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ISE Gasoline Hybrid Drive Systems to Power New 35’ and 40’ Buses for San Diego MTS
1 February 2008
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| Energy flow in the Thundervolt hybrid drive. Click to enlarge. |
New Flyer Industries has been awarded a contract to provide hybrid buses equipped with ISE’s gasoline series hybrid drive systems to the San Diego Metropolitan Transit System (MTS). ISE has received an initial order from New Flyer Industries for the supply of 12 gasoline hybrid drive systems to be delivered in the third quarter of 2008.
The Metropolitan Transit Development Board (MTDB) authorized the purchase of up to 20, 35-foot gasoline hybrid buses for delivery this fall, and up to 350, 40-foot CNG or gasoline hybrid buses over the next five years.
The ISE Thundervolt hybrid drive is a full series architecture, and has five major subsystems:
Motive Drive Subsystems: electric drive motors, motor controller, gear reduction system, driveline, and related components. The ThunderVolt motive drive subsystem is based on an ELFA dual motor and controller set manufactured by Siemens AG. The ELFA drive configuration includes two motors and a combining gearbox providing a flange for a driveshaft to the differential.
The motors and the inverter module that controls them are both operated on the same water-glycol cooling loop. The dual motor/controller set has a power rating of 170 kW continuous and 288 kW peak. Rated torque is 440 Nm (220 Nm per motor) and peak combined torque is 900 Nm.
The combined weight of the two drive motors and combining gearbox is approximately 300 kg. Each inverter module weighs 72 kg. Buses up to 30 feet in length can be operated with a single inverter module.
Auxiliary Power Units (APU). ISE considers the engine, electric generator, and related components auxiliary power units. The standard subsystem for ISE bus applications consists of a conventional diesel or gasoline engine, coupled to a Siemens 150 kW generator through a Stiebel gearbox. The generator is controlled by a Siemens inverter identical to the main drive motor inverters with the exception of its software. The combined weight of the generator and gearbox is approximately 215 kg.
The APU is sized to enable a 40-foot bus to perform efficiently in local stop-and-go driving at grades up to 17%.
The gasoline variant—ISE also offers diesel, natural gas and hydrogen versions—uses a Ford 6.8 liter V-10 gasoline engine that produces 305 hp and 405 lb-ft or torque. In October 2003, ISE’s gasoline hybrid drive system was certified by the California Air Resources Board for use in transit buses, to an emissions rating 0.4 grams of NOx per brake horsepower hour - making this ISE drive system the first hybrid drive system to be certified by the ARB for use in buses or heavy-duty trucks.
Energy Storage System: integrated pack of batteries or ultracapacitors. ISE offers either 17.8 kWh Zebra nickel sodium chloride battery packs and/or ultracapacitor packs from Maxwell (400 A per pack with capacitance of 18.05 F, peak voltage of 403 VDC). Monitoring, charging, equalization, and thermal control elements are included with both battery and ultracap versions.
Vehicle Control and Diagnostics: hybrid energy management controllers, dashboard displays, remote diagnostic tools, and related components. ISE has developed a proprietary system control architecture for use with the ThunderVolt drive system.
ISE has invested considerable effort into its series hybrid energy control system. In close collaboration with Siemens, it has focused recently on closed-loop generator control and a new rapid engine start/stop technology enable by this procedure.
Closed-loop generator control enables the operation of the combustion engine at virtually any speed while supplying a constant bus voltage. This increases the efficiency of the drive system because we can operate the engine at maximum load. Competing hybrid systems change engine speed to adjust their intermediate bus voltage, which becomes increasingly inefficient under partial or no load, according to ISE.
Furthermore, the closed-loop feedback enables the ISE hybrid system to automatically stop the engine whenever its operation is unnecessary, such as during stops when the engine would otherwise be idling. The engine is then restarted with the generator, increasing starter life. This can be achieved without injecting fuel, which cools the engine down rapidly to reduce heating. This process facilitates operation in the all-electric mode, when the vehicle operates solely on battery power.
Another feature of the ISE closed-loop process is the ability to operate in a mode in which the generator energy is directly transferred to the drive motors, bypassing the batteries. This operating mode improves battery life by reducing the number of battery charge/discharge cycles. It also enables the ISE hybrid system to function in the event the batteries become unusable for any reason, providing added redundancy. With the 160 kW Siemens generator, degradation of vehicle performance in the event of a battery failure is modest.
The amount of battery energy used can be adjusted to the type of operation by changing hybrid control parameters, even on the fly. For example, the system can be optimized to achieve absolute maximum fuel economy by maximizing dependence on the battery packs, or adjusted to maximize battery life by using the battery energy more sparingly when fuel is cheap or more readily available.
