3 ms·

Whenever you burn something to do work, you are limited by a principle in thermodynamics called the Carnot cycle[1]. It basically says that converting heat to w

Whenever you burn something to do work, you are limited by a principle in thermodynamics called the Carnot cycle[1]. It basically says that converting heat to work has a maximum efficiency (depending on the situation). 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. [1]: https://en.m.wikipedia.org/wiki/Carnot_cycle https://en.m.wikipedia.org/wiki/Carnot_cycle

usmeteora 9y ago
You are correct, but just as a point out for people, wind I am not sure, but Photovoltaics I am positive are accumulate per panel, or per unit for newer panels redesigned as solar roofing materials, intead of panels on roofing materials, utilize inverters, which are some of the most lossy circuit designs for power conversion right now. 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.
- epistasis 9y ago
  >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, 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...)

usmeteora 9y ago

You are correct, but just as a point out for people, wind I am not sure, but Photovoltaics I am positive are accumulate per panel, or per unit for newer panels redesigned as solar roofing materials, intead of panels on roofing materials, utilize inverters, which are some of the most lossy circuit designs for power conversion right now. 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.

epistasis 9y ago
>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, 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...)