Application of solar technology to reduce local demand in the grid system: A case study

The power systems demand in Botswana is about 243 MW. The sole coal fired electricity generation station generates and supplies 128 MW. The remaining deficit is supplied by ESKOM of South Africa. The paper proposes a design of a solar photovoltaic system connected to the power distribution systems in buildings. The purpose is to island the PV system so that power flows from the system to the distribution network during periods of high and efficient solar insolation. During periods of low insolation and efficiency, the PV system is cut off from the distribution system and power supply from the grid system to the distribution system is automatically restored. The PV system therefore operates as a stand-by source replacing the grid supply when needed. At the heart of the design are the following: a three-phase inverter. The inverter converts the de power from the PV arrays to ac power for the load. The filter unit improves the quality of energy supply to the load. A maximum power point tracker for optimum use of solar energy and the controlling system to coordinate the two systems. The advantage of such a system is that the energy demand in the grid system will be considerably reduced for most part of the day and hence the dependence of and purchases from the neighboring countries will also be reduced. Also the use of batteries is not envisaged. The paper will be of benefit to private individuals and companies as well as electricity utilities.