6 ms·

This is a good reason why Tesla cars are folly. This is why electric vehicles won't work. I'll copy in most of a comment I made a few days back. Let's say tom

by sien 14y ago

This is a good reason why Tesla cars are folly. This is why electric vehicles won't work. I'll copy in most of a comment I made a few days back. Let's say tomorrow some grad student gets fusion going at a very low price. The best way to use this to power cars would be to use it to create a fuel with a high energy density. If you had 'free energy' you'd extract C02 from the atmosphere and turn it into a hydrocarbon. For more info look at: http://en.wikipedia.org/wiki/Energy_density http://en.wikipedia.org/wiki/Energy_density and this interview with Nobel Prize winning Physicist Robert Laughlin http://www.econtalk.org/archives/2010/08/laughlin_on_the.htm.. http://www.econtalk.org/archives/2010/08/laughlin_on_the.htm.... the key quote is: "The ones that are technically trained get it right away: hydrocarbons, which we burned today have the greatest energy density possible of all fuels. Things that have carbon in them. Will people fly airplanes? Usually people say yes for the same reasons. Well, how are you going to make the airplanes fly? Battery. Batteries are pretty heavy. Oh--you can't have airplanes unless you have hydrocarbon fuels. You could in theory do it with hydrogen, but it's highly dangerous, noxious fuel. Quantum-mechanically, we know the energy content of those fuels is optimal. There will never be anything that beats them." A massive breakthrough in energy density for batteries might be possible but it's unlikely. Huge resources have been put into improving batteries and while they have improved it's not been enough to get near the energy density of hydrocarbons.

