Transcript Overview of Energy Harvesting

Introduction to Energy
Harvesting
EE174 – SJSU
Tan Nguyen
OUTLINE
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Introduction to Energy Harvesting (EH)
How does EH work?
Sources of Energy
Energy conversions
EH Components
EH system and EH Circuit
Energy storage is a Must
Application
Future Research Issues
Introduction Energy Harvesting (EH)
• Energy Harvesting (EH); also known as power harvesting or energy scavenging, is the process in which
energy is captured from an ambient energy and converted into usable electric power.
• Energy harvesters provide a very small amount of power for low-energy electronics.
• EH allows electronics to operate where there's no conventional power source, eliminating the need
for wires or replacement of batteries.
• EH systems generally includes circuitry to charge an energy storage cell, and manage the power,
providing regulation and protection.
• EH-powered systems need reliable energy generation, storage and delivery:
• Must have energy storage as EH transducer energy source is not always available (solar at night,
motor vibration at rest, air-flow, etc.)
• EH can provide “endless energy” for the electronics lifespan.
• Ideal for substituting for batteries that are impractical, costly, or dangerous to replace.
Ultra Low Power uController
Portable Electric Energy Sources Available
Batteries
– Wide spread availability, high
reliability
– Low-cost, mature
technologies
– Replacement/recharging is an
issue
• Too numerous in the future
• Location is unreachable
– Sensor size limited by battery
size
- Relative Improvement in
Laptop Technology
􀂃
Battery energy is the slowest trend
How Energy Harvesting works?
An energy harvester comprises one or more transducers, power conditioning,
and energy storage. These technologies work together to collect energy and
deliver power to the device. On the other hand, the device which uses the
energy needs to be designed to work with energy harvesting as the power
source.
(Sources of Energy)
(Devices)
How Energy Harvesting works?
• The transducer: converts energy from one energy type to a another energy
type, usually electricity.
• Power conditioning: is necessary because the natural output of the
transducer can be intermittent, and at the wrong frequency, voltage and
current to directly drive the device. A specialised DC-DC converter
microchip takes in power from the transducer and convert to voltages which
can then be stored or used.
• Energy storage: is needed to balance the energy supply and energy
demand. For applications where energy is used as soon it is collected (e.g.
RFID and wireless light switches), no storage is needed. Usually however a
rechargeable battery, capacitor, or supercapacitor is used. Batteries degrade
over time, and so the lifetime of the storage device can often be the limiting
factor in the overall lifetime of the harvester.
Sources of Energy
Energy harvesting uses unconventional
sources to power circuitry.
• Light (captured by
photovoltaic cells)
• Vibration or pressure
(captured by a piezoelectric
element)
• Temperature differentials
(captured by a thermo-electric
generator)
• Radio Frequency (captured by
an antenna)
• Biochemically produced
energy (such as cells that
extract energy from blood
sugar).
General Overview of Ambient Energy Sources
• Human Body: Mechanical and thermal (heat variations) energy can be
generated from a human or animal body by actions such as walking and running;
• Natural Energy: Wind, water flow, ocean waves, and solar energy can provide
limitless energy availability from the environment;
• Mechanical Energy: Vibrations from machines, mechanical stress, strain from
high-pressure motors, manufacturing machines, and waste rotations can be
captured and used as ambient mechanical energy sources;
• Thermal Energy: Waste heat energy variations from furnaces, heaters, and
friction sources.
• Light Energy: This source can be divided into two categories of energy: indoor
room light and outdoor sunlight energy. Light energy can be captured via photo
sensors, photo diodes, and solar photovoltaic (PV) panels; and
• Electromagnetic Energy: Inductors, coils, and transformers can be considered
as ambient energy sources, depending on how much energy is needed for the
application.
Additionally, chemical and biological sources and radiation can be considered
ambient energy sources
Block Diagram of General Ambient EH systems.
• The first row shows the energy-harvesting sources.
• The second row shows actual implementation and tools are
employed to harvest the energy from the source are
illustrated.
