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So, the exajoules mentioned for coal are including coal used for home heating, and blast furnaces etc.?

No. The point is, the concept of "primary energy", as originally developed for fossil fuels, means the entire energy release of fuel burning, whatever ratio of it is actually used. Thus when you use the same amount of coal for home heating and electricity generation, the end-use energy will be greater for the first, but the primary energy will remain the same. And the same way, if you increase power plant efficiency, the same amount of fuel will generate a higher amount of end-use energy from the same amount of primary energy.

The concept gets murkier for non-fossil sources of energy. For nuclear energy, one can count the heat generated by nuclear fission as the primary energy, with the electricity generated by the steam taking up that heat as the end-use energy (well, minus grd losses). For wind power, there is no fuel, but one can consider the sum of electricity generated and the consumption of the turbine's own motors as primary energy.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Feb 11th, 2008 at 08:26:38 AM EST
[ Parent ]
I understand this. I was wondering whether the 120 exajoules number above for 'primary energy from coal' was referring to the primary energy output of electric coal plants, or to the total primary energy output of all coal burning, including heating.

To compare the first to wind energy production, be it electric power or 'primary wind power' is of course silly, unless most of the non-electric coal power would be used for useful purposes, which isn't the case AFAIK.

Using the total primary energy release from coal is of course even stronger number-pumping in favor of coal, but at least it adresses a real problem with current renewables: most of them are at least ballpark cost competitive when it comes to electricity generation, but not for low-quality heat generation. But I don't see how this is any different for nuclear energy. It's not as if we are going to use excess nuclear heat to heat buildings.

by GreatZamfir on Mon Feb 11th, 2008 at 08:36:14 AM EST
[ Parent ]
I was wondering whether the 120 exajoules number above for 'primary energy from coal' was referring to the primary energy output of electric coal plants, or to the total primary energy output of all coal burning, including heating.

Oh. You have a point: I checked, actually the latter.

Agreed on your points.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Feb 11th, 2008 at 09:04:04 AM EST
[ Parent ]

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