Patent Application
20240361045
The present invention relates generally to systems that make, store, and use thermal energy in the form of ice to provide thermal storage and cooling to residences and commercial buildings.
With the increasing demands on peak demand power consumption, ice storage has been utilized to shift air conditioning power loads to off-peak times and rates. A need exists not only for load shifting from peak to off-peak periods, but also for increases in air conditioning unit capacity and efficiency. In order to commercialize advantages of thermal energy storage in residences and commercial buildings, thermal energy storage systems must have minimal manufacturing costs, maintain efficiency under varying operating conditions, and maintain flexibility in multiple refrigeration or air conditioning applications.
Systems for providing thermal stored energy have been previously disclosed in U.S. Pat. Nos. 7,363,772, 7,793,515, and 7,421,846 all by Ramachandran Narayanamurthy. All of these patents utilize ice storage to shift air conditioning loads from peak to off-peak electric rates to provide economic justification and are hereby incorporated by reference herein for all they teach and disclose.
Disclosed are a device as well as a system and methods for storing thermal energy in the form of ice and using the stored thermal energy to provide cooling to residences and other buildings. The device is a refrigerant-based thermal storage system with an ice-tank heat exchanger that cools a refrigerant that is circulated to an air handler as part of an air conditioning system. The device integrates with commercial heating and cooling devices such as compressors, condensers, air handlers, fans, air conditioning systems, furnaces and heating, ventilation and air conditioning (HVAC) systems.
An embodiment of the present invention includes a refrigerant-based thermal energy storage and cooling system (also referred to by its acronym RTESC) that operates in three modes, an ice make mode, an ice melt mode, and a direct cooling mode.
In certain embodiments the invention works with an external condenser unit, including a condenser that operates as part of an air conditioner, a heat pump or a HVAC system. The external condenser cools warm refrigerant returned by the thermal energy device and returns the cool refrigerant to the device.
In certain embodiments, the invention generates cooling by pumping cold refrigerant through an evaporator coil that is integrated with an air handler, such as an air handler that is part of a commercial HVAC system.
The invention includes a first refrigerant loop that receives warm refrigerant from the device, cools it and circulates the cool refrigerant to an isolating heat exchanger that cools refrigerant in a second refrigerant loop. The cool refrigerant in the second refrigerant loop is directed from a vessel to an ice tank filled with a fluid capable of a phase change between liquid and solid, wherein the tank uses the refrigerant to cool the fluid and to freeze at least a portion of the fluid within the tank.
An embodiment of the present invention may further comprise a refrigerant-based thermal energy storage and cooling system comprising: a first refrigerant loop containing a first refrigerant; a second refrigerant loop containing a second refrigerant, which is a different material than the first refrigerant; an isolating heat exchanger disposed between the first refrigerant loop and the second refrigerant loop for thermal communication therebetween; and, a ice-based heat exchanger within the second refrigerant loop that transfers to a load. In certain embodiments, the load is ambient air circulating in a building by an air handler, which results in air conditioning.
Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following drawings. In the drawings, like reference numerals refer to like parts throughout the various figures unless otherwise specified. A brief introduction of the figures is below.
The figures depict embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.
While this invention is susceptible to embodiment in many different forms, there is shown in the drawings and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not to be limited to the specific embodiments described.
The disclosed embodiments overcome the disadvantages and limitations of the prior art by providing a refrigerant-based thermal storage system and device wherein an ice-tank heat exchanger can be integrated with commercial HVAC components to provide a system that reduces the demand for electricity to operate an air conditioner during peak periods.
As used herein the following terms have the meanings given below:
Thermal energy storage system—as used herein, refers to a system that stores energy and discharges energy in thermal form. Typically, the stored energy is in the form of a liquid that is stored at a higher or lower temperature than ambient temperature. More specifically, certain embodiments store energy in the form of ice or cold water.
Refrigerant—as used herein is a fluid used in the refrigeration cycle of air conditioning systems and heat pumps where they undergo a repeated phase transition from a liquid to a gas (or vapor) and back again. An example of a refrigerant that may be used with the invention is R-410A, which has a boiling point of −48.5 C.
