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.