Thermochemical Material Systems for Heating Ventilation and Air Conditioning

Abstract

A thermal energy storage (TES) system using a thermochemical material (TCM) may have a discharging mode (i.e., heat releasing mode) and a charging mode (i.e., heat absorbing mode), both of which can be used in building heating, ventilation, and air conditioning (HVAC) applications. During both modes, the water vapor/moisture contained in the air interacts with the TCM. During discharging, water vapor is absorbed by the TCM and the heat of reaction is released to the air, resulting in a substantially dehumidified air which may be slightly heated and can be used for heating applications. During charging, the TCM may be heated to drive the reversible dehydration reaction and release the moisture to the air, preparing it for cooling applications.

Description

BACKGROUND

Achieving net-zero carbon emissions by 2050 requires pursuing multi-source renewable energy supplies and optimizing energy performance at end use. Utilizing renewable energy at a large scale requires energy storage. In the United States, buildings consume approximately 40% of total energy and thermal load is the dominate end use. Thus, there remains a significant opportunity to reduce and shift thermal load, motivating the development of thermal energy storage technologies for behind-the-meter application in buildings.

SUMMARY

An aspect of the present disclosure is a method including contacting a thermochemical material (TCM) with a first air stream resulting in a dehumidified and heated first air stream, directing the dehumidified and heated first air stream to interact with a second air stream, and releasing a heated second air stream into an indoor space, in which the first air stream enters the TCM from the indoor space, and the directing causes the second air stream to be heated resulting in the heated second air stream. In some embodiments, the contacting includes receiving the first air stream, and removing a humidity from the first air stream resulting in the dehumidified and heated first air stream, in which the removing results in the humidity being absorbed by the TCM, and the contacting is performed in a TCM bed. In some embodiments, the directing includes receiving the dehumidified and heated first air stream and the second air stream and transferring a heat from the dehumidified and heated first air stream to the second air stream, in which the transferring results in the dehumidified and heated first air stream becoming an exhausted first air stream, and the transferring results in the second air stream becoming the heated second air stream. In some embodiments, the directing is performed in a heat exchanger. In some embodiments, the second air stream enters the heat exchanger from an external ambient. In some embodiments, the TCM is a salt hydrate. In some embodiments, the salt hydrate comprises at least one of magnesium chloride (MgCl₂), strontium bromide (SrBr₂), calcium hydroxide (Ca(OH)₂), potassium carbonate (K₂CO₃), lithium hydroxide (LiOH), or strontium chloride (SrCl₂).

An aspect of the present disclosure is a system including a thermochemical material (TCM) bed configured to receive a first air stream and to release a heated and dehumidified first air stream, and a heat exchanger including a first inlet configured to receive the heated and dehumidified first air stream, a second inlet configured to receive a second air stream, a first outlet configured to release a heated second air stream into an indoor space, and a second outlet configured to release an exhausted first air stream, in which the TCM bed includes a TCM, the TCM bed is configured to absorb a humidity from the first air stream resulting in the dehumidified and heated first air stream being released from the TCM bed, the heat exchanger is configured to transfer heat from the dehumidified and heated air stream to the second air stream, resulting in the heated second air stream being released via the first outlet and the exhausted first air stream being released via the second outlet. In some embodiments, the TCM includes a salt hydrate. In some embodiments, the salt hydrate includes at least one of magnesium chloride (MgCl₂), strontium bromide (SrBr₂), calcium hydroxide (Ca(OH)₂), potassium carbonate (K₂CO₃), lithium hydroxide (LiOH), or strontium chloride (SrCl₂). In some embodiments, the second inlet and the second outlet are substantially co-located.

An aspect of the present disclosure is a method including contacting a mixed air stream with a sorbent material in a first channel, directing a first portion of the mixed air stream to interact with the sorbent material in a second channel, and releasing a second portion of the mixed air stream into an indoor space, in which the directing results in a humidity from the second portion of the mixed air stream to the sorbent material. In some embodiments, the method also includes combining a first air stream and a second air stream to form a mixed air stream, in which the combining occurs prior to the contacting. In some embodiments, the first air stream is sourced from the indoor space. In some embodiments, the second air stream is sourced from an external ambient. In some embodiments, the contacting includes receiving a first air stream and a second air stream into the first channel and placing a sorbent in thermodynamic communication with the mixed air stream, in which the mixed air stream comprises the first air stream and the second air stream. In some embodiments, the contacting also includes contacting the mixed air stream with a water film in the first channel. In some embodiments, the directing includes receiving the first portion of the mixed air stream into the second channel, contacting the sorbent material with the first portion of the mixed air stream in the second channel resulting in an exhausted mixed air stream, and releasing the exhausted mixed air stream to an external ambient. In some embodiments, the first channel and the second channel are separated by a plate. In some embodiments, the plate is substantially permeable by heat and water.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present disclosure are illustrated in the referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting.

FIG. 1 illustrates a method of heat recovery using a thermochemical material (TCM), according to some aspects of the present disclosure.

FIG. 2 illustrates a thermochemical material (TCM)-to-air system, according to some aspects of the present disclosure.

FIG. 3 illustrates air stream states for heat recovery after heating a “stale” indoor air stream using the TCM-to-air system, according to some aspects of the present disclosure.

FIG. 4 illustrates a schematic diagram of a lab-scale TCM-to-air reactor (i.e., a TCM bed) filled with SrCl₂-cement composite, according to some aspects of the present disclosure.

FIG. 5 illustrates a photo of a lab-scale TCM bed filled with SrCl₂-cement composite, according to some aspects of the present disclosure.

FIGS. 6A-B illustrate the temperature profile of an outlet air stream in the TCM bed from experimental data and numerical modeling based on (FIG. 6A) varied timestep Δt=0.02, 0.01 and 0.005 s with Δx=0.0148 m and (FIG. 6B) varied mesh size, Δx=0.0297, 0.0148 and 0.0074 m with Δt=0.01 s, according to some aspects of the present disclosure.

FIGS. 7A-D illustrate the effects of the inlet air RH on (FIG. 7A) outlet air temperature profile, (FIG. 7B) the cumulative volumetric energy density of the TCM bed, (FIG. 7C) the spatial averaging of the extent of conversion; (FIG. 7D) the spatial profile of extent of conversion with approximately 60% RH inlet airstream, according to some aspects of the present disclosure.

FIGS. 8A-D illustrate (FIG. 8A) Outlet air temperature and (FIG. 8B) extent of conversion profiles with inlet air at approximately 21° C. and approximately 30% RH, (FIG. 8C) outlet air temperature, and (FIG. 8D) extent of conversion profiles with inlet air at approximately 21° C. and approximately 60% RH, according to some aspects of the present disclosure.

FIGS. 9A-B illustrate (FIG. 9A) outlet air temperature and (FIG. 9B) extent of conversion profiles with different TCM bed cylinder sizes, according to some aspects of the present disclosure.

FIG. 10 illustrates the energy density of SrCl₂-based TCM bed in different scenarios, according to some aspects of the present disclosure.

FIGS. 11A-C illustrate air states in psychrometric charts for (FIG. 11A) indoor air stream direct heating mode, (FIG. 11B) outdoor air stream direct heating mode, and (FIG. 11C) outdoor air stream indirect heating mode using a TCM bed, according to some aspects of the present disclosure.

