An Alpha type Stirling engine contains two power pistons in separate cylinders. One cylinder is hot and one cold. The hot piston is situated after the higher temperature heat exchanger and the cold piston is situated after the low temperature heat exchanger. (In the diagram below, in the pipe connecting the two cylinders, internal heat exchangers are not shown in the compression and expansion spaces). A regenerator would be placed in the pipe connecting the two cylinders. The crankshaft has also been omitted.

This engine configuration results in a high power-to-volume ratio but the high temperature of the hot piston can create technical problems as the seals need to withstand high temperatures. To get over this problem a system is incorporated that carries a large insulating head to move the seals away from the hot zone at the expense of some additional dead space.

1. Most of the working gas is in contact with the hot cylinder walls, it has been heated and expansion has pushed the hot piston to the bottom of its travel in the cylinder. The expansion continues in the cold cylinder, which is 90° behind the hot piston in its cycle, extracting more work from the hot gas.

2. The gas is now at its maximum volume. The hot cylinder piston begins to move most of the gas into the cold cylinder, where it cools and the pressure drops.

3. Almost all the gas is now in the cold cylinder and cooling continues. The cold piston, powered by flywheel momentum (or other piston pairs on the same shaft) compresses the remaining part of the gas.

4. The gas reaches its minimum volume, and it will now expand in the hot cylinder where it will be heated once more, driving the hot piston in its power stroke.