HVAC Setpoint Trajectory Control for Peak Power Budgeting

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Solution Overview

Problem

Building management systems struggle to efficiently manage power consumption during peak usage times, particularly in HVAC systems, as existing technologies lack effective methods to optimize cooling power use without compromising comfort and increasing energy costs.

Innovation Solution

A controller processes cooling power use data to calculate deferred cooling power and applies a linear operator to transform temperature setpoints, optimizing power consumption by adjusting setpoints during limited power periods, thereby minimizing energy costs while maintaining comfort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If demand limiting is utilized during peak usage times to reduce energy costs, then energy costs are reduced, but cooling power use and occupant comfort are compromised

Engineering Contradiction:

Improveenergy costsVSAvoidcooling power use

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The system performs pre-cooling of the building during off-peak hours before the limited power period begins. By lowering the temperature setpoint in advance (e.g., from 72°F to 68°F), the building's thermal mass stores cooling energy, allowing the HVAC system to operate at reduced capacity during peak periods while still maintaining comfortable temperatures for occupants.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically changes the temperature setpoint parameter based on the timing relative to limited power periods. During pre-cooling, the setpoint is lowered below the normal comfort range; during the limited power period, the setpoint is raised or the system operates at reduced capacity; after the period, the setpoint returns to normal. This time-varying parameter adjustment resolves the contradiction between energy reduction and comfort maintenance.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If temperature setpoints are adjusted to optimize cooling power use, then energy costs are reduced, but occupant comfort is compromised

Engineering Contradiction:

Improvecooling power useVSAvoidoccupant comfort

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The system adjusts temperature setpoints in advance of limited power periods by pre-cooling the building. This preliminary action stores thermal energy in the building's mass, allowing subsequent temperature adjustments during peak periods to reduce cooling power consumption while the stored thermal energy maintains acceptable comfort levels for occupants.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses a linear operator trained on historical data to predict the relationship between temperature setpoint adjustments and resulting cooling power consumption. This feedback mechanism allows the system to make informed setpoint adjustments that optimize energy reduction while predicting and maintaining acceptable comfort outcomes, thereby resolving the contradiction between energy savings and comfort.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8755943B2Systems and methods for controlling energy use in a building management system using energy budgets

Publication Date: 2014.06.17 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 mathematical linear operator is found that transforms the unused or deferred cooling power usage of the HVAC system based on pre-determined temperature settings to a target cooling power usage. The mathematical operator is applied to the temperature settings to create a temperature setpoint trajectory expected to provide the target cooling power usage.