Journal of Solar Energy Engineering (Impact Factor: 0.94). 01/2011; 133(3). DOI: 10.1115/1.4004243

ABSTRACT This paper describes an advanced heat transfer fluid (HTF) consisting of a novel mixture of inorganic salts with a low melting point and high thermal stability. These properties produce a broad operating range molten salt and enable effective thermal storage for parabolic trough concentrating solar power plants. Previous commercially available molten salt heat transfer fluids have a high melting point, typically 140 °C or higher, which limits their commercial use due to the risk of freezing. The advanced HTF exploits eutectic behavior with a novel composition of materials, resulting in a low melting point of 65 °C and a thermal stability limit over 500 °C. The advanced HTF described in this work was developed using advanced experiment design and data analysis methods combined with a powerful high throughput experimental workflow. Over 5000 unique mixtures of inorganic salt were tested during the development process. Additional work is ongoing to fully characterize the relevant thermophysical properties of the HTF and to assess its long term performance in realistic operating conditions for concentrating solar power applications or other high temperature processes.

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    Thermochimica Acta 04/2013; 560:34-42. · 1.99 Impact Factor
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    ABSTRACT: The study of the thermal decomposition of molten nitrite/nitrates salt used for thermal energy storage (TES) in concentrating solar power (CSP) was carried-out with a HITEC (Reg. U.S. Patent – Coastal Chemical Company) type salt. This salt is the commercial mixture of NaNO3–KNO3–NaNO2 in the proportions 7–53–40 wt.% (NO2/NO3 weight ratio of 0.7). The study was done by simultaneous DSC/TG-MS analysis between room temperature and 1000 °C in gas atmospheres of argon, nitrogen, air and oxygen. It was found that:•The thermal stability of the salt can be significantly enhanced by controlling the atmosphere.•By two assessment criteria, TG and DSC, the salt operated in an inert atmosphere could be used at temperature of at least 610 °C and when operated in an oxidising atmosphere up to between 650 °C and 700 °C.Oxidising atmosphere was found to change the chemistry of the salt by converting some nitrite to nitrate, and although this may have a bearing on increasing the melting point, it has the benefit of rising the thermal decomposition temperature.
    Solar Energy 01/2012; · 3.54 Impact Factor
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    ABSTRACT: Molten-salt storage is already commercially available for concentrating solar power (CSP) plants, allowing solar power to be produced on demand and to “backup” variable renewable sources such as wind and photovoltaics. The first CSP plants to operate commercially with molten-salt storage utilized parabolic trough concentrators, for example, the Andasol-1 plant. A new type of storage plant has now reached commercial status, with the 19.9-MW $_{rm e}$ Torresol Gemasolar power tower, featuring 15 h of molten-salt storage, having come online in Spain in May 2011. Advantages of the power tower storage system include the elimination of heat transfer oil and associated heat exchangers, a lower salt requirement, higher steam cycle efficiency, better compatibility with air cooling, improved winter performance, and simplified piping schemes. Near-term advances in molten-salt power tower technology include planned up-scaling, with SolarReserve due to begin constructing a 110-MW $_{rm e}$ plant in Nevada by August 2011. Other advances include improvements to the thermal properties of molten salts and the development of storage solutions in a single tank. With these developments at hand, CSP will continue to provide dispatchable solar power, with the capacity to provide energy storage for 100% renewable electricity grids in sun-belt countries.
    Proceedings of the IEEE 03/2012; · 6.91 Impact Factor


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