Feasibility of a Liquid Air Powered Autonomous Truck

I had previously proposed liquid air powered autonomous cargo trucks that operate on a dedicated suspended bridge highway. Recently, I made some calculations on the feasibility of a liquid air powered vehicle based on the theoretical values with acceptable correction factors. The results look promising. I would like to repeat again that the performance of liquid air cannot beat a combustion engine. However, it performs better than battery operated alternatives.

Theoretical energy density of liquid nitrogen at atmospheric pressure and 27 °C ambient temperature is about 213 W·h/kg, while typically only 97 W·h/kg can be achieved under realistic circumstances. This compares with 100–250 W·h/kg for a lithium-ion battery and 3,000 W·h/kg for a gasoline combustion engine running at 28% thermal efficiency (Liquid nitrogen engine). Most notable advantage of liquid air is its Carnot efficiency. At 27 °C ambient temperature it is 74.3 %; at -16 °C ambient temperature it is 70 %. At such low temperatures, batteries have no chance and even diesel engines struggle to operate due to freezing of diesel.

I made my calculations for a full-sized container carrying truck. The weight of the truck with full fuel tank was 7300 kg (600kg fuel), the trailer was 6000 kg, the payload was 16,000 kg. I set the energy density of liquid air to be 1 / 20 of a diesel engine. In order to achieve half the range of a diesel truck it would require 6000 kg of liquid air. However, autonomous trucks have advantages in terms of weight because they can simply be a motorized trailer. Additionally, the cryogenic tanks can be designed to be used as the chassis. As a result, the liquid air powered autonomous container carrier can accommodate such a huge fuel tank with the same weight as a traditional truck with a trailer for half the range. One more advantage of such a huge fuel tank is, as it is depleted the truck gets much lighter compared to a diesel truck and its fuel consumption gets lower.

The prerequisites for this idea are light weight composite fuel tanks, light weight and high thermal conductive heat exchangers to create pressure that would turn the wheels. Aluminum alloy heat exchangers with carbon fiber can be a solution for that.