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Old 11-27-2017, 12:09 PM   #43
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Some info about battery expectations...http://www.bnn.ca/tesla-s-newest-pro...eries-1.924595
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Old 11-27-2017, 12:28 PM   #44
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I agree with the suggestion of having a diesel genny to top up the batteries. This could extend the range considerable as well. Diesel electrics are common place around us everyday. Almost all trains in use are electric drives with diesel generators to supply the electricity. Also large mining trucks and many ships are the same design. Apparently they cant make a transmission large enough to take the torque required to move such large equipment.
I'm going to need a longer shore power cord.....
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Old 11-28-2017, 11:26 PM   #45
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No idea on the Tesla Semi requirements but probably similar to what all the new ELectric busses use. Liquid cooled connections. 350 KW. Probably multiple feeds.
From a (partisan) analysis here, some numbers that don't add up. The article is wrong in attributing a lead-acid-type charging curve to Li batteries but that in no way invalidates the numbers.

A few quotes:

So we have a 76%, more or less, efficiency on the charge rate which means we must deliver almost exactly 2 Megawatts to the truck for that 30 minutes.

I note that 500 kilowatts has to be dissipated somewhere for that entire period in the truck or the batteries, controller equipment or both catch on fire. This is a serious problem all on its own that I am not convinced Musk can solve.

Then there is the economic issue. Musk claims he's going to "guarantee" a 7c/kwh price for all that power. How he thinks he can do this in a commercial environment where demand meters are used by law is beyond me; the first time a trucker needs to be charged at 4:00 PM on a 95 degree day there will be a very large surprise delivered in the form of the bill. Never mind that the trucker (or company) will be paying for the 25% losses too; you get to pay for the entire megawatt-hour even though you only keep 75% of it; the rest heats the air. Apparently Musk thinks that he can simply build "battery packs" to store energy and thus charge them when the power is cheaper. Ok, that's fine and well, except (1) now you have another 25% loss, stacked (you take one when you charge the pack when "cheaper" and then when the truck is charged) and for each truck's worth of capacity in said battery bank he gets to buy another battery that would otherwise go in the truck, plus another 25% to cover the losses when the truck is charged, plus the electronics to charge, discharge and control that "banked" pack. Somehow this all is going to "work out" to 7 cents/kwh.

---

The average house in the United States consumes about 12 megawatt/hours of energy over the entire year, or about a megawatt-hour per month. Musk intends to suck twice as much energy from the electrical grid as your house consumes in a month in 30 minutes.

To put some perspective on this that means that one such truck charging will place approximately the same load on the grid as 1,400 houses. One truck.

What happens when 20 of them show up at the truck stop? You know they do that today -- they fill their diesel tanks and they're on their way, although they typically only fill said tanks half as often as these batteries will require charging.

So it won't be 20 of them it will be 40 since their range-before-refueling is about half of common OTR trucks now. Now we're talking about the load of roughly 57,000 additional houses that will be instantly presented to the grid and which the grid must be able to support -- per truck stop or terminal!

---

All of the foregoing assumes you believe 800kw of battery is enough. I'm not so sure. The math doesn't pencil today on that and I don't see how Tesla can overcome the deficit under any plausible scenario. Today's diesel truck gets ~8.5mpg, roughly, fully loaded @ 80,000lbs gross (maximum 50-state legal limit.) Diesel contains ~136,000 btu/gal, so if we take 500 miles (maximum range of said EV truck) we would need ~60 gallons of fuel containing ~8.2 million BTUs if that was a conventional diesel-powered tractor. A modern diesel (with all of its computer controls and transmission) can achieve very close to 40% thermal efficiency in steady-state on-road operation (assuming ~5% gearbox and parasitic loss), which means 3.264 million BTUs have come out the business (driveshaft) end of the engine and transmission when it finishes burning that 60 gallons of fuel.

Musk's 800kw battery only has 2.7 million BTUs of energy in it. That's 18% short, roughly, but in fact it's worse than that because neither his motors or the PWM controllers for them are lossless, and remember, we've accounted for the diesel's engine and transmission/accessory inefficiency. If we assume Tesla's electric motors are 90% efficient (possible but unlikely; 85% is more-likely but I'll give him the other 5) and the controller is also 90% efficient (possible) the stacked loss there is 19% so now he only delivers 648kw over that same period of time to the driveshaft(s).

In other words he's not short 18% on energy content he's short a whopping 32%!
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Old 11-29-2017, 10:14 AM   #46
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From a (partisan) analysis here, some numbers that don't add up. The article is wrong in attributing a lead-acid-type charging curve to Li batteries but that in no way invalidates the numbers.