FIGS. 12A-D illustrate the outlet air temperature of the TCM bed during hydration between numerical simulation and experimental data with dehydration temperature at (FIG. 12A) approximately 50° C., (FIG. 12B) approximately 70° C., (FIG. 12C) approximately 130° C., and (FIG. 12D) approximately 150° C., according to some aspects of the present disclosure.

FIG. 13 illustrates a substantially regenerative two fluid TCM system, according to some aspects of the present disclosure.

FIG. 14 illustrates air stream states for heat recovery after heating indoor air stream using the two fluid TCM system, according to some aspects of the present disclosure.

REFERENCE NUMERALS
100 method
105 contacting
110 directing
115 releasing
200 system
205 thermochemical material (TCM) bed
210 first air stream
215 heated and dehumidified first air stream
220 second air stream
225 heated second air stream
230 exhausted first air stream
235 heat exchanger
240 inlet
245 outlet
250 indoor space
300 system
305 first channel
310 mixed air stream
315 first portion of the mixed air stream
320 second portion of the mixed air stream
325 water film
330 sorbent material
335 second channel
340 exhausted mixed air stream
345 separator plate
350 air duct

DETAILED DESCRIPTION

The embodiments described herein should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein. References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, “some embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

As used herein the term “substantially” is used to indicate that exact values are not necessarily attainable. By way of example, one of ordinary skill in the art will understand that in some chemical reactions 100% conversion of a reactant is possible, yet unlikely. Most of a reactant may be converted to a product and conversion of the reactant may asymptotically approach 100% conversion. So, although from a practical perspective 100% of the reactant is converted, from a technical perspective, a small and sometimes difficult to define amount remains. For this example of a chemical reactant, that amount may be relatively easily defined by the detection limits of the instrument used to test for it. However, in many cases, this amount may not be easily defined, hence the use of the term “substantially”. In some embodiments of the present invention, the term “substantially” is defined as approaching a specific numeric value or target to within 20%, 15%, 10%, 5%, or within 1% of the value or target. In further embodiments of the present invention, the term “substantially” is defined as approaching a specific numeric value or target to within 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% of the value or target.

As used herein, the term “about” is used to indicate that exact values are not necessarily attainable. Therefore, the term “about” is used to indicate this uncertainty limit. In some embodiments of the present invention, the term “about” is used to indicate an uncertainty limit of less than or equal to ±20%, ±15%, ±10%, ±5%, or ±1% of a specific numeric value or target. In some embodiments of the present invention, the term “about” is used to indicate an uncertainty limit of less than or equal to ±1%, ±0.9%, ±0.8%, ±0.7%, ±0.6%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, or ±0.1% of a specific numeric value or target.

Among other things, the present disclosure relates to the use of thermochemical materials (TCMs) for thermal energy storage (TES) in building heating, ventilation, and air conditioning (HVAC) applications. TCMs may release or absorb energy through a reaction, often a hydration/dehydration reaction. A TES system using a TCM may have a discharging mode (i.e., heat releasing mode) and a charging mode (i.e., heat absorbing mode). During both modes, the water vapor/moisture contained in an air stream interacts with the TCM. During discharging, water vapor is absorbed by the TCM and the heat of reaction (physical or chemical) is released to the air stream, resulting in a substantially dehumidified air stream which may be slightly heated and can be used for heating applications. During charging, the TCM may be heated to drive the reversible dehydration reaction and release the moisture to the air stream, possibly preparing it for cooling applications.

TCMs may include a wide range of hydrated salts as well as absorbents like silica gel or zeolite. Examples of TCMs may include such salt hydrates (and/or their composites) as: MgCl₂, SrBr₂, Ca(OH)₂, K₂CO₃, LiOH, and/or SrCl₂. Among those salt hydrates, SrCl₂ is one of the most promising candidates for low-to-medium temperature TES in buildings due to its ease of hydration by water vapor and low dehydration temperatures (in the range of approximately 70 to approximately 150° C.).

In some embodiments, the TES systems using at least one TCM described herein may take latent heat (i.e., water vapor) from the air stream and transform it into sensible heat by releasing the enthalpy of adsorption. This may transform the latent energy in the air stream into sensible energy, thereby increasing the temperature of the airstream. Because the enthalpy of adsorption of a TCM is larger than the enthalpy of vaporization of water, the sensible heat released exceeds the latent energy adsorbed from the air stream.

In some embodiments, the TES systems described herein may be substantially open systems, meaning they are substantially open to ambient conditions. The sorbate in an open system is typically water vapor, which may be pulled from or added to the air stream as the air stream interacts with the TCM. This water vapor may be available as natural humidity in the air stream and/or from an external source such as humidifier. One advantage of open systems is that the working fluid and the process fluid are the same: humid air. This makes the overall system configuration relatively simple and inexpensive. No auxiliary heat exchangers, heat transfer fluids, and pumps are required. This leads to the minimization of parasitic energy consumption. Additionally, an open system may be substantially at ambient pressure and does not require evacuated chambers.

During discharging/absorption mode, the TCM has a lower hydration state than the air stream and/or is in a state with a high affinity for water vapor.

In some embodiments, the thermodynamic equilibrium conditions between the material and the air stream are related to the partial pressure of water vapor in the moist air. The process of moisture transport from the air stream may be directedly related to the temperature difference between the air stream and the TCM and/or also on the extent of hydration of the TCM. During the initial phase of discharging/absorption, typically there is a high rate of vapor diffusion and absorption (of moisture into the TCM) which leads to high heat release. But at later stages of absorption/discharging this transport rate decreases and it can cause the delivered heat transfer rate to the air stream to gradually decline. Also, during absorption/discharging, the key driving force for vapor transport is the difference in the moisture content of the TCM and the airstream. Transport dynamics of this type of process are generally slow. During desorption/charging, the vapor transport from the TCM is also significantly determined by the temperature difference between the air-stream and the TCM. This may lead to different time scales for charging and discharging.

FIG. 1 illustrates a method 100 of heat recovery using a thermochemical material (TCM), according to some aspects of the present disclosure. In some embodiments, the method 100 includes contacting 105, directing 110, and releasing 115.

In some embodiments, the method 100 first includes contacting 105 a TCM with an air stream. At least a portion of this air stream may be sourced from inside a building (i.e., an indoor air source). This may result in a substantially dehumidified and/or heated air stream.

In some embodiments, the method 100 next includes directing 110 the substantially dehumidified and/or heated air stream to interact with an air stream sourced from outside of the building (i.e., an external air source). In some embodiments, the method 100 may include directing 110 at least a portion of the substantially dehumidified and/or heated air stream to interact with the TCM.

In some embodiments, the method 100 next includes releasing 115 an air stream having contacted the TCM into the indoor air space.

FIG. 2 illustrates a thermochemical material (TCM)-to-air system 200, according to some aspects of the present disclosure. In some embodiments, the system 200 includes a TCM bed 205 and a heat exchanger 235. The TCM bed 205 may be configured to receive a first air stream 210 and to release a heated and dehumidified first air stream 215. The heat exchanger 235 may have a first inlet 240a, a second inlet 240b, a first outlet 245a, and a second outlet 245b. The first inlet 240a may be configured to receive the heated and dehumidified first air stream 215. The second inlet 240b may be configured to receive a second air stream 220. The first outlet 245a may be configured to release a heated second air stream 225 into an indoor space 250. The second outlet 245b may be configured to release an exhausted first air stream 230.

