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The article tries to explain the difference between primary, final and useful energy to justify why moving to renewables would be easier than at first glance. B

by dudus 6y ago

The article tries to explain the difference between primary, final and useful energy to justify why moving to renewables would be easier than at first glance. But I just don't feel like I got convinced in the end. If anything I'm more confused now than before. In special this part about air conditioners being 300% efficient sounds to me like maybe they don't know what they are talking about. “Electrical devices can sometimes offer higher than 100% efficiency,” said BNEF analyst Matthias Kimmel. That might seem odd. How can there be more energy as output than input? But that’s exactly what heat pumps and air conditioners do. They use electricity to shift heat from the outside to inside, or vice-versa, and typically provide three units of energy service for one unit of energy input, meaning an efficiency of 300%.

dboreham 6y ago
That was easy. Just put a few of them back-to-back and you'll have 10X as much energy.
- sounds 6y ago
  Because this doesn't violate the second law of thermodynamics it is impossible to get to 10X - https://en.wikipedia.org/wiki/Coefficient_of_performance https://en.wikipedia.org/wiki/Coefficient_of_performance
akshatrathi 6y ago
I wrote the story. The efficiency here isn't breaking the first law of thermodynamics. It's just the industry's way of measuring how much work gets done for a certain amount of input. If the work is heating or cooling, then shifting heat from in one direction or another can be done using heat pumps, which move three units of thermal energy for every unit of electrical energy consumed. Might that explain the conundrum?
- deleted 6y ago
  [deleted]
- dudus 6y ago
  But then aren't you comparing apples and oranges when you call both that and the loss as heat and noise from coal as "efficiency"?
  - renewiltord 6y ago
    Well, we're not interested in a thermodynamic comparison. We're interested in a useful-energy-obtained for useful-energy-spent comparison. For instance, if I leave a block in the sun and then bring it inside, I have only expended the energy to move the block out and then move the block in. It doesn't make sense for me to include the sun's contribution to the system because that's not a cost I incur. The actual apples to apples comparison in efficiency _is_ the heat emitted by the block in my house divided by the cost of moving the block.
- foldingmoney 6y ago
  This is a property of _what the device is doing_ (moving heat from one place to another) as opposed to being a property of how it's powered, though.
goodcanadian 6y ago
Air conditioners move heat from inside the house to outside. So, they can provide more cooling (move more heat) than the equivalent input energy. That is how you come up with greater than 100% efficiency.
jcampbell1 6y ago
What is wrong with the concept of a heat pump? A resistor converts electricity into heat 100% efficiently, and a heat pump is often 3x as efficient at heating a house vs electric baseboards.
- dudus 6y ago
  Ok then the electric baseboard is 30% efficient vs the heatpump which is 100% efficient.
  - nickff 6y ago
    How are you calculating efficiency? It's usually: efficiency = useful work / energy input Efficiency is not calculated relative to the best performing machine.
  - thatcherc 6y ago
    But a resistor converts 100% of the electrical energy it consumes into heat. So if you were to take the same amount of electrical energy and run a heat pump, you could get 3x more heat into a room. In that sense, the heatpump is 300% efficient.
    - Gibbon1 6y ago
      Yeah one can argue semantics all one wants but you still get 3 to 4 times more low grade heat per kwh from a heat pump than a resistive heater. And that's what you actually care about.
  - NovemberWhiskey 6y ago
    No; you're missing the point - 100% of the energy in an electric baseboard system is converted into heat. It's 100% efficient. There is no more effective way to turn electricity into heat than resistively. A heat pump doesn't turn electricity into heat. It moves heat from one place (outside) to another place (inside); and can seem more efficient because the system isn't closed.
    - 6y ago
_Microft 6y ago
Heat pumps move more heat (which has the same unit as energy, that's why you can put the numbers in a ratio and get a unitless number) than they use energy for the process. This is the crucial point for heating with them, otherwise they would make little sense (except for using them for cooling) over having an electric heater instead. Here is something to read on this: https://en.wikipedia.org/wiki/Coefficient_of_performance https://en.wikipedia.org/wiki/Coefficient_of_performance Jump to "Examples" if you like concrete examples.
deleted 6y ago
[deleted]
bungle 6y ago
Another example is to light up a candle, then use a peltier element and a heatsink to generate electricity. Then use that electricity to power a led. The outcome is that you have some of the candle light, but you will have a much more light from the led.
ActionPlankton 6y ago
This discussion of heat pumps makes me want to add that we may also ignore cogeneration too much. We just don't think about heat flows and temperature enough. There is, of course, the communal thing, done in Sweden and Russia and college campuses, with a power plant and steam pipes going to apartments. But what about an appliance for suburban America? Like, combine a gas turbine generator with an HVAC system and hot water tank (pretty sure you can buy things like this in Germany). No unsolved technical problems here. You generate electricity for your home, heat it with waste heat, and absorb temporary excesses in capacity by usefully heating water. You could imagine integrating other things too: If you need more heat than you use electricity, then you might as well use the electricity to do something high-value (cryptocurrency is a crime against the environment, but you might as well compute some hashes in your resistive heater). All this becomes an elaborate way to burn natural gas to make heat, but you get a bunch of other things out besides. The "smart controller" aspect then becomes interesting -- but even that is "just simple automation", not super-difficult AI. Maybe logistically, the "everything is electric; electricity comes from renewables/nuclear; and heat comes from heat pumps" solution is easier in the long run? But this more "decentralized heat engines" solution has the "advantage"(?) that it could run on biomass, which is easy to store (however, I am aware of the problems of wood pellets and deforestation).

