Laser Induced Release of Encapsulated Noble Gas in SCHOTT Receiver

Abstract Thermo oil based parabolic through technology is limited to operational temperatures close to 400 °C due to the decomposition of the heat transfer fluid and accompanying hydrogen permeation into the vacuum annulus. The presence of hydrogen in the annulus leads to an increase of thermal losses and a decrease in thermal efficiency. In order to overcome this so-called ‘hot tube phenomenon’, SCHOTT introduced the PREMIUM receiver with a capsule containing noble gas placed in the evacuated annulus. The receiver operates after installation with the performance of the standard receiver (PTR 70), until the ‘hot tube phenomenon’ is detected. The encapsulated noble gas will be released via laser drilling the capsule, without further interruption of the plant operation. The opening process utilizes a fiber coupled laser and an alignment tool that is adapted to the conditions in the solar field. The drilling process is optimized for low impact on the receiver components and affordable equipment. Extensive tests confirm the sustained reliability of the receiver components after gas release. SCHOTT has developed a unique solution which is able to improve the receiver's lifetime and performance significantly with low maintenance and low additional costs. This additional feature allows operation at high performance for a significantly longer period than the vacuum lifetime of the product, lowering the LCOE in that way.