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Aquarius Engines unveils free-piston linear engine operating on 100% hydrogen

Israel-based Aquarius Engines unveiled a hydrogen-fueled version of its free-piston linear engine new hydrogen engine. The 10kg machine, based on the same technology as the original patented single-piston linear engine, operates exclusively on hydrogen.

The new Aquarius Hydrogen Engine’s lightweight design and unique internal-gas-exchange-method would greatly reduce emissions and lower the global carbon footprint.


The Aquarius free-piston linear engine which now operates 100% on hydrogen.

Aquarius Engines waited to unveil the new hydrogen engine until after successful third-party tests were conducted by AVL-Schrick. The tests demonstrated that a modified version of the original Aquarius Engine can fully operate on hydrogen.

The original Aquarius Engines Generator is currently undergoing successful field tests in North America, Europe, Asia and Australasia. Aquarius Engines recently announced partnership deals with Nokia in the field of remote communication and energy equipment management in addition to establishing a subsidiary in Tokyo and partnering with Japanese auto-parts manufacturers TPR and Honda-affiliate Musashi Seimitsu.

The 10kg Aquarius Engine was invented in 2014 and is designed to be used as an onboard power generator in a vehicle or as a stand-alone electricity generator. Unlike most conventional engines that are made of hundreds of parts, the Aquarius Engine has just twenty components and one moving part. The lightweight streamlined design makes it inexpensive and highly efficient with minimal need for maintenance, compared to traditional engines.

The Aquarius Engines technology currently has around two dozen patents registered worldwide. Aquarius Engines has manufacturing and development centers in Israel, Germany and Poland.



OK, so you have a very simple linear engine, and you then run it on H2, which is NOT a simple gas to work with. IMO, you'd be better sticking to methane (bio or fossil) as it is easier to store and manage generally.



They seem to be managing to use hydrogen, and storage in cylinders is now a reasonably mature technology.

Hydrogen is also zero emission at point of use, so a PHEV using this as an RE would remain a ZEV.

Methane ain't ZEV at point of use.

The Lurking Jerk

@ Davemart

Burning hydrogen isn't zero emission at point of use either.
I agree with mahonj, use methane, which is much cheaper to harvest and handle.
This kind of engine, used as a range extender, would be a Godsend for electric cars in cold, rural climates where people have to drive 100 miles to buy a loaf of bread.
I reject the whole notion that we must all drive zero emission vehicles soon. That is so absolute and absurd. Eliminating the vast majority of our emissions and fossil fuel use will be more than good enough.

I have spoken.


It is absurd to seek to equate any tiny residual emissions from burning hydrogen with the substantial output from combusting methane.

Of course, if you use fuel cells, they are zero anyway, but even in an ICE the comparison is daft when you have nitrous oxide emissions and all sorts from burning methane.

And nowhere have I said that there should be an absolute prohibition of reducing rather than eliminating emissions.

Since there is a solution to hand which is near enough absolute zero, then using methane is the one with the case to prove however.

Albert E Short

I see several articles but none mention power output. Has anyone seen anything?


@Dave, you have touched on a key point - does it have to be "zero emissions" or just "better" and if so, how much "better" is worthwhile.
People were fairly happy with hybrids like the Prius, even though it was only 30% better than a typical gasoline car.
However, the bigger win was getting people out of trucks and into cars, preferably Prii or better.
Sometimes, going for a full Zev solution may end up with an unaffordable or greatly delayed solution, whereas a good enough solution can be rolled out quickly.

A good approach would be carbon rationing, like food rationing in WW2 in the UK. That would get people making some tricky decisions, but would be hard to roll out without an emergency, and a climate emergency comes up so slowly that it is unlikely to happen.
Here's a book on rationing if you are interested: "Eggs or Anarchy".

Account Deleted

Not much technical information available. The Aquarius Engine homepage shows a "16kW device", so that looks like the power. It has a single linear piston (only moving part) inside a valveless 800cc cylinder, generating power from electromagnetic coils with each stroke.
Since a Range Extender needs to be simple and efficient, this engine looks good.
Fuel choice depends on what you have available and can be safely stored for long periods.


