Issue: Mar 2009


LOW COST CAPACITORS IMPROVE OUTLOOK FOR MICRO HYBRID



by Bob Brooks

The outlook is improving for non-lithium micro hybrids (largely stop/start systems), which refers to low cost, simplified hybrid technology and not to micro size cars. Micro systems will benefit from new low cost ultracapacitor technology developed by Monolith Engines Inc. Waukesha, WI, as consultants to capacitor maker Maxwell Technologies, San Diego, CA.

Monolith President, Tom Dougherty, until recently director of advanced battery and hybrid systems at Johnson Controls, Milwaukee, WI, explains that the virtues of ultracapacitor energy storage for hybrid and electric vehicle systems has long been recognized by vehicle engineers. Capacitors can intake and discharge energy very quickly and operate efficiently at low temperatures. These virtues are the opposite of batteries which have low power at low temperature and intake/discharge at slow rates. The two work well together. Chrysler battery engineer, Steve Clark, tells Automotive Industries that Li-Ion battery output, for instance, is reduced 50% at 0 deg.C and by 90% at –30 deg C

The stumbling block faced by ultracapacitor for major use in passenger cars has been high cost which Dougherty has solved by a new high volume manufacturing system that eliminates six of the ten steps now commonly used to make ultracapacitors. Dougherty forecasts cost to be a fraction compared with current capacitor production methods and materials.

Dougherty describes a vehicle system (essentially stop/start) for typical mass market cars as having a deep discharge lead acid battery (half the size of today’s common auto battery) in the back of the car (away from engine heat), a 10 lb. ultracapacitor pack (see exhibit) in the engine compartment but isolated from direct engine heat, a belt driven starter/alternator (to replace separate starter and alternator) and DC to DC converter with 42 volt operating system..

Maxwell VP John Miller tells Automotive Industries that an 18 unit 10 lb pack can provide 20 kW for 1.5 seconds or 5 kW for 6 seconds which is several times higher power than provided by current stop/start systems. It appears the system may permit economic energy in addition for some degree of launch assist.

Dougherty sees the potential for significant vehicle fuel efficiency gains without expensive large battery hybrid systems by greater use instead of ultracapacitors combined with engine downsizing, dual variable valves and long stroke gasoline engines which Toyota uses in its new 1.33L Auris(Corolla size) car. The 1.33L Auris with a current production stop/start system has reportedly demonstrated nearly 45 MPG per the combined unadjusted FTP test equal to 19% improvement over the standard 1.4L car. The Daugherty/Maxwell system goes beyond current technology yet is highly cost/effective and easily applied to 80% of mass market cars without basic design changes, says Dougherty. On an equal test basis, the Auris 45 MPG value compares with the U.S. vehicle Federal target of 35 MPG by year 2020

.A concern impacting the outlook for hybrid cars based on large lithium batteries is political instability in Bolivia which produces nearly half of world lithium supply. Published reports suggest that U.S. efforts to reduce its dependence on imported petroleum by changeover to vehicles with large lithium batteries may be at risk of the petroleum problem being replaced with dependence on increasingly expensive imported lithium. This in turn puts greater focus on more affordable optimized conventional automotive engines combined with ultracapacitors and non-lithium batteries.


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