The problem is energy density

Friday, November 17th, 2017

Long-haul trucking is an odd choice for Tesla. The problem is energy density:

Batteries take up far more space and weight for a given output of energy than gasoline and diesel. That issue is becoming irrelevant in lighter vehicles like cars and smaller vans because they don’t require much power. But it looms large when it comes to the heavy-duty longer-distance trucks that consume about half of road freight fuel, and are expected to see the biggest demand growth.

Energy Density

Take a look, for instance at Daimler AG’s Urban eTruck, the first fully electric heavy-duty vehicle to go into production earlier this year. The 2.5-metric-ton battery alone on this beast weighs as much as a Chevrolet Suburban, one of the largest SUVs on the road. Furthermore — as the name indicates — it’s only intended for deliveries within cities, with a maximum range of 200 kilometers. That’s not going to do much damage to long-distance routes: A typical semi-trailer can carry enough fuel to travel at least five times that distance.The specifications emerging for the Tesla Semi suggest it may be able to improve on that, with a range of about 800 kilometers when carrying a 36-ton maximum load. There’s no word yet about the weight of the Semi’s battery, but it would have to be colossal to achieve those sorts of specs. That’s probably not the best route to energy efficiency, given that about 25 percent to 30 percent of the time trucks are driven empty. A significant slice of the Semi’s energy will be spent hauling around its massive power plant.

That explains why the numerous competitors to the Semi already out there are mainly focused on shorter-range urban logistics networks. It’s going to require technological breakthroughs — such as the development of commercial lithium-air cells, which could have gasoline-style energy densities — for batteries to really eat into the oil consumed by long-haul trucking and aviation.


  1. Bill says:

    This discussion is interesting but moot not only because the energy density specs are irrelevant, but it also ignores the network of Megachargers that Tesla will install.

    Who cares about energy density when you realize that the Tesla Semi’s standard size cab without a trailer – just the truck part – can go from 0 to 60 in five seconds? Pulling the maximum load legal on US highways, 80,000 pounds, it does 0-60 in 20 seconds. Density, schmensity.

    The battery capacity is more than big enough for long-haul trucking. My Tesla has “only” about 250 miles of range, but there are Superchargers every 150 miles (or less) everywhere I need to go, and I can pick up 150 miles of charge in 30-40 minutes. Tesla says they can provide their usual 80% charge to a truck in thirty minutes, which is barely enough time for a decent stop.

    Just like a network of Superchargers is Tesla’s unbeatable ace in the hole in the car market, its Megachargers makes trucker “range anxiety” disappear.

  2. Wang Weilin says:

    Electric cars are charged via the grid by coal, natural gas or hydro. They are in essence coal and NG powered. Besides energy densities, the inefficiencies are horrible. Add to that the unaffordable prices for most people and tax rebates to the ‘rich’ who buy electrics. The electric car industry is a house of cards that would collapse without gov’t support.

  3. Bruce says:

    “The electric car industry is a house of cards that would collapse without gov’t support.”

    Agreed, for now. I want a motorcycle with big batteries for an electric scooter option. For going five miles or so inside a city, or for the first six blocks in a residential neighborhood before you open the pipes up. Or, killer app here, to get the damn thing moving when it’s too cold to start but the streets are still dry and safe. Bikers tend to like to fiddle, and the smart ones brag to the rest of us. Something good might well happen.

  4. Albion says:

    Isn’t the whole thing about energy that the more it is converted the more it loses, er, energy?

    Converting coal, gas and oil into electricity (the logistics and trucking businesses cannot afford to wait for natural supply sources to be there when they need them) and then piping it with the attendant loss through transfer to plug-in points to recharge batteries doesn’t seem like a good idea.

    I know lots of people get excited about electric vehicles (I have a relative who almost swoons at the very thought of electric cars everywhere) but they will have to go some to beat gasoline and even diesel.

  5. Bill says:

    I live in Michigan so the electricity to power my Tesla is about 30% nuclear and 30 percent assorted renewable. Line losses are on the order of 0.5 to 1.0 percent per hundred miles from a power plant via high tension lines. If line losses bother you, I assume you are piping diesel to your house and making your own electricity? Losses from municipal water pipes are typically 40%, so I guess you’re living on rainwater falling on your house, or possibly condensing it from the air with the power you are generating from your basement? (OK, that was snarky, sorry.)

    Electric vehicle subsidies (federal and state) for automakers are hard to estimate, certainly they amount to billions of dollars per year for as long as they are in force, with no equivalent for ICE vehicles.

    The International Monetary Fund estimates the total global incentives to the oil and gas industry amount to $5.3 trillion per year, compared to about $120 billion for renewables.

    Anyway, I think there’s a good case for seeing if there’s a way to do electric vehicles. I’d also say that if you drove a Tesla for a day, you’d never go back to those noisy, slow ICE cars.

  6. Wan Wei Lin says:

    Bill: Gov’t subsidies of electric vehicles means as a taxpayer I’m paying you to drive a car I can’t afford. You’re welcome.

    PS: Same as all subsidies. Get rid of all of them. No deductions or subsidies for anything or anybody.

  7. Bill says:

    I don’t like subsidies either, but now people can buy a Chevy Volt for $35k and get $7.5k subsidy as well, $27.5k is a price most Americans can afford for a car. You’re welcome. In the ’80′s I paid the equivalent of $10k for laptop computers which helped (along with subsidies to companies like Intel) to bring about $150 dollar laptops. You’re welcome.

    As taxpayers we’re all helping to pay for stuff we personally might never use. Google “corporate welfare” to see the extent of the problem of government subsidies; Tesla’s share of US government largesse is minuscule.

    If I had a choice, though, I’d vote to get rid of all subsidies, too. Let individuals decide how to spend their own money.

  8. Sam J. says:

    The subsidies are pulling in massive amounts of money into better batteries. The guy who invented the lithium battery now has a new one WAY better that is solid state and runs on sodium. He makes this work cost will plummet but without a large market we get none of this. I’m for electric cars for defense and individual freedom. Ecotopia I could care less about.

  9. Bruce says:

    “The subsidies are pulling in massive amounts of money into better batteries.”

    Yes, that’s a big deal. Jerry Pournelle kept saying we really need better batteries. He also kept saying a battery is not a power source, but batteries are still important.

  10. Baduin says:

    Electric trucks are possible and important. But they have to work like electric trains — you have to electrify the highways with overhead wires. Batteries would be used for short range movement to and from highway and in case of problems with wires.

    In other words, they would work like hybrid trolleybuses.

    Of course, this would require a serious government program. As for now, the electric car efforts are half scam, half technology development program.

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