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How to Build a Retrofit Project
Step 2: Identify Candidate Equipment and Vehicles
A successful retrofit project begins with careful selection of engine candidates. Some engines and vehicle applications make much better retrofit candidates than others, and certain engines and vehicles may simply be inappropriate for investment in an upgrade. Once a particular fleet has been selected, the next step in the retrofit process is to identify the most appropriate retrofit strategy. Proper technology matching helps ensure that emissions performance meets a project’s air quality improvement goals, while vehicle reliability is not negatively impacted and the project’s overall effectiveness is not undermined. For example, use of cleaner fuels that are not available at retail outlets is a poor match for on-road, line-haul trucking fleets that rely on retail fuel purchase, but are a good match for fleets that are centrally fueled, such as municipal refuse vehicles or off-road construction equipment. Some technologies, such as DPFs and catalyzed wire mesh filters (CWMFs), are significantly heavier than the original equipment mufflers they are designed to replace and require additional mounting brackets for stability as well as thermal blankets to help sustain specific exhaust temperatures for regeneration. Both approaches may also require some engineering and fabrication to aid in installation as well as assuring that safety is not impaired by blocking sight lines or exposing personnel to hot surfaces.
Certain technologies, while appearing attractive on paper, require specific operating profiles to be effective. As noted earlier, passive DPFs require specific minimum threshold engine exhaust temperatures to ensure effective regeneration of accumulated soot. As a result, their application may be limited and verification requires the installation of on-board backpressure monitors to warn operators during day-to-day operation of an impending need for maintenance i.e. to indicate when ash removal is necessary.
Many of the most effective diesel emissions reduction devices require some level of periodic maintenance to operate effectively and safely. DPFs require periodic disassembly to clean out ash deposits. Closed Crankcase Ventilation (CCV) systems require periodic filter replacement much like an engine oil filter (and frequently at the same intervals). Sophisticated NOx-reduction technologies, such as SCR, require periodic refilling of on-board urea reductant tanks. Failure to follow these and other prescribed procedures could compromise the effectiveness of the technology, render the vehicle inoperative, or even damage the engine. On the other hand, none of these or other precautionary and maintenance procedures are particularly onerous, and with adequate training, are easy to perform and adhere to over the life of the vehicle.
In some retrofit decisions, technical issues may be less important than economic considerations. Diesel engines are used in a variety of industry sectors: school bus, freight, construction, ports and agriculture. Each is characterized by a unique operating environment and business model that must be considered in order to balance emissions benefits with business profitability. For example, what works for terminal operators at ports may be completely inappropriate, or even disadvantageous for line-haul truck operators, construction contractors, or school bus operators. What follows is a brief look at some of these sector specific considerations
School Buses
Approximately 400,000 full-size school buses are currently in operation, the majority of which are diesel powered. Of these, roughly one-third were built before 1991, emitting six times more PM and twice the NOx of a 2005 diesel bus. These vehicles are obvious candidates for retrofit projects, and yet EPA estimates that only 7.5 percent of them – due to a number of considerations– have been involved in a clean school bus project. One of the biggest impediments to school bus retrofits is the lack of funding. Approximately 70 percent of school buses are owned, operated and maintained by school districts, which are locally funded and often cash strapped due to competing demands on municipal budgets. EPA’s Clean School Bus USA program has tried to fill this gap, however other challenges such as the limited capacity of individuals within the district or the lack of public partners to apply and manage grants create additional challenges, even if sufficient federal funds were available to cover the need.
From a technical perspective, DPFs have been verified with critical temperature specifications based on engine load and speed, thereby making some inappropriate for school bus applications that tend to operate under minimal load. They also require the use of ULSD, which before October 2006, has generally been unavailable outside of major metropolitan areas. As a result, a majority of the retrofits to date have been performed with DOCs, which are less expensive and could run on readily available diesel fuel.
Freight
Ground freight transportation, comprising onroad trucks and rail, accounts for 82 percent of all goods movement in the U.S. Together these modes account for 40 percent and 30 percent of transportation-related NOx and PM emissions, respectively. Truck and rail transport of goods will continue to grow in the years ahead. Significant emissions reductions were also realized through the nationwide introduction of ULSD fuel and cleaner heavy-duty engines in 2007. Additional progress can be realized through a variety of retrofit options, including anti-idling devices, fleet modernization, engine upgrades and exhaust emissions control devices
In the rail industry, technological barriers with emissions control devices make widespread retrofit a longer term proposition. One alternative is to rebuild or repower older locomotive engines with those that result in lower emissions levels while simultaneously improving overall performance. Another option is to install auxiliary power units (APUs) as an anti-idling technology. APUs allow the locomotive engine to be shut down while maintaining constant power to the train. By using significantly less fuel and emitting fewer emissions than the locomotive engine, APUs can help improve air quality while providing a fuel-saving alternative for the railroad.
