Grateless combustion and fuel for hot air stoves

Grateless fireplaces (hot air stoves and fireplaces)

The vast majority of stoves are structurally made with a grate hearth, while this method of combustion has a large number of disadvantages. Unpreheated air flows into the furnace through the grate, which lowers the combustion temperature and thereby reduces the fuel and heating efficiency. On the other hand, in the case of grateless stoves, wood gases are burned better, and thus fuel and heating efficiency are higher. In addition, there is no need to take out the ashes often (once every 3 weeks, sometimes even longer) and even the smallest carbon that would fall through the grate into the ashtray is burned up. This dramatically reduces the large amount of ash in the furnace.

Grateless fireplaces were developed on the basis of new knowledge about wood burning, which shows that wood does not need a grate for burning, as is the case with fossil fuels.

Advantages of grateless combustion:

  • It contributes significantly to a higher combustion temperature in the hearth, which has a very positive impact on efficiency, performance and, above all, emissions.
  • It will enable maximum fuel burn-out, thereby fundamentally reducing the amount of ash, increasing combustion efficiency, which also affects the performance of hot air stoves themselves.
  • Thanks to the perfect burning of ash, grateless combustion extends the time interval for the maintenance of the hearth (once every 3 weeks, sometimes even longer), so it is easy to start a new fire very quickly the next morning.

Fuel for hot air stoves, dry wood

The vast majority of wood species have a very similar calorific value per kilogram of wood mass, but they differ by a very significant volume weight of individual wood species.

The calorific value of wood is directly related to its moisture content, with a lower proportion of water, the calorific value of wood rises. If we heat with raw wood with 50% moisture (raw wood), we get approx. 8 MJ, i.e. 2.2 kW, from one kilogram of wood. At an ideal 20% wood moisture for heating, we get 14 MJ, i.e. approx. 3.9 kW. Heating with wet wood is a waste of money and natural resources!

If you want to dry wood effectively, it is necessary to store it properly, so it is advisable to follow several principles:

  • store the wood on a dry surface, preferably 20 dm from the ground
  • store the wood in a sunny and windy place
  • if you lay the wood crosswise, it will dry faster
  • cover the timber with a rain and snow cover

Raw wood has a moisture content of around 50%, in a year of drying it is possible to achieve a wood moisture content of around 25% under ideal conditions.


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