Strategy for designing solar powered UPS systems - in hospitals in Eastern Africa

Abstract

In Eastern Africa a stable supply of electricity from the grid cannot be taken for granted. It is therefore important to investigate possibilities on how to improve the supply for areas of the society that suffers the most from these flaws. A power outage during an ongoing operation at a hospital could in the worst case be fatal for the patient and therefore hospitals is one of the areas in the greatest need of help. The UPS technology has come far but has not yet become a common part in electric system for hospitals in the region. It is in the topic of how to design a UPS system with solar power for a hospital in this region of the world that this thesis focuses on. A strategy is presented for how to design and dimension all major parts of a UPS system with solar power. The strategy discussed UPS topology, UPS system configuration, solar power inclusion, batteries, installation and future expandability. If the strategy is followed correctly an efficient solution can be found for the majority of all hospitals in the region. The strategy was tested and improved during a case study at Kolandoto hospital in Tanzania. In the case study a UPS system was designed and installed with the purpose to supply three operations theatres and the wards at the hospital. The UPS system installed was a decentralised system with hybrid UPS/solar units what functions both as a solar inverter and a UPS unit. Solar power was installed to be able to supply the loads both during a power outage and during normal operations. The final tests of the systems revealed that the system was fully functional but slightly oversized.