By Steve D. Johnson
If you attended the APTA EXPO this past year, you noticed that everyone who had an electric vehicle showed it. You also noticed that there are some new players in the market building electric vehicles. Finally, you noticed that nearly every supplier selling mechanical accessories now has an electrically-driven alternative. The future of transit was on display and the public is very excited. However, the reality is that this is going to be a rather slow and lengthy transformation. Consider that Los Angeles has committed to switch its entire fleet of over 2,000 buses to zero emission by 2040. That is very aggressive considering that by 2040, diesel, CNG and hybrid electric drivetrains will still be more than 50 percent of all deliveries according to some market research forecasts. What this means for most fleets in North America is that we will be living with diesel, CNG and hybrid electrics for a long time to come. The race to zero emissions is more like a marathon as opposed to a 100-meter dash.
For the current bus population, efficiency improvements and emission reduction are still, and will remain as important objectives in the drive to reduce Green House Gases (GHG) and our overall carbon footprint. Given that the average fleet will have a complete turnover of buses at least twice in the next 25 years, what can we be doing in the interim as the new zero emission buses are integrated into the fleets? Here are a few suggestions:
• Identify and specify fuel reduction technologies for the HVAC, your largest single load.
• Consider the horsepower requirements for accessories and choose the most efficient.
• Add electrically-driven accessories wherever possible. This could include radiator fans, power steering, doors and the HVAC.
Let’s focus on the HVAC since that is what this series is about. Currently, the estimated population of standard diesel and CNG driven buses with all-electric HVAC is just over 3,000. There are many who are not aware of the fact that you can have an all-electric HVAC on a conventional bus, nor are they aware of the tremendous benefits. One good example is Miami-Dade Transit. The managers there had a vision which was to take a hybrid bus, add electric cooling fans and a self-powered all-electric HVAC, and test against the fleet for fuel economy. The hypothesis was to get a 7 percent contribution from each component – the hybrid drive, the electric cooling fans and the HVAC – for a total 21 percent improvement. In 2011 Miami-Dade put five hybrid buses of this configuration into service. In July 2012, the Miami Today News posted a story that said the five hybrids were 32 percent more efficient than the fleet. While it is not clear what the exact percentage contribution was for each in this case, the next example clearly shows that the HVAC was a major contributor. At a press conference during the 2014 APTA EXPO, Antelope Valley Transit Authority reported a fuel savings of $4,000 per bus annually, for 29 diesel buses in the fleet with the self-powered all-electric HVAC.
Both properties are in high-use HVAC areas and it should be noted that the level of fuel consumption reduction is related to how much HVAC is used, but in all cases an improvement should be seen. There are other significant benefits of all-electric HVAC not related to fuel. The mechanical compressor with its valves and fittings, the clutch and the connecting hoses are gone. Going away with them is the potential for failure and many hours of preventative maintenance. The savings in labor alone amounts to 50 percent when compared to a conventional HVAC. Also, the unit is sealed and tested at the factory so the risk for errors associated with field plumbing are eliminated. The value proposition is solid.
There is a cost premium associated with the self-contained all-electric HVAC but the savings in fuel, labor and provides the payback in three to five years. Those savings will continue for the next seven to nine years, giving you lower operating costs and the opportunity to contribute to a sustainable planet. By the time you get your first zero-emission bus you will be very familiar with the all-electric HVAC that will come with it.
Steve D. Johnson, Sr. serves as product marketing manager, Bus HVAC, at Thermo King, Minneapolis, MN. Thermo King is a world leader in transport temperature control systems for buses. Thermo King also manufactures auxiliary power units, which dramatically reduce engine idling. All Thermo King products are backed by a nationwide dealer network.