Mvandenbergh 14y ago
Most people miss the difference between hydrocarbon fuels as energy source* and as energy carrier. If you make HC fuels from atmospheric or oceanic carbon, you have a nice closed cycle. (*) Technically fossilised solar energy of course.
ta12121 14y ago
No. Electrolysing water to make H2 and extracting CO2 from the environment, and then synthesizing hydrocarbons from them, is extremely energy inefficient. Sure, theoretically, it can be done, and maybe one day it could even be done efficiently. But Tesla is making battery-electric cars that work today. The military does not care about efficiency because they have nuclear reactors on their ships and their goal is to not to have to transport liquid fuel.
- sien 14y ago
  If they can hit $3 / gallon why does it matter? Tesla's cars are wildly price inefficient because they cost $100K. For 10K you can get a decent car that has 4 times the range. http://en.wikipedia.org/wiki/Tesla_Roadster http://en.wikipedia.org/wiki/Tesla_Roadster How many gallons of fuel can you get for 90K? They are nice toys for rich people. Perhaps there is a market for that. Good luck to them. But for mass transit unless you can get the price of the batteries to plummet it just does not work.
  - rhizome 14y ago
    In non-currency terms, this sounds a lot like Unix-Windows arguments 15 years ago. If you can bundle Windows, why does it matter what computer you get? For 1/10 the price you can get a great Windows PC with 10 times more software. Tesla Roadster being like an SGI or Solaris box, Linux/FreeBSD is just for snobby nerds who like to tinker. Unless you can make it easier to use it just does not work.
  - wisty 14y ago
    Telsa cars are expensive for the same reason Ferraris are - they target people who want bling. A mass-produced commuter could be much cheaper, but there's a huge risk. Tesla aims to reduce the risk by validating the market, solving technical problems, creating infrastructure (recharge stations) and solving social problems (convincing people that range doesn't always matter, and educating them on the strengths and weaknesses of electric cars). A low total-cost (including fuel and maintenance) electric car can probably be produced, but it's not the Tesla's top model.
  - ta12121 14y ago
    $3 a gallon is what the fuel costs today when it comes straight out of the ground. Claiming to be able to build and run a nuclear reactor and then synthesize the fuel through multiple energy inefficient steps all for the same price is a pipe dream.
    - deleted 14y ago
      [deleted]
comicjk 14y ago
Lithium-air batteries (an immature technology, certainly) have an energy per gram 3.5 times less than gasoline's. But electric motors are about 3.5 times more efficient than internal combustion engines. And the technology to produce synthetic fuels from CO2 is pretty much as far from mass scale as lithium-air batteries. I agree that we will need carbon-based fuels for jet engines, but as for cars, the physics and economics are by no means as favorable as you represent.
lumberjack 14y ago
Your argument is only balanced on that one premise of Fusion or free energy, both of which are still vaporware and will be for decades if not centuries to come. Have you considered that maybe electric cars will fill the gap between now and then if ever? And you consider free energy a possibility but advancement in battery technology too far fetched. I don't agree at all.
dalke 14y ago
"Let's say tomorrow some grad student gets fusion going at a very low price. The best way to use this to power cars would be to use it to create a fuel with a high energy density." That is incorrect. If the fusion source is compact, and can produce a lot of instantaneous electrical power, and is quick to throttle up and down, then a "Back to the Future"-style Mr. Fusion would be the best way to power cars. Energy density isn't the only factor. There's also a question of infrastructure. Electrical distribution has few moving parts, while extracting C02 from the atmosphere to make fuel and distributing the fuel has many more mechanical parts. A fusion plant which could produce 50 kW, weighed 2 tons, and could be installed in the back yard of a home would mean that a house could be off the grid and still have power left over to charge the car, while using intermediate hydrocarbon storage would mean trips to fill the car, or heating oil, or cooking gas. So while I completely agree that airplanes will not be powered by batteries, I don't think that energy density is the only factor to consider in the economics equation.
- stcredzero 14y ago
  > That is incorrect. If the fusion source is compact, and can produce a lot of instantaneous electrical power, and is quick to throttle up and down, then a "Back to the Future"-style Mr. Fusion would be the best way to power cars. There's also safety to consider.
  - sophacles 14y ago
    On top of that, reliability. To have a large plant with a high mechanical complexity which can justify dedicated maintenance workers to help manage complexity and the results of part wear etc is likely able to achieve the same or higher reliability than a backyard unit, in TCO terms anyway.
    - dalke 14y ago
      So I think you both agree with me that it's not necessarily the case that a hypothetical fusion power source or free energy source is best used to produce hydrocarbons for distribution and downstream use. Regarding the comment of sophacles, power distribution is part of the economic factor. It may be that the central plant is much more reliable than a backyard plant, but the power grid - subject to thunderstorms, ice, tree falls, backhoes, curious squirrels, and so on - makes the overall power supply system less reliable than a backyard fusion plant.
Dn_Ab 14y ago
Very good point. But it doesn't make Tesla cars a folly so much as put a strong constraint on their long term economic viability: the invention of fusion power or some other method of making energy abundant turned to making hydrocarbons effectively renewable. But that could be decades away, timeline of practical viability is effectively unknown. Considering how speculative this notion of really cheap energy is (for now), I still think Tesla is a good bet. On the event of the floor dropping off the prices in energy markets, there will be few that are dependent on large energy barriers to entry that will emerge unscathed. It is also effectively win-win. If such a thing becomes possible the costs in much of production will cut very drastically and the potential of things now open would be just incredible. So much of expense is due to energy constraints.
confluence 14y ago
You are wrong. Electric engines run at 92% efficiency. Car engines run at ~15%. So energy density need not reach equivalence. That physicist is wrong too (Nobel prizes don't mean you aren't wrong - it just means people listen to you more) - jet engines on planes require oxygen to work - hence capped at ~10 km altitude with massive drag causing ineffecient travel. 10 years till battery tech reaches complete parity for lowest denominator cars, and 7 years before we start to see hyper sonic electric passenger jets being tested way up in the upper atmosphere (no oxygen needed, go as high and fast as you want - London - LA in a few hours - space views - cheap power).
- jrabone 14y ago
  What? 10 years until battery technology has advanced to the point of parity? Gasoline has an energy density of 132 MJ/US gal, or say 1500 MJ on a full small tank. Modern engines hit 30% thermal efficiency, but then there are drive train losses etc, so I'll give you the 15% as an absolute worst case, AND give you a 100% efficient electric motor / drive train. Therefore your car needs to provide 225 MJ of stored energy for parity. The best commercially-available Li-ion battery has an energy density of around 245 Wh/kg, or ~ 880 kJ/kg. Therefore you need at least 255kg of conventional batteries for motive energy parity (ie. not counting heat/AC/light etc.). The equivalent in gasoline (0.77 kg/l), weighs 35 kg. You are asking for nearly a ten-fold increase in usable energy density in battery technology in ten years, at price-parity with gasoline, and with the charging infrastructure to support it. I don't think it's going to happen - assuming lithium-air batteries ARE commercialised on that time scale, the cost of charging that kind of energy in reasonable time, safely, is going to be the real problem here. Every gas station is going to need its own nuclear power plant!
  - confluence 14y ago
    I'm assuming nuclear fusion is viable with the development of the ITER and DEMO plants in the South of France. If they aren't viable - I'm calling time of death on the world.
    - DennisP 14y ago
pigboy 14y ago
Energy density is a critical issue for aircraft because lift/drag ratios are capped at around 15 to 30. For every 15-30 N of fuel weight, you must supply at least 1 N of additional thrust (which translates to power, once you multiply by speed). Cars, on the other hand, experience a combination of aerodynamic and powertrain drag and rolling resistance, of which only (mostly?) the rolling resistance depends on mass. The typical coefficient of rolling resistance is about 10x better than the typical L/D ratio for aircraft (if I believe Wikipedia). Hence, road vehicles are 10x less sensitive to energy density than aircraft. So a statement that electric vehicles won't work is nonsense, without considering how sensitive the different vehicles are to fuel mass.