FIG. 3 illustrates air stream states for heat recovery after heating a “stale” indoor air stream (i.e., the first air stream 210) using a TCM-to-air reactor (i.e., a TCM bed 200), according to some aspects of the present disclosure. As shown in FIG. 3, if heat from the TCM is to be used to heat a second air stream 220, then moisture from first air stream 210 may drive the TCM hydration process (i.e., the charging and discharging modes). This may utilize a substantially balanced ventilation system with co-located exhaust and ventilation ducting. This is shown in FIG. 2, where the exhausted first air stream 230 and second air stream 220 are substantially co-located (i.e., on the same side of the heat exchanger 235). As shown in FIG. 3, the second air stream 220 may be heated by the heated and dehumidified first air stream 215 without any additional substantial heating requirements. If ventilation (i.e., fresh air from the outside, or the second air stream 220) is not needed, another configuration of the TCM bed 205 may be used with substantially adiabatic humidification to more effectively use the TCM heat.

In some embodiments, when the TCM bed 200 is utilized, the method 100 may comprise first contacting 105 the TCM bed 205 with the first air stream 210 resulting in the heated and dehumidified first air stream 215. The contacting 105 may be done in the TCM bed 205 and may result in at least some heat and/or humidity being absorbed by the TCM.

Next, the method 100 may include directing 110 the heated and dehumidified first air stream 215 to interact with a second air stream 220. The directing 100 may be performed in the heat exchanger 235. The directing 100 may result in the second air stream 220 absorbing at least some heat and/or humidity from the heated and dehumidified first air stream 215. This may result in the second air stream 220 becoming a heated second air stream 225.

Next, the method 100 may include releasing 115 the heated second air stream 225 into the indoor space 250. The indoor space 250 may be the origin of the first air stream 210. The indoor space 250 may be the interior of a building or a HVAC system within a building.

In some embodiments, the performance of the TES system using a TCM may depend on the conditions of the incoming air stream (i.e., the temperature and/or moisture level).

The experiments described herein used an SrCl₂-cement composite as a TCM/sorbent material 330. SrCl₂·6H₂O (from J. T. Baker, approximately 99% purity CAS no. 10025-70-4), was mixed with dry Portland cement powder in the appropriate ratio. Then approximately 10-15 mL of distilled water was added to the salt and cement mixture. The composite was placed into a mold approximately 7 mm in diameter and dried for approximately 30 minutes at a temperature of approximately 50° C. Once the material was able to retain its shape, it was cut into a cylinder with dimensions of approximately 7×7 mm. The cylindrical TCM composite was placed in an oven and dried, undergoing stepwise heating of approximately 50° C. overnight, approximately 90° C. for approximately 5 hours, and approximately 140° C. for approximately 1 hour, which is similar to the dehydration temperatures of SrCl₂·6H₂O. The weight percentage of SrCl₂·6H₂O in the composite content was approximately 50%.

A schematic of the TCM bed 205 is shown in FIG. 4; a photograph is shown in FIG. 5. The cylindrical TCM-to-air reactor (i.e., a TCM bed 205) was filled with the TCM composite cylindrical pieces. The temperature profile within the TCM bed 205 was measured with Type K thermocouples (approximately ±0.4% accuracy) in three positions in the axial direction. The volume flow rate of the air was measured and controlled by a Dwyer Series VF flowmeter. The inlet humidity and temperature were controlled using a PermaPure FC Series™ humidifier and an electrical in-line air heater. The inlet and outlet air humidity and temperature were measured using a Rotronic HC2 screw-in probe (temperature accuracy of approximately ±0.1° C. and RH accuracy of approximately ±0.8%). The glass reactor was insulated with an approximately 12-mm-wide layer of neoprene to minimize heat losses. Before each hydration experiment, the TCM composite was dehydrated for approximately 80 minutes at a dehydration temperature of approximately 100° C. with an air volumetric flow rate of approximately 0.0005 m³/s. The TCM then reached thermal equilibrium at approximately room temperature (i.e., approximately 21° C.). The hydration reaction was performed under the inlet conditions of approximately 11.5° C. and approximately 70-75% RH for approximately 14 hours until the inlet and outlet absolute humidity became substantially similar.

In the model, there are two components, the air and the solid. The physical property of air is determined by the dry air, and the solid is determined by the combination of the pure SrCl₂ salt and cement. The hydration state of the SrCl₂-cement composite is defined by the extent of conversion, χ,

$\begin{array}{cc}\frac{\chi =m-m_0}{m_1-m_0}& \mathrm{Eq}.\left(l\right)\end{array}$

where m₀ and m₁ are the initial and final weight of the salt during hydration, respectively. The salt (SrCl₂) is assumed to be in the anhydrous state at χ=0 and the hexahydrate state when χ=1.

The true density of the solid/composite at anhydrous state (SrCl₂), ρ_s,SrCl2, and at hexahydrate state (SrCl₂·6H₂O), ρ_s,SrCl26H2O, are, respectively, defined by,

$\begin{array}{cc}{\rho }_{s,{\mathrm{SrCl}}_2}={\Phi }_{{\mathrm{SrCl}}_2}{\rho }_{\mathrm{salt},{\mathrm{SrCl}}_2}+\left(1-{\Phi }_{{\mathrm{SrCl}}_2}\right){\rho }_{\mathrm{cement}}& \mathrm{Eq}.\left(2\right)\end{array}$ $\begin{array}{c}\mathrm{Eq}.\left(3\right)\end{array}$ ${\rho }_{s,{\mathrm{SrCl}}_2·6H_{2}O}={\Phi }_{{\mathrm{SrCl}}_{2}6H_{2}O}{\rho }_{\mathrm{salt},{\mathrm{SrCl}}_{2}6H_{2}O}+\left(1-{\Phi }_{{\mathrm{SrCl}}_{2}6H_{2}O}\right){\rho }_{\mathrm{cement}}$

where ρ_salt,SrCl2, ρ_{salt,SrCl2·6H2O} and ρ_cement are the true density of pure anhydrous salt, salt hexahydrate and cement, respectively. Φ_SrCl2 and Φ_SrCl2·6H2O are the mass fraction of anhydrous salt and hexahydrate in the composite, respectively.

The apparent density of the pure anhydrous salt, ρ_{salt,app,SrCl2}, the salt hexahydrate, ρ_{salt,app,SrCl2·6H2O}, the anhydrous composite, ρ_s,app,SrCl2, and the composite hexahydrate, ρ_{s,app,SrCl2·6H2O} are defined by

$\begin{array}{cc}{\rho }_{\mathrm{salt},\mathrm{app},{\mathrm{SrCl}}_2}=\frac{m_{\mathrm{salt},{\mathrm{SrCl}}_2}}{V_{\mathrm{reactor}}}& \mathrm{Eq}.\left(4\right)\end{array}$ $\begin{array}{cc}{\rho }_{\mathrm{salt},\mathrm{app},{\mathrm{SrCl}}_2·6H_{2}O}=\frac{m_{\mathrm{salt},{\mathrm{SrCl}}_2·6H_{2}O}}{V_{\mathrm{reactor}}}& \mathrm{Eq}.\left(5\right)\end{array}$ $\begin{array}{cc}{\rho }_{s,\mathrm{app},{\mathrm{SrCl}}_2}=\frac{m_{s,{\mathrm{SrCl}}_2}}{V_{\mathrm{reactor}}}& \mathrm{Eq}.\left(6\right)\end{array}$ $\begin{array}{cc}{\rho }_{s,\mathrm{app},{\mathrm{SrCl}}_2·6H_{2}O}=\frac{m_{s,{\mathrm{SrCl}}_2·6H_{2}O}}{V_{\mathrm{reactor}}}& \mathrm{Eq}.\left(7\right)\end{array}$

where m_salt,SrCl, m_{salt,SrCl2·6H2O}, m_s,SrCl2 and m_{s,SrCl2·6H2O} are the mass of pure anhydrous salt, the salt hexahydrate, the composite at anhydrous state, and the composite at hexahydrate in the TCM bed 205, respectively. V_reactor is the volume of the reactor (i.e., the TCM bed 205).

