Energy Harvesting for Tire Pressure Monitoring Systems

Tire pressure monitoring systems (TPMSs) predict over- and underinflated tires, and warn the driver in critical situations. Today, battery powered TPMSs suffer from limited energy. New sensor features such as friction determination or aquaplaning detection require even more energy and would significantly decrease the TPMS lifetime. Harvesting electrical energy inside the tire of a vehicle has been considered as a promising alternative to overcome the limited lifetime of a battery. However, it is a real challenge to design a system, that generates electrical energy at low velocities while being robust at 200 km/h where radial accelerations up to 20000 m/s2 occur. This work focusses on developing different electromechanical energy transducers that meet the high requirements of the automotive sector. Different approaches are addressed on how the change of acceleration and strain within the tire can be used to provide mechanical energy to the energy harvester. The energy harvester converts the mechanical energy into electrical energy. In this thesis, piezoelectric and electromagnetic transducers are discussed in depth, modelled as electromechanical networks. Since the transducers provide energy in the form of an AC voltage, but sensors require a DC voltage, various common interface circuits are compared, using LTspice and applying method of the stochastic signal analysis. Furthermore, a buck-boost converter concept for the electromagnetic energy harvester is optimized and improved. Experiments on a tire test rig validate the theoretically determined output and confirm that well designed energy harvesters in the tire can generate much more energy than required by an TPMS not only at high velocities but also at velocities as low as 20 km/h

Energy Harvesting from Hydraulic and Vibration Sources

This doctoral thesis, is divided in two main parts. The former is about load optimisation for a hydraulic energy harvester while the latter focuses on the design and fabrication of piezoelectric energy harvesters for the single supply pre-biasing circuit. An abstract for each part is reported below: \u88 Part I: The hydraulic power available in water pipes is usually wasted while it could be harvested and used to supply low power systems. To address this shortcoming, this study presents how load matching allows to harvest the maximum hydraulic power available in the environment. The hydraulic energy harvester considered in this study is composed of a hydraulic turbine and a permanent magnet generator. To estimate the optimal external load that maximises the power transfer, first a mathematical model of the harvester is introduced and then validated with experimental test. The benefit of this study consists in harvesting the maximum hydraulic power available for any input flow rate without changing physical parameters of the hydraulic turbine and the permanent magnet generator. Experimental and Simulation results show that by using the optimal load, the power transferred is maximum and consequently maximized power on the external load is available. \u88 Part II: The design and test of a novel screen printed piezoelectric energy harvester for the single supply pre-biasing (SSPB) circuit is presented. It was demonstrated in previous research that by using the SSPB circuit, power delivered to the load was over three times greater than that in the case of using a bridge rectifier circuit. For maximum power extraction from energy harvesters using the SSPB circuit, the SSPB switches must be triggered when the piezoelectric beam reaches its maximum point of displacement. Therefore, an accurate peak detection sensor is required. A new piezoelectric energy harvester integrating a small piezoelectric area for peak detection with a larger piezoelectric area for energy harvesting was designed and fabricated. The difference in capacitance between the peak detection sensor and the piezoelectric energy harvesting component leads to a phase difference between the two outputs if the load impedance is low. This phase difference can cause the switches to be triggered at the wrong time and thus reduce the efficiency of the SSPB circuit. A mathematical model was developed to study the phase dffierence. It was found both in simulation and experiments that impedance matching can be performed in order to eliminate the phase difference

Piezoelectric energy harvesting solutions

This paper reviews the state of the art in piezoelectric energy harvesting. It presents the basics of piezoelectricity and discusses materials choice. The work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions. The reviewed literature is compared based on power density and bandwidth. Lastly, the question of power conversion is addressed by reviewing various circuit solutions

Power Management Electronics

Accepted versio

Power electronic interfaces for piezoelectric energy harvesters

Motion-driven energy harvesters can replace batteries in low power wireless sensors, however selection of the optimal type of transducer for a given situation is difficult as the performance of the complete system must be taken into account in the optimisation. In this thesis, a complete piezoelectric energy harvester system model including a piezoelectric transducer, a power conditioning circuit, and a battery, is presented allowing for the first time a complete optimisation of such a system to be performed. Combined with previous work on modelling an electrostatic energy harvesting system, a comparison of the two transduction methods was performed. The results at 100 Hz indicate that for small MEMS devices at low accelerations, electrostatic harvesting systems outperform piezoelectric but the opposite is true as the size and acceleration increases. Thus the transducer type which achieves the best power density in an energy harvesting system for a given size, acceleration and operating frequency can be chosen. For resonant vibrational energy harvesting, piezoelectric transducers have received a lot of attention due to their MEMS manufacturing compatibility with research focused on the transduction method but less attention has been paid to the output power electronics. Detailed design considerations for a piezoelectric harvester interface circuit, known as single-supply pre-biasing (SSPB), are developed which experimentally demonstrate the circuit outperforming the next best known interface's theoretical limit. A new mode of operation for the SSPB circuit is developed which improves the power generation performance when the piezoelectric material properties have degraded. A solution for tracking the maximum power point as the excitation changes is also presented.Open Acces

An impact-based broadband aeroelastic energy harvester for concurrent wind and base vibration energy harvesting

© 2017 This paper proposes a novel broadband energy harvester to concurrently harvest energy from base vibrations and wind flows by utilizing a mechanical stopper. A problem for a conventional wind energy harvester is that it can only effectively harness energy from two types of excitations around its resonance frequency. The proposed design consists of a D-shape-sectioned bluff body attached to a piezoelectric cantilever, and a mechanical stopper fixed at the bottom of the cantilever which introduces piecewise linearity through its impact with the bluff body. The quasi-periodic oscillations are converted to periodic vibration due to the introduction of the mechanical stopper, which forces the two excitation frequencies to lock into each other. Broadened bandwidth for effective concurrent energy harvesting is thus achieved, and at the same time, the beam deflection is slightly mitigated and fully utilized for power conversion. The experiment shows that with the stopper-bluff body distance of 19.5 mm, the output power from the proposed harvesting device increases steadily from 3.0 mW at 17.3 Hz to 3.8 mW at 19.1 Hz at a wind speed of 5.5 m/s and a base acceleration of 0.5 g. A guideline for the stopper configuration is also provided for performance enhancement of the broadband concurrent wind and vibration energy harvester

A Cold-Startup SSHI Rectifier for Piezoelectric Energy Harvesters with Increased Open-Circuit Voltage

Piezoelectric vibration energy harvesting has drawn much research interest over the last decade towards the goal of enabling self-sustained wireless sensor nodes. In order to make use of the harvested energy, interface circuits are needed to rectify and manage the energy. Among all active interface circuits, SSHI (synchronized switch harvesting on inductor) and SECE (synchronous electric charge extraction) are widely employed due to their high energy efficiencies. However, the cold-startup issue still remains since an interface circuit needs a stable DC supply and the whole system is completely out of charge at the beginning of implementations or after a certain period of time without input vibration excitation. In this paper, a new cold-startup SSHI interface circuit is presented, which dynamically increases the open-circuit voltage generated from the piezoelectric transducer (PT) in cold-state to start the system under much lower excitation levels. The proposed circuit is designed and fabricated in a 0.18 um CMOS process and experimentally validated together with a custom MEMS (microelectromechanical systems) harvester, which is designed with split electrodes to work with the proposed power extraction circuit. The experiments were performed to start the system from the cold state under variable excitation levels. The results show that the proposed system lowers the required excitation level by at least 50% in order to perform a cold-startup. This aids restarting of the energy harvesting system under low excitation levels each time it enters the cold state