25 ‘Tata Starbus Hybrid Electric Bus’ Handed Over to MMRDA

[navnit013]

every argument here is giving me swings. From yes OK to no not good.

BUT when I looked up at the routes. This bus will operate to/from BKC. And destinations, borivli, mulund, khargar, Thane, sion. All destinations within 30 kms. So a round trip of about 60 kms max. More than the distance, its how the traffic is in some of these places. A lot of fuel can saved in these routes which the diesels would've wasted idling.

 

[carcommentor]

...... A lot of fuel can saved in these routes which the diesels would've wasted idling.

Question to ask : at what cost? Is the efficiency cost effective and significantly beneficial to the environment ? A simple auto-stop feature in conventional engine when idling for long (akin to 'mild hybrid') will give much more benefit at lower cost.
One more point to note: Shorter distance means no chance for long stretch of road for deacceleration , so even the regenerative braking will not work – more inefficiency!

 

[gearhead2]

Good analysis but let's analyze it step by step. Un-avoidable in both situations. However, in case of series hybrid,....... The biggest example of this is the diesel locomotive which for decades has been working on this principal (less the batteries). If there was a fuel saving in directly powering the wheels from engine, I think the locomotives would have had it. Also, the constant speed operation of engine means less wear and tear which is more predictable than the equivalent varying speed diesel engine.

Oh yes, they did - the Suri hydro mechanical transmission (basically a torque-convertor) did just that (https://en.wikipedia.org/wiki/Man_Mohan_Suri) and it was adapted for use in railway diesel locomotives for increasing their efficiency. Dr. Suri patented the invention and he went on to win many national awards.

The above analyses of different stages of conversion losses (engine > generator>charge controller/// motor input > torque output>wheel traction)) I feel ignores the fact that mechanical losses in a system - mostly frictional losses of one kind or another - are typically higher than electrical losses.

And torque convertor losses (the Suri transmission being an example) are invariably higher than mechanical g/box losses due to "slippage" (except in the "lock-up" mode) - the reason why FE figures are always poorer in auto-box equipped vehicles.

 

[navnit013]

If the EV only range is about 16kms, then in a typical running cycle of the bus, it would save them about 10 lakhs per year on fuel alone.

Also stop start system can only save you the idling loss, not while running. Also, I consider start-stop as a gimmick. Its like us switching the car off and on, thats it.

I am not saying this is the best move by the govt. I am saying, its a step in the right direction. Under FAME, there is further scope for full electric buses procurement. If public transport moves into electric/green technologies first, it will ease the pressure on single vehicle purchasers like us.

 

[bhvm]

As per the explanation A.G has given,
It appears that the puny battery is designated to be used as a large capacitor rather than outright EV battery. This small battery will absorb any charge generated from braking regeneration and also dump power for engine starting and initial torque.

The questions still remain-
1. Considering limited life of Battery technology to be about 1000 to 3000 cycles, And with over 100 start stops happening per journey per day, the life of battery will be laughable at best. A large battery (100KWH or more)can maintain depth of discharge to 50% or above to maximize life cycles. With this puny battery discharging to 80% or below on every run, life will fall off a cliff.

2. Was it worth wasting taxpayer money on such minuscule benefit in the long run? (we do not know the cost of battery and frequency of replacement). Certainly not.

 

[carcommentor]

If the EV only range is about 16kms, then in a typical running cycle of the bus, it would save them about 10 lakhs per year on fuel alone.

Even if we ignore the additional price of hybrid over and above a diesel bus of similar capacity, and just take the subsidy amount, the subsidy will be recouped only after 10 years (Rs.1Crore/10lakh).

Also stop start system can only save you the idling loss, not while running. Also, I consider start-stop as a gimmick. Its like us switching the car off and on, thats it.
I am not saying this is the best move by the govt. I am saying, its a step in the right direction. Under FAME, there is further scope for full electric buses procurement. If public transport moves into electric/green technologies first, it will ease the pressure on single vehicle purchasers like us.

Agree to the fact that mild hybrid (start / stop ) is a gimmick. However as it stands now, hybrids are a gimmick too. The fact is, diesel has an energy density of 45MJ/Kg whereas Li Ion battery at best has 0.87 MJ/Kg. So for a heavy vehicle category, diesel is 51.72 times better at managing weight . Similarly the Cost of 1kWh battery is around $140 whereas 1lt (Just $1) of diesel produces 10 kWh. Unless the energy density of battery is increased drastically or the cost of Li Ion comes down steeply, there is no way either pure electric or a series hybrid can match the cost and energy efficiency of a diesel - even after considering the drive train inefficiency.

