Hybrid dash8

[link821]

https://www.wingsmagazine.com/pratt-whi ... onstrator/#

[notwhoyouthinkIam]

I mean, I guess one hybrid engine is better than no hybrid engines.

[Dias]

Seems like a gimmick. If it really saves 30% fuel burn they would have done it 10 years ago.

[fish4life]

Reduces GHG’s by 30% unfortunately it also requires so much weight in batteries it can only only 59 % of the passenger

[Inverted2]

All diesel locomotives have been hybrids since they came out in the late 30’s.

Airplanes, I’m skeptical about, since the added weight due to the batteries and electric motors will decrease payload.

Weight in a train = good
Weight in an airplane = bad

It’s more of a placebo, like hybrid cars. Makes people feel good like they’re making a difference but in reality, not really.

[goldeneagle]

All diesel locomotives have been hybrids since they came out in the late 30’s.

Airplanes, I’m skeptical about, since the added weight due to the batteries and electric motors will decrease payload.

A diesel electric configuration found in locomotives doesn't include batteries. I've never driven a train, but in my younger years I did fly seasonally and spent one of those winters off driving a haul truck in a mine, also a diesel electric configuration. The diesel electric setup benefits greatly in the low speed high torque requirements area, common in big trucks crawling up a hill at 3mph loaded with 100 tons of rock. The diesel generator can operate at optimum speeds for efficiency with no regard to the actual speed of the vehicle. In the haul truck, when we applied the dynamic (electric) brake, the power generated was not stored in a battery, it was shunted to a very large resistor box beside the cab which dissipated the power as heat. Interesting side note, not all of that heat was wasted, we would often put a can of stew out on the resistor box a short while before lunch and have 'hot lunch' ready when it was time to stop and eat.

For a typical hybrid arrangement we see in cars today, the energy generated by braking goes into a battery to be used later driving the electric motor. I own a hybrid car, and it's fascinating to see that it gets better fuel mileage in city traffic than it does out on the hiway. That's the beauty of the energy recovery system in action. When you get out on the hiway and run at a constant speed, it's basically running as a 'gas electric', the battery doesn't really make a difference unless you spend a lot of time going down hills that require breaking to stay on speed.

Since an airplane basically runs at constant speed for long periods, the engines already run at what amounts to a steady state which can be tuned to an optimum rpm by simply manipulating the propeller. But there is another option to increase efficiency a lot, to see how that works you need to look at how the hybrid system works in an F1 car. They recover energy during breaking the same way our production hybrids do, but they also have another mechanism, the MGU-K. That part of the system recovers more energy by capturing the heat in the exhaust and converting it to electrical energy. A typical turbine engine will capture roughly 60% of the energy in the fuel as 'work' to drive shafts, the rest of the energy goes out the tailpipe in the form of heat. With the heat recovery system in place, you can generate electricity capturing a sizeable chunk of the energy currently wasted.

For an airplane, my expectation the development work would not be around large heavy batteries, but rather around a system similar to the F1 MGU-K which will capture heat energy from the exhaust and convert it to electrical power used to drive the electric drive motors. If that converts a propulsion system from 60% efficient to 78% (a 30% increase in efficiency) then it would indeed measure up to the hype.

[TheStig]

Here's a link to the 10 page analysis that the project is based on.

https://www.readkong.com/page/the-pragm ... al-7037661

The regional aircraft mission

A regional turboprop aircraft requires approximately 2MW to fly at cruise speed. The typical 200-250nautical mile mission lasts about one hour, including its climb, cruise, and descent, with an averageof 2,000 kW-hr of energy required to complete the mission. Adding the usual reserve, the aircraftneeds to carry about 3,500 kW-hr of energy per typical flight. Current engines convert about 30% ofthe fuel energy in useful work therefore the minimum fuel energy on board is around 12,000 kW-hr.To power this mission on stored electricity alone, assuming an electrical conversion factor of 85%and a cell packaging weight burden of 35%, a 200 Wh/kg based battery cell system would weigh inexcess of the aircraft’s maximum take off weight (MTOW).

