[Rahul Rao]

Originally Posted by ambivalent_98

However I think the torque on the motors and in turn the current from the batteries will be huge for crawling conditions and start stop so electrics working would be slightly impractical. However as I also earlier said I am no expert in the matter but just thinking logically.

There is no such issue, electric motors can provide a starting torque more than 50 times its continuous torque, that's why hoists elevators, railway locomotives etc are traction motor driven.
Note that a diesel electric locomotive with 6 nos 600 HP traction motors can start a 4500 Ton goods rake on a 1:150 gradient, and its prime mover providing power to the motors is barely at fast idle. This is managed by modulating start frequency of the Ac tration motor.
Buses are barely 16 tons, balancing power for 100 kph is barely 40 HP, yet electric buses and series Hybrid ones are provided with traction motors upto 200 Hp for quick acceleration. In parallel Hybrids, the electrics do the work of starting, and then provide power along with the engine, cruzing is done with the engine only, and if load is below minimum effecient load, the motors will work as generators, on gradients when more power is needed the motor and the engine work in tandem. While decelerating, and also while ideling the motors generate electricity which charges the battery.

Look up website of Railway traction motor makers, and gear box makers like Allison to understand the functioning.

Rahul

[volkman10]

Volvo delivers first hybrid buses in India, to ply on Navi Mumbai roads.

Volvo Buses India today delivered the first hybrid buses in India. Navi Mumbai became the first city in India to adopt hybrid buses. The announcement was made on the sidelines of the Make in India week in Mumbai. The Prime Minister of Sweden Stefan Lofven handed over a symbolic key of the bus to the Chief Minister of Maharashtra

The Volvo 8400 City buses, which are certified by the Automotive Research Association of India (ARAI), fall under the government’s Faster Adoption & manufacturing of Electric and Hybrid Vehicle (FAME) scheme and will thus receive around Rs 61 lakh as subsidy taking the total cost of the bus to Rs 2.3 crore. The hybrid buses are a variant of the existing 8400 series bus, 1500 units of which are currently plying in 34 cities across India.

The new Volvo 8400 Hybrid city bus has a parallel hybrid system, which comprises a 5-litre, 4-cylinder, in-line diesel engine and an electric motor, which generates 160 hp of power. The vehicle, which starts via diesel, is propelled on electric mode from till it gains momentum. It will run on electric mode until a speed of 20 kph, after which it switches to diesel mode. The phenomenon happens at every stop & start during the operation cycle, which results in significant fuel savings and reduction of emissions. The batteries get charged during operations by the re-generative brake system, thus making the buses ideal for city traffic. “The Lithium ion-powered battery charge has to be normalized or balanced for every ride. The energy from regenerative brake system is utilized again in the bus, similar to a dynamo, powering air-condition and the automatic doors of the bus

http://www.autocarpro.in/news-nation...ai-roads-10488

[ambivalent_98]

Originally Posted by Rahul Rao

There is no such issue, electric motors can provide a starting torque more than 50 times its continuous torque, that's why hoists elevators, railway locomotives etc are traction motor driven.
Note that a diesel electric locomotive with 6 nos 600 HP traction motors can start a 4500 Ton goods rake on a 1:150 gradient, and its prime mover providing power to the motors is barely at fast idle. This is managed by modulating start frequency of the Ac tration motor.
Buses are barely 16 tons, balancing power for 100 kph is barely 40 HP, yet electric buses and series Hybrid ones are provided with traction motors upto 200 Hp for quick acceleration. In parallel Hybrids, the electrics do the work of starting, and then provide power along with the engine, cruzing is done with the engine only, and if load is below minimum effecient load, the motors will work as generators, on gradients when more power is needed the motor and the engine work in tandem. While decelerating, and also while ideling the motors generate electricity which charges the battery.

Look up website of Railway traction motor makers, and gear box makers like Allison to understand the functioning.

Rahul

THanks for the very valuable info. Its very informative. However the examples you mentioned rail locos or lifts/elevators have an A/C 3 phase connection of some sort. As far as buses I think they will work on a battery which can produce the torque necessary but would drain out quickly as there is a limit on the number of batteries and their "ampere-hour" rating. So I am guessing in cruise mode the batteries would work A-OK but in intial torque or frequent start torque requirement it might not work out optimally.
However I would like add a disclaimer. I am not an electrical engineer and my logic might not be exactly right.

