A zeolite 13X/magnesium sulfate–water sorption thermal energy storage device for domestic heating

Abstract

A sorption thermal energy storage (TES) device for domestic heating is presented in this article. The TES device adopts the new design scenario with valve-less adsorber and separate reservoir to eliminate the largediameter vacuum valve for vapor flow, which decreases the cost, reduces the vapor flow resistance, and improves the system reliability. The device is charged by the electric heater, which can add much flexibility to the building energy system as well as contribute to the valley filling and peak shaving from demand side management. The newly developed composite sorbent of zeolite 13X/MgSO4/ENG-TSA (expanded natural graphite treated with sulfuric acid) with the salt mass fraction of 15% in the zeolite 13X/MgSO4 mixture is tested and used in the TES device (denoted as XM15/ENG-TSA). Experimental results show that the TES device with XM15/ENG-TSA has the energy storage density of 120.3 kWh•m −3 at 250°C charging temperature and 25-90°C discharging temperature. The temperature lift is as high as 65-69°C with the adsorption and evaporating temperatures of 25°C. The impregnation of MgSO4 dramatically improves the temperature rising rate during the adsorption heat recovery process, but the specific energy storage capacity of XM15/ENG-TSA is similar to that of zeolite 13X/ENG-TSA. The effect of the impregnated MgSO4 suggests that MgSO4 can be used for low-temperature TES to relieve the self-hindrance of the hydration reaction.

New kinetic model of the dehydration reaction of magnesium sulfate hexahydrate: Application for heat storage

“…The simultaneous kinetic parameter estimation was performed under constrained non-linear optimization in Matlab (fminsearch). Used of non-linear solvers consists in minimizing the squared error between simulated and experimental data as follow: (19) where Yi,sim and Yi,exp are respectively simulated and experimental values referring to αε values of Eqs. (13)- (15) and to (dΔm/dt) of Eqs.…”

“…Since the salt crystal of small size is dispersed within the porous structure, the problem of agglomeration is limited and both heat and mass transfer in the granular medium remain efficient, leading to an improvement of the material lifetime. The use of active porous matrix such as silica gel, zeolite, MOFs, etc... allows to benefit from the heat produced by the chemical reaction on the hygroscopic salt and by the adsorption on the porous material [14][15][16][17][18][19][20][21][22][23][24][25]. Nevertheless, the development of such a system remains a technological challenge, the main obstacle being the incomplete understanding of the involved physicochemical phenomena.…”

Cementitious composite materials for thermal energy storage applications: a preliminary characterization and theoretical analysis

“…Comparing the water uptake of the specific composite considered in this study with other MgSO 4 composite materials for thermal energy storage, their values are not considerably different. In fact, while the maximum water vapour uptake for the composite synthesised in this work was of , values in the order of 0.15–0.17 30 , 31 have been reported for composites based on Zeolite 13X and MgSO 4 .…”

Thermochemical heat storage ability of ZnSO 4 · 7H 2 O as potential long‐term heat storage material

“…However, these salt hydrates undergo various drawbacks, for instance, due to agglomeration, low rehydration enthalpy, and poor cyclicability of MgSO 4 significantly reduce heat recovery (only 55% energy is recovered). Moreover, at high temperature the crystal of materials transform into byproducts with decrease lifetime of salt hydrate and at ambient storage temperature (25°C) the salt hydrates displayed self‐discharging drawback 11,12 . In addition, at practical circumstances, the hydration reaction, enthalpy, low water sorption, and cyclicability of these salt hydrates become very slow, resulting in poor heat storage 6,13,14 .…”