Design and development of a community based micro-hydro turbine system with hydrogen energy storage to supply electricity for off-grid rural areas in Tanzania

Abstract

Micro-hydropower plants are used to supply electricity to the rural and off-grid areas of most developing countries like Tanzania. Their power capacity ranges from 5 kW to 100 kW which is equivalent to supply electricity from few households to several villages. The challenges that have influenced to undertake this research project are centred on the possibility of designing and developing a cost effective micro-hydro turbine system that can meet the dynamic load demand from the rural off-grid users and at the same time achieve high energy utilization efficiency with minimum energy losses using integrated renewable energy storage technologies such as hydrogen energy storage. The methods used in this research study are based on the field work and site data measurements together with power and energy determination as inputs to system design, modelling and simulation which will determine system characteristics. The results from data analysis show that the feasible water flow discharge for the micro-hydropower plant is 0.45 m3/s with the gross head of 25m which gives a turbine power of 79.5 kW and generator power of 75.5 kW as a power supply. On the other hand, results of the demand power analysis from the case study village shows the load profile has a low demand power of 8.42 kW and high demand power with peak power of 101.8 kW during the evening hours with the daily average energy of 1,114.38 kWh/d while the micro-hydropower can produce a maximum energy supply of 1,812 kWh/day.When supplying power to the load demand, the results show that the micro-hydro system produces excess power of up to 60 kW during low demand hours. In additional to this excess power production, it is also noted that the power supply is not sufficient to supply power during the peak hours of the day. So, in order to supply this peak power deficit, an energy storage system is introduced to store the produced excess electrical energy from the micro-hydro turbine system during the off-peak hours and then export it during the peak hours. Several energy storage options have been studied and analysed and based on the optimization results, the following system has been selected, i.e. micro-hydro turbine system with an electrolyser system and hydrogen fuelled internal combustion engine-generator system. The use of excess electricity to supply to the electrolyser system reduces the excess power to the dump loads to a minimum which results to an increase in the plant capacity factor and make the micro-hydro turbine system more energy efficient.