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The Truth About The Tesla Semi-Truck

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07:20   |   Dec 15, 2017

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The Truth About The Tesla Semi-Truck
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  • This video was made possible by you,
  • and my Patreon supporters.
  • Without you, this channel would not be possible.
  • Thank you!
  • Last month, Elon Musk unveiled a curiously anticipated Tesla truck.
  • A vehicle that most people will never step inside or drive.
  • Yet it was met with hysterical screaming and cheers.
  • The power of Elon Musk to generate hype for his next project is the envy of CEOs across the world.
  • So, what is the big deal about a truck,
  • and why is creating a battery-powered truck such an impressive feat?
  • In the U.S. alone, the trucking industry contributes to about
  • 23% of the total greenhouse gas emissions,
  • equating to 1.475 million metric tons of carbon dioxide.
  • Converting this industry to renewable energy sources
  • would be a huge win in our battle against climate change.
  • But this isn't just a matter of throwing some batteries in a truck,
  • adding some motors, and marketing it to bejesus using Elon Musk's hyper powers.
  • There are actual technical issues we need to overcome first:
  • the most prevalent of which is the energy density of the batteries,
  • which is the amount of energy provided per kilogram of their own weight.
  • Vehicles like semi-trucks are categorized as Class A vehicles,
  • bound to a maximum weight of 36 tons by the Federal Highway Administration.
  • This weight includes the weight of the truck and payload,
  • so any increase in the truck weight
  • will result in a decrease in payload– the part that pays the bills.
  • For an energy source like batteries,
  • which have a low energy density when compared to fossil fuels,
  • this creates issues when attempting to create a vehicle
  • that will offer a value proposition to the trucking industry.
  • Let's assume our truck, without batteries, will weigh about 7 tons.
  • This is based on current trucks without an engine.
  • That leaves us 29 tons to play with
  • to figure out how much of our weight to assign to batteries,
  • and this is where designers need to make a decision:
  • include more batteries, and the truck will have a greater range,
  • but will be able to carry less payload.
  • Or create a smaller battery pack, which sacrifices range for a greater payload.
  • A diesel truck can carry over 20 tons with a range of 1,500 km, or 900 mi.
  • We know Tesla will be creating two variants of its truck: a 300-mile and a 500-mile variant.
  • And while Elon hyped the 0-60 acceleration that no truck driver is ever going to use
  • unless they want to be fired the moment they arrive at the depot,
  • they left out the one crucial bit of information everyone in the trucking industry was waiting for:
  • the weight of the empty truck, which will determine exactly how much cargo the truck can carry,
  • and thus how quickly a buyer will get a return on investment.
  • I found the purposeful secrecy behind this information incredibly suspicious,
  • but it may just be a case of Elon wanting to wait another 2-3 years,
  • with possible energy density improvements on the horizon, to make that announcement.
  • The continued improvement of energy density was the driver of this new era of electrical vehicles,
  • and Tesla has been on the vanguard of many of the technological advancements,
  • and it's in their best interest to do so.
  • There really isn't any proprietary technology in Tesla that someone like BMW or Ford couldn't copy,
  • and quite frankly, improve upon.
  • Tesla, without their own battery production, is really just a very well-marketed brand.
  • So let's calculate the energy these batteries will need to provide these two trucks,
  • and more importantly, how much they will weigh.
  • To do this, we first need to estimate how much energy this truck will consume for a given range.
  • This is relatively easy. "Energy" is simply given as "power" by 'time".
  • We can calculate "time" by dividing the range by the average speed.
  • And "power" equals "force" times "velocity".
  • We can now swap in the power components for this equation we made earlier.
  • And, voila, we have our equation for the battery capacity needed for the truck.
  • Okay,
  • jokes aside, this an equation taken from an absolutely fantastic paper
  • by Shashank Sripad and another lad who needs less syllables in his name,
  • which goes into depth in this problem.
  • But I'll give you a quick rundown of its components.
  • To adequately calculate the force acting on the vehicle,
  • we first need to calculate the force required to overcome inertia,
  • that is, how much force it will take to get the vehicle moving,
  • which is this part of the equation.
  • This takes into account the efficiency of the electric engines and brakes
  • and the energy recovered from regenerative braking.
  • Now, we need to calculate the forces acting to slow the vehicle down
  • such as drag, the rolling friction on the wheels, and gravity as the vehicle travels uphill.
  • Musk specified that the range for the vehicle was calculated on a flat road,
  • so this component goes to "zero".
  • So if you work on mountainous roads, this truck may not be for you.
  • From the event last month, we know that the truck has an astounding coefficient of drag of 0.36-
  • that's slippier than a Bugatti Chiron-
  • thanks to the lack of air intakes to cool the engine.
  • We will take the mean rolling resistance of the truck tires at 0.0063,
  • and the average speed at 50mph
  • (this accounts for city driving too),
  • and with the average acceleration and deceleration at 0.112 m/s²,
  • and a frontal area of 7.2 m².
  • The rest are constants that you don't particularly need to worry about for this example,
  • but you can check the full calculations in the description
  • where I've included an interactive website that we created
  • so you can easily change these variables yourself to see how they affect the vehicle.
  • With this tool we can see that the 300-mile variant would need a 550-600 kWh batteries,
  • and the 500-mile variant would require 900-1000 kWh.
  • With current batteries' energy densities and prices, these would weigh 4.7 and 7.9 tonnes,
  • and cost $108,000 and $180,000 respectively.
  • These are the two most important metrics for any company considering buying this truck,
  • as it determines the exact return-on-investment time.
  • The batteries for the 500-mile version are going to be more expensive than a traditional truck alone
  • while having a shorter range and smaller hauling capacity.
  • That's going to make the return-on-investment time longer,
  • even if the operating cost per mile is 20% lower than a conventional diesel semi-truck.
  • But profitability is not everything in this world.
  • This truck will use approximately 25% the energy of a conventional truck,
  • thanks to the extremely efficient engines,
  • and much of this will be provided by renewable energy.
  • This truck has the potential to drastically reduce the greenhouse gas emissions of the trucking industry.
  • Tesla leading the way on this technology and ignoring skeptics like me, while risking bankruptcy
  • for the sake of improving the planet is exactly why I admire Elon Musk so much in the first place.
  • Honestly, I came into this video expecting the truck to be a deeply flawed technology,
  • After the event, I ranted on Twitter about how suspicious it was
  • that Musk didn't unveil the empty weight of the vehicle.
  • I honestly thought the whole event was created to stir up hype
  • and generate funds for a cash-poor company through pre-orders.
  • I expected my calculations to confirm my preconceived ideas,
  • but I've never been so glad to be wrong.
  • There are many other factors that will affect this truck,
  • but you can investigate them on our site at battery.real.realengineering
  • We can see how adding a 5% grade hill for 5% of the journey will increase the battery capacity required
  • for the 500-mile range by more than 200 kWh
  • and the weight of the truck by almost 2 tonnes
  • and increase the price by $44,000.
  • Go ahead and play around with the tool yourself, and if you found it useful
  • please consider supporting the channel on Patreon.
  • because this video, along with the website,
  • was made possible by funding from my Patreon community.
  • Funding from Patreon will always go straight back into this channel,
  • whether it's hiring more web developers to create cool companion sites like this,
  • or hiring animators and researchers to help the production quality and quantity of this channel.
  • Ultimately, with your help, I want to make this the best science documentary channel on the internet.

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