6 ms·

Nice that the cost has come down. Unfortunately, that which makes electric cars and planes feasible, namely energy density (Wh/litre) and specific energy (Wh/kg

by FabHK 5y ago

Nice that the cost has come down. Unfortunately, that which makes electric cars and planes feasible, namely energy density (Wh/litre) and specific energy (Wh/kg), has not improved that rapidly. The article mentions a factor of 3.4 over 30 years for energy density, ie 4% p.a., or doubling every 17 years. I think electric aircraft need another doubling or two in specific energy to become feasible, so another few decades :-/

walrus01 5y ago
If one looks at the Wh/kg of the very best li ion batteries right now (about 250Wh/kg) and then compares it to the Wh/kg in avgas or jet a or diesel, it's nuts. Even if you lose 40-60% to waste heat. The amount of energy contained in those fuels is ridiculously dense by comparison.
- winter_blue 5y ago
  It looks like diesel holds ~10,700 Wh/kg[1]. That’s over 40 times the volumetric energy density. I hope people find an electrical energy storage system (ie a battery) that’s cheap, and with high mass and volumetric energy density, soon. That would be huge for solving the impending climate (and pollution) crisis. [1] https://en.m.wikipedia.org/wiki/Energy_density#In_chemical_reactions_(oxidation) https://en.m.wikipedia.org/wiki/Energy_density#In_chemical_r...
  - SigmundA 5y ago
    You must account for all the equipment to convert fuel into mechanical work as well. A battery is a large part of the equipment to covert electrons into useful electricity and electric motors and controller are comparatively light weight. Energy density is still higher I have done rough calculations that say batteries need to be at about 2000 wh/kg to be at parity with a diesel semi and the theoretic upper limit for lithium is 2600 wh/kg.
- mgoetzke 5y ago
  And the energy stored in it does not need to be paid :) That is why these companies make so much money of course.
  - ganafagol 5y ago
    Oil is free? Not sure where the Saudis got there riches from then. Otoh sitting in the sun for a few hours to charge some battery via rays from the sun is itself free.
    - tohmasu 5y ago
      >Otoh sitting in the sun for a few hours to charge some battery via rays from the sun is itself free. Sounds wonderful, please show the math.
- leoedin 5y ago
  Not only that, hydrocarbon fuels also disappear after use - meaning you get another massive boost from the weight dropping over time, as the energy required by an aircraft to cruise is partially dependent on it's weight. So the energy density of batteries is effectively even lower than on face value.
- SigmundA 5y ago
  You must also account for the engine / motor / transmission / drivetrain / fuel tank weight difference you can't just look at fuel weight alone. In ground vehicles the weight of the engine and transmission and running gear is more than an electric motor and controller with much simpler usually single speed transmission and drivetrain especially diesel. Then there is structural batteries where the structure of battery helps replace some of the vehicle structure reducing wieght. This is why electric cars are starting to be competitive. Planes are somewhat different modern turbine engines are relatively light for their power output and there is not much of a transmission on planes, usually variable props instead and fuel tanks are sort of structural. Although having many multiple props driven by small electric motors can have advantages which would be complicated and heavy to do with a drivetrain in a plane. Still electric planes are far from practical IMO.
oblio 5y ago
If we fix everything except for aircraft, we will have done enough. At that point aircraft can keep using fossil fuels for a while longer. Cars, trucks, buses, trains, HVAC, factories are what needs to be electrified ASAP.
- amelius 5y ago
  If every industry thinks like that ...
  - legutierr 5y ago
    Is there another industry that is facing similar physical constraints that would hamper a transition? I understand that reducing the carbon output in concrete production is difficult to the point of being nearly economically infeasible. Other than that?
    - scotty79 5y ago
      There are some ideas about cement industry: [pdf] https://www.google.com/url?sa=t&source=web&rct=j&url=https://awsassets.panda.org/downloads/englishsummary__lr_pdf.pdf&ved=2ahUKEwiS7pXs1ofxAhVQrIsKHcVbCAI4ChAWMAR6BAgEEAI&usg=AOvVaw1cHvI0mPvO8597FtnA6QFu https://www.google.com/url?sa=t&source=web&rct=j&url=https:/...
  - oblio 5y ago
    I can drive a car that's 20% heavier due to batteries. Nobody's going to fly a commercial plane that's 40% heavier due to batteries. Some places, current batteries just don't cut it.
    - dublin 5y ago
      The requirements for fairly large power margins for safe operation at takeoff and landing generally prevent electric airplanes from making sense and achieving FAA approval, especially for commercial applications. We are decades away from viable electric commercial aviation. Even turbine-electric series hybrids weigh and pollute more than their native kerosene-burning equivalents.
nickik 5y ago
You can't just forward project like that. The question is what people are working on. So far people main concern has been reduction in price. This has reshaped and is reshaping the supply chain, has localized production and has massive improved production efficiency. Now we are slowly starting to approximate production of a scale and efficiency where we are approaching raw materials cost. A huge amount of effort has now shifted into improving density as that is a vector to reduce cost. Huge money is flowing into silicon and lithium metal anode study. There is some hope to get there faster.
KorematsuFred 5y ago
> I think electric aircraft need another doubling or two in specific energy to become feasible, so another few decades We have plenty of fossil fuel so if most of the world stops burning gas we can run aircrafts on fossil fuels for centuries. Even emissions wont be a problem as cheaper energy on ground can be used to capture green house gases and store them someplace. > I think electric aircraft need another doubling or two in specific energy to become feasible My trucker friends loved the electric semi trucks but what they were upset about was the charging time. Every hour the truck is idle you are basically losing money, losing rhythm of driving and so on. I think with aircrafts it is going to be an even bigger issue. Does anyone know what stops us from building tech where batteries are rapidly switched ?

