Facilites

Testbed for optical alignment of heliostat mirror facets: detection of canting, focusing, and slope errors. It consists of two structures that respectively hold the mirror facet and a 1×1 m2 reference target. The last one is equipped with a high-resolution 42 Mpx camera and a laser. Facet alignment is adjusted with micrometer screws. Along with the testbed, mirrors are curved to specific focal lengths in the workbench. 

The lab-scale Linear Beam-Down solar field is composed of 3 different stages: the first one is the primary mirror field located near the ground, the second one is the secondary reflector placed above the first stage, and the last stage is the solar receiver, where the solar irradiance is concentrated.

Flat mirrors are used in the primary field to save in prototype costs, specifically 40 flat mirrors 5.5 cm wide are used, divided in 4 different sets of 10 mirrors each to allow easier transport. Each mirror must be in a specific fixed position and with a defined angle that varies throughout the day to track the sun. The secondary reflector is composed of 18 flat mirrors 5 cm wide and fixed in the required position with the necessary inclination. These mirrors are located 1.31 meters above the primary field. Solar heat fluxes of 7-11 kW/m2 are expected on the solar receiver, which will be placed on the ground.

It is a liquid water loop of approximately 4 m length used to test the tubes of external solar receiver for solar tower power plants. The heat flux in the tube is obtained with an inductor system that heat unilaterally the tube with heat flow rates of 0.5-1 MW/m2. The facility is equipped to measure temperatures, stresses and deformations in the receiver tube. It is used to preliminarily validate the use of different geometries and composition of the tube and allows carry out tests with different structural boundary conditions and supports.

Experimental facility of the tubes of external solar receiver of solar tower power plants equipped to measure temperature and thermal stresses in the tubes.

It is a molten salt loop (KNO3+NaNO3) of approximately 12 m length used to obtain experimental measurements of the tubes in solar tower receivers, under real operating conditions. The facility is able to operate at different temperatures (from 300 ºC to 600 ºC) and variable flow rate; the geometry and material of the tube can be changed and the measurements can be carried out under steady or transient conditions. An inductor system is used to heat unilaterally the tube with heat flow rates of 0.5-1 MW/m2, similar to the conditions in real plants.

A Compound Parabolic Concentrator (CPC) is available in our laboratory. It redirects the incident solar rays from the lateral parabolas to the central flat area, where the solar receiver is located. The receiver dimensions are 150 mm wide and 1000 mm long. 

The expected solar concentration is about 4.6 suns. Measurements taken in May at University Carlos III of Madrid have shown a heat flux of about 3.6 kW/m2, achieving a solar concentration of about 4.