The instantaneous porosity of the TCM bed 205, e, is a function of χ and is assumed to be based on a linear relationship between the porosity of the composite at anhydrous state and

$\begin{array}{cc}\epsilon =\chi {\epsilon }_{{\mathrm{SrCl}}_2}+\left(1-\chi \right){\epsilon }_{{\mathrm{SrCl}}_2·6H_{2}0}& \mathrm{Eq}.\left(8\right)\end{array}$

where the porosity of the composite at anhydrous state, ∈_SrCl2, and hexahydrate, ε_SrCl2·6H2O respectively, are defined by

$\begin{array}{cc}{\epsilon }_{{\mathrm{SrCl}}_2}=1-\frac{{\rho }_{s,\mathrm{app},{\mathrm{SrCl}}_2}}{{\rho }_{s,{\mathrm{SrCl}}_2}}& \mathrm{Eq}.\left(9\right)\end{array}$ $\begin{array}{cc}{\epsilon }_{{\mathrm{SrCl}}_2·6H_{2}O}=1-\frac{{\rho }_{s,\mathrm{app},{\mathrm{SrCl}}_2·6H_{2}O}}{{\rho }_{s,{\mathrm{SrCl}}_2·6H_{2}O}}& \mathrm{Eq}.\left(10\right)\end{array}$

The hydration rate of the SrCl₂-cement composite is dominated by three variables: the temperature of the salt, T_s; the vapor pressure of the moist air, P_w; and the extent of conversion, χ·During hydration, χ increases from the monohydrate phase (χ=1/6) to the hexahydrate phase (χ=1). The change of χ in a cylindrical shape composite based on the equivalent diameter for a sphere including vapor diffusion follows the relation below:

$\begin{array}{cc}\frac{d\chi }{\mathrm{dt}}=\frac{\left(\frac{P_w}{P_{eq}}-1\right)}{\frac{R_s^2}{3D_e}\left({\left(1-\chi \right)}^{-\frac{1}{3}}-1\right)+\frac{\alpha R_s}{3}\frac{{\left(1-\chi \right)}^{-\frac{2}{3}}}{k{\left(\frac{P_w}{P_{eq}}-1\right)}^{n_0-1}}}& \mathrm{Eq}.\left(11\right)\end{array}$

where t is time, R_s is the radius of the solid, D_e is the effective diffusivity of water vapor, a is the surface area to volume ratio, ρ_eq is the equilibrium pressure of the hydrate salt, and k is the reaction rate, and is defined by

$\begin{array}{cc}k\left(T_s\right)=A_0{e}^{-\frac{E_a}{{\mathrm{RT}}_s}}& \mathrm{Eq}.\left(12\right)\end{array}$

where A₀ is the pre-exponential Arrhenius factor, E_a is the Arrhenius activation energy, and R is the air constant. The equilibrium pressure of the water vapor in equilibrium with the hydrated salt is fitted as a function of the extent of the conversion and the temperature of SrCl₂.

$\begin{array}{cc}{\log }_{10}\left(P_{eq}\right)=\{\begin{array}{cc}10.67\ln \left(T_s\right)-60.06& 0\le \chi <\frac{1}{6}\\ 9.144\ln \left(T_s\right)-49.68& \frac{1}{6}\le \chi <\frac{1}{3}\\ 9.31\ln \left(T_s\right)-50.02& \frac{1}{3}\le \chi <1\end{array}& \mathrm{Eq}.\left(13\right)\end{array}$

During hydration of the TCM bed 205, the increase in mass density of the salt leads to a decrease in the mass density of the vapor,

$\begin{array}{cc}{\rho }_a\epsilon \frac{\partial {\omega }_g}{\partial t}+{\rho }_{a}u\frac{\partial {\omega }_g}{\partial x}=-{\rho }_{\mathrm{salt},\mathrm{app}}\frac{d\chi }{\mathrm{dt}}\frac{M_{H_{2}O}}{M_{\mathrm{salt}}}𝓏& \mathrm{Eq}.\left(14\right)\end{array}$

The left-hand side of Eq. (14) denotes the moisture change in the moist air, where ρ_a is the density of the air, e is the porosity of the reactive bed, ω_a is the humidity ratio of the air, and u is the velocity of the air. The right-hand side of Eq. (14) shows that the moisture absorption by the salt and the vapor diffusion are included in the reaction term, where ρ_salt,app is the apparent density of the pure salt, M_H20 is the molar mass of water, M_salt is the molar mass of the salt, and z is the stoichiometric coefficient of water.

Two energy equations are applied to describe the heat transfer between the air and the solid in the TCM bed 205. The governing equation for the air is,

$\begin{array}{c}\mathrm{Eq}.\left(15\right)\end{array}$ ${\rho }_a{C}_{p,w}\epsilon \frac{\partial T_a}{\partial t}+{\rho }_a{C}_{p,w}u\frac{\partial T_a}{\partial x}=h_v\left(T_s-T_a\right)+\frac{h_{\mathrm{diss}}{P}_{\mathrm{reactor}}}{A_{\mathrm{reactor}}}\left(T_a-T_{env}\right)$

where T_a is temperature of the air, T_env is temperature of the environment, h_diss is convective heat dissipation coefficient of the environment, ρ_reactor is the perimeter of the cross-sectional surface of the TCM bed 205, A_reactor is the lateral surface area of the TCM bed 205, and C_p,m is the specific heat capacity of moist air,

$\begin{array}{cc}{C}_{p,m}=C_{p,a}+\omega C_{p,v}& \mathrm{Eq}.\left(16\right)\end{array}$

where C_p,a is the specific heat capacity of dry air, and C_p,v is the specific heat capacity of water vapor. h_v is the convective heat transfer coefficient between air and solid and is calculated by,

$\begin{array}{cc}{h}_v=6\left(1-\epsilon \right)k_a\frac{2+1.1{\mathrm{Re}}^{0.6}{\mathrm{Pr}}^{1/3}}{D_p^2}& \mathrm{Eq}.\left(17\right)\end{array}$

where k_a is thermal conductivity of the air, D_p is the diameter of the solid particle, Re is the Reynold number of the air, and Pr is the Prandtl number of the air.

The governing equation for the solid is,

$\begin{array}{c}\mathrm{Eq}.\left(18\right)\end{array}$ ${\rho }_{s,\mathrm{app}}{C}_{p,s}\frac{\partial T_S}{\partial t}={\kappa }_s\frac{{\partial }^2{T}_S}{\partial x^2}-{\rho }_{\mathrm{salt},\mathrm{app}}\frac{d\chi }{\mathrm{dt}}\frac{M_{H_{2}O}}{M_{\mathrm{salt}}}z\Delta H+h_v\left(T_s-T_a\right)$

where ΔH is reaction heat, κ_s is thermal conductivity of the solid, C_p,s is the specific heat capacity of the solid, and T_s is the temperature of the solid.

