EPA-420-P-98-020 Median Life, Annual Activity, and Load Factor Values for Nonroad Engine Emissions Modeling Report No. NR-005A December 9, 1997 revised June 15, 1998 Christian E. Lindhjem and Megan Beardsley Nonroad Engine Emissions Modeling Team Assessment and Modeling Division EPA, Office of Mobile Sources Purpose EPA's NONROAD model computes emission inventories for nonroad engines. This report documents the default input values of median life, annual activity, and load factor for various types of nonroad engines. These values are used to calculate the fleet age distributions for each engine type included in this model. Annual activity and load factor values are also used to calculate the yearly emissions for each engine type included in the model. Introduction This report documents the default annual activity and load factor values. These estimates are used to determine emissions from engines by using the following equation. The discussion of the other default values of population, power, and emission factors are the subject of other reports. Emissions = (Pop) (Power) (LF) (A) (EF) where Pop = Engine Population Power = Average Power (hp) LF = Load Factor (fraction of available power) A = Activity (hrs/yr) EF = Emission Factor (g/hp-hr) ------- This report also documents the default values for the median life of engines. The first step in developing the age distribution is the determination of how long an engine is used in years. The median life, annual activity, and load factor are all variables used in estimating the median lifetime of nonroad engine. The median lifetime in years is determined from the median life expressed in units of hours at full load, the annual activity expressed in units of hours per year, and the load factor expressed in units of the fraction of available power as shown in the equation below. »f j- T --c v e \ Median Life (hrs) Median Lifetime (years) = J ^ ' Activity (hrslyr) * Load Factor The fleet of engines' age distribution and scrappage rates are estimated as functions of the engine age expressed in the fraction of median lifetime. For instance, when engines of a given model year are used to their median lifetime, 50% of the engines sold in that model year have been scrapped and are not in use. In order to determine the engine population at any given in-use year, the number of engines in every model year remaining in service needs to be calculated based on the estimated median lifetime in years calculated with the equation above. A further discussion of how the age distributions and scrappage rates are used to incorporate fleet turnover is the subject of another report. (1) For most applications, equipment is used until the engine no longer works; that is, median engine life is considered synonymous with median equipment life. Marine vessels and other large equipment such as mining and construction applications are exceptions to this rule, because they typically use replacement engines when the original engine cannot be rebuilt instead of purchasing entirely new equipment. Installing a new engine is assumed to have the same effect on emissions as replacing the equipment, so engine life remains the relevant value for age determination for these applications. Values Used in NONROAD for Median Life, Annual Activity, and Load Factor The estimates for median life, activity, and load factor used as default data files in NONROAD are described in this work. The NONROAD model classifies engine applications and fuel types with the use of a source categorization code (SCC). The descriptions shown in the tables below were translated to SCC's by the fuel type and application description. For diesel and gasoline engines, this translation is straightforward because the structure of the SCC's differentiates engines by fuel type. For application-specific engines, the description of the application is used to determine the appropriate SCC. The translation procedure of using application description and fuel type to denote SCC's is also described in the report describing default equipment populations. (2) ------- Median Life in Hours at Full Load Engine life varies with engine type and power level. The NONROAD model uses the median life estimates that the California Air Resources Board in its OFFROAD model uses. (3) These estimates are listed by horsepower