Handbook for Evaluating Emissions and Costs of APUs and Alternative Systems (2012)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

1 C h a p t e r 1 Amid growing concerns regarding airport-related emissions, and in light of rising fuel costs, airport operators and airlines have been investigating various options for reducing aircraft- related emissions and fuel consumption. Aircraft are one of the primary sources of emissions at airports, and thus, there is widespread interest in identifying methods to reduce aircraft- related emissions. One of the options that has been implemented at commercial service airports throughout the United States is the provision of ground-based power, heating, and cooling sys- tems to reduce the use of aircraft auxiliary power units (APUs) which combust jet fuel and hence are a source of pollutant emissions. This Handbook will aid the practitioner to better understand the types of alternative systems available and the associated emissions, energy consumption, and cost implications of implementing these alternative systems at airports. 1.1 Background An APU is an engine located on a vehicle that provides energy for functions other than pro- pulsion or movement. APUs are found on most large commercial service aircraft, as well as some trucks. Most commercial aircraft engines have large, heavy rotors that must be accelerated to a high rotational speed to provide sufficient air compression for self-sustaining operation. The primary purpose of an aircraft APU is to provide power to start the main engines. Over time, aircraft APUs have evolved to also provide air conditioning or heat for cabin comfort, and elec- tric power for cabin lights and avionics. APUs were first used on piston-powered aircraft in the early 1900s. Beginning in the 1960s, most commercial service aircraft were equipped with an APU. The invention of the APU has independently from ground facilities (i.e., by providing power to start the main aircraft engines). Widespread adoption of APUs has allowed aircraft to fly to remote areas and to serve remote communities where ground power is not readily available. An aircraft APU is essentially a turbine engine that uses the same fuel as the main aircraft engines. In general, the APU consists of a compressor section, a turbine section, and an accessory drive section. The APU is located in the tail section of most aircraft (Figure 1), but the APU can also be located elsewhere on the aircraft. The APU supplies electric power to the aircraft systems and cooled/heated air for the cabin when the aircraft is parked. APU use times can range from approximately 20–25 minutes for quick-turn passenger aircraft to several hours for cargo aircraft when ground infrastructure sys- tems (i.e., ground power and pre-conditioned air systems) are not available. During the winter at Introduction and Background

2 handbook for evaluating emissions and Costs of apUs and alternative Systems cold-temperature airports, pilots will often operate APUs for extended periods to prevent water onboard the aircraft from freezing. In order to reduce aircraft APU usage, and hence emissions of both criteria pollutants and greenhouse gases, some form of ground-based power must be available. In most climatic condi- tions, the ground-based power system must also be coupled with heating, ventilation, and air conditioning (HVAC) capabilities to reduce aircraft APU use. It is important to note that even in those situations when ground-based power and HVAC infrastructure are available at an airport, aircraft pilots will typically use APUs upon arriving at an aircraft parking position and before departing the aircraft parking position. It is estimated that APUs are used for approximately 2 minutes when aircraft first arrive at a parking position and for approximately 5 minutes prior to push-back. The HVAC portion of a ground-based alternative system is referred to as pre-conditioned air (PCA). The power requirements of aircraft are primarily 400 hertz, but some smaller aircraft require 28.5 volts direct current (VDC) power. Thus, some ground power systems at airport terminals are capable of providing both 400 hertz and 28.5 VDC power. When new passenger boarding bridges (commonly referred to as gates) are constructed, they often include some form of an alternative system to provide electric power and PCA to parked aircraft. Similarly, in response to airline needs, some airport operators are retrofitting existing gates with these alternative systems, or assisting the airlines with the installation of such systems at the gates. As discussed in Chapter 3 of this Handbook, alternative systems generally have less pronounced effects on local air quality and global emissions of greenhouse gases when compared with aircraft APUs. SOURCE: Aerospaceweb, 2010 Figure 1. Typical aircraft APU.

