Tuesday, December 09, 2014

Technical Feasibility

That something is somehow technically feasible, doesn't mean it makes economic or even environmental sense.

Let's consider the following question:

1. Is it feasible for a country to transition to 100% renewable* electricity? (Assuming there are no financial or material constraints).

The answer is almost certainly yes.**

However, that is not the important question. The important question is:

a. What would be the purpose of generating all the electricity of a country with renewables?

If the answer is: to reduce CO2 emissions, then I think we first need to make our homework.

Off the bat, neither solar PV nor wind are zero carbon emitters (once their lifecycle is considered). Sure, no technology, not even hydro, is zero emissions but according to the IPCC**** utility scale solar PV has a median value of 48 grams of CO2 equivalent per kWh. Low, but not extremely low. Wind clocks in at 11 grams. Much better.

However, the numbers above do not include either the back up plant (usually fossil fuel powered) that is needed most of the time to support the relatively low capacity factors of renewable energy, nor the lifecycle emissions of the massive storage that would be required to somewhat wean renewables from fossil fuel plants.

So say, if on an annual basis wind supplies power 25% of the time and a natural gas power plant the rest of the time, the weighted emissions would be:

          25% x 11 grams/kWh + 75% x 490 grams/kWh = 370 grams/kWh

Yes, it is lower than a natural gas power plant by itself, (reduction of 120 grams/kWh) but are these modest CO2 reductions worth the double investment?

And, more important, is there a better way to invest our limited financial (and material) resources to achieve more bang for the buck?

As an exercise, the replacement of a coal plant with a natural gas plant would result in the following reduction:

          820 grams/kWh (coal) - 490 grams/kWh (natural gas) = 330 grams/kWh

The reduction in emission is almost three times larger and probably with a smaller investment that would last longer. (How long before wind turbines have to be replaced?).

Now, if we replace the coal plant with a nuclear one the numbers look this way:

          820 grams/kWh (coal) - 12 grams/kWh (nuclear) = 808 grams /kWh.

The reduction in emissions is almost seven times larger than with renewables.

Conclusion: technical feasibility by itself does not justify investments in renewable energy. More important is to consider the financial and environmental factors.

Feel free to add to the conversation in Twitter: @luisbaram

* By renewables we mean solar and wind in this article. Hydro is also a renewable but it is in a league by itself and we actually already have countries generating 100% of its electricity with it. Among them we have Paraguay and Albania.

** Sure, the manufacture of the wind turbines and solar panels would require massive inputs of fossil fuels, but for simplification we won't consider them at this moment.


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