Part of that brain push up is doing the math.


It won't be a dreamer, it will be somebody who does a heck of a lot of work developing it.

An invention is 1% inspiration and 99% perspiration.

Mike C.

If you climb a 10 degree slope, for moving forward 100 ft along the slope, you rise 17.4 ft upward, or 17.4% slope. Simple trig. Sine of 10 degrees is 0.174. That is where that came from in the article.

In the case of a DA40 climbing at 1120 feet per minute going Vy at 66 knots (6,684 feet per minute), the actual climb angle is 9.65 degrees, not far from the example.


Nope.

2645 lbs MGTOW going up a 9.65 degree slope requires 16.76% the weight of the airplane in more thrust. That is 443 lbs.

That 443 lbs thrust is acting through a distance of 6,684 feet every minute. Power is force times distance. That is 2,961,012 feet lbs per minute. 1 horsepower is 33,000 feet lbs per minute, so divide 2,961,012 by 33,000 and we get the answer in HP and it is...

89.7 HP.

This is actually far easier to compute than the incline method by simply taking the weight of the airplane, 2645 lbs, times the climb rate, 1120 FPM, which comes out to 2,962,400 feet lbs per minute, basically the same save for some small rounding errors. This is 89.8 HP. The fact you slide the weight up an incline doesn't change the basic lifting of weight up a height.

So if we are using 90 HP to climb the gradient, and we have a 180 HP engine, then it takes 90 HP to overcome the drag. Thus, to within some tolerance, it takes 90 HP of engine JUST to fly level and overcome the drag at the minimum drag airspeed, which is basically Vy.

Now this ignores prop efficiency. If we include prop efficiency, say 90%, then it really takes 99.7 HP for the climb part (we have to net 89.7 HP to climb the gradient after prop losses) and 80.3 HP for the drag part. So a little less power to fly level when we consider the prop but it doesn't change the overall point.

Mike C.

There's this giant myth that turbines has such great power-to-weight ratio. True, but only compared to dinosaur pistons. Their PTW is laughable compared to electric motors. I can today, off the shelf, buy a brushless DC motor that delivers 10hp/kg. No jet engine, not even with an afterburner, comes near that.

Therefore it's easy to deduct that the electric motor is not the problem, only the energy storage is. It's the ultimate prime mover, far superior to anything else. When energy storage gets solved (and it will, eventually), it will be all over for all fossil fuel engines in a flash. Obsolete overnight.

Don't buy stocks in big oil. Their days are numbered.

Energy storage is part of the propulsion system so it cannot be ignored.

It doesn't take much energy need before a turbine engine plus fuel is lighter than an electric motor plus batteries.

My plane, for example, has 3.7 MWH of shaft output, weighing a total of 3,400 pounds engine + fuel + misc.

For an equivalent electric system, it would take a battery pack of 4.0 MWH (assuming 93% efficiency motors). That would take 44,000 lbs of batteries and another 1000 pounds of motor and controllers.

Thus the turboprop engine is 13 times lighter in this application than current electric technology.


This is sort of saying don't buy Boeing stock, when anti gravity is invented, they are doomed.

In other words, it sure doesn't feel like a leap in battery technology is going to happen any time soon, certainly not at a scale of 10 times better. We don't need a few percentage points, we need big chucks.

While planes may be a factor of 10 away, cars are about a factor of 2 or 3, so expect widespread adoption of EVs well before any significant adoption in aviation.

Mike C.

Mike C.

Thanks for the math reminder, it has been twenty plus years since I had to deal with trig.
Still, just eye balling it, something seems off. :shrug;

Tim

This all comes back to what is REAL power, horsepower, in terms of electricity.

The batteries are the primary issue, but the difference between being close; in terms of legitimate useable storage now & what is REALLY needed to drive an airplane, is gigantic. We're not close, at all, even though (& GOOD on them) the scientists etc have made great strides forward.

To drive my Bonanza forward at approximately 180 MPH, it takes 11-12 gallons of gas per hour, or about 150 BHP. Gotta remember; that gas is ALSO making electricity for all the instruments & driving an AP; lights, the works.

At 150 HP, the conversion to electric KW is 111.85 KW per hour.

To understand how much that is, it takes about 25-30 KWH per DAY to run my 3200 SF house. The batteries needed for me to run my home are rated at 1105 AH, (or about 53 KWH) I can take about 80% out of them before they're dead, w/o recharging. That battery weighs just over 5,000 pounds.

