An Energy Efficiency Evaluation of the LTC3108 for Thermal Energy Harvesting

In everyday life, many activities release energy in the form of heat, such as car engines and the like; in nature, for instance, the thermal gradient between the internal temperature of a tree and the ambient temperature is a source of thermal energy. Thus, thermal energy has stood out, in these various scenarios, as a possibility to be harvested. In other words, it is possible to convert thermal energy into electrical energy to power low-consumption electronic devices. However, in thermal energy harvesting applications, the thermal gradient varies over time and, consequently, the energy generation potential is variable. Knowing this, it is necessary to use an energy conditioning circuit, such as the popular LTC3108 manufactured by Linear Technology, to regulate the generated voltage to achieve levels compatible with the power required by the devices. The present work presents an energy efficiency evaluation of the LTC3108 for different configurations of the Armstrong oscillator: Based on simulation results, it is demonstrated that, for generated voltage values greater than 125 mV, the combination of an Armstrong oscillator with a 1:50 transformer presents the highest efficiency value.