A few quotes:

So we have a 76%, more or less, efficiency on the charge rate which means we must deliver almost exactly 2 Megawatts to the truck for that 30 minutes.

I note that 500 kilowatts has to be dissipated somewhere for that entire period in the truck or the batteries, controller equipment or both catch on fire. This is a serious problem all on its own that I am not convinced Musk can solve.

Then there is the economic issue. Musk claims he's going to "guarantee" a 7c/kwh price for all that power. How he thinks he can do this in a commercial environment where demand meters are used by law is beyond me; the first time a trucker needs to be charged at 4:00 PM on a 95 degree day there will be a very large surprise delivered in the form of the bill. Never mind that the trucker (or company) will be paying for the 25% losses too; you get to pay for the entire megawatt-hour even though you only keep 75% of it; the rest heats the air. Apparently Musk thinks that he can simply build "battery packs" to store energy and thus charge them when the power is cheaper. Ok, that's fine and well, except (1) now you have another 25% loss, stacked (you take one when you charge the pack when "cheaper" and then when the truck is charged) and for each truck's worth of capacity in said battery bank he gets to buy another battery that would otherwise go in the truck, plus another 25% to cover the losses when the truck is charged, plus the electronics to charge, discharge and control that "banked" pack. Somehow this all is going to "work out" to 7 cents/kwh.

---

The average house in the United States consumes about 12 megawatt/hours of energy over the entire year, or about a megawatt-hour per month. Musk intends to suck twice as much energy from the electrical grid as your house consumes in a month in 30 minutes.

To put some perspective on this that means that one such truck charging will place approximately the same load on the grid as 1,400 houses. One truck.

What happens when 20 of them show up at the truck stop? You know they do that today -- they fill their diesel tanks and they're on their way, although they typically only fill said tanks half as often as these batteries will require charging.

So it won't be 20 of them it will be 40 since their range-before-refueling is about half of common OTR trucks now. Now we're talking about the load of roughly 57,000 additional houses that will be instantly presented to the grid and which the grid must be able to support -- per truck stop or terminal!

---

All of the foregoing assumes you believe 800kw of battery is enough. I'm not so sure. The math doesn't pencil today on that and I don't see how Tesla can overcome the deficit under any plausible scenario. Today's diesel truck gets ~8.5mpg, roughly, fully loaded @ 80,000lbs gross (maximum 50-state legal limit.) Diesel contains ~136,000 btu/gal, so if we take 500 miles (maximum range of said EV truck) we would need ~60 gallons of fuel containing ~8.2 million BTUs if that was a conventional diesel-powered tractor. A modern diesel (with all of its computer controls and transmission) can achieve very close to 40% thermal efficiency in steady-state on-road operation (assuming ~5% gearbox and parasitic loss), which means 3.264 million BTUs have come out the business (driveshaft) end of the engine and transmission when it finishes burning that 60 gallons of fuel.

Musk's 800kw battery only has 2.7 million BTUs of energy in it. That's 18% short, roughly, but in fact it's worse than that because neither his motors or the PWM controllers for them are lossless, and remember, we've accounted for the diesel's engine and transmission/accessory inefficiency. If we assume Tesla's electric motors are 90% efficient (possible but unlikely; 85% is more-likely but I'll give him the other 5) and the controller is also 90% efficient (possible) the stacked loss there is 19% so now he only delivers 648kw over that same period of time to the driveshaft(s).

In other words he's not short 18% on energy content he's short a whopping 32%!
Very good post! A real eye opener! At this time this country doesn't have the infrastructure to support a highway full of these vehicles. If OP is correct in his calculations the electrical grid required to support this seems overwhelming. Tesla may have designed the perfect semi, it's just to bad the country isn't ready to supply the needed power to support it now or in the very near future.
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Old 11-29-2017, 10:39 AM   #47
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Very good post! A real eye opener! At this time this country doesn't have the infrastructure to support a highway full of these vehicles. If OP is correct in his calculations the electrical grid required to support this seems overwhelming. Tesla may have designed the perfect semi, it's just to bad the country isn't ready to supply the needed power to support it now or in the very near future.


Tesla has said these “mega chargers” would be powered from solar panels, and would not take any energy from the grid.