Introduction and Background 3 1.2 APUs and Types of Alternative Ground Infrastructure Systems When evaluating different ground-based power and PCA systems, the following types of information are needed: • The temperatures at which heated or cooled air is needed (i.e., ambient temperatures); • Aircraft types that would be using the ground-based power and PCA systems; and • The characteristics and conditions of the electrical and HVAC systems at the airport. The first two items form the basis for examining the capabilities of the alternative system while the later is used to determine which category of alternative system (i.e., central or point of use) is most cost effective. The approach to determining the cost effectiveness of various alternative systems will vary based on the specific conditions at an airport and thus is beyond the scope of this Handbook; users should consult their asset management and facility managers to under- stand the cost effectiveness of these alternative systems relative to their specific conditions. Some limited information regarding costs and operational issues associated with alternative systems is presented in Chapter 4. As noted earlier, APUs supply cooled and heated air to the aircraft cabin. Thus, when consid- ering alternative systems, airport operators need to identify the ambient temperatures at which aircraft require heated or cooled air. Airport operators should consider guidance developed by the FAA in support of the Voluntary Airport Low Emissions (VALE) grant program, which specifies the following climatic conditions related to aircraft APUs and alternative systems (FAA 2010a; FAA 2010b): • Cold conditions (e.g., under 45°F)—aircraft requires heating and electric power • Neutral conditions (the FAA’s VALE program specifies 45 to 50°F)—aircraft requires only electric power (no heating or cooling) • Hot conditions (e.g., greater than 50°F)—aircraft requires cooling and electric power Although there are different manufacturers of APUs (e.g., Honeywell, Hamilton Sundstrand, etc.), each with different technical specifications, the overall technology is similar from manu- facturer to manufacturer. The main differences between the various APUs are related to their load ratings for electric power and PCA which are dependent on the type and size of aircraft serviced by the APU. Some APUs are built specifically for certain aircraft types, while others can be installed in different aircraft types within the same size category. Table 1 provides a summary of selected APUs and associated aircraft types grouped by aircraft category. Since ACRP Project 02-25 is focused on the commercial aircraft fleet in the United States, Table 1 does not include military aircraft or general aviation aircraft. In lieu of the use of APUs, alternative ground infrastructure systems can be used to supply electric power and PCA to parked aircraft. However, as discussed previously, APUs are still com- monly used for short periods of time at airports that have alternative systems in place (e.g., to start the main aircraft engines). Unlike individual APU models, alternative systems1 are better described by their overall system categories: • Ground power providing 400 hertz, 28.5v, or both power levels: – Portable diesel-powered systems; – Point of Use (POU) systems that are mounted either on the loading bridge or on the ground; and – Central systems. 1 Although this Handbook discusses each system separately, it is important to note that airport operators can mix and match the ground power and PCA components associated with each system.

4 handbook for evaluating emissions and Costs of apUs and alternative Systems • PCA (heated or cooled air): – Portable diesel-powered systems; – POU systems that are mounted either on the loading bridge or on the ground; and – Central systems. Point of Use (POU) systems provide the primary infrastructure needed for the power/HVAC capability at the use location. In contrast, central systems provide their primary function at a central location. For the PCA element, central systems are often integrated into the airport’s overall HVAC system. As each alternative system type can be used to satisfy the power and PCA load requirements for multiple aircraft types, the choice of which alternative system to implement is based on vari- ous factors related to costs, infrastructure requirements, and operational considerations. The three types of alternative systems have their advantages and disadvantages.2 A portable diesel-powered system, often referred to as a Ground Power Unit (GPU), is shown in Figure 2. These systems can be mounted on the back of a truck or they can be trailer/cart mounted for greater mobility. While a GPU provides for flexibility of movement and has a rela- tively low initial capital cost, local emissions are not avoided when most GPUs are in operation Aircraft Category Example Aircraft Types Representative APUs Narrow Body Boeing 737-700 Series, Boeing MD-80 Series, Airbus A320 Series, Boeing 757-200 Series, Airbus A319-100 Series, Boeing 737-800 Series, Boeing 737-300 Series, Boeing 717- 200 Series, Embraer ERJ170, Embraer ERJ175. GTCP 36-300 (80 HP), GTCP 85 (200 HP), GTCP85-98 (200 HP), GTCP85-129 (200 HP), GTCP-129H, GTCP 331-9B, GTCP 331-200, GTCP 85-98, GTCP 36-150, GTCP 36-4A. Wide Body Boeing 767-300 Series, Boeing 777-200 Series, Airbus A300B/C/F-600 Series, Boeing 767-200 Series, Boeing 767-400, Airbus A310- 200 Series, Boeing 777-300 Series, Airbus A300B/C/F Series, Airbus A310-300 Series, Boeing 787-300 Series. TSCP700-4B, GTCP331-200ER, GTCP331- 500, APS 5000. Jumbo - Wide Body Boeing 747-400 Series, Airbus A330-200 Series, Airbus A340-200 Series, Boeing 747- 200/300 Series, Airbus A330-300 Series, Airbus A340-600 Series, Airbus A340-300 Series, Airbus A340-500 Series, Boeing 747- 100 Series, Airbus A380 Series. GTCP 331-350, PW-980, GTCP 660, APU PW901A. Regional Jet Bombardier CRJ-200/400, Embraer ERJ145, Bombardier CRJ-700, Bombardier CRJ-900, Embraer ERJ140, Bombardier CRJ-100, Embraer ERJ135, Dornier 328 Jet, BAE 146- 100, BAE 146-200. GTCP 36-100, GTCP 36-150, GTCP 85. Turbo Prop DeHavilland DHC-8-400, DeHavilland DHC-8- 100, Embraer EMB120 Brasilia, DeHavilland DHC-8-300, DeHavilland DHC-8-200, Shorts 360-100 Series, DeHavilland DHC-7 Dash 7, Embraer EMB110 Bandeirante, Fokker F27- 100 Series, Fokker F27-200 Series. T-62T-40C7, APS 1000 T-62T-46C12, GTCP 36-150, GTCP 30-54. SOURCE: Developed from the FAA’s Emissions and Dispersion Modeling System (EDMS) fleet database (FAA 2010a). Table 1. Aircraft types and auxiliary power units grouped by aircraft category. 2 The focus of this Handbook is on the tradeoffs between the two alternative systems (Point of Use and central) that can be bridge- or ramp-based.