Condenser unit—as used herein condenser unit receives refrigerant in vapor phase, liquid phase or in partial liquid and partial vapor phase and generates cool liquid refrigerant. A condenser unit typically includes both a compressor and a condenser. A condenser unit may be the outdoor portion of an air conditioning or HVAC device or system, a commercial condenser, or a heat pump.
During ice make mode, condenser unit 10 directs cold refrigerant into a vessel 20. Vessel 20 provides the cold refrigerant through heat exchange coils 44 (henceforth referred to coils 44) that run vertically through a tank 42 that holds water and ice. Due to the low boiling temperature of the refrigerant the relatively warmer water found at the bottom of tank 42 boils the refrigerant which changes to gaseous phase and rises through coils 44. The refrigerant flowing in coils 44 absorbs heat from the water and effectively freezes the water and generates a solid block of ice. Effectively, when device 2 operates in ice make mode tank 42 in conjunction with coils 44 form a heat exchanger, transforming cold liquid refrigerant into warm refrigerant vapor and in the process freezing water to make ice.
Refrigerant in vapor form rises to the top of tank 42 where it is piped into the top of vessel 20. The horizontal line in
Finally, to complete the cycle, refrigerant in gas form is sucked out of vessel 20 and piped back to condenser unit 10 which transforms it back into liquid form.
Air handler 60 generates cool air inside a building or residence that is blown through ductwork and thereby distributed within a building. In the process, refrigerant flowing through air handler 60 is heated. The heated refrigerant, which may be in vapor form or partial vapor and partial liquid form is returned to vessel 20. The warmer vapor phase refrigerant is then sucked into tank 42 at the top where it flows or descends downward through coils 44. The warmer gas melts the surrounding ice, which flows to the bottom of tank 42. The refrigerant accordingly loses temperature and condenses, i.e. returns to liquid form, as it descends through coils 44. The cool refrigerant is then piped back to vessel 20. Cool refrigerant is then pumped into an evaporator coil 62 that is integrated with air handler 60. Air handler 60, which is equipped with a fan, blows room temperature air or outside air across evaporator coil 62 to generate cool air.
Finally, to complete the cycle, the cool refrigerant in liquid or partial liquid and gas is sucked returned to vessel 20.
Effectively, when device 2 operates in ice melt mode, tank 42 in conjunction with coils 44 form a condenser that transforms warm refrigerant in vapor form into cold liquid refrigerant and in the process melts ice inside tank 42 into water.
The horizontal line in
As illustrated in
Condenser unit 10 receives a stream of refrigerant in gas, liquid or partial gas and partial liquid form to generate a stream of liquid refrigerant that it directs through a supply line 12 to an expansion device 18.
Supply line 12 and return line 14 are commercially available tubes or pipes that carry refrigerant in liquid or gas form. They may be made of plastic, copper or from a range of other materials. Generally, all refrigerant lines depicted in
First refrigerant supplied by condenser unit 10 enters expansion device 18, which generates a stream of further cooled refrigerant in liquid, vapor, or partial liquid and partial vapor form which is then supplied to an isolating heat exchanger 16. Expansion device 18 may be a conventional thermal expansion valve, a mixed-phase regulator and surge vessel (reservoir) or the like. In certain embodiments, the first refrigerant is sufficiently cooled by condenser unit 10 that an expansion device is not required.
Isolating heat exchanger 16 transfers cooling from a first refrigerant loop 5 to a second refrigerant loop 7. It cools the refrigerant circulating in second refrigerant loop 7 and supplies the cool refrigerant to a refrigerant vessel 20 (henceforth referred to simply as vessel 20). Isolating heat exchanger 16 may be, for example, a brazed plate heat exchanger that uses corrugated plates to create channels that carry a liquid medium such as refrigerant. First refrigerant loop 5 circulates a first refrigerant and second refrigerant loop 7 circulates a second refrigerant. The first and second refrigerants may be the same liquid or material or they may be different liquids or materials.
