Research And Development Of Hybrid Microenergy Collection And Storage System For Power Supply Of Forest Wireless Sensors Nodes

At present,wireless sensor networks（WSNs）have been widely used in the field of forest resource management and environmental monitoring.But the limitations of the WSNs layout environment make them face serious power shortage problems.The efficient collection and utilization of forest environmental energy to power wireless sensors has many advantages.Due to the limitations of the forest environment,most of the environmental energy is micro-energy,and it is difficult to power the wireless sensor independently.In this paper,a new type of ultra-low power hybrid energy harvesting（HEH）system was designed to collect three kinds of environmental micro-energy（solar energy,soil temperature difference thermal energy and bioenergy in standing trees）to provide stable power for wireless sensors.According to the electrical characteristics of the three kinds of energy,the design of HEH system and test of board were completed.The system features included:（1）Due to the difference in the equivalent power supply of solar energy and the others,two independent sets of low-power DC/DC conversion circuits and storage circuits were designed to avoid impedance mismatch problems.And the problems solved,which was hardly to collect multiple energy sources at the same time,under the control of electronic switch.（2）The parallel connection of soil temperature difference thermal energy and bioenergy in standing trees,and they shared the DC/DC conversion circuit and the storage circuit to reduce power loss.（3）The energy system（solar energy）with high output voltage and power was selected to the main power supply line.The auxiliary power line（soil temperature difference thermal energy and bioenergy in standing trees）was mainly used to charge the lithium battery to form a complementary power supply.（4）The electronic multi-way switch was used to control the on/off of the main/sub power lines.Through the enable terminal to determine the direction of the switch,the main power supply was connected to the normally closed switch,and the auxiliary power supply was connected to the normally open switch.There was only one output for a single connection,which improved energy output and storage efficiency.Through data analysis and power loss analysis of the input source（solar energy,soil temperature difference thermal energy and bioenergy in standing trees）,output source（low-power wireless sensor node TI e Z430-RF2500 target board）,system integrated circuit board,the overall system efficiency was evaluated.The three kinds of energy output was 3.3V stably through the DC/DC converter circuit.The charge/discharge curve of the main/sub lithium battery in the power management circuit changed periodically with the input source.Combined with the input/output source data analysis,the overall system efficiency evaluation was obtained:taking 1.27m W(P_PV:P_TEG&PEG about 3:1)input power as an example,the loss of the HEH system accounted for 33.8%of the total input.The ratio was reduced with the increase of input power.