Granted, battery technology has come a long ways in terms of storage, weight, the whole enchilada, but the math, is still the math. You want 100 HP in an engine, (what it honestly takes to run/fly a 2 seat anything) than it's going to use at least 80 KW per hour, to fly for 2 hours will use 160 KW. That number needs to be no more than 80% of the battery's rated capacity; so you need a battery that's at least 200 AH. Mike's Nissan Leaf battery is 660 pounds, but only makes 24 KWH of power. At that rate, to fly 2 hours on a Nissan Leaf type battery, you'd need (3) of them @ 1800 pounds or so to fly. One hour.

Gas, Fellas, is amazing for it's energy storage. Even though we all want to believe (and we do hope, myself included) that electricity could overcome gasoline, the truth is that as a medium, there isn't anything that comes close to it as a fuel. Solar/electricity is only just now becoming somewhat viable as a fuel, but it's going to be a long time before the panel/battery combination will be able to surpass gasoline's ability to make brake horsepower.

Sure Adam its easy, you just need a longer extension cord.

https://ec.europa.eu/jrc/sites/default/ ... miller.pdf

Pretty nice summary of the state of batteries just over a year ago.
The initial aircraft will be largely demo planes. The first real electric planes will be along the lines of the http://www.pipistrel-usa.com/ I linked earlier. Fly much slower, very low drag, light planes which require much smaller engines. Think back to the planes a hundred years ago, fly at 30 MPH and use 45 HP max.

As a stepping stone, I expect some hybrid planes. Use a generator and some batteries, idea of the batteries is to handle climb and/or take off power and the generator has just slightly more power then needed for normal cruise; allowing the batteries to recharge in flight. By tuning the engine for a single speed you can get more efficiency out it, but I expect this to be a market dead end.

Tim

In my past experience that's where the magic happens. Inspiration improves perspiration efforts by a factor 4.

A dreamer can take many forms. A hard working dreamer is a formidable force.

Back to electric airplanes..........I think that we'll figure out the battery to where the airplane can be used for training for 2-3 hours and be fast charged or battery swapped back at the home field.

No it does not. Your plane has about 700hp/engine, that's about 500Kw/per side. So maybe a 1MW in total. 750Kw of those get wasted as heat and noise, so you're only utilizing 250Kw of the potential power of your gas, they rest you just throw overboard. A 250Kw battery is a different kettle of fish. An improvement by a factor of 4-6, would already put it on par with gas. That's an energy density of about 2000Kw/kg. A pipe dream? Maybe. Or Maybe here in the next 5 years.

Listen, I'm not saying energy storage is there today or even close to where it needs to be, today. The operative word being today. But anyone who thinks that the future of mass transportation is not electric, is delusional. And it'll be so quick it'll spin the Fox News channel crowd's heads. I doubt you'll see any pure gas powered cars in 15 years time. Aviation, 40 years, tops. The old boy oil network is not going to be a business of growth.

My statement was on the total ENERGY, not the POWER, my plane would need a 4.0 MWH (mega watt hour) pack. That is, making 1 MW (mega watt) for 4 hours, roughly equivalent to my turbine engines using 366 gallons of jet fuel.


No, the engine rating is the SHAFT horsepower. That is the ACTUAL power coming out of the shaft, AFTER the losses. In my case, my effective SHP (which includes a bit of the jet thrust) is 715 HP each side, which is 1.07 MW for both engines. This is the OUTPUT that an electric system has to REPLACE. Assuming a 93% efficient electric motor, that means I have to draw 1.15 MW from the pack. Over 4 hours, that exceeds 4 MWH.

My engines ESFC (measured in actual service) is 0.47 lbs fuel per HP per hour. This is 29% efficiency. That is, my engines extract 29% of the available total energy in the fuel. 71% of the available fuel energy is lost overboard as heat. 29% is actually quite a high number for a combustion engine.


Wrong sized kettle. A 250 KWH pack would operate my plane for 15 minutes instead of 4 hours. Off by a factor of 16.


I consider this delusional.

Sanity check: Nissan Leaf has been in production 5 years already! Progress is not as fast as you think it is. There just isn't that much unexplored chemical territory for major battery breakthroughs any more. People have been looking for a LONG time!

Mike C.

This is not my field of expertise, but reading articles like the following it seems that there is a lot of progress right on the horizon. Your comments seem to indicate this is a mature science with nothing significant remaining, so what are your thoughts on this:

http://phys.org/news/2014-01-ultra-high ... ulfur.html

There is a lot of hype on the horizon about battery storage capacity, and a tremendous amount of misunderstanding based on how much actual energy comes out of gallon of gasoline; versus any battery combination, purely from a physics standpoint.

