Performance characterisation of a husk powered system for rural electrification in Uganda.

Abstract

This dissertation reports on the performance characterisation of a 32 kWe gasification power plant connected to an isolated electric grid in Tribogo Village, Muduuma Parish in Mpigi District. The system was installed as a rural electrification pilot business by the Renewable Energy Incubation Centre at the College of Engineering, Design, Art and Technology (CEDAT) at Makerere University in conjunction with Norgesvel of Norway. The objective of the study was to provide technical support in the installation of the plant and systematically establish field performance characteristics of the system by collecting and analysing data on actual operating conditions. The system had operated since October 2012 with a daily usage of 7 hours. During the study, it was observed for 22 days while being run on maize cobs and coffee husks as fuel for 11 days each. The biomass consumption was found to be an average of 30 kg/hr of maize cobs and 25 kg/hr of coffee husks. Total power output was 34.2 kW with a line voltage of 243.9 V, frequency of 50 Hz and phase voltage of 422 V with a power factor of 0.85. The specific fuel consumption was about 0.88 kg/kWh for maize cobs and 0.74 kg/kWh for coffee husks. The efficiency from biomass to electricity was 20.5% for maize cobs and 30% for coffee husks. The solid waste products generated were 12% for maize cobs and 10% for coffee husks of the total biomass fuel fed into the gasifier. Applying a software business model using a world renown software, RETScreen, to determine the total cost of inputs and cost of sales, the unit cost of power was found to be US$ 0.26 (UGX 686/=). The simple payback period for the business was 3.3 years for maize cobs and 3.4 years for coffee husks with a break even period of 6.2 and 6.3 years, respectively. In conclusion, the operation of the 32 kWe power plant was found satisfactory. Indeed, it was producing more power than the community could consume or buy. The system is thus suitable for rural areas with available agro-residues of up to 7 tons annually despite some minor operational challenges that can be overcome by training the operators.