Almost A Hybrid
By Bill Moore
Wouldn't it be ironic that hybrid-electric cars will become the norm not because of concerns over the environment or fuel economy - after all how many really care about such things - but because of an increasing hunger for more and more gadgets on our cars?
Given developments both in Europe and North America, that is not as strange a scenario as it first appears to be. According to the latest issue of Automotive Engineering magazine, the demand of electricity onboard the average car has grown from 500 watts in 1970 to 2,000 watts in the 2001 model year. In the last five years the demand has grown at a rate of 100 watts per year, and according to Visteon Corporation electrical demand in the next decade could approach 10,000 watts, far outstretching the capabilities of today's14 Volt, alternator systems.
Where is all this power going to be used? Here'sa short list of the more power-hungry components on tomorrow's cars:
- Active suspension … 12,000 watts
- Electric air conditioning compressor… 4,000 watts
- Electromechanical value control… 3,300 watts
- Catalytic heating… 3,000 watts
- Heated windshield…2,500 watts
- Brake-by-wire… 2,000 watts
- Heated front seats… 2,000 watts
- Steer-by-wire…1,800 watts
- Power seats… 1,600 watts
Moving Towards 42 Volts
Given these levels of power, automotive engineers are quickly moving towards a 42-Volt power architecture on the cars and trucks of the new decade. It is believed this architecture will make it possible to accommodate a car that requires as much as 10,000 watts, roughly equivalent to the energy demand of the typical American home at peak loads.
But adapting a 42 V system presents its own set of challenges, not the least of which is how do you generate that level of electricity while still meeting evermore stringent fuel efficiency and emission standards.
Engineers are still wrestling with what the underlying architecture will look like, whether they will use a single 42 V system or a dual voltage system that makes use of both 14V and 42V architectures. While the single 42V system appears the simplest on paper, it is the hardest to implement in practice. What may evolve is dual system with parallel architectures and storage batteries.
Equally daunting is the task of generating all that electricity. Today's Lundell alternators simply aren't up to the task. So, what firms like Visteon, Delphi, Mannesmann Sachs, and Siemens are doing is looking at switching to integrated starter alternators or ISA systems on internal combustion engines. In effect, what they are experimenting with are devices that bear a remarkable similarity to hybrid-electric drive systems in the Toyota Prius and Honda Insight.
Norman L. Traub, Technology Integration Manager at Delphi is reported to have stated that the introduction of ISA marks the beginning of a 20-year technological revolution that "will change the cars we drive." It's a surprisingly short path from ISA to THS (Toyota Hybrid System) or IMA (Honda Integrated Motor Assist). Automotive Engineering calls this approach, "light hybrids."
ISA systems, like the Visteon system pictured above, will serve both at the engine starter and power generator. Interestingly, Visteon touts one of the benefits of the system is "Instant Start". Like Honda's IMA or Toyota's THS, an ISA-equipped vehicle will be able to automatically turn off its IC engine while stopped in traffic and instantly restart the motor when the driver depresses the accelerator or puts the car in gear.
The power to restart the motor instantly has to come from the vehicle's battery system and here the parallels continue with today's gasoline-electric hybrids. One of the leading candidates, currently, is spiral wound technology using an absorbent glass mat or AGM-based 36 V battery. Also under consideration are more advanced batteries including NiMH and Lithium-ion. There is also talk of introducing regenerative braking into ISA-equipped vehicles and using ultra-capacitors to capture the energy.
Increasing the electrical power demands of the vehicle also increases the demands on the engine, so one approach being considered is the use of small fuel cells as auxiliary power units or APUs to produce the electrical current needed. This approach reduces the total emissions from the vehicle by letting engineers reduce the size of the main power plant while creating virtually no emissions from the APU, itself.
Siemens projects that sometime around 2006, 14V architectures will begin to be phased out with 42V systems becoming the dominant voltage architecture by 2015 to 2020. The 42 V system could result in a 5-12% increase in fuel economy and a 10-15% drop in emissions.
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