BACKGROUND Field of Invention This invention relates to heating, cooling, and energy storage systems. More specifically, this invention relates to apparatuses and processes that use pressure swing adsorption and desorption to achieve heating, cooling, and energy storage functions such as are needed for HVAC, refrigeration, and other heating and cooling applications.
Description of Prior Invention Adsorption is emerging as an important process for separating fluids, heating, cooling, molecule storage, and energy storage. The present invention comprises a pressure swing adsorption (PSA) (so called “heatless” adsorption) cycle that provides heating, cooling and energy storage. The invention uses an adsorbate fluid which is pressure swing adsorbed releasing heat, and then pressure swing desorbed absorbing heat. The released heat is applied to a heating application such as heating a building and the absorbed heat is absorbed from an application to be cooled such as a building or a refrigerator. Also, the adsorption and the desorption processes can be selectively separated in time such that a pressurized sorption bed provides a stored capacity to cool which is utilized by simply opening a valve; similarly, a depressurized sorption bed provides a stored capacity to heat which is utilized simply by opening a valve. For about 100 years, prior art temperature swing adsorption (TSA) and absorption have been utilized for cooling systems such as adsorption chillers and ammonia absorption chillers. Such systems have the advantage of being relatively simple with few moving parts and being powered by burning fuel, or solar thermal energy, or waste heat energy but have the disadvantage of requiring excessive heat input for desorption and therefore have a low coefficient of performance (COP) efficiency. An example of a water based temperature swing adsorption system including a storage aspect is described in an undated paper “Sorbtion Materials for Application in Solar Heat Energy Storage” by P. Gantenbein et al of the Institute for Solartechnik in Switzerland. Another example of a temperature swing adsorption system is described in U.S. Pat. No. 7,497,089 by Kakiuchi et al. which relies upon an adsorption process driven by a heat input and a system that requires an evaporator and a condenser in addition to the sorption beds. The present invention replaces the heat input “temperature swing adsorption” and “temperature swing absorption” driven compression and phase change effect with mechanical energy input “pressure swing adsorption” driven compression and phase change effect. Moreover, the prior art cycle resembles a vapor compression cycle with an evaporator, a condenser, and with the desorption process not being directly utilized for cooling an application such as a building. By contrast, the present invention requires no evaporator, no condenser, and the desorption in the sorption bed is applied directly to a cooling application such as cooling a building or a refrigerator. The present cycle is driven by mechanical energy input from an electric compressor pump or vacuum pump or a renewable wind driven compression pump or vacuum pump, with the mechanical energy applied to pressure swing adsorption, or pressure swing desorption, or to both. Very recently researchers have demonstrated a pressure swing adsorption process applied to producing chilled water. This demonstration is described in Chemical Engineering Journal, 171, (2011) 541-548, Titled “Experimental investigation of a single-bed pressure swing adsorption refrigeration system towards replacement of halogenated refrigerants” by Kumar Anupam et al. It is also described in India Patent Application 1153/KOL/2011 A dated Jan. 9, 2011 and published on Sep. 9, 2011 titled “An Eco-Friendly Mechanism of Cold Production to Combat with Halogenated Refrigerants”, invented by Halder Gopinath, and Kumar Anupam. In these documents, carbon dioxide is the adsorbate, activated carbon is the adsorbent, a COP of 3.014 using a pressure swing of 0.1 MPa to 0.5 MPa, cooled water from 26° C. to 4° C. While this illustrates a prior art application of a pressure swing adsorption cycle and apparatus utilized for a cooling application, the present invention describes and claims more complex cycles, integration of mechanical energy inputs, multiple adsorption beds, application of pressure swing adsorption to both heating and cooling applications, achieving heating and cooling applications concurrently, having one or more beds loaded with adsorbate as a stored capacity to cool, having one or more beds unloaded with adsorbate as a stored capacity to heat, using a pressure differential to passively cool, using a pressure differential to passively heat, a system for leveraging pressure differentials between sorption beds to maximum advantage, integrating pressure swing adsorption heating and cooling with other forms of energy transfer, and an electronic, firmware, software control system to take advantage of these preceding apparatuses and cycles.
BRIEF SUMMARY The present invention is drawn to leveraging pressure swing adsorption to perform a heating function, an energy storage function, and a cooling function. The system uses a closed loop adsorbate fluid such as water vapor which is pressure swing adsorbed releasing heat, and then pressure swing desorbed absorbing heat. The released heat is applied to a heating application such as heating a building or heater or mobile vehicle or substrate and the absorbed heat is absorbed from a cooling application such as cooling a building or refrigerator or freezer or mobile vehicle or substrate. Also, the adsorption and desorption processes can be separated in time such that a pressurized sorption bed provides a stored capacity to cool which can be utilized by simply opening a valve to allow fluid to flow to equalized pressures; similarly, a depressurized sorption bed provides a stored capacity to heat which is utilized simply by opening a valve to allow fluid to flow to equalized pressures. Mechanical energy input “pressure swing adsorption” utilizes compression to drive an exothermic adsorption phase change and utilizes decompression to drive an endothermic desorption phase change wherein one or both processes is applied directly to a respective heating or cooling application such as a building. Mechanical energy input is achieved by an electric compressor/vacuum pump where the electricity is obtained from any available source, including but not limited to the electric grid or from batteries charged by renewable energy such as wind or wave energy. Alternatively, wind or wave mechanical energy input can also directly drive the compressor/vacuum pump without being converted to electricity.
Objects and Advantages Accordingly, several objects and advantages of the present invention are apparent. It is an object of the present invention to provide an energy efficient heating process. It is an object of the present invention to provide an energy efficient cooling process. It is an advantage of the present invention to utilize an adsorbate-adsorbent pair that enables the system to operate within the most efficient part of their adsorbed phase loading versus gas phase pressure isotherm curves with inflexion point slopes greater than 0.1 mol/kg/kPa for adsorption/heating operations. It is an advantage of the present invention to utilize an adsorbate-adsorbent pair that enables the system to operate within the most efficient part of their adsorbed phase loading versus gas phase pressure isotherm curves with inflexion point slopes greater than 0.1 mol/kg/kPa for desorption/cooling operations.
It is an object of the present invention to store energy in a bed in an adsorbed or loaded state for subsequent use in a passive cooling application controlled by a valve allowing fluid to flow to pressure equalization. It is an object of the present invention to store energy in a bed in a desorbed or unloaded state for subsequent use in a passive heating application controlled by a valve allowing fluid to flow to pressure equalization. It is an object of the present invention to provide a cycle that includes a single mechanical energy input step to achieve a pressure change that drives an adsorptive heating application step, an energy storage application step, and a desorptive cooling application step. It is an advantage of the present invention that no condenser is needed. It is an advantage of the present invention that no evaporator is needed. It is an advantage of the present invention that heat from adsorption can be applied directly to an application requiring heat such as a building. It is an advantage of the present invention that heat required for desorption can be extracted directly from an application requiring cooling such as a building or a refrigerator. It is an advantage of the present invention that a higher COP is achievable compared to prior art temperature swing adsorption cycles. It is an advantage of the present invention that water vapor can be used as the primary working fluid adsorbate.
