Imagine a world where every conceivable data about our surroundings is readily available for analysis making human life drastically different from what we know it today. This is not an unrealistic concept and its implementation lies on the creation of a network of ubiquitous sensor nodes powered by an energy harvesting system. This thesis explores the challenges in creating such systems. The system level components in a basic power harvesting system are given, with each components function and issues briefly explained. Energy sources are then visited and the available power from such sources is discussed. The report then explores the topics of power management and storage technology for harvesters. A case study involving the design of a power harvesting system using radiowaves is then presented. The RF harvester built has a sensitivity of -13 dBm, an efficiency of 14% and a simulated operating distance of 10 metres. Built in standard CMOS technology, the system is cost effective and compares favourably with reported RF harvesters in literature.