Systems and methods for supplying stored heat to a vapor compression system
A vapor compression system includes a primary loop, an auxiliary loop, and first and second valves. The primary loop includes an indoor heat exchanger, an outdoor heat exchanger, and a compressor. The first valve is positionable in first and second positions, such that the first valve fluidly connects the indoor heat exchanger to the compressor in the first position. The second valve is positionable in third and fourth positions, such that the second valve fluidly connects the indoor and outdoor heat exchangers in the third position. The auxiliary loop includes a thermal storage unit, a supply duct, and a return duct. The supply duct fluidly connects a thermal storage unit exit to the indoor heat exchanger when the first valve is in the second position. The return duct fluidly connects a thermal storage unit inlet to the indoor heat exchanger when the second valve is in the fourth position.
1 . A vapor compression system comprising:
a primary loop comprising:
an indoor heat exchanger;
an outdoor heat exchanger; and
a compressor operable to compress a refrigerant;
a first valve selectively positionable in a first position and a second position, wherein the first valve fluidly connects the indoor heat exchanger to the compressor in the first position;
a second valve selectively positionable in a first position and a second position, wherein the second valve fluidly connects the indoor heat exchanger to the outdoor heat exchanger in the first position when in a heating mode and a cooling mode; and
an auxiliary loop comprising:
a thermal storage unit having an inlet, an exit, and a heating duct extending therebetween, wherein the thermal storage unit includes a cavity filled with a plurality of particles, wherein the thermal storage unit is operable at temperatures of up to 1200 F;
a supply duct fluidly connecting the exit of the thermal storage unit to the indoor heat exchanger when the first valve is in the second position; and
a return duct fluidly connecting the inlet of the thermal storage unit to the indoor heat exchanger when the second valve is in the second position when in an auxiliary heating mode; and
a defrost loop comprising:
a defrost duct fluidly connected between the thermal storage unit and the outdoor heat exchanger; and
a defrost valve positioned in the supply duct and operable to selectively permit refrigerant to flow through the defrost duct,
wherein the defrost valve is positionable in a first position to fluidly connect the outdoor heat exchanger to the thermal storage unit to permit refrigerant to flow in the defrost loop therebetween,
wherein the second valve fluidly connects the outdoor heat exchanger to the thermal storage unit in the second position when in a defrost mode, wherein the refrigerant is diverted through the auxiliary loop when the first valve is in the second position and the second valve is in the second position when in a defrost mode.
2 . The vapor compression system of claim 1 further comprising a reversing valve operable to selectively configure the primary loop to operate in a cooling mode, in which the compressor provides the refrigerant to the outdoor heat exchanger, or a heating mode, in which the compressor provides the refrigerant to the indoor heat exchanger.
3 . The vapor compression system of claim 1 , wherein the thermal storage unit further comprises a heating element operable to raise a temperature of the plurality of particles.
4 . The vapor compression system of claim 3 , wherein the heating element heats the plurality of particles to a temperature of between 800 and 1200 F.
5 . The vapor compression system of claim 3 , wherein the heating element is powered by renewably generated electricity or off-peak electricity.
6 . The vapor compression system of claim 1 , wherein the plurality of particles are sand particles.
7 . The vapor compression system of claim 1 , wherein the plurality of particles surround the heating duct to permit heat transfer therebetween.
8 . A method of retrofitting an existing vapor compression system with an auxiliary heating loop having a thermal storage unit including a cavity filled with a plurality of particles, the vapor compression system including an indoor heat exchanger, an outdoor heat exchanger, and a compressor fluidly connected between the indoor and outdoor heat exchangers, the method comprising:
fluidly connecting a first path of a first valve between the indoor heat exchanger and the compressor of the existing vapor compression system;
fluidly connecting a first path of a second valve between the indoor heat exchanger and the outdoor heat exchanger of the existing vapor compression system;
fluidly connecting a supply duct between the thermal storage unit and a second path of the first valve, wherein the thermal storage unit is operable at temperatures of up to 1200 F;
fluidly connecting a return duct between a second path of the second valve and the thermal storage unit,
fluidly connecting a defrost duct between the thermal storage unit and the outdoor heat exchanger; and
fluidly connecting a defrost valve between the supply duct and the defrost duct, the defrost valve operable to selectively permit refrigerant to flow through the defrost duct, wherein the defrost valve is positioned in the supply duct,
wherein the defrost valve is positionable to fluidly connect the outdoor heat exchanger to the thermal storage unit to permit refrigerant to flow in a defrost loop therebetween when in a defrost mode,
wherein the second path of the second valve fluidly connects the outdoor heat exchanger to the thermal storage unit when in a defrost mode, wherein the refrigerant is diverted through the auxiliary loop in the defrost mode when the first valve is in a second position fluidly connecting the supply duct to the thermal storage unit and the second valve is in the second position connecting the return duct to the outdoor heat exchanger.
9 . The method of claim 8 , wherein fluidly connecting the return duct comprises connecting the return duct between the second valve and the thermal storage unit such that the indoor heat exchanger is positioned above the thermal storage unit such that flow of a refrigerant through the return duct is driven by gravity.
10 . The method of claim 8 , wherein fluidly connecting the return duct comprises fluidly connecting a pump in the return duct between the second valve and the thermal storage unit.
11 . A controller for a vapor compression system including a primary loop and an auxiliary loop, the primary loop including an indoor heat exchanger, an outdoor heat exchanger, and a compressor, the auxiliary loop including a supply duct, a return duct, a thermal storage unit having a heating duct fluidly connecting the supply duct and the return duct, a defrost duct fluidly connected between the thermal storge unit and the outdoor heat exchanger, a defrost valve positioned within the supply duct and operable to selectively permit refrigerant to flow through the defrost duct, the thermal storage unit including a cavity filled with a plurality of particles, the thermal storage unit operable at temperatures of up to 1200 degrees Fahrenheit, the primary and auxiliary loops being connected by first and second valves, the controller comprising:
a processor; and
a memory storing instructions that program the processor to:
operate the vapor compression system to provide a flow of refrigerant through the primary loop;
determine if a condition has been satisfied by determining that a temperature of the outdoor heat exchanger has fallen below a threshold value; and
adjust a position of the first valve to fluidly connect the supply duct to the outdoor heat exchanger and a position of the second valve to fluidly connect the outdoor heat exchanger to the return duct to and divert the refrigerant through the auxiliary loop when the condition is satisfied.
12 . The controller of claim 11 , wherein the instructions program the processor to:
determine if a second condition has been satisfied; and
adjust the position of the first valve to fluidly connect the indoor heat exchanger to the supply duct and adjust the position of the second valve to fluidly connect the indoor heat exchanger to the return duct when the second condition has been satisfied.
13 . The controller of claim 12 , wherein the instructions program the processor to determine if a third condition has been satisfied by determining that a utility high demand event has occurred.
14 . The controller of claim 12 , wherein the instructions program the processor to determine if a third condition has been satisfied by determining that high stage heating is needed.