Energy Harvesting and Energy Storage for Wireless and Less-Wired Sensors in Harsh Environments
Engineering requires sensors to control and understand the environment. This is particularly
important in harsh environments. The drawbacks, especially in gas turbines is the complexity
of installing a wired sensor and the weight of the wires. This makes wireless sensors attractive.
A wireless sensor requires a power source for transmission of data. Batteries have previously
taken the role of power source for most wireless sensors, but is unfortunately not suitable for
all applications. Lately, with energy harvesting and supercapacitors in the picture, sensor ap-
plications in high temperature environments, with high power requirements or with long life
requirements have the possibility of wireless interface.
A supercapacitor can handle higher temperatures, higher power output and can have a cycle life
that exceeds batteries by a factor of 10000. The lower energy density and high self-discharge
makes it unsuitable to power a wireless sensor without power source. However, connected to
an energy harvester converting waste energy into electricity makes this a powerful combination.
Energy harvesters thrives in environments where waste energy is plentiful and low conversion
efficiencies can be enough to power both the sensor and the transmitter. A thermoelectric har-
vester is designed and fabricated for the middle to rear part of a gas turbine. The temperature
in this region can reach 1600 ◦ C and require extensive cooling. In the cooling channels the wall
temperature reach 800-950 ◦ C when the cooling air is 450-600 ◦ C. In this location a thermoelec-
tric harvester will have access to high thermal gradients and active cooling.
To harvest the vibrations a piezoelectric energy harvester was built. To harvest enough energy
the resonance frequency of the energy harvester is frequency-matched with the high energy
vibrations. In many applications these frequencies drift and thus require a broad bandwidth
harvester. Simulation and assembly of a broadband coupled piezoelectric energy harvester is
presented in the thesis.
A piezoelectric harvester require electronics and energy storage to gather enough energy to
power up and run a wireless sensor. The thesis covers the fabrication of a high temperature su-
percapacitor capable of temperatures up to 181 ◦ C.