Predictive VRF Control for Peak Demand and Energy Cost Reduction
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Solution Overview
Problem
Existing HVAC systems, particularly variable refrigerant flow (VRF) systems, face challenges in minimizing power consumption, leading to increased energy costs and environmental impact.
Innovation Solution
The implementation of a predictive VRF system that includes an outdoor VRF unit, indoor VRF units, a battery for energy storage, and a predictive VRF controller. This controller optimizes a predictive cost function to determine the optimal amount of electric energy to purchase from the grid and store or discharge from the battery, taking into account energy pricing data and demand charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VRF systems operate powered components (compressor, fan) continuously to maintain building temperature, then temperature control reliability is improved, but power consumption increases
Solution Approach 1:
The system performs preliminary cooling of the building during off-peak hours when electricity rates are lower, storing cooling capacity in the building's thermal mass (walls, floors, furniture). This allows the VRF system to reduce or shut off powered components during peak pricing periods while maintaining temperature control through the stored cooling effect.
Solution Approach 2:
The control system dynamically adjusts the operation of powered components based on real-time electricity pricing signals, weather forecasts, and building thermal characteristics. The system transitions from static continuous operation to dynamic operation that optimizes the balance between temperature control reliability and power consumption at different times.
2Use of energy by moving object
If VRF systems reduce power consumption by operating components less frequently, then energy costs decrease, but temperature control reliability deteriorates
Solution Approach 1:
The system proactively cools the building during off-peak hours to store thermal energy, creating a buffer that maintains temperature control during periods when powered components are reduced or shut off, thereby preserving reliability while reducing energy consumption.
Solution Approach 2:
The control system continuously monitors building temperature, outdoor conditions, and electricity pricing, using this feedback to adjust component operation timing and duration. This ensures that reduced operation does not compromise temperature control reliability while maximizing energy savings.
3Reliability
If VRF systems operate at full capacity during peak demand periods, then temperature control is maintained, but demand charges increase
Solution Approach 1:
The system shifts cooling load to off-peak periods by storing thermal energy in the building structure, thereby reducing peak demand and avoiding high demand charges while maintaining temperature control through the stored cooling capacity during peak periods.
Solution Approach 2:
The system operates powered components in periodic cycles aligned with electricity pricing structures, intensifying operation during off-peak periods and reducing operation during peak periods, thereby smoothing demand and reducing peak demand charges while maintaining overall temperature control.
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
The predictive VRF system effectively reduces energy costs by optimizing energy usage based on real-time pricing and demand, thereby minimizing power consumption and environmental impact.
Implementation Method 1
The battery is configured to store electric energy and discharge the stored electric energy for use in powering the powered VRF components
Implementation Method 2
The VRF system includes one or more photovoltaic panels configured to collect photovoltaic energy
Implementation Method 3
The outdoor VRF unit includes a refrigeration circuit including a heat exchanger, a compressor configured to circulate the refrigerant through the heat exchanger
Data Source
AI summary
An air conditioning system for a building includes an air conditioning unit including one or more powered air conditioning components configured to apply heating or cooling to a refrigerant and an air conditioning controller. The air conditioning controller is configured to cause a determined amount of power to be received at the one or more powered air conditioning components for use in powering the air conditioning unit and control the one or more powered air conditioning components by determining a refrigerant temperature setpoint for the refrigerant or a supply air temperature setpoint for supply air output by the air conditioning system based on the determined amount of power.