View
214
Download
2
Category
Preview:
Citation preview
Comparison of Energy Harvesting Power Management Techniques and Application
Mohd Sofwan Mohd Resali ',Member IEEE, Hanim Salleh 2 , 2Department of Mechanical Engineering
Universiti Tenaga Nasional (UNITEN) Kajang, Malaysia
'Mohdsofwan@gmail.com, 2Hanim@uniten.edu.my
Abstract
There has been a significant increase in the research on energy harvesting device for low power applications in recreant years. This is due to smaller electronics power applications such as wireless and mobile electronics and the demand for better lifespan of batteries. One of the challenges of the harvesting energy from ambient is to convert, transfer and store the usable power effectively. In this context, there is a need to understand and design and efficient energy harvesting power management circuitry. In view of the issues, this paper compares several energy harvesting power management techniques and applications. Based on the comparison, suggestion on the design improvement are also included. This paper proposed improvement on the adaptive circuit as to get better efficiency. This paper will propose by using full bridge AC-DC rectifier to convert AC input voltage to usable DC voltage. In order to reduce power consumption of the circuit and power losses, comparator circuit is implementing as an adaptive approach to the DC-DC stepdown converter. Simulation results are presented that output voltage from power management energy harvesting circuit is 3.0V with output power is 30mW. The efficiency reported as 80%. The total power losses are 7.5mW. Lastly this design presents a stand-alone system, single supply voltage and compatibility for micro-scale circuit integration.
1. Introduction
In a few years before, with the increasingly many of electronic company devices start to produce micro-power electronic applications, people start to explore on the energy harvesting technologies as it can promise for the low power source. This technology will become as a big role for the alternative low power technology as it can reduce for the long life operation cycles, reduce cost of maintenance, keep clean of environment and researcher try to prove it can operate reliably as a good system for the environmental and industrial monitoring. This section will discuss about previous work for the power management energy harvesting circuit design. This section will cover on the design technique, key design factor and its application design for as to full fill a task as a good system from the ambient or waste energy sources. This comparison and review paper will be focus on the energy harvesting power management techniques and application for piezoelectric micro generator vibration based.
2. Power Management Energy Harvesting Circuit Concept
Design
In energy harvesting technologies, researcher or engineers start produce or introduce a few approach of the circuit design. The typical circuit consists of voltage rectifier, converter and storage. Below discuss about the components that are will be considered in the power management energy harvesting circuit. The choosing of the electronic device below should also consider the implementation of the low power electronics which is critical to reduce the total power losses.
2.1 AC-DC Rectifier
First of all in piezoelectric energy harvesting research concept, the piezoelectric will work as a harvester to collect a waste energy such as vibration rotational machine and then convert it to electrical energy [1-5]. The extract piezoelectric strain energy will produce an AC voltage as an electrical energy. But most of the low power electronic device nowadays will only use a low DC voltage. Therefore the AC output voltage need to rectify and convert it to the usable DC voltage to supply to the load circuit which is contents with electronic devices.
2.2 Energy Storage
In some electronic applications, the ambient energy or energy harvesting technique, the energy harvested can be considered to replace the usage of the batteries as an energy storage device. In the effort of it, device for the energy storage always promise for the advantages if compare to the batteries. Supercapacitor is one of the devices that can propose to replace of the usage of the batteries. By using supercapacitor it has advantages by more charge and discharge cycles. Other of the advantages are has high power density, high cycle efficiency, longer lifetime and lower toxicity of material used if compare to the usage of the batteries. There a few method of design energy storage circuit after the AC-DC rectifier. One of the method is by directly charge [6, refer IPEC ret] by connecting the supercapacitor parallel across the output AC-DC rectifier.
2.3 Comparator Circuit
In energy harvesting circuit design, the stability and enough targeted power is very important key points need to consider when apply it to the circuit design. The harvester or energy generator for example piezoelectric micro generator always harvest the energy from vibration rotational machine which will vibrating for a long time. The energy that was harvested will always flow to the targeted electronic load. But the challenging is when the input power or energy is lower
than targeted input power it will never to power up the load electronic circuit. That is why many component circuit design for energy harvesting circuit they will use the comparator
circuit. Torah et el [6] reported the comparison by using comparator or it was name as a cold start circuit between by
not using comparator circuit to power the microcontroller and RF sensor node. It was reported that by using the cold start
circuit it can power up the entire circuit and without cold start
circuit it never turn on the entire electronic devices.
