If you have a lot of heat, then you can do what power plants do: Use the heat to generate steam, and use the steam to spin a turbine. The turbine can drive a generator, which produces electricity. This setup is very common, but it requires a fair amount of equipment and space.
If you would like to generate electricity from heat in a simple way that has no moving parts, this usually involves thermoelectric generators.
A Thermoelectric Power Generator (TEG), is any solid-state device that can convert heat directly into electricity. Such devices are based on thermoelectric effects involving interactions between the flow of heat and of electricity through solid bodies.
All thermoelectric power generators have the same basic configuration. A heat source provides the high temperature, and the heat flows through a thermoelectric converter to a heat sink, which is maintained at a temperature below that of the source. The temperature differential across the converter produces direct current to a load having a terminal voltage and a terminal current. As there is no intermediate energy conversion process, thermoelectric power generation is classified as direct power conversion.
More information about Thermoelectric Generators (Wikipedia)
Videos of Thermoelectric Generators (YouTube)
Thermoelectric Generator Forums (TEGforums.com)
More information Web Sites about Thermoelectric Generators below:
Basics of Thermoelectric Generators
Thermoelectric Generator Definitions
Basic information on the Thermoelectric Generator
More information on the Thermoelectric Generator
Electricity from Heat Educational Page
Stove Lite (World's First Wood Stove Powered Thermoelectric Lantern)
Devil Watt (Wood Burning Stove Thermoelectric Generators)
TEGPRO (Experts of TEG systems)
Tegulator (Complete line TEG power regulators Made in the USA)
Tegmart (Online Store: Wood Burning Stove Thermoelectric Generators, Energy Harverting Regualtors (Tegulator), and other Accessories)