Nikola Motor Company reveals its class 8 tractor design (EV/serial hybrid)
 

http://ecomodder.com/forum/attachmen...1&d=1465329863

There was some discussion in the past of some of this technology being used in a heavy haul application. They claim they have a prototype undergoing testing and expect to see production within three years.

Startup company targeting owner-operators with electric Class 8 truck | Overdrive - Owner Operators Trucking Magazine

https://nikolamotor.com/one

Makes me want to become a truck driver.

https://nikolamotor.com/assets/nikol...b8120e4ab2.jpg

Their claim of 1,200 mile range with a 320kWh battery puts the energy consumption at ~267Wh/mile - which is better than many EV cars. That is a little hard to believe.

Edit: it is a hybrid, and it has a turbine generator. So, it uses an unknown amount of fuel to go the 1,200 miles.

https://nikolamotor.com/assets/nikol...1ec3967d4a.jpg

Diesel-electrics have been doing quite well in long distance heavy haul applications for some time now.

http://pop.h-cdn.co/assets/cm/15/05/...n-470-0210.jpg

150 gallon fuel tank for CNG

This is being discussed on Sheppard's AeroTruck thread.
 

The technical issues of a gas turbine charging a battery pack is questionable from an efficiency standpoint. It does allow a small and light weight power pack to charge a very large battery pack. But, does a gas turbine which has near double the fuel consumption on a mass/power/time scale of a modern diesel engine have the ability to haul 80K pounds of freight the stated 1200 miles without plug in charging? I really don't think so. Some simple math doesn't think so.

One interesting claim from the Nikola website is their procurement of natural gas wells to provide 1 million miles of free fuel to the first 5000 buyers. This would certainly offset their premium cost over current top Class 8 tractors.

I feel Sheppard's approach is far more practical now and in the near future. If you take the AeroTruck and use a smaller 11-12 L diesel engine with a reasonable electric boosting drive, you get the best of both worlds in that you can cruise on diesel engine power alone in flats and low loads and still have excess stored power to drive uphills with the ability to regain some of that energy on the downhills. Such a truck could happen NOW.

I'd sign up to try one. If anyone here can get press loaners, I have the CDL!

A gas turbine can be more efficient then a diesel when used as a powered for a generator. That is how I read this. The electic motors at the wheels are powered by a battery. The CNG turbine just trys to keep the battery charged. In 1200 miles both the batteries and the CNG is empty and it needs charged and refuled. The driver would be at his limit anyway before that point. Many heavy trucks are used less then 500 miles and may be able to go pure electic.
As pointed out, this is how a locomotive works but also how a submarine is powered.

The Rankine cycle turbine can be more efficient than a diesel piston engine but emissions standards for NOx and manufacturing costs have been barriers in the past. The concept has merit even if CNG is not yet available at every truck stop. We have a local station for CNG in Sayre, PA and fleets in the region have their own fueling facilities. GE has put out bids for injectors to use CNG for their locomotive engines. Starting and braking are the high torque operations that benefit from electric motors. Hybrid pick up trucks may be in the offing too. Farmers and construction fleet operators are very cost conscious.

http://www.overdriveonline.com/files...5-10-13-03.jpg




https://borgdotcom.files.wordpress.c...ett-design.jpg

Simple cycle gas turbines do not have the efficiency needed.
 

Modern gas turbines are rated just above 39% thermal efficiency. Many class 8 diesels are at 48% thermal efficiency and some cutting edge applications are knocking on 52%. The only way a gas turbine exceeds this efficiency is via co-generation with a steam cycle using some of the high value exhaust heat from the gas turbine. I doubt they are using a steam cycle as a co-generator in the Nikola Truck.

However, the fuel is supposedly free for a period of time after purchase, so the efficiency is really a moot point when viewed by Nikola Motor Company.

Gas turbines may have a lower weight and fewer moving parts than a reciprocating engine with the same power output, but their maintenance is more specialized and the time between overhaul is shorter, not to mention their air intake filters have a shorter life.

I'll take always being used at peak load over a higher theoretical thermal efficiency any day- an idling engine is inefficient no matter what graph you can point to. That'll help with overhaul interval as well.

Right, the gas turbine is always at max efficiency, the diesel sometimes. Plus you are comparing old gas turbines to the most modern diesels. There are modern turbines that do as well or better then the most modern diesels and they are getting better all of the time as they are more widely used in ships.

If diesels are more efficient than gas turbines, then why are there many gas turbine-powered generating plants, while diesels are only a niche application, mostly for backup & emergency power? And why are there so few diesel-engined airplanes?

