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Sorption and Thermochemical Materials
DFT Study on Characterization of Hydrogen Bonds in the Hydrates of MgSO4
August 2012
By: Eldhose Iype, Silvia V. Nedea, Camilo C. M. Rindt , Anton A. van Steenhoven, Herbert A. Zondag , and A. P. J. Jansen
Publisher: Copyright © 2012 American Chemical Society
Magnesium salt hydrates are potential thermo-chemical energy storage materials considering its high energy storage density and its availability. However, in practical applications, these materials suffers from low efficiency due to their sluggish kinetics and significant structural changes during hydration and dehydration. A DFT PW91-TZ2P level optimization is performed on the various hydrates of magnesium sulfate molecules to study their structural properties. The study identifies a wide network of hydrogen bonds which is significantly influencing the chemical structure of the molecules. These hydrogen bonds appear to cause distortions in the hydrated structures and even hindering the coordination of water with magnesium resulting in lower energy isomers. In the case of hexa-hydrated isomers, the hydrogen bond stabilizes a conformation which has only four coordinated water molecules, and is energetically more stable than the conformation with six coordinated water molecules. The sluggish hydration kinetics in magnesium sulfate is attributed to the strong hydrogen bond network present in the crystals. In addition, the hexahydrated structure exhibits an intra-molecular proton transfer reaction. This suggests that the strong hydrogen bond interactions potentially dissociates water molecules during hydration.
Document Number: 10.1021/jp3025649
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Adsorption properties of porous materials for solar thermal energy storage and heat pump applications
SHC 2012
July 2012 - PDF 0.21MB
By: J. Jänchen, H. Stach
The water adsorption properties of modified porous sorbents for solar thermal energy storage and heat transformation have been investigated by thermogravimetry (TG) differential thermogravimetry (DTG), microcalorimetry, measurements of water adsorption isotherms, and storage tests. A chabazite type SAPO, a dealuminated faujasite type zeolite, and a mesostructured aluminosilicate, have been synthesized and compared with common zeolites X, Y and silica gel. It has been found that optimized lattice composition and pore architecture contribute to well adapt hydrophilic properties and a beneficial steep isotherm.
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Development of a Seasonal Thermochemical Storage System
Proceedings of the (1st International Conference on Solar Heating and Cooling for Buildings and Industry 2012, San Francisco, USA, 9-11 july 2012
July 2012
By: R. Cuypers, N. Maraz, J. Eversdijk, C. Finck, E. Henquet, H. Oversloot, H. van ‘t Spijker, A. de Geus
Publisher: Energy Procedia
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New two-component water sorbent CaCl2-FeKIL2 for solar thermal energy storage
July 2012 - PDF 1MB
By: Alenka Ristic, Darja Maucec, Stefan K. Henninger, Venceslav Kaucic
Publisher: Microporous and Mesoporous Materials
A new two-component (composite) water sorbent CaCl2-FeKIL2 has been developed for sorption-based solar thermal energy storage. The matrix of the composite is FeKIL2 material with disordered mesopores, high surface area of 712 m2/g and mesopore dimensions between 4 and 29 nm. The composite, prepared by wet impregnation of FeKIL2 with CaCl2, has lower surface area (418 m2/g) and similar mesopore dimensions as the matrix. The maximum water sorption capacity of FeKIL2 is 0.21 g/g, while the composite possesses 3 times higher maximum water sorption capacity due to the presence of the salt in the matrix. Heat of adsorption of the composite is 50.4 kJ/mol. A short-term cycling test between temperatures of 150 and 40 C at a water vapour pressure of 5.6 kPa confirms a comparatively good hydrothermal stability of the composite.
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MERITS: More Effective use of Renewables Including compact seasonal Thermal energy Storage
InnoStock Conference 2012, Lleida, Spain, 16-18 May 2012
May 2012
By: R. Cuypers, C. Finck, E. Henquet, H. Oversloot, A. de Geus
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Preparation, hydrothermal stability and thermal adsorption storage properties of binderless zeolite beads
International Journal of Low-Carbon Technologies Advance Access published May 5, 2012
May 2012 - PDF 0.39MB
By: Jochen Janchen, Kristin Schumann, Erik Thrun, Alfons Brandt, Baldur Unger and Udo Hellwig
Novel binderless zeolite beads of types A and X have been synthesized and characterized by scanning electron microscopy, mercury intrusion, nitrogen adsorption, thermogravimetry, water adsorption isotherm measurements, cyclic hydrothermal treatments and storage tests. The binderless molecular sieves show an improved adsorption capacity, sufficient hydrothermal stability, higher specific energies and the potential for a better performance density of the storage. Both open and closed storage tests have shown comparable adsorption capacities and specific energies for the binderless molecular sieves. A significantly higher discharging temperature, however, could be realized with the open storage system.
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Characterization of MgSO4 Hydrate for Thermochemical Seasonal Heat Storage
2009
By: V.M. van Essen H.A. Zondag J. Cot Gores L.P.J. Bleijendaal M. Bakker R. Schuitema W.G.J. van Helden Z. He C.C.M. Rindt
Publisher: Journal of Solar Energy Engineering, Vol. 131(2009)
Water vapor sorption in salt hydrates is one of the most promising means for compact, low loss, and long-term storage of solar heat in the built environment. One of the most interesting salt hydrates for compact seasonal heat storage is magnesium sulfate heptahydrate (MgSO4·7H2O). This paper describes the characterization of MgSO4·7H2O to examine its suitability for application in a seasonal heat storage system for the built environment. Both charging (dehydration) and discharging (hydration) behaviors of the material were studied using thermogravimetric differential scanning calorimetry, X-ray diffraction, particle distribution measurements, and scanning electron microscope. The experimental results show that MgSO4·7H2O can be dehydrated at temperatures below 150°C, which can be reached by a medium temperature (vacuum tube) collector. Additionally, the material was able to store 2.2 GJ/m3, almost nine times more energy than can be stored in water as sensible heat. On the other hand, the experimental results indicate that the release of the stored heat is more difficult. The amount of water taken up and the energy released by the material turned out to be strongly dependent on the water vapor pressure, temperature, and the total system pressure. The results of this study indicate that the application of MgSO4·7H2O at atmospheric pressure is problematic for a heat storage system where heat is released above 40°C using a water vapor pressure of 1.3 kPa. However, first experiments performed in a closed system at low pressure indicate that a small amount of heat can be released at 50°C and a water vapor pressure of 1.3 kPa. If a heat storage system has to operate at atmospheric pressure, then the application of MgSO4·7H2O for seasonal heat storage is possible for space heating operating at 25°C and a water vapor pressure of 2.1 kPa.
Document Number: p. 041014-1/7
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