2.4 DC-DC Step Up or Down Regulator
Most of the electronic device for low power application
needs for the low input voltage. The ranges of the low input
voltage usually range 3V until 5V. DC-DC step up or step down regulator are functioning first to supply a very stable supply voltage to the electronic load circuit which can
eliminate the voltage ripple from piezoelectric micro
generator. The second function is it also can step down the
high input voltage to the targeted low voltage as an example from 9V to 3V supply voltage and vice versa.
2.5 Load or Application Circuit
The last parts of the energy harvesting circuit that needs to consider is the application or load circuit. Basically researcher
or engineers will defmed first what is the targeted energy that
will be supplied to the application circuit and prepared the electronic device which can be utilize the energy that will be
supplied. Torah et al. [6] present also the power or budget energy consumption for the every single electronic application
device and by accumulates the energy consumption. By that it
can help engineers or researcher to provide the energy storage
that can store enough energy as requested.
3. Factors Affecting the Performance of the Power
Management Energy Harvesting Circuit
3.1 Circuit Efficiency
Many times of the research paper will report for the
optimum power energy extracted from a harvester such as from piezoelectric micro-power generator but many times one not reported for the circuit ineffectiveness. When comparing
techniques of power management energy harvesting circuit
solutions for a given application, the most important thing is to focus on the effectiveness of the circuit. The efficiency will
report on the actual energy effectively delivered to the application or also as a report of the energy harvested lost before delivered the energy to the targeted application. The
effectiveness of the circuit is calculated and measured by its efficiency converting power between input power (Pin) which
is the power generated from the micro-power generator and the output power (POIlI) which is the output power from storage in the power management circuit which will deliver the power
to the targeted application. It is also important to know what
the budget's power of the targeted application is and comparing with the actual power since the actual power will
be different from the optimwn power produce from the
harvester.
3.2 System Operations Independent
One of the applications by using energy harvesting circuit is the wireless sensor node (WSN) monitoring system. This
system is functioning to monitor as an example the vibration
rate for cooling fan's motor in the power plant by transmit vibration data to the control room. As to full fill this task
sometimes power management circuit requires for the external
sensor to trigger the energy harvesting circuit before can start to operate. This scenario shows this power management circuit
is not stand-alone. Stand-alone here means that this power
management energy harvesting circuit can operate independent of the other components of the electronic load.
One of the advantages by using the stand-alone operation
energy harvesting circuit is to save more energy or power.
3.3 Simple Management Circuit
Monitoring system by using energy harvesting circuit
always need for mUltiple electronic loads such as accelerometer sensor, microprocessor, RF module, switching
circuit and other more. Some electronic loads need for a more than one supply voltage for sensing current before can start operate. It makes the power management energy harvesting
circuit become more complex and need for a high power
application and reduces the efficiency due to non-scalable. A
good energy harvesting circuit which apply for a low power application is by applying only a single supply voltage and at
the same time makes the circuit more simple and increase the efficiency.
3.4 Small Size Circuit
These characteristics requests for the final integration of the power management energy harvesting circuit which will
improves the efficiency, energy density and reduce the cost. When applying adaptive circuit to the energy harvesting circuit avoid using the external sensor for sensing current. By
that this circuit can reduce for the circuit complexity, multi
supply voltage, and more simplicity and at the same time can
reduce for the cost.
3.5 Circuit Adatively
Adaptive approach is needed as to achieving the maximum
power flow from the rectified voltage. Since the amplitude of
the ambient energy such as the beam of vibration is not fixed, the power flow from the micro-power generator to the storage device is not optimum and is inefficient. By using an adaptive
circuit approach will maximize the power transferred from
vibrating piezoelectric transducer to the storage device.
4. Previous Energy Harvesting Circuit Design
In this section it will discussed on the previous works by previous researcher on the energy harvesting circuit design.
