Has Rising Fuel Costs Paved The Way For Electric Buses?

[Joseph C.]

I was thinking about the cost of bus transportation and did the arithmetic on the numbers in light of the continued rise of petrol and diesel.

• I estimate that just one bus from a company like Citylink travelling roughly 500 kilometres a day would burn €180,000 worth of diesel a year at today's market value (37 litres per 100km). Granted they get wholesale prices but the discount probably wouldn't be that great. Plus I anticipate that wholesale prices will match the current market value quite quickly as the price continues to rise.
  
  The same mileage would cost €12,600 at ten cent per kilowatt if the bus was electric - assuming that there is a lower commercial electricity rate. If not it would be roughly twice that at the domestic non-night saver tariff.
  
  I'd imagine that such a bus would need one megawatt of battery for a 1,000 kilometre range. Thunder Sky quotes 70kw per 100 kilometres for their 40-something-seater electric bus. A 350/400 kilowatt motor would be required - reliability being the operative word.
  
  Basically, if they could produce a kilowatt of lithium NMC for €500 this should be enough to make it practical. €800,000 per bus with modifications and additional spares for refitting.
  
  It could be modified further with highly insulated walls, roof and windows to reduce energy consumption (up to 30 kilowatts/hour I believe) on heating/cooling. The roof could also be lined with solar panels to power the heating/cooling (damn the proper name for this eludes me).
  
  The estimated 6,000kg of battery should be easy enough to carry. 500 hundred litre tanks of diesel would be 500kg. I'm not sure about the engine perhaps it would save another 900kg (12 litre). That's just 4.6 tonnes of additional weight.
  
  If the battery could last ten years (it should as it is only being discharged half-way) than it would be a prudent investment. Over such a time period a normal diesel bus would burn €1.8 million worth of fuel. That leaves a saving of over €800,000 per bus. This also doesn't include the maintenance costs associated with the upkeep of ICEs. For a company with an electric fleet the savings are enormous. If NMC batteries could last longer than ten years the savings will be even greater.

The problems that I would foresee is that bus companies such as Citylink change their buses every five years. To be the most cost efficient you would have to over-engineer the bus so that it would last a long time and refit it as the need arises. The second problem is of course the cost of infrastructure. The company would have to have a base capable of recharging a fleet of buses relatively quickly.

Anyway something to ponder for a more efficient, less-polluted future.

I am going to write a piece on this and the transition to electric transport but I would appreciate if any holes can be picked out.

 

[dogman dan]

Your math looks good only if the battery is free. You have to look at cost per mile, and how many additional busses you need since half the time many of them will be charging.

 

[Joseph C.]

Your math looks good only if the battery is free. You have to look at cost per mile, and how many additional busses you need since half the time many of them will be charging.

My figures are very conservative and error on the side of caution. For instance, they don't take into account the cost of an ICE bus (€260,000) to give additional leeway.

I was thinking of an actual specific intercity company in Ireland to make it easier to work the numbers.
There are no 24 hour intercity bus services in Ireland. The pack would only be discharged to half-way on any given day before arriving in the bus depot.

Therefore, the question becomes charging points. This particular company would only need about ten points at a depot if they could charge the buses at one C. It would take 30 minutes to fully charge a pack. That would be less if there was a charging point at one of the bus terminals - induction charging would be very convenient.

The charging infrastructure would get more expensive if you were talking about a large national fleet of buses or a city fleet like Dublin. However, then it becomes a question of numbers. Well engineered charging stations should also last a lot longer than the lifespan of the buses.

There is also the additional fact that city buses wouldn't clock up half the mileage of an inter-city bus. It would take at the very worst just half the time to charge the battery pack as it would an Inter-City pack. So a 15 minute maximum charging turnaround time at one C. Of course the fuel savings of city bus would undoubtedly be at best half those of an inter-city service. €400,000 as opposed to €800,000.

 

[fechter]

We've had them for years in San Francisco.
But they cheat and use overhead lines to power them. No batteries. It's like a gigantic slot car. It makes some impressively large sparks when they connect to the lines. Overhead lines run at 600VDC. The power comes mainly from hydroelectric sources.

