Miguel Diago-Martínez

Desert dune sand is considered as a potential sensible heat thermal energy storage (TES) material. Several samples are collected from different locations of the desert in the United Arab Emirates (UAE), and relevant thermophysical and mechanical properties are measured. In addition, the optical properties of desert sand are investigated to evaluate its performance as a direct solar absorber. Thermogravimetric analyses show that the samples appear to be thermally stable between approximately… Show more

Desert dune sand is considered as a potential sensible heat thermal energy storage (TES) material. Several samples are collected from different locations of the desert in the United Arab Emirates (UAE), and relevant thermophysical and mechanical properties are measured. In addition, the optical properties of desert sand are investigated to evaluate its performance as a direct solar absorber. Thermogravimetric analyses show that the samples appear to be thermally stable between approximately 650 °C to 1000 °C following an initial mass loss occurring during the first heating cycle. The transformation of calcium carbonate into calcium oxide at higher temperature during the first heating process has a negative impact on the solar absorption of the sand. In addition, the high calcium content leads to sand agglomeration which has significant implications on receiver design and operation. It is therefore critical to locate sand collection points with low carbonate content. Show less

Abstract:
Desert sand from the United Arab Emirates (UAE) is considered as a possible sensible heat, thermal energy storage (TES) material. Its thermal stability, specific heat capacity and tendency to agglomerate are studied at high temperatures. The analyses show that it is possible to use desert sand as a TES material up to 800-1000 °C. Above 800 °C, weak agglomeration effects start to become significant. The samples become solid above 1000 °C. This may represent a major operating limit… Show more

Abstract:
Desert sand from the United Arab Emirates (UAE) is considered as a possible sensible heat, thermal energy storage (TES) material. Its thermal stability, specific heat capacity and tendency to agglomerate are studied at high temperatures. The analyses show that it is possible to use desert sand as a TES material up to 800-1000 °C. Above 800 °C, weak agglomeration effects start to become significant. The samples become solid above 1000 °C. This may represent a major operating limit depending on the handling mechanism in place for the possible transport of the sand. The sand chemical composition is analyzed with the XRF and XRD techniques, which reveal the dominance of quartz and carbonates. Finally, the spectral absorptivity of the samples is measured before and after a thermal cycle, as it may be possible to use the desert sand not only as a TES material but also as a direct solar absorber. Show less

Abstract:
An energy and exergy analysis of a novel solid particle solar receiver is presented based on experimental data and well-known correlations found in the literature. A sand sample from the deserts of the United Arab Emirates has been chosen as the solar absorber and heat carrier material. The intent of the receiver in consideration is to be used as a part of a sensible Thermal Energy Storage system for Concentrated Solar Power plants based upon the concept of storing solar heat in… Show more

Abstract:
An energy and exergy analysis of a novel solid particle solar receiver is presented based on experimental data and well-known correlations found in the literature. A sand sample from the deserts of the United Arab Emirates has been chosen as the solar absorber and heat carrier material. The intent of the receiver in consideration is to be used as a part of a sensible Thermal Energy Storage system for Concentrated Solar Power plants based upon the concept of storing solar heat in sand particles for a later discharge through a specific sand-steam heat exchanger. The results obtained in this work, based on experimental values, indicate low efficiency figures that might be caused by imperfections on the experimental setup and on the original design. Several paths of improvement are discussed in conclusion. Show less

Abstract:
An innovative gravity-fed combined solar receiver/storage system for thermal energy storage (TES) is presented for concentrated solar power (CSP) plants with beam down tower configuration. Sand particles are employed as heat collector, heat transfer and thermal energy storage media in contrast to conventionally used materials such as molten salts or synthetic oils. Relevant properties of two sand samples from the United Arab Emirates (UAE) deserts are examined. A prototype of the… Show more

Abstract:
An innovative gravity-fed combined solar receiver/storage system for thermal energy storage (TES) is presented for concentrated solar power (CSP) plants with beam down tower configuration. Sand particles are employed as heat collector, heat transfer and thermal energy storage media in contrast to conventionally used materials such as molten salts or synthetic oils. Relevant properties of two sand samples from the United Arab Emirates (UAE) deserts are examined. A prototype of the receiver was manufactured and its elements were characterized. Preliminary tests on the prototype were performed under the concentrated flux of a 2 kW solar furnace and associated results are presented. Show less

Abstract:
Desert sand samples were thermally analyzed and their suitability for use as sensible heat thermal energy storage (TES) media is evaluated. Mass loss during heating was monitored with a thermal gravimetric analyzer (TGA) linked to a Fourier transform infrared spectrometer (FTIR). This technique showed that the relative mass loss rate of all the samples is comparable and that carbon dioxide is produced during their degradation. The calcite content of each sample is estimated… Show more

Abstract:
Desert sand samples were thermally analyzed and their suitability for use as sensible heat thermal energy storage (TES) media is evaluated. Mass loss during heating was monitored with a thermal gravimetric analyzer (TGA) linked to a Fourier transform infrared spectrometer (FTIR). This technique showed that the relative mass loss rate of all the samples is comparable and that carbon dioxide is produced during their degradation. The calcite content of each sample is estimated assuming full calcination during the process. Additionally, larger fractions of the samples were heated in a high temperature electric furnace. This experiment showed that some samples tend to agglomerate at high temperatures, thus rendering their use as heat transfer fluid media questionable. Furthermore, color change from lighter tones to whiter tones is observed. This effect may impact the radiative properties of the samples, especially their solar absorptivity values. Finally, the average heat capacity in the 150-1100 °C temperature range was measured with a differential scanning calorimeter. The average heat capacity for all the samples was 926.1 J kg-1 K-1. Show less