Some consideration that was takes by previous researcher or
engineers are depending by the specification that was earlier
set-up by them. This previous works are being review as to get look in depth understanding from previous works concept design and adapt to the new design.
The first findings research on the piezoelectric movement was reported by Kymissis et al. [7]. It proposed piezoelectric
generator the direct forced in a running shoe. Using direct discharge method by connecting capacitor to the AC-DC
rectifier is cannot extract maximum power. The output voltage
was regulated by a step-down switch mode power supply as to
get the stable DC output voltage and supply it to the targeted
load electronic circuit.
Dallago et al. [8] present for the AC-DC voltage doubler
retire to rectify the input power from micro-generator. It
implements exclusively a fraction of the harvested energy to
supply itself. The comparator of power conditioning circuit is
replaced with operational amplifier as to sense the voltage
across the switching MOSFET and drive their gate terminals.
The function of the OP-AMP was design so that they are able
to work with the minimum possible value of the supply
voltage. It was found that by implement independent supply
bias circuitry in order to make the current consumption of the
driving circuitry independent of the supply voltage the total
current consumption is 500nA. Meanwhile the efficiency is 90% in a wide range of load value. This design approach is
standalone system and compatible for a small size circuit.
Lesieutre et at. [9] proposed for the two mode of energy harvesting circuit. The first mode for low excitations, the
rectifiers charges the battery directly. The second mode, for
higher excitations the battery runs the DC-DC converter. At
the higher level of excitations the DC-DC converter delivers
more than four times the power to storage than direct charging from the rectifier, this ratio increase with excitations. The
hardware experimental results on a base on piezoelectric
cantilever had shown that having 26% coupling coefficient
and yielded an effective loss factor for the fundamental 2.2%
of vibration mode. This design approach presented the
standalone system but it has a big size of complete circuit since apply for the two mode of energy harvesting circuit.
Le et at. [10] proposed for the conversion circuit with
synchronous rectifier for voltage doubler, full bridge and
passive full bridge rectifier which are connected to the
piezoelectric micro power generator. Synchronous circuit here
means that the circuit is the digital control circuit in which the parts are synchronized by a clock sognal. It was reported that
for synchronous voltage doubler rectifier efficiency was
measured as 88% efficiency with output power exceeds
2.5f.lW at 100KQ, 100nF load. Meanwhile the synchronous
full bridge rectifier produced the efficiency 86% with peak power 22f.lW at 68KQ. For the passive full bridge rectifier it
was reported that the efficiency is achieve only 66% at 220KQ
and the peak output power was achieve 16f.lW at 68KQ load.
This paper reported that the best performance achieve at the
power conversion circuit based on the full wave synchronous
rectification architecture.
Yi et al. [11] proposed energy adaptive maximum power
point tracking (EA-MPPT) as to allow power management
circuit unit to activate at different operation modes according
to the available power level. AC-DC voltage doubler rectifier
circuit was used as a conversion circuit and then followed by
on chips charge pumps circuit with variable up or down conversion ratios for higher efficiency. It was reported that the AC-DC voltage double produce the open circuit voltage from
1.4 V to 5V and to make the efficiency comparable to a
switching converter the charge pump has to be highly
reconfigurable according to the input voltage. This deign method by using charge pump as power management circuit at
last not mention for the efficiency achievement but this is an
adaptive circuit implementation and standalone system with
small size circuit.
Hehn et al. [12] proposed for the two modes energy
harvesting circuit. The first mode at low excitations, the rectifiers charge the battery as a storage device directly. For
the second mode, at the higher excitations the battery will runs
the DC-DC converter. At the higher levels of excitations the
DC-DC converter delivers more than four times the power to
storage than direct charging from the rectifier, this ratio
increase with excitations. For this design method it use the full bridge AC-DC rectifier circuit with filter capacitor, a
switching DC-DC converter and battery as a storage device.
This paper presented operates as a standalone system which Observe that by fix duty cycle provides near-optimum
performance when persistent excitations exceed a certain
levels. The circuit design is not compatible for the small size
circuit.
