Monday, July 16, 2007

How Do You Define "Renewable"?

That's the question in Florida, and the topic of a new post from We Support Lee.


Josh said...

Renewable is any energy source liked by the wets. It's a buzz word, a fashion label, no longer an engineering description.

Doug said...

I don't think it's reasonable to call nuclear a renewable energy source, at least at the present time. It is reasonable to call it a low-carbon energy source.

Ultimately the argument about renewability boils down to timescale. Sources like fossil, nuclear, even geothermal, will deplete (with current technology) on human timescales (100s to perhaps 1000s of years). Sources like tidal, solar, wind, etc. will not deplete for millions/billions of years.

The big plus for nuclear verus a lot of other low-carbon sources is that it's practical for baseload today, without needing to pre-suppose breakthroughs that might not appear. IMO it's best not to speculate on breakthroughs (such as extraction of fuel from diffuse sources), otherwise you're just debating energy fantasies with people pushing impractical energy non-solutions. Breeder technology is probably as far as I'd go in terms of projection - it's been practical for decades, but hasn't been successfully commercialised. Breeding plutonium (and U233 from thorium) would take us out 1000s of years - while not renewable, I'd call it sustainable.

Stewart Peterson said...

They should define any reactor that uses fuel already in inventory as renewable--they are, by definition, since they aren't depleting any natural resources--and mandate 30%-35% renewables by 2025. That would include breeders, CANDUs using DUPIC, LWRs using downblended weapons material and thorium...most of the promising fuel cycles that need development.

That should work well with the recent reprocessing plant proposal--it would be a lot easier if they didn't have to separate actinides at all.

Anonymous said...

The term is a brilliant piece of marketing, but it is meaningless to the engineer. Everything is renewable to some degree, or everything non-renewable to a degree, depending on which way you look at it. Diffuse power sources such as wind and solar have no fuel content, but they consume raw materials and human labor just the same. Periodically, these raw materials and human inputs must be replenished or renewed, just like any other industry.

Here is my definition of renewable: the EROEI (energy return on energy invested) is infinite. Now this is precisely what advocates of diffuse power would have you believe about their pet projects. It's not true of course, as it would violate the second law. I'd even settle for something with an EROEI >> 100 as renewable, seeing as infinity is not about to happen.