Development of a Mathematically Controlled System for Electrical Energy Saving in Trough Withering of Tea

A control system was developed for optimizing the electrical energy consumption in tea withering. The electrical energy saving was achieved by controlling the speed of the fan through variable speed drive coupled with fan motor and controlling hot and ambient air delivering into the trough. The fan speed was determined based on theoretical mass flow rate requirement of air, calculated by the mathematical model developed for simulating the withering process, while calculating the thermodynamic properties of withering air and the moisture content of tea leaves in real time.   A single board computer, Raspberry Pi 3 model B was used to run the mathematical model and the software programme to actuate the VSD for controlling the mass flow rate of air delivered by withering fan as well as to control the withering air temperature. The experiments were conducted and electrical energy consumption of the fan and the quality parameters of the manufactured tea were measured and compared in the withering process with and without the control system. The results showed that the energy consumption was in the range of 36 to 39 kWh with the control system while it was in the range of 55 to 67 kWh in without control system. The specific electricity consumption was 0.17 to 0.18 kWh.kg-1 of made tea with control system and it was 0.27 to 0.35 kWh.kg-1 of made tea in without control system. Therefore, 39% of electrical energy can be saved by introducing the control system compared to the withering process without control system.