SOLEAD Lead Facility: from the conceptual design to the operation

The NEXTOWER H2020 EU project investigates the possibility of using liquid lead as heat storage medium for high-temperature Thermal Energy Storage (TES) in concentrated solar power plants. To that end, within such project, a demonstration TES unit named SOLEAD (SOlar LEAd Demonstrator) is being developed to be coupled with an open volumetric air receiver in a solar tower CSP system. The SOLEAD demonstrator will use pure lead as working fluid and will be tested stand-alone, to address structural material behaviour at very high temperature, without coupling with air receiver. The tests are planned by the ENEA Brasimone R.C. in Italy. The introduction of the paper provides a general summary of the TES and CSP technology. Then a section is devoted to the conceptual design of SOLEAD. In the lead stand-alone experiment, the focus is on the materials corrosion in lead environment. Although the thermal stratification in the main vessel cannot be reproduced in a stand-alone experiment, the thermal cycle of the facility in the range 600-750°C will be properly reproduced in the experimental test. To this aim, external heating cables will heat up the system from 600°C to 750°C, while a proper Air Cooling System (ACS) will cool down the lead pool. A section of the paper contains the design criteria and calculation of the ACS with the air flowing on an annular gap between the vessel and the insulation. The power provided and extracted by the two systems (heating cables and ACS) is around 30 kW, so that the temperature range 600-750°C can be covered in about 8 hours and a complete cycle can be carried out in one day. Finally, a brief summary of the operational procedures needed from lead melting to the materials inspection is provided. The plan is to test the vessel for 4 months with daily thermal cycles to assess the resistance of FeCrAl materials exposed to very high temperature lead.