SEQUENCING OF HYDRO PROJECTS BY USING MIXED INTEGER PROGRAMMING

A number of alternative sources of electrical power are investigated for a rapidly developing country, Transkei. The alternatives comprise various hydroelectric projects and associated reservoirs, or purchase of electricity from the South African Electricity Supply Corporation (ESCOM). Each project is optimal at a different size, and being in the same river basin, the Mzimvubu basin, they are interdependent. Mixed integer programming is used to select which source should be implemented at successive points in time. The ESCOM supply is regarded as a linear variable and the various hydroprojects handled as integers in order to conserve their integrity after project optimization. The effect of different inflation rates of hydro and coal-fired ESCOM power is found to affect the sequencing. With equal inflation, large storage is recommended for hydro, and with lower thermal cost inflation, minimal storage is preferred. The resulting optimal plan may be linked into a national economic master plan by using the decomposition principle.