Given the large energy needs of even short-haul missions, and near-term energy storage densities, afully electric solution to propel a regional turboprop-sized aircraft is out of reach for the short to mid-term future. However, a hybrid-electric solution may be viable, provided it can enable significant fuelsavings and justify its onboard presence without limiting overall aircraft capabilities. If a hybrid-electric engine converts 40% of the fuel energy into useful work (as opposed to 30%), it wouldenable 25% of the fuel energy to be replaced by electrical stored energy in the form of batteries.This stored electrical energy is used for only a short period of the mission time, like during take offand early climb. Additional benefit can also come from using renewable sources for the stored electrical energy.

Application example - regional turboprop

A regional turboprop requires high take off power to carry large payloads but flies relatively slowlyunder relatively low power. Project 804 leverages this large ratio between peak power and steady-state power to create significant total energy savings. The propulsion system uses a 50/50 powersplit, parallel-hybrid configuration between an engine and an electric motor that is shown in Figure 4below. The electrical assist is high-power and short-duration allowing the size and weight of theenergy storage device to be manageable within the aircraft maximum take off weight. Theconfiguration also allows the engine to be optimized for the cruise portion of the flight only. Fullsystem capability is within the 2MW power class for the 30-50 passenger regional turboprop market.

The hybrid-electric system increases the aircraft Operating Empty Weight (OEW), and the aircraft’sfuel capacity is reduced by about 50% to allow for the electrical equipment and energy storage. Theremaining fuel mass, combined with the more efficient hybrid-electric system gives the re-enginedaircraft a range of approximately 600 nm (as compared to the base 1000 nm range). Given that 99%of this airframe’s missions are shorter than 500 nm, and that the hybrid-electric system provides anaverage 30% increase in fuel economy over the missions mix, this is a tradeoff that makes bothtechnical and economic sense.

[digits_]

The hybrid-electric system increases the aircraft Operating Empty Weight (OEW), and the aircraft’sfuel capacity is reduced by about 50% to allow for the electrical equipment and energy storage. Theremaining fuel mass, combined with the more efficient hybrid-electric system gives the re-enginedaircraft a range of approximately 600 nm (as compared to the base 1000 nm range). Given that 99%of this airframe’s missions are shorter than 500 nm, and that the hybrid-electric system provides anaverage 30% increase in fuel economy over the missions mix, this is a tradeoff that makes bothtechnical and economic sense.

This is the part where I'm curious how the regulator is going to deal with it. Measuring battery capacity and mileage/energy remaining seems to be quite difficult tasks to accomplish reliably. Much harder than determining how much fuel you have left in your tanks.

The missions may be shorter than 500 NM, but you might need 1000 NM to cover your alternates and final reserves.

Your new plane has 60% of the range when using 50% of the fuel. Makes me wonder if the cost/fuel savings would be worth it. I like innovative technology, but this seems to be doomed economicaly speaking.

Without any changes, I could easily design an airplane that would have 50% of the range for 50% of the fuel in the current airplanes, and it would give you thousands of pounds extra payload!

[goldeneagle]

It’s more of a placebo, like hybrid cars. Makes people feel good like they’re making a difference but in reality, not really.

With airplanes, you choose the right machine for the mission, different configurations have different strengths. Just like you wouldn't choose a citation to be landing on gravel bars in the arctic, you probably wouldn't choose a twin otter to move executives from Vancouver to Calgary.

Cars are similar. If your primary mission is to go out and drive on the hiway, hybrid doesn't make much sense. But if your primary mission is to drive around the city all day long, the hybrid shines. Every time you step on the brake pedal to slow in traffic, instead of burning the excess energy off as heat in the brake pads, a big chunk of it gets stored in the battery to use later. Accelerating from the stop after a light changes to green, the gas engine is being asked to do that acceleration in a low rpm high torque mode where it is the most inefficient. The electric motor can provide the low speed high torque start just as efficiently as it can produce steady state power in cruise. There is a reason the vast majority of the taxi fleet today is comprised of the Prius, and that reason is operating cost. In day to day operations, the hybrid uses a lot less gasoline, goes farther between oil changes, and is overall just less expensive to operate. It's a bit more expensive to purchase up front, but if you do 100,000 km of city driving, it more than pays for itself over the term.