While this document describes a prior art application of pressure swing adsorption cycle and apparatus utilized for a cooling application, the present invention describes and claims more complex cycles, integration of mechanical energy inputs, multiple adsorption beds, application of pressure swing adsorption to both heating and cooling applications, achieving heating and cooling applications concurrently, loading one or more beds as a stored capacity to cool, unloading one or more beds as a stored capacity to heat, using a pressure differential to passively cool, using a pressure differential to passively heat, a system for leveraging pressure differentials between sorption beds to maximum advantage, integrating pressure swing adsorption heating and cooling with other forms of energy transfer, and a electronic, firmware, software control system to take advantage of these preceding apparatuses and cycles.
Further objects and advantages will become apparent from the enclosed figures and specifications.
DRAWING FIGURES FIG. 1 illustrates a portion of a sorption bed.
FIG. 2 illustrates a sorption bed fabrication step.
FIG. 3 illustrates a sorption bed with affixed thermal dissipation array.
FIG. 4 illustrates primary fluid adsorbate flow from a first sorption bed to a second sorption bed.
FIG. 5 illustrates primary fluid adsorbate flow from the second sorption bed to the first sorption bed.
FIG. 6a illustrates secondary fluid flow through the first sorption bed from and to a cooling application and secondary fluid flow through the second sorption bed from and to a heat dump.
FIG. 6b illustrates secondary fluid flow through the second sorption bed from and to a cooling application and secondary fluid flow through the first sorption bed from and to a heat dump.
FIG. 7 illustrates an HVAC cabinet of the present invention.
FIG. 8a is an adsorbent populated substrate.
FIG. 8b is the adsorbent substrate of FIG. 8a rolled up and inserted into a pipe.
FIG. 8c is a sorption bed assembly incorporating several pipes of FIG. 8b.
FIG. 8d illustrates adsorbate flow and secondary fluid flow through the sorption bed assembly of FIG. 8c.
FIG. 9a illustrates Calgon BPL activated carbon-water vapor equilibrium adsorption isotherms over a range of temperatures, gas phase pressures and adsorbed phase loadings.
FIG. 9b illustrates equilibrium adsorption isotherms for CO2 adsorbed by a metal organic framework (MOF) impregnated with an amine over a range of temperatures, gas phase pressures and adsorbed phase loadings.
FIG. 9c illustrates equilibrium adsorption isotherms at 25° C. for water vapor on a) activated alumina (granular), b) activated alumina (spherical), c) silica gel, d) 5A zeolite and e) activated carbon over a range of gas phase pressures and adsorbed phase loadings.
FIG. 10a illustrates transient sorption bed temperatures during Case III adsorption and desorption to cool a cooling application.
FIG. 10b illustrates transient sorption bed temperatures during Case VII adsorption and desorption to heat a heating application.
FIG. 11a illustrates curves describing local sorption bed temperatures versus gas phase pressure during Case III cyclical operation of a sorption bed to cool a cooling application.
FIG. 11b illustrates system performance curves describing local sorption bed adsorbed phase loading versus gas phase pressure during Case III cyclical operation of a sorption bed to cool a cooling application.
FIG. 11c illustrates curves describing local sorption bed temperatures versus gas phase pressure during Case VII cyclical operation of a sorption bed to heat a heating application.
FIG. 11d illustrates system performance curves describing local sorption bed adsorbed phase loading versus gas phase pressure during Case VII cyclical operation of a sorption bed to heat a heating application.
FIG. 12 illustrates several different equilibrium adsorption isotherm curves that are suitable and one that is not suitable for use in the present invention and that can be readily classified based on their IUPAC (International Union of Pure and Applied Chemistry) definitions.
DETAILED DESCRIPTION OF THE INVENTION FIG. 1a illustrates a portion of a sorption bed. An adsorbent 31 is sealably contained in a pipe 33 and prevented from exiting the pipe by a screen 35 which is contained within a screen fitting 37 which is affixed to the pipe 33. In operation, an adsorption process is achieved as pressure increase causes adsorbate flow into adsorbent 39 and a desorption process is achieved as pressure decrease causes adsorbate flow out of adsorbent 40. Adsorbate flow is caused by opening a valve when there is a pressure differential in the system and the pressure differential causes adsorbate to flow from a higher pressure location such as a first bed to a lower pressure location such as a second bed until the two locations reach the same pressure. Adsorbate flow is also caused by pumping as later described. Pumping can be compression pumping where pressure is being increased and it can also be vacuum pumping where pressure is being decreased. The adsorption process is exothermic whereby heat flows out of the adsorbent 31, through the pipe 33, through a heat dissipation array 38 and from the heat dissipation array 38 into a secondary fluid or a substrate to a heat dump or to a heat application as later described. In operation, a desorption process is achieved as pressure decrease causes adsorbate flow out of adsorbent 31. The desorption process is endothermic whereby as later described heat flows from an application to be cooled or from a heat source through a secondary fluid or a substrate through the heat dissipation array 38, through the pipe 33, and into the adsorbent 31.
In a preferred embodiment, the adsorbent 31 is BPL activated carbon granules sourced from Calgon and placed into the pipe 33 according to FIG. 2. The adsorbent 31 comprises a sorption bed. In a preferred embodiment, the adsorbate is water vapor. The pipe 33 is selected to be suitable for heat transfer therethrough, to withstand pressure differentials later described, and to be non-corrosive when in contact with the adsorbent and the adsorbate selected for use in the present invention. The screen 35 and screen fitting 37 are installed prior to input of the adsorbent 31 as described in FIG. 2. The heat dissipation array 38 is fabricated from a metal suitable for heat transfer such as aluminum and during fabrication the pipe 33 is inserted into the heat dissipation array 38 such that the pipe is in contact with the heat dissipation array and heat is efficiently transferred through this contact. The adsorbent 31 is in contact with the pipe 33 such that heat is efficiently transferred to and from the adsorbent through the pipe. As in FIG. 2 and FIG. 3 multiple pipes are used to contain the adsorbent and comprise a sorption coil bed 42 and multiple fins comprise the heat dissipation array such that the secondary fluid can efficiently flow therethrough and transfer thermal energy out of the sorption coil bed 42 during adsorption and transfer thermal energy into the sorption coil bed 42 during desorption.
