Abstract
Thermal management of SOFCs (solid oxide fuel cell) is important for helping to minimise high temperature-related performance losses and maximising cell/stack lifetime. Thin film sensor technology is proposed as an excellent candidate to measure the cell temperature during operation due to its negligible mass, minimal disturbance to normal operation and higher temporal and spatial resolutions. However, the effective application of such sensors in SOFC systems is a challenging endeavour and predicated on incorporating the external wire attachments to complete the electrical circuit. This is because of the high sensitivity of SOFC materials to any interference to operation, limited available space and harsh operating conditions. In this paper, a new concept of packaging external wire attachments to the thin film sensor is described to enable the integration of the sensor in the SOFC system. Temperature measurements have been monitored under OCV and operating condition with the thin film sensor directly from SOFC cathode surface via proposed spring-based wire connection, from room temperature to SOFC operating temperature. The impact of the parameters including contact resistance (Rc) between sensor pads and attached wire on monitored temperature has also been analysed with the contribution of conductive paste. High temporal and spatial resolutions have been obtained with the implemented sensor.
Highlights
Due to harsh operating environments of a working cell, it is difficult to measure the temperature of operating SOFCs experimentally[11,12]
There is 14 °C temperature difference observed between the furnace (TC) and sensing points (SSPs)-ave whilst the average cell temperature was at about 250 °C during heating segment (H-TC, and H-SSPs ave)
Currently applied method for external wire attachment to a thin film sensor. For those sensors including resistance temperature detectors (RTD), thermistors, resistance strain gauges (RSG), and TCs used in the thin film form, external wire connection plays a key role as a step in the determinant pathway for accurate and constant signal collection[21]
Summary
Due to harsh operating environments of a working cell, it is difficult to measure the temperature of operating SOFCs experimentally[11,12]. The measurements from TCs in SOFCs is generally obtained from gas flow channels with an allowed adjacency to the cell surface[17]. A thin film- based sensor architecture is realised as a potential application for SOFC temperature sensing due to their advantageous features that include minimal intrusion to the normal working of the cell and comprising of mechanically self-supporting components not requiring too much machining[23]. It is capable of higher temporal and spatial resolutions. The wider intent is to extend/replicate the design provisions for these external connections at a stack level to allow sensory techniques to be more applicable for SOFCs that eventually can help to (i) understand the degradation issues of SOFC systems deeply and (ii) provide an integrated platform for SOFC lifecycle monitoring and diagnostics that more accurately includes temperature monitoring, at both a cell- and stack-wide level
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