class and engine type in Table 1. The horsepower classes are defined in Table 2. Liquid petroleum gas (LPG) and compressed natural gas (CNG) engines are primarily four-stroke spark-ignition engines and hence have many similarities with four-stroke gasoline engines. Because LPG and CNG engines are similar in design to gasoline engines, their median life is likely to be similar to the median life of gasoline engines. For this reason and the lack of relevant data to the contrary, LPG and CNG engines are assumed to have the same median life as gasoline engines in the NONROAD model. The values described represent the only comprehensive review of the engine life associated with the engine type and power level available. They represent median values of engine life, not distinguishing the engine by make or model. Individual engine models may have longer or shorter median lives. Surveys of engine life by application or engine type are encouraged to improve the estimates shown below. Table 1 Expected Engine Life in Hours at Full Load (3) Engine Type Diesel 2-stroke Gasoline 4-stroke Gasoline CNG/ LPG HP1 1250 150 200 200 HP 2 2500 200 400 400 HP 3 2500 750 750 750 HP 4 4000 — 1500 1500 HP 5 4000 — 3000 3000 HP 6 4000 — 3000 3000 HP 7 6000 — 3000 3000 HP 8 6000 — 3000 3000 HP 9 6000 — 3000 3000 HP 10 — — 3000 3000 ------- Table 2 Horsepower Classes for Median Life (3) HP Class HP 1 HP2 HP3 HP4 HP5 HP6 HP7 HP8 HP9 HP 10 Diesel <15 16-25 26-50 51-120 121-175 176-250 251-500 501-750 751+ — 2-stroke <2 3-15 16-25 26-50 51-120 121-175 176-250 251-500 501-750 751+ 4-stroke <5 6-15 16-25 26-50 51-120 121-175 176-250 251-500 501-750 751+ Small (<25 hp) Spark-Ignition Engine Median Life The median life (the point where 50% of engines have been scrapped) for several applications of nonroad engines have been estimated previously in terms of years of use. (4) For the purpose of the NONROAD model, the median life was converted from units of years to units of hours at full load using load factors and median hours of use which are shown in Table 5 below. To do this, we used the second equation shown above. Median life in years from Table 3 was multiplied by hours per year and load factor given in Table 5 to create the column in Table 3 and used as an input to the NONROAD model. The final values for the median life used in NONROAD for these selected applications are shown in Table 3. Lower or higher power level engines used the default values from ARB to distinguish power level among these applications because these engines are expected to be significantly different than the engines estimated previously. Table 3: Median Life for the Bulk of Several Small Spark-Ignition Engine Applications Application Lawn Mowers Use Residential Commercial Power (min.) 1 1 Power (max.) 6 6 Median Life (Hours at Full Load) 47.9 268 Median Life (Years) (4) 5.8 2 ------- Trimmer/Edger/Cutter Chainsaws Leaf Blower\ Vacuum Tillers Snowblowers Commercial Turf Rear Engine Rider Lawn and Garden Tractor Residential Commercial Residential Commercial Residential Commercial Residential Commercial Residential Commercial Commercial Residential Commercial Residential Commercial 0 0 0 0 0 0 0 0 0 0 3 3 6 3 6 3 3 6 6 6 6 11 11 6 6 25 16 16 25 25 19.4 157.6 28 136.4 21.5 324.3 39.4 830.7 12.3 209.4 988.9 79.3 627 114.8 920 4.3 2.3 4.3 0.9 4.3 2.3 5.8 4.4 4.4 4.4 2.9 5.8 2.9 5.8 2.9 Activity in Hours per Year The default input values for the activity estimates come from Power Systems Research (PSR), an independent research firm. This firm conducts several yearly surveys of equipment owners and determines a median usage rate for engines by application and fuel type. (5) These usage rates are shown in Table 4 for 2 and 4 stroke gasoline and diesel engines. The PSR methodology is described and evaluated in a report by Pechan. (6) The PSR data represents the most comprehensive review of application specific activity available to the NONROAD team. It may be possible to determine activity regionally for a few specific types of nonroad equipment, and the results compared with the PSR estimates used in NONROAD. If such information becomes available, the Nonroad Engine Emissions Modeling Team would consider using such information in future versions of the model. No data exist regarding activity levels for LPG and CNG engines. These engines