Test stand method for the determination of system efficiency and emission factors of small-scale biomass combustion systems
In the last decades certification tests of small-scale biomass systems have impressively shown the state of the art. Though, steady state measurements present results for optimal operation. In practice typical results differ due to deficiencies of installation, maintenance and operation.
The determination of environmental impacts and conversion losses of energy service applications requires accurate, reliable and cost-saving methods. Fundamental knowledge of emission factors and annual system efficiency is required accordingly. Currently in Austria used data for small-scale biomass combustion systems is based on measurements done more than 10 years ago. In public and political discussion this regularly leads to misunderstandings and consequently inhibits market penetration of modern small-scale wood combustion systems.
To overcome this difficulty, the project aims at the development of a test stand measurement method for the determination of annual system efficiency and emission factors of small-scale biomass combustion systems. The method should allow deriving realistic annual system efficiencies and emission factors under unsteady conditions. Measurement setup, techniques and position of sensors should be according to the default boiler testing standard EN 303 5 to use the same infrastructure. For evaluation of measurement data an easy-to-use software was designed, which is capable of calculating the annual efficiency and the emission factors for a boiler heat storage combination too.
According to the developed measurement method 3 pellet boilers, 1 wood chip boiler and a log wood boiler were tested on 3 different test stands. The evaluation of the measurement data shows the suitability of the new method to quantify the stage of development of modern small-scale biomass boilers.
Values for annual standard system efficiencies measured on test stand are comparable to published results from field tests. The modulating operation of the biomass boilers results in lower annual efficiencies compared to operation with heat storage tanks. Efficiency is increased if the heat loss of the storage is considered too. The derived annual emission factors are comparable to values from field tests. Because of the small amount of tested boilers there is still a difference to published emission factors.
The results of our experiments show that the newly developed method is a good tool to evaluate small-scale biomass boilers. With this method we provide an easy and reliable tool to determine annual system efficiencies and emission factors for realistic boiler operation.
Bioenergy 2020+ GmbH
Project or cooperation partner
- Armin Themessl / Arbeitsgemeinschaft Erneuerbare Energien Kärnten Salzburg
- Leo Lasselsberger / HBLFA Francisco Josephinum - Biomass Logistics Technology
- Hans Hartmann / Technologie- und Förderzentrum Nachwachsende Rohstoffe