How do they work (heat powered wood stove fans)? Is it possible for an eco fan to create electricity? Is there enough electricity to run a small fan? What is a heat-powered fan? It is true. The heat from the wood stove generates heat that powers Heat-Powered Fans. They don’t require electricity. The wood stove is equipped with a heat-powered fan that sits on top as the stove warms up and the fan blades spin. According to some manufacturers, a heat-powered fan that pushes warm air away from a wood stove can help heat a space up to 18% quicker. Another benefit to a heat-powered fan is that it moves air around, creating convection effects, so the woodstove doesn’t have to run as hot. This allows the customer to use less wood.
What is the working principle of heat-powered wood stove fans?
A heat-powered wood stove fan works when there is a temperature difference within the fan. The wood stove heats the high-temperature side, while insulation and a heat sink expose the cold side to air.
Two types of heat-powered wood stove fan designs are common: a Thermoelectric Generator, which is an electric design, and a Stirling Engine, which is a mechanical one. Heat-powered fan designs both work by being exposed to temperature variations. One part is heated (as in a wood-burning stove), while the other is kept cool.
The Thermoelectric Generator heat-powered fan
The thermoelectric Eco fan uses low-cost thermoelectric generator (TEG) modules to provide small amounts of electricity. TEG is an electric device made from two different metals and separated by positively or negatively charged semiconductor material.
Thermal insulation can generate electrical power when heat is applied to one end of the TEG. This is the Seebeck coefficient, which generates electrical power.
When a TEG is connected between two heatsinks, placed directly on top of the hot wood stove and the other thermally insulated to create temperature differences, it will generate enough electricity to power an electric motor. Multiple TEGs connected will produce a higher voltage and more power to spin a motor fast sufficient to connect it with fan blades and move enough air to heat a room. This is a simple, no-input power design for a modern Eco fan powered by a wood stove.
Stirling Engine heat-powered fan
The Stirling generator, also known as the Stirling engine or (also known as Eco fans) Stirling Generator, has many functional designs based on expanding and compressing fluids in closed cycles.
The same gas is found in two pistons that are connected. When heated, the gas expands and forces the piston in the opposite direction to compress. The force of the hot fluid or gas is reduced as it cools, but the force exerted on the second piston by the compressed fluid/gas is still present. The second piston moves in the same direction as the first and repeats the cycle.
In an eco fan two pistons connected contain the same gas. The gas is expanded when heated, forcing the first piston in a direction that forces the opposing piston to compress. As the fluid or gas in the hot side starts to cool, its force is lessened, but there is now a force on the second piston that contains the compressed fluid or gas. The second piston moves in the direction of the first piston, repeating the cycle. This cycle continues so long as there is a heat source that continues to expand the fluid or gas in the first piston. A rotating crank linked to the pistons turns as the pistons shift. Fan blades are attached to the crank to make a Stirling engine eco fan.