People jump to conclusions too quickly...... these electric trucks will be a rarity at first....not much contention at charging locations to start. The infrastructure will build out to support the growth as time marches on.
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Old 11-29-2017, 10:42 AM   #48
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Where are you going to put enough solar panels to power a small town in anywhere but the most rural areas?
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Old 11-29-2017, 11:39 AM   #49
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Charging a single truck requires 2 megawatts for half an hour. Some research shows that it takes 4.8 acres of panels to supply 1 MW. So, you're looking at close to 10 acres for every charging station. I don't think that is ever going to happen.
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Old 11-29-2017, 11:47 AM   #50
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Newmar, please make a coach like this.

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Charging a single truck requires 2 megawatts for half an hour. Some research shows that it takes 4.8 acres of panels to supply 1 MW. So, you're looking at close to 10 acres for every charging station. I don't think that is ever going to happen.


No. You store the charge. The panels can take time to recover before the next truck comes along.

Same way that getting a big Mac in the drive thru lane can take 1 minute or 30 minutes depending upon the demand at the time.
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Old 11-29-2017, 12:32 PM   #51
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No. You store the charge. The panels can take time to recover before the next truck comes along.

Same way that getting a big Mac in the drive thru lane can take 1 minute or 30 minutes depending upon the demand at the time.
Currently the sun is up from 07:20 to 17:32 and it is heavily overcast (predicted for the next 3 days). We just had two days of dust.

The cooling houses are full of produce.
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Old 11-29-2017, 02:26 PM   #52
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Currently the sun is up from 07:20 to 17:32 and it is heavily overcast (predicted for the next 3 days). We just had two days of dust.

The cooling houses are full of produce.


I’m sure we will see trucks with large batteries - designed to give emergency charges to other electric trucks and cars that have run “out of gas” - lol

Not much different than AAA giving a jump start....

I have been to gas stations that have run out of fuel.....then you go to the next one.

Remember this is how all early technology goes through its refinement phases......
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Old 11-29-2017, 02:51 PM   #53
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I’m sure we will see trucks with large batteries - designed to give emergency charges to other electric trucks and cars that have run “out of gas” - lol

Not much different than AAA giving a jump start....

I have been to gas stations that have run out of fuel.....then you go to the next one.

Remember this is how all early technology goes through its refinement phases......
Those trucks already exist, but EV's not semis.
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Old 11-29-2017, 03:01 PM   #54
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So, a couple things. When we were on the windmill tour the guide addressed a couple questiions regarding the location of wind and solar. The solar field or windmill doesn't have to be where the power is needed.

A chinese factory located in San Diego faced a rather large power bill. They leased a chunk of land in the coachella valley, put up windmills and solar and connected it to the grid. They actually produce more than they need. Even after the power company charges them for "delivery" they are ahead. Their payout is 6 years, the system has a lifespan of 30 years, their ROI is expected to be north of 300 percent. The power goes in at palm springs and comes out at San Diego.

As far as the grid not being ready for all vehicles being EV, that is irrelevant...because not all vehicles are EV's. They have 20 to 30 years to adapt...and they will or individual users will simply generate their own power. The share holders of the power companies will not be happy.

I suspect many of the replies here are from Americans. Although many feel that their country is not capable of change or modernizing their facilities that is not the USA I know. (And I'm a foreigner). Give yourself a little credit. The rest of the world is figuring this out, you will too.
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Old 11-29-2017, 03:17 PM   #55
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I suspect many of the replies here are from Americans. Although many feel that their country is not capable of change or modernizing their facilities that is not the USA I know. (And I'm a foreigner). Give yourself a little credit. The rest of the world is figuring this out, you will too.
Thank you Radar!

When petroleum-powered vehicles first appeared there weren't filling stations dotted along the highways - there weren't any highways to dot! It took 20-30 years at the beginning of the 20th century to even start to build a network of filling stations with consistent quality fuels, highways for the cars and trucks to drive on, etc. And how about pipelines to carry crude to refineries and then to move the refined fuels? Trucks to carry the fuel the "last mile." There were huge expenditures of taxpayer dollars along with private capital. Many companies were started and then went bankrupt in the process.

The spread of efficient and flexible electrical grid technology, standardization of chargers, technology to efficiently store electricity for when and where it is needed, all these things are doable but will require the same things as our current petroleum ecosystem: taxpayer dollars, utility ratepayer dollars, and private capital. And lots and lots of entrepreneurial energy. And yes, there's still a lot of that left in the US, last I checked
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Old 11-29-2017, 07:14 PM   #56
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With the typical RV campground today browning out when folks try starting up their AC’s, imagine a few if these sucking in the amps to recharge those Lithium power packs. Nothing in the boonies will be able to handle that load.

Imagine the revenue to the parks. They will be able to sell fuel (power) as well as parking space.
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