Analytical and CFD Simulation of an on-roof Wind Generator Using Biomass

Solar systems usually suffers the non-continuous availability of solar insolation e.g.
during the night and in cloudy days. The integration of biomass with solar systems
may represent a good solution for the application which is under consideration in the
“on-roof solar chimney”. This report highlights the importance of understanding the
combustion process for efficient burning of the biomass waste and also point out one
of the reasons why biomass waste is not fully utilized. Mathematical modelling of
the system is the main focus of this report.
Preliminary design of the system for two cases is provided. On Case I the fluid
stream to the Savonius rotor is the flue gases only. As the flue gases flow through the
roof heat is lost to the ambient air through the glass the glass canopy. The lost heat
can be utilized by putting an absorber layer between the insulated roof and the glass
canopy and allowing the ambient air to pass between the absorber and the canopy.
This provides the basis for Case II which is to make use of the heat loss through the
canopy. The resulting air stream is mixed with the flue gas stream before entering the
on-roof chimney, and the resulting stream is directed to the rotor on the roof to
generate power.
From the simulations it is shown that a significant amount of the heat carried by the
flue gases leaves through the on-roof chimney and only 10% is lost through the
canopy for Case I and Case II reduces the heat lost through the canopy by 3% and the
output power is increased by 74% per unit width of the house. The analysis of the
system proves that there is potential in biomass being used to generate electricity for
domestic applications with further modifications to the roof dimensions and the
configuration of the Savonius wind rotor.