System and method for thermo-mechanical monitoring of a solar receiver

A concentrated solar power (CSP) plant, comprising:

• a plurality of heliostats or a heliostat field;
• a substantially cylindrical solar energy receiver located atop a central tower and having an external surface covered with receiver panels and a heat shield adjacent the solar receiver, the heliostats being configured to reflect solar energy to the external surface of the receiver, each receiver panel comprising a plurality of heat exchanger tubes configured to transport a heat transfer fluid, which are partly exposed on the external surface of the receiver;
• a thermo-mechanical monitoring system configured to ensure integrity of the solar receiver panel tubes in operation, the thermomechanical monitoring system comprising at least:
• a plurality of thermal imaging devices located on ground and mounted each on a securing and orienting device, configured to measure infrared radiation emitted by the external surface of the receiver and to provide a panel temperature-dependent signal in an area of the external surface;
• for each thermal imaging device, a reference area of interest RAOI located on the heat shield arranged opposite its thermal imaging device and containing one or more temperature sensors configured to measure a reference temperature corresponding to the RAOI,
• one or more flowmeters configured to measure a flow rate of heat-transfer fluid in the heat exchanger tubes and temperature sensors arranged respectively at inlets and outlets of the exchanger tubes, the measurements provided by the flowmeters and the temperature sensors being intended for calculating an energy balance absorbed by the heat transfer fluid in the receiver as well as mechanical strains experienced by the exchanger tubes;
• and
• a data processing system configured to calculate and/or supply respectively a maximum temperature, a temperature profile, and/or an absorbed power profile in each heat exchanger tube and theoretical mechanical strains assigned to each heat exchanger tube as a function of a temperature provided by the imaging devices, taking into account a reference temperature of the RAOI and a temperature of the heat transfer fluid at the inlets and the outlets of the tubes, in order to control if an operating point of an area located on the solar receiver is within an operating envelope in a 2D-space theoretical strain/Tmax defining predefined temperature and strain thresholds and in order to emit alerts upon exceeding predefined temperature and strain thresholds, while being outside the envelope and further to require heliostat radiation defocusing on the area, the data processing system comprising first control means configured to control IR cameras, second control means configured to control panel tube integrity in operation, and a distributed control system DCS connected to the first and second control means, to flowmeters, tube temperature sensors, and RAOI reference temperature sensors, the DCS being configured to communicate the measured reference temperature of the RAOI to the first control means, the measured flow rate and inlet/outlet temperatures of the heat transfer fluid to the first control means and/or second control means, and the DCS being configured to receive from the second control means local panel defocusing information for defocusing heliostat radiation on one or more panels;
• wherein the second control means configured to control panel tube integrity in operation comprise means configured to communicate with the first means and for:
• calculating a corrected maximum temperature on each exchanger tube by introducing a mathematical correction based on temperatures measured by the IR camera, inlet and outlet panel molten salt temperatures, and molten salt flow in the considered panel;
• with a dedicated mathematical creep-fatigue model, calculating theoretical strain level in the tubes;
• comparing a positioning of points defined by the calculated corrected maximum temperature and the calculated strain level within allowed solar receiver operating envelope;
• and
• generating an alarm and, according to the actual error level, requesting heliostat defocusing and/or shutdown, when a positioning of the calculated corrected maximum temperature and/or the calculated strain level is outside the operating envelope.