Development Of A Piezoelectric Energy Harvesting System For Applications In Collecting Pavement Deformation Energy

Transportation is a pillar industry of national economic and social development.With the rapid development of the transportation industry,the energy saving and emission reduction in this industry have been paid more and more attention.This research is to develop an energy harvesting system to collect the wasted energy due to the pavement deformation induced by road traffic.It includes theoretical analysis,laboratory test,finite element simulation and a demonstration project.The scope of the work includes defining the principles for pavement piezoelectric energy harvesting technology,analyzing factors that influence the piezoelectric effect,developing the piezoelectric energy harvesting device for asphalt pavement,and fabricating a set of piezoelectric energy harvesting system that can convert the work of the vehicle-induced pavement deformation to electric energy.This system can potentially provide a large scale clean energy source for electric facilities along the road.This research mainly focused on the road piezoelectric energy harvesting technology pertinent to the characteristics of asphalt pavement and traffic loading.The main research activities and discoveries are presented as follows:(1)Based on the theory of piezoelectric power generation and characteristics of road traffic load,this dissertation studied the characteristics of piezoelectric power generation under vehicle dynamic load conditions,established the relationship between vehicle speed,axle load and piezoelectric energy output.(2)Based on the characteristics of the traffic load on the asphalt pavement,the mechanical performance and power generation performance of different piezoelectric ceramics and piezoelectric transducers are compared through literature review and laboratory tests.From this study piezoelectric PZT-5H is selected and a multi-stack structure is chosen as the piezoelectric transducer.(3)Finite element simulation and laboratory tests have been conducted to study the effect of piezoelectric connection mode,number of stacks,and the ratio of piezoelectric unit height to section diameter on the power generation performance.The results show that under the same loading conditions,parallel piezoelectric ceramic connection is better than series connection,and the power generation increases with the increase of number piezoelectric ceramic stacks and the increase of the ratio of piezoelectric unit height to the section diameter.Based on this evaluation,three stacks of parallel connected cylindrical piezoelectric disks are chosen for this study.(4)According to the traffic load characteristics,the influence of load magnitude,loading frequency,and temperature on the power generation performance is assessed through laboratory tests.The results show that energy output increases with the increase of load,following a cubic polynomial relationship;with the loading frequency increase,power generation has increased,but the increment rate decreases with frequency increasing.Temperature has a significant effect on piezoelectric power generation.In the range of-15 C?50 C,with the increase of temperature,the open circuit voltage of the piezoelectric unit decreases,while the charge amount increases and the output power increases.(5)This research has developed a piezoelectric energy harvester which is suitable for the axle loading of road traffic and the pavement conditions.Twelve sets of piezoelectric energy harvester are built,and the 30%GF nylon plastic is used as the packaging material.By studying the influence of the connection type between multi piezoelectric units on power generation performance,it is found that the output is higher if it is first rectified and then parallel connected.(6)According to the characteristics of piezoelectric power generation and based on the principle of synchronous charge extraction,an improved synchronous charge extraction circuit is designed and fabricated.The circuit can identify voltage peaks automatically and control the on and off the connection.The energy collection efficiency is above 16%which is 1.53 times the efficiency of the commercial energy collection chip,and it is not affected by the load and the application scope is wider.(7)Based on the above research,an integrated piezoelectric energy harvesting system has been designed and fabricated for a demonstration project to power the LED sign system.Twenty piezoelectric energy harvesters were installed in the surface layer of a pavement test section.The electricity generated by the passing vehicles is supplied to the LED sign board.The project demonstrated the feasibility of using piezoelectric power harvesting to power sign boards.The dissertation research served as part of the state 863 project and the project under Western Region Research Development Support plan of the Ministry of Transportation.Both project reports have been evaluated accepted by the expert panels.Overall,this study has developed a set of practical and integrated technology of piezoelectric energy collection,which may bring great social and economic benefits.It has potential impacts on energy saving and emission reduction.