by dudus 6y ago

dboreham 6y ago

That was easy. Just put a few of them back-to-back and you'll have 10X as much energy.

sounds 6y ago
Because this doesn't violate the second law of thermodynamics it is impossible to get to 10X - https://en.wikipedia.org/wiki/Coefficient_of_performance https://en.wikipedia.org/wiki/Coefficient_of_performance

akshatrathi 6y ago

I wrote the story. The efficiency here isn't breaking the first law of thermodynamics. It's just the industry's way of measuring how much work gets done for a certain amount of input. If the work is heating or cooling, then shifting heat from in one direction or another can be done using heat pumps, which move three units of thermal energy for every unit of electrical energy consumed. Might that explain the conundrum?

deleted 6y ago
[deleted]
dudus 6y ago
But then aren't you comparing apples and oranges when you call both that and the loss as heat and noise from coal as "efficiency"?
- renewiltord 6y ago
  Well, we're not interested in a thermodynamic comparison. We're interested in a useful-energy-obtained for useful-energy-spent comparison. For instance, if I leave a block in the sun and then bring it inside, I have only expended the energy to move the block out and then move the block in. It doesn't make sense for me to include the sun's contribution to the system because that's not a cost I incur. The actual apples to apples comparison in efficiency _is_ the heat emitted by the block in my house divided by the cost of moving the block.
foldingmoney 6y ago
This is a property of _what the device is doing_ (moving heat from one place to another) as opposed to being a property of how it's powered, though.

goodcanadian 6y ago

Air conditioners move heat from inside the house to outside. So, they can provide more cooling (move more heat) than the equivalent input energy. That is how you come up with greater than 100% efficiency.

jcampbell1 6y ago

What is wrong with the concept of a heat pump? A resistor converts electricity into heat 100% efficiently, and a heat pump is often 3x as efficient at heating a house vs electric baseboards.

dudus 6y ago
Ok then the electric baseboard is 30% efficient vs the heatpump which is 100% efficient.
- nickff 6y ago
  How are you calculating efficiency? It's usually: efficiency = useful work / energy input Efficiency is not calculated relative to the best performing machine.
- thatcherc 6y ago
  But a resistor converts 100% of the electrical energy it consumes into heat. So if you were to take the same amount of electrical energy and run a heat pump, you could get 3x more heat into a room. In that sense, the heatpump is 300% efficient.
  - Gibbon1 6y ago
    Yeah one can argue semantics all one wants but you still get 3 to 4 times more low grade heat per kwh from a heat pump than a resistive heater. And that's what you actually care about.
- NovemberWhiskey 6y ago
  No; you're missing the point - 100% of the energy in an electric baseboard system is converted into heat. It's 100% efficient. There is no more effective way to turn electricity into heat than resistively. A heat pump doesn't turn electricity into heat. It moves heat from one place (outside) to another place (inside); and can seem more efficient because the system isn't closed.
  - 6y ago

_Microft 6y ago

Heat pumps move more heat (which has the same unit as energy, that's why you can put the numbers in a ratio and get a unitless number) than they use energy for the process. This is the crucial point for heating with them, otherwise they would make little sense (except for using them for cooling) over having an electric heater instead. Here is something to read on this: https://en.wikipedia.org/wiki/Coefficient_of_performance https://en.wikipedia.org/wiki/Coefficient_of_performance Jump to "Examples" if you like concrete examples.

deleted 6y ago

[deleted]

bungle 6y ago

Another example is to light up a candle, then use a peltier element and a heatsink to generate electricity. Then use that electricity to power a led. The outcome is that you have some of the candle light, but you will have a much more light from the led.

ActionPlankton 6y ago

This discussion of heat pumps makes me want to add that we may also ignore cogeneration too much. We just don't think about heat flows and temperature enough. There is, of course, the communal thing, done in Sweden and Russia and college campuses, with a power plant and steam pipes going to apartments. But what about an appliance for suburban America? Like, combine a gas turbine generator with an HVAC system and hot water tank (pretty sure you can buy things like this in Germany). No unsolved technical problems here. You generate electricity for your home, heat it with waste heat, and absorb temporary excesses in capacity by usefully heating water. You could imagine integrating other things too: If you need more heat than you use electricity, then you might as well use the electricity to do something high-value (cryptocurrency is a crime against the environment, but you might as well compute some hashes in your resistive heater). All this becomes an elaborate way to burn natural gas to make heat, but you get a bunch of other things out besides. The "smart controller" aspect then becomes interesting -- but even that is "just simple automation", not super-difficult AI. Maybe logistically, the "everything is electric; electricity comes from renewables/nuclear; and heat comes from heat pumps" solution is easier in the long run? But this more "decentralized heat engines" solution has the "advantage"(?) that it could run on biomass, which is easy to store (however, I am aware of the problems of wood pellets and deforestation).