Variable-Speed HVAC Control for Peak-Demand Comfort
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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 tools to increase sensible capacity and maintain comfort under demand requests.
Innovation Solution
The implementation of a variable-speed compressor and blower system, along with a controller that adjusts the 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 the system to operate at increased sensible capacity while reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the HVAC system operates at high power consumption to maintain comfortable temperatures, then the temperature comfort is improved, but the power consumption increases during peak demand response times
Solution Approach 1:
The evaporator is divided into two separate circuits: a top evaporator circuit with a first compressor and a bottom evaporator circuit with a second compressor. This segmentation allows selective operation of circuits based on cooling demands, enabling the system to reduce power consumption by operating only the top circuit during peak demand response times while still providing adequate cooling through the top evaporator and blower assembly.
Solution Approach 2:
The system implements partial action by deactivating the bottom evaporator circuit and its associated second compressor during peak demand response times. The top evaporator circuit operates independently to provide sufficient cooling for the conditioned space, using only a portion of the system's total capacity. This partial operation reduces overall power consumption while maintaining acceptable temperature comfort levels.
2Use of energy by moving object
If the compressor speed is decreased to reduce power consumption, then the power consumption is reduced, but the sensible capacity decreases
Solution Approach 1:
The system employs variable-speed compressors that can dynamically adjust their operating speeds based on cooling demands and system conditions. The first compressor associated with the top evaporator circuit can operate at optimized speeds to maintain adequate sensible capacity while reducing power consumption during peak demand response times. This dynamic speed adjustment allows the system to balance between power consumption and cooling capacity.
3Productivity
If the air flow rate is increased to improve cooling capacity, then the sensible capacity is improved, but the power consumption increases
Solution Approach 1:
The system uses a single blower assembly to serve both the top and bottom evaporator circuits. During peak demand response times when only the top circuit is active, the blower operates at reduced speeds to provide adequate air flow for the top evaporator's cooling capacity. This partial operation of the blower reduces its power consumption while still delivering sufficient air flow to maintain sensible capacity for the conditioned space.
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 enables HVAC systems to maintain comfortable temperatures during peak demand response times by increasing sensible capacity, reducing power consumption, and providing improved cooling performance 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
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 operate the HVAC system at a predefined setpoint temperature. In response to receiving the demand request, a setpoint temperature associated with the HVAC system is adjusted to the predefined setpoint temperature. A speed of the variable-speed compressor is decreased to a low-speed setting. Based on the decreased speed of the variable-speed compressor, an air-flow rate is determined to provide by the blower. The controllable flow rate of the flow of air provided by the blower is adjusted based on the determined air-flow rate.