by sien 14y ago

Mvandenbergh 14y ago

Most people miss the difference between hydrocarbon fuels as energy source* and as energy carrier. If you make HC fuels from atmospheric or oceanic carbon, you have a nice closed cycle. (*) Technically fossilised solar energy of course.

ta12121 14y ago

No. Electrolysing water to make H2 and extracting CO2 from the environment, and then synthesizing hydrocarbons from them, is extremely energy inefficient. Sure, theoretically, it can be done, and maybe one day it could even be done efficiently. But Tesla is making battery-electric cars that work today. The military does not care about efficiency because they have nuclear reactors on their ships and their goal is to not to have to transport liquid fuel.

sien 14y ago
If they can hit $3 / gallon why does it matter? Tesla's cars are wildly price inefficient because they cost $100K. For 10K you can get a decent car that has 4 times the range. http://en.wikipedia.org/wiki/Tesla_Roadster http://en.wikipedia.org/wiki/Tesla_Roadster How many gallons of fuel can you get for 90K? They are nice toys for rich people. Perhaps there is a market for that. Good luck to them. But for mass transit unless you can get the price of the batteries to plummet it just does not work.
- rhizome 14y ago
  In non-currency terms, this sounds a lot like Unix-Windows arguments 15 years ago. If you can bundle Windows, why does it matter what computer you get? For 1/10 the price you can get a great Windows PC with 10 times more software. Tesla Roadster being like an SGI or Solaris box, Linux/FreeBSD is just for snobby nerds who like to tinker. Unless you can make it easier to use it just does not work.
- wisty 14y ago
  Telsa cars are expensive for the same reason Ferraris are - they target people who want bling. A mass-produced commuter could be much cheaper, but there's a huge risk. Tesla aims to reduce the risk by validating the market, solving technical problems, creating infrastructure (recharge stations) and solving social problems (convincing people that range doesn't always matter, and educating them on the strengths and weaknesses of electric cars). A low total-cost (including fuel and maintenance) electric car can probably be produced, but it's not the Tesla's top model.
- ta12121 14y ago
  $3 a gallon is what the fuel costs today when it comes straight out of the ground. Claiming to be able to build and run a nuclear reactor and then synthesize the fuel through multiple energy inefficient steps all for the same price is a pipe dream.
  - deleted 14y ago
    [deleted]

comicjk 14y ago

Lithium-air batteries (an immature technology, certainly) have an energy per gram 3.5 times less than gasoline's. But electric motors are about 3.5 times more efficient than internal combustion engines. And the technology to produce synthetic fuels from CO2 is pretty much as far from mass scale as lithium-air batteries. I agree that we will need carbon-based fuels for jet engines, but as for cars, the physics and economics are by no means as favorable as you represent.

lumberjack 14y ago

Your argument is only balanced on that one premise of Fusion or free energy, both of which are still vaporware and will be for decades if not centuries to come. Have you considered that maybe electric cars will fill the gap between now and then if ever? And you consider free energy a possibility but advancement in battery technology too far fetched. I don't agree at all.

dalke 14y ago

"Let's say tomorrow some grad student gets fusion going at a very low price. The best way to use this to power cars would be to use it to create a fuel with a high energy density." That is incorrect. If the fusion source is compact, and can produce a lot of instantaneous electrical power, and is quick to throttle up and down, then a "Back to the Future"-style Mr. Fusion would be the best way to power cars. Energy density isn't the only factor. There's also a question of infrastructure. Electrical distribution has few moving parts, while extracting C02 from the atmosphere to make fuel and distributing the fuel has many more mechanical parts. A fusion plant which could produce 50 kW, weighed 2 tons, and could be installed in the back yard of a home would mean that a house could be off the grid and still have power left over to charge the car, while using intermediate hydrocarbon storage would mean trips to fill the car, or heating oil, or cooking gas. So while I completely agree that airplanes will not be powered by batteries, I don't think that energy density is the only factor to consider in the economics equation.