[Rahul Rao]

There is a engine along with the battery which is also generating electricity and charging the battery. In railways the older generation traction motors were Dc, while current ones are Ac with modulated frequency. Power electronics have advanced to a stage that small VFD inverters to convert the DC supply from battery in required frequency is just about briefcase size.

Rahul

[i74js]

This would be a boon to curb the vehicular emissions associated with city transportation system. I am sure that enough testing of parallel / synchronous operations of electrical and diesel motor has been carried out for stop-go traffic and overload conditions.

Also, Mumbai observes a warm & humid climate for almost 10 months of the year and performance limitations of such sophisticated machinery is required to be understood to ensure enough preventive maintenance is carried out for smooth operation of buses.

Good to see new age technologies finding its place in developing countries.

Cheers !

[bullrun87]

How big is the change in fuel economy between the normal diesel we see on our roads and this new hybrid?

[silversteed]

Originally Posted by bullrun87

How big is the change in fuel economy between the normal diesel we see on our roads and this new hybrid?

Volvo claims an FE improvement of about 35%, going by this article. The Volvo 8400LE diesel city buses return an FE of 2-3kmpl, and the stats given in the article says 25.7L/100km, which roughly translates to ~4kmpl

[AkMar]

BHPians,

I got a chance to travel in this bus yesterday. Here is a short review of it.

Looks:

The bus looks very similar to any other Volvo 8400. There are a very few changes. There is a dome like structure on the roof & slightly different looking roof equipment of AC. Due to extra equipment the last window on left hand side is shorter in length. On the sides it gets decals related to environment & hybrid system. Large sized text "Let your city breathe" is there on window glasses on both sides. Inside the bus, changes include a new instrument cluster & 2 less seats in the last row owing to additional equipment. It gets an extra "Hybrid" badge below 8400 badge on engine cover.

Hybrid system & Drivetrain

As we all know, this bus has a diesel-electric hybrid system to power it. It uses a 4 cylinder, 5 litre diesel engine in combination with an electric motor. This bus uses an i-Shift (AMT) transmission instead of conventional torque converter AT. I guess this is done in interest of Fuel efficiency. The AC in this bus is not coupled to diesel engine. It runs on electricity. The batteries which power electric motor are charged by regenerative braking or directly by engine.

The bus starts on electric power. It continues on pure electric power will about 15 km/h, after which diesel engine fires up. The engine has a distinct note from which you can clearly make out the reduced displacement. Due to presence of AMT, gearshifts are not as seamless as the normal 8400. The AMT mechanism is clearly audible through clanking noises while shifting gears. Though gearshifts are easily noticeable to the ears, they are smooth & jerk free. Gearshifts are clearly tuned for FE. The unit upshifts very early. It rarely allows the revs to climb too high. However, the AMT unit never hesitates to downshift whenever necessary. The route involved a few hill climbs, and the transmission's selection of gears was spot on every time. Good to see that Volvo's implementation didn't go the Cerita way of holding onto an upper gear for ever.

The bus starts off with a typical electric motor whine, which I love. There is a break in acceleration for a few moments when the diesel engine cranks up. After engine cranks, a combination of electric motor & diesel powers the bus. The engine always sounds relaxed. There is hardly any time when it feels strained. The bus reaches 60 km/h very comfortably. It is electronically locked at 60/65 kmph. If you expect the typical blazing performance of a Volvo, you will be disappointed. I would term the performance as adequate. There is nothing to complain about. A bus designed for reducing emissions & increasing FE cannot be expected to win drag races However it goes about its job quietly.

Though the engine remains off until 15 kmph after the bus starts, once cranked, it does not shut down when speed drops below 15. That happens only when the bus comes to a dead halt. I feel some more gains could have been achieved by designing the system to cut off the engine before coming to a dead halt. I can think of many instances in bumper to bumper traffic where the bus will cross 15 kmph for a short time and then continue rolling at lower speeds without coming to a halt. In such situations, the engine will continue running even at low speeds.

It feels eerily quiet inside the bus when engine is shut off! I found the creep function in this bus to be a lot better than diesel Volvos. It creeps forward slowly & smoothly unlike jerky starts of diesel siblings. This results in increased comfort for standees in slow moving traffic. The battery pack gets charged mainly by regenerative braking. On some occasions, the engine continued running even after bus came to a full stop. I guess that must be due to low battery charge levels. However these occasions were very few.

