A plethora of energy-efficient MAC protocols have been developed for wireless sensor networks based on the assumption of readily available (if somewhat limited) battery power. One of main research challenges in this area is the development of approaches suited to devices which harvest energy from the environment (e.g. through solar cells or equivalent mechanisms). Although such devices offer the potential for self-sustained operation, energy availability is likely to be severely limited and time-varying. These characteristics challenge the traditional assumptions behind MAC protocol design and calls for new approaches. This PhD will explore the impact of limited and time-varying energy resources on the medium access control problem and subsequently develop new approaches which can maximise the throughput capability of typical networks. Simulation modelling will form a key part of the work, along with analytical models and practical evaluation as appropriate.