Like the rail industry, trucks spend a significant amount of time idling, primarily to keep drivers cool and comfortable while not on the road. As a result, APUs and advanced truck stop electrification also can help supply truck drivers with electricity to meet their needs while the engine is turned off. In both cases, economic benefits complement the emissions reductions through fuel conservation and less engine wear and tear.
Nevertheless, unlike locomotives, trucks can benefit from the application of exhaust emissions control devices. In 2003, EPA created its SmartWay program to help reduce emissions and energy consumption from the ground freight industry. This voluntary collaborative serves to reduce environmental footprints by helping carriers reduce their emissions and encouraging shippers to use only participating SmartWay carriers.
In order to help make emissions reduction and fuel efficiency technologies more accessible, SmartWay has developed upgrade kits that combine the two so that fuel efficiency cost savings can pay for the emissions reduction improvements. SmartWay helps carriers identify national and state loan programs to help finance the initial cost of the upgrade kits. More information on the program is available at: www.epa.gov/smartway
Ports
There are over 180 seaports along the U.S. contiguous coasts, islands and internal waterways, most of which are controlled by state or local public governmental agencies. Many of these also lie in or border NAAQS non-attainment areas and have become a particular concern for regulators and adjacent communities. Unlike other sectors, ports are an amalgam of five different sub-sectors operating within the same geographical area, all of which operate under different business models and operating conditions. As a result, diesel emissions reduction strategies will differ depending upon their unique technological challenges, the complexity of their business operations and the influence of public port authorities.
Ocean-going ships typically present the greatest challenge due to their very large compression ignition engines, complex worldwide operations and limited port involvement other than temporary docking. For this sub-sector, emissions reduction programs have focused on fuel quality through Sulfur Emission Control Areas because fuel used in ocean-going ships is known as bunker oil, a more energy-dense, less-refined, higher sulfur fuel. Of the four other subsectors: harborcraft, drayage trucks that transport goods into and out of the port, rail service and dockside equipment used for cargo handling, the latter has been given most attention.
Terminal operators rely on smooth, continuous operation of their loading equipment to maximize efficiency and profitability. As a result, replacing or repowering older equipment followed by refueling with lower sulfur fuels have been among the most preferred emissions reduction strategies at ports. The former provides better performance together with air quality improvements, making it an attractive option. The benefits of refueling include easy implementation and little if any intrusion on terminal operations since there is no downtime required for installation. Retrofit emissions control technologies are generally regarded as less attractive owing to concerns about operating performance in harsh environmental conditions, fear about equipment downtime for maintenance and operator sight obstruction issues.
In addition to these technical considerations, port-related retrofits can be hampered by the competition for funds which may also be needed to meet national security mandates and the complexity of working with multiple jurisdictions.
Construction
Despite the construction industry’s size and importance to the U.S. economy, the majority of companies are quite small, with 92 percent of the industry’s 700,000 firms having fewer than 20 employees. They tend to be low-margin businesses with much of their business value accumulated in their capital equipment. Because of this, construction companies resist modifications that will restrict their equipment’s operability. Retrofit technology offers few economic benefits and poses potential risks for owners due to the downtime associated with installation and possible additional maintenance and training costs. Yet increasingly, failure to invest in these equipment upgrades can prevent them from competing for projects with contracting requirements for cleaner equipment.
Currently 2.1 million units of off-road construction equipment are believed to be in use, 31 percent of which are so old that they have no emissions controls. Emissions reductions from off-road diesel engines have lagged behind their on-road counterparts, making the potential for air quality improvements through retrofit of these vehicles more cost-effective. This is particularly true in urban areas where the majority of construction sites, population centers and non-attainment areas are located.
The construction industry poses several unique challenges in retrofit decisions including extended idles and/or low-speed operation periods,vibration, high levels of dust, space limitations and operator visibility. Repowering has been a strong retrofit option for construction equipment since upgraded engines pose less performance risk and can improve equipment performance and longevity. Another option is to use Upgrade Kits as part of a rebuild solution. Refueling and emissions control devices offer other possibilities, with the latter somewhat limited by their NOx/PM emissions ratio, age, varying duty cycles and the limited number of verified technologies. Unfortunately, the specificity of construction equipment applications has hindered the speed at which new technologies have been developed, tested and verified.
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