There are a lot of other little things that add up to a significant savings over time. When we got our first Prius it was disconcerting to pull up at a red light and the engine 'stalled'. It was even more confusing initially, light turns green and you step on the accelerator, the engine doesn't start, the car just carries on to the next light without even starting the engine.

A couple years ago we upgraded the Prius to a Prius Prime, the plug in hybrid variant. It's got a bigger battery and beefier electric motor so it can do extended hiway runs on just electric. When we take the dogs up to the top of Mt Washington to go for a walk around the boardwalk, the battery is essentially drained parking in the lot at the top. When we come down the hill, by the time we reach the hiway it's almost full again, and we can go 42km down the hiway without the gas engine starting (I've measured, more than once). For a typical city commuter that plugs it in overnight at home, with that car they can likely do the to/from work trip without ever starting the gas engine. The virtue signalling folks will go on about 'green' yadda yadda, but I dont really care about that. We bought the car for two reasons, the first is to save money in the long term. My energy cost when driving it on electric that costs 14 cents per KWh runs about 2.2 cents a kilometer. When it runs on gas that costs 1.50 a liter, our cost is 6.6 cents a kilometer. Even on the hiway when the gas engine is running most of the time, it's 20% more efficient than it's predecessor we owned.

Our secondary reason for purchasing this one was a little different, goes back to when the Albertan folks were making all the noise about 'turn off the gas taps'. We live a short distance out of town, and my wife was driving to/from work every day. With that car, she can go back and forth to work without the gas engine starting, so if the pumps ran dry, no big deal. Not such a big deal today now that she is retired, but it was our own little personal way of saying '@#$! you' to that financially mismanaged disaster called Alberta.

[fish4life]

Another problem with the battery issue is they probably have a very narrow band where it’s well suited since you are always carrying the weight around whether you need all your range or not. A typical jet A powered aircraft can trade off low fuel loads for short range efficiency and high payload when required or use full tanks for long range and less payload

[Inverted2]

All valid points. Wondering if the turbine engine will do a lot of start ups and shutdowns. That start stop crap at red lights is actually very bad for your car engine. Most of the wear on a turbine engine is during start up as anyone who is a pilots should know.

My brother used to have a crappy Ford Escape with a V6. His work vehicle was a similar Ford Escape Hybrid with a 4 cylinder. Guess what? They got almost identical city driving mileage.

I’m not knocking their attempt at this idea. It just seems the amount of money and effort that will go into this won’t really pay off. I’ve got thousands of hours in the Dash8 series and the little -100s sip fuel something like 8-900lb/hr with the power back.

Great airplanes. Maybe they plan on making a lighter partially composite version. I have no idea but it will be interesting to see.

[‘Bob’]

It’s more of a placebo, like hybrid cars. Makes people feel good like they’re making a difference but in reality, not really.

I’m sure that all of those cab companies who run nothing but hybrids are doing it for nothing but the feels.

[Inverted2]

It’s more of a placebo, like hybrid cars. Makes people feel good like they’re making a difference but in reality, not really.

I’m sure that all of those cab companies who run nothing but hybrids are doing it for nothing but the feels.

They drive almost exclusively in cities and one driver I talked to said they got a government tax break to equip their fleet. Good in the cities yes, but out on country roads the engine runs the whole time.

[fish4life]

It’s more of a placebo, like hybrid cars. Makes people feel good like they’re making a difference but in reality, not really.

I’m sure that all of those cab companies who run nothing but hybrids are doing it for nothing but the feels.

They drive almost exclusively in cities and one driver I talked to said they got a government tax break to equip their fleet. Good in the cities yes, but out on country roads the engine runs the whole time.

Actually a lot of hybrids can run fairly efficiently on the highway as well because most can take advantage of an Atkinson cycle engine which is more efficient but doesn’t have low end power where the electric makes up for it.

[imjustlurking]

I wouldnt go so far to include the entire United States as having embraced diesel-electric hybrids -- California, for example, mostly goes with CNG, LNG, and gasoline-electric hybrid buses.

CargoJet would probably still try to do it and then fire you if you call them out on it.

[oldncold]

my question is battery efficiency at. -30c in a hybrid application, doesn't that negate any real or perceived gains in aircraft use?