Simanaitis Says

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BACK IN the 1970s, Mazda made the excellent point that conventional engines went “boing boing boing,” whereas its rotary powerplant went “hmmmmmm.” Today, high-efficiency laundry facilities may go “hmmmmmm” as well. So say researchers at the Advanced Power and Energy Program (APEP), University of California, Irvine; its partner, Mazda North American Operations and Racing Beat, a legendary Mazda speed shop.


At the heart of this research is DG/CHP, an acronym for Distributed Generation/Combined Heat and Power, a concept that’s made to order for more than 8000 laundry facilities throughout California, an estimated 3700 of which are in the southern portion of the state.

Here’s how each of these terms comes out in the wash: As its name suggests, distributed generation has independent electrical production at a local level, with several benefits. First, DG’s nearness to its user eliminates the 8 to 10 percent losses incurred in conventional long-line electrical distribution. Second, its specificity of use promotes efficiencies peculiar to that application. Third, DG’s modest scope offers advantages of funding, on-site construction and operation compared with those of traditional power plants.

Combined heat recovery augments these DG benefits. Typically, heat is a byproduct of any energy generation. Rather than waste this heat, why not capture it for useful purposes? What’s more, the routing of these heat sources can be efficiently combined in distributed generation. Hence DG/CHP.

The APEP-devised DG/CHP (there’s an acronymic mouthful!) uses a Mazda rotary engine converted to natural gas with a multi-point low-pressure injection. Natural gas has its existing supply infrastructure and an inherently good emissions profile in use. A stock Mazda three-way catalytic converter was originally fitted, now replaced by one that’s natural-gas optimized for even lower emissions.


The Micro DG/CHP System. Image from APEP Bridging: Engineering Science to Practical Application, Annual Report, Volume 3, 2015.

This diagram provided by APEP shows how CHP enhances DG operational efficiencies. With ordinary liquid-cooled internal combustion, 25 percent of its heat of operation is carried away by the coolant and oil to the radiator and oil cooler, then dissipated into the atmosphere through heat exchange. Another 30 percent of the heat exits through the exhaust pipe. Thus, this 55 percent of thermal energy is as wasted as the typical 23 percent of an engine’s radiated heat losses.


By contrast, consider a CHP’s application in powering a laundry facility: The DG engine’s hot oil and coolant exchange their heat with the laundry’s water storage tank. Otherwise, the latter would have to be heated by an auxiliary gas or electric source. Similarly, the DG engine’s exhaust is routed to exchange its heat with air used in the laundry’s dryers. All the while, of course, the DG is providing the laundry facility’s required electricity.

APEP and Racing Beat specialists tuned and tested the unit using an engine dynamometer at the latter’s Anaheim, California, shop. In terms of fuel in/electric power out, the Mazda rotary’s thermal efficiency was measured at 22 percent. Its emissions of NOX and CO were less than 2 and 12 parts per million, respectively, both showing the cleanliness of natural gas operation and efficacy of optimized catalytic converter.

Last, the system’s overall thermal efficiency—its electric power and recovered heat divided by fuel consumed—was calculated to be greater than 75 percent. APEP researchers concluded that such low-cost small-scale DG/CHP units could satisfy a variety of electrical needs exploiting these benefits of distributed power and heat recovery. In time, more than laundry facilities might be going “hmmmmmm.” ds

© Dennis Simanaitis,, 2015

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