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The wankel engine is being seriously looked at, and developed, for range extender duties in EVs. It promises to perform more efficiently at this role than a conventional piston engine with a crankshaft. That is good news as cars are moving towards EVs with range extenders to alleviate range anxiety. It may be more fuel efficient to run an EV with an efficient range extender than charge batteries from the electricity grid. Having the electric driving traction motors disconnected from the generating engine makes all this work efficiently allowing the generator to run at its most efficient constant speed and load independently of the demands of the driving electric motors. That means the on-board battery only needs to be big enough to be used as a buffer rather than the prime storage of on-board energy. Larger battery sets may be insisted upon to reduce emissions in cities, by running more on electricity giving zero emissions for most of running time.
It is argued that this is also the case for piston engines with crankshafts used as range-extenders, and that is true, however, the wankel's small size and weight with very smooth running and predicted greater efficiency at this role may preclude conventional piston engines.
As many manufacturers and research establishments are looking into small highly efficient range extenders, different approaches have been looked at. The two-stroke OPOC engine, backed by Bill Gates, looks to be a good range extender and is making it to production in China as a general purpose generator. But it still has a heavy bulky crankshaft, so it is just a modernised and greatly improved opposed piston design.
The problem with engines is that there are great inefficiencies to get "turning motion" in order to turn a generator. To make electricity turning motion is not needed. A piston moving up and down with coils in it is all that is needed. Working back from this then a crankshaft is not needed. The engine and generator can be combined into one compact efficient unit.
Toyota are developing a piston range extending generator with no crankshaft. The free piston moves up and down with coils in the piston and cylinder lining to produce electricity. Power is generated, via the electrical coils, on the downstroke and the upstroke of the piston in the Toyota and Germany's "NASA" free-piston generator engines. In a piston/crankshaft engine energy is only generated on every other one of the downstrokes in a 4-stroke cycle and only on the downstroke of a two-stroke cycle. Efficiency is clearly greater.
The piston of the Toyota engine is a top hat and "W" shaped affair. Think of a large can of beans with small can on top with coils around the large can. There is no crankshaft with an air spring returning the piston. It is also a two stroke design using computer controlled hydraulic exhaust poppet valves with no camshaft. The intake is via cylinder ports, like a diesel two-stroke. The unit is small and light and returned on the first run 42% efficiency about 9 months ago. Toyota hope to reach over 50%, when a conventional powertrain in a vehicle only returns about 20% efficiency this is a great advance in such a small mechanically simple unit. Over 50% efficiency in producing electricity is greater than the 40% efficiency (depending on where you live) of electricity from a power station to socket in the home.
The free piston engine is readily scalable upwards, as is also the wankel, to use in large trucks, buses, trains and ships. For the likes of ferries with electrically driven propellers giving independent control of each prop is a great advantage in manoeuvring.
Expect EVs with buffer batteries, using ultracapacitors for brake kinetic reclaim energy, and physically small free piston range extenders or wankel engines as the generators. Expect them to be mainstream well within 10 years. I would bet the the free piston unit over the wankel to be the eventual unit of choice. Some are predicting this will be the last internal combustion engine development before eventually they are fully superseded.
The issue with "new" technologies is that they may be "too little, too late". The day that battery technology improves by approx another 30 to 50%, which is not long away, is the day that all internal combustion engines in small to medium vehicles, and maybe larger vehicles, become obsolete. This is because once you reach ZERO tailpipe emissions every single environmental issue/problem and costs simply disappear. With emissions design development and then homologating costing upwards of $150m per platform, moving to a fully electric car cuts costs to such a degree that no manufacturer can afford not to do it.
Think of the issues that disappear completely, no: on-board diagnostics, catalyst ageing, urea injectors, high pressure common rail pumps, evaporative emissions, multiple drive cycles, testing on world-wide fuels, testing on a huge range of temperatures, thermostat monitoring, misfire monitoring, catalyst monitoring, injector ageing, etc, etc, all simply disappear, saving many million possibly billions. The savings just keep accumulate.
And then having any kind of engine in a car is going to become seriously un-cool.
So, if engineers asked management for say $300m to develop a new world beating internal combustion engine architecture, the management would rightly say "what are the risks?" and the risk is that the idea may become a white elephant overnight.
I see this free piston design as probably the last mass produced internal combustion engine development before obsolescence.
That sure is an amazing innovation. We need more of this type of thinking. Everyone wants electric cars to save the planet but they often forget that at the other end of that plug they use to recharge their "green" car is a coal fired, oil fired, nuclear power plant that is not so green. Solar, Wind and Hydro only produce a fraction of what it takes to run the world.
Any device that can squeeze out more MPG is a winner.
That sure is an amazing innovation. We need more of this type of thinking. Everyone wants electric cars to save the planet but they often forget that at the other end of that plug they use to recharge their "green" car is a coal fired, oil fired, nuclear power plant that is not so green. Solar, Wind and Hydro only produce a fraction of what it takes to run the world.
Any device that can squeeze out more MPG is a winner.
They are green in that they are orders of magnitude cleaner to burn the fuel at a regulated, centralized plant than in millions of deteriorating point sources (individual cars). Coal plants are being converted into even cleaner natural gas plants, and wind/hydro and solar are making up an increasingly larger portion of the domestic electricity grid, including individual homeowners who are going solar. Anything that reduces our reliance on oil and keeps us from importing oil is a good thing, no matter what you say.
The Toyota design by the vid is a 2 cycle engine. They are a known dirty emissions engine. Yeah it can be cleaned up but at what expense? Why use a dirty emissions engine when the idea behind a hybrid is low to zero emissions? This is stupid when Toyota has in its design arsenal a very competitent 2 cylinder diesel that is perfect for this application. I don't see this one happening at all. Diesel electric is going to be the future.
The VW design is based on their modification of the Dr Paul engine developed about 20-25 years ago. VW has mules running around in Europe using an engine design like it but with 2 crankshafts. Each shaft powers a separate transmission, one for the front drive and one for the back. Fuel mileage with the engine is supposed be over 100 mpg US. The Dr Paul engine you will never see even though it is a zero emissions engine. The issue is taxes. You can make your own fuel from garbage and the Feds have no way to tax you on it, so you can't have it. It's all about the money folks. Remember back in the 70's when they said on TV that by the year 2000 we'd be out of oil? Guess what? Get the money right and everything is great.
The Toyota design by the vid is a 2 cycle engine. They are a known dirty emissions engine. Yeah it can be cleaned up but at what expense?
Mercury Marine used two-strokes using the Australian Orbital direct injection system and meet emissions.
Forget diesels as it is just dirty. It emits particulates unless there is a filter on he exhaust. This Toyota engine will be running at a constant speed which ensures lower emissions, which can use ethanol, gasoline, diesel, etc. The idea behind a hybrid is using two types of propulsion, not low emissions, that is 100% EV territory.
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