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The issue of after-treatment
In terms of the schedule for emissions reduction, the EPA’s Tier system, Tiers 1 and 2 are passed and Tier 3 will be completed throughout 2010. Advanced in-cylinder combustion technology provides emissions solutions for all three Tiers. Tier 4, which has entered an interim stage, is concerned primarily with exhaust after-treatment. Selective catalytic reduction (SCR) systems have been gaining ground here as well as after-treatment technology that uses advanced regenerative filters, but dealing with emissions at this stage comes at a high price.
States Payne: “After-treatment strategies add considerable costs and complications for end users. It makes no sense to spend money on them when the problem can be addressed much earlier on. Our philosophy is to discharge the problem in the first place.”
There are many applications out there that utilise diesel generator sets only for emergency, standby. The EPA defines emergency standby as an internal combustion engine whose operation is limited to emergency situations - and up to 100 hours per annum for testing and maintenance. It is understood in the US that it does not make sense to force after-treatment for this kind of operation. It is assumed engines in this category hardly ever run and so emissions, by definition, are not a major issue.
“There is another more obvious motivator to invest in low emissions technology.” Says Payne, “As we make improvements we enhance engineering in other ways too, such as smaller, lighter components and fuel efficiency, all of which are worthwhile. The challenge is to find the right technology to meet the customers’ needs - not just emissions targets.”