Energy harvesting (EH) is the capture of ambient
energy as an unlimited energy source for powering electronic devices.
Energy harvesting in sensor networks is deployed as part of an
overall Power Management System to create the most efficient use
of the total energy available to the network.
One challenge in deploying a sensor network
is providing consistent energy to remotely located wireless sensor
nodes; hence, the addition of EH as a power source can greatly
expand the potential applications, as well as greatly decrease
the costs associated with replacing conventional batteries.
Sources of Ambient Energy for Harvesting:
Mechanical: Vibration, mechanical stress
Thermal: Temperature gradients from friction,
Electromagnetic: RF, Inductors, coils
Natural Energy: Solar, wind, water and
Biomechanical Energy: Energy produced
by movement of a living organism
Chemical and Biological: Heat from biological
reactions, ion gradient
EH Components in Sensor
Energy Harvesting Module: This module
captures, stores and manages harvested energy. It includes a transduction
device, microprocessor, energy storage device, buffers and additional
circuitry for adjusting the harvested power such as a low voltage
booster. Examples of such modules include:
EH transduction devices
convert ambient energy into usable electrical signals. Specialized
materials are used to manufacture these devices, including photovoltaic
cells; piezoelectric, electromagnetic, thermoelectric and biochemical
materials; and micro-electro mechanical systems (MEMS) materials.
EH storage devices include
rechargeable batteries and capacitors.to store the harvested
energy so that a constant amount of current can be supplied
during times the ambient energy source is not present, like
solar energy at night.
Rechargable batteries: Thin Film
batteries are often used for their ultra-thin profile and
low leakage characteristics. Solid State rechargeable are
another good EH option.
Distributed or centralized: Depending
on the sensor network type (wired, wireless, combination)
EH devices can be centralized or distributed throughout the
entire system. Distributed EH modules are integrated with
each individual sensor node to create an energy harvesting
sensor. This type of EH tends to be employed with wireless
systems. Centralized EH modules are not integrated with each
node and tend to be deployed in wired and fiber-optic based
Power management software module to
manage and optimize the efficient use of the power. Specialized
power budgeting protocols and algorithms are used to maximize
power generated and minimize power use. Since the most energy
intensive function is transmitting data, our specialized algorithms
focus on precisely controlling the sleep/wake/transmit and receive
cycles of the sensor node transceiver, while Multi Sensor Data
Fusion (MSDF) algorithms minimize redundancy in the data to
reduce the data transmission size.