The governing equations are solved in an explicit finite difference form in a Python environment. The first-order upwind scheme is applied to discretize spatial terms. The independent study of the timestep, Δt, and mesh size, Δx, (or grid number, N_x,) is also conducted with Δt=0.02, 0.01 and 0.005, and Δx=0.0297, 0.0148 and 0.0074 m (N_x=10, 20 and 40). The results will be shown in the following section on model validation, which shows that it is accurate enough to choose Δx=0.0148 m (N_x=20) to discretize the computational domain, and Δt=0.01 s for timestep. The thermophysical properties of moist air are calculated by PsychroLib.

For building energy storage purposes, a TCM bed 205 may be installed in a heating, ventilating, and air-conditioning (HVAC) system. The humidity level of the inlet air stream strongly affects the thermal performance. In some embodiments, the system 200 is designed to prevent the TCM bed 205 from dehumidifying the indoor space 250 and provide a sufficient humidity level during hydration.

To use a TCM bed 205 for space heating, the local air conditions in different climate zones are needed to set the inlet conditions for the TCM bed 205 during the heating season. The heating loads and the indoor and outdoor air conditions of a typical single-family house are simulated by EnergyPlus™ in different climate zones: warm-humid (Atlanta, Georgia), mixed-marine (Seattle, Washington), cold-humid (Minneapolis, Minnesota) and mixed-humid (New York City, New York). The indoor air stream needs to be heated when the indoor heating load is not zero more than 2 hours in a day.

The energy density, Q_v, is the time integration of the power density, {dot over (Q)}_v, of the TCM bed 205, which can be calculated by the air-side temperature change,

$\begin{array}{cc}{Q}_v=\underset{t_0}{\overset{t_1}{\int }}{\stackrel{.}{Q}}_v\mathrm{dt}=\underset{t_0}{\overset{t_1}{\int }}\frac{{\dot{m}}_a{C}_{p,m}\left(T_{a,\mathrm{out}}\left(t\right)-T_{a,\mathrm{in}}\right)}{V_{\mathrm{reactor}}}\mathrm{dt}& \mathrm{Eq}.\left(19\right)\end{array}$

where t₀ and t₁ are the initial and final time of the hydration process, respectively, and {dot over (m)}_a is the mass flow rate of process air in the TCM bed 205.

As shown in FIG. 6A the model has good agreement with the measured air outlet temperature. In addition, the results among different timesteps show negligible difference for the air outlet temperature. In FIG. 6B, the air outlet temperature is compared between the experimental data and the numerical results with different mesh size. As indicated by the inset plot focusing on the early stage of the hydration, there is good convergence once the grid number exceeds 20. The parameters used in the validation are listed in Table 1, and the density details of the pure SrCl₂ and the composite at different χ values are listed in Table 2. In addition to the current experimental result with dehydration temperature at 100° C., other experimental results with different dehydration temperatures are shown in FIGS. 12A-D to provide credibility of the model with different initial conditions.

TABLE 1
Parameter values used in the simulation
The thermodynamic properties of moist air (at Patm = 1 atm)
Inlet air dry bulb temperature, Ta, in (° C.) 11.5
Inlet air RH, RHa, in (%)        75%
Specific heat of dry air, Cp, a (J/(kg · K)) 1009
Thermal conductivity of aig, ka (W/(m · K) 0.0321
Velocity of process air, u (m/s) 0.3288
Air constant, R (J/(mol · K))    8.314
Reaction enthalpy, ΔH (J/kgwater) 3175000
The thermodynamic properties of the solid
Density of cement, ρs, cement (kg/(m3)) 2251
Initial temperature, Ts, 0 (° C.) 11.5
Specific heat of solid, Cp, s (J/(kg · K)) 747
Thermal conductivity of solid, κs (W/(m · K)) 0.704
Mass fraction of salt, Φ         0.518
Reaction and transport parameters
Pre-exponential Arrhenius factor, A0, 0-6 1.3 × 107
Arrhenius activation energy, Ea, 0-6 (J/mol) 58700
Diameter of solid particle, Dp (m) 0.007
Effective diffusivity of water vapor, De (m2/s) 1.65 × 10−11
Heat dissipation coefficient, hdiss (W/m2K) 1.3
Environment temperature, Tenv (° C.) 21
Surface area to volume ratio, α (m2/m3) 858.7
Geometry of the reactor (i.e., the TCM bed)
Height of reactor, h (m)         0.297
Radius of reactor, r (m)         0.022

TABLE 2
Density of pure SrCl2 and the composite at different χ
State of	True density (kg/m3)	Apparent density (kg/m3)
SrCl2	χ	Pure salt	Composite	Pure salt	Composite
SrCl2	0	3096.93	2771.58	218.56	560.12
SrCl2•H2O	⅙	2921.29	2680.56	243.37	584.94
SrCl2•2H2O	⅓	2672	2551.36	268.19	609.76
SrCl2•6H2O	1	1956.49	2180.54	367.45	709.02

The humidity input for the TCM bed 205 is one of the most important factors affecting the power density of the TCM bed 205 because the vapor pressure difference between the air and the salt provides the driving force for the hydration reaction. To study the effects of air inlet humidity on thermal performance, the humidity-temperature phase diagram of the SrCl₂-H₂O system was used to determine the lowest RH corresponding to each hydrate of SrCl₂ at 21° C.: RH=8.1% for dihydrate, RH=32.4% for hexahydrate, and RH=68.2% for deliquescence. FIG. 4 shows the results during the hydration process based on four different inlet RH values (15%, 30%, 45%, and 60%). As illustrated in FIG. 7A, the TCM bed 205 with higher RH inputs (45% RH and 60% RH) has higher outlet air temperatures. Both curves for the hexahydrate of SrCl₂ (45% RH and 60% RH) reach a peak at the beginning of the hydration process, followed by a rapid decline and then a slow decay. The outlet air temperatures become lower with lower inlet RH (15% RH and 30% RH). The curve with 30% RH has an initial hydration process similar to the higher RH case but has a single decay for −12 hours before the cessation of the hydration process. The curve for 15% RH outputs air temperature at 21° C. for the whole hydration process, which implies that only a small amount of the salt is hydrated at such low RH. A new set of hydration coefficients is extracted based on experiments because the hydration from monohydrate to dihydrate has a different hydration reaction coefficient from monohydrate to hexahydrate. The hydration reaction coefficient from anhydrous SrCl₂ to dihydrate is estimated from experimental data.

The different trends of the curves are also indicated by their energy output in FIG. 7B. The hydration rates of the salts are faster at the beginning and become slower for cases with higher RH (approximately 45% RH and approximately 60% RH), while the rates for lower RH remain slow. For inlet air with RH of approximately 60%, the extent of the conversion of the salt in the TCM bed 205 is approximately 0.64 at the end of an approximately 12-hour hydration process, with an energy density of approximately 61 kWh/m³. When the inlet air RH is approximately 45%, salt is converted to approximately 49% of the hexahydrate during the approximately 12-hour hydration period, with approximately 41.9 kWh/m³ energy density. The case with approximately 30% RH provides energy to the room with approximately 14.7 kWh/m³. The case with approximately 15% RH has the lowest extent of conversion and only provides approximately 3.5 kWh/m³ heat output. The lower inlet humidity (less than approximately 32% RH) essentially constrains the possible energy density that is achievable. A longer hydration period would result in a fully hydrated TCM bed 205 (χ=1) in the current design for the approximately 45% and approximately 60% RH cases (approximately 131.32 kWh/m³).

