It’s probably no secret to fleet managers that idle time can significantly affect a vehicle’s fuel efficiency. In “Secrets of Better Fuel Economy,” a white paper offered by Cummins, the engine manufacturer explains just how detrimental unnecessary engine idling can be to the bottom line.
“Every hour of idle time in a long-haul operation can decrease fuel efficiency by 1%,” the paper states. “Idle/PTO fuel consumption increases exponentially with engine speed.”
Details in the Cummins paper include the following fuel consumption rates at idle:
• 650 RPM = 0.5 gallons per hour
• 1,000 RPM = 1 gallon per hour
• 1,200 RPM = 1.5 gallons per hour
Engine manufacturer Detroit Diesel notes that along with other fuel-efficient habits, it’s critical to educate drivers on the role of shorter idle times. “Optimizing driver habits alone can improve fuel economy by up to 30%,” the company says.
Detroit also points to the importance of electronics that can be set to automatically shut down an engine after a specified period of idle time to save fuel, reduce excessive engine wear and prevent additional pollution.
While costly, idling often is necessary to maintain cab and sleeper compartment temperatures. Now offered by truck OEMs as original equipment, and from a variety of manufacturers for new and aftermarket installation, are auxiliary cab and sleeper heaters, some with engine heating capability, and full auxiliary power units (APUs) that offer heating, cooling, accessory power, battery charging and engine heat, as well as other technologies.
Autotherm Energy Systems‘ no-idle vehicle interior heating system can be installed on any vehicle powered by a water-cooled internal combustion engine. The patented system needs no periodic maintenance. Once turned on at the beginning of a day, it operates each time the engine is turned off by enabling the vehicle’s existing heater to operate and recover waste heat energy in the coolant.
Bergstrom’s NITE Phoenix battery-powered no-idle system features onboard service diagnostics, automatic temperature control, a check filter function, and an LCD digital user interface and battery monitoring system that make it easier for drivers to control the unit.
Carrier APU, an integrated cooling and heating system, provides up to 12,000 BTU/hr of cooling and 10,000 BTU/hr of heating. Its generator delivers 4 kW of power for accessories. The Carrier APU charges truck batteries, warms the truck engine and is compatible with shore power. Designed for maintenance ease, its service interval is 1,000 hours and changing the oil and oil, air and fuel filters can be done in less than 15 minutes.
Dometic battery-powered sleeper HVAC systems provide up to 10 hours of engine-off air conditioning. The integrated system includes a 10,000 BTU compressor/evaporator unit normally installed beneath the bunk, a condensing unit mounted on the back of the cab, a DC-AC inverter, a high-performance alternator, a bank of absorbed glass mat batteries and a digital control/display unit. Dometic also offers a specially-designed system for day cabs. All systems are CARB compliant.
Dynasys APU utilizes R134a hermetic-style AC and electric heating. The unit generates 6,000W of power from a belt-driven generator. The system also provides 12V DC power from a separate 55-amp alternator for operation of the APU control system and to provide charging capacity for the main truck engine batteries. Risk-free fleet trial programs are available.
Espar Heater Systems‘ independent auxiliary fuel-fired air heaters range from 7,500 BTU/hr to 41,000 BTU/hr and coolant heaters range from 13,700 BTU/hr to 120,000 BTU/hr. Espar’s Airtronic D2 bunk heater runs on diesel fuel and draws less than an 1 amp/hr of power on average from the 12-volt battery system. The heater has four heat levels and cycles between these levels according to the temperature desired by the driver.
Idle Free Systems‘ electric APU meets heat, air conditioning and hotel power needs. Idle Free’s system is an alternating current-based electric APU, which translates to longer battery life and no need to use the truck’s starter batteries to power the unit.
Parker Fluid Control Division’s Industrial Climate Control Solution offers an on/off solenoid valve with terminations that plug into trucks’ auxiliary equipment to regulate heating and cooling systems, allowing drivers’ cabs to keep warm or cool without idling engines. The two-way normally closed/open brass valve comes with an orifice diameter of ½-in. or larger and with ½-in. NPT.
