Environmental pollution is currently one of the most worrying factors that endangers human health. Therefore, attempts are being made to reduce it by various means. One of the most important sources of pollution in terms of the current RoHS and REACH directives is the pollution caused by the use of chemical products for the production of sources for the storage and generation of electricity. The aim of this article is therefore to develop supercapacitors made of biodegradable materials and to investigate their electrical performance. Among the materials used to make these electrodes, activated carbon was identified as the main material and different combinations of gelatin, calligraphy ink and glycerol were used as the binders. The electrolyte consists of a hydrogel based on gelatin, NaCl 20 wt% solution and glycerol. In the context of this research, the electrolyte, which has the consistency of a gel, fulfills the dual function of the separator in the structure of the manufactured cells. Due to its structure, the electrolyte has good mechanical properties and can easily block the contact between the two electrodes. Most of the materials used for the production of supercapacitor cells are interchangeable materials, which are mainly used in other application fields such as the food or cosmetics industries, but were also successfully used for the investigations carried out in this research. Thus, remarkable results were recorded regarding a specific capacitance between 101.46 F/g and 233.26 F/g and an energy density between 3.52 Wh/kg and 8.09 Wh/kg, with a slightly lower power density between 66.66 W/kg and 85.76 W/kg for the manufactured supercapacitors.

This paper describes the design and implementation of an automated irrigation control system that uses data collected by a wireless sensor network. Each sensor node, built on a custom-designed printed circuit board, includes sensors for light intensity, temperature, and a custom soil moisture sensor. Data is transmitted to a central control node via ESP-NOW, where it is processed and compared with configurable thresholds retrieved from Google Sheets over Wi-Fi. Irrigation is triggered automatically when conditions meet the remotely defined thresholds. A key contribution is the development and testing of a custom soil moisture sensor, with results compared to commercial models. The system supports low-power operation through deep sleep modes, enabling long-term field deployment. The novelty lies in the complete integration of hardware, software, and cloud-based control, providing a flexible and low-cost solution for precision agriculture. The system can be deployed in greenhouses or open fields and serves as a platform for future research in smart irrigation. The fundamental aspect is a very user-friendly solution for any farmer attributable to easy accommodation to the Google Sheets interface, no maintenance cost over the cloud account, and up to 45 days of battery life or a built-in alternative for solar power.

This study investigates the temperature-dependent electrical behavior of 400 F/2.7 V supercapacitors, both at the single cell level and in packs of six cells connected in series (6S configuration), over the temperature range of −20 °C to 58 °C, for further development of sustainable energy storage systems (ESSs). In the context of the increasing share of renewable energy sources and the development of low-environmental-impact storage systems, supercapacitors represent a viable technology due to their high power density, energy efficiency, and extended operational lifespan. The work is motivated by the critical influence of temperature on the Equivalent Series Resistance (ESR), voltage stability, and charge–discharge dynamics in real energy storage applications. Experimental characterization was performed using controlled Constant-Current (CC) and Constant-Voltage (CV) charge–discharge cycles with automatic data acquisition, complemented by temperature regulation via thermal chambers. Different parameters like ESR, Open-Circuit Voltage (OCV), and transient current profiles were extracted for each cell, while the pack-level behavior was derived by analyzing the experimental data. Additional investigations have included voltage recovery analysis. The results showed that the capacitance remains largely stable over the entire temperature range investigated, while the ESR exhibits a strong nonlinear dependence, increasing significantly at low temperatures and contributing to a reduced efficiency. A common transition region was identified around the 20–25 °C range, where the system performance is optimal. The voltage recovery increases with temperature, indicating increased ionic mobility and faster charge redistribution. Significant non-uniformity was observed between cells connected in series, with some cells exhibiting higher thermal sensitivity and instability. Optimizing the use of supercapacitors within their operating temperature range may contribute to increasing energy efficiency, to extending system lifespan, and to developing sustainable solutions for modern ESSs. In conclusion, the 6S supercapacitor pack exhibits a strongly temperature-dependent electrochemical dynamics, governed mainly by the ESR and diffusion processes. These findings highlight the need for thermal modeling and integration of balancing strategies in series-connected supercapacitor packs, which can be used for the expansion of the environmental-friendly ESSs.