Okay, maybe indigenous peoples didn’t have air conditioning, but they also weren’t the spoiled brats we are. One of the original heat engines is the Stirling Engine, invented in the early 1800s. Essentially, it is a closed-loop system in which a working fluid is alternatively compressed and expands when heat is applied. Constructing this kind of engine is a relatively easy task once you have the materials, which are actually very common. The old hard drive of a computer can function as a perfectly acceptable heat sink. The working fluid can be almost anything, although air is popular because it is so easy to obtain. But if you have the capacity, helium or hydrogen gas would be more efficient. And the pistons can be made out of just about anything you can you make pistons out of.
Usually a Stirling Engine is used to produce motion by simply placing the device in direct sunlight. Although any heat source of sufficient intensity can be used. This in and of itself is very useful since it directly converts sunlight into mechanical motion, with a possible 80% efficiency rate. The temperature differential necessary to run a Stirling Engine is surprisingly low. But the most fascinating aspect of a Stirling Engine is that it also works in reverse. If you input mechanical motion, rather than heat, the engine will output cold, rather than mechanical motion. Stirling Engines were used in early refrigeration and are still used in a number of industrial, high tech, and military situations. So if you were to connect a Stirling Engine to some source of mechanical motion, say a water wheel, you would get a constant output of cold from the Engine. This cold could be used to extend the life expectancy of food, or to make really hot days more comfortable.