Abstract
Today the technical limit for solar towers is represented by the temperature that can be reached with current accumulation and exchange fluids (molten salts are generally adopted and the max temperatures are generally below 600 °C), even if other solutions have been suggested that reach 800 °C. An innovative solution based on liquid lead has been proposed in an ongoing experimental project named Nextower. The Nextower project aims to improve current technologies of the solar sector by transferring experience, originally consolidated in the field of nuclear plants, to accumulate heat at higher temperatures (T = 850–900 °C) through the use of liquid lead heat exchangers. The adoption of molten lead as a heat exchange fluid poses important criticalities of both corrosion and creep resistance, due to the temperatures and structural stresses reached during service. Liquid lead corrosion issues and solutions in addition to creep-resistant material selection are discussed. The experimental activities focused on technical solutions adopted to overcome these problems in terms of the selected materials and technologies. Corrosion laboratory tests have been designed in order to verify if structural 800H steel coated with 6 mm of FeCrAl alloy layers are able to resist the liquid lead attack up to 900 °C and for 1000 h or more. The metallographic results were obtained by mean of scanning electron microscopy with an energy dispersive microprobe confirm that the 800H steel shows no sign of corrosion after the completion of the tests.
Highlights
This paper outlines the results obtained under the H2020 research project entitled: “Advanced materials solutions for generation high efficiency concentrated solar power (CPS) tower systems”, of which the acronym is NEXTOWER
One of the technical limits for the efficiency of most common solar towers is the temperature (Tmax = 565 ◦ C), which can be reached with current storage and exchange fluids [1,2,3] even if there are other interesting solutions that have been suggested in the literature for service up to 800 ◦ C [4]
The actual innovation consists in the achievement of a higher service temperature (T > 800 ◦ C) in comparison with that of the liquid lead nuclear plants, where the maximum use temperatures are under T = 600 ◦ C, even if further developments are expected to achieve up to 650 ◦ C [5]
Summary
This paper outlines the results obtained under the H2020 research project entitled:. “Advanced materials solutions for generation high efficiency concentrated solar power (CPS) tower systems”, of which the acronym is NEXTOWER. Research activities have focused on providing new solutions for improving current technologies for the production of electricity by concentrating the solar energy, finding a transversal application on experience that has already been consolidated in the field of liquid lead heat exchangers for nuclear use. Activities are carried out, focused on the importance of achieving a more efficient hightemperature receiver and more efficient heat-storage devices to increase the best conversion of solar to thermal energy [6]. Following this path, the present research is focused on the development of a highly efficient thermal energy management by mean of a liquid lead solution. T > 800 ◦ C.800H, ATI Specialty Rolled Products, New Bedford, MA, US) that could be the structu base for creep-resistance, to have all the surfaces exposed to liquid lead coated with
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