What is the exact criteria by which energy ends up as rejected?
That seems very difficult to define and I'm afraid this "America is so inefficient" rant is some misunderstanding of what is an imperfect measure.
That seems very difficult to define and I'm afraid this "America is so inefficient" rant is some misunderstanding of what is an imperfect measure.
So the rejected energy in this sankey diagram is partly just the consequence of the thermodynamic efficiency limits of the situations. Also, since there are always heat and resistance losses (the real world is not a frictionless surface), the efficiency of converting energy into work is further decreased.
All in all, we're actually pretty good at covering heat into energy. The rejected energy here is simply a consequence of the situation and thermodynamics. For other situations that don't involve heat-to-work, such as wind and photovoltaics, the Carnot cycle doesn't apply, and you can have much less rejected energy.
Until inverters are made to be more efficient, this will always be a huge bottleneck for dynamic energy input and output for the solar industry, and should be considered as apart of the losses for a solar unit.
That seems pretty unlikely, do you have any literature on that?
Inverters do sometimes become less efficient when there's less power coming out of the panels, but getting <85% efficiency out of an inverter in any common scenario would probably just mean that the install had been poorly designed.
I guess a case could be made for not capturing the thermal energy from the sun with panels and using that, but it's a strange case to make. (Probably about as strange as getting more than Carnot limits out of petroleum. Though if the waste heat is used in, say, steam pipes for distribution in a city, maybe not so strange...)
We can guess what rejected energy meant when this was drawn (presumably, Carnot efficiency was taken into account, since that's the most probable explanation for the very low efficiency of transportation), but it's hard to interpret without knowing for sure. (I assume the LLNL has a document somewhere that breaks this all down, but it would be nice to have more details in the article.)
Ideally, that waste heat would be put to some use...that's called co-generation [2]
[1] http://blog.schneider-electric.com/energy-management-energy-...
So simply running hotter is not a realistic solution to get above 30 or so percent, not at current technology levels. That's where strange staged and cogeneration schemes are applied to boost efficiency.
Low grade process heat is surprisingly useless in practice, unfortunately. Also economics and politics smack up against engineering ideals, where massive vertical integration would result in higher efficiency but short of nationalizing all industry or allowing massive monopolies its hard to integrate a coal generating plant with a steel mill heat treatment plant and a sardine canning plant and a greenhouse all under the same roof. Maybe with infinite scaling nano-technology all industrial plants could do all things to really boost efficiency.
For electricity generation, yeah. What it is that stops us from using it for residential heating? Eg, space heating and for hot water. Is it just the proximity to big power plants that makes it unfeasible?
It's been done though.
More or less rejected means "lost as heat before we can do something useful with it".
Computers will turn essentially all power entering them into heat. But then by that measure we can never make an efficient computer but would have to look at something like flops/W to give us actionable information.
What is a measure we can apply consistently to computers and cars and get actionable information?
What happens "past the meter" is a consumption question.
Generally.