Memphis Fire Department implements idle reduction technologies

Four MFD ambulances outfitted with ZeroRPM technology sit against the Memphis skyline; Credit: Lieutenant Jonathan Haley, MFD

In the last year, the Memphis Fire Department (MFD) has introduced idle reduction technologies to its ambulance fleet in order to minimize fuel waste, idle wear and pollutant emissions from its emergency vehicles.

In the emergency medical field, the standard operating procedure requires that an ambulance be kept ready and warmed. This is done for a few reasons:

  • An ambulance must be prepared to respond to a call with minimal delays
  • Treatment requires a temperature-controlled environment, particularly in extreme cold or heat
  • Refrigeration and communications systems require sustained power
  • Onboard equipment requires electricity to maintain appropriate charge levels
  • Emergency lights and auxiliaries need power to operate

In order to maintain power and HVAC to the ambulance, EMS crews have historically run the ambulance’s engine. This practice is known as “idling,” and there are a number of significant drawbacks.

Idling wastes fuel and increases pollution. For ambulances, idling wastes about 1.5 gallons per hour. Over the course of a 24-hour shift, that’s 36 gallons that could’ve been better spent on transportation and not idling. Similarly, the emissions from gallons spent idling are significant; an ambulance idling for an hour puts 33 pounds of carbon dioxide into the air. Additionally, the engine wear from constant usage decreases ambulance life and necessitates upkeep and replacement costs sooner.

Given that idling has multiple downsides, technologies to avoid idling are important to discuss and implement.

The suite of technological solutions to decrease idling is known as Idle Reduction Technologies.

There are three main types of idle reduction technologies suitable for ambulance usage: Auxiliary Power Units, Electrified Parking Spaces and Solar Panels.

Auxiliary Power Units, or APUs, are battery units that provide power to auxiliaries like medical equipment, refrigerators and HVAC systems when the ambulance engine is shut off. These units save an average of 1.5 gallons per vehicle hour, and their diversion of gases like carbon dioxide is good for EMS crews and patients, as well as for the environment. Companies like Stealth Power and ZeroRPM specialize in APUs for emergency response vehicles, including ambulances.

The Memphis Fire Department has used APUs as its mode of idle reduction to great effect.

In 2020, they contracted with ZeroRPM to install an APU in one of their ambulances to test the technology. In the period from August 2020 to August 2021, the idle reduction numbers were as such for that trial ambulance:

  • 2,318 hours of idle mitigation per year
    • That’s 6.35 hours of idle mitigation per day
    • Or 381 minutes of idle mitigation
      • Just over 70% of idling time reduced per year
  • 2,170 gallons of diesel use reduced per year
  • $6,000 dollars in fuel saved per year
  • 23.94 short tons of CO2 reduced per year
  • Savings in preventive maintenance due to less engine wear-and-tear was estimated at $1,500 per year

Lieutenant Jonathan Haley of the Memphis Fire Department spoke with Middle-West Tennessee Clean Fuels. He explained that the APU technology exceeded expectations in fuel, cost and emissions savings and the Department quickly added ZeroRPM to all of its new ambulance contracts when they saw the initial numbers.

MFD now has five ambulances with APUs, and an order for another seven to be completed by end of 2022. By the end of the year, ambulances equipped with APUs will constitute 33% of their fleet.

A ZeroRPM unit within its compartment in a Memphis Fire Department ambulance; Credit: Lieutenant Jonathan Haley, MFD

Additionally, Lieutenant Haley detailed that the on-the-ground experience for ambulance crews with APUs has been positive. The absence of emissions from the ambulance’s exhaust, coupled with the lack of diesel noise, improves crew health and makes it easier to work with patients around the ambulance.

Lieutenant Haley explained MFD’s greatest takeaways from APU usage:

“As everybody realizes that we need to move to sustainable practices, we’re trying to do our part and given the technology available for ambulance operations currently, ZeroRPM was a great entry point for us. It was accessible and easily implemented. And after we saw the cost benefits, they were significantly favorable. It’s a win, and the proof is there and it’s working for us. We’ll keep doing it and keep looking for other opportunities to move the needle and get to a green fleet.”

The Memphis Fire Department’s example has been a great success story in APUs and their ability to curb idling, fuel usage, costs and emissions.

Electrified Parking Spaces, or EPS, are stationary pedestals that ambulances can use to provide electricity or HVAC support to their ambulance while they sit at a predestined location.

Typically, EPS are deployed outside of hospitals or firehouses—wherever an ambulance is likely to rest and wait for a call. For electricity, EMS operators can plug in; for HVAC only, a tube can be inserted in the ambulance window to provide necessary climate control.

Installation of a connection port on the ambulance is necessary, and the plug is designed to automatically disconnect if the ambulance needs to quickly drive away.

Solar Panels can also be installed on ambulance roofs to store solar power while the ambulance is driving and resting in the sun. The stored power can then maintain electrical systems while the engine is shut off. This solution is less often utilized but can be very effective in sunny climates.

These idle reduction technologies have the potential to save money and fuel, improve individual and community health outcomes, and change the way that ambulances idle. By adopting new technologies, idling ambulances are just as prepared and better designed to make efficient use of their fuel.


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