The formula to calculate the thermal efficiency of a biomass furnace is:

\[ \xi_t = \frac{Q_s}{FCR \cdot HVF} \times 100 \]

Where:

• \(\xi_t\) is the thermal efficiency in percentage (%).
• \(Q_s\) is the heat supplied in KCal/hr.
• \(FCR\) is the fuel consumption rate in kilograms per hour (kg/hr).
• \(HVF\) is the heating value of fuel in KCal/kg.