 

[dogman dan]

I'm not entirely knocking the idea. It's just that when you consider the fuel cost of an EV, you need to also include at least some portion of the battery cost. On the flip side, industrial size electric motors can have a lifespan calulated in decades. If I'm not mistaken, the San Francisco cable cars have the cable pulled by the original electric motors, which of course have had bearings and what not replaced. So perhaps you'd only replace the wheels and the seats on buses in the future.

It would be fantastic if things like buses that ran all day were primarily powered with clean solar energy which is gathered daytime. I've seen some interesting ideas, wireles charging ports under the bus stop to help extend range, and similar ideas with an overhead contact at the bus stop giving the bus a quick zap.

But cheaper, not just yet, unless you add in the real cost of oil. That would be calculated in the cost of air craft carriers, armored batalions, cruise missles, attack drones, human bodies killed and maimed etc. You pay for cheap oil in blood in some cases.

 

[deardancer3]

buses in some cities run on Compressed natural gas, CNG, which has not seen the run up in fuel price like diesel.

d

 

[Kingfish]

Diesel-Electric busses are common in the Seattle Metro: They can operate with or without overhead power.

• Tolley Bus System Evaluation
• New clean, green hybrid buses hit the streets today

~KF

 

[Joseph C.]

I'm not entirely knocking the idea. It's just that when you consider the fuel cost of an EV, you need to also include at least some portion of the battery cost. On the flip side, industrial size electric motors can have a lifespan calulated in decades. If I'm not mistaken, the San Francisco cable cars have the cable pulled by the original electric motors, which of course have had bearings and what not replaced. So perhaps you'd only replace the wheels and the seats on buses in the future.

It would be fantastic if things like buses that ran all day were primarily powered with clean solar energy which is gathered daytime. I've seen some interesting ideas, wireles charging ports under the bus stop to help extend range, and similar ideas with an overhead contact at the bus stop giving the bus a quick zap.

But cheaper, not just yet, unless you add in the real cost of oil. That would be calculated in the cost of air craft carriers, armored batalions, cruise missles, attack drones, human bodies killed and maimed etc. You pay for cheap oil in blood in some cases.

The electric bus trams are convenient for large cities. They are not a viable solution for the majority of transport.

I have included the cost of the battery. Half a million euro. I'd maintain that if you were ordering 20 to 30 megawatts of battery you should be able to get it for at least that price.

Worst case scenario it still works out €800,000 cheaper than the price of diesel over ten years. In reality that figure would be closer to €1,000,000 as you would include the cost of a new ICE bus (€260,000).

One million worth of savings per bus. It starts to really add up when you have a fleet of buses.

This may not work so well in the U.S. where you have subsidised fuel but it is very different here.

 

[Hillhater]

.....if they could charge the buses at one C. It would take 30 minutes to fully charge a pack. That would be less if there was a charging point at one of the bus terminals - induction charging would be very convenient.

...I'd imagine that such a bus would need one megawatt of battery

I believe you suggested only using 500kwhrs before recharging ...?
So to recharge 500kWhrs in 30mins on (say) a 500volt system would need a 2000A charger system ..for each bus !

 

[Joseph C.]

.....if they could charge the buses at one C. It would take 30 minutes to fully charge a pack. That would be less if there was a charging point at one of the bus terminals - induction charging would be very convenient.

...I'd imagine that such a bus would need one megawatt of battery

I believe you suggested only using 500kwhrs before recharging ...?
So to recharge 500kWhrs in 30mins on (say) a 500volt system would need a 2000A charger system ..for each bus !

Yep. A monster one megawatt charging station - no half measures. And about ten of those for a large depot. An induction type charge could fill up ten battery packs in five hours plus the time for one bus to move on and move off the charger.

The above is the cost I don't know. Safety could be a bigger stumbling block than the cost though. I just don't know.

 

[Hillhater]

does such a thing as a 1MW charger exist ?...
..and yea, 2000a at 500v seems a tad bit dangerous !

 

[Joseph C.]

does such a thing as a 1MW charger exist ?...
..and yea, 2000a at 500v seems a tad bit dangerous !

I don't know but it needs to be invented.

 

[gogo]

I rode on a demonstrator electric bus at an EV Expo in Phoenix more than 20 years ago. It was very pleasant but had a very limited range. It was explained that advancements in battery technology would soon make the range and economics acceptable. Molten salt batteries seem like they'd be suited to use in busses.
http://en.wikipedia.org/wiki/Molten_salt_battery

The transit department I drive for has some hybrid busses that use regenerative braking to charge Maxwell ultracapacitors which are then used to charge the batteries, thereby taking a load off the normal generator. I haven't heard any claims of improved fuel economy. Cough*subsidy*cough.

