Intelligent Heat System – high energy efficient wood stoves with low emissions

This development and demonstration project conducted by HWAM A/S and DTU Chemical Engineering has contributed to the development of an automatically controlled wood stove (HWAM IHS), which is on the market today. The new digital control system ensures optimal combustion conditions by keeping optimal temperatures and overall oxygen concentrations in the combustion chamber throughout a complete wood log combustion cycle.
This improved performance has been verified by field tests in private homes where measurements showed significant reduced emissions and higher efficiency for the IHS stoves compared to traditional manually controlled stoves. The tests also showed that in many cases it is impossible to visually tell if non-optimal combustion occurs. Also, in practice it is impossible to manually control the combustion air as fast and optimally as the automatically controlled air inlet valves.
Emission measurements at the research wood stove set-up at DTU Chemical Engineering showed generally low emissions of particles, well below current standards, and high energy efficiency.
The highest emissions of CO, VOC and PM were seen in the ignition phase while only a small particle peak was observed in the flame phase. The CO emission in the char combustion phase increased due to decreasing temperature in freeboard – but almost no particle emissions were seen this combustion phase.
For the further optimization of the state of art technology of the IHS stoves developed in this project, the improvement of the tertiary air injection showed a considerable potential, which may result in an improved combustion and reduced pollutant emissions. Some important areas of future work include further development of control system sensors and measuring methods, and optimisation of the combustion process and chamber.