are similar to gasoline engines because they employ spark-ignition. Therefore, LPG and CNG engines are more likely to be used in applications where gasoline engines are used, so they are assumed to have the same usage pattern as gasoline engines. ------- Load Factor PSR also estimates the load factor from surveys of equipment users. PSR calculates the fraction of load from the estimate of hours of usage per year, the fuel consumption per year, and the fuel consumption rate at rated power for each engine in the field. A median fraction of available power is determined for specific applications. The load factors are also shown in Table 4. As was the case for activity levels, LPG and CNG engines are assigned the load factors for gasoline engines. The load factor is determined from actual and maximum fuel consumption rates for various pieces of equipment. If alternative surveys become available, they would be considered for future versions. For reference, the PSR methodology is explained in detail in the Pechan report. (6) Table 4: PSR Estimates of Activity and Load Factor for Gasoline and Diesel Engines* 3SR Application Description jenerator Sets Mr Compressors 3umps til Field Equipment Jnderground Mine Equipment lefrigeration/AC Tactical Military Equipment Terminal Tractors \Velders 7orklifts )ther Material Handling ^ocomotive scrubbers/Sweepers surfacing Equipment 7orest Equipment Vlarine Auxiliary Shippers/Grinders Cranes ixcavators scrapers jraders brawler Dozers lubber Tire Dozer lubber Tire Loader Srush/Processins Equipment sec 22xx006005 22xx006015 22xx006010 22xx010010 22xx009010 22xx003060 not modeled 22xx003070 22xx006025 22xx003020 22xx003050 not modeled 22xx003030 22xx002024 22xx007015 not modeled 22xx004066 22xx002045 22xx002036 22xx002018 22xx002048 22xx002069 22xx002063 22xx002060 22xx002054 Activity Diesel (Hrs/year) 338 815 403 1231 1533 1341 260 1257 643 1700 421 848 1220 561 1276 2608 465 806 859 914 821 936 899 761 955 Load Factor Diesel (% of Max. Power) 74 48 74 92 68 28 62 82 45 30 59 63 68 45 71 67 73 43 57 72 61 64 59 68 78 Activity Gasoline (Hrs/year) 115 484 221 1104 260 605 225 827 208 1800 386 15 516 488 35 175 488 415 378 540 504 700 900 512 241 Load Factor Gasoline (% of Max. Power) 68 56 69 90 80 46 68 78 51 30 53 91 71 49 70 61 78 47 53 70 64 80 75 71 85 ------- 3aving Equipment )ther Construction Sore/Drill Rigs skid Steer Loader lollers )ff-Highway Truck 3avers Trenchers FractorVLoaderVBackhoe rrigation Sets Agricultural Tractor )ther Agricultural Equipment Combines swathers Balers 3owerboats (Inboard Marine) z%%% Frimmer/Edger/Cutter* * Agricultural Mowers snowb lower** Cement/Material Mixers 3ressure Washer Tillers** Jumpers/Tenders 3late Compactors specialty Vehicle/Carts ^awn and Garden Tractor** \erial Lifts ^awn Mowers** xaf Blower/Vacuum* * Commercial Turf Equipment** )ff-Highway Tractors sprayers ^hainsaws** snowmobiles** ^ight Plants\Signal Boards )ther General Industrial 22xx002021 22xx002081 22xx002033 22xx002072 22xx002015 22xx002051 22xx002003 22xx002030 22xx002066 22xx005060 22xx005015 22xx005055 22xx005020 22xx005045 22xx005025 2282010005 2282020005 22xx004025 22xx004026 22xx005030 22xx004035 22xx004036 22xx002042 22xx006030 22xx005040 22xx002078 22xx002009 22xx001060 22xx004055 22xx004056 22xx003010 22xx004010 22xx004011 22xx004030 22xx004031 22xx004071 22xx003070 22xx005035 2260004020 2260004021 2260007005 22xx001020 22xx002027 22xx003040 622 606 466 818 745 1641 821 593 1135 749 475 381 150 110 95 200 60 363 400 275 145 172 566 484 435 544 384 320 120 1068 855 90 70 50 535 878 53 62 75 55 56 57 62 75 55 65 70 51 70 55 58 35 43 43 65 56 30 78 38 43 65 57 46 55 40 55 65 58 60 40 78 51 175 371 107 310 621 450 392 402 870 716 550 124 125 95 68 100 34 175 45 84 115 43 127 166 65 104 361 76 56 733 155 80 26 121 318 713 59 48 79 58 62 80 66 66 48 60 62 55 74 52 62 38 68 48 78 59 85 71 41 55 58 62 46 70 75 60 70 65 92 81 72 54 ------- Wood Splitter )ther Lawn Garden** ^oncrete/lnd. Saws sailboat Auxiliary*** lailway Maintenance \ircraft Support lear Engine Rider** lough Terrain Forklifts lydro Power Unit 7ront Mowers jas Compressors Mi-Terrain Vehicles\Off-road Vlotorcycles 3ersonal Water Craft**** Vlini-Bikes jolf Carts rampers/Rammers shredders brawler Tractor (Agricultural Tractor with Crawler Tracks) '-Wheel Tractors Outboard