LAUSR

Abstract Drying is necessary for wood biomass to be used in various applications such as heating. This work aims to assess the energy and performance of a hybrid solar dryer for woody biomass. The study is carried out by establishing the energy and mass balance in a prototype hybrid kiln. A mathematical model for predicting heat and mass transfer during the biomass drying process is developed and validated. The drying parameters are evaluated for a hybrid solar kiln witch integrate a heat pump and a condensing gas boiler. The results show that the energy consumption ratio decreases as the set-temperature increases. The combined use of a solar air collector and a heat pump allows a reduction of 52, 37 and 24% in terms of drying time for the three set temperatures 50, 60 and 70 °C, respectively. The use of a recycled air fraction of 75% in the hybrid solar dryer has the effect of reducing the energy consumption up to 84% and improving the drying efficiency by 92%. The results also show that the moisture extraction rate and the specific moisture extraction rate decrease as the bed height/wood chip effective diameter ratio increases. The use of a porous medium with an optimal vacuum rate is also desirable in order to improve the thermal performance of the drying system. The overall results show that the combined use of a solar air collector and a heat pump is an effective solution to reduce energy consumption and improve thermal performance during the biomass drying process.