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Bilge Demir - One of the best experts on this subject based on the ideXlab platform.

  • an investigation of mechanical and metallurgical properties of explosive welded aluminum dual phase steel
    Materials Letters, 2008
    Co-Authors: Mustafa Acarer, Bilge Demir
    Abstract:

    Abstract The aim of this paper is investigation of microstructure and property relationship in aluminum–HSLA steel and aluminum–dual phase steel Bimetals fabricated by explosive welding technique. Dual phase steel was produced by intercritical annealing and water quenching from 1.45Mn–0.2Si–0.186C HSLA steel. Hardness, tensile shear strength, tensile strength, toughness and microstructure of explosively welded aluminum–HSLA steel and aluminum–dual phase steel were evaluated. Both Bimetals have a straight bonding interface. It was also seen that plastic deformation of dual phase steel was higher than HSLA steel near interfaces of Bimetals. The hardness was increased near the bond interface of Bimetals. Tensile and tensile shear strength tests showed that aluminum–dual phase steel is superior than aluminum–HSLA steel. Also, impact toughness of aluminum–dual phase steel was found significantly higher than that of aluminum–HSLA steel.

  • An investigation of mechanical and metallurgical properties of explosive welded aluminum–dual phase steel
    Materials Letters, 2008
    Co-Authors: Mustafa Acarer, Bilge Demir
    Abstract:

    Abstract The aim of this paper is investigation of microstructure and property relationship in aluminum–HSLA steel and aluminum–dual phase steel Bimetals fabricated by explosive welding technique. Dual phase steel was produced by intercritical annealing and water quenching from 1.45Mn–0.2Si–0.186C HSLA steel. Hardness, tensile shear strength, tensile strength, toughness and microstructure of explosively welded aluminum–HSLA steel and aluminum–dual phase steel were evaluated. Both Bimetals have a straight bonding interface. It was also seen that plastic deformation of dual phase steel was higher than HSLA steel near interfaces of Bimetals. The hardness was increased near the bond interface of Bimetals. Tensile and tensile shear strength tests showed that aluminum–dual phase steel is superior than aluminum–HSLA steel. Also, impact toughness of aluminum–dual phase steel was found significantly higher than that of aluminum–HSLA steel.

Mustafa Acarer - One of the best experts on this subject based on the ideXlab platform.

  • an investigation of mechanical and metallurgical properties of explosive welded aluminum dual phase steel
    Materials Letters, 2008
    Co-Authors: Mustafa Acarer, Bilge Demir
    Abstract:

    Abstract The aim of this paper is investigation of microstructure and property relationship in aluminum–HSLA steel and aluminum–dual phase steel Bimetals fabricated by explosive welding technique. Dual phase steel was produced by intercritical annealing and water quenching from 1.45Mn–0.2Si–0.186C HSLA steel. Hardness, tensile shear strength, tensile strength, toughness and microstructure of explosively welded aluminum–HSLA steel and aluminum–dual phase steel were evaluated. Both Bimetals have a straight bonding interface. It was also seen that plastic deformation of dual phase steel was higher than HSLA steel near interfaces of Bimetals. The hardness was increased near the bond interface of Bimetals. Tensile and tensile shear strength tests showed that aluminum–dual phase steel is superior than aluminum–HSLA steel. Also, impact toughness of aluminum–dual phase steel was found significantly higher than that of aluminum–HSLA steel.

  • An investigation of mechanical and metallurgical properties of explosive welded aluminum–dual phase steel
    Materials Letters, 2008
    Co-Authors: Mustafa Acarer, Bilge Demir
    Abstract:

    Abstract The aim of this paper is investigation of microstructure and property relationship in aluminum–HSLA steel and aluminum–dual phase steel Bimetals fabricated by explosive welding technique. Dual phase steel was produced by intercritical annealing and water quenching from 1.45Mn–0.2Si–0.186C HSLA steel. Hardness, tensile shear strength, tensile strength, toughness and microstructure of explosively welded aluminum–HSLA steel and aluminum–dual phase steel were evaluated. Both Bimetals have a straight bonding interface. It was also seen that plastic deformation of dual phase steel was higher than HSLA steel near interfaces of Bimetals. The hardness was increased near the bond interface of Bimetals. Tensile and tensile shear strength tests showed that aluminum–dual phase steel is superior than aluminum–HSLA steel. Also, impact toughness of aluminum–dual phase steel was found significantly higher than that of aluminum–HSLA steel.