Ottman et al. [I3*7nm] proposed the adaptive control
technique for the DC-DC converter. The objective of the design method to develop an approach that maximizes the
power transferred from vibrating piezoelectric transducer to the electrochemical battery. This paper initially presents the
simple model of a piezoelectric and added AC-DC rectifier
and then used to determine the point of optimal power flow for
the piezoelectric element. At lasts this paper present adaptive
approach to achieving the optimal power flow through the use
of a switch mode DC-DC converter. Experiment result show adaptive DC-DC converter increase power transfer by over
400% as compared to when the DC-DC converter is not used.
Nowadays the demands for the energy harvesting
application especially for the industrial wireless sensor system
monitoring network start to increase. Many company starts to
introduce their products and try to become a pioneer company who start explore this technology. Advance Linear Device
Inc. (ALD) produces the VEH300, VEH360 series power
management circuit that was ready to use. The portable power
management has a small size WxLxH (l4mm, 50.8mm, and
17.8mm) which the input generator is form piezoelectric.
Meanwhile Perpetuum Ltd produces the product PMG 17
which the generator is from electromagnetic. Their product is
including with the complete RF wireless sensor node and
commercialized with complete monitoring system especially
to the vibration machinery.
5. Design Proposal
0: 0: 0
U'!! � u �D DU- o: Enables D 'f- t!: 0 Uu
"'UJ ::;; D 0: 0 u
Figure I. Proposed power management energy harvesting circuit
Figure 1 show the proposed power management energy
harvesting circuit vibration based for wireless sensor nodes. The power management circuit apply for the full bridge AC
DC rectifier circuit as to convert from AC voltage to the DC
usable voltage. The supercapacitor then connected to the
rectifier as to store the energy flow from piezoelectric
transducer. The comparator is used as and adaptive circuit to
the DC-DC step-down converter. The output from the DC-DC
step-down converter then connected to the electronic load
circuit. This proposed power management energy harvesting
circuit was simulated and will be reported on the simulation results.
Energy Harvesting and Storage
Figure 2. Proposed block diagram for the energy harvesting circuit wireless sensor node
Microcontroller
RF Module
Figure 2 shows the block diagram for the propose design
energy harvesting circuit wireless sensor node. These propose
design is the early stage as to complete the proposed power
management energy harvesting in the figure 1. The
implementation of the microcontroller and RF module as the
load to the power management energy harvesting circuit vibration based were tested with hardware experimental test.
The result and discussion will be explained in the next chapter
of result and discussion.
6. Result and Discussion
Figure 3 show the simulation result for the propose power
management energy harvesting circuit in the figure 1.
12
10 -:::-- 8 III tI.O 6 �
- � �V(regulator)
... '0 4 :::-
2
0
,
,1 "'---
�V(Co rnparator)
_ V(Capac i tor)
o 27 54 81 108135
Time ( s )
Figure 3. Simulation results for the proposed power management energy harvesting circuit
Simulation results are presented that output voltage from
power management energy harvesting circuit is 3.0V with
output power is 30mW. The efficiency reported as 80%. The
total power losses are 7.SmW.
Figure 4. Piezoelectric generator to harvest energy from vibration.
Figure 5. Hardware experimental setup.
Figure 6. Storage capacitor charge and discharge.
Charge and Discharge
16
14
12
10 �
"0 8 >
__ Volt, 6
4 ........ Transmit
0
0 4 8 10 1 2
Seconds
Figure 7. Signal waveform of the system.
Figure 4 and S shows the hardware setup for the propose of block diagram energy harvesting circuit as mentioned in the
figure 2. Piezoelectric cantiliver was choose as the harvester which connected to the vibration shaker. The open circuit voltage was measure to the piezoelectric and the maximum voltage was measured is 16V AC.
Figure 6 and 7 shows the wavefonn for the experimental
test for the figure S. The supercapacitor will start charge until
maximum DC voltage supply at 14.SV DC and discharge until
SV DC voltage. When storage capacitor reached 9.SV threshold voltage the LED was blinking ON and OFF. The
cycle of ON and OFF is depending to the how long the storage
discharge and charge again. The power input after rectify the
AC voltage is 9mW. Mean while the power output that was measured is around 7mW.
