| With the vigorous development of Io T technology,the "smart +" model has emerged to solve various problems in production and life,such as smart cities,smart transportation,and smart agriculture.The key to this lies in the deployment of a distributed wireless sensor network.Thanks to the development of semiconductor technology,ultra-low-power sensors are widely used,but the cost of providing continuous power to a large number of sensors is enormous.Electrical energy can be obtained by converting clean and renewable energy such as wind energy,light energy,and ocean energy,which are widely available in the environment.Among them,wind energy and light energy have the characteristics of wide distribution and easy access,and have received extensive attention.The micro wind energy harvester operates in surface environment with low average wind speeds(1.2-3.8 m/s)and high uncertainty.But the wind turbines have long radii and require high wind speeds(11-25 m/s)during their rated operation.It is difficult to directly apply their design to micro wind energy harvesters.Light energy harvesters are designed using solar cells,and related products are relatively mature,but they are easily affected by season and weather conditions.Wind-light hybrid energy harvesting schemes can reduce uncertainty in the clean energy harvesting process,and the research focus on the design of micro wind energy harvesters with low startup wind speeds.Therefore,various types of Triboelectric-Electromagnetic hybrid micro energy harvesters have been widely studied,but these types of wind energy harvesters still have the problem of high startup wind speeds and cannot be applied in surface environments.To break through the bottleneck of the high startup wind speed of wind energy harvesters and the high uncertainty of clean energy collection,a wireless passive sensing network system with wind-light hybrid micro energy harvesting is proposed.The system consists of a low-startup wind energy harvesting unit and a flexible light energy harvesting unit to form an energy harvester.The dual-path energy management circuit is used to supply low-power wireless passive sensors,and multiple wireless passive sensors are deployed to achieve a wireless passive sensing network with environmental status monitoring capabilities.In the system design process,a design method with low tip speed ratio propeller and a design method to reduce rotor torque are proposed based on classical mechanics theory and blade-element momentum theory,which greatly reduces the startup wind speed and size of the wind energy harvesting unit with a propeller.Emphasis is placed on the selection and design of hardware for wireless passive sensors from a low-power perspective.A load switch is used to control the working time of high-power-consuming circuits to reduce sensor power consumption.Based on the Long Range Radio(Lo Ra)transmission technology,which can transmit over long distances and has strong anti-interference capabilities,a wireless passive sensing network without data forwarding is constructed.Experiments show that the wind-light hybrid energy harvester designed has excellent environmental energy harvesting performance.The wind energy harvesting unit covers a wind speed range of 1.2-11 m/s,with the peak power of the triboelectric nanogenerator ranging from0.025-239.6 μW and the peak power of the electromagnetic generator ranging from 0.553-100.9m W.The solar energy harvesting unit,under weak illumination conditions exceeding 1100 lux,exhibits an open-circuit voltage of 1.233 V and a short-circuit current of 0.235 m A.The sleep power consumption of the wireless passive sensor is 0.22 m A.The wind speed is 2 m/s and the illumination is 2100 lux,the net input energy of the wireless passive sensor can reach 1.77 m W and achieve self-powered operation.The above results indicate that the wind-light hybrid micro energy wireless passive sensing network system designed can achieve long-term,multi-node,and long-distance wireless passive sensing network coverage through wind energy and light energy harvesting.It has extremely high practical application value in Io T application fields such as smart cities,smart transportation,and smart agriculture. |