 

[gearhead2]

Even if we ignore the additional price of hybrid over and above a diesel bus of similar capacity, and just take the subsidy amount, the subsidy will be recouped only after 10 years (Rs.1Crore/10lakh).
Agree to the fact that mild hybrid (start / stop ) is a gimmick. However as it stands now, hybrids are a gimmick too. The fact is, diesel has an energy density of 45MJ/Kg whereas Li Ion battery at best has 0.87 MJ/Kg. So for a heavy vehicle category, diesel is 51.72 times better at managing weight . Similarly the Cost of 1kWh battery is around $140 whereas 1lt (Just $1) of diesel produces 10 kWh. Unless the energy density of battery is increased drastically or the cost of Li Ion comes down steeply, there is no way either pure electric or a series hybrid can match the cost and energy efficiency of a diesel - even after considering the drive train inefficiency.

Which is why I find it baffling why other sustainable/alternate/renewable energy sources do not seem to catch the imagination of the powers that be - to the same extent as EV & hybrids seem to be doing at present. Why are the fuel cell patents being guarded so tightly? Why hydrogen extraction from bio-waste is suddenly off the radar? Why bio-rich economies (Brazil & other South American nations) seem to have lost interest after popularizing gasohol?
At the risk of going OT, even here in India bio-diesel was in the news a while back & then the govt. seems to have got cold feet - at the behest of the oil companies perhaps? In fact I had almost invested in a mini jatropha oil extraction plant, when better sense prevailed!

 

[A.G.]

Having worked on such systems and bound by NDA, my observation is that yes the Hybrids, especially series hybrids, have significant efficiency improvement as compared to their non-hybrid counterparts. Further, the engine in a series hybrid runs at constant speed (variation less than 10% of design speed) and when coupled with the alternator, it can be simply compared to a genset and nothing more. In parallel or series+parallel hybrid where the engine is also used to power the wheels, the speed variation of engine is similar to pure engine powered vehicle.

The alternator in case of a pure series hybrid is easy to design and better optimized in terms of size while offering efficiency which is 90% or more. AC-DC converter efficiency is 95% and with best technology, the system efficiency for prime mover (Motor + Control) averages above 75% in MIDC and can go upto a peak of 85%.

Battery life of 2000 cycles is when the depth of discharge is 90% or more. For a Hybrid system to work effectively, the SOC of around 70% on the higher side is maintained to allow for energy recovery during regeneration and 30% on the lower side to increase battery life by preventing deep discharge. Beyond this range of 30% to 70% SOC of battery, the behaviour of power and regeneration is different in the interest of battery life.

 

[navnit013]

Regarding bio diesel. Its a double edged sword. Once there is a high commercial value for the crop, farmers will find it attractive and shift from their traditional crops. Which will eventually lead to food scarcity and ecological issue as well. I think brazil had a huge issue regarding the same. India dodged the bullet in this case.

The battery technology will improve. Lots of new tech coming up. The space to watchout for is capacitor based energy storage systems. Capacitors if successful has the potential to leave Li-ion battery for dead.

 

[carcommentor]

Which is why I find it baffling why other sustainable/alternate/renewable energy sources do not seem to catch the imagination of the powers that be - to the same extent as EV & hybrids seem to be doing at present. Why are the fuel cell patents being guarded so tightly? Why hydrogen extraction from bio-waste is suddenly off the radar? Why bio-rich economies (Brazil & other South American nations) seem to have lost interest after popularizing gasohol?
At the risk of going OT, even here in India bio-diesel was in the news a while back & then the govt. seems to have got cold feet - at the behest of the oil companies perhaps? In fact I had almost invested in a mini jatropha oil extraction plant, when better sense prevailed!

