The increasing deployment of Internet of Things (IoT) sensors in smartbuildings has enabled enhanced operational efficiency, real time monitoring,and improved occupant comfort. However, reliance on conventionalbattery powered systems presents challenges in sustainability,maintenance, and environmental impact. This thesis investigates ahybrid energy harvesting approach integrating photovoltaic (PV) andthermoelectric generator (TEG) technologies to provide a continuousand sustainable power supply for IoT devices in smart buildings.A comparative evaluation of multiple energy harvesting techniquesrevealed that while PV harvesting offers high efficiency in well environments,it is limited by light availability. Conversely, TEGs cangenerate electricity from temperature gradients, providing supplementarypower during low or no light conditions. Radio frequencyharvesting was found unsuitable for this application due to low powerdensity.The proposed system incorporates a high capacitance supercapacitor(1300 F) and an efficient power management circuit to optimize energycapture, storage, and delivery. The use of supercapacitors offers keyadvantages such as low maintenance cost, high power density, rapidcharge–discharge capability, and reliable operation across wide temperatureranges—making them well suited for hybrid energy harvestingsystems in smart buildings. Five year simulations using real worldweather data for Halmstad, Sweden, showed that the hybrid systemachieved over 99% annual uptime, with sufficient energy autonomy tosustain operation for more than 48 hours without new input. Seasonalanalysis confirmed that the hybrid approach effectively mitigates theintermittency challenges of single-source harvesters.The results demonstrate that hybrid PV-TEG energy harvesting is atechnically feasible, environmentally sustainable, and economically viablealternative to conventional battery-powered IoT devices in smartbuildings. The approach reduces electronic waste, minimizes maintenancerequirements, and supports the development of autonomous,long life sensor networks for intelligent building management systems.Limitations: This study is based entirely on simulations and literatureanalysis rather than physical laboratory experiments or full scaledeployment. Therefore, the long-term performance of supercapacitorsrelative to batteries has not been experimentally verified. The comparativediscussion of battery cycle life is indicative and based onpublished data; future work should include empirical testing underrealistic operating conditions.