The importance of renewable energy is increasing rapidly nowadays. Solar energy is one of the most powerful resources that can be used to provide power supply for remote electrical devices. Such remote devices often need batteries replacements and maintenance that raises expenses. This contribution describes energy management and power harvesting implementation in a low-power microcontroller integrated within an autonomous solar-powered device with supercapacitor that significantly reduces maintenance needs. The energy management implements a fuzzy logic-based system that allows it to adapt to ambient temperature and sunlight intensity in deployment location. Fuzzy energy management sets device's functional mode that affects the measurement rate of the weather station and subsequent storage rate in SD Card. Both simulation results and real data results obtained in a laboratory located in Ostrava, Czech Republic, are presented in this contribution.