FIG. 2 illustrates a sorption bed fabrication step. During a fabrication process the pipe 33 is one of multiple but individual pipes aligned in parallel that are inserted into and affixed to the heat dissipation array as depicted in FIG. 3. The pipes are aligned in parallel so that during operation the adsorbate flow occurs simultaneously into each pipe in order to minimize axial pressure drop within each pipe. The series of pipes and the manifold 32 are pictured in two dimensions with a single row of pipes aligned in parallel with each other. It would be obvious to any skilled in the art that this could also be fabricated in three dimensions with banks of pipes all aligned in parallel and with the manifold 33 also being three dimensional and connecting them all together through one single exit or entrance manifold nozzle at one end of the set of pipes. An adsorbent slurry input step 41 is utilized whereby the adsorbent 31 is first mixed with a fluid such as water and then the fluid adsorbent slurry is pumped into a manifold nozzle such as 33 at one end of the pipe assembly. As the fluid adsorbent slurry fills the sorption coil a adsorbent free fluid output 41a flows out of a manifold nozzle such as 33 at the opposite end of each pipe where the screen 35 and similar screens on each pipe contained within the screen fitting 37 and similar fittings on each pipe allows the adsorbent free fluid to pass out of each pipe while preventing the adsorbent from exiting each pipe and the adsorbent thereby fills each pipe within the sorption coil bed 42. Each of the input ends of the pipes are then sealed such that the screened end of each pipe is the only remaining port into the pipe. The sorption coil pipes are then subjected to a vacuum pressure to evacuate liquid from the sorption coil bed and regenerate it so it is prepared for operation in this invention. The sorption coil bed 42 may be also subjected to an elevated temperature to drive out any remaining liquid. In operation, the adsorbate is the primary fluid which is pumped into and out of the sorption coil bed 42 interior and a secondary fluid is caused to flow around the outside of the assembly to cause thermal energy transfer to and from the sorption coil bed 42 and to and from the secondary fluid including a secondary fluid input 43 entering heat dissipation array 38 at a first temperature and a secondary fluid output 45 exiting heat dissipation array 38 at a second temperature.
FIG. 3 illustrates a sorption bed with affixed heat dissipation array 38. It illustrates the sorption coil bed 42 fully integrated with the heat dissipation array 38. A manifold port 32 is sealably affixed to each pipe in the sorption coil bed 42. The manifold port 32 comprises a single adsorbate input/output port to the plurality of pipes within the sorption coil bed. As in FIGS. 4, 5, 6a, 6b, and 7, operation of this invention generally utilizes two or more sorption beds similar to the sorption coil bed 42 with a compressor/vacuum pump, intervening valves, and a control system cooperating to transfer primary fluid adsorbate between the two or more sorption coil bed interiors and fans cooperating to transfer secondary fluid around the exteriors of the sorption coil bed exteriors.
FIGS. 1 through 3 comprising fabrication of a sorption bed designed to ensure primary fluid adsorbate flow through the adsorbent bed interior and secondary fluid flow through external surfaces to ensure efficient thermal energy transfer into the bed during desorption and efficient thermal energy transfer out of the bed during adsorption. The secondary fluid carries thermal energy to and from applications to be heated and/or cooled and to and from heat sources and/or thermal dumps. Thus, the primary and secondary fluids are physically isolated from each other.
FIG. 4 illustrates primary fluid adsorbate flow from a first sorption bed to a second sorption bed. The beds being fabricated as described in FIGS. 1 through 3 then sealably connected to a pump 55 and to valves that are connected to each bed and direct adsorbate flow to the input side of the pump and from the output side of the pump, the valves being opened and closed depending upon flow direction and which bed is performing desorption and which bed is performing adsorption. In operation, a first desorbing sorption bed 51 has primary working fluid adsorbate flowing therefrom while a second adsorbing sorption bed 53 has primary working fluid adsorbate flowing thereto. An adsorbate flow from first sorption bed 57 is driven by the pump 55 through a first sorption bed open outflow valve 59 to the input port of the pump 55 through a second sorption bed open inflow valve 61 and into the second adsorbing sorption bed 53. The primary adsorbate fluid flow from the first desorbing sorption bed 51 causes an endothermic desorption process to occur which cools the bed. A secondary fluid flow into first sorption bed 63 brings thermal energy either from a heat source or from an application to be cooled. Thermal energy from the secondary fluid flow is used in the desorption process and a secondary fluid flow from first sorption bed 65 is at a lower temperature than is the secondary fluid flow into first sorption bed 63. If the system is performing a cooling function, the secondary fluid flow into first sorption bed 63 comes from the application to be cooled, the secondary fluid flow from first sorption bed 65 is at a lower temperature than is the secondary fluid flow into first sorption bed 63 and the secondary fluid flow from first sorption bed 65 returns to the application to be cooled. So, in an air conditioning application the application to be cooled is a home and a fan draws the secondary fluid flow into first sorption bed 63 from the home and the fan blows secondary fluid flow from first sorption bed 65 back into the home. A refrigerator application or a freezer application would operate similarly with fans blowing air as a secondary fluid or relying on a convection energy flow to cool the refrigerator or the freezer.
As the pump moves adsorbate, it lowers pressure within the first sorption bed causing the adsorbate to desorb from the adsorbent, the pump raises pressure in the second adsorbing sorption bed 53 causing the adsorbate to adsorb into the adsorbent. In a cooling application, a fan blows secondary fluid flow into second sorption bed 67 from the heat sink or in the case of an air conditioner or refrigerator or freezer from the ambient air through the heat dissipation array and emerges as a secondary fluid flow from second sorption bed 69 at a higher temperature and is them dumped into the heat sink, the ground source, or the ambient air source. The pump 55 has a distinct input side and a distinct output side such that valves are used to direct flow to and from each bed and during operation where primary fluid flow is from the first bed to the second bed where a first sorption bed closed in flow valve 60 remains closed and a second sorption bed closed out flow valve 62 remains closed. In some configurations, it is possible to remove valves from the adsorbate flow process in FIGS. 4 and 5. For example, where the pump is constructed in a way that it operates in a first rotational direction to cause fluid to flow from the first bed to the second bed and the pump subsequently operates in a second rotational direction to cause fluid to flow from the second sorption bed to the first sorption bed, no valves are needed to direct the flow. Also, valves may be configured to bypass the pump such that when one sorption bed is at a higher pressure and the other sorption bed is at a lower pressure, the valves can bypass the pump to allow adsorbate to flow between beds to produce the adsorption heat and the desorption cooling without the use of the pump. Such a process represents a stored capacity to heat and a stored capacity to cool with no external mechanical, electrical, pressure, or pumping energy input needed. This flow can continue until the beds reach equal pressures and then the pump must operate to elevate the pressure of one sorption bed and lower the pressure of the other bed as previously discussed. The sorbent beds of FIGS. 4 and 5 and throughout this specification are fabricated according to FIGS. 1, 2, and 3 or FIGS. 8a, 8b, 8c, and 8d.
