Handbook for Evaluating Emissions and Costs of APUs and Alternative Systems (2012) / Chapter Skim
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17 C h a p t e r 3 This chapter provides a step-by-step guide to calculating fuel (energy) consumption, emissions, and costs for various scenarios involving APUs and alternative systems.
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18 handbook for evaluating emissions and Costs of apUs and alternative Systems be served by the alternative systems. For the purposes of this Handbook, aircraft fleet mix is defined in terms of five (5)
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Quantitative assessments 19 Table 2 are based on one cold condition (Winter) , two neutral conditions (Spring and Fall)
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20 handbook for evaluating emissions and Costs of apUs and alternative Systems applications have been prepared for a number of airports, gate block time can be collected and then adjusted down by seven minutes to account for the time the APU will be in operation during the "Gate In" and "Gate Out" modes. The adjusted gate block time reflects the total time that the aircraft is located at the gate and incorporates the four TIM categories presented in Table 3.
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Quantitative assessments 21 sion factor with the quantity of fuel (e.g., kilogram of fuel) representing the activity data.
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22 handbook for evaluating emissions and Costs of apUs and alternative Systems power electricity requirements for POU systems are identical to those for central systems and central systems with airport boilers as discussed below. The ground power requirements presented in Table 8 reflect the use of a 40% diversity factor.
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Quantitative assessments 23 3.2 Quantifying Fuel Consumption and Emissions The common basis for the quantification of fuel consumption and emissions for APUs and alternative systems is the identification of aircraft types that the equipment will service. To simplify the assessments and to ensure that calculations support a planning-level of analysis, all assessments described in this chapter use the aircraft categories described in Table 1 and presented below: • Narrow Body, • Wide Body, • Jumbo -- Wide Body, • Regional Jet, and • Turbo Prop.
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24 handbook for evaluating emissions and Costs of apUs and alternative Systems the calculations can potentially be improved through the use of more specific data (e.g., regionspecific data) , the methods presented herein are to be used strictly for planning purposes and should not be used in support of regulatory compliance.
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Quantitative assessments 25 and 7 to compute APU fuel burn. Users without airport specific data will use data provided in Tables 2, 8, 9, 10, and 11 to compute alternative system electricity and heat energy consumption.
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26 handbook for evaluating emissions and Costs of apUs and alternative Systems Calculate APU emissions for the four modes of APU operation and the three ambient conditions as follows: E FB EI (Formula 2A) Where: E = Emissions per mode g FB= Fuel Burn per mode kg EI = Emissions Index g kg )
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Quantitative assessments 27 Sample FB and emissions calculations for APUs, POU systems, central systems, and central systems with airport boilers are presented in the following sections. These sample calculations make use of the formulas presented in this section and default data presented in Section 3.1.2.
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28 handbook for evaluating emissions and Costs of apUs and alternative Systems Assuming the number of LTO cycles/yr for each aircraft category is specified, fuel burn and emissions are calculated for each of the four APU modes and three ambient temperature condition combinations. Example fuel burn, CO2 emissions, and THC emissions calculations for the "APU Start" mode and the "Narrow Body" aircraft category are presented in the following paragraphs.
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Figure 7. Sample calculations -- APU fuel consumption and emissions.
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Figure 8. Sample calculations -- APU weighted fuel consumption and emissions.
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Quantitative assessments 31 using the resulting 111,188.510 g/LTO emissions of CO2 from Figure 8, the total CO2 emissions for the "Narrow Body" aircraft category would be calculated using Formula 4 as: CO Emissions 111,188.510 g LTO 40,000 LTO2 = ( )
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32 handbook for evaluating emissions and Costs of apUs and alternative Systems Emissions are then calculated using Formula 2B as follows: E EE EF Where: E Emissions permode g EE Elec = × = ( ) = tric Energy consumption permode KWh EF Em ( )
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Quantitative assessments 33 This is repeated for the heating and cooling operations, and then the energy consumption values are summed accordingly to match the combinations specified in Table 11. For example, electric energy consumption from ground power is combined with electric energy consumption for cabin heating: Total electric energy consumption ground po= wer electric energy cabin heating electric+ energy 1.433 KWh 2.802 KWh 4.235 KWh = + = Emissions are calculated as exemplified by this CO2 emissions calculation: CO Emissions 4.235 KWh 618 g KWh 2,6172 = ( )
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Figure 10. Sample calculations -- POU system energy consumption and emissions.
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Figure 11. Sample calculations -- POU system weighted energy consumption and emissions.
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36 handbook for evaluating emissions and Costs of apUs and alternative Systems Similar to the evaluation process for POU systems, users can supply all of the above data or can use default data for all except the locally specific LTO cycles. To calculate electricity (energy)
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Quantitative assessments 37 E EE EF Where: E Emissions permode g EE Elec = × = ( ) = tric Energy consumption permode KWh EF Em ( )
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Figure 14. Sample calculations -- central system energy consumption and emissions.
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Quantitative assessments 39 Figure 14 are summed to generate the total energy value in the one table at the bottom left corner. The resulting three tables at the bottom of Figure 14 represent the sum of the energy and emissions data for the "Gate Out" and "Gate In" modes with each table corresponding to one of the three ambient conditions.
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Figure 15. Sample calculations -- central system total weighted energy consumption and emissions.