Vessel 20 is typically a cylindrical tank that holds refrigerant in liquid and vapor form. The liquid naturally resides at the bottom and vapor naturally fills the cavity above the liquid. In certain embodiments, vessel 20 is cylindrical in form and is oriented horizontally and has a horizontal axis through its center; in other embodiments vessel 20 is oriented vertically and has a vertical axis through its center. Vessel 20 has a number of tubes, or lines that emanate from it; the lower lines (with respect to a vertical axis) supply liquid phase refrigerant and the higher lines supply vapor phase refrigerant. Lines that supply mixed phase refrigerant are typically placed closer to the vertical center of vessel 20. Additionally, in certain embodiments there are lines that suck refrigerant in liquid phase that enter vessel 20 from the top and terminate towards the bottom. Such lines are often referred to as “dip tubes” since the tube dips into the liquid region of vessel 20.
Vessel 20 supplies cool refrigerant, through a supply line 26, to a primary heat exchanger 40 which forms a block of ice when device 2 operates in an ice make mode, and melts the ice to generate cooling, typically for purposes of air conditioning, when device 2 operates in an ice melt mode. Primary heat exchanger 40 includes an insulated ice tank 42, which houses a number of coils 44 which run vertically through ice tank 42. In operation, coils 44 are surrounded by fluid and/or ice depending on the current mode of operation. Primary heat exchanger 40 further includes a lower header assembly connected through coils 44 to an upper header assembly. The upper and lower header assemblies (not identified in the figures) exchange fluid and vapor with other components with supply and return lines as previously discussed. The form of primary heat exchanger 40 has been referred to as a box spring heat exchanger.
When device 2 supplies cooling to air handler 60 it releases liquid from vessel 20 through supply line 26. The cold refrigerant is pumped by pump 50 through an evaporator coil 62 which is integrated with air handler 60.
In contrast, to prior art devices there is no inline expansion device between pump 50 and air handler 60; thus, evaporator coil 62 is flooded with liquid refrigerant. Air handler 60 blows ambient air across evaporator coil 62 resulting in a cooling of the air since the liquid fluid inside evaporator coil 62 is at a lower temperature than the ambient air. In turn, the refrigerant absorbs heat from the air circulated by air handler 60 as it passes through evaporator coil 62. Depending on various factors, including pressure and the temperature of the ambient air, some or all of the refrigerant may transform to vapor. This warmer refrigerant, typically in liquid and vapor form, returns to vessel 20 through a return line 28.
In certain embodiments, integration between evaporator coil 62 and air handler 60 is accomplished by physically incorporating evaporator coil 62 within the housing of air handler 60 such that room temperature or warmer air blows across the coils of evaporator coil 62. Integration may be performed in various other ways in other embodiments without departing from the scope of the subject invention.
A secondary heat exchanger 70 is included in certain embodiments to ensure that the block of ice formed inside tank 42 forms evenly in shape and depth.
The three modes of operation are typically implemented by a series of valves (not shown) that control the flow of refrigerant through various components, depending on the operating mode currently selected. The operating mode is typically selected by a computer controller and the mode may be selected based on any of a variety of factors including inter alia time of day, external temperature, refrigerant temperature, water temperature in tank 42, and the amount of ice in tank 42.
RTESC system 1 uses a condenser unit 10 to provide cool refrigerant during ice-make mode when it forms a block of ice inside tank 2. RTESC system 1 typically shifts into an ice-make mode during non-peak hours to shift energy load, i.e. electricity usage, to a lower price period. During ice make mode, condenser unit 10 directs cold refrigerant into supply line 12. Inline expansion device 18 lowers the refrigerant fluid pressure and therefore cools the refrigerant before it reaches isolating heat exchanger 16.
The cooler refrigerant in vessel 20 flows to the bottom and is sucked through a supply line 26 and enters coils 44 at the bottom of primary heat exchanger 40. The refrigerant absorbs heat from the relatively warmer surrounding water in ice tank 42 and due to the low boiling temperature of the refrigerant boils and changes to gaseous phase. The refrigerant in gaseous form then rises through coils 44. The refrigerant phase change absorbs heat from the surrounding water which freezes the water and generates a solid block of ice. Effectively, when device 2 operates in ice make mode tank 42 in conjunction with coils 44 form a heat exchanger, transforming cold liquid refrigerant into warm refrigerant vapor and in the process freezing water to make ice.