The Nikola One design has 6 motors - and no need for a multigear transmission. Electric motors have almost flat torque output at all RPM's.

Another route would be to do something like this, instead of the turbine:

http://www.rtcc.org/files/2012/07/si...head-truck.jpg

Since the trucks have batteries, they can still pass:

http://assets.inhabitat.com/wp-conte...ehighway-1.jpg

Gas turbine power is relatively cheap and the turbines can be run at their max efficiency. Gas can be main lined into a facility much easier than diesel. Diesels are favored for backup generation because of their much quicker startup time vs a turbine generator. Diesel, as I understand, is also not favored in airplanes because of weight.

Really?
 

Please show me the "modern turbine" that can improve on current thermal efficiencies of diesels. I have already defined this as the simple cycle gas turbine and not the combined cycle turbines you are thinking of. The Nikola truck does not seem to have a steam turbine hanging off the back of the gas turbine exhaust. The steam turbine would be exceedingly large and it's start up would be excessively long.

Turbines are ideal where power to weight is at a premium. Modern turbines have the ability to run at higher temperatures and compressor pressures but are still limited to around 40% TE. Yes, you can hang pre-compressors and thermal recuperators and such but now your small compact turbine is big and clunky for just a few percent gain. Capstone only claims about 35% TE for it's simple cycle micro turbine. Such a turbine would be ideal for a class 8 tractor with hybrid electric drive but not because it is more fuel efficient than current diesels but because it's small size and weight allows you to transfer more payload to your battery and fuel.

The advantage of gas turbines in aircraft is self explanatory. Nothing beats the power to weight advantage. But, small aircraft engines that are diesel are making a comeback for their fuel efficiencies and reasonable costs.

And you are making the assumption that diesels lose great efficiency when at part "throttle". They do not. They do not have throttles and can be optimized for part load efficiencies. The BFSC map of a diesel is far larger than that of a gas turbine or a spark ignition reciprocating engine.

Yes, I am familiar with super-critical CO2 turbines but these are more suited to larger power generators found on ships or land. An experimental system leverages the high quality heat of turbines (little heat is lost to cooling and friction) by running a gas turbine exhaust into a steam turbine whose exhaust powers a super-critical turbine. The thermal efficiencies are pushing 70%. Exciting stuff but not applicable to a class 8 tractor drive.

How about US Army plans to replace Abrams power pack (originally gas turbine) with diesels? I assume that originally gas turbine was chosen because of its multi-fuel capacity and high power to mass ratio, but certainly not fuel effectiveness.

https://en.wikipedia.org/wiki/M1_Abrams#Tactical

The 30-40% turbines are the old design that date back to when diesel motors achieved similar numbers or worse. So diesels have evolved and improved and you yourself have pointed out so have the turbines even though much less attention is spent on them. So even the old simple turbine design is not bad thermal efficiency especially comparing it to a truck diesel operated at all kinds of rpms and loads. Now start using this concept's power plant in millions of trucks for 25 years and watch how much better turbine designs get.

Not to me :-) And I still remember the (possibly apocryphal) story about the WWII-era engine designers searching for the optimum turbocharger size for piston engines - which turned out to be eliminating the piston part entirely.

But AFAIK those engines are all intended as replacements for gasoline engines, not turbines.

The Piper M350 and M500 are the same airplane on the outside.

The M350 has a 350 hp turbocharged six cylinder gasoline engine. It holds 120 gallons of fuel, has a maximum cruise speed of 245 MPH, and a maximum range of 1544 miles.

The M500 has a 500 hp PT6 turbine engine. It holds 170 gallons of fuel, has a maximum cruise speed of 299 MPH, and a maximum range of 1150 miles.

Those high efficiency gas turbine power plants have huge heat recovery systems that could not possibly fit into an airplane.

So a 500 hp engine uses more fuel then a 350hp engine. I don't think people 20 years ago thought you would be holding a battery powered supercomputer in you hand either, and it makes sense Orville and Wilbur's design might be more refined then Adolf's, especially when the technology is used widespread from lawn movers to supertankers. I still say give turbines a little more chance before writing them off.

Right. And it comes as a surprise that cruising at 299 mph burns more fuel than cruising at 245 mph?

As for heat recovery systems, a truck can carry quite a bit more weight than an airplane.

