||HEMS11 Archimede Solar Energy receiver tubes are produced under license from ENEA (Italian National Research Agency for Renewable Energy) and they are designed for thermodynamic solar power plants, operating at high temperature (up to 580°C), with molten salts as Heat Transfer Fluid (HTF).
Thanks to a unique spectrally selective coating stable up to 600 °C and a casing kept in a vacuum, Archimede tubes ensure the maximum sunlight yield and thus they are the most technologically advanced solar receivers, available for high temperature range. Moreover, it is possible to accumulate the solar energy in special storage tanks so that electric power can be produced on the basis of the actual needs of the users, even in absence of solar radiation.
The surface coating deposited on the tube is constituted of a thin film multilayer structure with an inferior layer of metal, reflecting in the infrared and a superior one of antireflective ceramic material.
A graded ceramic-metallic material (CERMET), having different volumetric fraction of metal, is interposed between the two films. Thanks to this spectrally selective coating, the receiver tubes have an absorbance equal or higher than 95% and a design emissivity lower than 10% at 400°C and than 14% at 580°C.
The external glass has an antireflective coating on both surfaces with a solar transmittance equal or higher than 96.5%.
The metal bellows, adjust the difference in thermal expansion between the hot absorber tube and the cooler external glass envelope during operating conditions.
In order to achieve outstanding vacuum tight enclosure, each bellow is welded on one side to the absorber tube and to the glass on the other side by glass-to-metal junction.
Innovative glass-to-metal junctions are made by a special machined and vacuum heat treated stainless steel rings.
The internal shields have been dimensioned to optimize the thermal characteristics and reliability of the tube with an irradiated surface/total surface ratio equal to 0.95.
During the entire working life of the tube, a quantity of getter strip is wrapped around each shield inside the glass enclosure to ensure the designed vacuum conditions.