Pierre-jean Cottinet - One of the best experts on this subject based on the ideXlab platform.

  • Coupling of PZT Thin Films with Bimetallic Strip Heat Engines for Thermal Energy Harvesting
    Sensors, 2018
    Co-Authors: J Boughaleb, Daniel Guyomar, Thomas Skotnicki, Stephane Monfray, Arthur Arnaud, Benoit Guiffard, Raynald Séveno, Pierre-jean Cottinet
    Abstract:

    A thermal energy harvester based on a double transduction mechanism and which converts thermal energy into electrical energy by means of piezoelectric membranes and Bimetals, has previously been developed and widely presented in the literature In such a device, the thermo-mechanical conversion is ensured by a bimetal whereas the electro-mechanical conversion is generated by a piezoelectric ceramic. However, it has been shown that only 19% of the mechanical energy delivered by the bimetal during its snap is converted into electrical energy. To extract more energy from the bimetallic strip and to increase the transduction efficiency, a new way to couple piezoelectric materials with Bimetals has thus been explored through direct deposition of piezoelectric layers on Bimetals. This paper consequently presents an alternative way to harvest heat, based on piezoelectric bimetallic strip heat engines and presents a proof of concept of such a system. In this light, different PZT (Lead zirconate titanate) thin films were synthesized directly on aluminium foils and were attached to the Bimetals using conductive epoxy. The fabrication process of each sample is presented herein as well as the experimental tests carried out on the devices. Throughout this study, different thicknesses of the piezoelectric layers and substrates were tested to determine the most powerful configuration. Finally, the study also gives some guidelines for future improvements of piezoelectric Bimetals.

  • Dynamic study for performance improvements of a thermo-mechanically bistable heat engine
    2015
    Co-Authors: J Boughaleb, G Pitone, Frederic Boeuf, S. Quenard, Daniel Guyomar, Stephane Monfray, Pierre-jean Cottinet, Arthur Arnaud, Thomas Skotnicki
    Abstract:

    This paper focuses on a thermal study of a thermal energy harvester based on the coupling of a bimetallic strip heat engine with a piezoelectric membrane for wasted heat scavenging. Such a harvester is dedicated to power autonomous systems such as wireless sensor nodes. For a better understanding of the working principle of the system, it is compulsory to have a good understanding of the thermal specificities and phenomenon taking place inside the harvester. Attention is consequently focused on the thermal modeling of the harvester in static mode using the equivalence between the electrical and thermal quantities. This first modeling step allowed the improvement of the thermal properties inside the system by increasing the thermal gradient across it. However, the bimetal being the active part of the system has not been taken into account in this model and shadow zones persisted regarding the bimetal operation windows as a function of its snapping temperatures and hysteresis. To overcome this, a dynamic model is proposed in this paper taking into account the bimetal as a switched capacitance alternatively in contact with the hot source and the cold surface. This last model completed the static one by predicting the bimetal’s operation windows in function of its intrinsic properties and the operation range evolution in function of the snapping temperature first and then in function of the bimetal thermal hysteresis. Moreover, experimental measurements enable to validate the proposed model and to point out the most powerful Bimetals for scavenging higher amounts of power.