Electrically-Driven Accessories: electrical power steering and braking systems, air conditioning systems, and related components. These subsystems derive power from the main battery pack when the APU is not running, so there is no loss of functionality when the bus operates in its all-electric mode. The electric accessories also enable more efficient operation of the power steering, power braking, and heating/ventilation/air conditioning (HVAC) systems.
ISE estimates that this reduces aggregate power demands on the drive system by at least 15 horsepower.
Serving approximately three million people in San Diego County, MTS provides bus and rail services directly or by contract with public or private operators with 82 fixed-bus routes operated by SDTC, MTS Contract Services, and Chula Vista Transit.
New Flyer is excited to expand its leadership in clean, environmentally friendly transit buses by providing hybrid buses equipped with ISE’s gasoline hybrid drive to the sixth largest city in the US, San Diego. As the first to launch the ISE gasoline hybrid system in the industry, and with over 300 orders and options for the systems prior to this award, the ISE product has been a successful new product for the transit industry.
—John Marinucci, CEO of New Flyer Industries
February 1, 2008 in Heavy-duty, Hybrids | Permalink | Comments (17) | TrackBack (0)
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Comments
Souldn't these HEV buses be (nano)safe?
Isn't ISE work in JV with Altairnano(Alti)?
http://www.isecorp.com/ise_news/ise_press_releases/may-30-2007-Altairnano.php
Posted by: Nanosafer EV | Feb 1, 2008 4:54:29 AM
The company Enova Systems(ENA) would have been the better choice for their application.
Posted by: c | Feb 1, 2008 5:43:08 AM
Interesting mix of SI and Imperial units.
A 6.8 litre gasoline engine, delivering 300HP, or about 220KW, seems overkill for a 170KW motor.
I thought the London Hybrid buses were using a 1.9 litre diesel engine. A big advantage is they can use a car diesel which has lower cost than a bus diesel. Because it operates in continuous mode, the wear on the diesel is less.
Also - do they plan to plug these in at night?
Posted by: Alex | Feb 1, 2008 6:43:49 AM
If they made them FFV to run on E85 that would be better, but there is probably no E85 in San Diego. Or, make them CNG diesel, but the LNG that the gas company brings into Ensenada, Mexico is going to the power plants. Maybe we need better coordination between energy producers, distributors and users.
Posted by: sjc | Feb 1, 2008 8:17:36 AM
There is a bus yard near here that has fairly new out of service buses that could be converted to hybrid. If they can convert a Lincoln maybe they can convert buses. The Lincoln cost $40k to convert and the buses would cost more, but it might be worth it.
There was also this article about converting SUVs to hybrid. It cost $7k and the SUV went from 12 mpg to 18 mpg.
Posted by: sjc | Feb 1, 2008 8:46:56 AM
Here is the web page for the conversion company.
http://www.salidaconversions.com/index.html
I am not trying to promote this company, but this is an idea that I had a while back and I thought it would be of interest to readers.
Posted by: sjc | Feb 1, 2008 9:07:15 AM
I was thinking that they could have used a smaller ICE myself at first. But with an electronic throttle gasoline engine, they may get better thermodynamic efficiency and/or emissions running at or near the torque peak with very large throttle angles. I would think that using a smaller engine and needing to actually rev up to the point of using peak power would raise cylinder temperatures quite a bit and at least harm NOx emissions. And when the ICE really is too big for the job, they can just turn it off until it's needed again.
There are no local sources of E85 and it would be hard to maintain the emissions profile. CNG is possible, but it adds a lot of bulk and weight.
As for London and other European city buses using much smaller ICEs, keep in mind that the drive cycle for an American transit bus, except for in a few places like New York City, is very different. They are expected to reach much higher speeds between stops, may make brief runs on highways, hillclimbs, etc. A smaller ICE could potentially still do the job, but only with much larger battery/capacitor arrays, which are a lot more expensive.
There's minimal return on grid-charging a vehicle like this. The battery pack usable capacity is 17 kWh. If you could fully deplete it before returning to the terminal overnight, you could grid-charge the 17 kWh in. As a charge-sustaining design, though, you'll likely only get to do half of that. That's only going to save about a gallon of gasoline a day per bus- nontrivial, but looking at the infrastructure cost to make them grid-chargeable and then to set up the charging infrastructure at the bus yard, I doubt they'd bother.
Posted by: Wes | Feb 1, 2008 9:31:15 AM
The flow of energy diagram is very informative. It would interesting to compare this with other series hybrid designs - do most of them route power through the battery first? That seems unusual.
This general site seems to indicate an energy path similar to the ISE design, with generator power split by power electronics between the traction motor and the batteries:
http://www.hybridcenter.org/hybrid-center-how-hybrid-cars-work-under-the-hood-2.html
It would also be interesting to see how the myriad of fuel cell cars route their power, since many of those cars could be considered glorified series hybrids.