PonyPack is an APU that provides heating, cooling, engine warming and battery charging. The patented unit transfers engine exhaust heat to the antifreeze to keep the truck engine warm while an inline pump installed in the cab heater core supply hose circulates hot coolant to heat the cab and sleeper. For cooling, the PonyPack compressor and condenser uses existing evaporators, ductwork, blower motors and panel controls. The APU also features a 110-amp alternator to keep batteries charged for on-board devices.
Thermo King TriPac Evolution auxiliary power units can be ordered after April 1, 2013 for shipment in the second quarter of 2013. The new model meets Tier 4 Environmental Protection Agency final regulation requirements using new patented technology. The updated TriPac APU features software that can be customized to each customer’s operating profile. This unit also has an extended maintenance interval of 1,500 hours, a new flash-loadable control system, and improved service access for easier maintenance.
Webasto’s Tandem 717 heating system combines the benefits of the Air Top 2000 ST air heater and Thermo Top C coolant heater for a total vehicle solution. The Thermo Top C provides engine pre-heat without idling and eliminates cold starts. The Air Top 2000 ST warms the bunk without idling.
Willis Power Systems offers a complete line of APUs including the GenForce 14 HP, 2 cylinder engine, 15,000 BTU A/C and heat unit; the Compact Willie 20 HP, 3 cylinder engine, 30,000 BTU A/C, 28,000 BTU heat model; and the customizable Premium APU with Willie specs plus a choice of a hydraulic pump or an air compressor.
Trojan Battery engineered its OverDrive AGM 31 battery to operate electric APUs. OverDrive batteries feature robust plates, effective paste formulation and grid designs to extend deep-cycle battery life and performance in electric APUs. The Trojan deep-cycle battery designed specifically to support electric APU applications has the ability to provide 730 cold cranking amps.
APU field test
In an evaluation of 10 of its 230 Class 8 trucks, FTS International (FTSI), a Texas-based provider of services and products to the oil and gas industry, set out to determine how much fuel could be saved by using APUs. The test utilized Hodyon’s Dynasys auxiliary power unit.
FTSI studied average idle hours per day, the percentage of idle hours in 24 hours and idle costs based on an average of $3.95 per gallon. Cost savings per day was determined as the difference between fuel burned during idle time prior to using the APU compared to fuel burned during idle with the APU. Reduction in idle time varied based on driver behavior, types of loads or other factors.
• A decrease in average idle hours per day from 10.85 before the APU was installed to 2.26 after installation.
• The percentage of idle hours in 24 hours dropped from 45.1% to 9.6%.
• Daily idle costs were reduced from $63.63 to $11.78.
• Fuel used per idle hour dropped from 1.25 gallons an hour to 0.230 gallons per hour.
• The average savings in idle time for the 10 tractors was 77%.
• The average cost savings per day was $41.58 and the average cost savings per year was $12,474.85.
Extrapolating those calculations to 223 tractors, FTSI determined a daily cost savings of $9,272 and annual cost savings of $2,781,891, and based on the analysis made the decision to equip its entire fleet with APUs.
Shore power, the use of electricity to operate in-cab systems without idling, is already a proven technology. For trucking companies, this system is increasingly attractive, requiring nothing more than a heavy-duty extension cord and a facility-based system. Truck manufacturers are incorporating shore power-ready connections into electrical and auxiliary battery-powered systems as factory-installed options.
IdleAir offers dedicated facilities at terminals as well as IdleAir Truck Stop Electrification at a growing nationwide network. The service includes air conditioning and heat, electricity inside and outside the cab, Internet, and DirecTV. Discounted fleet rates are available.
The Shorepower Truck Electrification Project (STEP), funded by the U.S. Department of Energy and administered by Cascade Sierra Solutions and Shorepower Technologies, is deploying shore power at 50 truckstops along major freight corridors across the country.
Unnecessary idling is a major contributor to diesel fuel costs, and truck idling is a cause of harmful emissions, as well as noise. That has led states, provinces, metropolitan areas and municipalities across the U.S. and Canada to enact strict regulations that limit the time trucks may idle.
At the same time, truck fleets continue to need to provide drivers with comfort and convenience during on-duty non-driving time periods. Rested drivers are not only safer drivers—cab comfort also is helpful in attracting and retaining drivers, and keeping costs for those activities in check.