Engines**** 22xx004060 22xx004061 22xx004075 22xx004076 22xx002039 22820xx020 22820xx025 228500x015 22xx008005 22xx004040 22xx002057 22xx005050 22xx004055 22xx004056 22xx006020 22xx001030 2282005015 22xx001040 22xx001050 22xx002006 22xx004050 22xx004051 22xx007010 No population not used 22xx005010 2282005010 9989090010 265 433 580 68 943 732 480 662 790 480 8500 0 0 0 1150 460 120 936 544 150 55 65 73 32 47 51 64 60 48 56 60 0 0 0 49 43 40 64 62 29 76 61 610 62 184 681 86 413 450 86 8500 135 100 55 1080 160 50 700 286 100 69 58 78 35 62 56 67 63 56 65 60 72 42 62 46 55 80 80 62 32 * Gasoline values are used for LPG and CNG engines. ** See discussion below of Small Spark-Ignition Engines for alternate use and load factors. *** Gasoline sailboat auxiliary is included in outboard and powerboats (inboard in the SCC nomenclature) **** New values for gasoline recreational marine shown below Small (<25 hp) Spark-Ignition Engines Activity and Load Factor Regulations to be proposed for small spark-ignition engines are described in greater detail in another report (2), and the supporting documentation for those regulations include estimates of activity and load for a few important applications. (4) The activity and load factors and power levels for these applications, mainly lawn and garden equipment, were derived from data supplied during discussions regarding the proposed regulations. These alternate values are shown in Table 5 and represent a departure from the PSR values shown above. For applications not shown in Table 5, the PSR values were used because the PSR survey includes such categories ------- as construction, agricultural, commercial, and many other engines applications already considered commercial and not included in the data submitted for the rulemaking. Many of the small spark-ignited engines are used in lawn and garden equipment applications, and lawn and garden equipment is used both by commercial and residential users. The commercial users are grounds keepers for nonresidential, large apartment complexes, and some single-family homes. Commercial equipment therefore has significantly different usage in terms of hours per year and weekday and weekend day than residential equipment. To account for these differences in equipment usage, separate SCC's were defined to distinguish commercial from residential lawn and garden equipment. ------- Table 5: Usage and Load Factors for Several Small Spark-Ignition Engine Applications Application Lawn Mowers Trimmer/Edger/Cutter Chainsaws Leaf Blower\ Vacuum Tillers Snowblowers Commercial Turf Rear Engine Rider Lawn and Garden Tractor Use Residential Commercial Residential Commercial Residential Commercial Residential Commercial Residential Commercial Residential Commercial Commercial Residential Commercial Residential Commercial Annual Hours 25 406 9 137 13 303 10 282 17 472 8 136 682 36 569 45 721 Load Factor (fraction of power) 0.33 0.33 0.50 0.50 0.50 0.50 0.50 0.50 0.40 0.40 0.35 0.35 0.50 0.38 0.38 0.44 0.44 Recreational Marine Engines As described in another report (2), recreational marine engines are divided into three applications; inboard, outboard, and personal watercraft. The outboard category includes the inboard\outboard sterndrive engines formerly considered as a separate application in the SCC system because the engine types are similar. The inboard engines are most closely associated with the PSR category 'powerboats' in Table 3. Personal watercraft were included in the PSR category formerly reserved for Off-Road Motorcycles which are now included with All Terrain Vehicles. 10 ------- A study of recreational boating activity indicates that boating activity may be considerably different than PSR estimates. (5, 7) In order to determine and estimate for activity in hours per year, it was necessary to estimate the number of engines (E), yearly fuel consumption of the engines (FC), brake-specific fuel consumption (BSFC), average horsepower (Hp), and a load factor (LF) by type of engine as described in the equation below. Activity (hrs/year) =(FC) / [(E) * (Hp) * (LF) * (BSFC)] According to the report (7), the fuel consumption and number of boats by boat type were determined and given in Tables II-3 (page II-6) and II-8 for gasoline-fueled engines. Cabin cruisers and other cabin boats were assumed to be inboard