FIG. 5 illustrates primary fluid adsorbate flow from the second sorption bed to the first sorption bed. In the present invention, multiple beds can be used with flow being directed to and from beds and each bed alternately performing desorption and then adsorption. Thus, the first sorption bed which was desorbing in FIG. 4 is now a first adsorbing bed 51a and the second sorption bed of FIG. 4 is now a second desorbing bed 53a. The adsorbate flow in FIG. 5 is reversed from that of FIG. 4 whereby an adsorbate flow from the second sorption bed 57a is driven by the pump 55 and through a second sorption bed open out flow valve 62a and a first sorption bed open in flow valve 60a. A second sorption bed closed in flow valve 61a and a first sorption bed closed out flow valve 59a prevent fluid flow to and from the wrong input and output side of the pump when adsorbate is flowing from the second bed to the first bed. Similarly, secondary fluid flow is now flipped by motorized dampers that are described in FIGS. 6a, 6b, and 7. A secondary fluid flow into the second sorption bed 63a flows from the application to be cooled through the second bed exterior where it is cooled and a secondary fluid flow from the second sorption bed 65a which flows to the application to be cooled. A secondary fluid flow into the first sorption bed 67a is from the heat dump or ambient air through the exterior of the first bed where it is heated and then a secondary fluid flow from the first sorption bed 69a to the heat dump or to the ambient air. The valves and motorized dampers of FIGS. 4, 5, 6a, 6b and 7 open and close and the pump engages in response to a thermostat which is reading the temperature of the particular heating or cooling application and sending a signal to turn the system on and off. Pressure sensors and temperature sensors in the sorption beds send signals used to determine when to open and close valves, motorized dampers, and to turn fans and the pump on and off or vary their throughput.
It should be noted that the system herein is compatible with any heating or cooling application. When used as an air conditioner the secondary fluid is often air and a fan blows air as the secondary fluid from a building through the desorbing bed exterior and back into the building and concurrently a fan blows air as the secondary fluid from the outside of the building through the adsorbing bed exterior and back outside. Cooling a refrigerator or freezer has a similar secondary flow arrangement. Also, the secondary fluid can be air but it can also be any thermally conductive fluid conducive to the operating conditions such as water or glycol which are pumped through the exterior of a bed for example to transfer heat into the desorption bed or to transfer heat out of the adsorption bed. Also, the present invention can be used for heating applications; for example, it can heat water at the same time it cools a building. Also, it can be an air source or ground source heat pump where secondary fluid comes from the interior of a building through the exterior of the adsorbing bed and back to heat the interior of the building; in this scenario, the desorbing bed exterior receives secondary fluid from a heat source such as the ground or air, extracts thermal energy, and the secondary fluid returns to the heat source such as the ground or the air.
FIG. 6a illustrates secondary fluid flow through the first sorption bed from and to a cooling application and secondary fluid flow through the second sorption bed from and to a heat dump. In FIG. 6a, the primary fluid flow is that of FIG. 4. The secondary fluid flow previously discussed is directed by secondary fluid motorized dampers that are affixed to a compartmentalized system cabinet of FIG. 7 with compartments that separate components and secondary fluid flows. Secondary fluid motorized dampers direct secondary fluid flow into the system, into a first compartment, through a sorption bed into a second compartment and out of the system. One bed receives the secondary fluid from an application to be cooled, extracts thermal energy from the secondary fluid which is then directed back to the application to be cooled. Concurrently, the other bed receives the secondary fluid from an application to be heated, dumps thermal energy into the secondary fluid which is then directed back to the application to be heated. Note that fans are used to move the secondary fluid when the secondary fluid is a gas such as air; one or both fans can be replaced with pumps when one or both secondary fluids are a liquid.
A system cabinet 70 of FIG. 7 is a rigid container constructed to contain and to insulate two sorption beds and their respective secondary fluid flows from one another and to house eight secondary fluid motorized dampers that are opened and closed to direct secondary fluid to and from cooling applications, heating applications, and through the sorption bed exteriors. A fan to application 71 is affixed to the system cabinet. An open motorized damper from the application to the first sorption bed 73 is open to direct the secondary fluid flow into the first sorption bed 63 which then becomes the secondary fluid flow from the first sorption bed 65 which flows through an open motorized damper to the application from the first sorption bed 75 and out of the system through the fan to the application 71. In FIG. 6a, the fan to the application 71 drives the secondary fluid flow into the system, through the first sorption bed 51, and out of the system to the application to be cooled. A closed motorized damper from the heat dump to the sorption bed 77 and a closed motorized damper to the heat dump from the sorption bed 79 prevent secondary fluid from flowing therethrough.
Meanwhile, a fan to the heat dump 81 is affixed to the system cabinet and drives secondary fluid flow to and from the second bed. An open motorized damper from the heat dump to the second sorption bed 87 is open to direct the secondary fluid flow into the second sorption bed 67 into the second sorption bed 53 which then becomes the secondary fluid flow from the second sorption bed 69 which flows through an open motorized damper to the heat dump from second sorption bed 89 and out of the system through the fan to heat dump 81. In FIG. 6a, the fan to the heat dump 81 drives the secondary fluid flow into the system, through the second sorption bed 53, and out of the system to the application to be heated. A closed motorized damper from the application to the second sorption bed 83 and a closed motorized damper to the application from the second sorption bed 85 prevent secondary fluid from flowing therethrough. The secondary fluid flow of FIG. 6a is directed to achieve cooling of an application, where it is understood that the motorized dampers can be opened and closed in a complete opposite configuration when the system is used to perform a heating application. Thus, the same system can be used to perform a cooling application and through alternate motorized damper openings a heating application. It is also possible to reverse the fan rotation direction to drive secondary fluid flow in an opposite direction through the system.
As previously mentioned, the primary fluid valves and the secondary fluid motorized dampers and the pump and the fans are turned on and off as directed by a thermostat at the heating application or the cooling application and in response to temperature sensors and pressure sensors in the sorption beds and controlling software logic. In FIG. 6a, the fan to the application 71 drives the secondary fluid flow into the system, through the first sorption bed 51, and out of the system to the application to be cooled. In FIG. 6a, the fan to the heat dump 81 drives the secondary fluid flow into the system, through the second sorption bed 53, and out of the system to the application to be heated. In FIG. 6b, the fan to the application 71 drives the secondary fluid flow into the system, through the second sorption bed 53a, and out of the system to the application to be cooled. In FIG. 6b, the fan to the heat dump 81 drives the secondary fluid flow into the system, through the first sorption bed 51a, and out of the system to the application to be heated. The secondary fluid fans and motorized dampers used herein are well known and widely available in the HVAC industry.
