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> Electricity wastes two-thirds of its primary energy; transportation wastes about three-quarters. The electricity generation waste I'm willing to take at face

> Electricity wastes two-thirds of its primary energy; transportation wastes about three-quarters. The electricity generation waste I'm willing to take at face value, but only because I am somewhat familiar with the concepts of conversion factor loss and line loss. I find both of these assertions require digging into the footnotes to understand better. Their presentation is a little too hand wavy. I'm really at a loss to understand what the transportation waste means. Sure, you also need to propel the mass of the vehicle. Is it comparing every other vehicle to a bicycle? I don't know.

bsully 9y ago
Transportation waste is the inefficiency of the internal combustion engine. The presentation isn't "hand wavy", it's just simplified. Most of the confusion in this thread is from users who don't understand relatively simple aspects of how energy is generated and used. Which is fine, but the response to that should be to look something up or ask a question, not attack the graphic.
- jackfoxy 9y ago
  Well actually there is an article along with the very fine graphic. I think the article could have expended a few more sentences on energy waste. That's all. This wasn't an attack.
deleted 9y ago
[deleted]
Retric 9y ago
The fact the tailpipe on your car ejects a lot of useless heat is waste. Similarly, a car's radiator is ejecting a lot of useless heat. Sure, tracking this feels hand-wavy but using less fuel because you drive less is different from using less fuel because the engine is more efficient. However, this stuff still very simplified as lighter cars use less fuel even without changing the % of waste energy generated.
- dibujante 9y ago
  Heat is energy. Any heat that enters the atmosphere is energy you're giving up.
  - Retric 9y ago
    99% of energy from gasoline ends up as heat, but saying it's ~0% useful energy is not really meaningful.
- SamBam 9y ago
  > lighter cars use less fuel even without changing the % of waste energy generated. Yes, but they reduce the total Joules of energy wasted, and that's the important point. And that would be reflected in the graph at hand. I know we're all talking percentages, but the graph is actually about total quantity. If everyone were in very light cars, the transportation bar would be narrower, and the total energy going to the Waste node would be smaller. So it's accurately reflecting any efficiencies of that kind.
SamBam 9y ago
> I'm really at a loss to understand what the transportation waste means. Sure, you also need to propel the mass of the vehicle. Total work done by the vehicle / total energy contained the fuel. A small combustion engine is a very inefficient converter of energy, so it's no surprise that it's only able to use 1/4 of the available energy. The rest is lose as heat (as well as minor losses such as noise and slippage).
dredmorbius 9y ago
This boils down to well-known and well-understood behaviours of energy systems, particularly at large scale. Much of the waste is simply Carnot efficiency of thermal systems: the amount of useful energy you can extract is proportional to the (absolute) temperatures (Kelvin) of the "hot" and "cold" ends of the cycle. For thermal electrical generation -- coal-fired plants, gas-fired turbines, oil-fired turbines or diesel generators, biomass thermal, solar thermal, or nuclear plants -- this is in the range of 30 - 45% or so. Ironically, high-temperature thermal coal achieves some of the best thermal efficiency. This doesn't mitigate its far more compelling downsides. Direct kinetic or photovoltaic electrical generation has no thermal losses, but is subject to the efficiency constraints of the input stream: hydroelectric, wind, or solar PV. There are additional losses in transmission (about 6%), and in electrical conversion and switching equipment ( ~<10%). The net is about a 66% energy loss in what's delivered to the electrical customer. For transportation, you have the same Carnot efficiency limits, but given the smaller temperature differential start with a lower initial efficiency -- about 30%. There are additional losses through parasitic systems (any powered in-car features: power steering, brakes, A/C, electrical and electronics, etc.), transmission losses, tire and wind drag. Again, all well understood and modeled, and well-behaved in large-number populations. The Lawrence Livermore National Lab (LLNL) has done energy modelling for the United States since the 1970s, and has a set of flow diagrams (Sankey diagrams) showing flows dating to the 1950s, through the present.

bsully 9y ago

Transportation waste is the inefficiency of the internal combustion engine. The presentation isn't "hand wavy", it's just simplified. Most of the confusion in this thread is from users who don't understand relatively simple aspects of how energy is generated and used. Which is fine, but the response to that should be to look something up or ask a question, not attack the graphic.

jackfoxy 9y ago
Well actually there is an article along with the very fine graphic. I think the article could have expended a few more sentences on energy waste. That's all. This wasn't an attack.

deleted 9y ago

[deleted]

Retric 9y ago

The fact the tailpipe on your car ejects a lot of useless heat is waste. Similarly, a car's radiator is ejecting a lot of useless heat. Sure, tracking this feels hand-wavy but using less fuel because you drive less is different from using less fuel because the engine is more efficient. However, this stuff still very simplified as lighter cars use less fuel even without changing the % of waste energy generated.

dibujante 9y ago
Heat is energy. Any heat that enters the atmosphere is energy you're giving up.
- Retric 9y ago
  99% of energy from gasoline ends up as heat, but saying it's ~0% useful energy is not really meaningful.
SamBam 9y ago
> lighter cars use less fuel even without changing the % of waste energy generated. Yes, but they reduce the total Joules of energy wasted, and that's the important point. And that would be reflected in the graph at hand. I know we're all talking percentages, but the graph is actually about total quantity. If everyone were in very light cars, the transportation bar would be narrower, and the total energy going to the Waste node would be smaller. So it's accurately reflecting any efficiencies of that kind.

SamBam 9y ago

> I'm really at a loss to understand what the transportation waste means. Sure, you also need to propel the mass of the vehicle. Total work done by the vehicle / total energy contained the fuel. A small combustion engine is a very inefficient converter of energy, so it's no surprise that it's only able to use 1/4 of the available energy. The rest is lose as heat (as well as minor losses such as noise and slippage).

dredmorbius 9y ago

This boils down to well-known and well-understood behaviours of energy systems, particularly at large scale. Much of the waste is simply Carnot efficiency of thermal systems: the amount of useful energy you can extract is proportional to the (absolute) temperatures (Kelvin) of the "hot" and "cold" ends of the cycle. For thermal electrical generation -- coal-fired plants, gas-fired turbines, oil-fired turbines or diesel generators, biomass thermal, solar thermal, or nuclear plants -- this is in the range of 30 - 45% or so. Ironically, high-temperature thermal coal achieves some of the best thermal efficiency. This doesn't mitigate its far more compelling downsides. Direct kinetic or photovoltaic electrical generation has no thermal losses, but is subject to the efficiency constraints of the input stream: hydroelectric, wind, or solar PV. There are additional losses in transmission (about 6%), and in electrical conversion and switching equipment ( ~<10%). The net is about a 66% energy loss in what's delivered to the electrical customer. For transportation, you have the same Carnot efficiency limits, but given the smaller temperature differential start with a lower initial efficiency -- about 30%. There are additional losses through parasitic systems (any powered in-car features: power steering, brakes, A/C, electrical and electronics, etc.), transmission losses, tire and wind drag. Again, all well understood and modeled, and well-behaved in large-number populations. The Lawrence Livermore National Lab (LLNL) has done energy modelling for the United States since the 1970s, and has a set of flow diagrams (Sankey diagrams) showing flows dating to the 1950s, through the present.