Harvesting energy for IoT nodes in places that are permanently poorly lit is important, as many such places exist in buildings and other locations. The need for energy-autonomous devices working in such environments has so far received little attention. This work reports the design and test results of an energy-autonomous sensor node powered solely by solar cells. The system can cold-start and run in low light conditions (in this case 20 lux and below, using white LEDs as light sources). Four solar cells of 1 cm² each are used, yielding a total active surface of 4 cm². The system includes a capacitive sensor that acts as a touch detector, a crystal-accurate real-time clock (RTC), and a Cortex-M3-compatible microcontroller integrating a Bluetooth Low Energy radio (BLE) and the necessary stack for communication. A capacitor of 100 μF is used as energy storage. A low-power comparator monitors the level of the energy storage and powers up the system. The combination of the RTC and touch sensor enables the MCU load to be powered up periodically or using an asynchronous user touch activity. First tests have shown that the system can perform the basic work of cold-starting, sensing, and transmitting frames at +0 dBm, at illuminances as low as 5 lux. Harvesting starts earlier, meaning that the potential for full function below 5 lux is present. The system has also been tested with other light sources. The comparator is a test chip developed for energy harvesting. Other elements are off-the-shelf components. The use of commercially available devices, the reduced number of parts, and the absence of complex storage elements enable a small node to be built in the future, for use in constantly or intermittently poorly lit places.

Leak detection in underground drinking-water networks is especially difficult in plastic pipes because leak-generated acoustic and vibration signals attenuate strongly. This study investigates the concept of distributed soil-moisture monitoring as a potential complementary early-warning approach and derives stakeholder requirements for future system development. An expert questionnaire was distributed by email to 90 water-supply utilities in the Swiss cantons of Thurgau, Zurich, and Aargau. Fifty-five submissions were received (61.1% relative to invitations), of which 52 included consent for research use and were analysed (57.8% of invitations). Item-specific denominators, Wilson 95% confidence intervals, and exploratory exact and non-parametric subgroup tests were used. Current practice was dominated by acoustic methods (48/52) and baseline-consumption monitoring (41/52). Among valid quantitative answers, 29/47 respondents expected detection at or below 20 L/h (61.7%, 95% CI 47.4–74.2%), 44/46 preferred at least daily sampling (95.7%, 85.5–98.8%), 41/45 selected a price at or below EUR 20/m (91.1%, 79.3–96.5%), 36/46 specified a false-alarm tolerance of no more than one per year (78.3%, 64.4–87.7%), and 39/44 specified a missed-leak tolerance of no more than 5% (88.6%, 76.0–95.0%). These cumulative proportions include more demanding response categories and do not establish acceptance of performance exactly at each boundary. Experience-group comparisons yielded no statistically significant differences after Holm correction. The contribution is a traceable, uncertainty-aware requirement specification linked to engineering relationships and verification planning for power, spacing, latency, cost, false alarms, and missed detections. Limited precision, regional recruitment, and unfamiliarity with the monitoring approach constrain interpretation. The requirements are provisional design inputs; technical feasibility and final acceptance criteria require laboratory, field, and stakeholder validation.