Performance Analysis of the Direct-Charge β-Radiation Energy-Harvesting Method

In the last decade, we witness an active search for an efficient, reliable and long-lasting power source for miniature devices and wireless sensors. One of the promising energy conversion methods for the development of such a power source is the direct-charge energy-harvesting method. This technique is implemented in a vacuum capacitor arrangement. In this setting, the kinetic energy of the emitted particles is converted into usable electrical energy without intermediate steps. In this work, we introduce a systematic analysis of the performance of this method in terms of appropriate transfer functions describing the main energy loss mechanisms that govern its efficiency. The individual contributions of these mechanisms are determined and integrated in order to evaluate the overall efficiency. To demonstrate the validity of our analysis, it is applied to a specific harvester for which experimental measurements are available. The predicted efficiency and volumetric power density are compared with the experimental findings under various operational configurations. Excellent agreement of our predicated performances with the experimental results is revealed. The analysis enables to predict the performance envelope of the harvester. Thus, it can be used for the design and optimization of direct charge β-radiation devices. In the specific device examined, the predicted highest efficiency is 13.5%.