Cooling Systems & Emission Controls
By Marek Krasuski
Despite current weather conditions summer is fast approaching and with it are thoughts about air conditioning systems to provide cool comfort for drivers during summers that are becoming longer and hotter. But they come with a cost.
A vehicle’s air conditioning system can increase fuel consumption by up to 20 percent because of the extra load on the engine. Load stress depends on vehicle size, outdoor temperature and other conditions.
With climate change underway the industry has been vigorous in reducing emissions as much as possible, so electrically powered auxiliary power units (APU’s), devices that provide additional energy, are looked upon favourably. Battery powered systems are quiet and relatively maintenance free compared to diesel run APU’s that require maintenance – oil changes, filters – around every 500 hours. The fuel required to operate an APU is less than running the truck of course, but has typically been viewed as more energy intensive than battery operated alternatives. Yet the advantage of diesel powered APU’s is their longer running cycles.
As battery technology improves however, their running times are extended as well. Carrier Transicold’s ComfortPro electrically powered auxiliary unit, for example, will cool a cab with zero emissions, promise a long lasting running time of about 11 hours and generate 7,500 Btu/h of air conditioning. The units are powered by four absorbent glass mat batteries with power replenished from the truck’s alternator. For many, electric powered APUs are preferable to their engine-driven counterparts as there are fewer moving parts to change, and no oil or fuel filters to replace.
Yet while upgrades are made to battery technologies that extend run cycles on electric APUs, diesel powered APUs are becoming more efficient. Carrier Transicold, for example, has updated its ComfortPro diesel powered units along with its electric APUs. The updates reduce maintenance time and extend service cycles to twice their previous intervals. The ComfortPro diesel APU provides air conditioning, engine warming and battery charging, among other functions, with 12,000 Btu/h of cooling power and 10,000 Btu/h of heat.
Webasto is another provider of vehicle air conditioning products. These systems charge the cold accumulators during the vehicle’s movement. Cold temperatures are then emitted when the vehicle is parked. Among Webasto’s product choice is the Cool Top RTE 10. The system is easily installed in the roof of the cab, the compressor driven system is prefilled with refrigerant and connected to a 24 volt battery. This electric parking cooler reduces engine idling time and saves fuel. The Cool Top yields high energy efficiency thanks to a powerful cooler system. The electrically powered unit means there is no fuel consumption, and low voltage cut-off assures problem free starting as little power is drawn from the engine. Webasto also provides the Rooftop system ranging from 3.5 to 6.2 kW. The Rooftop is ideal for off road applications and can be used in construction and agricultural vehicles, ambulances and firefighting equipment. The Rooftop is easy on fuel consumption thanks to lightweight materials, offers high aerodynamic efficiency, and has a compact design that makes for easy installation in various cab configurations.
Both diesel powered and electric powered APUs should meet most cooling needs, as long as some forward thinking supports their use. Drivers claim that closing the cab curtains before shut down for the day keeps the sun out and the cab cooler, drawing much less power than repeatedly turning on and off the unit.
For several decades Autoclima has been a leader in the design and manufacture of air conditioning systems for vehicles. Today it provides equipment for the over the road market and for vocational applications, among others. Suited for earth moving machines and agricultural vehicles Autoclima has six product offerings. The Modula is an electrically driven unit powered by 12V/24V power outlet or by a hydraulic power feed. The Modula derives its namesake from its modular configuration that enables flexible installation. The Modula is available in three product offerings – the Modula RT, Modula MK and Modula MC.
For the crane operator Autoclima features the Compact electric unit ACW 50. This 220V vertical unit consists of a condenser, evaporator and hermetic compressor and is suitable for severe environments such as high concentrations of micron particles. An alternative, the portable, easily installed Roof Top unit RT 40 works well for cooling small interior spaces like tractors and small trucks, similar to the Roof Evaporator RE 50, also lightweight, compact and easily installed. Autoclima also offers aftermarket products for delivery and long haul trucks. In Canada Wajax, through its extensive dealer network, supplies the Fresco system which Autoclima describes as follows: “The Fresco battery powered no-idle air-conditioning systems are the most efficient truck air-conditioning systems available today. The Fresco 6000 requires no diesel fuel, requires minimal seasonal maintenance which dramatically reduces vehicle operational costs, while ensuring a well-rested driver each day through maximum climate comfort.”
Choosing an electric or diesel system depends on a number of factors – air temperature, humidity, solar irradiation through windows, cab size, driving mode of vehicle. Parcel service vehicles with frequent opening and closing of side doors, for example, are likely to demand more power than long haul trucks where engines operate steadily and continuously over longer periods and cabs are closed longer. Still, there is no denying there are advantages to both systems. Diesel powered units produce virtually unlimited power for cooling. Battery powered alternatives on the other hand have the advantage of running quietly, but with limited run times before recharging. This can be especially difficult for drivers running in climates with hotter temperatures. In such cases some drivers complain they have to run the truck engine for longer periods to recharge batteries. And insufficient cooling during overnight breaks have led some operators to migrate toward diesel powered systems as the preferred choice.
Regardless of preference, driving all developments in truck technology is the desire for continuous reductions in emissions. Over the past two decades the industry has invested billions of dollars in reducing particulates and smog emissions, chiefly through Selective Catalytic Reduction (SCR) or Exhaust Gas Recirculation (EGR). EGR technology cools diesel exhaust which it circulates back into the engine where emissions are eliminated in-cylinder. The advantages of Advanced EGR are no additional costs associated with the purchase of liquid Urea (required with the Selective Catalytic Recirculation method), increased payload capacity, and improved efficiency. The Selective Catalytic Reduction (SCR) method is distinguished by the treatment of N0x outside the engine as opposed to the in-cylinder treatment in the EGR system.
Notwithstanding the industry’s commitment to environmental improvement, further controls are being considered in Ontario. A policy proposal outlining changes to the heavy-duty truck emissions policy is underway and currently posted on the Ontario Environmental Registry at ero.ontario.ca/notice/013-3867. Proposals include: a mandatory test of a vehicle’s on board diagnostic (OBD) computer-based emissions controls; reviewing the appropriate vehicle test age and test frequency; reviewing the test standard for visible emissions opacity; increased enforcement of existing anti-tampering restrictions with regard to emission control systems that are in current regulations; and providing incentives to industry stakeholders who consistently demonstrate cleaner fleets.
Since 1999 emissions from light duty vehicles have declined, but the province says emissions from heavy duty trucks have not decreased as rapidly because of less stringent emissions standards and the existence of older vehicles on the road that produce unacceptable emissions levels. It is hoped that changes to the emissions control program will help in identifying non compliant operators who use aftermarket kits to undermine environmental controls.
In addition to tougher emissions enforcement the Ontario government will commit $400 million over four years toward enhanced emission measures. These include the adoption of low carbon fuel technologies, and the expansion of compressed natural gas (CNG) stations in the trucking sector along 400 series highways.
Since 2000, new engine builds have progressively contributed to lower emissions of diesel exhaust and soot. And though efforts have been stymied by older trucks still on the road and by non-compliant operators, new enforcement measures are likely to generate greater compliance and lower emissions.☚