FIG. 6b illustrates secondary fluid flow through the second sorption bed from and to a cooling application and secondary fluid flow through the first sorption bed from and to a heat dump. Once the first sorption bed of FIG. 6a is evacuated below a certain pressure later described, its cooling efficiency diminishes and it is fully discharged. Concurrently, when the second sorption bed increases to a certain pressure later described, it is loaded with adsorbate to where its heating efficiency diminishes and it is fully recharged. At this point, the pump may turn off and all primary valves close such that primary fluid flow is stopped. However, the fan to the heat dump 81 may continue to run to bring the second sorption bed to ambient temperature. Similarly, the fan to the cooling application may continue to run until the first bed reaches the temperature of the incoming secondary fluid. Once the second sorption bed reaches the ambient temperature point the primary fluid flow is reversed from FIG. 4 to be that of FIG. 5 and the secondary fluid motorized dampers and secondary fluid flow is that of FIG. 6b. The fan to the application 71 now drives secondary fluid flow through the second sorption bed where secondary fluid flows from the application to be cooled through an open motorized damper from the application to the second sorption bed 83a, through the second sorption bed 53a, through an open motorized damper to the application from the second sorption bed 85a and out of the system. A closed motorized damper from the heat dump to the second sorption bed 87a and a closed motorized damper to the heat dump from the second sorption bed 89a are now closed and prevent secondary fluid flow therethrough. The fan to the heat dump 81 now drives secondary fluid flow through the first sorption bed 51a. An open motorized damper from the heat dump to the sorption bed 77a directs secondary fluid to flow through the first sorption bed and an open motorized damper to the heat dump from the sorption bed 79a directs secondary fluid out of the system. A closed motorized damper from the application to the first sorption bed 73a and a closed motorized damper to the application from the first sorption bed 75a are closed to prevent secondary fluid flow therethrough. Thus, each sorption bed cycles between an adsorption heating phase with secondary fluid carrying the heat of adsorption to an application to be heated or a heat dump and a desorption cooling phase with secondary fluid carrying heat for desorption to the sorption bed from an application to be cooled or a heat source.
FIG. 7 illustrates an HVAC cabinet of the present invention. In fabrication, the system cabinet 70 is constructed similarly to HVAC systems of the prior art including cut and shaped sheet metal lined with insulation, fitted together and fastened with sheet metal screws. The secondary fluid fans and secondary fluid motorized dampers are also fabricated and mounted the same as those commonly utilized to direct secondary fluid flow in the prior art HVAC industry. The system cabinet 70 has insulated walls inside to define multiple compartments designed to isolate elements from one another, direct secondary fluid flow, and to seat secondary fluid fans, secondary fluid motorized dampers, sorption beds, the pump, primary fluid valves and lines, and electronics. The cabinet of FIG. 7 is that operationally described in FIGS. 4 and 6a. A first compartment 72 is illustrated to be missing a wall to allow viewing inside the first compartment; in actual practice the wall would be in place and one would not be able to see within the first compartment. The first sorption bed 51 is sealably mounted on the wall between the first compartment and a second compartment 74. In FIG. 6a secondary fluid flows from the first compartment through the first sorption bed and into the second compartment. Similarly, the second sorption bed (not visible in the illustration) is mounted on a wall between a third compartment 76 and a fourth compartment 78. Secondary fluid from the second sorption bed flows through a fifth compartment 82 before exiting the system. The secondary fluid motorized dampers are each sealably mounted on walls within the system cabinet 70 to direct secondary fluid flow as previously discussed. The open motorized damper from the application to the first sorption bed 73 is mounted in the rear wall of the first compartment. The open motorized damper to the application from the first sorption bed 75 is mounted in the rear wall of the second compartment. The closed motorized damper from the heat dump to the sorption bed 77 is mounted in the floor of the first compartment. The closed motorized damper to the heat dump from the sorption bed 79 is mounted in the ceiling/floor between the second compartment and the fifth compartment. The closed motorized damper from the application to the second sorption bed 83 is mounted in the rear wall of the third compartment. The closed motorized damper to the application from the second sorption bed 85 is mounted in the rear wall of the forth compartment. The open motorized damper from the heat dump to the second sorption bed 87 is mounted in the floor of the fourth compartment. The open motorized damper to the heat dump from the second sorption bed 89 is mounted in the ceiling/floor between the third compartment and the fifth compartment. Other than the secondary fluid motorized dampers, the sorption beds and the fans, each compartment is sealed such that secondary fluid cannot flow therethrough. The system interfaces with an application to be heated or cooled such as a building including a feed duct from the building 80 interface and a receiving duct to the building which is not shown. The secondary fluid flows to and from the building through the ducts.
While FIG. 7 illustrates, the present invention applied to a building it is understood that it can be applied to an application requiring cooling or heating such as a refrigerator, a freezer, a movable vehicle, a substrate, and a heater. Similarly the system can extract thermal energy from and dump thermal energy into any source for example a ground source, a water source, and an air source.
FIG. 8a is an adsorbent populated substrate. FIGS. 1 through 3 described a sorption bed fabrication method. FIGS. 8a through 8d illustrate an alternate sorption bed fabrication methodology. A foil 91 is a foil metal suitable for depositing an affixed activated carbon adsorbent 93. Catacel (also known as Johnson Matthey) is a manufacturer of adsorbent coated foils used in fabrications similarly to those in FIGS. 8a, through 8d that are populated with activated carbon and other adsorbents which are suitable for use herein.
FIG. 8b is the adsorbent substrate of FIG. 8a rolled up and inserted into a pipe. The foil 91 including the affixed activated carbon adsorbent 93 is physically rolled up and inserted into an alternate sorption bed pipe 97. Catacel manufactures pipes such as the alternate sorption bed pipe 97. Documentation from Catacel indicates that the adsorptive density of such pipes are significantly greater than the Calgon activated carbon utilized in FIGS. 1 through 3 and the foil metal backing is thermally conductive and has good physical contact with the alternate sorption bed pipe 97. Thermal energy very efficiently moves from adsorption in the affixed activated carbon adsorbent 93 through the foil 91 and out of the alternate sorption bed pipe 97. Also thermal energy very efficiently moves from the alternate sorption bed pipe 97 through the foil 91 and into desorption occurring in the affixed activated carbon adsorbent 93. Pipes populated with adsorbent as described in FIG. 8b can be substituted for pipes populated with adsorbent as described in FIG. 1 through 3.
FIG. 8c is a sorption bed assembly incorporating several pipes of FIG. 8b. The alternate sorption bed pipe 97 and similar pipes are installed with a housing 92. The space between the housing 92 and the alternate sorption bed pipes is filled with thermally conductive material 94 such as a steel wool which has high thermal conductivity and a high amount of air space to allow air flow therethrough. During adsorption, thermally energy is transferred from the alternate sorption bed pipe 97 through the thermally conductive material 94 into the secondary fluid which is pumped through the housing 92 and carried out of the system. During desorption, the secondary fluid brings thermal energy into the housing 92, which is picked up by the thermally conductive material and then into the alternate sorption bed pipe 97.
FIG. 8d illustrates adsorbate flow and secondary fluid flow through the sorption bed assembly of FIG. 8c. The housing 92 has a primary fluid port 102 through which adsorbate is added into the alternate sorption bed pipe 97 during adsorption and through which adsorbate is taken out of the alternate sorption bed pipe 97 during desorption. The housing 92 has a secondary fluid input port 96 and a secondary fluid output port 98 through which secondary fluid flows.
Alternate bed fabrications offer comparative advantages to one another and the optimal bed produces the highest system COP balancing the following constraints. The optimal bed minimizes internal non-adsorbent volume, ensures adsorbate flow therethrough, has structural integrity to withstand the range of pressures needed, maximizes thermal conductivity from the internal adsorption process to the container (such as the pipe) wall, maximizes thermal conductivity to the internal desorption process from the container (such as the pipe) wall, and maximizes thermal conductivity between the container wall and the secondary fluid.
