Variable-Speed HVAC Control for Peak Demand Sensible Cooling
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Solution Overview
Problem
HVAC systems face challenges in maintaining comfortable temperatures during peak demand response times while reducing power consumption, as existing technologies lack effective methods to increase sensible capacity and maintain comfort under restricted operating conditions.
Innovation Solution
The implementation of a variable-speed compressor and blower system, along with a controller that adjusts compressor speed and air flow rate to increase the sensible heat ratio, and the use of a face-split evaporator to deactivate the bottom evaporator circuit for evaporative cooling, allowing for improved sensible capacity and reduced power consumption during peak demand response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the HVAC system operates at high power consumption to maintain comfortable temperatures, then the temperature control is improved, but the power consumption increases during peak demand response times
Solution Approach 1:
The system dynamically adjusts the ratio of air flow rate to cooling capacity by varying blower speed and compressor tonnage in response to demand requests. The blower speed is adjusted to maintain a higher CFM/ton ratio during peak demand response times, which improves sensible capacity and allows the system to meet temperature setpoints while consuming less power.
Solution Approach 2:
The system changes operating parameters including CFM/ton ratio, blower speed, and compressor tonnage to optimize performance during peak demand response times. By adjusting these parameters, the system can operate at reduced power consumption while still maintaining comfortable temperatures through improved sensible capacity.
2Use of energy by moving object
If the compressor speed is reduced to decrease power consumption, then the power consumption is reduced, but the cooling capacity decreases
Solution Approach 1:
The system dynamically adjusts the relationship between blower speed and compressor tonnage to maintain effective cooling capacity even when compressor speed is reduced. By coordinating blower speed adjustments with compressor tonnage changes, the system optimizes the CFM/ton ratio to preserve sensible capacity while reducing overall power consumption.
3Productivity
If the air flow rate is increased to improve sensible capacity, then the sensible capacity is improved, but the power consumption increases
Solution Approach 1:
The system changes the CFM/ton ratio parameter by adjusting blower speed relative to compressor tonnage. This parameter change improves sensible capacity without proportionally increasing power consumption, as the system operates at optimized blower speeds that balance airflow delivery with energy usage during peak demand response times.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the HVAC system's ability to maintain comfortable temperatures while satisfying peak demand response requirements by increasing sensible capacity and reducing power consumption, providing more effective cooling and dehumidification compared to previous technologies.
Implementation Method 1
a variable-speed compressor configured to compress refrigerant flowing through the HVAC system
Implementation Method 2
The top evaporator circuit is configured to transfer heat from a first portion of a flow of air passing across the top evaporator circuit to refrigerant in the top evaporator circuit. The bottom evaporator circuit is configured to transfer heat from a second portion of the flow of air passing across the bottom evaporator circuit to refrigerant in the bottom evaporator circuit.
Implementation Method 3
A first portion of the liquid condensate formed on a surface of the top evaporator circuit is allowed to fall on a surface of the bottom evaporator circuit such that the second portion of the flow of air is evaporatively cooled by the first portion of the liquid condensate.
Data Source
AI summary
An HVAC system includes a variable-speed compressor which compresses refrigerant flowing through the HVAC system, a blower which provides a flow of air through the HVAC system at a controllable flow rate, and a controller communicatively coupled to the variable-speed compressor and the blower. The controller receives a demand request which includes a command to reduce power consumption by the HVAC system. In response to receiving the demand request, a speed of the variable-speed compressor is decreased and the controllable flow rate of the flow of air provided by the blower is adjusted. Accordingly, a ratio of the first flow rate to the decreased tonnage of cooling is increased to a predefined value, and a power consumption of the HVAC system is decreased by at least a predefined percentage associated with the demand request.