- Generování elektrické energie z okolí (autonomní zdroje elektrické energie) Ing. Zdeněk HADAŠ, Ph.D. Ústav mechaniky těles, mechatroniky a biomechaniky Fakulta strojního inženýrství Vysoké učení technické v Brně Technická 2896/2, Brno 616 69
Introduction This presentation deals with overview of unique ways of generating energy from surroundings. These ways of generating energy are commonly called as Energy Harvesting and this source can be used for autonomous feeding of remote electronics, low power devices and wireless sensors. Nowadays power sources can be classified as: Energy reservoir (batteries, supercapacitors, fuel cells, etc.) Power distribution methods (wiring, laser, RF, acoustic, etc.) Energy harvesting methods (energy/power scavenging) Definition: An energy harvesting device generates electric energy from its surroundings using some energy conversion method. Therefore, the energy harvesting devices here considered do not consume any fuel or substance. On the other hand, as the environment energy levels are very low (at least for today s electronic devices requirements).
Idea of Energy Harvesting The current electronic circuits and applications are capable to operate at microwatt power levels and it is feasible to power them from non-traditional energy sources. This leads to use energy harvesting technologies, which provide power to charge, supplement or replace batteries in systems where battery use is inconvenient, impractical, expensive or dangerous. Energy harvesting technologies compete with other traditional sources of electricity for small electronics, Wireless Sensor Networks and electrical devices. The lifetime of electronic devices is guaranteed up to ten years but the lifetime of their batteries is typically only a few years.
Energy Harvesting The output power of energy harvesting device depends on the ambient energy and converting efficiency of energy harvester. The amount of ambient energy is ordinarily minute and the term energy harvesting is usually used when we speaking about small autonomous devices, like MEMS or low voltage applications, wireless sensor networks, etc. This devices and applications are powered by batteries in present time. available energy: Solar energy RF radiation Industrial system Energy Harvesting Application Ambient environment Mechanical energy Human energy Thermal energy Other energy
Common sources of ambient energy Radiation Solar energy Electromagnetic radiation (light, RF source) Thermal Energy waste energy from heaters, friction sources, etc. Mechanical Energy Vibration of industrial systems Random moving of system kinetic energy Deformation, Pressure (mechanical stress and strain) Medium flow - Liquid flow, - Natural energy of flow from the environment such as wind, rivers, ocean currents, ocean waves, rain, etc. Human Body Human passive energy (body moving, walking - running, breathing, etc.) Human active energy (pedaling, shaking, typing, etc.) Other Energy from chemical and biological sources
Schematic diagram of energy harvesting system The choice of suitable energy harvesting devices design and physical method of energy conversion are very important for efficient harvesting of energy. The efficiency of energy harvesting is in nature very low. The obtained energy can be used to recharge a secondary battery (supercapacitors) or, in some cases, to power directly the electronics. The output voltage and current of the generators is transient and discontinuous in nature, and usually it must be converted to a DC signal. Ambient Energy Physical Principle Energy Harvester Power Management (rectifying, stabilization, charging, etc. ) Load, Powered device (electronics, sensor, etc.) Energy Storage Capacitors (supercapacitors) or rechargeable batteries
Potential Energy Harvesting Applications Sources of energy Energy Harvesting Systems Applications Solar energy - Photovoltaic cells - Remote electronics, etc. Thermal gradient - TEG Thermoelectric generators (Seebeck effect) - Aeronautic/automotive industry, etc. - Human body heat (e.g. watches) - Frictions Human body movement - Passive - Health monitoring (e.g. pacemaker, earpiece) - Active (walking, typing, etc.) - Source for portable devices (army) - Source for MP3, mobile phones Random movement - Random oscillation - Generator inside tires - Random load, shocks - Generator for traffic monitoring - Fluid flow, etc. - Piezo strips (eel) generators Vibrations - Resonance system - Electro-static generators - MEMS - Piezo-electric generators - Electro-magnetic generators
Comparisons of ambient energy Power Source P/cm 3 (mw/cm 3 ) Solar (outside) 15000 * Solar (inside) 10 * Temperature gradient 40 * Passive Human Power 330 Air flow 380 Vibrations 100-500 * Sources of metric are power per square centimeter rather than power per ccm Demonstrated from a 5ºC temperature differential Assumes air velocity of 5 m/s and 5 % conversion efficiency Harvested power depends on level of vibration my research source: Shad Roundy research - Berkeley University
Power requirements of electronics and power of energy harvesting products (www.idtechex.com) with shown Brno University of Technology vibration power generators.
