Michael Dearman hauled an invention out of deep-freeze to fix refrigeration
Click here to read an earlier piece I wrote about the Dearman engine for The Economist
Michael Dearman is preparing for the realisation of a family dream. Almost 40 years ago, his father, British inventor Peter Dearman, came up with the idea of an engine powered by liquid nitrogen. Next spring, the prototype will finally be tested on public roads — not in a car, as Dearman intended, but as a replacement for the auxiliary engines bolted on to the side of refrigerated trucks.
“I have seen the engine grow from an idea in my father’s head to a piece of machinery,” says 34-year-old Dearman, head of development at the company named after his father, now 64.
Liquid nitrogen engines have been a goal since nitrogen was first liquefied in the 1880s, but progress was slowed by the challenges of building engines to use fuel at -196°C — nitrogen’s boiling point. Dearman says his company now found a niche for its tech by using his father’s engine to deliver cold and power at the same time.
The engine produces power like a petrol engine, with liquid nitrogen expanding to drive a single piston. Before the nitrogen gets to the engine, however, it has absorbed the heat of the refrigerated compartment through a heat exchanger. This latent heat changes the nitrogen into a gas without any increase in temperature. It is then injected into the cylinder to mix with a water-glycol fluid, which enables the gas to expand at a consistent and efficient rate, a feat previous attempts at liquid nitrogen engines have struggled with.
The company has teamed up with transport refrigeration suppliers Hubbard Products Ltd to develop the engine in preparation for a larger trial — potentially with a supermarket — in the spring. But does it matter that Dearman’s vision is powering fridges, not cars?
“My dad did run a car using a Dearman engine,” says Michael. “Just because it works in principal doesn’t mean it’s the best use for a technology.”