Standardized small diesel power plants for rural electrification in Tanzania.

摘要

This study focuses on small townships where the forecasted power demand stays below 500 kW during the first ten years. Case study calculations were made where two hypothetical load centres form the base. Each load centre is assumed to be supplied by two alternative standardized diesel power plants. One option is a power plant consisting of two medium speed (750 rpm) generator sets, one always on stand-by. Alternatively, a power plant consisting of three high speed (1500 rpm) generator sets is evaluated for each hypothetical load centre. The calculations clearly show that the high speed, three unit option comes out cheaper than the two unit, medium speed option in all the considered cases. The fuel costs per kWh generated are almost the same in all the cases studied, i.e. between 6 and 7 US cents. The medium speed engine tends to consume more fuel per kWh generated than the high speed, as it runs more often on part load. Consequently, the fuel costs will be slightly higher for this option. It is also of interest to compare the plant failure rate of the two options. In this study no proper probability evaluation has been made, but some general reflections can be worth considering. The availability of spare parts in Tanzania is doubtful. Many small diesel power plants presently operating have to wait indefinitely, when a failure appears that requires spare parts. As long as the individual sets have the same, or nearly the same failure rate, a three unit plant has lower probability for total loss of generating capacity than a two unit plant. The main conclusion of this evaluation is that for electricity generation in rural Tanzanian villages, power plants with three small, high speed generator sets are preferable to plants with two, medium speed generator sets. A power plant made out of small sets requires less capital, consumes less fuel and is not as likely to loose its generating capacity totally. 16 refs, 10 figs, 21 tabs