This month I read of places without electricity for several days due to storm damage. Storm Arwen left me without electricity for several days, and the next village for longer.
My petrol Asda (10 years old) has repeated electric window failures, and I may have to replace it for that reason. I’m thinking of a used diesel – of a different make.
(Window stuck up at present, stuck down is disaster. Leaving taking it to main dealer who sold it, has serviced it, and has fixed the problem several times lately until I decide, so I can trade it in working.)
A friend has a plug-in hybrid here. Got it for the generous road tax reduction. He does ~200 mile legs, on which the battery does 30 miles and the other 170 is on diesel. Kia. Obviously not a good example of usage!
@Peter, it’s a very good example of PHEV usage if you compare it with the non-existent performance of pure EVs doing 400 miles or more in a day. My only interest in PHEVs is that if (God forbid) I am somebody forced by government to drive something with batteries I could drive long distances (e.g 700 miles per day) using the on-board gasoline engine.
There is talk of some of the current silly EV only mandates allowing plug in hybrids. I doubt I’d ever plug the thing in, but that would be my business.
I’m aiming for 200K miles with my current 2017 car that’s at 91K now. It has never had a single fault to date, only replacement of wear items, and has never been back to the dealer. Hopefully I’ll be able to replace it with something similarly utilitarian, attractive and cheap.
Silvaire wrote:
The idea with @LeSving’s Mazda Wankel version is that since the engine doesn’t get run much for some people’s PHEV service, the requirements for the engine shift towards power density (i.e. low weight) and away from efficiency and longevity.
It’s the exact opposite on the new Wankel compared with previous versions. The old Wankels were all about high power, high revving, fun driving. This new one is low revving (less than half the rpm compared with the old ones) and low power. It’s only 74 hp on one larger rotor. The older ones had two smaller rotors. The power density is very low compared with previous Wankels, but large compared with a similar hp piston engine. The car has 170 hp, all electric drive transmission. The Wankel is only connected to a generator, and it’s the steering of that generator that makes much of the “magic” (+ direct injection). It’s more like a dieselectric train, but with a battery.
In Norway the MX-30 r-ev costs about 10k Euro more than the all electric MX-30. Is it worth it? That’s up to each to decide, but there is nothing even remotely similar in terms of technology out there, and perhaps it never will be. I bet Mazda will eventually put that drive train into something more “fun” like some new version of RX or MX-5 though.
The thing with hybrid drive trains is that there are many different ways to do it. Some are more complex than others. The r-ev is in many ways the simplest version thinkable. Just an engine driving a generator, the rest is ordinary electric MX-30 tech, but with a smaller battery. Others are much more complex. The most popular hybrid in Norway (one of the most popular cars of all cars today, and has been for many years now) is the Mitsubishi Outlander PHEV. This is very complex car with a traditional piston engine, two electric motors, one on each axel, and one separate generator. It can run in all electric mode, series hybrid mode and parallel hybrid mode. In many ways the perfect car for driving in Norway, but it is large and complex. It will have a hard time competing with less complex technologies IMO. An all electric car can be built much cheaper.
I have had electric car since 2014, almost 10 years. I cannot see mee switching back to fossil fuel. Well except for that MX-30 R-EV 
The issues with Wankels are universal to the breed, mitigated by lower RPM. Wankel power density will still be higher than a piston engine (a good thing) and the efficiency lower (a bad thing but not so bad for a plug in hybrid). Tip seal wear will likely still be an issue, but less so in low rpm intermittent service.
Look up Alturdyne for previous work on Wankels used to drive high power density generators. I know several of the guys who did the work, now employed elsewhere. A connection to aircraft is that Alturdyne was earlier involved in development of alternate propulsion for the infamous Bede BD-5, as a sideline interest, which not surprisingly given that the original BD-5 engine was an unreliable but lightweight two-stroke, got them into Wankels. This was a long time ago but some of those involved are still active.
Here’s another similar but more recent activity in Germany.
Surely hybrid power systems are wasted in constant high power applications?
Peter wrote:
Surely hybrid power systems are wasted in constant high power applications?
That’s what I would think too. But what exactly is constant high power? How non-constant must it be before it is no longer constant high power? For ships, only the largest transports cruising for weeks at a time have direct propulsion from the engine. You have to travel at constant high power for a very long time before constant high power “layout” is beneficial. Is an aircraft constant high power? I don’t think so, not in a technical sense, not even close. Even trains are diesel electric for a reason, instead of direct diesel power (with a mechanical transmission for instance). The better solution is of course all electric.