Additionally, selection of the optimal set of isotherm curves produced by an adsorbate-adsorbent pair and system operation within the most efficient part of that set of isotherm curves produces the highest COP.
FIG. 9a illustrates a Calgon BPL activated carbon-water vapor equilibrium adsorption isotherms set 99 over a range of temperatures, gas phase pressures and adsorbed phase loadings. Note the isotherm curves are all s-shaped (in this case they are all classified as IUPAC Type V isotherms) and have steep slopes greater than 0.1 mol/kg/kPa) through much of the operating range of interest to this invention. A steep slope of the isotherm curve indicates a high efficiency of the system since small increments in pumping pressure causes large increments or changes in the adsorbed phase loading of the adsorbate on the adsorbent. Thus, less pressure swing work input is required to achieve large amounts of adsorbate to be adsorbed or desorbed with a correspondingly high heat of adsorption output or high heat of desorption input, thus resulting in a high COP for either heating or cooling applications.
FIG. 9b illustrates a graph 101 of the equilibrium adsorption isotherms for CO2 adsorbed by a metal organic framework (MOF) impregnated with an amine over a range of temperatures, gas phase pressures and adsorbed phase loadings. This is an alternative adsorbate-adsorbent pair that exhibits the desirable characteristics over a range of adsorption temperatures, gas phase pressures and adsorbed phase loadings. The curves from left to right are at 25° C., 50° C., 75° C., 100° C., and 120° C. Again, these desirable characteristics are s-shaped isotherms (in this case they are again all classified as IUPAC Type V isotherms) with steep slopes greater than 0.1 mol/kg/kPa) through much of the operating range of interest. Again, for this system small pressure swing work input is needed to produce a high heat of adsorption output or high heat of desorption input with correspondingly high COPs for heating or cooling applications.
FIG. 9c illustrates some additional equilibrium adsorption isotherms 103 at 25° C. for water vapor on A) activated alumina (granular), B) activated alumina (spherical), C) silica gel, D) 5A zeolite and E) activated carbon over a range of gas phase pressures and adsorbed phase loadings. Isotherm B (IUPAC Type II) and isotherm E (IUPAC Type V) are advantageous for this invention as they exhibit the desirable characteristics, i.e., they are both s-shaped isotherms with steep slopes greater than 0.1 mol/kg/kPa) through much of the operating range of interest. In contrast, isotherm A, isotherm C and isotherm D (being all IUPAC Type I) are not advantageous for this invention, as they do not exhibit the desirable characteristics. This graph also illustrates that certain types of activated alumina exhibit the desirable characteristics with water vapor as the adsorbate (isotherm B), while other types of activated alumina may not exhibit the desirable characteristics with water vapor as the adsorbate (isotherm A). The desirable operating range for isotherm B is above 50% relative humidity (partial pressure) because a significant change in the adsorbed phase loading takes place in the 50% to 100% relative humidity range. Isotherm A exhibits about the same change in the adsorbed phase loading but over a much broader range of relative humidity spanning between 0% and 100% which is undesirable. The same undesirable features are also exhibited by isotherm C. Similarly, isotherm D would have to be pumped down to a very low pressure (i.e., relative humidity) to exhibit roughly the same change in adsorbed phase loading as isotherm B. Isotherm E is similar to the isotherms illustrated in FIG. 9a and thus exhibits the desirable characteristics with water vapor as the adsorbate.
Operational parameters of the above system using the Calgon BPL activated carbon-water vapor adsorbent-adsorbate system are described in the following Table 1 including Cases I, II, III, and W. These performance results were obtained through rigorous mathematical simulation of the adsorption and desorption processes taking place within the sorption beds. The adsorption isotherms used in these simulations and corresponding to the results in Table 1 display isotherm curves similar to those illustrated in FIG. 9a. These four cases describe summer operation as an air conditioner performance wherein the exterior air temperature is at 95° F. and the interior air temperature is at 80° F. The summary of these results is that heat transfer through the pipe 33 and through the heat dissipation array 38 is key to reach a high COP (up to a COP of 8.3 as in Case III). If the system is heat transfer limited, the bed experiences large swings of temperatures and pressures, smaller working capacities (i.e., changes in the mols of water vapor adsorbed or desorbed per kg of adsorbent from the adsorbed phase during a heating or cooling cycle) and lower COP. This can be observed when comparing Case I to Case III, where the heat transfer coefficient (ha, kW/m/K) in Table 1 is improved and the corresponding COP is raised from a COP of 3.3909 in Case I to be a COP of 8.2879 in Case III due to more efficient heat transfer into pipe 33 and through the heat dissipation array 38 to and from the secondary fluid. Note that in Case III the temperature difference from the system interior compared to the outside temperature is about 15° F. during cooling (desorption) and during heating (adsorption). Alternatively, the cycle times have to be significantly longer to improve performance as is described in Case IV relative to Case I. For the same thermal energy transfer demand, this would imply the use of bigger beds. Note that Cv is the valve coefficient which indicates the degree of opening of the primary valve or the size of the valve such as the first sorption bed open out flow valve 59 and the other valves of FIGS. 4 and 5 that are directing the flow of the primary fluid adsorbate through the interior of the system.