gasoline. Personal watercraft were determined uniquely, and all other boats were assumed to be driven by outboard-style engines. The total number of inboard, outboard, and personal watercraft boats were estimated to be 998,000, 9,065,000, and 200,000 respectively. Table II-9 shows the fraction of boats that have one and two engines where 26.8% of inboard boats have two engines; 2.7% of outboard boats have two engines; and no personal watercraft engines. So it is estimated that there were 1,265,000 inboard, 9,309,755 outboard, and 200,000 personal watercraft engines nationally in 1990-1991, the time period for the survey. Total fuel consumption was determined from Table II-3 based on the criteria described above to be 257,173,000 gallons for inboard, 672,009,000 gallons for outboard, and 25,063,000 for personal watercraft for the survey year. To determine the fuel consumption of the engines, data was submitted to EPA which indicated fuel consumption as a function of power level and is shown in Table 6. (8) The fraction of engines by power level was determined from PSR data for the 1990 in-use year and associated with fuel consumption estimates to determine an average fuel consumption of 0.216 for outboard, 0.100 for inboard, and 0.160 for personal watercraft in units of gallons/hp-hr. Table 6 Fuel Consumption by Power Level Engine Type 2-stroke 4-stroke Power Level 0-16 hp >16hp 0-25 hp 25-40 hp >40hp Fuel Consumption (gallons/hp-hr) 0.27 0.16 0.14 0.12 0.10 11 ------- The average power for the three types of engines was determined from the PSR estimates of the 1990 in-use populations. Price Waterhouse estimate average power level by boat length and type of boat rather than a direct measure of average power level. The average power level of outboard engines was determined to be 37 horsepower from PSR compared with roughly 66 for the Price Waterhouse estimate. The average power level for inboard engines was estimated to be 166 from PSR compared with 179 for the Price Waterhouse. The average power level for personal watercraft was estimated to be 52 from PSR compared with 50 for Price Waterhouse. By using the PSR data for average power level, we are consistent with the use of PSR in determining the population distributions for this version of NONROAD. Other supplied comments indicates that EPA should revise the load factor to accurately reflect the duty cycle in the certification test of 20.7% of rated power. In-use data of load factor is not available, and the PSR estimates of load factor (32% for outboard, 38% for inboard, and 42% for personal watercraft) are not currently documented. Using the combined information and estimates, the average activity is estimated to be 75 hours per year for inboard, 45 hours per year for outboard, and 73 hours per year for personal watercraft engines compared with the PSR estimate of 100 hours for all types of recreational marine gasoline engines. It is helpful to remember that this implied activity is related to the number of hours that the engine actually operates, not necessarily how many hours the boat is in- use on the water. References (1) EPA, "Growth and Scrappage Methodology Report for NONROAD," NR-008, Jan. 1998. (2) EPA, "Nonroad Engine Population Estimates," NONROAD Documentation, NR-006, Dec., 1997. (3) ARE, "Documentation of Input Factors for the New Off-Road Mobile Source Emissions Inventory Model," Energy and Environmental Analysis, Inc., February, 1997. Table 3-1. (4) EPA, "Statement of Principles for Nonroad Phase 2 Small Spark-Ignited Engines; Proposed Rule," 62 FR 14740, March, 27, 1997. (5) Power Systems Research, "Reference Guide, US Parts Link Edition 6.2," St.Paul, MN. (6) E.H. Pechan, "Evaluation of Power Systems Research (PSR) Nonroad Population Data Base," prepared for Office of Mobile Sources, U.S. Environmental Protection Agency, September 1997, EPA Contract No. 68-D3-0035, Work Assignment No. III-107, Pechan Report No. 97.09.003/1807. (7) Price Waterhouse, "National Recreational Boating Survey," Draft Final Report, Prepared for the U.S. Fish and Wildlife Service and the U.S. Coast Guard, March 9, 1992. (8) Ted Morgan, "Emission Data for Recreational Marine Engines," communication to Ken ZerafaoftheEPA, September 13, 1991. (9) Ted Morgan, communication to Rich Wilcox of the EPA, April 13, 1998. 12 ------- |