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An experimental tube receiver was constructed, built and brought to operation. This receiver served as a model to try out the so-called scan-method and the measurement of the flux density by reflection off the receiver in real time during irradiation. A comparison with a flux map obtained by a radiometer-based method shows qualitatively similar results. It is concluded that the camera-method is applicable to tube receivers. Experiments at large-scale industrial receivers are planned. [ABSTRACT FROM AUTHOR]

The conventional method of initial heliostat calibration by sequentially pointing the heliostats one by one onto a target is a very slow process. The use of unmanned airborne vehicles (UAVs) is a possible approach to developing a less time consuming procedure for the initial setup of the field control system and elimination of offset in light beam pointing. This paper presents a UAV based method for measuring the heliostat offset in two stages. The first stage, preliminary and less accurate, creates a three-dimensional model of the mirror facet corners in order to estimate the heliostat orientation. The estimated orientation from the first stage is a prerequisite for the second stage of measurement, in which the highly accurate heliostat orientation is derived from deflectometrically measuring the mirror shape. While work is still ongoing to fully implement the final steps of the second stage, the measuring principles has been demonstrated and partially validated for the first stage. [ABSTRACT FROM AUTHOR]

Power tower or central receiver systems use hundreds to ten thousands of two-axis tracking mirrors, so called heliostats, which reflect and focus the sunlight onto a receiver on top of a tower during the day. As basis for a well performing heliostat field, a single heliostat has to perform "correctly". In order to describe and measure the performance of a single heliostat, the SolarPACES Guideline for Heliostat Performance Testing has been developed by a group of R&D and industry experts during the last years. However, at the end, the performance of the whole field, which means the superposition and interaction of all heliostats determines the energy collected in the aperture of a solar central receiver. For that reason, a second guideline is currently outlined, the SolarPACES Guideline for Heliostat Field Performance Testing. Both guidelines aim to be commonly agreed protocols between R&D centers and industry in the field of heliostat performance testing. Recently, a third guideline activity has been started to improve and unify heliostat wind load design methods. The once finalized guidelines (or their concepts) should be included in international standards (e.g. IEC) and used by national organizations like DKE, AENOR, ASME, ASTM. This paper gives an update of the state of the three guidelines being developed in the SolarPACES task III-heliostat working group. [ABSTRACT FROM AUTHOR]

This paper reports heat flux measurements on parabolic trough receivers, which are integrated to calculate the receiver overall heat loss. Integrated heat fluxes yield an overall heat loss value which agrees with DLR ThermoRec heat loss measurements within ± 5 %, in the simplified case of assuming a homogeneous heat flux distribution around the receiver circumference. Heat flux measurements also allow separating glass envelope and shielded bellow heat loss terms for receiver thermal modelling. Shielded bellows only represent 3 to 4 % of the receiver total length at ambient temperature, however heat flux measurements show that their contribution to the overall receiver heat loss ranges from 5 to 15 %, depending on the shield construction and the absorber temperature. The receiver specific heat loss thus tends to lie above the glass envelope specific heat loss. Almost homogeneous heat flux values are measured along the glass envelope length (variation below 5 %), while more inhomogeneous heat flux values are observed over circumference of the glass envelope (variation between top and side of 17 %). The measurement setup analysis shows a good repeatability, although a proper mounting of heat flux sensors is important in order to avoid systematic biases. [ABSTRACT FROM AUTHOR]