Robert Stirling invented and patented the Stirling engine in 1816. It was known at the time as Stirling’s air engine and it was invented as an alternative to the atmospheric steam engine which was dominant at that time. It had the advantage of eliminating the need to use coal to create steam to drive a piston. The piston in Stirling’ engine is driven by gas sealed in the engine which expands and contracts as it is heated and cooled. Today, the Stirling engine is only used in specialized applications. Some of its uses include a stove fan where the operation needs to be quiet, on yachts as auxiliary power generators and on submarines.
A difference in temperature needs to be maintained within the engine between the hot and cold parts. Power is generated when the air in the engine is heated and cooled rapidly. The piston is pushed upwards when the air expands as it is heated. As the same air is cooled, it contracts which pulls the piston downwards. Heat energy is converted to mechanical energy when the heating and cooling process occurs rapidly. A two cylinder Stirling engine works in exactly the same way except one cylinder will remain hot and the other remains cold. Research has continued into developing the Stirling engine and these developments mean that it is now possible to power the engine with heat that is equivalent to that produced by a cup of coffee.
There are a number of advantages that a Stirling engine has. It is much safer than a steam engine because there is almost no risk of a boiler explosion. Less pressure is put on the pistons in a Stirling engine which means that general wear and tear is reduced and it is possible that the engine could last a decade without needing to be serviced. Wear is also reduced by the fact that the engine is not experiencing combustion within the engine itself. Almost any type of heat source can be used to power the engine and because it is not reliant on burning fuel such as coal it is better for the environment as it produces less pollution.