  • Analysis of the thermal impact of a bimetal on the dynamic behavior of a thermal energy harvester
    Sensors and Actuators A-physical, 2015
    Co-Authors: J Boughaleb, Frederic Boeuf, A Arnaud, S. Quenard, Daniel Guyomar, Stephane Monfray, Pierre-jean Cottinet, Thomas Skotnicki
    Abstract:

    This paper reports on the dynamic analysis of the bimetallic strip of a thermal energy harvester based on a two-step conversion mechanism. The system is primarily based on a thermo-mechanical transduction ensured by a bimetal that is then coupled to an electro-mechanical transduction ensured by a piezoelectric membrane. Previous studies have shown that the bimetal that acts as a shuttle between the hot source and the cold surface does not impact the stationary thermal behavior of the device. However, this bimetal considered as a self-oscillating heat engine does impact the functioning of the structure by shifting its corresponding temperature range. The present study consequently deals with a dynamic model of the harvester using a lumped parameter representation that confirms the temperature shifts observed experimentally. A bimetal that is bounded to start snapping at 70 °C and to snap down at 67 °C only starts snapping at 84 °C once mounted in the structure. Thus, the purpose of this paper is about to explain this phenomenon and propose a model to predict the real snap temperature of any bimetal once it is introduced in a harvester, as this would be a huge advance. This paper thus solves the problem of experimentally finding the snap and the snap-back temperature of any bimetal once mounted in a harvester and proposes many applications to the established dynamic model. For example, one is able to predict the intrinsic snap-up and -down temperatures of a bimetal as a function of its desired snapping temperature once it is introduced in the harvester. Moreover, experimental measurements have been carried out on various Bimetals thus making it possible to experimentally validate the dynamic model. The model finally gives the main guidelines for bimetal design from a thermal point of view.

  • Flexible bimetal and piezoelectric based thermal to electrical energy converters
    Sensors and Actuators A-physical, 2014
    Co-Authors: Onoriu Puscasu, J Boughaleb, Dario Rapisarda, Elodie Rouvière, G. Delepierre, G Pitone, Stephane Monfray, Christophe Maitre, Pierre-jean Cottinet, Frederic Boeuf
    Abstract:

    Abstract A new approach to thermal energy harvesting is presented in this paper. The devices we fabricate are composed of thermal Bimetals and piezoelectric membranes. Bimetals that show a snapping behavior when heated are used. When brought to a predetermined temperature, a bimetal snaps abruptly from one position to another. In this step a thermal to mechanical conversion takes place. The provided mechanical energy is then converted into electricity by a piezoelectric membrane. When shocked by the bimetal, the piezoelectric material provides voltage pulses that can be recovered with the help of an energy harvesting circuit. With this approach we have managed to build thin devices that are assembled into matrixes on a flexible substrate, and work at temperatures close to ambient. The key point of their functioning is their intrinsic ability to keep a high temperature gradient when heated and thus work without a heat sink. This is a substantial advantage over the thermal harvesters based on Seebeck effect that need a bulky heat sink for optimal performance. Pulse frequencies of 2.4 Hz have been reached, with an electrical energy per pulse up to 31 μJ. The mechanical energy per cycle delivered by a bimetal is bigger and can reach 770 μJ for a 3 °C temperature difference operation. These results have been obtained while cooling with ambient air, without a heat sink. The main characteristics of our devices and ways to improve the performance are discussed in this paper.

  • Flexible bimetal and piezoelectric based thermal to electrical energy converters
    Sensors and Actuators A: Physical, 2014
    Co-Authors: Onoriu Puscasu, J Boughaleb, Dario Rapisarda, Elodie Rouvière, G. Delepierre, G Pitone, Stephane Monfray, Christophe Maitre, Pierre-jean Cottinet, Frederic Boeuf
    Abstract:

    A new approach to thermal energy harvesting is presented in this paper. The devices we fabricate are composed of thermal Bimetals and piezoelectric membranes. Bimetals that show a snapping behavior when heated are used. When brought to a predetermined temperature, a bimetal snaps abruptly from one position to another. In this step a thermal to mechanical conversion takes place. The provided mechanical energy is then converted into electricity by a piezoelectric membrane. When shocked by the bimetal, the piezoelectric material provides voltage pulses that can be recovered with the help of an energy harvesting circuit. With this approach we have managed to build thin devices that are assembled into matrixes on a flexible substrate, and work at temperatures close to ambient. The key point of their functioning is their intrinsic ability to keep a high temperature gradient when heated and thus work without a heat sink. This is a substantial advantage over the thermal harvesters based on Seebeck effect that need a bulky heat sink for optimal performance. Pulse frequencies of 2.4 Hz have been reached, with an electrical energy per pulse up to 31 μJ. The mechanical energy per cycle delivered by a bimetal is bigger and can reach 770 μJ for a 3 °C temperature difference operation. These results have been obtained while cooling with ambient air, without a heat sink. The main characteristics of our devices and ways to improve the performance are discussed in this paper. © 2014 Elsevier B.V.

J Boughaleb - One of the best experts on this subject based on the ideXlab platform.

  • Coupling of PZT Thin Films with Bimetallic Strip Heat Engines for Thermal Energy Harvesting
    Sensors, 2018
    Co-Authors: J Boughaleb, Daniel Guyomar, Thomas Skotnicki, Stephane Monfray, Arthur Arnaud, Benoit Guiffard, Raynald Séveno, Pierre-jean Cottinet
    Abstract:

    A thermal energy harvester based on a double transduction mechanism and which converts thermal energy into electrical energy by means of piezoelectric membranes and Bimetals, has previously been developed and widely presented in the literature In such a device, the thermo-mechanical conversion is ensured by a bimetal whereas the electro-mechanical conversion is generated by a piezoelectric ceramic. However, it has been shown that only 19% of the mechanical energy delivered by the bimetal during its snap is converted into electrical energy. To extract more energy from the bimetallic strip and to increase the transduction efficiency, a new way to couple piezoelectric materials with Bimetals has thus been explored through direct deposition of piezoelectric layers on Bimetals. This paper consequently presents an alternative way to harvest heat, based on piezoelectric bimetallic strip heat engines and presents a proof of concept of such a system. In this light, different PZT (Lead zirconate titanate) thin films were synthesized directly on aluminium foils and were attached to the Bimetals using conductive epoxy. The fabrication process of each sample is presented herein as well as the experimental tests carried out on the devices. Throughout this study, different thicknesses of the piezoelectric layers and substrates were tested to determine the most powerful configuration. Finally, the study also gives some guidelines for future improvements of piezoelectric Bimetals.

  • Dynamic study for performance improvements of a thermo-mechanically bistable heat engine
    2015
    Co-Authors: J Boughaleb, G Pitone, Frederic Boeuf, S. Quenard, Daniel Guyomar, Stephane Monfray, Pierre-jean Cottinet, Arthur Arnaud, Thomas Skotnicki
    Abstract:

    This paper focuses on a thermal study of a thermal energy harvester based on the coupling of a bimetallic strip heat engine with a piezoelectric membrane for wasted heat scavenging. Such a harvester is dedicated to power autonomous systems such as wireless sensor nodes. For a better understanding of the working principle of the system, it is compulsory to have a good understanding of the thermal specificities and phenomenon taking place inside the harvester. Attention is consequently focused on the thermal modeling of the harvester in static mode using the equivalence between the electrical and thermal quantities. This first modeling step allowed the improvement of the thermal properties inside the system by increasing the thermal gradient across it. However, the bimetal being the active part of the system has not been taken into account in this model and shadow zones persisted regarding the bimetal operation windows as a function of its snapping temperatures and hysteresis. To overcome this, a dynamic model is proposed in this paper taking into account the bimetal as a switched capacitance alternatively in contact with the hot source and the cold surface. This last model completed the static one by predicting the bimetal’s operation windows in function of its intrinsic properties and the operation range evolution in function of the snapping temperature first and then in function of the bimetal thermal hysteresis. Moreover, experimental measurements enable to validate the proposed model and to point out the most powerful Bimetals for scavenging higher amounts of power.