The hybrid bus gets an all new instrument cluster. A digital battery level indicator takes up prominent place at the center of the console. There is a system which advises driver on how to drive for best FE. However I was unable to go into the details of it. The system apparently transmits driving data to Volvo.

Other fuel saving measures:

Measures to reduce fuel consumption extend beyond the hybrid system in this bus. it has fully automatic AC which decides an optimum temperature based on outside weather. It cannot be manually over ridden. This prevents unnecessary fuel consumption by AC. It should be noted that even though AC is fully automated for FE, it kept the bus adequately cool. Diesel engine's gearshifts are optimised to deliver maximum FE. Even the glasses are designed to reduce load on the air conditioning system. The bus gets black tinted glasses. Whats more, it gets dual layer glasses to better insulate the interior from outside heat. Regular Volvos get a single layer of glass.

Closing thoughts:

It was a real pleasure travelling in this bus. Experiencing the various systems at work was refreshing. It was a good exercise to try and understand the working of the bus & predict what its next behavior would be!

This is a very good product IMHO. It has all one needs for city conditions. Performance is satisfactory for the conditions it is designed to operate. The only two factors I see going against this product are 1) Cost, 2) High levels of Sophistication. Maintenance will have to be perfect considering the number of systems working together.

I have a few pics of the bus but I was unable to upload them from mobile. Will post them from home. Till then, here is a video by a friend who travelled in the bus:

https://www.youtube.com/watch?v=GHxVnWBT3Mg

[AkMar]

Pics & videos of the bus follow.

https://www.youtube.com/watch?v=oLgHvkSgPiE

A short video from the journey. Note that the tacho reads 0 initially. Diesel engine is off at this time & bus is propelled purely by electric motor. Towards the end, diesel engine cranks & tacho needle rises.

Interiors. Note the different position of tubelight above rear door


Close look at dual layer glass


Glimpse of instrument cluster. Couldn't get a better pic


Decals on the side.


Rear view of the bus. Note the Hybrid badging


Along with a regular Volvo. Note the bulge on AC unit


Front view


Side profile


Rear 3/4th view

[AkMar]

I had another ride in the same bus today. There seemed to be an issue with its air conditioning. For almost half an hour, the compressor didn't switch on. Everyone in the bus was sweating. The driver and conductor were hapless as they have absolutely no control over air conditioning. Poor folks had to bear ire of the passengers. They invited the passengers to fiddle with AC panel and see for themselves that pressing any button has no effect whatsoever. Need to travel in the bus a few more times to conclude whether it was a one off case or a regular occurrence. Perhaps Volvo should keep the AC manually controlled. A few more points from the journey & a chat with driver:

• Bus is electronically restricted to 60 kmph
• Acceleration was very much acceptable as stated earlier
• Driver seemed proud of his machine. A passenger started bad mouthing the bus due to AC issue. He said that the speed is also poor & compared it to BEST's Ceritas. Driver passionately defended the bus saying that it is far better than Cerita and it has reached destination in same time as a regular Volvo
• The bus delivers an FE of 4-4.5 kmpl against 2-2.5 kmpl of regular Volvo
• Regenerative braking was quite effective. From Borivali statio to Dahisar toll plaza, battery level rose from 1/4th to 3/4th. Near Thane, it came from 1/4th to half way mark within a kilometer of start-stop traffic

[volkman10]

Volvo's hybrid buses likely in Bengaluru soon.

Swedish bus and truck maker, said it is planning to introduce hybrid buses in Bengaluru within the next six to ten months.

The company delivered its first set of four hybrid buses to Navi Mumbai Municipal Transport Corp earlier this year. Volvo says these produce 50% less carbon footprint because of smaller engine sizes.

the government of Karnataka is in talks with the company to place orders for more buses to replace the existing ageing fleets.

On an average, a hybrid bus costs about Rs 2.3 crore but the central government provides subsidy of Rs 60 lakh per vehicle to the bus owners. Still, the cost is almost double that of non-hybrid low-floor Volvo buses, which plies in various metros. The bus segment of Volvo India is expected to grow 9% in 2016, up by about a percent compared to last year.

Link