• The third row shows the energy-harvesting techniques
from each source.
Energy Harvesting Block Diagram
Energy Harvesting (EH)
• EH uses of ambient energy to provide electrical power for small electronic and electrical devices.
• An Energy Harvesting System consists of an Energy Harvester Module and a processor/transmitter
block.
• Energy Harvesting Module captures milli-watts of energy from light, vibration, thermal or
biological sources. A possible source of energy also comes from RF such as emitted from cell
phone towers.
• The power is then conditioned and stored within a battery, an efficient quick charging capacitor
or one of the newly developed thin film batteries.
• The system is then triggered at the required intervals to take a sensor reading, through a low
power system. This data is then processed and transmitted to the base station.
• This kind of EH System eliminates the dependency of the system on battery power and reduces
the need to service the system..
Portable Electric Energy Sources Available
• Solar Cells
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Commercial-off-the-shelf (COTS) energy harvesting
1cm x 1cm; 0.14 mW (much less inside)
• Recent research trend to improve the efficiency, robustness, costdown, etc.
• Often limited by the availability of direct sunlight and size.
Biochemical Energy Production
• Catabolism: metabolic
reactions in which large
molecules are broken
down into smaller
molecules – Usually
produce energy (but not
always)
• Anabolism: metabolic
reactions in which
smaller molecules are
joined to form larger
molecules – Usually
consume energy
Metabolism
Energy Storage is a Must
• Almost all energy-harvesting scenarios require some sort of energy
storage element or buffer. Even if the voltage and current requirements
of an embedded application were so low as to be run directly on power
captured or scavenged from the environment, such power would not
flow in a constant way.
• Storage elements or buffers are implemented in the form of a capacitor,
standard rechargeable lithium battery, or a new technology like thin-film
batteries. What kind of energy storage is needed depends greatly on the
application.
• Some applications require power for only a very short period of time, as
short as the RC time constant discharge rate of a capacitor. Other
applications require relatively large amounts of power for an extended
duration, which dictates the use of a traditional AA or a rechargeable
lithium battery
Li-Ion Battery
Thin Film
Battery
Recharge cycles
Hundreds
Thousands
Millions
Self-discharge
Moderate
Negligible
High
Charge Time
Hours
Minutes
Sec-minutes
Physical Size
Large
Small
Medium
Capacity
0.3-2500 mAHr 12-1000 μAHr
10-100 μAHr
Environmental
Impact
High
Minimal
Minimal
Super Cap
Industry Applications
• Remote patient monitoring
• Efficient office energy control
• Surveillance and security
• Agricultural management
• Home automation
• Long range asset tracking
• Implantable sensors
• Structural monitoring
• Machinery/equipment monitoring
Design Consideration
• TI's TMS37157 could also be used to harness the RF energy
into electrical energy. TI's MSP430 and Low Power RF parts
combined with efficient DC/DC Converters and Battery
Management parts are an ideal complement to these low
power energy harvesting sources.
• With as low as 160 uA/MHz (microamp per megahertz) active
power consumption and 1.5 uA standby power
consumption, MSP430F5xx MCUs enable longer battery life or
no batteries at all for energy harvesting systems that run off of
solar power, vibration energy or temperature differences like
found on human body.
References:
http://www.maximintegrated.com/en/app-notes/index.mvp/id/5259
http://www.ti.com/lsds/ti/apps/alternative_energy/harvesting/overview.page
http://institute.lanl.gov/ei/_docs/Annual_Workshops/Overview_of_energy_h
arvesting_systemsLA-UR_8296.pdf
http://chipdesignmag.com/lpd/blog/2009/07/17/energy-scavenging-and-storagemust-work-together/
http://scholar.lib.vt.edu/ejournals/JOTS/v35/v35n1/yildiz.html
http://www.msm.cam.ac.uk/teaching/partIII/courseM19/M19H.pdf
file:///C:/Users/test1/Downloads/Energy%20harvesting%20(1).pdf
http://health.uml.edu/horta/23Energy.pdf