Posted by: AES | Feb 1, 2008 10:16:10 AM
I do not look at it as through the battery. I view it as a several direct current sections. One is the direct current from the batteries to the inverter to drive the motor. One is from the alternator rectifier to the battery charge circuit. So what this says is that they have a path from the alternator rectifier to the inverter controller. That seems necessary in the case of the GM Volt or any series hybrid. When the genset is running it is providing power to the car and charging the batteries at the same time.
Posted by: sjc | Feb 1, 2008 10:46:47 AM
This seems to be a pretty logical approach - besides cutting down on battery cycling it would cut down on any inefficiencies in charge/discharge.
Posted by: AES | Feb 1, 2008 12:59:35 PM
Keen to see some development on placing the drive motors axially in place of the rear differential.
Eliminating the 90 degree drive will provide serious savings.
I am assuming that differential action and electric regenerative braking will all be included.
When CNG Is mentioned, although not described indicating a range of options are envisaged, we may assume a converted diesel with diesel igniter but plainly there is a preference for a ford v10 gasoline variant. This sounds overkill. Lack of confidence or just making sure, also if the options for size matching gen, E Motors, bus, etc are somewhat restricting.
If a workshop is already using a particular supplier or engine and is equipped for that in service, then it would make sense to stay close to that.
We are not seeing a complete ground up integrated design, and are simply not likely to for quite some time. Clever system design can work around this limitation and has great merit.
This way will provide maximum possibilities and versatility .
Good to see these vehicles getting traction.
Posted by: Arnold | Feb 1, 2008 6:44:06 PM
Just a bit of information on high power brushless PM motors. I contacted UQM and got a quote of around $20k, $30k, and $35k quantity 1 of their 75kw, 100kw and 150kw motors.
www.uqm.com/products/specsheet.html
Buses can use large motors that cost less, but cars can not. I just thought that this was a good point of reference. I would like to make a hybrid, but not at these prices.
Posted by: sjc | Feb 2, 2008 11:20:16 AM
I thing also that 6.5L engine is a over kill.
We probably have to look beyond hybrid and internal combustion engine.
I will seriously look on the old idea of external combustion engine, mainly steam engine with all of the new improvement that are used in current power plants.
The example could be that Cyclone steam engine.
Very interesting approach.
From this what I see it could be perfect engine for bus or truck (specially the Mark V and VI).
With the efficiency of 36% that go to the wheels as compare of 12% in conventional ICE (even series hybrid can't get more then 20% of absolute power to the wheels). External combustion engine have emission significantly lower then any ICE can deliver (no mater what fuel they using). With the enormous torque at starting point (700 ft/lbs or even 2310ft/lbs) you can't get wrong (no transmission necessary). One of the best thing in the steam engine is no idle cycle when the vehicle stop - perfect for city driving.
I think some body should seriously look on such possibility for city buses.
Look on there link below what is possible to do with that old idea of steamers. Just amaizing.
http://cyclonepower.com/cyclone_engine_uses.html
Posted by: mkimagin | Feb 2, 2008 1:15:34 PM
You might consider the Tesla steam turbine. This video shows one powered by a pressure cooker.
Lab tests have shown it to be 38% efficient with air power to electricity.
It might make a good series hybrid.
Posted by: sjc | Feb 2, 2008 2:52:04 PM
Tesla turbine like most of the turbines have very high rotational speed, and very narrow speed range where they are very efficient. It might be good for gen set. If I remember correctly some British company planning to use gen set with micro combustion turbine in some sport car, claiming 250mpg.
There is another solution for internal combustion engine to get maximum efficiency - that some type of CVT. They become more and more common even for buses.
80 year ego some Romanian inventor George Constantinesco come up with inertia transmission.
He drive 10 people in modified car that have only 10HP engine.
This man came with "people car" that did make 100mpg in 1920s . Should the X-price be awarded to him?
If that approach could be use (probably with some reliability improvement) in todays buses and cars we could see some significant improvement in fuel economy.
See the link with this patents - pretty interesting to read :
http://www.rexresearch.com/constran/1constran.htm
Posted by: mkimagin | Feb 3, 2008 8:47:55 PM
I think a Tesla could make a good stream series hybrid. They do not scale up well for a large bus, but 100 hp ones are pretty common and like you say, if you run them in that "sweet spot" they can be efficient. The alternator/controller/charger can keep the turbine in that range. The batteries act as a current buffer so the turbine/alternator can run efficiently most of the time.
Posted by: sjc | Feb 3, 2008 9:26:03 PM
Very informative article. This helps people a lot.
Posted by: Power Control Systems | Jul 3, 2008 9:50:37 PM