What leads to a relatively high efficiency of turbine engines in aircraft is either the cruising altitude or the bypass ratio. For higher altitude a turbojet (or pure-jet as it's still often known) makes sense because the air is thinner, so there wouldn't be so much advantage with a high bypass ratio and the fuel consumption would be more related to the lower drag with the air and the lower oxygen concentration limiting the amount of fuel that could be burnt at those conditions, while for intermediate and lower altitudes a turbofan is more advantageous due to the bypass ratio. Turbine engines in general, even turboprops to some extent, are also more prone to damage from foreign object ingestion than piston engines, no wonder some operators still rely on piston-powered aircraft for harsh environmental conditions such as faced by agricultural aviation.

I am afraid it is not entirely correct. 299mph is max cruising speed. If you need max range, you fly at economy speed and it is determined by mass, shape and propeller, so it should be pretty similar for both planes (EDIT: I must admit, I cannot prove it - I cannot find the corrrect data).
Lets do simple math:
1544 miles div 120 gals is 12.86 mpg
1150 miles div 170 gals is 6.76 mpg
500 vs 350 hp means 42% more power
6.76 vs 12.86 mpg means 52 % more consumption
Here you go. In similar aplications, turbine loses roughly ten percent in efficiency.

Pardon me for assuming.
 

Let's use WWII as the starting point.

The Junkers Jumo Aircraft engines were technically advanced even for current times in that they were 2 stroke, opposed piston engines with excellent scavenging and produced about 750 hp for just under 1700 pounds of weight. The license was sold to Napier who produced an after war engine that had a Delta configuration and became better known as the Deltic. Though it was not used in aircraft it was widely used in motor patrol boats and other utility marine craft as well as the Deltic line of rail cars and some municipal emergency vehicles. It produced around 2500 hp with a weight approaching 6000 pounds though it is unclear to me if that includes accessories. The engine was not a light weight by any means.

The famous Wright R-3350 which powered the B29 and other craft of the era eventually saw a development cycle that had multi turbos geared to the shaft to capture lost exhaust energy and add efficiency and power. It could produce over 2500 hp and weighed in at just under 2700 pounds.

Pratt & Whitney's line of PT turbo shaft engines which is now represented by the PW 127 and is widely used in commuter aircraft such as the Bombadier Dash 8 and the Fokker 50/60. It produces about 2500 shaft hp at just above 900 pounds!

The simplicity and weight advantage of the gas turbine is ideal for aircraft. The increase in fuel consumption is more than compensated for by the massive increase in lifting power and the ability to fly higher and faster than piston propeller aircraft.

Yes, there are continuing advancements in turbine technology but they are focused on the issues of reliability and costs as development is up against the limits of the laws of physics and material science. Compressor ratio and heat differential dictate your power production and efficiency much like in a piston engine. Compressor ratios are already up from the 3-5 of the WWII jets to 30 in engines found in the likes of the F15 and up above 40 for the high bypass turbines found on commercial transports. One just keeps stacking more vane/stator stages. But flight parameters also effect your engine design because effective compressor ratio increases with aircraft velocity.

None of this is germane to the discussion at hand except for the fact that turbine engines do not like to run at much less than full rated power without a severe drop off in thermal efficiency. The TE plateau starts to really drop off at 70% of max power and by the time you are idling at 30% max, your TE is halved. Aircraft designers will specify an engine so that it operates on this plateau with the knowledge they can call on a massive amount of take off power for at least a few seconds or minutes before all the inconel turbine blades melt.

The micro turbine to power a Class 8 tractor would be woefully inefficient as a direct drive. Using it as a hybrid charger in the Nikola truck makes sense even if it may be only at 35% TE as it will run for only a period of time to charge the batteries. It looks like Nikola has dealt with the fuel cost aspect by providing the "free fuel".

Let me address this question.
 

The idea of the micro turbine engine is to provide high power in a very small size and weight. To gain a few more percentage points of thermal efficiency would require not just an increase in mass but an increase in volume. Intake air can be pre-heated and compressed using the exhaust stream of the turbine, but at the gas flow volumes needed to be effective, the size of your power pack increases tremendously.

A 500 hp micro turbine with intake heater and pre-compressor would be larger and weigh almost as much as a 500 hp diesel engine. At that point, why go with the turbine? Though of course you would have to add back the weight and volume of a diesel's cooling and transmission needs.

500hp might be somewhat overkill anyway, as the ICE is going to be used only to drive a genset. But still, even though a turbine engine has a higher power-to-weight ratio and fewer moving parts, it still sounds too hard to justify their use in a road-going vehicle even if it's a serial hybrid. Even a Wankel engine could make more sense.

I always thought hybrid tech was perfect for heavy hauling. Reducing the need for a higher output engine just to accelerate or climb a grade should improve fuel economy and recapture on downgrades.

