclable?, alternative, infinite?

Solar + Wind: alternative, infinite

The problem of definition of the terms sustainable, renewable, and recyclable is not the case for such hardware products like cell phones or cars or washing machines or ... that do not disappear when used. Perhaps for energy sources, the term sustainable or renewable has come to mean something equivalent to infinite in supply. Hence nuclear, solar, wind, bio-fuels, and syn-fuels are presented as sustainable, whereas fossil fuels are not.

Alternative means other than current use of the most common use of energy. For example: most common was wood, alternative then becomes coal. Then most common is coal, alternative then becomes oil. etc. An alternative does not necessarily mean renewable or sustainable.

Renewable means that the source of energy replenish itself provided that consumption rate is less than replenishment rate. Renewable can be or can not be alternative. Renewable is sustainable. For example, grass and bamboos population and growth exceeds consumption made by people using it as source of energy for cooking provided that the population of people in the same domain and rate of consumption is less.

Sustainable energy is a source of energy that is renewable or greatly exceeds the today and future use of current use of energy. For example, today wood, coal, oil, uranium is not practical today. Hydrogen fusion (theoretically) seems to be sustainable by today's standard (because water is plentiful) however it will not be sustainable if population grow, energy demand increases etc. Water is a finite supply on earth and it has other more important uses than source of energy. Helium from the sun seems to be sustainable for tens of thousand of years but it will be finite unless we learn to travel to another star. Then helium becomes sustainable.

Hope that clarify

I appreciate everyone's contributions and comments to this topic. While I agree with the "theoretical definitions" of Mr Weimer, the definitions appear to be too purist, ideal and perhaps not in the context of energy. Ideality is a concept scientists dream of but never attain. Nevertheless this topic is an interesting debate that bring about different views. But I definitely appreciate Mr Weimer's contribution as well as others who have commented and/or simply followed the questions!

@A Adeyemi: When one has no foundational definitions of the base terms to start, then anarchy is sure to follow. Perhaps that is why, when you ask your question to folks who work only in the context of energy, you may get as many answers as the number of people you ask, and the answers may vary depending on the time of day or political/economic landscape. As you note, perhaps that is another underlying lesson from this thread.

I would hesitate otherwise to say, the definitions that I give are "outside the context of energy". That implies that something is wrong with the root definitions, which certainly is not the case. A better statement about the problem (if indeed there is any problem) is the inverse of your statement--the definitions of sustainable, renewable, and alternative energy are still ambiguous (as currently in use) in the sense that they still do not seem to fit consistently in the over-arching definitions of sustainable, renewable, and alternative. In this case, we do not have to fix the definitions of the root terms to fit the context of energy; we have yet to solidify how they are applied in the context of energy.

[ note added in edit ]

After some further thought, I can see your point of reference better. Sustainable energy ... How to define this one in particular? The other two (renewable and alternative) are to me less ambiguous.

Thanks for the thought-provoking question to start this thread!

I think Jeffrey has done an excellent job of defining the terms. I offer some references in the Frequently Asked Questions at www.regulationbodyofknowledge.org . The FAQs examine the role of energy sector regulators in promoting cost-effective renewable energy projects (as well as energy efficiency)--particularly in developing countries. The attached paper summarizes some of the key points; it appeared in the July 2013 Electricity Journal.

Here is the link to the paper

https://www.conserve-energy-future.com/isrenewableenergysustainable.php