Last week was all about the bright lights and smoke machines at the launch of the Tesla electric truck, but this week there’s a more sobering questioning of the Tesla truck: fact or fiction. The Tesla founder, Elon Musk, is a master of hyperbole; his style is all about making big claims and then trying to live up to them.
More sober heads have been dissecting the information that came along with the loud music and baying fans in an aircraft hangar in California last week. The presentation was big on broad unprovable claims but light on cold hard numbers and real undeniable facts.
Smarter heads than the team at Diesel News have been crunching the numbers and trying to work out just what Musk was talking about and how much of it is an undeniable fact. We are dealing with the laws of physics here and they may be complex, but they are difficult to break.
The first question has to be about the batteries and the series of assertions made about the electric truck’s range and acceleration. The claim by Musk tells us the Tesla semi has a range of 800km and will consume 1.25 kilowatt hours per kilometre (kWh/km).
Cambridge University’s Professor David Cebon, recognised as an expert in the field, has calculated this range will require 1,000kWh of energy and this will need a 1,300kWh battery to deliver this. Current lithium ion battery technology costs $150 per kWh and should fall to $100 per kWh by 2021. This puts the cost of a battery at $130,000.
This comes close to the cost of a current semi prime mover in the US truck market. Tesla has announced its vehicle will enter the market at $150,000.
A lithium ion battery has a capacity to store energy and current technology enables them to run at between 0.1 and 0.25 kWh per kilogram of battery. This runs out as a battery capable of meeting the Tesla claim weighing between 5.2 and 13 tonnes. This compares with the overall weight of a Cummins X15 engine at 1,430kg. One thousand litres of diesel weighs 832kg and will get a relatively inefficient diesel-powered semi over twice the distance claimed for the Tesla’s range.
Chris Winkler from the University of Michigan’s Transport Research Institute has crunched the numbers on a quick battery-charging system. He looks at a typical US truck fuel capacity of 200 US gallons (757 litres), which translates to 2,785kWh of energy (if you assume a 37 per cent efficiency for diesel engines). This is the equivalent of 12.8 years of electricity consumption of a typical US household.
The other issue – carbon emissions – gets his attention. The 37 per cent efficiency of a diesel engine to get the truck to its destination can be compared to the efficiency of power stations to create the electricity to power the batteries at 33 per cent for coal or nuclear or 42 per cent for natural gas.
No one involved in this debate is saying electric trucks are a bad idea – they are a good idea. The point many industry experts are making concern overblown claims by Musk, which may create an unfulfilled expectation about what electric trucks can deliver in the short term.
There are real world electric trucks on the road now and they are delivering efficiencies.