Fujitsu Laboratories was able to reduce the solar-powered sensor (and its energy storage elements by half) by developing special circuit control technology that reliably activates the wireless circuit by monitoring and adjusting the balance between power generation and consumption, by controlling signal transmission timing based on the temperature variation measured by a temperature sensor.
With this technology signal transmissions are only carried out at the time when the activation voltage, which varies with temperature, is maximized in order to prevent it from falling below the minimum operational voltage for LPWA module. By using power efficiently in this way, it is possible to tolerate variation in the power consumed by the wireless circuit or power generated by solar cells due to temperature. This eliminates the need for the excess energy storage elements that were previously necessary to respond to power fluctuations. Using this technology, Fujitsu Laboratories says it was able to collect temperature and humidity data transmitted to a Sigfox base station over a distance of about 7km, eliminating the need for batteries and their replacement.