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DOE OSTI2025

Passive Wireless Sensors for Realtime Temperature and Corrosion Monitoring of Coal Boiler Components Under Flexible Operation (Final Technical Report)

Researchers at West Virginia University (WVU) propose to demonstrate inexpensive wireless, high-temperature sensors for real-time monitoring of the temperature and corrosion of metal components, which are commonly used in coal-fired boilers. This study presents the development of cost-effective wireless high-temperature sensors for real-time temperature and corrosion monitoring in coal-fired boilers' metal components. The focus is on fabricating and evaluating chipless radio-frequency identification (RFID) sensors capable of operating between 25-1300 ºC. Efforts were directed towards designing passive RFID sensor and interrogator antenna with a broad frequency range, optimizing a microstrip patch antenna sensor integrated into a "peel-and-stick" format for efficient application to various metal specimens without altering their geometry. Additionally, this research aimed to assess the sensor responses under accelerated high-temperature conditions, correlating corrosion and cracking mechanisms with sensor data. An investigation of through-wall data acquisition techniques was also planned, facilitating unobtrusive monitoring of sensor responses housed within metal enclosures. Ultimately, this work sought to establish a robust passive wireless sensor system for the continuous health monitoring of metal components in operational settings, thereby contributing to enhanced safety and efficiency in coal-fired power plants.

20 FOSSIL-FUELED POWER PLANTS↗

DOE OSTI2019

Microstrip patch antenna for simultaneous temperature sensing and superstrate characterization

This paper investigates a microstrip patch antenna for measuring the thickness and dielectric constant of the medium above the antenna (i.e. the superstrate) as well as the temperature. The intended application is simultaneous sensing of ash accumulation and temperature inside a boiler, with the aim of enhancing safety, improving efficiency, and reducing downtime associated with maintenance. A patch antenna, consisting of a dielectric substrate, a radiation patch, and a ground plane, functions as an electromagnetic resonator with specific fundamental frequencies. A dielectric medium placed above the patch antenna changes its effective dielectric constant and thus its resonant frequencies. Meanwhile, temperature also influences the antenna frequencies because of the thermal expansion of the conductors (i.e. the radiation patch and ground plane), and the dielectric constant of dielectric materials due to their temperature dependency. Since a rectangular patch antenna has two fundamental frequencies, it enables determining these two parameters simultaneously. Once the temperature and superstrate thickness are determined, the dielectric constant of the superstrate and its temperature dependency can also be extracted. To demonstrate this capability, a dual-frequency patch antenna was designed, fabricated, and characterized with a superstrate of various thicknesses and at different temperatures. By fitting the antenna resonant frequencies as functions of the superstrate thickness and temperature, these two parameters were inversely determined from the measured antenna frequencies. Using ash from charcoal briquettes as a superstrate, the measurement uncertainties were determined to be ±0.58 °C and ±58.05 μ m for the temperature and the superstrate thickness respectively. The dielectric constant of the ash was found to be 2.64 at room temperature and its thermal coefficient of dielectric constant (TCD k ) was found to be 918 ppm °C –1 .

36 MATERIALS SCIENCE↗

DOE OSTI2016

Wireless Interrogation of a High Temperature Antenna Sensor Without Electronics

This paper presents a novel interrogation mechanism for an antenna sensor subjected to high temperatures. In sensor node, an Ultra-wide Band (UWB) microstrip antenna was used as a wireless Tx/Rx transceiver to amplify the reflected interrogation signal from the temperature-sensing element, i.e. the patch antenna-sensor. A microstrip delay line was used to connect the Tx/Rx antenna and the antenna-sensor so that the reflected signal from the sensor node is delayed and can be separated from the background clutter using time-domain (T-D) gating technique. In this paper, the principle of operation of the proposed interrogation mechanism is first discussed, followed by the design and simulations of the sensor node circuitry. Finally, a temperature test was conducted to validate the wireless temperature sensing performance of the antenna sensor.

Tchafa, Franck Mbanya↗

DOE OSTI2016

Far-Field Interrogation of Microstrip Patch Antenna for Temperature Sensing Without Electronics

Temperature sensing without electronics is demonstrated through wireless interrogation of passive antenna-sensors. The sensor node is equipped with an ultra-wide-band microstrip antenna as the transmitting/receiving (Tx/Rx) antenna and a microstrip patch antenna serving as the temperature-sensing element. A microstrip transmission line connecting the Tx/Rx antenna and the antenna-sensor delays the signal reflected from the sensing element and thus separated it from the background clutter. The operation principle of the wireless sensing scheme is first discussed, followed by the design and simulations of the sensor node circuitry. Furthermore, a digital signal processing algorithm that extracts the antenna resonant frequency from the wirelessly received signal is also described. Temperature tests were conducted to validate the performance of the wireless antenna sensor inside an oven.

42 ENGINEERING↗

DOE OSTI2018

A Compact Hybrid-Fed Microstrip Antenna for Harmonics- Based Radar and Sensor Systems

In this letter, we propose and experimentally validate a compact hybrid-fed microstrip antenna for the harmonics-based radar and sensor systems, which receive the fundamental tone and retransmit the modulated second harmonic. The proposed microstrip antenna is based on a simple single-layered and dual-feed structure, consisting of an inner circular patch operating in the TM110 mode (second harmonic; 6 GHz) and an outer split-ring patch operating in the higher order TM210 or TM310 mode (fundamental frequency; 3 GHz). By varying the feed position and the geometry of the split-ring patch, a specific higher order mode can be excited at the fundamental frequency. Moreover, analytical expressions were derived for calculating the antenna's resonant frequencies. Our measurement results show that the maximum realized gain is 1.17 dB at 3 GHz and is 3.33 dB at 6 GHz, with good impedance matching (vertical bar S-11 vertical bar < -15 dB) and high isolation (< -20 dB).

harmonic radar↗

DOE OSTI2018

Microstrip patch antenna for simultaneous strain and temperature sensing

A patch antenna, consisting of a radiation patch, a dielectric substrate, and a ground plane, resonates at distinct fundamental frequencies that depend on the substrate dielectric constant and the dimensions of the radiation patch. Since these parameters change with the applied strain and temperature, this study investigates simultaneous strain and temperature sensing using a single antenna that has two fundamental resonant frequencies. The theoretical relationship between the antenna resonant frequency shifts, the temperature, and the applied strain was first established to guide the selection of the dielectric substrate, based on which an antenna sensor with a rectangular radiation patch was designed and fabricated. A tensile test specimen instrumented with the antenna sensor was subjected to thermo-mechanical tests. Experiment results validated the theoretical predictions that the normalized antenna resonant frequency shifts are linearly proportional to the applied strain and temperature changes. As a result, an inverse method was developed to determine the strain and temperature changes from the normalized antenna resonant frequency shifts, yielding measurement uncertainty of 0.4 °C and 17.22 μϵ for temperature and strain measurement, respectively.

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2017

Simultaneous Strain and Temperature Sensing using a Microstrip Patch Antenna

In this paper, we present simultaneous strain and temperature sensing using a single microstrip patch antenna fabricated on commercial printed circuit board (PCB). Temperature and strain are extracted from the resonant frequencies of the patch antenna as these frequencies are dependent on the dielectric constant of the PCB and the patch dimensions, which are subject to change with applied strain and temperature variations. The principle of operation of the patch antenna is first discussed, followed by the design and fabrication of the instrumented test specimen. Finally, thermal and mechanical tests were conducted to validate the strain and temperature sensing performance of the antenna sensor

TCHAFA, FRANCK MBANYA↗