Introduction and Background 5 (i.e., diesel emissions). It is important to note that some battery based GPUs have been devel- oped, but these battery based systems are primarily used to provide power to small general avia- tion aircraft and thus are not used at most commercial service airports. Commercial service airports have a large number of vehicles and activities that are conducted on the ramp and adjacent to aircraft parking positions. Ramp traffic congestion and vehicle stor- age can also be an issue with mobile units. Self-contained, stationary, power, and PCA systems, also referred to as POU systems, run as single units (i.e., self-contained units—located at their POU) using airport electricity. As a result, their use does not produce emissions at the airport, although off-airport emissions associated with electricity generation at a power plant do occur. POU systems have lower up-front capital costs than central systems, but operating and maintenance costs can be substantial over time as discussed in Chapter 3. POU infrastructure also provides flexibility in modularity-of-use (can be purchased one at a time) and can be installed a few at a time, minimizing the required capital outlay. POU systems are typically bridge- or ramp-based. A typical passenger boarding bridge based POU system is depicted in Figure 3. The images depict a self-contained PCA unit and a power converter (frequency converter) unit. Figure 2. Typical diesel-powered portable system. Note: The image on the left shows a bridge-mounted PCA unit; the image on the right shows a bridge-mounted power converter unit. Figure 3. Typical bridge-mounted POU system.

6 handbook for evaluating emissions and Costs of apUs and alternative Systems Central systems use a main, centralized set of chiller and boiler units to provide pre-con- ditioned air to air handling units (AHUs) located at each gate. AHUs are simple devices con- sisting primarily of a blower, coil, and the associated actuators and controls. Unlike a POU system, a central ground power system has its power converters located at a central location, and the resulting power is distributed to gate electrical boxes at various gate locations. Power (solid state frequency) converters are typically comprised of four sections—the converter section, the direct current (DC) link, the inverter section, and a controls section—that work to convert DC voltage to an alternating current (AC) 400 Hz power at the required voltage. POU units typi- cally provide 115/200V, 3 phase, and 4—wire service for direct connection to the aircraft. In contrast, a central system can operate at many different voltages with final transformation to the required voltage in a gate box at the aircraft parking position. Central systems are typically 115/200V, 3 phase, and 4 wire (requires no transformation) or 575V, 3 phase, and 3 wire (requires transformation). Figure 4 depicts the main components of a central system. Because central power and PCA systems use grid electricity and natural gas, their operation results in little or no direct emissions of criteria pollutants. However, since these systems draw power from the electric grid, they are an indirect source of greenhouse gas emissions. Although the initial capital investment for a central system is greater than for a POU system, they generally require less maintenance, and their operating costs tend to be lower than POU systems (AERO Systems Engineering 2011). Central systems are usually housed in the central plant or another facility within the terminal building complex with utility equipment (i.e., AHUs and gate boxes). 1.3 Purpose of the Handbook and Reasons for the Research As discussed previously, the use of alternative ground-based infrastructure systems (herein- after referred to as alternative systems) to reduce the use of aircraft APUs has been identified as an effective method to reduce fuel burn and air pollution. While airport operators generally understand that implementation of alternative systems can result in reduced APU-related emis- sions and fuel consumption, there is little information regarding the relative benefits and costs associated with the primary types of alternative systems. Because size, layout, fleet makeup, and climatic conditions vary by airport, the same alternative system cannot be implemented at all airports. There is no one-size-fits-all solution—alternative system specifications must be tai- lored to the conditions at each individual airport. The Transportation Research Board (TRB) initiated ACRP Project 02-25 in July 2010. The Handbook, one of the primary products of the ACRP Project 02-25, contains information regarding the types of alternative systems available, and potential emission reduction benefits associated with reducing aircraft APU usage through the implementation of an alternative system. The Handbook also contains guidance that facilitates comparisons between different types of alternative systems across several parameters (e.g., energy use, emissions, infrastructure requirements, and cost). The Handbook is intended to present technical data for APUs and alternative systems in a clear and easy-to-understand manner using methodical step-by-step instructions and example calculations. This Handbook also provides information regarding tradeoffs associated with different alter- native systems as well as information regarding operational efficiencies and limitations. The Handbook is intended to provide general guidance and to facilitate decision-making regarding the implementation of alternative systems. The Handbook is geared toward planning-level analyses and assessments, and data contained in the Handbook and the associated Software Tool are not intended to support engineering or