The success of alternate fuels boils down to how efficient and how easy it is to produce, transport and consume. No fuel has been able to beat crude oil based fuels till now. The alternate energy needs economics of scale to match crude oil based fuel ,for which demand has to be high. EVs managed to do just that. The popularity of EV is only because of Tesla’s huge success. If Tesla had failed to capture the imagination of people, EVs would have been relegated to niche markets. Despite making no profits, Tesla’s billion dollar valuations and pretty much unlimited preorders is what has kept the interest in EVs high.
As for biofuel, the biofuel source has shifted from arable crops to lignocellulosic biomass (plant, agriculture refuse and woody crops). The processing of fuel from these materials is not only less economical but is also energy intensive. For eg they use gasification, pyrolysis ( decomposition in high temperature in absence of oxygen) which are not only inefficient but are also energy intensive. Despite that, the niche market for biofuels is projected to be 1 lakh Crore in 2019.
The Gobar Dhan scheme of Govt might spark interest in methane fuels.
Coming on to fuel cells, the most popular fuel cell is the PEM based cell which works on Hydrogen. Although the electrolysis of water to get hydrogen is fairly efficient (60%), the subsequent processes of compressing hydrogen gas to liquid, transporting it in high resistive wall cylinders and using it in engines with thick resistive walls to avoid leakage and the danger of explosions has reduced the initial popularity of fuel cells.

 

[carcommentor]

........
The alternator in case of a pure series hybrid is easy to design and better optimized in terms of size while offering efficiency which is 90% or more. AC-DC converter efficiency is 95% and with best technology, the system efficiency for prime mover (Motor + Control) averages above 75% in MIDC and can go upto a peak of 85%.

You have to add the Diesel engine to the mix. Even if we generously attribute efficiency of 40% to ICE, the total efficiency of the system (taking the efficiency figures mentioned by you) is 40%*90%*95%*75% = 25% only. This is almost equal to at wheel efficiency of pure diesel drive train.

Battery life of 2000 cycles is when the depth of discharge is 90% or more. For a Hybrid system to work effectively, the SOC of around 70% on the higher side is maintained to allow for energy recovery during regeneration and 30% on the lower side to increase battery life by preventing deep discharge. Beyond this range of 30% to 70% SOC of battery, the behaviour of power and regeneration is different in the interest of battery life.

As I mentioned in earlier comment, the SoC limit reduces the usable battery capacity, thus a 30 to 70 SoC range reduces usable capacity to just 40% (70-30), so a 9 kWh battery acts like just a 3.6 kWh Battery.

 

[A.G.]

^^ Hybrids are any day more efficient than equivalent counterparts - case in point is Camry Hybrid (Parallel Series Combo) which is more fuel efficient than a Camry Petrol only version or a GM Volt (Series Hybrid) is better than an equivalent Petrol vehicle.

 

[carcommentor]

^^ Hybrids are any day more efficient than equivalent counterparts - case in point is Camry Hybrid (Parallel Series Combo) which is more fuel efficient than a Camry Petrol only version or a GM Volt (Series Hybrid) is better than an equivalent Petrol vehicle.

First off, the discussion is about significant difference in efficiency and if it is worth the subsidy. Second, AFAIK Camry Hybrid 2018 mileage is 46 MPG = 16.28 kmpl. The non- hybrid Camry gave around 19.16 kmpl. Where is the efficiency?
Coming to Volt, the first generation Volt series hybrid was phased out precisely because it was not significantly efficient than the conventional ICE. The present Volt is a plugged in hybrid. It has a externally chargeable battery and a fuel tank. The battery has to be charged externally. Once the battery nears depletion, the ICE engine (generator) takes over. So it runs on external stored electricity + gasoline. It's fuel efficiency is 42MPG (about 17.86 km/l ) on a UN/ECE Elementary Urban Cycle , which has less acceleration variations than typical Indian driving cycle. Where do you find significant efficiency difference in this?

 

[A.G.]

First off, the discussion is about significant difference in efficiency and if it is worth the subsidy.

Thanks for pointing out as I had the impression that the discussion was whether Hybrids posed any benefit at all or not. Subsidy unfortunately has never been a function of efficiency - that's why SHVS got the subsidy for benefits which were nothing more than a mere eyewash.

 

[gearhead2]

Forgive me for being cynical, but I find the thread degenerating into a brownie-point scoring exercise. A situation pregnant with technological breakthrough possibilities on the one hand and environmental catastrophe on the other, seems to have meandered into same-old, same-old territory.

A fate that seems almost tailor-made for the "pre-ordained" school of thought about our planet's future! One sees small breakthrough steps in fits & starts, but on the larger canvas entropy seems to be having the last word, with the system paradigm gradually unraveling down a one-way street.

Perhaps (as I said before) it is only the cynicism of senior citizenship - though I fervently hope it is not.