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Quantitative assessments 41 In order to calculate emissions from central systems, the first step is to calculate the electricity (electric energy) consumption required for ground power, heating, and cooling using Formula 1B: EE EP TIM Where: EE Electric Energy consumpti = × = on permode KWh EP Electric Power KW See T ( )
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42 handbook for evaluating emissions and Costs of apUs and alternative Systems E HE EF Where: E Emissions permode g HE Heat = × = ( ) = Energy consumption permode BTU EF Emissi ( )
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Quantitative assessments 43 ambient condition combinations. Example calculations for ground power electricity consumption and heat energy consumption for the "Narrow Body" aircraft category follow.
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Figure 18. Sample calculations -- central system with airport boiler electricity-based energy consumption and emissions.
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Quantitative assessments 45 percentages in Table 2 and then summed to produce weighted tables as presented in Figures 20 and 21. For example, the weighting for electric energy consumption for the "Narrow Body" aircraft category is conducted as follows: Weighted average EE Cold EE 0.25 Neutral= ×( )
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Figure 20. Sample calculations -- central system with airport boiler weighted electricity-based energy consumption and emissions.
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Quantitative assessments 47 category of interest as presented in Table 13. For example, using CO2 emissions data from Figures 20 and 21, total CO2 emissions for the "Narrow Body" aircraft category are calculated using the following equations: Total Electricity-related CO Emissions yr2 = 7234 061 40 000 289 362 4 .
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48 handbook for evaluating emissions and Costs of apUs and alternative Systems Figure 22. Sample calculations -- central system with airport boiler total electricity-based energy consumption and emissions.
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Quantitative assessments 49 3.3 Estimating Costs for Alternative Systems As discussed previously, this Handbook includes cost data for three types of alternative systems: POU systems, central systems, and central systems with airport boilers. Portable dieselpowered systems are not included since reliable cost data could not be obtained.
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50 handbook for evaluating emissions and Costs of apUs and alternative Systems 3.3.1.3 Methodology Along with the specification of APU TIM values and the total number of LTO cycles per year for emissions calculation purposes, the number of gates also needs to be specified to calculate alternative system costs as presented in Table 14. The number of gates and the number of LTOs/yr for each aircraft category are interrelated and, therefore, must be carefully estimated to ensure proper (realistic)
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Quantitative assessments 51 These calculations are performed for each of the five aircraft categories, as applicable. Then, the individual costs are summed to obtain the total capital cost.
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52 handbook for evaluating emissions and Costs of apUs and alternative Systems As indicated in Table 17, the POU system maintenance cost rate is constant (not adjusted based on the number of gates to be served by the POU system)
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Quantitative assessments 53 Narrow body aircraft category electric energy consumption MWh yr KWh yr = = 653 697 653 697 . , Note: 1MWh KWh POU system operatin =( )
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54 handbook for evaluating emissions and Costs of apUs and alternative Systems The total cost is calculated as: Total POU system cost = +$ , , $ , ,9 323 600 1 511 053+ = $ , , $ , , 3 247 860 14 082 513 3.3.2 Central System Costs Input Data The following sets of data by aircraft category are necessary to calculate central system costs: • Number of gates, • Central system capital costs per gate, • Cost of electricity, • Central system maintenance costs per gate, and • Central system electric energy consumption data (See Section 3.2.3)
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Quantitative assessments 55 These calculations are performed for each of the five aircraft categories, as applicable. Then, the individual costs are summed to obtain the total capital cost.
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56 handbook for evaluating emissions and Costs of apUs and alternative Systems As previously explained, these costs can be modified as necessary to reflect present day values using a suitable inflation rate such as 2%. Example Calculations The example calculations presented herein are based on the use of the example and default data presented in this chapter and assuming a 15-year usage period.
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Quantitative assessments 57 As with the emissions calculations, these costs represent average weighted values because the electric energy consumption values account for the distribution of ambient conditions (i.e., 25% cold, 50% neutral, and 25% hot)
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58 handbook for evaluating emissions and Costs of apUs and alternative Systems Although these datasets are necessary, the user is generally only expected to supply the number of gates by aircraft category. The default data presented in this section are used for all other variables.
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Quantitative assessments 59 Similar to capital costs, these calculations can be performed for each of the aircraft categories if cost per category is necessary. Otherwise, the total electric energy and total heat energy consumptions for all aircraft categories can be used.
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60 handbook for evaluating emissions and Costs of apUs and alternative Systems The operating cost for the narrow body aircraft category is: Narrow body aircraft category electric energy consumption 468.224MWh/yr 468,224 KWh = = /yr (Note: 1MWh= 1,000 KWh) Central system electricity-related operating cost 468,224 KWh yr $0.07 KWh 15 years = ( )
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Quantitative assessments 61 Central systemmaintenance cost rate for 38 gates 38 30 40 30 2,615 2,636= − − × −( ) + = 2,636 $2,619.2 gate-yr Then the maintenance cost is calculated as: Central systemmaintenance cost 38 gates= ( )
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62 handbook for evaluating emissions and Costs of apUs and alternative Systems an order-of-magnitude. As such, their usefulness increases when they are compared (i.e., comparison of results from different scenarios)
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Quantitative assessments 63 Second, although total costs for alternative systems can be compared, it is recommended that capital, operating, and maintenance cost estimates be preserved and compared to allow a greater understanding of the factors that influence total costs. This may also allow the user to identify better strategies in terms of using existing financial resources to implement alternative systems.
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