Environmental Engineering Reference
In-Depth Information
5
Hybrid Ene rgy Harvesting System
Small-scale energy harvesting (EH) is a fast-growing research solution for
powering a wireless sensor node [122-125]. However, EH itself has an inher-
ent problem, which is the intermittent nature of the ambient energy source. It
is possible that the operational reliability of the sensor node becomes compro-
mised for prolonged unavailability of the ambient energy source. To augment
the reliability of the sensor node, hybrid energy harvesting (HEH) is proposed
in this chapter. For the HEH approach, a second ambient energy source, which
is available in the same environment as the first energy source, is harvested
to supplement the energy supply of the wireless sensor node. By doing so,
more energy can be potentially harvested, such that the wireless sensor node
is able to perform more power-intensive operations, such as increasing its
transmission rate or increased support for external sensors and peripherals.
The concept of HEH has been recently discussed in the literature [35, 126-
129] as a potential micropower supply solution to minimize the size of the
energy supply as well as to extend the operational lifetime of the wireless
sensor node. Researchers have considered a number of methods to combine
different small-scale EH sources, and these methods can be classified into four
main categories.
Type 1: HEH using two different EH mechanisms on the same platform.
Tadesse et al. [126] and Khaligh et al. [127] present a mechanical
combinatory EH device structure of two different EH mechanisms on
the same platform to harvest from the same vibration energy source.
Due to the drastic difference in matching the internal impedances
of the electromagnetic (
)EHmechanisms
with the external load resistance, it presents difficulty in combining
the output power from the two different mechanisms; hence, differ-
ent power converters are required to process the harvested power
separately.
) and piezoelectric (M
Type 2: HEH using an electronic switch/multiplexer to switch between EH
sources. Guilar et al. [128] and Lhermet et al. [129] proposed to com-
bine EH using an electronic switch/multiplexer to switch between
the two energy sources. Whenever both energy sources are present
simultaneously, based on the priority given by the power manage-
ment circuit, typically the higher-power source, only one of the two
137
Search WWH ::




Custom Search