  • Analysis of the thermal impact of a bimetal on the dynamic behavior of a thermal energy harvester
    Sensors and Actuators A-physical, 2015
    Co-Authors: J Boughaleb, Frederic Boeuf, A Arnaud, S. Quenard, Daniel Guyomar, Stephane Monfray, Pierre-jean Cottinet, Thomas Skotnicki
    Abstract:

    This paper reports on the dynamic analysis of the bimetallic strip of a thermal energy harvester based on a two-step conversion mechanism. The system is primarily based on a thermo-mechanical transduction ensured by a bimetal that is then coupled to an electro-mechanical transduction ensured by a piezoelectric membrane. Previous studies have shown that the bimetal that acts as a shuttle between the hot source and the cold surface does not impact the stationary thermal behavior of the device. However, this bimetal considered as a self-oscillating heat engine does impact the functioning of the structure by shifting its corresponding temperature range. The present study consequently deals with a dynamic model of the harvester using a lumped parameter representation that confirms the temperature shifts observed experimentally. A bimetal that is bounded to start snapping at 70 °C and to snap down at 67 °C only starts snapping at 84 °C once mounted in the structure. Thus, the purpose of this paper is about to explain this phenomenon and propose a model to predict the real snap temperature of any bimetal once it is introduced in a harvester, as this would be a huge advance. This paper thus solves the problem of experimentally finding the snap and the snap-back temperature of any bimetal once mounted in a harvester and proposes many applications to the established dynamic model. For example, one is able to predict the intrinsic snap-up and -down temperatures of a bimetal as a function of its desired snapping temperature once it is introduced in the harvester. Moreover, experimental measurements have been carried out on various Bimetals thus making it possible to experimentally validate the dynamic model. The model finally gives the main guidelines for bimetal design from a thermal point of view.

  • Flexible bimetal and piezoelectric based thermal to electrical energy converters
    Sensors and Actuators A-physical, 2014
    Co-Authors: Onoriu Puscasu, J Boughaleb, Dario Rapisarda, Elodie Rouvière, G. Delepierre, G Pitone, Stephane Monfray, Christophe Maitre, Pierre-jean Cottinet, Frederic Boeuf
    Abstract:

    Abstract A new approach to thermal energy harvesting is presented in this paper. The devices we fabricate are composed of thermal Bimetals and piezoelectric membranes. Bimetals that show a snapping behavior when heated are used. When brought to a predetermined temperature, a bimetal snaps abruptly from one position to another. In this step a thermal to mechanical conversion takes place. The provided mechanical energy is then converted into electricity by a piezoelectric membrane. When shocked by the bimetal, the piezoelectric material provides voltage pulses that can be recovered with the help of an energy harvesting circuit. With this approach we have managed to build thin devices that are assembled into matrixes on a flexible substrate, and work at temperatures close to ambient. The key point of their functioning is their intrinsic ability to keep a high temperature gradient when heated and thus work without a heat sink. This is a substantial advantage over the thermal harvesters based on Seebeck effect that need a bulky heat sink for optimal performance. Pulse frequencies of 2.4 Hz have been reached, with an electrical energy per pulse up to 31 μJ. The mechanical energy per cycle delivered by a bimetal is bigger and can reach 770 μJ for a 3 °C temperature difference operation. These results have been obtained while cooling with ambient air, without a heat sink. The main characteristics of our devices and ways to improve the performance are discussed in this paper.