by FabHK 5y ago

walrus01 5y ago

If one looks at the Wh/kg of the very best li ion batteries right now (about 250Wh/kg) and then compares it to the Wh/kg in avgas or jet a or diesel, it's nuts. Even if you lose 40-60% to waste heat. The amount of energy contained in those fuels is ridiculously dense by comparison.

winter_blue 5y ago
It looks like diesel holds ~10,700 Wh/kg[1]. That’s over 40 times the volumetric energy density. I hope people find an electrical energy storage system (ie a battery) that’s cheap, and with high mass and volumetric energy density, soon. That would be huge for solving the impending climate (and pollution) crisis. [1] https://en.m.wikipedia.org/wiki/Energy_density#In_chemical_reactions_(oxidation) https://en.m.wikipedia.org/wiki/Energy_density#In_chemical_r...
- SigmundA 5y ago
  You must account for all the equipment to convert fuel into mechanical work as well. A battery is a large part of the equipment to covert electrons into useful electricity and electric motors and controller are comparatively light weight. Energy density is still higher I have done rough calculations that say batteries need to be at about 2000 wh/kg to be at parity with a diesel semi and the theoretic upper limit for lithium is 2600 wh/kg.
mgoetzke 5y ago
And the energy stored in it does not need to be paid :) That is why these companies make so much money of course.
- ganafagol 5y ago
  Oil is free? Not sure where the Saudis got there riches from then. Otoh sitting in the sun for a few hours to charge some battery via rays from the sun is itself free.
  - tohmasu 5y ago
    >Otoh sitting in the sun for a few hours to charge some battery via rays from the sun is itself free. Sounds wonderful, please show the math.
leoedin 5y ago
Not only that, hydrocarbon fuels also disappear after use - meaning you get another massive boost from the weight dropping over time, as the energy required by an aircraft to cruise is partially dependent on it's weight. So the energy density of batteries is effectively even lower than on face value.
SigmundA 5y ago
You must also account for the engine / motor / transmission / drivetrain / fuel tank weight difference you can't just look at fuel weight alone. In ground vehicles the weight of the engine and transmission and running gear is more than an electric motor and controller with much simpler usually single speed transmission and drivetrain especially diesel. Then there is structural batteries where the structure of battery helps replace some of the vehicle structure reducing wieght. This is why electric cars are starting to be competitive. Planes are somewhat different modern turbine engines are relatively light for their power output and there is not much of a transmission on planes, usually variable props instead and fuel tanks are sort of structural. Although having many multiple props driven by small electric motors can have advantages which would be complicated and heavy to do with a drivetrain in a plane. Still electric planes are far from practical IMO.

oblio 5y ago

If we fix everything except for aircraft, we will have done enough. At that point aircraft can keep using fossil fuels for a while longer. Cars, trucks, buses, trains, HVAC, factories are what needs to be electrified ASAP.

amelius 5y ago
If every industry thinks like that ...
- legutierr 5y ago
  Is there another industry that is facing similar physical constraints that would hamper a transition? I understand that reducing the carbon output in concrete production is difficult to the point of being nearly economically infeasible. Other than that?
  - scotty79 5y ago
    There are some ideas about cement industry: [pdf] https://www.google.com/url?sa=t&source=web&rct=j&url=https://awsassets.panda.org/downloads/englishsummary__lr_pdf.pdf&ved=2ahUKEwiS7pXs1ofxAhVQrIsKHcVbCAI4ChAWMAR6BAgEEAI&usg=AOvVaw1cHvI0mPvO8597FtnA6QFu https://www.google.com/url?sa=t&source=web&rct=j&url=https:/...
- oblio 5y ago
  I can drive a car that's 20% heavier due to batteries. Nobody's going to fly a commercial plane that's 40% heavier due to batteries. Some places, current batteries just don't cut it.
  - dublin 5y ago
    The requirements for fairly large power margins for safe operation at takeoff and landing generally prevent electric airplanes from making sense and achieving FAA approval, especially for commercial applications. We are decades away from viable electric commercial aviation. Even turbine-electric series hybrids weigh and pollute more than their native kerosene-burning equivalents.

nickik 5y ago

You can't just forward project like that. The question is what people are working on. So far people main concern has been reduction in price. This has reshaped and is reshaping the supply chain, has localized production and has massive improved production efficiency. Now we are slowly starting to approximate production of a scale and efficiency where we are approaching raw materials cost. A huge amount of effort has now shifted into improving density as that is a vector to reduce cost. Huge money is flowing into silicon and lithium metal anode study. There is some hope to get there faster.

KorematsuFred 5y ago

> I think electric aircraft need another doubling or two in specific energy to become feasible, so another few decades We have plenty of fossil fuel so if most of the world stops burning gas we can run aircrafts on fossil fuels for centuries. Even emissions wont be a problem as cheaper energy on ground can be used to capture green house gases and store them someplace. > I think electric aircraft need another doubling or two in specific energy to become feasible My trucker friends loved the electric semi trucks but what they were upset about was the charging time. Every hour the truck is idle you are basically losing money, losing rhythm of driving and so on. I think with aircrafts it is going to be an even bigger issue. Does anyone know what stops us from building tech where batteries are rapidly switched ?