EVwire brief: During the Semi’s rollout event, Tesla VP of Vehicle Engineering Lars Moravy and Semi Program Lead Dan Priestley explained how the Semi’s thermal system was developed, from the days of the original prototype to its current production version.
As per Priestley, Tesla's engineers first tried to solve the Semi's thermal system by copying what already worked. The original plan was to take the thermal system shared by the Model 3 and Model Y, which was already proven across more than 10 million vehicles and billions of miles, and simply install two of them in the truck.
That approach didn't hold up. Tesla found the doubled-up system wasn't actually capable enough for Semi, so the company built an all-new indirect thermal system instead, designing it alongside Cybercab so one architecture could serve both the company's most efficient vehicle and its biggest one, with only small changes to the cooling loop.
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That common architecture also gives Tesla the benefit of components already used across its vehicle lineup. Tesla said its vehicles use roughly two or three coolant pumps each, meaning the company has produced tens of millions of these pumps. The Semi uses the same pumps, which Tesla said provides an established supply and distribution system as well as components with extensive real-world use.
“Those pumps are the same pumps we have all over the world. And that means not only do you get a very reliable part, a very available part, but you get to leverage that distribution system as well.
The indirect design also changes how refrigerant is handled. Rather than running refrigerant lines from the thermal system to the front of the Semi, the system leaves the factory sealed and charged with refrigerant and circulates coolant through the vehicle. Tesla said that eliminates the AC and refrigerant lines that would otherwise need to run through the truck, reducing potential leak or damage points and simplifying service.
As described by Dan Priestley:
“One thing you might notice about this thermal system is that there's no AC lines, there's no refrigerant lines. And that's the beauty of the indirect thermal system is it comes from the factory fully charged, sealed with refrigerant and it just exchanges coolant. It doesn't actually run refrigerant up to the front of the vehicle. So there's no AC lines to worry about damaging or leaking or having to do any work in the shop. It's a great tight integrated system straight out of the factory.”
Overall, the Tesla Semi’s Megamanifold connects the battery, drive unit and cabin into the same thermal system. Instead of treating heat as something that simply needs to be removed or added, the system can move heat between different parts of the vehicle. Heat generated in one area can be recovered and directed somewhere it is needed, such as using heat removed from the cabin to warm the battery or drive unit.
That approach allows the Semi to reuse thermal energy rather than treating heating and cooling as separate jobs. Tesla said the result is a more efficient system built around a common architecture it can use across different vehicles.
“If you can't tell, we're kind of ruthless about every watt-hour that we chase in these things because there's this wonderful compounding effect is that if you make the vehicle more efficient, that means it's less battery you need to do the same amount of work, which means that you can take battery out of the vehicle, which is lower cost, and lower mass.”
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Context:
The scale of Tesla's Semi customer base was already on display before the event: drone shots of the factory lot showed customer trucks bearing PepsiCo, US Foods, Einride, LTS, Nevoya, OK Produce, ABF Freight, DHL, WattEV, IMC Logistics and HMD branding, all staged for delivery.
That momentum carried into the days before the rollout too. ZET SCALE announced a 2,500-truck electric Class 8 program two days prior, with Tesla as primary OEM across 10 freight hubs, and Forum Mobility separately rolled out four new California depots adding 30 MW of heavy-duty charging capacity, three of which will host public Megachargers, with over 330 Semis already under contract for fleet offtake at its FM Santa Fe site in Rancho Dominguez.
Source: Tesla Semi on X
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