Why all the talk of a diesel engine operating under a wide load range? It would operate similarly to a turbine in that it would only run when needed to charge the battery, and during that time would operate at peak efficiency.

Another advantage of a hybrid design is to maintain cabin comfort without having to idle the engine.

The huge drawback to a hybrid design is that it weighs a lot more, and that cuts into the max payload the truck is allowed to haul. Since the primary purpose is to haul a load, this is not an insignificant drawback.

My question is, with all variables concerning payload and route being the same, what is the fuel cost per mile of a hybrid design compared to modern diesel-only tractors?

The turbine as pointed out is not connected to the drive wheels and only runs at peak efficiency as a powerhead for the generator. You are right a diesel could do the same job more efficiently today. This is 10 years out, so right about when the Elios are rolling off the line. At any point they could easily drop the turbine and go with a CNG piston powerhead on the generator. No doubt they want not just efficiency but the cleanest truck on the road and thanks to VW nobody is going to look at a diesel as clean ever again. Also the point here is this is an electric truck, if you say it goes 1200 miles on 150 gallons of diesel you are just another diesel truck on the road even if you aren't powering the wheels. That kind of diesel electric hybrid technology is already on the road. These guys are trying something new.

Don't get me wrong, I admire the work NMC is putting forth.
 

They are in reality producing a battery electric truck for OTR use. However, they must use an exceedingly large batter pack to have any useful range which is not enough for a 600 mile driving stint. So, they must use a genset to extend the range. But, the weight is the issue. They chose a micro turbine based solely on its high power to weight ratio. Lightening the structure is also in order so that they can still carry the industry standard freight load within the 80,000 lbs of road load limits. The thirstiness of the micro turbine is offset by using CNG as the base fuel and offering free fuel to offer the buyer payback times that are short. However, accepting a much shorter electric range of around 100 miles with rapid charging as mentioned by several posters would allow drayage and nodal carriers who have a predictable route to run almost purely on electricity via quick charge stops or overhead cable connects.

This would not help the Independent Operator who goes where his load takes him. Sheppards' Starship would be a much more saleable item to that market niche. Free fuel doesn't help the Independent when that fuel is nowhere near the pickup or drop off point. The Nikola truck would really be better targeted at the corporate firms that run large node freight centers as the free fuel is easily stored and dispensed there.

An aside to this discussion has been the turbine technology available. In another thread, powder printing was discussed. Powder printing along with nano scale powders allows alloying of metals/materials that would not be possible in the standard melt pot. There is exciting research that will allow turbines more leeway to run at higher compressor ratios and combustor temperatures. This will add several percent to their thermal efficiency. Now all we will need is for Thermo Electric Materials to find a breakthrough that will allow electric power generation from the high value turbine exhaust heat without adding much to weight and bulk.

Though hybrid tech is usually pointed out to fare better in heavy urban traffic than in highway, it makes sense to explore its regenerative braking as an alternative to traditional mechanical engine-braking setups.


I'd rather get a Diesel instead. Could even try some radial engine, much like a downsized version of the Guiberson engine used in Stuart tanks.


All-electric air conditioners are already available and can be adapted into non-hybrid trucks too.


Why not give BAS-Hybrid setups a chance? Even though they may not offer full-hybrid capabilities, their mileage improvement comes at a lower weight penalty.

What a radial diesel might look like:

https://upload.wikimedia.org/wikiped...sel-Radial.jpg
https://en.wikipedia.org/wiki/Guiberson_A-1020

What if empty batteries?
 

Imagine the truck is reaching max range, meaning battery banks are empty and also CNG supply. You can fill CNG tank, but still, battery banks are empty. No idling means you drive and use the turbine to propel the truck.

Then, what remains in the game?
500 hp gas turbine * 80% efficiency in conversion to electricity * 90% efficiency in conversion from electricity to motion in your six electric motors. So without battery assist Nikola One has cca 360 hp on wheels.

In hills, Nikola One will crawl 20 MPH with other dirty old-skool trucks and pray for downhill ride to charge battery banks.

How much hp is really needed to move class 8 rig on flat terrain?


side note - 320 kWh battery seems theoretically to be good for max 2880 m climb (at least potential energy of 40 tons 18 wheeler equals 320 kWh in 2880 meters of height).
I have no idea how long could the truck drive on batteries, but electric ships in my country have 336 kWh batteries and range around 80 km (source here). Can anyone estimate range of this rig on batteries?

