Older, heavy-duty diesel vehicles that will not be scrapped, retired or replaced for several years are potential candidates for diesel emission-reduction retrofit devices, such as exhaust, crankcase, and anti-idling retrofits.
Closed-Loop Crankcase Ventilation (CCV) Retrofits
Depending on the age of the vehicle, approximately 10% of the total vehicle emissions come from the engine crankcase. CCV systems use filters to capture the oil in the air or blow-by emitted from the engine crankcase. This technology is very important for vehicles such as school buses because crankcase filters help prevent engine emissions from entering the vehicle cab.
Several anti-idling technologies are available to reduce diesel emissions and fuel use:
- Thermal Storage Systems store engine heat while operating, which can then be used to heat/cool the engine cab for a period of time after the main engine has been turned off.
- Fuel-Operated Systems:
- Pre-heaters: Small diesel engines that heat engine fluids. Pre-heaters can be connected to the engine HVAC system to heat the vehicle cabin and defrost windows.
- Air-heaters: Small diesel engines that provide heat in vehicle cabins.
- Auxiliary Power Units or Generators supply cooling, heating, and electrical power to Class 8 trucks, emergency response vehicles, and other heavy-duty applications.
- Automatic Shutdown/Startup Devices shut off the main engine and then restart it when necessary based on preset parameters (set time, engine temperature, battery charge, etc.).
- Shore Power Plugs enable auxiliary power needs to be supplied by an external electrical source, such as a shore power station. Shore power is also used for ocean-going vessels to enable the vessels to "plug in" while at berth to load and unload cargo or passengers.
- Truck Stop Electrification provides an electrical source the vehicles can plug into to obtain power for heating, cooling, and other accessories.
Exhaust retrofits are used to reduce emissions coming out of the vehicle’s tailpipe/mufflers. They use a catalytic process and/or filter technology to reduce carbon monoxide, hydrocarbon emissions, and diesel particulate matter (DPM). There are three types/levels of exhaust retrofit devices:
Level 1 Retrofit
- A flow-through catalytic device, e.g., diesel oxidation catalyst.
- Reduces the least amount of DPM - 25%
- Requires minimal maintenance and does not have special temperature or opacity requirements.
Level 2 Retrofit
- A flow-through catalytic device.
- Reduces DPM by at least 50%.
- Requires occasional maintenance and has some temperature and opacity requirements.
Level 3 Retrofit
- A filter technology with either a passive or active cleaning system:
- Passive Level 3 retrofits must be removed from the vehicle to be cleaned.
- Active Level 3 retrofits have active systems that help clean the filter while it is still on the vehicle.
- Reduces the most DPM - more than 85%.
- Requires regular maintenance and has more-stringent temperature and opacity requirements.