Testing Hydraulic-Hybrid Refuse Haulers
Hydraulic-Hybrid Refuse Haulers
CLIENT: City of Manteca, CA
As part of a demonstration project funded by a new technology development grant from the San Joaquin Valley Air Pollution Control District (CIP Project No. 11078), the City of Manteca, CA contracted carbonBLU personnel to determine the actual fuel and emissions savings of operating new, RunWise hydraulic-hybrid diesel refuse haulers (manufactured by Parker Hannifin’s Hydraulic Pump & Power Systems division in Marysville, Ohio) as compared to the conventional diesel Autocar refuse haulers. This comparison required first developing a method to measure the in-use emissions of the vehicles and compare those results on an “apples-to-apples” basis.
- Log real, in-use vehicle data for thirty days.
- Analyze and compare in-use emissions data.
- Prepare a report of our analysis for regulators, and the city.
In January of 2013, data loggers were installed on both types of trash haulers and activity and engine data were logged for at least 30 days on each unit. The data logging equipment recorded important engine and vehicle parameters (such as engine load, estimated fuel consumption, engine speed, etc.) every second. They also logged the location of the vehicle every second using a GPS system.
Through subsequent analysis of the logged data and through interviews with Manteca’s Solid Waste Division, carbonBLU personnel determined that the best way to emissions test these units would be during actual trash and green waste collection routes. The routes would be as similar to each other as possible, but would not be identical. Therefore, a hypothetical duty-cycle would not be used to collect the emissions and fuel consumption data. Instead, a hypothetical duty-cycle would be used during analysis of the data. This approach to comparing the emissions from two vehicles is often called “Modal Analysis.”
Modal Analysis categorizes the emissions and fuel consumption data into similar operating modes, based upon the type of activity the vehicle is performing. Then an average emissions and fuel consumption rate for each of the categories of activity is determined. Then those averages are recombined into an “overall” average that represents a typical day’s worth of activity for each vehicle. This approach ends up comparing the two vehicles over the exact same duty-cycle that has been assembled from the Modal Analysis results – after the emissions data are collected, instead of in advance.
In June of 2013, using the methods developed previously in the project, carbonBLU personnel then emissions tested a hydraulic-hybrid diesel and a conventionally powered refuse hauler as they performed their normal refuse collection duties. The portable emissions measurement system (PEMS) combined gaseous measurement instruments with a particulate measurement instrument. The gaseous PEMS was a system pre-approved by EPA for in-use compliance testing of heavy-duty on-road vehicles according to 40 CFR 1065. The PM PEMS used a laser light scattering principle that measures scatter from two angles and relates it to PM mass emissions.
The resulting data were compared and reported to Manteca using methods also developed earlier in the project. As later requested by the San Joaquin Air Pollution Control District, carbonBLU personnel also conducted analyses comparing the hybrid model to similar conventional models of the same model year, based upon emissions standards and estimated fuel efficiency differences.