stcredzero 14y ago
> That is incorrect. If the fusion source is compact, and can produce a lot of instantaneous electrical power, and is quick to throttle up and down, then a "Back to the Future"-style Mr. Fusion would be the best way to power cars. There's also safety to consider.
- sophacles 14y ago
  On top of that, reliability. To have a large plant with a high mechanical complexity which can justify dedicated maintenance workers to help manage complexity and the results of part wear etc is likely able to achieve the same or higher reliability than a backyard unit, in TCO terms anyway.
  - dalke 14y ago
    So I think you both agree with me that it's not necessarily the case that a hypothetical fusion power source or free energy source is best used to produce hydrocarbons for distribution and downstream use. Regarding the comment of sophacles, power distribution is part of the economic factor. It may be that the central plant is much more reliable than a backyard plant, but the power grid - subject to thunderstorms, ice, tree falls, backhoes, curious squirrels, and so on - makes the overall power supply system less reliable than a backyard fusion plant.

Dn_Ab 14y ago

Very good point. But it doesn't make Tesla cars a folly so much as put a strong constraint on their long term economic viability: the invention of fusion power or some other method of making energy abundant turned to making hydrocarbons effectively renewable. But that could be decades away, timeline of practical viability is effectively unknown. Considering how speculative this notion of really cheap energy is (for now), I still think Tesla is a good bet. On the event of the floor dropping off the prices in energy markets, there will be few that are dependent on large energy barriers to entry that will emerge unscathed. It is also effectively win-win. If such a thing becomes possible the costs in much of production will cut very drastically and the potential of things now open would be just incredible. So much of expense is due to energy constraints.

confluence 14y ago

You are wrong. Electric engines run at 92% efficiency. Car engines run at ~15%. So energy density need not reach equivalence. That physicist is wrong too (Nobel prizes don't mean you aren't wrong - it just means people listen to you more) - jet engines on planes require oxygen to work - hence capped at ~10 km altitude with massive drag causing ineffecient travel. 10 years till battery tech reaches complete parity for lowest denominator cars, and 7 years before we start to see hyper sonic electric passenger jets being tested way up in the upper atmosphere (no oxygen needed, go as high and fast as you want - London - LA in a few hours - space views - cheap power).

jrabone 14y ago
What? 10 years until battery technology has advanced to the point of parity? Gasoline has an energy density of 132 MJ/US gal, or say 1500 MJ on a full small tank. Modern engines hit 30% thermal efficiency, but then there are drive train losses etc, so I'll give you the 15% as an absolute worst case, AND give you a 100% efficient electric motor / drive train. Therefore your car needs to provide 225 MJ of stored energy for parity. The best commercially-available Li-ion battery has an energy density of around 245 Wh/kg, or ~ 880 kJ/kg. Therefore you need at least 255kg of conventional batteries for motive energy parity (ie. not counting heat/AC/light etc.). The equivalent in gasoline (0.77 kg/l), weighs 35 kg. You are asking for nearly a ten-fold increase in usable energy density in battery technology in ten years, at price-parity with gasoline, and with the charging infrastructure to support it. I don't think it's going to happen - assuming lithium-air batteries ARE commercialised on that time scale, the cost of charging that kind of energy in reasonable time, safely, is going to be the real problem here. Every gas station is going to need its own nuclear power plant!
- confluence 14y ago
  I'm assuming nuclear fusion is viable with the development of the ITER and DEMO plants in the South of France. If they aren't viable - I'm calling time of death on the world.
  - DennisP 14y ago

pigboy 14y ago

Energy density is a critical issue for aircraft because lift/drag ratios are capped at around 15 to 30. For every 15-30 N of fuel weight, you must supply at least 1 N of additional thrust (which translates to power, once you multiply by speed). Cars, on the other hand, experience a combination of aerodynamic and powertrain drag and rolling resistance, of which only (mostly?) the rolling resistance depends on mass. The typical coefficient of rolling resistance is about 10x better than the typical L/D ratio for aircraft (if I believe Wikipedia). Hence, road vehicles are 10x less sensitive to energy density than aircraft. So a statement that electric vehicles won't work is nonsense, without considering how sensitive the different vehicles are to fuel mass.