On-Demand Heat Pump Water Heater

Abstract

The disclosed technology includes an on-demand water heater which uses a heat pump to heat the fluid. The on-demand heat pump water heater can have a low fluid capacity heating chamber which has an inlet and an outlet, a heat pump for heating the fluid, and a controller to control the heat pump and maintain the temperature of the fluid at a predetermined temperature. The on-demand heat pump water heater can include one or more temperature sensors, flow sensors, fluid mixing valves, or supplemental heat sources.

That which is claimed is: 
     
         1 . A water heater comprising:
 a heating chamber configured to hold a fluid;   a temperature sensor configured to detect a temperature of the fluid;   a heat pump configured to heat the fluid;   a first supplemental heat source also configured to heat the fluid, wherein the first supplemental heat source is a resistive heating element; and   a controller configured to:   initially control operation of the heat pump to control the temperature of the fluid based on a predetermined temperature without using the first supplemental heat source;   determine that the temperature of the fluid is below the predetermined temperature during operation of the heat pump; and   enable, based on determining that the temperature of the fluid is below the predetermined temperature during operation of the heat pump, the first supplemental heat source to supplement the heat pump to heat the fluid.   
     
     
         2 . The water heater of  claim 1 , further comprising a second supplemental heat source, wherein the second supplemental heat source is also a resistive heating element. 
     
     
         3 . The water heater of  claim 1 , wherein the first supplemental heating source is provided at a fluid inlet or a fluid outlet of the heating chamber. 
     
     
         4 . The water heater of  claim 1 , further comprising at least one of: a flow sensor. 
     
     
         5 . The water heater of  claim 1 , further comprising a fluid mixing valve. 
     
     
         6 . The water heater of  claim 5 , wherein the controller is a first controller, the water heater further comprising a second controller configured to control at least one of: the fluid mixing valve or the first supplemental heat source. 
     
     
         7 . The water heater of  claim 1 , wherein the heating chamber has a fluid capacity from 0.25 gallons to 15 gallons. 
     
     
         8 . The water heater of  claim 1 , further comprising a ventilation system configured to cool the heat pump. 
     
     
         9 . The water heater of  claim 1 , wherein the temperature sensor comprises a thermocouple or a thermistor. 
     
     
         10 . A method of controlling a fluid heating system, the method comprising:
 detecting, by a temperature sensor, first temperature data of fluid in a heating chamber of the fluid heating system;   in response to determining that the first temperature data indicates fluid temperature is less than a predetermined temperature, outputting, by the controller and to a heat pump, instructions to heat the fluid in the heating chamber;   detecting, by a temperature sensor, second temperature data of the fluid; and   in response to determining the second temperature data indicates the fluid temperature is less than the predetermined temperature, outputting, by the controller and to a supplemental heat source, instructions to heat the fluid in the heating chamber with the supplemental heat source along with the heat pump, wherein the supplemental heat source is a resistive heating element, and wherein the supplemental heat source is configured to heat the fluid.   
     
     
         11 . The method of  claim 10 , further comprising:
 in response to determining that the fluid temperature cannot be maintained at a predetermined temperature setting for a predetermined amount of time based on the first temperature data, outputting, by the controller and to the heat pump, instructions to heat the fluid in the heating chamber.   
     
     
         12 . The method of  claim 10 , further comprising:
 in response to determining that a fluid temperature is outside of a predetermined temperature range, output, by the controller, adjustment instructions to a fluid mixing valve.   
     
     
         13 . A system for heating a fluid, the system comprising:
 a heating chamber;   a heat pump configured to heat the fluid within the heating chamber;   a first supplemental heating source provided at the heating chamber, wherein the first supplemental heat source is a resistive heating element;   a controller; and   a memory having instructions stored thereon that, when executed by the controller, directs the controller to:   receive, at a controller and from a flow sensor, flow data indicative of a detected flow rate associated with a first fluid;   receive, at the controller and from a temperature sensor, temperature data indicative of a detected temperature of a second fluid; and   output a heat pump control signal by the controller in response to determining that (i) the flow data indicates a positive flow or (ii) the temperature data indicates a fluid temperature that is less than a predetermined temperature;   receive, from the temperature sensor, second temperature data; and   output a supplemental heat source control signal in response to determining that the second temperature data indicates the fluid temperature that is still less than the predetermined temperature.   
     
     
         14 . The system of  claim 13 , further comprising a second supplemental heat source, wherein the second supplemental heat source is also a resistive heating element. 
     
     
         15 . The system of  claim 13 , wherein the first supplemental heating source is provided at a fluid inlet or a fluid outlet of the heating chamber. 
     
     
         16 . The system of  claim 13 , further comprising a fluid mixing valve. 
     
     
         17 . The system of  claim 16 , wherein the controller is a first controller, the system further comprising a second controller configured to control at least one of: the fluid mixing valve or the first supplemental heat source. 
     
     
         18 . The system of  claim 13 , wherein the heating chamber has a fluid capacity from 0.25 gallons to 15 gallons. 
     
     
         19 . The system of  claim 13 , further comprising a ventilation system configured to cool the heat pump. 
     
     
         20 . The system of  claim 13 , wherein the temperature sensor comprises a thermocouple or a thermistor.