Influence of Measurement Equipment on the Uncertainty of Performance Data from Test Loops for Concentrating Solar Collectors

Abstract

Parabolic trough concentrating collectors play a major role in the energy efficiency and economics of concentrating solar power plants. Therefore, existing collector systems are constantly enhanced and new types were developed. Thermal performance testing is one step generally required in the course of their testing and qualification. For outdoor tests of prototypes, a heat transfer fluid loop (single collector or entire loop) needs to be equipped with measurement sensors for inlet, outlet, and ambient temperature as well as irradiance, wind speed, and mass or volumetric flow rate to evaluate the heat balance. Assessing the individual measurement uncertainties and their impact on the combined uncertainty of the desired measurement quantity one obtains the significance of the testing results. The method has been applied to a set of EuroTrough collector tests performed at Plataforma Solar de Almería, Spain. Test results include the uncertainty range of the resulting modeling function and exemplify the effects of sensors and their specifications on the parameters leading to an uncertainty of ±1.7% points for the optical collector efficiency. The measurement uncertainties of direct normal irradiance and mass flow rate are identified as determining uncertainty contributions and indicate room for improvement. Extended multiple sensor deployment and improved calibration procedures are the key to further reducing measurement uncertainty and hence increasing testing significance.

Characterization and Corrections for Clamp-On Fluid Temperature Measurements in Turbulent Flows

“…Nevertheless, there are various applications in which higher measurement accuracy rather than durability is needed. For example, during the commissioning or after major maintenance services of the solar field, a variety of performance tests have to be conducted, which require temporary, accurate temperature measurement at different locations [8]. Furthermore, these can serve to review the existing measurement system during normal operation.…”

Improved in situ performance testing of line-concentrating solar collectors: Comprehensive uncertainty analysis for the selection of measurement instrumentation

“…The aforementioned aspects are considered in the work performed by Janotte et al [21,22,5] and in the guideline for acceptance testing of parabolic troughs compiled by Kearney [23]. Within these publications, standard and combined uncertainties and details on the uncertainty calculation are reported.…”

On-site comparison of flowmeters installed in a parabolic-trough solar collector test facility

“…Depending on the performance of the flowmeters installed, uncertainties in the volumetric or mass flow rate may represent a larger or smaller contribution to the standard uncertainty of the solar collector's thermal efficiency [2].…”