Optimisation of hydropower generation at Volta River Authority during off-design conditions
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Date
2003-11-29
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Abstract
Volta River Authority (VRA) operates two hydropower plants as part of its power system; one of which consists of six turbine-generator units at Akosombo with total capacity of 9 12MW and the other a downstream plant of four turbine-generator units of total capacity of 160MW at Kpong.
The operation of the downstream plant depends on the total discharge from the Akosombo plant to create the head required.
The discharge per unit at the Akosombo plant is less than the discharge per unit at the Kpong plant. However, the total discharge from the Akosombo plant is more than that from the Kpong plant under normal operating conditions for all units. Running less than six units at the Akosombo plant results in inadequate head at the Kpong plant; this makes it impossible to put all four units into service at the Kpong plant.
A model equation of the two power plants has been determined and used for the estimation of the plant efficiency. The model equation serves as the objective equation and is used for the optimisation of the system.
A computer program was developed for determining the combinations of the units at the
Akosombo and the Kpong plants that would allow for optimum generation of power. The
Search method of optimisation was employed and coded in Visual Basic programming
language. The simulated results were validated using the given operation data.
The output of the program includes the number of turbines that can be run within a day on hourly basis to obtain the optimum power output, .taking into consideration the set of constraints of the system. Estimated combinations for six days are provided.
The result of this project or thesis is recommended for use as a guide in the operation of the Akosombo and Kpong Hydropower plants by VRA when the headwater level at Akosombo dam is less than the normal recommended minimum of 75.59m. It is expected that by the use of this program, optimal power output shall be obtained at low available water levels. The programme can be used to predict future available power.
Description
A thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology in partial
fulfilment of the requirements for the award of Master of Science degree in Mechanical Engineering, 2003