  • Flexible bimetal and piezoelectric based thermal to electrical energy converters
    Sensors and Actuators A: Physical, 2014
    Co-Authors: Onoriu Puscasu, J Boughaleb, Dario Rapisarda, Elodie Rouvière, G. Delepierre, G Pitone, Stephane Monfray, Christophe Maitre, Pierre-jean Cottinet, Frederic Boeuf
    Abstract:

    A new approach to thermal energy harvesting is presented in this paper. The devices we fabricate are composed of thermal Bimetals and piezoelectric membranes. Bimetals that show a snapping behavior when heated are used. When brought to a predetermined temperature, a bimetal snaps abruptly from one position to another. In this step a thermal to mechanical conversion takes place. The provided mechanical energy is then converted into electricity by a piezoelectric membrane. When shocked by the bimetal, the piezoelectric material provides voltage pulses that can be recovered with the help of an energy harvesting circuit. With this approach we have managed to build thin devices that are assembled into matrixes on a flexible substrate, and work at temperatures close to ambient. The key point of their functioning is their intrinsic ability to keep a high temperature gradient when heated and thus work without a heat sink. This is a substantial advantage over the thermal harvesters based on Seebeck effect that need a bulky heat sink for optimal performance. Pulse frequencies of 2.4 Hz have been reached, with an electrical energy per pulse up to 31 μJ. The mechanical energy per cycle delivered by a bimetal is bigger and can reach 770 μJ for a 3 °C temperature difference operation. These results have been obtained while cooling with ambient air, without a heat sink. The main characteristics of our devices and ways to improve the performance are discussed in this paper. © 2014 Elsevier B.V.

Frederic Boeuf - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic study for performance improvements of a thermo-mechanically bistable heat engine
    2015
    Co-Authors: J Boughaleb, G Pitone, Frederic Boeuf, S. Quenard, Daniel Guyomar, Stephane Monfray, Pierre-jean Cottinet, Arthur Arnaud, Thomas Skotnicki
    Abstract:

    This paper focuses on a thermal study of a thermal energy harvester based on the coupling of a bimetallic strip heat engine with a piezoelectric membrane for wasted heat scavenging. Such a harvester is dedicated to power autonomous systems such as wireless sensor nodes. For a better understanding of the working principle of the system, it is compulsory to have a good understanding of the thermal specificities and phenomenon taking place inside the harvester. Attention is consequently focused on the thermal modeling of the harvester in static mode using the equivalence between the electrical and thermal quantities. This first modeling step allowed the improvement of the thermal properties inside the system by increasing the thermal gradient across it. However, the bimetal being the active part of the system has not been taken into account in this model and shadow zones persisted regarding the bimetal operation windows as a function of its snapping temperatures and hysteresis. To overcome this, a dynamic model is proposed in this paper taking into account the bimetal as a switched capacitance alternatively in contact with the hot source and the cold surface. This last model completed the static one by predicting the bimetal’s operation windows in function of its intrinsic properties and the operation range evolution in function of the snapping temperature first and then in function of the bimetal thermal hysteresis. Moreover, experimental measurements enable to validate the proposed model and to point out the most powerful Bimetals for scavenging higher amounts of power.

  • Analysis of the thermal impact of a bimetal on the dynamic behavior of a thermal energy harvester
    Sensors and Actuators A-physical, 2015
    Co-Authors: J Boughaleb, Frederic Boeuf, A Arnaud, S. Quenard, Daniel Guyomar, Stephane Monfray, Pierre-jean Cottinet, Thomas Skotnicki
    Abstract:

    This paper reports on the dynamic analysis of the bimetallic strip of a thermal energy harvester based on a two-step conversion mechanism. The system is primarily based on a thermo-mechanical transduction ensured by a bimetal that is then coupled to an electro-mechanical transduction ensured by a piezoelectric membrane. Previous studies have shown that the bimetal that acts as a shuttle between the hot source and the cold surface does not impact the stationary thermal behavior of the device. However, this bimetal considered as a self-oscillating heat engine does impact the functioning of the structure by shifting its corresponding temperature range. The present study consequently deals with a dynamic model of the harvester using a lumped parameter representation that confirms the temperature shifts observed experimentally. A bimetal that is bounded to start snapping at 70 °C and to snap down at 67 °C only starts snapping at 84 °C once mounted in the structure. Thus, the purpose of this paper is about to explain this phenomenon and propose a model to predict the real snap temperature of any bimetal once it is introduced in a harvester, as this would be a huge advance. This paper thus solves the problem of experimentally finding the snap and the snap-back temperature of any bimetal once mounted in a harvester and proposes many applications to the established dynamic model. For example, one is able to predict the intrinsic snap-up and -down temperatures of a bimetal as a function of its desired snapping temperature once it is introduced in the harvester. Moreover, experimental measurements have been carried out on various Bimetals thus making it possible to experimentally validate the dynamic model. The model finally gives the main guidelines for bimetal design from a thermal point of view.