Refrigerant in vapor form rises through coils 44 where it is piped into the top of vessel 20. The refrigerant in gas form is then sucked out of vessel 20 and piped back to isolating heat exchanger 16 which transforms it back into liquid form.
It may be appreciated that
Refrigerant in vessel 20 is typically in a mixed phase, i.e. partially in vapor phase and partially in liquid phase. The cooler refrigerant in vessel 20 flows to the bottom. The vapor phase refrigerant is sucked out of vapor lines emanating from the top of vessel 20 and enter coils 44 from the top. The vapor phase refrigerant condenses as it descends through coils 44 to form cool liquid phase refrigerant.
Refrigerant pump 50 draws cool liquid refrigerant from the bottom vessel 20 and from the bottom of coils 44 through supply line 26 and pumps it to evaporator coil 62 which is integrated with air handler 60. As the liquid refrigerant passes through evaporator coil 62, inside air handler 60, it absorbs heat. Thus, some of the liquid refrigerant evaporates and a mixture of warm vapor and liquid returns to refrigerant vessel 20 through return line 28. In refrigerant vessel 20 the returned liquid mixes with cold refrigerant at the bottom of refrigerant vessel 20. The warm vapor is siphoned back to primary heat exchanger 40 and enters coils 44 from the top.
In certain embodiments, some of the warm vapor enters secondary heat exchanger 70 and is condensed using cold water from tank 42. Although not further discussed herein, this optional feature can assist to create even formation of ice.
Coils 44 are immersed in ice or cold water and consequently the warm vapor phase refrigerant entering from the top condenses back into a cold liquid and flows to the bottom of coils 44 where it is pumped back out, thus completing the cycle.
Due to the continuous injection of warm vapor phase refrigerant into coils 44 from the top the ice block in tank 42 continuously melts from the top down. This continues until the entire block of ice melts or system 1 switches to ice make mode. Generally, the capacity of cooling is specified in terms of cubic tons of cooling air that can be generated.
It may be appreciated that standard AC units would typically include an expansion device between pump 50 and evaporator coil 62 to generate cool refrigerant. However, device 2, due to the function of primary heat exchanger 40 which stores thermal energy in the form of ice, does not require an expansion device in this mode. This results in a simpler design and eliminates a component that would otherwise draw electrical power.
Direct cooling mode takes advantage of device 2 to provide cooling from condenser unit 10 to air handler 60 without using primary heat exchanger 40. This is advantageous, for example, if cooling is requested but there is no ice or not enough ice in ice tank 42 to warrant using primary heat exchanger 40.
When operating in direct cooling mode, condenser unit 10 directs cold refrigerant through supply line 12 to expansion device 18. Expansion device 18 lowers the refrigerant fluid pressure, resulting in cool gas flowing through isolating heat exchanger 16. This, in turn, cools the vapor and liquid phase refrigerant flowing through isolating heat exchanger in second frigerant loop 7 before it returns to vessel 20.
The cool refrigerant flows to the bottom of vessel 20 where it is sucked out by pump 50 through supply line 26. Refrigerant pump 50 draws cool liquid refrigerant from the bottom vessel 20 and pumps it to evaporator coil 62 which is integrated with air handler 60. As the liquid refrigerant passes through evaporator coil 62, inside air handler 60, it absorbs heat. Some of the liquid refrigerant evaporates, i.e. is transformed to gas or vapor phase and a mixture of warm vapor and liquid returns to refrigerant vessel 20 through return line 28. In refrigerant vessel 20 the returned liquid mixes with cold refrigerant at the bottom of refrigerant vessel 20. The vapor is sucked back to isolating heat exchanger 16 where it is again transformed to cool liquid phase refrigerant, thus completing the cycle.
Upon reading this disclosure, those of skill in the art will appreciate that while particular embodiments and applications have been illustrated and described herein, the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those skilled in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.
| Number | Date | Country | |
|---|---|---|---|
| 63461730 | Apr 2023 | US |