The thing that really sucks is that the Germans who make this system haven't figured out how to integrate the regen with the regular engine-retard for smooth braking. The damn things brake like bucking broncos! The Germans have been back a few times to try to implement improved control software and they are improving the braking smoothness, but it still sucks compared to the non-hybrids.

Here is the PDF describing the system. The motor is shown grafted onto the left of the transmission.
View attachment crappy_hybrid.pdf
Here the motor is shown on the right:

 

[Joseph C.]

90 watt-hours per kilogram means a one megawatt battery pack would be twice the weight of the NMC.

If you were to go that route lithium-titanate would be a better solution with a much longer cycle life.

 

[liveforphysics]

500v and 2000amps is cake. The datacenter switchgear I used to work with was 8000amps at 480vac 3p. You only need 2 contactors that are a quarter the size. There are connectors and contactors and power supplies that can do 2kA no problem.

Though, for most flexible cables and ease if mating and unmating, I would suggest a staggered mate connector with compact off-the-shelf 500amp rated pin/socket connectors sized for 500MCM noodle conductor. Then a guy just has to plug in 4 of the cables that are each easily managable to move and mate, then flip the switch to close the contactor and start the charging.

If you have all night though, it seems to me a 200kw charge setup would be enough.

 

[gogo]

90 watt-hours per kilogram means a one megawatt battery pack would be twice the weight of the NMC.

If you were to go that route lithium-titanate would be a better solution with a much longer cycle life.

Some places on the internet claim 120Wh/kg.
http://en.wikipedia.org/wiki/Electric_vehicle_battery#Zebra
And there is clearly a battery conspiracy going on here, anyway. :wink:
Is this a Battery Conspiracy?

Weight doesn't seem to be much of a concern with the busses I drive. They are always 7/8 full of fuel or more.

Diesel busses are loud and vibraty. Just the improvement in the passenger experience would have to be worth a lot.

 

[liveforphysics]

Each one of these 12 cables fitted to this breaker is 500MCM (equal to about 12 pieces of 4awg cable that you may be used to seeing all in parallel). There are 12 of these cables per bus on the back of this contactor.

It's capable of roughly 4,500amps continuously, and this is just generic off-the-shelf stuff in a medium sized data-center.

The charging infrastructure is really a non-issue. It just seems big to folks used to residential tiny stuff. It's nothing compared to data-centers that pull 30MW continuously, and have single PDU fail-safe static-switch devices moving 2MW through them 24-7, and they are only about the size of a couple refrigerators back to back.

 

[Dauntless]

The Solar Taxi, which went around the world in 80 days and then kept going, had some seriously hot molten salt batteries. Did you check the temperatures in the Wikipedia link? If they cool off, the electricity is going and it can take weeks to get them useable again.

(Oh and, I'm wondering if Mr. Physics considered that they might need to be charging DOZENS of those buses in one location, even if it is overnight that's almost the need for it's own power generation right there. What is one bus compared to one data center?)

There are other molten salt efforts. Ceramatec is supposed to have some that work at 90 degrees. They are emphasizing the use in storage, there's no such thing as batteries for our main grid, but there are communities that aren't on the main grid using molten salt from Zebra and others as the backup for when the local plant goes down. Ceramatec (30 years experience with sodium beta-alumina, etc.) is offering a 20kw battery, (10 watts for a dollar) compared to the 16kw in the Chevy Volt. But the suggestion is that it's not suitable for electric vehicles, at least not the current evolution. The Solar Taxi wasn't exactly off the shelf technology for the mechanically/electrically ignorant. The focus is instead on people like my Mother, who is outside the city and off grid, running her place on solar and propane generators. (Texas; those batteries won't do much cooling off.) Her lead acid cells for the various buildings are a nightmare. (Why did they build that wall around the cells that I have to lift those huge things over?) The solar trailer for remote power gets whatever is useable out of the old batteies cycled out of one of the solar sheds, nothing but problems. Molten salt is predicted to work for at least 10 years,3,600 cycles. (Ah, blessed relief.) I'll probably have to bust those walls down to get the unit in. (Are you getting the idea that WON'T break my heart?) Oh, let's not forget they could store a lot of electricity at the bus yard for charging overnight if they used the molten salt, perhaps cutting in half the overnight current demand. Disappointed as I am that they don't suit my needs, I have to say it's a tantalizing technology. Maybe someday it'll be ready for cars. . . .