TABLE 1
Case
I II III IV
Highest Heat Exchanger T, ° F. 95.00 95.00 95.00 95.00
Lowest Heat Exchanger T, ° F. 80.01 80.01 80.01 80.01
Half Cycle Time, s 2200.0 2200.0 2200.0 6000.0
h, kW/m/K 0.2 1.0 2.0 0.2
Valve Cv 10.0 10.0 10.0 5.0
Effective Heat Transferred 0.1600 0.4242 0.4402 0.3587
Energy/half cycle, Kwh (1)
Pump Consumption/half 0.0472 0.0706 0.0531 0.0798
cycle, Kwh (2)
Power, kW 0.2619 0.6942 0.7204 0.5869
Pump Power, kW 0.0772 0.1155 0.0869 0.1305
COP, (3) = (1)/(2) 3.3909 6.0096 8.2879 4.4961
Mass Adsorbent,kg 1.8121 1.8121 1.8121 1.8121
Working Capacity, mol/kg 8.9144 19.6969 20.2060 17.2683
Working Capacity, kg/kg 0.1605 0.3545 0.3637 0.3108
Bed Volume, m3 0.004119 0.004119 0.004119 0.004119
Energy density (kWh/m{circumflex over ( )}3) 38.85 103.00 106.89 87.09
Energy density (kWh/kg) 0.0883 0.2341 0.2429 0.1979
Power density (kW/m{circumflex over ( )}3) 63.58 168.55 174.91 142.51
Power density (kW/kg) 0.1445 0.3831 0.3975 0.3239
Lowest P, Torr 4.91 2.72 2.27 5.46
Highest P, Torr 108.50 45.21 37.44 73.30
Table 2 describes operational parameters of the system operating as a heat pump during the winter, including Cases V, IV and VII. These performance results were also obtained through rigorous mathematical simulation of the adsorption and desorption processes taking place within the sorption beds. The adsorption isotherms used in these simulations and corresponding to the results in Table 1 are again similar to those illustrated in FIG. 9a. Cases V, VI and VII operate when the exterior air temperature is 47° F. and the interior air temperature is 70° F. These Table 2 results are to be compared to Case III of Table I, wherein the same heat transfer coefficient was used so that the same heat pump system can be used for either cooling during the summer or heating during the winter. The summary of these results is that the unit in winter needs a larger primary fluid adsorbate valve (i.e., a larger Cv value) to be able to operate at working capacities comparable to the summer. Because of where the system operates with respect to the temperature, pressure and adsorbed phase loading isotherm space shown in FIG. 3a, i.e., at lower pressures during winter, the gas phase densities and corresponding flow rates through the valve will be much lower, which in turn require a larger Cv. Increasing the Cv thus leads to higher flow rates and hence helps increase the working capacity as shown in Table 2 where the Cv is increased in going from Case V to Case VI and then from Case VI to Case VII. These larger Cv values also create larger swings in temperatures and pressures, and thus smaller COPs. In Table 2 the working capacity for Case V is only 0.1954 kg/kg which is much smaller compared to that of Case DI (Table 1) which is 0.3637 kg/kg. Notice that these two runs use the same Cv of 10. In contrast, the working capacity improves significantly when the Cv is increased to 20 and 30 as shown by Cases VI and VII, respectively. Now Case VII has a working capacity that is more in line with that of Case III. However, this produces a lower COP since the system is swinging through larger changes in pressure which makes the pump do more work. These results in Tables 1 and 2 collectively show that the same heat pump system can be used for either heating or cooling applications with the appropriate control valve for changing the Cv as required for either heating or cooling applications.
TABLE 2
Case
V VI VII
Highest Heat Exchanger T, ° F. 70.00 70.00 70.00
Lowest Heat Exchanger T, ° F. 47.00 47.00 47.00
Half Cycle Time, s 2200.0 2200.0 2200.0
h, kW/m/IC 2.0 2.0 2.0
Valve Cv 10.0 20.0 30.0
Effective Heat Transferred 0.2278 0.3230 0.3541
Energy/half cycle, Kwh (1)
Pump Consumption/half 0.0248 0.0408 0.0486
cycle, Kwh (2)
Power, kW 0.3728 0.5285 0.5795
Pump Power, kW 0.0406 0.0668 0.0795
COP, (3) = (1)/(2) 9.1790 7.9155 7.2892
Mass Adsorbent, kg 1.8121 1.8121 1.8121
Working Capacity, mol/kg 10.8550 15.0802 16.3803
Working Capacity, kg/kg 0.1954 0.2714 0.2948
Bed Volume, m3 0.004119 0.004119 0.004119
Energy density (kWh/m{circumflex over ( )}3) 55.32 78.42 85.98
Energy density (kWh/kg) 0.1257 0.1782 0.1954
Power density (kW/m{circumflex over ( )}3) 90.52 128.33 140.69
Power density (kW/kg) 0.2057 0.2917 0.3198
Lowest P, Torr 3.40 2.59 2.29
Highest P, Torr 17.48 17.55 16.29
FIG. 10a illustrates how the bed temperature of one of the beds changes over time during the cooling application of Case III and for two complete adsorption and desorption cycles. In Case III the bed temperature during adsorption 112 is roughly 15° F. higher than the secondary fluid input temperature and the bed temperature during desorption 114 is roughly 15° F. cooler than the secondary fluid input temperature. The former bed temperature during adsorption provides the heat source to eject heat into the secondary fluid and thus into the environment. The latter bed temperature during desorption provides the heat sink to remove heat from the secondary fluid for the cooling operation.
FIG. 10b illustrates how the bed temperature of one of the beds changes over time during the heating application of Case VII and for two complete adsorption and desorption cycles. In Case VII the bed temperature during adsorption 116 is roughly 10° F. higher than the secondary fluid input temperature and the bed temperature during desorption 118 is roughly 10° F. cooler than the secondary fluid input temperature. The former bed temperature during adsorption provides the heat source to supply heat to the secondary fluid for the heating operation. The latter bed temperature during desorption provides the heat sink to extract heat from the secondary fluid and thus from the environment.
FIG. 11a illustrates the corresponding cyclical operation of a bed through adsorption and desorption processes for the cooling application described in Table 1 Case III in terms of the local temperature versus gas phase pressure. A Case III cooling desorption bed temperature curve 124 shows the Case III bed temperature during desorption as a function of pressure. A Case III cooling adsorption bed temperature curve 122 shows the Case III bed temperature during adsorption as a function of pressure.
FIG. 11b illustrates the corresponding cyclical operation of a bed through adsorption and desorption processes for the cooling application described in Table 1 Case III in terms of the local adsorbed phase loading versus gas phase pressure, i.e., the system performance curve. A Case III cooling desorption bed loading curve 124a shows the Case III bed loading during desorption as a function of pressure. A Case III cooling adsorption bed loading curve 122a shows the Case III bed loading during adsorption as a function of pressure.
FIG. 11c illustrates the corresponding cyclical operation of a bed through adsorption and desorption processes for the heating application described in Table 2 Case VII in terms of the local temperature versus gas phase pressure. A Case VII heating desorption bed temperature curve 126 shows the Case VII bed temperature during desorption as a function of pressure. A Case VII heating adsorption bed temperature curve 128 shows the Case VII bed temperature during adsorption as a function of pressure.
FIG. 11d illustrates the corresponding cyclical operation of a bed through adsorption and desorption processes for the heating application described in Table 2 Case VII in terms of the local adsorbed phase loading versus gas phase pressure, i.e., the system performance curve. A Case VII heating desorption bed loading curve 126a shows the Case VII bed loading during desorption as a function of pressure. A Case VII heating adsorption bed loading curve 128a shows the Case VII bed loading during adsorption as a function of pressure.
The adsorbed phase loading-pressure performance curves in FIGS. 11b and 11d are unique to this water vapor-activated carbon adsorbate-adsorbent system. The adsorption/heating curve of the loading-pressure performance curve such as 122a and 128a does not correspond to a single equilibrium adsorption isotherm as the system crosses many such isotherms like those shown in FIG. 9a during the adsorption step because the bed temperature increases during this step as shown in curves 122 and 128. Similarly, the desorption/cooling curve of the loading-pressure performance curve such as 124a and 126a does not correspond to a single equilibrium adsorption isotherm as the system crosses many such isotherms like those shown in FIG. 9a during the desorption step because the bed temperature decreases during this step as shown in curves 124 and 126. This is readily observed by superimposing FIG. 11b or 11d on top of FIG. 9a, with both pressure axes expressed in the same units like Torr. The point is the curves in FIG. 9a are equilibrium adsorption isotherm curves, whereas the performance curves in FIG. 11b or 11d are not equilibrium adsorption isotherm curves. The direct relationship between them is that the performance curves are derived from the equilibrium adsorption isotherm curves.