Konarka vision of ubiquitous energy harvesting
Consumer market total value by sector
ENERGY HARVESTING TECHNOLOGIES
Solar energy four generations of well-known photovoltaic cells are available the efficiency is in range 15 40 %
Applications EnOcean GmbH
Thermal Energy Well-known Seiko Thermic watches: Thermal energy harvesting devices could use the thermal energy of different sources like machines, human or other natural sources. Thermogenerator is devices which convert heat (temperature gradient) directly into electrical energy. It commonly works on the principle of the Seebeck effect, with typical efficiencies of around 5-10%. Thermo Life Energy Corp.: Tellurex s module Micropelt Power Generation:
Other Applications
Mechanical energy A mechanical energy is occurred almost in each engineering system (movement of mechanical parts or medium, vibration and deformation) and in nature as wind, ocean waves, ocean current, rivers or rain etc. An acoustic energy can include in mechanical energy as a wave motion through air or another materials. These available sources of ambient mechanical energy (kinetic energy) can use for harvesting of useful electrical energy: Vibration Random moving Medium flow Human energy
Vibration Several wireless applications operate in environments excited by vibration. The vibration is one of the most suitably energy sources for wireless application. The generic vibration power generator consists of: mechanical resonance mechanism, energy transducer: piezoelectric, electromagnetic, electrostatic, magnetostriction. electrical load power management and powered electronics.
Energy Harvesting from Vibration as Complex Mechatronic System
Electro-mechanical energy transducers: Electromagnetic generator Piezoelectric generator Electrostatic generator MEMS
Comparison of energy transducer principles: Principle Characteristic Electrostatic Piezoelectric Electromagnetic + Potential for integration with MEMS (frequency of several khz) - Require a separate voltage source to initiate the conversion process - Low power - Mechanical stop limits must be included + Suitable as source for frequency of vibration higher than ~ 100 Hz + High voltage - High impedance, low current + Suitable as source for frequency of vibration up to 50 Hz (100 Hz) + Sufficient voltage if the volume of generator is not significant limitation - Generally low voltage The magnetostriction material works with similar principle as piezoceramics but a coil is required to electro-mechanical conversion. It indicate characteristic of this generator in field between piezoelectric and electromagnetic generator.
Electromagnetic generator Piezoelectric generator Electrostatic generator Power requirements of small electronic products including Wireless Sensor Networks (WSN) and GSM mobile phones and the types of battery employed
Available Commercial Products Perpetuum Ltd. http://www.perpetuum.co.uk This company developed several products of microgenerator which generates electrical energy from vibration frequency range 17 120 Hz. Ferro Solutions http://www.ferrosi.com/ Operating frequency 60 Hz Weight 289 grams Q factor around 28 Output voltage 3.3 V, vibration 0.025 G 0.8 mw, vibration 0.05 G 3.1 mw, vibration 0.1 G 10.8 mw. PMG17-100 Operating frequency 100 Hz Output voltage 4.5 V, vibration 0.025 G max 1.1 mw, vibration 0.5 G max 5 mw, vibration 1 G max 17 mw, weight 680 grams.
