Enabling Technologies

Demand response programs require sophisticated control and communication technologies to automatically adjust HVAC loads in response to grid signals. These enabling technologies form the bridge between utility grid operators and building mechanical systems.

Smart Thermostats

Smart thermostats provide the fundamental interface between occupants, HVAC equipment, and demand response signals.

Core Capabilities

Connected thermostats enable automated demand response through:

• Cloud-based communication with utility servers
• Automated setpoint adjustment during DR events
• Pre-cooling or pre-heating strategies before events
• Real-time energy consumption feedback
• Occupancy learning algorithms
• Weather forecast integration

Communication Protocols

Smart thermostats utilize multiple communication methods:

• Wi-Fi connectivity for internet access
• OpenADR 2.0b protocol for standardized DR signals
• Utility-specific APIs and middleware
• ZigBee or Z-Wave for local device networks
• Cellular backup for critical applications

DR Implementation Modes

Direct Load Control Mode: Utility directly adjusts setpoints within pre-authorized ranges (typically ±3-4°F). Override capability preserved for occupant comfort.

Price Response Mode: Thermostat responds to real-time electricity pricing by optimizing setpoints to minimize cost while maintaining comfort constraints.

Event-Based Mode: Responds to discrete DR event signals with pre-programmed load reduction strategies.

Load Modification Strategies

Building Automation System Integration

BAS platforms provide enterprise-level demand response capabilities for commercial and institutional buildings.

Architecture Components

Field Controllers:

• Direct Digital Control (DDC) of AHUs, RTUs, chillers
• Local intelligence for fail-safe operation
• Point trending and alarming
• Communication via BACnet, Modbus, LonWorks

Supervisory Controllers:

• Facility-level coordination of DR strategies
• Optimization algorithms for multi-zone buildings
• Integration with energy management systems
• Historical data logging and analytics

Enterprise Integration:

• OpenADR client software on BAS servers
• EMCS (Energy Management and Control System) integration
• Building-to-grid communication gateway
• Cybersecurity and firewall protection

DR Control Sequences

BAS systems implement complex sequences:

1. Pre-Event Conditioning

   • Maximize thermal storage in building mass 2-4 hours before event
   • Pre-cool to 68-70°F in cooling season
   • Charge ice or chilled water storage systems
   • Verify all equipment operational

2. Event Response

   • Global setpoint adjustment across all zones
   • Chiller staging optimization (reduce to minimum required)
   • Supply air temperature reset (increase 2-4°F)
   • Reduce outdoor air to code minimum
   • Disable non-critical exhaust fans
   • Implement optimal start/stop adjustments

3. Post-Event Recovery

   • Gradual return to normal setpoints over 30-60 minutes
   • Monitor rebound demand to avoid new peak
   • Stagger equipment restart across zones
   • Trend temperature recovery rates

Performance Verification

BAS enables automated M&V (Measurement and Verification):

• Real-time kW demand trending
• Comparison to baseline consumption
• Event participation confirmation to utility
• Savings quantification and reporting
• Commissioning of DR strategies

Load Controllers

Dedicated demand limiting controllers provide focused control for specific equipment or loads.

Smart Load Controllers

HVAC-Specific Controllers:

• Compressor soft-start modules
• Variable frequency drive integration
• Peak demand limiting algorithms
• Time-of-use scheduling
• Load prioritization during constraints

Electrical Load Management:

• Real-time power monitoring at service entrance
• Predictive algorithms to anticipate peak demand
• Automatic load shedding when approaching demand limit
• Configurable load priority hierarchy
• Manual override capabilities

Control Strategies

Fixed Setpoint Limiting: When building demand reaches predetermined kW threshold, shed loads in priority order until demand drops below setpoint.

Sliding Setpoint: Demand limit varies based on time of day, outdoor temperature, or utility rate schedule.

Ideal Rate: Maintains constant power draw over billing period to minimize demand charges. Calculates maximum allowable kW based on time remaining in billing period.

Load Prioritization

Typical load shedding hierarchy:

1. Non-critical plug loads (priority 1)
2. Domestic hot water heating (priority 2)
3. Lighting in non-occupied zones (priority 3)
4. HVAC setpoint adjustment +2°F (priority 4)
5. HVAC setpoint adjustment +4°F (priority 5)
6. Non-critical ventilation fans (priority 6)
7. Auxiliary equipment (priority 7)

Critical loads (data centers, life safety, critical process) excluded from shedding.

Energy Storage Integration

Thermal and electrical energy storage systems enhance DR capabilities by time-shifting loads.

