Issue link: http://read.dmtmag.com/i/348131
I DA U N I V E R S A L J u l y -Au g u s t 2 0 1 4 52 or the past decade, the drive to reduce diesel exhaust emissions has dominated the headlines. But with the last EPA mandated deadline of 2014 for Tier 4 Final engines here, the war is over, and a new front has opened in the drive for cleaner, greener equipment. e new technology trend for heavy equipment is the merger of diesel engines with electric drive trains. Unlike exhaust emissions technology, which currently stops with Tier 4 Final, the diesel-electric revolution is just getting started. More work, smaller engines Diesel-electric and hybrid drive systems have in com- mon the capability to run with a slightly smaller engine at a lower rpm. is translates into fuel savings, fewer PMs and longer engine life. But that's just the beginning. Electric drive systems have an infi nitely variable power band. Lugging the engine and redlining the tach become things of the past. Some proponents of diesel- electric earthmoving equip- ment are also promising that, with all the surplus electric power being generated, they may be able to do away with alternators and electrify the components that normally hang off the serpentine belt such as lube, AC and water pumps, thereby greatly reducing parasitic loads. Cummins offi cials even hinted that it might be possible one day to drive hydraulic imple- ments with hybrid electricity instead of fl ywheel-powered hydraulic fl uid. Manufacturers at this year's ConExpo-Con/Agg showcased a number of diesel-electric and diesel- hybrid prototypes, but also on display were a handful of machines that have already proven their worth in the dirt. ese include Cat's D7E electric drive dozer, Komatsu's HB215LC-1 hybrid excavator and John Deere's 644K elec- tric hybrid wheel loader. e Cat D7E is an electric drive dozer, not a hybrid, since it doesn't recapture energy from other systems. Rather, it uses a Cat C9.3 diesel engine to convert mechanical energy into AC electrical current, which powers the fi nal drives and generates DC current for the accessory systems. anks to the electric drive motor, there is no transmission or gears in the driveline, and the power out- put and speed are infi nitely variable. Alan Quinby, superinten- dent, Durango Services, Woodward, Oklahoma, took deliv- ery of his fi rst Cat D7E dozer three years ago and has added three more to the fl eet. Fuel economy o driv i