The Caframo ecofan is one of a range of fireplace accessories designed to improve the efficiency of a log burner by improving the distribution of hot air from the hot metal surfaces out into the rest of the room. This style of woodstove fan has significant advantages as it rests directly on the metal stovetop and draws its power from the heat of the fire.
One common complaint regarding modern woodburners is that they can have a "too hot or too cold" effect on the room. If you are sitting nearby you can quickly feel too hot, while the more remote parts of the room and building fail to warm up properly. In many cases this is a significant factor in limiting them to occassional or novelty use, rather than replacing a central system for home heating.
The ecofan addresses this by directing hot air from above the woodburner out into the room, rather than allowing it to simply rise up to the ceiling. As a result you may also be able to reduce the firewood you burn as the ecofan distributes warmth further and more evenly through your living space.
The ecofan powers itself by generating an electric current from the temperature difference between the top of the stove and the surrounding air. This electricity is generated through the "Seebeck Effect" where alternating strips of semiconductors generate a voltage and, when carefully arranged, can produce a current. This is actually a very old technology, with "thermoelectric generators" being produced since around 1820!! They were originally used to charge early radios before mains electricity became widespread.
This in turn powers the electric fan, letting the ecofan run without any external energy source other than the stove itself. This makes it ideal for locations where there is no mains power.
Using a stove thermometer along side your Ecofan is highly recommended. These Caframo fans work best within a limited temperature range of between 205°C and 345°C, which is also the recommended operating temperature for most modern wood stoves. Exposing an ecofan to temperatures above this range is likely to permenantly damage the mechanism through overheating and can also damage your woodburner!
In my parents home, where we have two large wood stoves which contribute a substantial part of the winter heating load, we have for some years used a stirling engine based wood stove fan. This does a great job of distributing heat throughout the large rooms of their house, but has had some operational problems. The fan itself operates from an internal piston arrangement - purely mechanical power generation - which is rather sensitive to overheating. The mechanism needs occassional lubrication and can sound rather noisy if the room is quiet.
Because the ecofan uses a power generating system with no moving parts it is less prone to damage through overheating, and some models come with a bi-metallic strip in the base to lift the fan if the surface it rests on becomes too hot.
The ecofan motor itself is nearly silent which to my mind is a substantial advantage.
Currently they cost in the region of £90 which, while pricey, may be a worthwhile investment interms of reduced firewood consumption and greater comfort and warmth distribution from your woodstove. That said; there are free or nearly free, alternatives if you are on a tight budget or worried about adding to your environmental impact or carbon footprint by purchasing manufactured materials.
We have a couple of homemade wood stove fans at home, constructed from old PC cooling fans and mobile phone chargers. They do need to be plugged into the mains, but the power consumption is minimal and the cost savings, both financial and environmental, from not purchasing manufactured components is substantial.
There are a variety of different models available on the market at the moment:
Ecofan 800 Original Fan DISCONTINUED
The original ecofan model - it comes in two forms with different blade/body colours
Ecofan 802 Airplus Fan DISCONTINUED
Updated version of the ecofan wood stove - comes in two forms with different blade/body colours. The fan is more powerful and less prone to problems cause by overheating.
Ecofan 806 GS Gas-Stove Fan
Note that this fan is not suitable for woodburning stoves - it is designed to run on lower temperature surfaces and will overheat.