Airports are often massive and complex buildings with a wide range internal process loads, high solar loads, and transient occupant. Creating an energy model for an Airport on any platform is challenging and requires a wide range of information specific to this building type. Modeling an Airport will be a team effort and we recommend utilizing the Internal Chat Feature to connect the entire design team to energy model so that each can contribute their unique domain knowledge into the model.
Benchmarking a project is the first step to understanding and settings energy reduction goals. For an Airport this requires understanding the unique mix of uses the building will include. Example of use types that may be included in an airport are: dining, retail, ticket counters, waiting rooms, corridors, offices, baggage claim, and more. Several resources are available from the Transportation Research Board (TRB), including details on the methodology used, and academic research papers.
From TRB - Results from ACRP 09-10 Study, Data from 10 actual airports
From TRB - EUI breakdown by use type and process load
Modeling an Airport is possible via the cove.tool platform, which will allow teams to view the whole building EUI, daylight metrics such as sDA and ASE, optimize for cost vs. energy, and finally preform the building load model!
Step 1: Project Basics
Create a new project and on the Projects Page select one of the eight standard building types. For an Airport, Retail or Hotel work well. Next enter the project location and modify the energy code if the project is being design to a higher than the local minimum energy code.
Select save and continue to next import or create the building geometry. Once done navigate to the Baseline Energy Page. For the purpose of this workflow we will assume that the automated Envelope Performances match the design intent and do not need to be modified.
Step 2: Usage and Schedules Inputs
Many of the unique aspects of each airport project will be input into the Usage and Schedule Tab of the Baseline Energy Model. Each of the key inputs are described below and recommended values and resources provided.
The interior lights are defined as a power per area with units of w/ft2 or w/m2. This is a peak power input that will depend on the building design and ratio between different use types. A typical references for initial lighting power density (LPD) is ASHRAE 90. 1 Section 9. For the 2019 version Table 9.5.1 provides building type assumptions, given that Airport is not an available option, using Transportation at 0.5 w/ft2 is recommended. Note, this represents a mix of the occupied, and back of house spaces within the airport.
Alternative - One alternative to estimating the overall LPD is to make use of drawing.tool to define individual rooms with templates. This workflow allows each room of a model to be assigned a specific input, which will then be area-weighted averaged into the Baseline Energy Model. This is a great option if space planing has been completed for the project and areas that will be corridors, waiting rooms, dining, etc. have been defined.
The appliance or equipment use within a building is defined as a power per unit with units of w/ft2 or w/m2. There is a lot of different equipment within an airport. Examples include laptops and phones of passengers, flight information screens, retail displays, commercial kitchens, and even the baggage handling system. Each room use type within an airport can range from a low equipment power density (EPD) in rooms such as corridors or waiting areas, to high in kitchens or baggage handing rooms. Given the larger total area associated with low EPD rooms the resulting value based on the unique mix is expected to be on the lower end. Unfortunately, there are no standard values that can be used for EPD of buildings as these are determined based on empirical studies and not controlled by codes or standards. A good starting point would be 1 w/ft2.
Alternative - Just like lighting power density, by using the drawing.tool to define the use of each room of a building we can automatically produce an area-weight average EPD value for the Baseline Energy Model.
Regardless of the method used, cove.tool highly recommends consulting the project's mechanical engineer who will be able to advise on the appropriateness of all energy model inputs for the project.
Airports occupancy is an especially difficult value to determine due to the transient nature of the majority of persons using the building. For many buildings types the occupancy value would be the Full Time Equivalent or FTE of the building, however for an airport this does not capture the passengers.
To determine the occupancy for an airport it is helpful to refer to the occupancy schedule and how this will be applied. The schedule essentially works on simple multiplication of the total occupant * the percent expected, so if the total occupants defined is 100 and the schedule is set to 50% at 8am, there will be 50 people present in the energy model at that time. The total value we define should be the peak per hour.
The occupancy schedule will depend on the operations of the airport. As many airports are 24/7 or close to it the hours of occupancy will look similar to the example below. Given additional information on typical flight departure and arrival times the design team can refine this schedule further.
Step 3: Building Systems
An airport can have many different mechanical systems all being used in different areas of the airport. For example the back of house baggage handling spaces may have single zone equipment doing only spot heating and cooling where required. While the main passenger spaces may have large variable air volume systems delivery ventilation and comfort cooling to occupants. Given the wide variety of systems that could be in use, it's advisable to apply a System Type to the model that is a good approximation of many. VAV w/ Reheat, with Gas Boiler and Water Cooled Chiller is a good starting point for an Airport. If the project is being connected to a central utility plant as part of an airport campus us this guide for district energy systems.