  • Flexible bimetal and piezoelectric based thermal to electrical energy converters
    Sensors and Actuators A-physical, 2014
    Co-Authors: Onoriu Puscasu, J Boughaleb, Dario Rapisarda, Elodie Rouvière, G. Delepierre, G Pitone, Stephane Monfray, Christophe Maitre, Pierre-jean Cottinet, Frederic Boeuf
    Abstract:

    Abstract A new approach to thermal energy harvesting is presented in this paper. The devices we fabricate are composed of thermal Bimetals and piezoelectric membranes. Bimetals that show a snapping behavior when heated are used. When brought to a predetermined temperature, a bimetal snaps abruptly from one position to another. In this step a thermal to mechanical conversion takes place. The provided mechanical energy is then converted into electricity by a piezoelectric membrane. When shocked by the bimetal, the piezoelectric material provides voltage pulses that can be recovered with the help of an energy harvesting circuit. With this approach we have managed to build thin devices that are assembled into matrixes on a flexible substrate, and work at temperatures close to ambient. The key point of their functioning is their intrinsic ability to keep a high temperature gradient when heated and thus work without a heat sink. This is a substantial advantage over the thermal harvesters based on Seebeck effect that need a bulky heat sink for optimal performance. Pulse frequencies of 2.4 Hz have been reached, with an electrical energy per pulse up to 31 μJ. The mechanical energy per cycle delivered by a bimetal is bigger and can reach 770 μJ for a 3 °C temperature difference operation. These results have been obtained while cooling with ambient air, without a heat sink. The main characteristics of our devices and ways to improve the performance are discussed in this paper.

  • Flexible bimetal and piezoelectric based thermal to electrical energy converters
    Sensors and Actuators A: Physical, 2014
    Co-Authors: Onoriu Puscasu, J Boughaleb, Dario Rapisarda, Elodie Rouvière, G. Delepierre, G Pitone, Stephane Monfray, Christophe Maitre, Pierre-jean Cottinet, Frederic Boeuf
    Abstract:

    A new approach to thermal energy harvesting is presented in this paper. The devices we fabricate are composed of thermal Bimetals and piezoelectric membranes. Bimetals that show a snapping behavior when heated are used. When brought to a predetermined temperature, a bimetal snaps abruptly from one position to another. In this step a thermal to mechanical conversion takes place. The provided mechanical energy is then converted into electricity by a piezoelectric membrane. When shocked by the bimetal, the piezoelectric material provides voltage pulses that can be recovered with the help of an energy harvesting circuit. With this approach we have managed to build thin devices that are assembled into matrixes on a flexible substrate, and work at temperatures close to ambient. The key point of their functioning is their intrinsic ability to keep a high temperature gradient when heated and thus work without a heat sink. This is a substantial advantage over the thermal harvesters based on Seebeck effect that need a bulky heat sink for optimal performance. Pulse frequencies of 2.4 Hz have been reached, with an electrical energy per pulse up to 31 μJ. The mechanical energy per cycle delivered by a bimetal is bigger and can reach 770 μJ for a 3 °C temperature difference operation. These results have been obtained while cooling with ambient air, without a heat sink. The main characteristics of our devices and ways to improve the performance are discussed in this paper. © 2014 Elsevier B.V.