Innovative stand-alone biomass boiler characterized by low PM emission

The use of renewable energy sources (RES) as alternatives to fossil fuel for the production of thermal and/or electric energy has recently received much attention. Biomasses seem to be realistic alternative fuels leading to environmental, technical and economic benefits. However, to further increase the share of energy produced from biomass plants, it is necessary to improve the critical issues which to date have limited their spreading. In particular, particulate emissions and reliability are identified as the most determining limits. The paper describes two innovative technological solutions developed at the University of Bologna to further increase biomass plant marketability and shows a preliminary design on how they can be integrated in a biomass boiler for residential application. The first innovation is a high efficiency and low cost filter for particulate emissions: to reach a PM collection efficiency of 99.9%, wet scrubber was chosen as technological solution for the application on a 25 kW th biomass boiler installed in University of Bologna laboratory. The second innovation is the integration of a thermoelectric generator able to produce electricity directly from heat exchange. A prototype has been realized and tested in University of Bologna laboratory and represents a new approach in the design and application of thermoelectric generator. The paper shows how these new technologies can be integrated in a small size biomass boiler, including also an economic assessment.