The power losses before the energy flow reached the targeted electronic devices are 2mW. It means that the
efficiency of the system is 77.7%. The authors believe that the power losses can be decrease by using more low power
consumption for the DC-DC step-down converter. The
challenging for the author is also when it will start use the actual RF module load, which is almost require for the stable power supply.
The full bridge rectifier use MIC W06M device with the 47�F storage capacitor. The PIC 16F877A microcontroller are programmed to blink the light emitting diode (LED) once the
microcontroller are turn on. The LED function as an indicator
to demonstrate an autonomous blinking LED to represent
wireless condition monitoring system powered by energy harvested vibrational energy.
Acknoedgement
The authors would like to acknowledge the funding from TNB
(grant project number RJO 10090427) for the project an
energy harvesting power management module for wireless sensor network.
References
I. A. Tabesh, L. G. Frechette, "A low power stand-alone adaptive circuit for harvesting energy from a piezoelectric micro-power generator," IEEE
Trans. on Industrial Electronics, vol. 17, no. 3, March 20 I O.
2. C. 0'. Mathu'na, T. 0'. Donnell, R. V. Martinez-Catala, 1. Rohan, B. 0'
3.
4.
5.
Flynn, "Energy scavenging for long-term deployable wireless sensor
networks," ScienceDirect, vol. 75, issue 3, pp. 613-623, Remote
Sensing, May 200S.
D. 1. de Villiers, S. Kaplan, R. H. Wilkinson, "Energy harvesting for a
condition monitoring mote," IEEE 34th Annual Conference of IEEE,
Industrail Electronics, IECON 200S.
P. L. Chapman, "Power management for energy harvesting devices," IEEE Symps. on Radio and Wireless 2009, San Diego, CA, pp. 9-12, IS-
22 Jan. 2009,.
S. W. Arms, C. P. Townsend, D. L. Churchill, 1. H. Galbreath, S.W.
Mundell, "Power Management for energy harvesting wireless senssors," SPIE, Int. Symposium on Smart Structures and Smart Materials, San
Diego, March 2010.
6. R. Torah, P. Glynne-Jones, M. Tudor, T. 0', Donnel, S. Roy, "Self-powered autonomous wireless sensor node using vibration energy harvesting," Meas. Sci. Technol. 19, 200S.
7. Kymissis, J., Kendall, C., Paradiso, J. and Gershenfeld, N. 1998. "Parasitic Power Harvesting in Shoes," In: Second IEEE International
Conference on Wearable Computing (ISWC), IEEE Computer Society
Press, pp. 132-139.
8. E. Dallago, D. Miatton, G. Venchi, V. Bottarel, G. Frattini, G. Ricotti, M.
Schipani: "Active Autonomous AC-DC Converter for Piezoelectric
Energy Scavenging Systems", IEEE Custom Integrated Circuits Conference, CICC 2008, 21-24 September 2008, San Jose, California,
USA.
9. Lesieutre G, Ottman G and Hofmann H 2004, "Damping as a result of piezoelectric energy harvesting ," J. Sound Vih.269, pp. 991-1001.
10. Le, T. T., Han, 1., von Jouanne, A., "Piezoelectric micro-power generation
interface circuits,"IEEE Journal of Solid-State Circuits, 4/(6), 1411-1420.
11. Jun Yi, Feng Su, Yat-Hei Lam, Wing-Hung Ki, Chi-Ying Tsui, "An
energy adaptive MPPT power management unit for micro-power vibtration energy harvesting," IEEE Int. Symp. af Circuits and Systems,
200S,pp. 2570-2573.
12. T Hehn, F. Hagedorn, Y. Manoli., " A CMOS Integrated Interface for Piezoelectric Generators," Proc. Eurosensors XXIII conference, 2009,
Vol. 1, pp. 1451-1454.
13. G. K. Ottman" Heath F. Hofmann, Archin C. Bhatt, George A.
Lesieutre., "Adaptive piezoelectric energy harvesting circuit for wireless
remote power supply", IEEE Trans. on Power Electronics, vol.l7, pp. 669--676,2002.
Recommended