Liquid Calcium Chloride Solar Storage: Concept and Analysis

Abstract

Aqueous calcium chloride has a number of potential advantages as a compact and long-term solar .storage medium compared with sensibly heated water. The combination of sensible and chemical binding energy of the liquid desiccant provides higher energy densities and lower thermal losses, as well as a temperature lift during discharge via an absorption heat pump. Calcium chloride is an excellent choice among desiccant materials because it is relatively inexpensive, nontoxic, and environmentally safe. This paper provides an overview of its application for solar storage and presents a novel concept for storing the liquid desiccant in a single storage vessel. The storage system uses an internal heat exchanger to add and discharge thermal energy and to help manage the mass, momentum, and energy transfer in the tank. The feasibility of the proposed concept is demonstrated via a computational fiuid dynamic study of heat and mass tran.sfer in the system over a range ofRayleigh, Lewis, Prandtl, and buoyancy ratio numbers expected in practice.

Development of Space Heating and Domestic Hot Water Systems with Compact Thermal Energy Storage

“…All transient experiments as well as a computational fluid dynamic study [Quinnell et al, 2011 andQuinnell andDavidson, 2012c] show that the density interfaces remain stable and the natural convection flows are confined to regions of uniform CaCl 2 mass fraction. Representative data are provided for an experiment in which Ra is of order 10 9 , N is of order 4, Le = 404, and a = 0.5.…”

“…Faster heat and mass transfer rates are possible with liquid absorption. Materials recently investigated include aqueous solutions of CaCl 2 [Quinnell et al, 2011], LiCl [Bales, 2006], NaOH , and KOH [Hui et al, 2011]. Hui et al compare absorption materials for use in low pressure (1.2 -4.2 kPa) absorption cycles and have reported theoretical material energy densities up to 476 kWh/m 3 [Hui et al, 2011], as shown in …”

“…The regenerator is envisioned here as a two-stage device, with boiling in the first stage and heat from the condensed steam driving a second stage [Lowenstein, A., 2005]. Strong LD feeds the heat pump and chiller, both of which return weak LD to the storage tank... CaCL 2 is an inexpensive desiccant and for this application provides similar energy density as LiCl [Quinnell et al, 2011]. The accessible material storage density depends on the operating limits of the system.…”

Thermodynamics and economics of liquid desiccants for heating, ventilation and air-conditioning – An overview

“…when the cooling/dehumidification demand is needed to meet, the concentrated solution is pumped to the absorber, driving the cycle without any further heat needed; once the process is completed, the obtained dilute solution is stored in the dilute solution tank. Sometimes, in reality, one tank was used instead of using two tanks, where the strong and weak solutions were mixed or separated by buoyancy [110]. The energy storage capacity of a liquid desiccant, SC, is defined as [111]:…”

Identification of best available thermal energy storage compounds for low-to-moderate temperature storage applications in buildings

“…Solar energy is stored in a liquid CaCl 2 volume by heating the solution and vaporizing H 2 O. Energy is extracted as water is reabsorbed and/or the solution is cooled (142). The energy density of the material, which is dependent on how the tank is discharged, is 106 kWh/m 3 , similar to that of LiCl for the same operating parameters (98).…”