Water sorption heats on silica-alumina-based composites for interseasonal heat storage

Abstract

CaCl 2 -containing composites have been prepared by depositing the hydrated salt (by incipient wetness impregnation) on three different silica-aluminas with various Si/Al ratios. The surface area and porosity of all the samples were determined by N 2 -adsorption at -196°C, and their water sorption properties were investigated by thermogravimetry linked to differential scanning calorimetry (TG-DSC) in order to determine the quantity of adsorbed/desorbed water and the related heats. The heat released and the quantity of adsorbed water were found to depend on parameters such as the silica-alumina pore diameters, the Si/Al ratio, and the presence of accessible CaCl 2 active phase. The short-term stability of both supports and composites has been also checked by performing successive hydration-dehydration cycles. The sample with the lower Si/Al ratio provided the highest heat per surface area of material, and the heat released per mol of water increased with the amount of Al 2 O 3 present in the samples. The deposition of CaCl 2 positively acted on the quantity of heat released during the water sorption, and the composite with the higher alumina content (75 mass% Al) showed the largest heat released per m 2 of material (2.4 J m -2 ) compared to those containing 25 and 13 mass% Al (1.4 and 1.2 J m -2 , respectively).

Effect of NaOH addition on the thermochemical heat storage capacity of nanoporous molecular sieves

“…The hydration/dehydration behavior of the zeolites and the corresponding composites was studied by using a TG‐DSC‐111 from Setaram. Before carrying out the TG‐DSC measurement, zeolites and their corresponding composite materials were pretreated under vacuum at 150 °C during 3 h. Then, a hydration step was carried out for 16 h at constant temperature (20 °C) with a partial water vapor pressure of 0.78 kPa, and then dehydrated again using a temperature ramp of 2 °C min −1 from 20 °C to 150 °C followed by isothermal plateau at 150 °C during 3 h before cooling to room temperature, as detailed in a previous work . The error on the hydration/dehydration heat values is around ±15 J g −1 of sample.…”

A Critical Review of Solid Materials for Low-Temperature Thermochemical Storage of Solar Energy Based on Solid-Vapour Adsorption in View of Space Heating Uses

“…Isostructural compounds with Fe 3+ or Al 3+ instead of Cr 3+ could also be obtained [291]. A high water uptake of 1.01 g g −1 onto MIL-101(Cr) was reported by Ehrenmann et al who obtained an S-shaped adsorption isotherm [89]. Higher water uptake of 1.2 g g −1 and 1.47 g g −1 were measured, respectively, by Akiyama et al and Elsayed et al [277,292].…”

“…The intra-particle porosity is one of the principal characteristics of the adsorbents that are pertinent to their use in thermochemical energy storage. The adsorption phenomena should be carried out making use of mesoporous (pore size in the range of 2–50 nm) or/and microporous (pore size less than 2 nm) solids in order to enhance the adsorbate uptake and intensify the heat exchange during each charge-discharge cycle [ 16 , 57 , 69 , 70 , 77 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 ]. This is the best way to increase the specific surface area, in line with the first criterion.…”

“…Higher water uptake of 1.2 g g −1 and 1.47 g g −1 were measured, respectively, by Akiyama et al and Elsayed et al [ 277 , 292 ]. MIL-101(Cr) exhibited a steep retention of water vapour in a relative pressure range between 0.30 and 0.6 [ 89 ]. This hydrophilic-hydrophobic switching behaviour was considered as making the regeneration easier under 363 K. MIL-100(Cr) possessing smaller pores of 2.5 nm and 2.9 nm, was shown to adsorb less water vapour (ca.…”

Reversible formation of alcohol solvates and their potential use for heat storage

“…Storage and utilization of thermal energy are of utmost importance for a sustainable energy future. There are three main approaches in this field, e.g., sensible heat storage in water [1,2], utilization of latent heat by phase change materials (PCM) [3][4][5][6][7][8][9][10][11][12][13][14][15], and conversion to chemical energy by different thermochemical reactions [16][17][18][19][20][21][22]. Heat storage via reversible thermochemical reactions has several benefits, such as high energy density per volume material and low long-term losses.…”