But my real interest is in convenient power for vehicles, molten salt so far hasn't seemed like the answer. The search goes on.

 

[Joseph C.]

(Oh and, I'm wondering if Mr. Physics considered that they might need to be charging DOZENS of those buses in one location, even if it is overnight that's almost the need for it's own power generation right there. What is one bus compared to one data center?)

He said that a data centre would draw 30 MW continuously. That would be enough to charge over 400 buses in eight hours using 30 one megawatt chargers. If it was used continuously it would charge over 1,200 buses every 24 hours from 50 per cent discharges.

In reality, it would probably be much higher as probably the majority of the buses wouldn't be discharged anywhere near half with one megawatt battery packs.

 

[liveforphysics]

Getting a 10-20MW service installed is as simple as telling them where you want the switchgear doghouse to recieve the medium voltage feeder (25-75kv), and where you want the pad mount transformers to sit. You would likely want about 5 pickup truck sized stepdown transformers if you wanted 10x 1MW charge stations.

This sort of feed and equipment is just off-the-shelf stuff that you simply bid out for install prices and write a check to the lowest bidder to do it. Takes a couple weeks, most of that is waiting on the transformers to be delivered.

Things dont get special in industrial power until you exceed about 100MW. Then it becomes a special concern. 10MW stuff is just off-the-shelf typical data center or industrial process gear.

 

[Joseph C.]

Getting a 10-20MW service installed is as simple as telling them where you want the switchgear doghouse to recieve the medium voltage feeder (25-75kv), and where you want the pad mount transformers to sit. You would likely want about 5 pickup truck sized stepdown transformers if you wanted 10x 1MW charge stations.

This sort of feed and equipment is just off-the-shelf stuff that you simply bid out for install prices and write a check to the lowest bidder to do it. Takes a couple weeks, most of that is waiting on the transformers to be delivered.

Things dont get special in industrial power until you exceed about 100MW. Then it becomes a special concern. 10MW stuff is just off-the-shelf typical data center or industrial process gear.

This is excellent information, Luke.

You wouldn't happen to have an approximate cost for this? Are we talking 200,000 or more for the infrastructure and installation for ten megawatts of charging facilities? I don't need specific numbers but somewhere close to 100k would be ideal.

 

[deronmoped]

They should run them off of natural gas.

I just read a article (Yahoo Finance News) that they are burning off hundreds of millions of dollars of natural gas every year at these new oil fields here in the USA. All someone has to do is capture it and put it in the bus. Here in San Diego they run a fleet of NG powered buses. The bottom has fallen out of the price of natural gas. It's now becoming a problem trying to get rid of it. Burning it off will lead to trouble for these companies in the near future.

 

[Dauntless]

The run buses and shuttles on NG, LPG, etc.

As for the flaring (Sigh) yeah, the shift in the gas market has set the new oil finds that don't already capture it burnin'. You see, they can't sell it for enough to cover the cost of capturing it. Befire the economic collapse with the gas pumps going at over $5/gallon, the natural gas prices were soaring and they were hard at work digging new wells. They didn't even have to go LOOK, they just went back to known gas fields that were once thought undrillable. Then with the price fell for lack of demand, these wells were hard pressed to recoup the investment. New natural gas finds that are NOT shale see burnoff, as sand, etc. is not a popular place for gas to come from if you own a refinery. (Don't as me to explain that one.) There's all this talk about how we should be selling more natural gas overseas, but nothing comes of that. But they want the ethane and other things they find where there's NG, so what to do with it as it comes out?

So if you're thinking 'Great, with demand down they'll stop FRACKING.' Well, the only fields I understand to be fracked are the shale fields, which is where they want the natural gas to be from. Meanwhile this other unwanted gas burnoff pollutes the air, warms the globe, all while accomplishing NOTHING. . . .

 

[Mike B]

PROTERRA anyone?

http://www.proterra.com/index.php

 

[gogo]

Heh, the bus barn for my city is heated by the university's cooling tower water because its right next to the university power plant! How easy would it be to run those power lines?!