Well it looks like I helped open up a hornets' nest!
Using equivalent primary energy (that which I quoted) is a method of "normalizing" energy production in terms of a standard (i.e. megatonnes of oil equivalent). This is a difficult, perhaps impossible, task to do in a fair manner.
Take coal, for instance. If it is used in steel making (as coke), its heat is used for just that - heating the ore. Presumably a large fraction (>70%? I'm guessing.) of the heat content of the fuel goes into heating the ore. If, however, the coal was used to generate electricity to power an electric arc furnace (generally better quality steels), then you have the coal to electricity transformation. Essentially the same net product (steel of different qualities), but two very different energy implementations (and "efficiencies") of the same primary source .
Or what about wood? If you heat your home with wood (preferably not in an urban setting), the energy of the wood goes primarily into low-grade heat (+ a bit of light, which turns to heat). And, hopefully, most of that goes to heat your home (and not the outdoors). But if that wood is waste at a pulp mill or lumber mill, and is burned (gas or oil over-firing is used, I believe), then there are energy conversion losses as steam is produced. Using the steam for heating processes, rather than electricity generation, also change the energy utilization.
With hydro electricity, the primary energy is falling water. The potential power is gravitational accn x head x mass flowrate. This is the primary energy available, but there are losses (turbine, friction, generator, plus some kinetic energy in the exit flow so the water will move away from the powerhouse). I'm not sure what the conversion rate is - presumably a function of the height of the dam and size of the flumes - but I seem to recall something over 90%.
With nuclear generation, don't forget that net generation (i.e. what is supplied to the switchyard and thus the grid) is on average 93 to 94% of gross generation (those primary pumps are big, thus using a lot of in-house energy. The same for coal and gas-fired steam-generating stations). And don't forget line losses (for all electrical generation).
Anyhow, the gist of it is that the end use of the energy determines the "efficiency" of converting heat energy to that which you desire. And it makes energy comparison soooo difficult, to say nothing of the public perception problem.
From: Duane Pendergast [mailto:email@example.com]
Sent: Wednesday September 25, 2002 7:15 AM
Subject: [cdn-nucl-l] Canadians and Energy Understanding
My contribution to positive thinking this fine morning follows.
It's doubtful that 99% of Canadians make any distinction between
and energy at all.
The contribution of hydroelectricity, in particular, is compared
energy sources inadequately in many publications as it is assumed equal to
thermal energy. Educating Canadians on these fine distinctions would be a
monumental undertaking - involving the whole education system perhaps.
The understanding of these points by reporters is on par with
public so it's no surprise they publish misleading information.
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