Development of an indoor photovoltaic energy harvesting module for autonomous sensors in building air quality applications

A 50 mm × 20 mm × 15 mm indoor photovoltaic (PV) energy harvesting power module (IPEHPM) has been developed for powering an IoT sensor node containing a low-power CO₂ sensor for automatic building ventilation. It is composed of a high efficiency PV energy harvesting module and a supercapacitor to produce 3.6 ~ 4.2V output voltage with 100 mA pulse current for up to 600 ms. Storage efficiency analysis and storage efficiency tests of the IPEHPM have demonstrated that with the adopted simple power management scheme, which exempts the commonly used power management blocks of the voltage regulator and the maximum power point tracking (MPPT) to save power, 88.7% average storage efficiency has been achieved at 200 lux. With the newly established PV powering model, the power consumption requirements of an IoT node can be directly converted into the illumination requirements of the PV energy harvester, making the IPEHPM easy to use. IPEHPM powered IoT experiments with a low-power CO₂ gas sensor have demonstrated that the IPEHPM is suitable for IoT-based building ventilation applications where the CO₂ concentration level is measured every 150 seconds at the indoor lighting condition down to 200 lux.