Energy harvesting is a very promising area for clean energy production, especially for unused and wasted energy sources such as thermal energy. Therefore, a pyroelectric PU-xPZT material is implemented to convert waste heat into electricity to make low-energy devices autonomous and contribute to sustainable development. The goal of this contribution is to present the relevant methods of thermal energy harvesting using the pyroelectric PU-xPZT composite, where x = 10%, 20% and 30% and to optimize this energy in order to make the systems autonomous from the energy point of view. In this regard, an experimental setup was carried out to polarize and characterize PU-xPZT, and evaluate the energy harvested by the PU-xPZT composite. The investigation results obtained from the pyroelectric PU-xPZT composite have demonstrated an excellent capacity to convert thermal to electrical energy. With this original concept, the power harvested is about 14.00 μW. Furthermore, using the (SSHI) technique, the greatest harvested power increases by 50% for the PU-30PZT composite (21.5 μW). Therefore, this energy type is acknowledged as the most readily accessible ambient energy source, facilitating a considerable amount of harvested energy based on the intended application.