scholarly journals Testing thermocline filler materials and molten-salt heat transfer fluids for thermal energy storage systems used in parabolic trough solar power plants.

2004 ◽  
Author(s):  
Michael Kelly ◽  
Paul Hlava ◽  
Douglas Brosseau
Author(s):  
Doug Brosseau ◽  
Mike Edgar ◽  
John W. Kelton ◽  
Kye Chisman ◽  
Daniel Ray ◽  
...  

Parabolic trough power systems that utilize concentrated solar energy to generate electricity are a proven technology. Industry and laboratory research efforts are now focusing on integration of thermal energy storage as a viable means to enhance dispatchability of concentrated solar energy. One option to significantly reduce costs is to use thermocline storage systems, low-cost filler materials as the primary thermal storage medium, and molten nitrate salts as the direct heat transfer fluid. Prior thermocline evaluations and thermal cycling tests at the Sandia National Laboratories’ National Solar Thermal Test Facility identified quartzite rock and silica sand as potential filler materials. An expanded series of isothermal and thermal cycling experiments were planned and implemented to extend those studies in order to demonstrate the durability of these filler materials in molten nitrate salts over a range of operating temperatures for extended timeframes. Upon test completion, careful analyses of filler material samples, as well as the molten salt, were conducted to assess long-term durability and degradation mechanisms in these test conditions. Analysis results demonstrate that the quartzite rock and silica sand appear able to withstand the molten salt environment quite well. No significant deterioration that would impact the performance or operability of a thermocline thermal energy storage system was evident. Therefore, additional studies of the thermocline concept can continue armed with confidence that appropriate filler materials have been identified for the intended application.


Author(s):  
Iñigo Ortega ◽  
Javier Rodríguez-Aseguinolaza ◽  
Antoni Gil ◽  
Abdessamad Faik ◽  
Bruno D’Aguanno

Slag is one of the main waste materials of the iron and steel manufacturing. Every year about 20 million tons of slag are generated in the United States and 43.5 million tons in Europe. The revalorization of this by-product as heat storage material in thermal energy storage systems would have numerous advantages which include: the possibility to extend the working temperature range up to 1000 °C, the reduction of the system cost and, at the same time, the decrease of the quantity of waste in the iron and steel industry. In this paper, two different electric arc furnace slags from two companies located in the Basque Country (Spain) are studied. Their thermal stability and compatibility in direct contact with the most common heat transfer fluids used in the concentrated solar power plants are analyzed. The experiments have been designed in order to cover a wide temperature range up to the maximum operation temperature of the future generation of concentrated solar power plants (1000 °C). In particular, three different fluids have been studied: synthetic oil (Syltherm 800®) at 400 °C, molten salt (Solar Salt) at 500 °C and air at 1000 °C. In addition, a complete characterization of the studied slags and fluids used in the experiments is presented showing the behavior of these materials after 500 hour laboratory-tests.


2005 ◽  
Vol 127 (1) ◽  
pp. 109-116 ◽  
Author(s):  
Doug Brosseau ◽  
John W. Kelton ◽  
Daniel Ray ◽  
Mike Edgar ◽  
Kye Chisman ◽  
...  

Parabolic trough power systems that utilize concentrated solar energy to generate electricity are a proven technology. Industry and laboratory research efforts are now focusing on integration of thermal energy storage as a viable means to enhance dispatchability of concentrated solar energy. One option to significantly reduce costs is to use thermocline storage systems, low-cost filler materials as the primary thermal storage medium, and molten nitrate salts as the direct heat transfer fluid. Prior thermocline evaluations and thermal cycling tests at the Sandia National Laboratories’ National Solar Thermal Test Facility identified quartzite rock and silica sand as potential filler materials. An expanded series of isothermal and thermal cycling experiments were planned and implemented to extend those studies in order to demonstrate the durability of these filler materials in molten nitrate salts over a range of operating temperatures for extended time frames. Upon test completion, careful analyses of filler material samples, as well as the molten salt, were conducted to assess long-term durability and degradation mechanisms in these test conditions. Analysis results demonstrate that the quartzite rock and silica sand appear able to withstand the molten salt environment quite well. No significant deterioration that would impact the performance or operability of a thermocline thermal energy storage system was evident. Therefore, additional studies of the thermocline concept can continue armed with confidence that appropriate filler materials have been identified for the intended application.


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