Alternative Power Systems

Dave Hall · Post by **Dave Hall** » Tue Nov 30, 2010 12:00 pm

That's an excellent intro to electric aircraft - Ian gave it to the Bristol Strut a while ago.

If you visited the Flying Show last weekend, you may have seen that Roger Target had his electric air-racer project there on display.

Trevor Harvey · Post by **Trevor Harvey** » Tue Nov 30, 2010 3:43 pm

Presumably the batteries do not have to be square things like the one in my car? When can they become part of the airframe? Carbon/glass/foam sandwich construction seems common enough, why not incorporate the battery within the structure?

tnowak · Post by **tnowak** » Wed Dec 01, 2010 8:23 am

And when the batteries need replacing???
Tony Nowak

Trevor Harvey · Post by **Trevor Harvey** » Wed Dec 01, 2010 2:47 pm

OK next question, thinking outside the box, when will batteries not require changing? Thinking of "now, today" type of technology, yes, rubbish idea!Technology will advance.
And I would not suggest that the entire load bearing airframe would be one single battery, just bits, easily removed bits, like floor pans, door linings, seats etc.

Ian Melville · Post by **Ian Melville** » Wed Dec 01, 2010 3:25 pm

Anyone know more about the batteries the Rebel uses? I cannot make the numbers stack up
60kw will be something like 150A at 400v
30 min duration will need a 75AH 400v pack
112 Li-ION 80AH cells at 3.6v =403V and weight 246Kg

That's more than the whole aircraft weight, so my maths is wrong or there is a 'wonder' battery out there.

Love the cheap to operate comment

The batteries alone must be around 40 grand at trade prices

Ian Melville · Post by **Ian Melville** » Sat Dec 04, 2010 1:41 pm

Thanks to the latest Light Aviation I now know the sorce of the kit in the proposed Rebel.
Yuneec 60kw motor
The batteries are Li-Po, which are a variation of Li-Ion, and lighter. Still cannot make the numbers stack up, unless the battery pack is not an 'off the shelf' size.
I also suspect that the Yuneec website is out of date as a max discharge of 5C is well below the 25C or even 60C now in production

Dave Hall · Post by **Dave Hall** » Sun Dec 05, 2010 11:38 pm

I also noted the 'cheap to operate' - Roger's response to my observation was a wry grin.

I suspect the main hope is that the car industry will provide the means to develop battery technology further, but in this recent cold weather, I imagine those with electric cars in the UK will have been staying at home, or froze stiff while out on the road.

Brian Hope · Post by **Brian Hope** » Mon Dec 06, 2010 8:06 am

A friend of mine has an battery powered Berlingo and I'm pretty sure it has a petrol powered heater; it heats water and operates like a conventional car heater. He was up at the strip with it at the weekend as usual. It is very practical for short journies, the type which most people, apparently, make. He pays no tax on it and it doesn't have to have an MOT (I think because technicaly it is a commercial vehicle) - sort of an SSDR car!

Ian Melville · Post by **Ian Melville** » Mon Dec 06, 2010 6:35 pm

it heats water and operates like a conventional car heater

Does it make tea

Trevor Lyons · Post by **Trevor Lyons** » Fri Mar 04, 2011 9:54 am

As the earth's oil reserves diminish, it becomes increasingly important to develop alternative energy sources; and one of the most promising is the fuel cell. A fuel cell is a device that combines hydrogen & atmospheric oxygen to produce electricity to drive an electric motor, producing only water vapour as an exhaust product.

If fuel cell/electric-motor (FCEM) units were to power the world's cars, then the remaining oil could be used a a chemical resource rather than burnt as a fuel; and motor vehicle pollution would diminish to nothing. But although FCEM technology is almost ready for use, there is a problem: there are no filling stations where hydrogen is available to motorists. This is where light aviation could play a huge developmental role. If a handful of UK airfields were persuaded to supply hydrogen, and if some GA light aircraft were fitted with FCEMs, then the project could get going.

