Effect of Desert Environmental Condition on an Open Direct Absorption Molten Salt Solar Receiver/Storage System

  • Muna AlQaydi

Student thesis: Master's Thesis

Abstract

State-of-the-art thermal energy storage (TES) for concentrated solar power (CSP) plants is the two-tank molten salt technology. A cost-effective alternative might be a single-tank that works as an open direct absorption solar receiver, and at the same time as a thermal energy storage unit. This concept was called Concentrated Solar Power on Demand Demonstration (CSPonD Demo). In this concept, an insulated divider plate separates the hot and the relatively 'cold' parts of the salt in the tank and the sunlight is concentrated directly into the molten salt from the top for volumetric absorption of the solar energy. As the system is open to the atmosphere, impurities such as sand could fall into the bath of salt. This work studies the effect of desert environmental conditions on the thermo-physical properties of molten salts. The salts that was used for this study is a binary nitrate mixture, commercially called Solar Salt (60 wt. % NaNO3, 40 % wt. KNO3). Thermal analyses on nitrate salts mixture were performed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). These analyses were conducted to mainly obtain melting and solidification points, heat capacity, decomposition temperatures and mass loss. The measurements were carried out under different atmospheres (nitrogen, air, and oxygen) and with adding 2 % (w/w) sand. Sand did not affect the melting temperature of the nitrate mixture but it increases the solicitation temperature by 1 % and specific heat capacity by 22 %. Decomposition temperature was reduced by adding sand however; it was higher under air and oxygen than under nitrogen. In addition, sand contributed in increasing mass loss of nitrate salts mixture but it was less than 3% under nitrogen and air. Futhermore, mass loss measurements with higher mass and bigger crucibles showed that the nitrate salts mixture is stable during the 8 hours of experiment, which means that by up-scaling the system, the mass losses will be minimize. Another interesting result is that oxygen causes a slight increase in mass by more than 2 % due to the reversible reaction between the nitrate and nitrite. For conclusion, the same measurements should be repeated for samples taken from the prototype to confirm the results found at laboratory scale.
Date of AwardMay 2017
Original languageAmerican English
SupervisorNicolas Calvet (Supervisor)

Keywords

  • Solar Power
  • Thermal Energy Storage
  • Concentrated Solar Power
  • Demand Demonstration (CSPonD Demo)
  • Solar Salt
  • Thermogravimetric Analysis
  • Differential Scanning Calorimetry.

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