Method and system for controlling the defrost cycle of a vapor compression system for increased energy efficiency

A vapor compression system comprising:

• a compressor configured to pressurize a refrigerant;
• a condenser operatively coupled to the compressor and configured to receive the compressed refrigerant from the compressor;
• an evaporator operatively coupled to the compressor and configured to return expanded refrigerant to the compressor;
• an expansion valve operatively coupled between the evaporator and the condenser and configured to expand the compressed refrigerant;
• a controller operatively coupled to the compressor and configured to:
• record a heat delivered by the refrigerant and an operational energy of the compressor during an operational period of the vapor compression system;
• determine a cumulative coefficient of performance (CCOP) of the system based on the recorded delivered heat, the recorded operational energy, and a defrost energy consumed by the compressor during a previous defrost period of the vapor compression system;
• and
• initiate a next defrost period of the vapor compression system in response to the CCOP of the system meeting one or more predefined conditions.

A non-transient computer readable medium comprising instructions stored thereon that when executed by a processor cause the processor to:

• receive one or more sensed conditions of a vapor compression system;
• using one or more of the sensed conditions to determine a measure related to a total heat delivered (THD) by the vapor compression system following a completion of a defrosting cycle;
• using one or more of the sensed conditions to determine a measure related to a total electrical energy consumed (TEC-H) by the vapor compression system while delivering heat following the completion of the defrosting cycle;
• store a measure related to a total electrical energy consumed (TEC-D) by the vapor compression system during a previous defrosting cycle;
• determining a cumulative coefficient of performance (CCOP) of the vapor compression system based at least in part on the measure related to a total heat delivered (THD) by the vapor compression system following the completion of a defrosting cycle, the measure related to a total electrical energy consumed (TEC-H) by the vapor compression system while delivering heat following the completion of the defrosting cycle, and the measure related to a total electrical energy consumed (TEC-D) by the vapor compression system during the defrosting cycle;
• and
• initiating a next defrosting cycle of the vapor compression system at a time that is based at least in part on one or more characteristics of the cumulative coefficient of performance (CCOP).