MAXIMAL USE OF RENEWABLES IN SMALL ISOLATED POWER SYSTEMS

Paper i proceeding, 2005

For rural or remote areas in developing countries, where an extension of the existing grid is not economically or technically possible, electrification has to be carried out in small isolated power systems. For environmental and economical reasons it is beneficial if the electrification can be based on renewable energy sources. When designing such systems the need of over power production capacity is well documented. Over capacity leads to lost energy when power is available. For renewable sources like wind and solar the available power fluctuates heavily and therefore extra over capacity is required. The availability of the load increases with an increased installed capacity but reaches a level where further increase hardly effect the availability. By using a continuous controllable load (CCL) the energy usage can be maximized and frequency control can be obtained in over production situations. A case study for Dar-es-salaam in Tanzania has been carried out and it has been shown that implementing a CCL will significantly reduce the lost energy. In this study the CCL is a pumping system and thereby the extra energy will be available as water or pressurised water. However, a small negative change in the availability of the other more prioritised loads can be seen, as the CCL needs a minimum of power. This minimum power increases with the increased CCL. Due to a limited capacity of the CCL there will still be some lost energy in the system. The lost energy decreases with an increased CCL. However, the generation still need some kind of limiting equipment due to the limited capacity of the CCL.