Long-term energy storages and voltage level converters have been necessary components in conventional energy harvesting systems even though those components significantly limits the lifetime, cost and form factor of the systems. Our recent research proved that removing those components is possible by directly supplying the harvested solar energy to the computing node.  For proving the functionality and effectiveness of the proposed storage- and converter-less energy harvesting architecture, we have implemented a practical circuit of power management unit (PMU) capable of performing maximum power point tracking (MPPT) of solar energy without requiring any long-term energy storages and voltage converters. 

Our PMU circuits operate at a wide operating range with ultra-low power consumption for providing high performance even with the low solar irradiance. As a pilot application of the proposed storage-less and converter-less energy harvesting system, we have implemented SmartPatch, a prototype of a solar-powered UV level meter. By exploiting the proposed PMU technology, we successfully remove the long-term energy storages such as a battery or super capacitor and voltage converters without affecting the functionality of the UV level meter. SmartPatch is a quite attractable application because people pay more attention to the skin irritation due to UV exposure and our SmartPatch can provide low cost, efficient solution for caring about the UV exposure.


Related Papers

[C-14-01] Cong Wang, Naehyuck Chang, Younghyun Kim, Sangyoung Park, Yongpan Liu, Hyunggyu Lee, Rong Luo and Huazhong Yang, "Storage-less and converter-less maximum power point tracking of photovoltaic cells for a nonvolatile microprocessor," in Proceedings of Asia South Pacific Design Automation Conference (ASP-DAC), pp. 379--384, SunTec, Singapore, 2014.