Introduction and Background 7 Note: The photo on the upper-left shows a bridge-mounted gate box. The photo on the upper-right shows a bridge-mounted AHU. The photo on the lower-left represents a centrally located power converter unit. The photo on the lower-right shows centrally located chiller and boiler units. Figure 4. Typical components of a central system.

8 handbook for evaluating emissions and Costs of apUs and alternative Systems design processes. Similarly, the information contained in this Handbook regarding emissions associated with APUs and alternative systems should not be used for regulatory compliance purposes or in support of federal or state environmental impact documentation. Information contained in the Handbook is not intended to replace or supersede in any way the required use of the FAA’s Emissions and Dispersion Modeling System (EDMS) and Aviation Environmental Design Tool (AEDT) (FAA 2010a; FAA 2011b). 1.4 Software Tool Overview The Handbook is accompanied by ACRP-CD-113 which contains a Software Tool, the Tool for Evaluating Emissions and Costs of APUs and Alternative Systems (TEECAAS), which auto- mates the calculation of fuel/energy use, emissions, and costs using methodologies specified in the Handbook. While the Handbook provides overall guidance to allow the user to make informed decisions regarding alternative systems, TEECAAS strictly focuses on the quantifi- cation of emissions and costs. As with the Handbook, the tool is intended for planning-level assessments only and should not be used for regulatory compliance purposes. It is not intended to replace or supersede in any way the required use of the FAA’s EDMS or AEDT. TEECAAS was designed as a single window containing tabbed sheets with various datasets. The default data provided on each sheet have been grouped based on data category (e.g., APU use times, emissions indices, etc.). It is anticipated that most users of TEECAAS will use some of the default datasets to perform emission and cost calculations. It should be noted that TEECAAS results may not match results calculated using the guidance provided in Chap- ter 3 of the Handbook due to rounding errors. Emission factor values, energy consumption rate values and other information provided in Chapter 3 have been rounded to improve the readability of the Handbook. In contrast, the TEECAAS software makes use of unrounded emission factors and energy consumption rate values in its calculations to improve the fidel- ity of the results/output. TEECAAS is a Microsoft Windows-only tool that works on all versions of Windows starting with XP. 1.5 Organization of the Handbook and Intended Users The Handbook has been organized to separate information for first-time users from the infor- mation for more experienced users (See Figure 5). Chapters 1 and 2 present primer-type infor- mation for individuals who are less familiar with the different types of equipment and the issues involved with their usage. Chapters 3 and 4 present information that can be used to calculate emissions and costs for POU and central systems. Chapters 3 and 4 also present qualitative information regarding other important considerations relative to the design and implementa- tion of alternative systems. Individuals who are not familiar with emission and cost character- istics associated with APUs and alternative systems should review Chapter 2, while those who are more familiar with the subject matter can jump ahead to Chapter 3. A consolidated list of key assumptions, an acronym list, a list of helpful websites, and a list of Frequently Asked Ques- tions (FAQs) have been included in the Handbook (see appendices) to provide relatively quick answers to common questions. The intended users of both the Handbook and the Software Tool (TEECAAS) are airport operators and consultants wishing to conduct planning-level assessments involving imple- mentation of alternative ground power, heating, and air conditioning systems. Although

Introduction and Background 9 TEECAAS strictly focuses on calculations, the Handbook provides both primer-level infor- mation as well as detailed discussions of issues and methods. Therefore, the Handbook can potentially be used by airport management personnel wishing to gain a better understanding of the issues involved with alternative systems and by technical personnel to conduct quan- titative assessments. • Introduction • BackgroundChapter 1 • Basic considerations • Understanding of impactsChapter 2 • Quantification methods • Scenario comparisonsChapter 3 • Qualitative issues • Comprehensive understandingChapter 4 Primer-type information. Novice users should start with these chapters. Quantitative and qualitative information used to make decisions. Experienced users can start with Chapter 3. Figure 5. Handbook organization and utilization tips.