A similar trend of the effect of inlet air RH on spatial averaging of the extent of conversion can be found in FIG. 7C, where low RH curves peak at χ=0.33 and high RH curves peak at χ=1. In addition, there is a large discrepancy in χ along the TCM bed 205, with the inlet and outlet reaching approximately 0.55 and approximately 0.73, respectively, after approximately 12 hours of hydration with approximately 60% RH air (FIG. 7D).

The effect of air flow rate on the thermal performance of the TCM bed 205 with four volumetric air flow rates (0.00025, 0.0005, 0.001, and 0.002 m³/s) was studied. The effects with inlet air stream RH at approximately 30% and approximately 60% are illustrated in FIGS. 8A-D. A higher air flow rate accelerates the hydration process and increases the power density of the TCM bed 205. However, the effects of higher flow rate on hydration rate become weaker after the air flow rate is greater than approximately 0.001 m³/s. With the inlet air at approximately 30% RH, increasing the volumetric flow shortens the hydration process, as shown in FIG. 8A. This result is consistent with the reaction rate profile of different volumetric flow rates in FIG. 8B.

As illustrated in FIG. 8C, the outlet air temperature with an air flow rate of approximately 0.002 m³/s is approximately 4° C. less than with an air flow rate of approximately 0.00025 m³/s during the quasi-steady output period. The TCM bed 205 with higher air stream flow can reach the quasi-steady state much more rapidly. Meanwhile, more stored thermal energy is extracted with the higher air flow rate in the same time period. The output heat can reach approximately 71.8 kWh/m³ with an air flow rate of approximately 0.002 m³/s, but reaches approximately 68, approximately 61, and approximately 49.7 kWh/m³ with an air flow rate of approximately 0.001, approximately 0.005, and approximately 0.00025 m³/s, respectively. However, the accelerating effect from the air flow rate on the hydration reaction reduces as the flow rate increases higher than approximately 0.001 m³/s. As seen in FIG. 8D, the difference of the reaction rate between cases approximately 0.001 and approximately 0.002 m³/s is much smaller than the other cases.

The thermal performance of the TCM bed 205 is also affected by moisture transport in the SrCl₂-cement composite (i.e., the TCM), and it is highly related to the cylinder size according to Eq. (11). As shown in FIGS. 9A-B, the hydration process significantly accelerates when the radius of the cylinder decreases from approximately 3.5 mm to approximately 1 mm. However, the size effect on the hydration process becomes much weaker once the radius keeps shrinking smaller than approximately 1 mm. This effect becomes less dramatic because the reaction is more controlled by chemical kinetics.

The thermal performance of a TCM energy storage system 200 in different climate zones was analyzed. The system 200 was designed to prevent the TCM bed 205 from dehumidifying the indoor space 250 during hydration. Realistic weather data was used to estimate the applicable energy and LCOS in a TCM system 200 in different climate zones. The heating loads are determined from simulation conducted by EnergyPlus on a typical single-family house in different climate zones: warm-humid (Atlanta, Georgia), mixed-marine (Seattle, Washington), cold-humid (Minneapolis, Minnesota), and mixed-humid (New York City, New York).

TABLE 3
Percentages of heating hours that
SrCl2 spends at each hydration phase
State of	Heat supply hour percentages (%)
SrCl2	Atlanta	Seattle	Minneapolis	New York City
Monohydrate	0	0	10.2	0
Dihydrate	68.0	39.6	78.5	75.5
Hexahydrate	32.0	60.4	11.3	24.5
Deliquescence	0	0	0	0

Using the probability distribution, estimate performance of the SrCl₂-based TCM bed 205 in different climate zones can be estimated by assuming that (1) the indoor RH is stable during one hydration process and (2) the salt in the TCM bed 205 is fully regenerated to monohydrate before the next hydration process. The effective energy densities of the TCM in different climate zones are calculated based on the probability density of the inlet air RH, f(RH), and the energy density of the TCM bed 205 at each inlet air RH, Q_v(RH),

$\begin{array}{cc}{Q}_{v,\mathrm{eff}}=\underset{\mathrm{RH}=0\%}{\overset{\mathrm{RH}=100\%}{\int }}f\left(\mathrm{RH}\right)Q_v\left(\mathrm{RH}\right)\mathrm{dRH}& \mathrm{Eq}.\left(20\right)\end{array}$

The pure SrCl₂ has a theoretical storage density as high as 699 kWh/m³ for the full hydration from anhydrous salt to hexahydrate. However, the salt is seldom dehydrated to its anhydrous state in practice due to the required high temperature for regeneration air (greater than approximately 100° C.). A hydration process initiated from monohydrate or dihydrate has less potential energy density than one initiated from anhydrous salt.

FIG. 10 shows the achievable energy densities of an SrCl₂-based TCM bed 205 in different scenarios for a reaction from monohydrate to hexahydrate. For this reaction, pure monohydrate SrCl₂ has a theoretical storage density of approximately 583 kWh/m³. This value is remarkably higher than typical values in sensible and solid-liquid latent heat. The energy density of the monohydrate substantially drops once it is incorporated into a composite and is in the TCM bed 205. The SrCl₂-cement composite's energy density is reduced by roughly approximately 50%, but its cyclability is improved by preventing agglomeration of the salt (case 2 in FIG. 10). When the composite is put in the TCM bed 205, the effective porosity of the TCM bed 205 reduces the composite's energy density to approximately 131 kWh/m³, but this is still higher than in a corresponding TCM storage system (case 3 in FIG. 10).

As previously discussed, the energy density of a TCM bed 205 is affected by the inlet air conditions. The inlet air RH needs to be higher than the 2-6 transition line in the SrCl₂ phase diagram to ensure that the salt can be converted to hexahydrate. High inlet air RH converts most salt to hexahydrate during the 19-hour hydration process, as indicated by cases 4 and 5 in FIG. 10. Otherwise, the stored heat in the salt is not fully exploited for lower RH of approximately 30% (case 6 of FIG. 10). In addition, more energy can be extracted by using smaller amounts of the SrCl₂-cement composite during the hydration process. The solid filled bars show that almost approximately 20% more heat is extracted with incoming air RH at approximately 45% and approximately 60%. However, this is not the case with inlet air RH at approximately 30%, due to the cessation of conversion to dihydrate.

Based on Eq. (20), the energy density of a TCM bed 205 in different cities is illustrated by cases 7-10 in FIG. 10. This result is highly correlated to the probability distribution of the indoor air RH in different cities. Environments where SrCl₂ spends more time in the hexahydrate phase will have higher effective energy density. This conclusion can guide future TCM designs in different climate zones.

Other good candidates for a salt-hydrate-based TCM bed 205 are SrBr₂ and CaCl₂, because they require a lower vapor pressure than SrCl₂ for full hydration. For example, the monohydrate of SrBr₂ has an equilibrium vapor pressure similar to that of the monohydrate of SrCl₂, but it can be converted to the hexahydrate in the absence of an inter-hydrated state, which means that the monohydrate SrBr₂ can be converted to the hexahydrate for an air RH of approximately 32.4% at approximately 21° C. However, SrBr₂ and CaCl₂ deliquesce at a lower RH, meaning the TCM bed 205 and TCM composite must be carefully designed to eliminate leakage of salt ions from the TCM bed 205 when in the aqueous solution state.