Piezoelectric generators The piezoelectric generator harvests energy from strain of piezomaterial, which is component of resonance mechanism. An excited movement of mass causes deformation of piezo-material and due to strain inside the piezo-material provides voltage. The ceramics lead zirconate titanate (PZT) substrate is usually used for energy harvesting application. AdaptivEnergy (AE) has developed the Joule-Thief energy harvesting solution
Other application of piezoelectric generator: Non-resonance (Inertial) generators tires, manipulators, human and random movement, etc. Non-resonance generator from Berkley University: Power paving
PulseSwitch Systems makes piezoelectric wireless switches that do not need a battery Piezoelectric road
Freeplay wind up radio in Africa Other applications of Energy Harvesting:
Other applications of Energy Harvesting: Flag or ell piezoelectric generators medium flow produces deformation of piezoelectric strip Wind powered phone charger
Self-powered Wireless Sensor Technology from EnOcean These products are presented as service-free energy converters with the following options: Energy from a switching operation (button pressure): Electrodynamic energy converter - user-dependent energy generation from button motion Solar cells Thermal converter Rotation converter Vibration converter
Number of cases by type of harvesting
Profiled organisations active in energy harvesting by country, numbers rounded.
Currently, the most of energy harvesting applications is tested in the laboratory and practical applications of some energy harvesting technologies have been used in several engineering applications. Main players in energy harvesting fields are companies: AdaptivEnergy, EnOcean, Holst Centre, Lumedyne, MEMS@Mit, Micropelt, Microstrain, Morgan Electro Ceramics, Piezo TAG, Perpetuum, Thermo Life, TPL Micropower, Transense Technology, Visityre. In total, there are about 500 organizations working on energy harvesting and about half of them being academic.
Brno University of Technology and WISE project http://www.wise-project.org - Integrated WIreless SEnsing WISE research the way to integrate wireless technologies, in the aircraft systems environment, for which the sensor powering has to be autonomous. Our University cooperates on this project and the self-power generation was investigated and it could be integrated at the sensor level. Operating frequency 17 Hz 34 Hz Weight 120 grams 100 grams Effective Volume 80 ccm 40 ccm Vibration 0.1 G rms Vibration 0.5 G rms 5 V DC/ 5 mw rms 9 V DC/ 30 mw rms 4 V DC/ 5 mw 9 V DC/ 35 mw rms Energy harvester 17 Hz Optimal load 3 9 kw 1 3 kw
Development (APU) (RAGB) (TGB)
VIBRATION POWER GENERATOR 17 Hz Performance Data of Developed Vibration Power Generator: Parameter (Condition) Value Unit Weight 135 g Volume 50x40x40 mm 80 cm³ Working Frequency 17 Hz Coil (enamelled copper wire with diameter 0.05 mm) 2000 turns Inner Resistance of Coil 1600 W Output Voltage DC (vibration 0.3 G peak; load 9.2 kw) 13.5 V rms Output Power (vibration 0.3 G peak; load 9.2 kw) 20 mw Optimal Load (it depends on level of vibration) 3 15 kw Integrated WIreless SEnsing Maximal Output Power (load 3 kw; 0.5 G peak) 26 mw
VIBRATION POWER GENERATOR 17 Hz ABS Plastic frame Rapid Prototyping Generator with power management: Non-assembled generator with coil: Assembly of generator with power management and wireless sensor for aeronautic application
Output Voltage RMS [V] Output Power [mw] Praha 14. 4. 2011 VIBRATION POWER GENERATOR 17 Hz Excited vibration peak; frequency 17 Hz 30 0.1 G 0.2 G 0.3 G 0.4 G 0.5 G 25 20 15 10 5 0 18 0 5 10 15 20 Load R [kohm] Excited vibration peak; frequency 17 Hz 0.1 G 0.2 G 0.3 G 0.4 G 0.5 G 15 12 9 6 3 0 0 5 10 15 20 Load R [kohm]
Conclusion Potential of Energy Harvesting - Wireless Sensor Networks
Conclusions Energy harvesting has been successful in several engineering (aeronautic, automotive, military and civil engineering). Other consumer goods such as mobile phones and laptops will become significant; however, generated power of energy harvesting devices is very low for these consumer goods. Energy harvesting technologies are enabling the commercial progress of next-generation ultra-low-power electronic devices and systems. These devices are being deployed for wireless as well as wired systems such as mesh networks, sensor and control systems, MEMS, etc. The aim of this presentation was briefly reviewed energy harvesting technologies and their opportunity for future wireless and remote applications.
Harvesting children's energy for electricity