There are optimal shapes to the performance curves of FIGS. 11b and 11d that correspond directly to the equilibrium adsorption isotherm curves in FIG. 9a where steeper equilibrium adsorption isotherm curves correspond to a better adsorbate-adsorbent system with respect to COP performance. For system operation, there are also optimal positions for these equilibrium adsorption isotherm curves relative to each other along the pressure (horizontal) axis, where if the isotherms are too close to each other the heat of adsorption is too low even though the work of the pump will be lower and if the isotherms are too far apart the work of the pump is too high even though the heat of adsorption will be higher. It is also more optimum or desirable that the inflexion point regions of the equilibrium adsorption isotherm curves be located at pressures more away from the origin to minimize the work of the pump, at least for this water vapor-activated carbon adsorbate-adsorbent system. For other adsorbate-adsorbent systems, like water vapor-activated alumina (FIG. 9c, curve B) or carbon dioxide-amine impregnated MOF (FIG. 9b), the optimal set of equilibrium adsorption isotherm curves that maximize the COP may be different and is dictated by the thermodynamics of the adsorbate-adsorbent system and the required operating conditions (i.e., heating or cooling duties).
FIG. 12 illustrates several isotherm curves that are suitable for use in the present invention. IUPAC (International Union of Pure and Applied Chemistry) has classified a variety of isotherm types. FIG. 12 illustrates several of these IUPAC isotherm types that do satisfy a necessary condition and one that does not satisfy a necessary condition to be a useful adsorbate-adsorbent pair for this invention. Only a few cases are illustrated with IUPAC a) Type I, b) Type V, c) Type V, d) Type IV, e) Type VI and f) Type VI isotherms; other cases would include any type of isotherm as defined by Types I to VI by the IUPAC. These isotherms represent either the adsorption or desorption branch, indicating any of these isotherms could display a hysteresis loop defined as H1 to H5 by the IUPAC. The equilibrium adsorption isotherms depict the onset pressure (PL) and the offset pressure (PH) that define the change in adsorbed phase loading or working capacity Δq of interest. As shown in each case, the onset and offset pressures are determined by the intersection between the tangent line at the inflexion point where the change of adsorbed phase loading of interest takes place and the tangent at the saddle point directly below and above, respectively. In the absence of a saddle point, the tangent corresponds to the horizontal asymptote. In the case of a Type I isotherm as in 12a, which by the IUPAC definition cannot exhibit an inflexion point, the onset pressure corresponds to the origin (i.e., where q=0 and P=0), which is undesirable for the present invention. Curve 12f includes a situation where the change in the adsorbed phase loading could include more than one inflexion point. Only cases that show onset pressures greater than zero satisfy the necessary condition to be useful in the present invention. In other words, Type I isotherms such as curve 12a are not useful for the present invention.
The curves of FIGS. 9a, 9b, 9c (E only) are classified by IUPAC (International Union of Pure and Applied Chemistry) as Type V isotherm curves. FIG. 9c (B only) is classified by IUPAC as a Type II isotherm curve. When each of these curves display an inflexion point slope greater than 0.1 mol/kg/kPa and a pressure ratio of PH/PL<20.0, it makes these adsorbate-adsorbent pairings suitable for use within the present invention within suitable operational temperature and pressure ranges. Curves A, C and D in FIG. 9c (all being Type I isotherms) do not display an inflexion point slope greater than 0.1 mol/kg/kPa because as stated above Type I isotherms cannot exhibit inflexion points; and because the onset pressure PL is zero, they necessarily display a pressure ratio of PH/PL=infinity. Thus, adsorbate-adsorbent pairings that exhibit Type I isotherms are not suitable for use within the present invention. Isotherms that are suitable include those of Types II, III, IV, V and VI, which are preferred because adsorbate-adsorbent pairs that exhibit these shapes most likely meet the two criteria set forth herein: 1) an inflexion point slope greater than 0.1 mol/kg/kPa and 2) a pressure ratio of PH/PL<20.0.
Another condition that must be met by an adsorbate-adsorbent pair covered by this invention is that their equilibrium adsorption isotherm curves corresponding to the performance curve must exhibit a Δq*ΔH>5 kJ/kg, where ΔH is the heat of adsorption. As an example, the product of Δq*ΔH for water vapor adsorbed on BPL activated carbon, i.e., one of the adsorbate-adsorbent pairs of interest for this invention, is about 20 (mol/kg)*40 (kJ/mol)=80 kJ/kg. Even if it is such that an adsorbate-adsorbent pair corresponding to any one of the six IUPAC isotherm types exhibits a Δq*ΔH>5 kJ/kg, even a Type I isotherm, for this adsorbate-adsorbent pair to be useful for this invention at least one of its equilibrium adsorption isotherm curves must also satisfy the two additional criteria, i.e., an inflexion point slope greater than 0.1 mol/kg/kPa and a pressure ratio of PH/PL<20.0.
In summary, of the six types of isotherms and five types of hysteresis loops defined by the IUPAC, the only one not suitable for this invention is Type I which is illustrated in FIG. 12a. It is also illustrated by isotherm curves A, C and D in FIG. 9c. Suitable IUPAC isotherm types include those of types II, III, IV, V and IV. As suitable examples, IUPAC Type V is similar to that in FIGS. 12b and 12c and also Case III in Table 1 and FIGS. 9a and 9b. IUPAC Type II is similar to that in FIG. 12d and is also illustrated by isotherm curve B in FIG. 9c.
OPERATION OF THE INVENTION Operation of the invention has been discussed under the above heading and is not repeated here to avoid redundancy.
CONCLUSION, RAMIFICATIONS AND SCOPE The reader will see that the apparatus and processes of this invention provides an efficient, energy saving, greenhouse gas reducing, thermal pollution reducing, novel, unanticipated, highly functional and reliable means for heating and cooling applications and storing energy in the form of the stored capacity to cool and the stored capacity to heat.
The preceding has described water vapor as the adsorbate; it is understood that any fluid or combination of fluids can comprise the adsorbate as long as they meet conditions set forth herein. The preceding has described activated carbon as the adsorbent; it is understood that any other adsorbent may be substituted as long as they meet conditions set forth herein. The goal is to minimize acquisition and operational costs while maximizing efficiency and energy density.
The terms “primary working fluid” and “adsorbate” in the specifications have the same meaning and are interchangeable.
Intervening steps, valves, pumps, motorized dampers, fans, sensors, actuators and other components may be added to enhance efficiency.
The heat exchange system described herein as a secondary fluid is one example; many heat exchange techniques are known and may be substituted to increase efficiency and reduce cost.
The terms “compressor” and “pump” have the same meaning in that through mechanical work they transfer a primary working fluid adsorbate from a first location to a second location and/or transform working fluid from a lower pressure to a higher pressure or from a higher pressure to a lower pressure.
While the above description describes many specifications, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of a preferred embodiment thereof. Many other variations are possible.