In some embodiments, the inlet air vapor pressure (i.e., indoor RH) needs to be higher than the equilibrium vapor pressure of the salt hydrate. Especially for hydrated salts that have multiple states, e.g., SrCl₂ and MgCl₂, the inlet air vapor pressure should be higher than the salt hydrates' equilibrium vapor pressure by a maximum mole of water. The inlet air with higher vapor pressure (typically meaning a higher RH), is encouraged for the TCM bed 205 once it is less than the deliquescence value. The potential energy in a TCM bed 205 is seldom fully utilized by inlet air with low RH during the heating season.

The usable energy density of the TCM bed 205 was calculated by reviewing indoor conditions in four climate zones. A TCM bed 205 in the mixed-marine climate zone has the best performance in our analysis due to a high portion (approximately 60%) of heat supply time with the indoor air RH above approximately 32.4%. The TCM bed 205 in the cold-humid climate zone showed the worst performance because the duration of the indoor air RH is lower than approximately 32.4% for most of the annual heat supply period. Once the indoor air RH is lower than the dihydrate to hexahydrate (2-6) transition line in the SrCl₂ phase diagram it confines the performance of the SrCl₂-based TCM bed 205 because it prevents the conversion of SrCl₂ from dihydrate to hexahydrate. This might be solved by substituting SrCl₂ with SrBr₂ or CaCl₂ in the TCM bed 205 because of the low equilibrium pressure of the hexahydrates for both salts.

In general, deployment in locations with more moisture available in the air due to higher RH (i.e., Seattle versus Minneapolis) results in higher thermal performance of the TCM bed 205. LCOS is also determined by the number of hours in the heat supply seasons. Manufacturing TCM beds 205 for multifamily buildings has obvious advantages (e.g., lower costs) over doing the same for a single-family house.

In some embodiments of the present disclosure, the exhaust air (i.e., first air stream 210) is used as process air for the TCM, then for heating the outdoor air (i.e., the second air stream 220) in the heat exchanger 235. The heat exchanger 235 may be at least one of a shell and tube heat exchanger, plate heat exchanger, finned tube heat exchanger, gasketed plate heat exchanger, double pipe heat exchanger, plate and frame heat exchanger, regenerative heat exchanger, welded plate heat exchanger, air exchanger, or a combination thereof.

In some embodiments of the present disclosure, the exhaust air (i.e., the first air stream 210) is used to drive the TCM bed 205, which then heats incoming ventilation air (i.e., second air stream 220) with an air-to-air heat exchanger 235. This keeps the indoor humidity level the same as if the TCM bed 205 were not installed. The TCM bed's 205 performance can be maintained at a relatively high level due to the sufficient water vapor from the indoor space that is being exhausted outside (via exhausted first air stream 230). The ventilation air (i.e., second air stream 220) is heated sensibly, in many cases above the indoor temperature, reducing energy required by the furnace or heat pump to maintain the temperature of the indoor space 250.

As shown in FIGS. 12A-D, the current model still works well when it is used to predict the outlet air temperature during the hydration process after the TCM has been dehydrated at different temperatures.

FIG. 13 illustrates a substantially regenerative two fluid TCM system 300, according to some aspects of the present disclosure. The system 300 may include a first channel 305 configured to receive a mixed air stream 310, a second channel 335 containing a sorbent material 330 or TCM, and an air duct 350 connecting the first channel 305 to the second channel 335. The mixed air stream 310 may be a combination of the first air stream 210 (i.e., air from the indoor space 250) and the second air stream 220 (i.e., air from an external source). The air duct 350 may direct 110 a first portion of the mixed air stream 315 to the second channel 335. The air duct 350 may contain a vent (not shown), which may release a second portion of the mixed air stream 320 to the indoor space 250.

In some embodiments, the two-fluid TCM system 300 shown in FIG. 13 may be used where an air stream (i.e., the mixed air stream 310) is to be heated and humidified indirectly from a TCM reaction. This may be done where the ventilation air stream (i.e., the second air stream 220) would be heated and humidified by the outgoing “stale” indoor air stream (i.e., the first air stream 210).

But it may also be done as a regenerative, or recuperative, heat and mass exchanger, as shown in FIG. 13. In the example shown in FIG. 13, a portion of the air stream that has already been heated indirectly by the TCM (i.e., the first portion of the mixed air stream 315) may be used to drive the hydration reaction (i.e., the charging and discharging modes). The mixed air stream 310 may be heated through conduction from the TCM (i.e., the sorbent material 330) across a separator plate 345. A water film 325 may also be provided on the walls of the first channel 305, which may humidify the mixed air stream 310 to the required level. The air stream delivered to the building (i.e., the second portion of the mixed air stream 320) may then be substantially humidity neutral, so it is not drying or humidifying the building.

In the example shown in FIG. 13, approximately 40% of the TCM energy may be used to heat the first air stream 210, but it may do it at a higher temperature lift (i.e., a supply temperature of approximately 30° C. versus approximately 24° C.). It may also heat a second air stream 220 that is provided to the building. Adding the sensible heat needed for this level of ventilation air stream (i.e., the second air stream 220) heating increases the TCM utilization to approximately 67% and adding both the sensible heat and the latent heat done to the ventilation air stream (i.e., second air stream 220) increases the TCM utilization to approximately 81%.

EXAMPLES

Example 1. A method comprising:

• • contacting a thermochemical material (TCM) with a first air stream resulting in a dehumidified and heated first air stream;
  • directing the dehumidified and heated first air stream to interact with a second air stream; and
  • releasing a heated second air stream into an indoor space; wherein:
  • the first air stream enters the TCM from the indoor space, and
  • the directing causes the second air stream to be heated resulting in the heated second air stream.

Example 2. The method of Example 1, wherein:

• • the contacting comprises:
  • receiving the first air stream; and
  • removing a humidity from the first air stream resulting in the dehumidified and heated first air stream; wherein:
    • the removing results in the humidity being absorbed by the TCM, and
    • the contacting is performed in a TCM bed.

Example 3. The method of Example 1, wherein:

• • the directing comprises:
  • receiving the dehumidified and heated first air stream and the second air stream; and
  • transferring a heat from the dehumidified and heated first air stream to the second air stream; wherein:
    • the transferring results in the dehumidified and heated first air stream becoming an exhausted first air stream, and
    • the transferring results in the second air stream becoming the heated second air stream.

Example 4. The method of Example 3, wherein:

• • the directing is performed in a heat exchanger.

Example 5. The method of Example 4, wherein:

• • the second air stream enters the heat exchanger from an external ambient.

Example 6. The method of Example 1, wherein:

• • the TCM comprises a salt hydrate.

Example 7. The method of Example 8, wherein:

• • the salt hydrate comprises at least one of magnesium chloride (MgCl₂), strontium bromide (SrBr₂), calcium hydroxide (Ca(OH)₂), potassium carbonate (K₂CO₃), lithium hydroxide (LiOH), or strontium chloride (SrCl₂).

Example 8. A system comprising:

• • a thermochemical material (TCM) bed configured to receive a first air stream and to release a heated and dehumidified first air stream; and
  • a heat exchanger comprising:
  • a first inlet configured to receive the heated and dehumidified first air stream;
  • a second inlet configured to receive a second air stream;
  • a first outlet configured to release a heated second air stream into an indoor space; and
  • a second outlet configured to release an exhausted first air stream; wherein:
    • the TCM bed comprises a TCM,
    • the TCM bed is configured to absorb a humidity from the first air stream resulting in the dehumidified and heated first air stream being released from the TCM bed,
    • the heat exchanger is configured to transfer heat from the dehumidified and heated air stream to the second air stream, resulting in the heated second air stream being released via the first outlet and the exhausted first air stream being released via the second outlet.

