alt Hacker NewsWhat does "Rejected Energy" mean in that graph?
Great chart, by the way.
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Rejected energy means energy that is lost as waste heat without performing any work first. For example, a coal fired power plant may generate 3 megajoules of thermal energy from coal combustion but only deliver 1 megajoule of it as electricity. The other 2 megajoules are lost as useless waste heat.
The 1 megajoule of useful electricity is also ultimately dissipated as low grade heat, but it can do work first (like generating light, or pumping water uphill).
It would be nice if before each box where rejected energy is an output, the inputs were split by rejected and non-rejected inputs.
I live in a part of the world that is far below freezing for a significant portion of the year. Thus a large portion of my annual energy usage goes into not freezing to death.
When I drive my daughter to school when it’s -40 fucking degrees, a lot of the energy I use goes into heating my vehicle, swearing, moving and swearing. But this energy also leaks through my windshield, through my exhaust system and through my engine. This energy (heat) doesn’t provide any benefit to anyone and just leaks out into the atmosphere (which we’ve already established is trying to kill me).
That’s rejected energy. Or when it’s below -40, rejected motherfucking energy. :)
Only about 30% of the energy in gasoline is converted to useful work in a gasoline car (the 'make metal box go forward' part). The remaining 70% is Rejected Energy (the steam you see going out the tail pipe in winter).
Which (not sure if you did this intentionally or accidentally) brings up an interesting point on the parent comment and the LLNL sankey:
> It's always worth remembering that electricity only accounts for ~20% of global energy consumption (in the US it's closer to 33%).
That "global energy consumption" figure includes a lot of Rejected Energy going out tailpipes and smoke stacks turning burnables into electricity. A secret bonus of wind and solar is if you produce electricity without burning things, you actually decrease the energy demand! If you're not losing 70% of your energy consumption to the Rejected category, you suddenly need a lot less total energy.