Thermal Energy Storage

Ice Storage Systems:

• Charge during off-peak hours (typically 10 PM - 6 AM)
• Discharge during peak periods to offset chiller operation
• Full storage or partial storage configurations
• 100% demand reduction during discharge mode

Chilled Water Storage:

• Stratified storage tanks maintain temperature differential
• Typical capacity: 4-12 hours of cooling load
• Lower first cost than ice storage
• Larger volume requirements

Building Thermal Mass:

• Pre-cool structure 2-4 hours before DR event
• Concrete, masonry, furniture absorb sensible cooling
• 2-4 hour load shift capability
• No additional equipment required

Battery Energy Storage Systems (BESS)

Grid-Interactive Capabilities:

• Peak shaving: Discharge during demand response events
• Load leveling: Reduce building demand variability
• Backup power during grid outages
• Frequency regulation services

HVAC Integration:

• Power critical HVAC equipment during outages
• Extend chiller operation during peak periods without grid draw
• Reduce demand charges by limiting instantaneous power draw
• Enable participation in wholesale market programs

Typical Sizing:

• Small commercial: 50-200 kWh capacity
• Medium commercial: 200-1000 kWh capacity
• Large commercial: 1-5 MWh capacity
• Duration: 2-4 hours at rated power

Grid-Interactive Efficient Buildings

Grid-interactive buildings actively optimize energy use in response to grid conditions through coordinated control of multiple systems.

Characteristics

Connectivity:

• Real-time communication with grid operators
• Access to grid state information (frequency, voltage, congestion)
• Integration with wholesale electricity markets
• Participation in ancillary services markets

Intelligence:

• Predictive algorithms using weather forecasts
• Machine learning optimization of DR response
• Building energy modeling and digital twins
• Automated fault detection and diagnostics

Flexibility:

• Multiple DR strategies based on grid needs
• Fast response times (seconds to minutes)
• Sustained load reduction capability (hours)
• Bidirectional power flow (with on-site generation/storage)

OpenADR 2.0 Protocol

OpenADR (Open Automated Demand Response) provides standardized communication:

Event Signals:

• Simple signals: Moderate, High, Special load reduction levels
• Price signals: Real-time or time-of-use pricing
• Load dispatch signals: Specific kW reduction targets

VTN/VEN Architecture:

• VTN (Virtual Top Node): Utility/grid operator server
• VEN (Virtual End Node): Building client software
• Push or pull communication models
• Event confirmation and opt-out capability

Implementation Layers:

• Profile A: Simple HTTP/XML for basic DR
• Profile B: Full bidirectional XMPP communication
• Event reports confirm participation and quantify load reduction

Advanced Control Strategies

Model Predictive Control (MPC): Uses building energy model to optimize HVAC operation over 24-48 hour horizon considering:

• Weather forecasts
• Occupancy schedules
• Electricity price forecasts
• Thermal comfort constraints
• Equipment capacity limits

Multi-Objective Optimization: Balances competing priorities:

• Minimize energy cost
• Maintain thermal comfort
• Reduce peak demand
• Extend equipment life
• Support grid reliability

Distributed Energy Resources Coordination: Orchestrates multiple building systems:

• HVAC load flexibility
• Battery charging/discharging
• Solar PV generation curtailment
• Electric vehicle charging control
• On-site generation dispatch

Cybersecurity Considerations

Grid-interactive buildings require robust security:

• Network segmentation isolating HVAC/BAS from IT networks
• Encrypted communication channels (TLS 1.2 or higher)
• Authentication and authorization for all DR signals
• Intrusion detection systems monitoring traffic patterns
• Regular security audits and penetration testing
• Backup local control during communication failures

Performance Metrics

Implementation Roadmap

Successful deployment follows structured progression:

1. Assessment Phase

   • Audit existing control systems
   • Identify controllable loads
   • Evaluate DR program options
   • Estimate load reduction potential

2. Design Phase

   • Select appropriate technologies
   • Develop control sequences
   • Specify communication requirements
   • Plan cybersecurity measures

3. Installation Phase

   • Deploy hardware (controllers, sensors, meters)
   • Configure software and interfaces
   • Establish utility communication
   • Commission control sequences

4. Testing Phase

   • Execute test DR events
   • Verify load reduction achieved
   • Assess occupant comfort impact
   • Tune control parameters

5. Operations Phase

   • Participate in utility DR programs
   • Monitor performance metrics
   • Optimize strategies based on results
   • Maintain and update systems

The integration of these enabling technologies transforms passive buildings into active grid assets, providing substantial value through reduced energy costs and enhanced grid reliability while maintaining occupant comfort.