Mass Flow Distribution Measurement in Concentrated Solar Power Plants via Thermal Time-of-Flight Method

To maximize the thermal efficiency of Concentrating Solar Power (CSP) plants with a Parabolic Trough Collector (PTC) field, mass flow of the individual loops must be controlled carefully with the aim of achieving optimal loop outlet temperatures. An individual mass flow control has only been introduced in recent power plants, while a mass flow measurement with high temporal and spatial resolution has not yet been implemented. In this paper, the "Time-of-Flight" (ToF) method for the determination of the mass flow distribution through the individual loops of the solar field in a CSP plant is presented, based on measuring thermal step responses only with temperature sensors existing in typical power plant configurations. The ToF method is resented and validated with exemplary operational measurement data from the power plant Andasol III and determines the mass flow distribution through the solar field, measuring 94 % of the data within ±5 % of full scale. Knowledge and a good understanding of the mass flow distribution within the solar field enables the application of measures to increase the efficiency of power plant operation through improved loop balancing and improved early fault detection. For plants that already have high temporal and spatial resolution temperature measurements this ToF method enables the determination of the mass flow distribution without the installation of additional measuring equipment, and can thus be a powerful tool for the improvement of operation and predictive maintenance.