Designing Potential Energy Based Emergency Power Systems for High Rise Buildings: A Comprehensive Guide

Designing potential energy based emergency power systems for high rise buildings is a critical aspect of ensuring the safety and functionality of these structures during power outages. This comprehensive guide will delve into the technical details, physics principles, and practical considerations involved in creating a robust and reliable emergency power system.

Codes and Standards: The Foundation of Design

The design of potential energy based emergency power systems for high rise buildings is governed by a set of codes and standards that ensure compliance with safety and performance requirements. These include:

1. NFPA 70-2017: National Electrical Code (NEC): This code provides the minimum requirements for electrical installations, including emergency power systems.
2. NFPA 99-2015: Health Care Facilities Code: This code sets the standards for emergency power systems in healthcare facilities, which are often found in high rise buildings.
3. NFPA 101-2015: Life Safety Code: This code addresses the safety of building occupants, including the requirements for emergency power systems.
4. NFPA 110-2016: Standard for Emergency and Standby Power Systems: This standard specifically outlines the design, installation, and maintenance requirements for emergency power systems.

Adherence to these codes and standards is essential to ensure the safety and reliability of the emergency power system.

Generator Sizing: Calculating the Critical Load

The size of the generator(s) required for a high rise building’s emergency power system is determined by the critical loads that need to be supported during an outage. These critical loads can include:

1. Lighting: Emergency lighting is essential for safe evacuation and maintaining essential operations.
2. Elevators: Elevators are crucial for evacuating occupants, especially those with mobility challenges.
3. HVAC Systems: Maintaining temperature and air quality is vital for the comfort and safety of building occupants.
4. Life Safety Systems: This includes fire alarm systems, smoke control systems, and other critical safety equipment.

To calculate the required generator size, designers must perform a detailed load analysis using the following formula:

Generator Size (kW) = Total Critical Load (kW) + Safety Factor (typically 20-30%)

The safety factor accounts for potential increases in load and ensures the generator can handle the maximum expected load during an emergency.

Transfer Switches: Seamless Transition to Emergency Power

Automatic transfer switches (ATS) play a crucial role in the emergency power system by automatically switching from the normal power source to the emergency power source during an outage. The transfer time must be less than 10 seconds to meet the NEC requirements for emergency systems.

The selection of the ATS should consider factors such as:

1. Voltage and Amperage Rating: The ATS must be rated for the voltage and current requirements of the building’s electrical system.
2. Switching Speed: The ATS must be capable of transferring the load within the required 10-second timeframe.
3. Bypass Functionality: The ability to bypass the ATS for maintenance or testing is essential for ensuring the system’s reliability.

Proper installation and testing of the ATS are critical to ensure a seamless transition to emergency power during an outage.

Fuel Storage: Ensuring Continuous Operation

Emergency power systems for high rise buildings often rely on diesel generators, which require on-site fuel storage. The fuel storage capacity should be sufficient to support the generator(s) for at least 72 hours of continuous operation.

The design of the fuel storage system should consider the following factors:

1. Fuel Tank Size: The tank size should be calculated based on the generator’s fuel consumption rate and the required runtime.
2. Fuel Delivery and Refueling: Provisions for fuel delivery and refueling during an extended outage should be made.
3. Fuel Quality and Maintenance: Regular fuel testing and maintenance are essential to ensure the fuel’s integrity and the generator’s reliable operation.

Adherence to applicable codes and standards, such as NFPA 30: Flammable and Combustible Liquids Code, is crucial for the safe design and installation of the fuel storage system.

Maintenance and Testing: Ensuring Readiness

Regular maintenance and testing of the emergency power system are critical to ensure its proper function during an emergency. NFPA 110-2016 recommends the following testing and maintenance schedule:

1. Weekly Testing: This includes a brief (5-30 minutes) operation of the generator under load to verify its functionality.
2. Monthly Testing: More comprehensive testing, including load bank testing, to ensure the system’s readiness.
3. Annual Testing: Thorough testing, including a full-load test, to verify the system’s performance and identify any potential issues.

Maintenance activities should include:

1. Fuel System Maintenance: Checking for fuel leaks, replacing filters, and ensuring fuel quality.
2. Generator Maintenance: Performing oil changes, checking belts and hoses, and inspecting the generator’s components.
3. Transfer Switch Maintenance: Verifying the proper operation of the automatic transfer switch.

Maintaining detailed records of all testing and maintenance activities is essential for demonstrating compliance with applicable codes and standards.

Physical Components: Selecting the Right Equipment

The emergency power system for a high rise building will include various physical components, such as:

1. Generators: The generator(s) should be selected based on the calculated critical load, fuel type, and environmental conditions.
2. Transfer Switches: Automatic transfer switches, as discussed earlier, are a critical component of the system.
3. Fuel Storage and Delivery: Fuel tanks, piping, and pumps are necessary for the fuel storage and delivery system.
4. Electrical Distribution Equipment: This includes switchgear, transformers, and distribution panels to deliver the emergency power to the building’s electrical system.

The selection of these components should be based on the specific requirements of the building, the expected load, and the environmental conditions. Proper sizing, rating, and compatibility of these components are essential for the system’s reliable operation.

Design Criteria: Documenting the Requirements

The design criteria for the emergency power system should be clearly documented and communicated to all stakeholders in the project. These criteria should include:

1. Expected Load: The critical loads that need to be supported during an emergency, including their power requirements.
2. Transfer Time: The maximum allowable transfer time from normal power to emergency power, as per the NEC requirements.
3. Fuel Storage Capacity: The required fuel storage capacity to support the generator(s) for the desired runtime.
4. Maintenance Requirements: The scheduled maintenance activities and testing procedures to ensure the system’s readiness.

By documenting these design criteria, the project team can ensure that the emergency power system is designed, installed, and maintained to meet the specific needs of the high rise building.

Construction Documents: Ensuring Compliance

The construction documents for the emergency power system should include detailed drawings and specifications for all components. These documents should be reviewed and approved by the authority having jurisdiction (AHJ) to ensure compliance with all applicable codes and standards.

The construction documents should include:

1. Electrical Drawings: Showing the layout and interconnections of the generators, transfer switches, and electrical distribution equipment.
2. Mechanical Drawings: Depicting the fuel storage and delivery system, including the tank, piping, and pumps.
3. Specifications: Detailing the technical requirements and performance characteristics of each component.

The AHJ’s review and approval of these construction documents are crucial to ensure the emergency power system meets all safety and performance requirements.

By following this comprehensive guide, designers can ensure that the potential energy based emergency power system for a high rise building is properly sized, installed, and maintained to meet the needs of the building and its occupants during an emergency.

Reference:

1. NFPA 70-2017: National Electrical Code (NEC)
2. NFPA 99-2015: Health Care Facilities Code
3. NFPA 101-2015: Life Safety Code
4. NFPA 110-2016: Standard for Emergency and Standby Power Systems
5. NFPA 30: Flammable and Combustible Liquids Code