Simon Caron

A Transient Thermography Method to Separate Heat Loss Mechanisms in Parabolic Trough Receivers

This paper describes a transient thermography method to measure the heat loss of parabolic trough receivers and separate their heat loss mechanisms. This method is complementary to existing stationary techniques, which use either energy balances or glass envelope temperature measurements to derive overall heat losses. It is shown that the receiver heat loss can be calculated by applying a thermal excitation on the absorber tube and measuring both absorber tube and glass envelope temperature signals. Additionally, the emittance of the absorber selective coating and the vacuum quality of the annulus can be derived. The benefits and the limits of the transient method are presented and compared to the established stationary method based on glass envelope temperature measurements. Simulation studies and first validation experiments are described. A simulation based uncertainty analysis indicates that an uncertainty level of approximately 5% could be achieved on heat loss measurements for the transient method introduced in this paper, whereas for a conventional stationary field measurement technique, the uncertainty is estimated to 17–19%.

Techno-Economic Analysis of Receiver Replacement Scenarios in a Parabolic Trough Field

The heat loss of an evacuated parabolic trough receiver of solar thermal power plants ranges typically between values below 150 and 200 W/m at 350°C. Defects, such as glass breakage by wind events and coating degradation, anti-reflection coating degradation or hydrogen accumulation in the annulus, decrease the annual electricity production. This study examines the effect of different receiver performance loss scenarios on the energetic and economic output of a modern 150-MWel–parabolic trough plant with 7.5-hours molten-salt storage, located in Ma’an, Jordan over the whole lifetime by modeling it in an extended version of the software greenius. Compared to the reference scenario, a wind event in year 5 (10, 15) causing glass envelope breakage and consequential degradation of the selective coating of 5.6% of the receivers reduces the electricity output by 5.1% (3.8%, 2.5%), the net present value is reduced by 36.5% (23.1%, 13.1%). The payback time of receiver replacement is only 0.7 years and hence this measure is recommended. The highest negative impact on performance and net present value of a project has the hydrogen accumulation scenario (50% of field affected) in event year 5 (10,15) reducing net electric output by 10.7% (8.1%, 5.4%) and the net present value by 77.0% (48.7%, 27.6%). Replacement of the receivers or even better an inexpensive repair solution is an energetically and economically sensible solution. The option of investing in premium receivers with Xe-capsule during the construction phase is a viable option if the surplus cost for premium receivers is lower than 10 to 20 percent.