Obviously, Adam, you're sure that electricity will run everything in the near future, and by your (derogatory) statements about Fox News & the oil companies, that's a real good thing for you. Myself, I don't really care about the oil companies or Fox news, but I DO care about this little thing called "reality" and Mike has been correct from the beginning on his assertions of shaft HP, and his math. He's spot on.

Being that I do know what I'm talking about when it comes to the WORK that electricity provides, the ideal that we'll be able to effectively make planes fly on electricity for any real & useable time in the near future is just a pipe dream.

If it wasn't a pipe dream, IF the batteries were "SO" improved, than why aren't almost all the cars switching over to them right now? Seriously; when it comes to cars right now; (at a time when (supposed "green energy") is getting SO MUCH money for research) they STILL can't really make a car electric, past being a puddle jumper (Prius, Leaf etc) so again; where are they at?

Now, you can go ahead & tell me about Tesla, and no question they make a fine automobile, BUT they don't make a car that the average person can AFFORD. If they could, it'd be getting manufactured next year, for the masses, and it won't happen.

Now; if we can't make an incredible car battery, one that will run a 4WD truck of full sized car for a few hundred miles, up & down mountains, in heat & cold, what in the world would make you think we can make a battery anytime soon that will be light enough to make it into an airplane & be in any way efficient; or even legitimately useable?

There are multiple reasons that electricity is NOT the ideal fuel for transportation.

The primary reason that people like the IDEA of electricity driven cars so much is because they think it is "cleaner for the environment" because they've been conditioned & programmed to see all fossil fuels as bad.

The simple FACT is that electricity isn't free, it costs money to make it, to maintain it, across the board. The only electricity that comes from "natural" sources is hydro, and we pay the price of a decimated salmon population for that source of power. Past that, there's nuclear, coal & natural gas powered turbines. Nuclear is dangerous, no question, coal IS clean now; (bit that doesn't matter as it's been whitewashed as a "dirty fuel" so we can't use it) and natural gas is...a fossil fuel. That makes electricity. By burning it. And polluting the atmosphere with it.

Now, look at reality when it comes TO using electricity as a fuel in the average car.
As long as you're a city dweller, and your trips are short, you do the domesticated short commute every day; than fine, you can charge your car at night, and all is well.
But what about rural people who need to drive a couple hundred miles a day? Or; what happens if you want to drive across the country?
IF you have a larger battery, it will take IMMENSE amounts of power to charge that battery. Power is power, KW is KW, so no matter how efficient you make the motor or battery, you still have to replace the power it uses. That means an immense increase in stress on the existing grid; the average house probably will need to upgrade their power coming into the house; and the time it will take to shift say a thousand KWH form the grid into your car battery won't be short; it'll be long.

Couple that with the idea that everybody plugs their car in at the same time, at night, and now we face another problem....see, in the warm areas of the country, your AC will be shut off or running low at night so there's some extra power. BUT for those of us in colder climates, night time is when electric usage skyrockets, because that's when it gets cold outside, and more electric heaters are used.

Then...couple THAT with the idea that this new improved all efficient battery, it has to hold it's charge & accept charge & maintain charge in colder weather, too....
Not gonna happen. ALL batteries by their nature have extreme problems with cold temps. Batteries on the space shuttle have to be kept heated in order to maintain a semi decent level of charging capacity.

I love how they're working on this stuff, and some of it is amazing, but I truly believe that we're a LONG ways from having electricity being in any way able to replicate the ENERGY we get from a simple gallon of gas anytime soon, no matter how unpopular that opinion is.

More precisely, anything truly new and radically better will take decades to make work reliably and be commercially viable. Existing concepts will get incremental improvements but nothing that would be called a leap.


Lithium Sulfur dates back to 1960s. Yeah, it's 50 years old. No one has yet made a commercially viable LiS battery. A lot of the research is promising as to capacity, but there are significant technical and manufacturing issues to overcome.

This article is very positive on LiS:

http://www.hybridcars.com/oxis-jump-sta ... batteries/

Here's the company mentioned, Oxis:

http://www.oxisenergy.com/technology/product/

They are only at 300 WH/kg, but only for the short cycle cell (300 cycles). That's not much better than the 250 WH/kg that Lithium Nickel can reach now. Not a great leap. We need 1000 WH/kg.

Jet fuel is 3500 WH/kg at the OUTPUT of my engines, all losses considered, at least a factor of 10 better than the best batteries today.

If batteries improve by a factor of 10, that will be revolutionary. LOTS of people have looked and LOTS are still looking. I don't expect it in my lifetime.

Mike C.

We are talking about the difference between faith based science and analytical science.