Modelling of heat pump drying system powered by a hybrid PV-wind-battery plant for slow-drying hardwoods

Abstract

In Chile, a small sawn lumber industry producing native hardwoods co-exists with the massive radiata pine industry. Artificial drying of these hardwoods is challenging as they only tolerate low temperatures but extended drying schedules. In this work, an energy autonomous wood drying system for slow-drying hardwoods, powered by a heat pump and a hybrid non-conventional renewable energy plant, is modelled. The model was used to simulate the drying of 3 m3 of Patagonian Oak lumber in summer and winter, considering a power plant composed by 46 photovoltaic panels (175 W), a 10-kW wind turbine, 11 lithium batteries (48 V, 100 Ah), and an auxiliary unit, as power resource. Results of the simulation show that the moisture content (dry-based) of Patagonian Oak lumber can be reduced from 102 to 12 % in 30 days, with a SMER of 2.2 kgwater/kWh. In such condition, the heat pump will consume 585 kWh per m3 of dried oak, which energy demand and autonomy are secured by the hybrid power plant. In summer, the hybrid power plant can supply up to 97 % of the dryer electric demand. The 3 % difference can be supplied by an auxiliar unit. In winter, the hybrid plant can supply up to 70 % of the power demand. Therefore, the auxiliar unit must supply the 30 % additional power demand. The results indicate that the power supply generated by a hybrid power plant adjust well to the power needs of an extended artificial drying cycle, which is required for several hardwood species processed nowadays in Chile.