Example 9. The system of Example 8, wherein:

• • the TCM comprises a salt hydrate.

Example 10. The system of Example 9, wherein:

• • the salt hydrate comprises at least one of magnesium chloride (MgCl₂), strontium bromide (SrBr₂), calcium hydroxide (Ca(OH)₂), potassium carbonate (K₂CO₃), lithium hydroxide (LiOH), or strontium chloride (SrCl₂).

Example 11. The system of Example 8, wherein:

• • the second inlet and the second outlet are substantially co-located.

Example 12. A method comprising:

• • contacting a mixed air stream with a sorbent material in a first channel;
  • directing a first portion of the mixed air stream to interact with the sorbent material in a second channel; and
  • releasing a second portion of the mixed air stream into an indoor space; wherein:
    • the directing results in a humidity from the second portion of the mixed air stream to the sorbent material.

Example 13. The method of Example 12, further comprising:

• • combining a first air stream and a second air stream to form a mixed air stream; wherein: the combining occurs prior to the contacting.

Example 14. The method of Example 13, wherein:

• • the first air stream is sourced from the indoor space.

Example 15. The method of Example 13, wherein:

• • the second air stream is sourced from an external ambient.

Example 16. The method of Example 12, wherein:

• • the contacting comprises:
    • receiving a first air stream and a second air stream into the first channel; and
    • placing a sorbent in thermodynamic communication with the mixed air stream; wherein:
      • the mixed air stream comprises the first air stream and the second air stream.

Example 17. The method of Example 12, wherein:

• • the contacting further comprises contacting the mixed air stream with a water film in the first channel.

Example 18. The method of Example 12, wherein:

• • the directing comprising:
    • receiving the first portion of the mixed air stream into the second channel,
    • contacting the sorbent material with the first portion of the mixed air stream in the second channel resulting in an exhausted mixed air stream; and
    • releasing the exhausted mixed air stream to an external ambient.

Example 19. The method of Example 12, wherein:

• • the first channel and the second channel are separated by a plate.

Example 20. The method of Example 19, wherein:

• • the plate is substantially permeable by heat and water.

Example 21. A system comprising:

• • a first channel configured to receive a mixed air stream;
  • a second channel containing a sorbent material; and
  • an air duct configured to connect the first channel and the second channel and having a vent; wherein:
    • the mixed air stream comprises a first air stream and a second air stream,
    • the sorbent material is in thermodynamic communication with the mixed air stream,
    • the air duct is configured to direct a first portion of the mixed air stream to the second channel, and
    • the vent is configured to release a second portion of the mixed air stream to an indoor space.

Example 22. The system of Example 21, wherein:

• • the first channel comprises a water film.

Example 23. The system of Example 21, wherein:

• • the first channel and the second channel are separated by a plate.

Example 24. The system of Example 23, wherein:

• • the plate is substantially permeable by heat and water.

Example 25. The system of Example 21, wherein:

• • the first air stream is sourced from the indoor space, and
  • the second air stream is sourced form an external ambient.

The foregoing discussion and examples have been presented for purposes of illustration and description. The foregoing is not intended to limit the aspects, embodiments, or configurations to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the aspects, embodiments, or configurations are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the aspects, embodiments, or configurations may be combined in alternate aspects, embodiments, or configurations other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the aspects, embodiments, or configurations require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. While certain aspects of conventional technology have been discussed to facilitate disclosure of some embodiments of the present invention, the Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects discussed herein. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate aspect, embodiment, or configuration.

Claims

1. A method comprising: contacting a thermochemical material (TCM) with a first air stream resulting in a dehumidified and heated first air stream;directing the dehumidified and heated first air stream to interact with a second air stream; andreleasing a heated second air stream into an indoor space; wherein:the first air stream enters the TCM from the indoor space, andthe directing causes the second air stream to be heated resulting in the heated second air stream.

2. The method of claim 1, wherein: the contacting comprises: receiving the first air stream; andremoving a humidity from the first air stream resulting in the dehumidified and heated first air stream; wherein:the removing results in the humidity being absorbed by the TCM, andthe contacting is performed in a TCM bed.

3. The method of claim 1, wherein: the directing comprises: receiving the dehumidified and heated first air stream and the second air stream; andtransferring a heat from the dehumidified and heated first air stream to the second air stream; wherein:the transferring results in the dehumidified and heated first air stream becoming an exhausted first air stream, andthe transferring results in the second air stream becoming the heated second air stream.

4. The method of claim 3, wherein: the directing is performed in a heat exchanger.

5. The method of claim 4, wherein: the second air stream enters the heat exchanger from an external ambient.

6. The method of claim 1, wherein: the TCM comprises a salt hydrate.

7. The method of claim 8, wherein: the salt hydrate comprises at least one of magnesium chloride (MgCl2), strontium bromide (SrBr2), calcium hydroxide (Ca(OH)2), potassium carbonate (K2CO3), lithium hydroxide (LiOH), or strontium chloride (SrCl2).

8. A system comprising: a thermochemical material (TCM) bed configured to receive a first air stream and to release a heated and dehumidified first air stream; anda heat exchanger comprising: a first inlet configured to receive the heated and dehumidified first air stream;a second inlet configured to receive a second air stream;a first outlet configured to release a heated second air stream into an indoor space; anda second outlet configured to release an exhausted first air stream; wherein:the TCM bed comprises a TCM,the TCM bed is configured to absorb a humidity from the first air stream resulting in the dehumidified and heated first air stream being released from the TCM bed,the heat exchanger is configured to transfer heat from the dehumidified and heated air stream to the second air stream, resulting in the heated second air stream being released via the first outlet and the exhausted first air stream being released via the second outlet.

9. The system of claim 8, wherein: the TCM comprises a salt hydrate.

10. The system of claim 9, wherein: the salt hydrate comprises at least one of magnesium chloride (MgCl2), strontium bromide (SrBr2), calcium hydroxide (Ca(OH)2), potassium carbonate (K2CO3), lithium hydroxide (LiOH), or strontium chloride (SrCl2).

11. The system of claim 8, wherein: the second inlet and the second outlet are substantially co-located.

12. A method comprising: contacting a mixed air stream with a sorbent material in a first channel;directing a first portion of the mixed air stream to interact with the sorbent material in a second channel; andreleasing a second portion of the mixed air stream into an indoor space;wherein:the directing results in a humidity from the second portion of the mixed air stream to the sorbent material.

13. The method of claim 12, further comprising: combining a first air stream and a second air stream to form a mixed air stream; wherein:the combining occurs prior to the contacting.

14. The method of claim 13, wherein: the first air stream is sourced from the indoor space.

15. The method of claim 13, wherein: the second air stream is sourced from an external ambient.

16. The method of claim 12, wherein: the contacting comprises: receiving a first air stream and a second air stream into the first channel; andplacing a sorbent in thermodynamic communication with the mixed air stream; wherein:the mixed air stream comprises the first air stream and the second air stream.

17. The method of claim 12, wherein: the contacting further comprises contacting the mixed air stream with a water film in the first channel.

18. The method of claim 12, wherein: the directing comprising: receiving the first portion of the mixed air stream into the second channel,contacting the sorbent material with the first portion of the mixed air stream in the second channel resulting in an exhausted mixed air stream; andreleasing the exhausted mixed air stream to an external ambient.

19. The method of claim 12, wherein: the first channel and the second channel are separated by a plate.

20. The method of claim 19, wherein: the plate is substantially permeable by heat and water.