HVAC Demand Limiting With Feedback Control and Pre-Cooling

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Solution Overview

Problem

Building management systems (BMS) lack integration with smart grid components and data, limiting their ability to efficiently manage energy consumption and reduce costs, especially during peak usage times.

Innovation Solution

A method and system for controlling HVAC power consumption using a feedback controller that adjusts operation based on energy use setpoints, integrating with smart grid components to optimize energy usage and reduce demand through demand limiting strategies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If demand limiting is utilized to reduce energy costs during peak usage times, then energy costs are reduced, but building temperature control may be compromised

Engineering Contradiction:

Improveenergy costsVSAvoidbuilding temperature control

Core Design Contradiction:

Use of energy by stationary objectVSTemperature

Solution Approach 1:

The system performs pre-cooling of the building before demand limiting periods begin, storing thermal energy in the building structure (walls, floors, furniture). This preliminary action allows the building to maintain comfortable temperatures during peak periods without active HVAC operation, resolving the contradiction between reducing energy costs and maintaining temperature control.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors building temperature, outdoor conditions, and energy pricing signals, using feedback control to adjust pre-cooling strategies and demand limiting operations. This ensures temperature constraints are maintained while optimizing energy cost reduction during peak usage times.

Inventive Principle:

Principle #23Feedback

2Use of energy by moving object

If HVAC system operation is reduced during demand limiting periods, then energy consumption is reduced, but temperature setpoint maintenance becomes difficult

Engineering Contradiction:

ImproveHVAC energy consumptionVSAvoidtemperature setpoint maintenance

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The system pre-cools or pre-heats the building before demand limiting periods, storing thermal energy in the building mass. This preliminary action creates a thermal buffer that maintains temperature setpoints during reduced HVAC operation, resolving the contradiction between reducing energy consumption and maintaining temperature precision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts temperature setpoints and pre-cooling durations based on outdoor temperature predictions, building thermal characteristics, and energy pricing signals. This parameter optimization maintains temperature setpoint maintenance while minimizing HVAC energy consumption during demand limiting periods.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by stationary object

If building pre-cooling is performed, then energy costs during peak periods are reduced, but energy consumption increases before the demand limiting period

Engineering Contradiction:

Improvepeak period energy costsVSAvoidpre-cooling energy consumption

Core Design Contradiction:

Use of energy by stationary objectVSUse of energy by moving object

Solution Approach 1:

The system performs pre-cooling only when predictive algorithms determine it will result in net energy savings, considering factors such as outdoor temperature forecasts, building thermal mass, and peak period pricing signals. This selective preliminary action reduces peak period energy costs while minimizing unnecessary pre-cooling energy consumption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts pre-cooling strategies based on real-time and forecasted conditions, optimizing the balance between pre-cooling energy consumption and peak period energy cost reduction. This dynamic adaptation ensures pre-cooling is performed only when energetically beneficial.

Inventive Principle:

Principle #15Dynamics

4Productivity

If HVAC system is integrated with smart grid components, then energy management efficiency is improved, but system complexity increases

Engineering Contradiction:

Improveenergy management efficiencyVSAvoidsystem integration complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The building management system is designed to perform multiple functions: traditional HVAC control, demand response participation, energy optimization, and smart grid communication. This multi-functionality improves energy management efficiency while avoiding the need for separate dedicated systems, thereby limiting the increase in overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The integrated system uses feedback from smart grid pricing signals and building performance data to automatically optimize HVAC operation. This automated feedback control improves energy management efficiency while reducing the need for complex manual intervention and monitoring infrastructure.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9322566B2Systems and methods for controlling energy use during a demand limiting period

Publication Date: 2016.04.26 JOHNSON CONTROLS TECHNOLOGY CO

AI summary

Systems and methods for limiting power consumption by a heating, ventilation, and air conditioning (HVAC) subsystem of a building are shown and described. A feedback controller is used to generate a manipulated variable based on an energy use setpoint and a measured energy use. The manipulated variable may be used for adjusting the operation of an HVAC device.