It would be neat if the rigs could fast charge while parked in a loading bay, either being loaded or unloaded. I'm sure this would require a massively upgraded electric service at each location.

freebeard: Bolting a radial engine into a genset seems easier than doing it with a regular driveline due to clearance issues.

seifrob: Gotta agree with you, there is somewhat of an over-expectation in regard to the overall efficiency of this concept. OTOH a direct-driven electric driveline without differentials or a gearbox is often pointed as advantageous as it eliminates most of the friction losses.

redpoint5: As long as there would be no shock hazard for loading bay operators, makes sense.

I believe this like I believe the three wheeler out of New Orleans.

Turbine-electrics haven't had a good history - they're noisy and the turbine is only efficient under full load. GE tried them for locomotives and they were only effective in train with an auxiliary diesel-electric locomotive for non-full-load work (and travelling in populated areas)

It will be interesting to see if adding a battery pack solves the issue.

Given ICEs of any kind only work efficiently on full load I've been wondering if a HGV chassis would be large enough to allow multiple independent engines to be installed. (Similar to Toyota's free-piston 10kW generator concept)

For aircraft: Power to weight. A piston engine of the same output as a large turbine would be so heavy the aircraft won't fly (imagine a 747 with 10 piston engines, as one example, or look at the complexity of the engines that were used on the Bristol Brabazon).

For power stations: Exhaust temperature. Turbine exhaust is hot enough to drive steam plant (cogeneration) and the combined efficiency brings the relatively poor efficiency of the turbine past that of a similar diesel. Unlike other space-constrained applications it's perfectly feasible to run a 1+N solution so that turbines can be down for maintanance without affecting overall output.

(Open cycle turbine plants exist, they're expensive to run and generators tend to keep their older diesels maintained for this kind of peaking load as a result. These plants are getting more and more workouts due to renewables intermittency and this in turn is driving up power prices - it's one of the hidden costs of renewables that noone wants to talk about)

Diesel (or CNG) piston engines don't have hot enough exhaust temperatures to drive steam turbine generation efficiently, so you don't get DGCT plants.

For ships: Piston engines win on efficiency every the time. You usually only see turbines on military vessels where rapid response time and compact size are bigger advantages than fuel consumption. Theoretically on an electric-drive vessel one could run a CCGT generation plant but this doesn't happen

For rail locomotives: gas turbines were tried and failed. They were useful to haul loads up the west side of the Rocky Mountains but noise was a killer and heavy consumption meant the locos were deadweight when running down the plains of the midwest (diesels were used for the downhill runs). Hauling up the Midwest plains was viable but noise complaints were a major issue.

The american power grid systems (note plural) are not interconnected or robust enough to handle longhaul electric rail systems - which have a nasty tendency to go from drawing 4-5MW to generating 3-4MW as trains go over hills. That's bad enough that in some countries (New Zealand being one example), the power distribution companies PAY rail companies to not run electric locomotives. European rail systems are dense enough and interconnected enough that a train generating power in one segment can supply a train in another segment without stressing the intermediate power distribution systems (this is more or less the same issue that intermittent renewables plants cause on grids, only on a much faster timeframe)

For vehicles: Turbines have been proposed on a few high performance hybrids. These are NOT being pushed for fuel efficiency, but for power-to-weight and powerplant size reasons.

For the actual power requirements and fuel efficiency required on vehicles piston engines are the right choice if you need ICE. Truckmakers have decades of experience at "rightsizing" the engine to the load and whilst electric transmission is a good idea for boosting on hills or stop-start urban delivery work, a longhaul rig has more-or-less constant load which means that direct coupling an appropriately sized engine directly to the wheels is the most efficient overall design. It may be that a smaller donkey engine setup is the best way of boosting or providing electric drive for noise-sensitive end-point operation but (as with a hybrid setup and batteries) that extra mass cuts into carrying load plus overall efficiency and therefore it makes more sense to setup your distribution depots so that the longhaul work is point-to-point with (hybrid) delivery vehicles from there - funnily enough, that's exactly what tends to happen.

The thing about longhaul transport is that trucks have lifespans of several million miles and in many cases the engines are never allowed to cool down between servicing (not running == not earning). Providing "free fuel" for 150,000 miles isn't a big incentive over having an overall more-efficient solution - and that overall solution includes appropriate location of your endpoints.

Yes, the hybrid is cool - but unless it makes economic sense a haulier will never buy it. The technology is more likely to make economic sense in the 2-12 ton delivery vehicle market than in the 30-50 ton hauling one - and in such markets a turbine would be far too noisy to tolerate.