There is the distinction between series hybrid and parallel hybrid. The Mitsubishi Outlander does both. Series hybrid is electric power “first” with assistance from an engine. The MX-30 R-EV is a series hybrid. Parallel hybrid is is the engine “first” with electrical assistance. For constant high power, the engine in a series hybrid can be thought of as a range extender, while in a parallel hybrid the electric motor can be thought of as extra power. Both will do “constant high power” output from the engine just fine. That is one of the main benefits of hybrid propulsion, making the engine run on best efficiency.
I think in aircraft there are incentives to make things as simple as possible, as light as possible and as compact as possible. A hybrid system will fail on all three. It’s simpler, lighter and more compact to mount the propeller straight onto the engine, or the electric motor. The benefit of all electric propulsion (battery electric) is unsurpassed simplicity and efficiency, which leads to cost reduction. It’s “only” the weight problem left
Peter wrote:
Surely hybrid power systems are wasted in constant high power applications?
Definitely. With your use case (long-distance cruise high on the right side of the power curve) hybrid does not make sense.
If one accepts slower flight closer to the most efficient speed, there is possible use case.
This (flying slower) is not done, because
a) it is slow and boring
b) the IC engine does not like working at low power
c) you need an engine with extra power for safe takeoff and climb performance anyway
d) once you have the extra power, you as well might use it, the engine hours are ticking…
With hybrid, you solve b) and c), you have no option of d) and have to live with a). Actually, the (weight penalty) cost of having extra peak power is not that high with hybrid. You can have your fun of high-powered flight (e.g. super-fast takeoff and initial climb, maybe a few minutes of aerobatics), but it won’t last long.
Another selling point: That great takeoff and (initial) climb performance is good for safety, maybe you can even quickly climb across a freezing layer. Also, if done smartly, the electric motor can function as a back-up if your primary IC engine fails – won’t save you in mid-ocean failure, but could be a life-saver on engine failures low above the ground (takeoff/landing/hilly terrain).
IMHO sizing the electric engine power to just match the peak performance of IC-equipped plane would be mistake, you want extra spice as an extra selling point. As with Tesla, you can pretend to be saving the environment, but the emotional buying decision comes also from the thrill of pressing the accelerator and really feeling it.
However, as with everything GA, low volumes mean no real developments, so I don’t expect anybody will do it. The niche is there, though.
There is another thread for GA but the only use case I am aware of is basically power gliders; these need power to get up but can cruise at lower power, close to Vbg. Negligible market…
In shipping, the new name of the game, I am told, is “slow sailing”, around 9kt. 25 days from China to N Europe, but the “MPG” is good. I have no idea if these ships can do 15kt or whatever and are just going slowly. 25 days is great for the customer’s cash flow (not)!
My take on hybrid cars, starting with the Pious years ago, is that this primarily was a technology development platform, and secondarily a great piece of green marketing which you could but buy at any price. There are advantages if you do a lot of city driving, so it is not a total waste. The mfgs did a lot of R&D on the back of this, on electric motors, electronics, etc. The word “Pious” is another old Toyota Prius joke – not dissimilar to the many jokes about pilots telling everybody how great they are.
LeSving wrote:
Even trains are diesel electric for a reason, instead of direct diesel power (with a mechanical transmission for instance). The better solution is of course all electric.
Unlike an aircraft, a diesel loco has to do some kind of torque conversion to move from a standing start. For thousands of horsepower levels, electric transmission is the most efficient. (Others have been done – lighter trains can have hydraulic or mechanical transmission, e.g. the BR first generation DMUs had 4 speed manual gearboxes with a fluid coupling so you didn’t need a clutch, rather similar to a bus transmission, some modern DMUs have mechanical transmissions e.g. the BR class 172 has a 6 speed automatic transmission, the Germans and BR western region went with hydraulic transmissions for locomotives in the 1960s. There was one bizarre 2000hp mechanical transmission locomotive designed by the LMS and put into service by British Rail which had no fewer than 6 engines (the Fell locomotive). It used roots blowers powered by their own diesel engines to make the immense amount of torque required to move from a standing start. https://en.wikipedia.org/wiki/British_Rail_10100
But you don’t have the move away from a standing start problem for an aircraft. A propeller can easily be turned from a standing start, the air acting as the fluid part of the transmission, so you don’t have the major problem of the need to multiply torque to get moving from a standing start that you do with a train or with a car. It’s most efficient therefore just to bolt the prop to the end of the crank and not have any kind of transmission.