In a light aircraft, an electric motor would be ideal: small, light, compact, reliable, torquey and turbine-smooth. These qualities permit a fuselage with a very streamlined nose; and the smooth, vibrationless engine needs only the lightest engine mountings. The fuel-cell and the fuel itself can be located optimally; and the whole thing becomes a virtuous circle. To begin with, while the fuel-cells were still being perfected, the first aircraft might need to be hybrids. They could have a small array of lithium batteries charged on the ground from mains power and in the air from wing-mounted solar panels and from the fuel cell. (Even when fuel cells attain full development, such a hybrid set-up could yet prove to be ideal).

As FCEM aircraft became more common, more airfields could be be coaxed to sell hydrogen fuel and the project would snowball. In due course car manufacturers and filling stations would start to take notice, motorists would drive FCEM cars, and the world would change. After all, it didn't take too long before LPG was generally available. (Of course, it takes energy to isolate the hydrogen in the first place; but there are some very efficient and green ways to do this).

A major issue is: how to fund research? If a go-ahead GA consortium were to be set up (say the UK's Swift and Austria's Diamond), and if the national governments and/or the EU were to provide grants or cheap loans, there is a real chance of progress. If we Europeans don't do it first, the Japanese probably will!

Ian Melville · Post by **Ian Melville** » Fri Mar 04, 2011 10:20 am

I was wondering the other day what the opposite of a vicious circle was, now I know

These new technologies often have a chicken or egg situation, and FCEM is no different. It will take a brave company to invest sufficent money to ensure critical numbers of cars/aircraft are powered in this way. I am sure that any investment will be with cars, and not in aviation. Market size and the fact that cars can get away with imperfect technology.

I'm a big fan of electric motive power, and look forward to seeing it at an airfield near me.

Trevor Lyons · Post by **Trevor Lyons** » Fri Mar 04, 2011 2:47 pm

Ian Melville wrote: I am sure that any investment will be with cars, and not in aviation. Market size and the fact that cars can get away with imperfect technology..

Of course, the GA market is tiny compared to cars; but the FCEM needs to be tried out somewhere. It could perhaps be most easily done with small boats; but why not with aircraft? Any automotive company might find aircraft an effective way to test prototypes. True, cars can get away with imperfect technology; but a prototype FCEM aircraft would not be unsafe, particularly if it were a hybrid that could rely on its batteries and solar panels in the event of fuel-cell failure.

Bill McCarthy · Post by **Bill McCarthy** » Fri Mar 04, 2011 5:07 pm

There has been much behind the scenes efforts (in the submarine service) to extend battery endurance for main propulsion - hampered by the restriction that it has to survive the vagaries of a depth charge !

Ian Melville · Post by **Ian Melville** » Fri Mar 04, 2011 7:57 pm

Bill McCarthy wrote: it has to survive the vagaries of a depth charge !

About par with the kiddies school run then

Simon Clifton · Post by **Simon Clifton** » Wed Apr 27, 2011 4:04 pm

Okay - time to get this thread back to the top!

Lets review where we got to about a year ago:

1)We said that electric motors and controllers were good enough already, it's the energy storage that needs attention.

Were we right?

Yep - a year on batteries to give decent endurance are still far too expensive and far too heavy. I even think my 'maybe there in 5-years time' is looking optimistic. I've been experimenting with small LiPos, ESCs and brushless motors in the 20-20Amp range - good but a long way from full-size.

2) I said 'hybrid systems were the worst of both worlds'

Was I right? - well maybe not, when considering where we are with conventional reciprocating 4-stroke internal combustion engines. They get their power either through slow-rev large displacements and heavy build, or lighter high-rev with small displacements. These lighter engines need a reduction drive. There are no viable 20Kg-class 40HP 4-stroke reduction drive engines I can find, nor do I think it possible to make a good one.

How does that fit in with alternative power? Wouldn't a generator/electic motor fit the description of a reduction drive?

Via some kind of small battery pack, you could also get a current boost for take-off power.

Anyone know how to get 50Volts at 200Amps out of a 15,000RPM 250CC engine?

Cheers

Simon C
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