16kW is enough to drive a Tesla 3 at ~110 kph, so it would make a good range extender for a small EV - any EV if you are using it to limp home rather than blam along the motorway.
Agree with gryf, could make a nice range extender.
In that case, you could drop the battery size to say 20-25 kWh, like a Mk1 Leaf.

(Obviously a more powerful device would be better, but what you have there is enough to get started with).


NOX is a GHG


Toyota who are developing hydrogen ICE for racing reckon:

' Fuel cell electrified vehicles (FCEVs) such as Toyota's Mirai use a fuel cell in which hydrogen chemically reacts with oxygen in the air to produce electricity that powers an electric motor. Meanwhile, hydrogen engines generate power through the combustion of hydrogen using fuel supply and injection systems that have been modified from those used with gasoline engines. Except for the combustion of minute amounts of engine oil during driving, which is also the case with gasoline engines, hydrogen engines emit zero CO2 when in use.'

They don't mention NOx, but JCB reckon that it is less than a diesel engine, even one which uses the latest technology to reduce it by 98%, and think that they will be able to reduce it further to amounts too small to measure:

Westport say that their GHG emissions are near zero:

This is princess and the pea stuff, there looks like no realist emission problem for hydrogen ICE even against the highest possible standards for gasoline and diesel, let alone what is on the road at the moment.


I have to agree with Dave on the emissions thing. H2 ICE tailpipe emissions are not an issue.
What is an issue is the source of the H2: green, blue, turquoise, brown or grey hydrogen anyone?


I get fed up arguing against extremist views from both sides, who have in common that they think that they have all the answers.

I recently debated with a knowledgeable energy forecaster who works for a coal company.
He decried what he called fake costings showing renewables as the cheapest energy source, on the grounds that intermittency and subsidies were not counted, or not counted properly.

I would agree that there is one heck of a lot of faking 'for the greater good' happening now as it always has by the green lobby, having put in the hard yards on some occasions to take their costings apart.

But closer examination and questioning revealed that the costings he does take into account whatever the state of play of legislation for reduction in GHG, but nothing at all for any further reduction, even were a big reduction achievable cheaply.

He said 'external costs are just that, external'.

IOW, no value at all is attached to GHG reduction, and the climate is supposed to be infinitely forgiving, just as buffalo were in infinite supply so slaughtering them was of no concern, as there were plenty more where they came from.

I can see where that line of thought comes from, in a coal forecaster fighting for industry survival, but it leads even supposing something is technically doable to not looking properly into for instance carbon sequestration. And I am not interested in the proclamations of greens on the other hand, who seek to rule out sequestration absolutely based on their theory that it will never work, or rather their emotional choice of means to the preferred end.

So the answer for me about green, blue, or any other shade of hydrogen is to see what works.

Incidentally EP has fulminated on many occasions here against hydrogen.

It is becoming ever clearer that it is a superb fit with nuclear power, and the new factory built 4th generation reactors have hydrogen generation upping capacity use and improving economics firmly in mind.

I am just as uninterested in absolutist claims against nuclear power.

How safe and how cheap are my evaluating questions, not the outpourings of godlike beings who imagine that they can rule things in or out according to their own prejudices.

A 4th generation SNR is not a Chernobyl series reactor.

They simply have the name nuclear in common, enough to trigger a Pavolovian reaction in Greennuts.


...hydrogen combustion can produce oxides of nitrogen, known as NOx. In this way, the combustion process is much like other high temperature combustion fuels, such as kerosene, gasoline, diesel or natural gas.


Thanks, SJC, for the comment about NOx! I was about to write that myself. Hydrogen has among the highest flame temperatures of any fuel. Thus, its NOx production is the highest I know among potential engine fuels. NOx production can be abated with “in-cylinder” measures and in the aftertreatment system, but this is far from trivial. I will not elaborate on that further here. Regarding NOx, hydrogen is far from a “clean” fuel.


Fair enough. It looks like fuel cells it is then, when practical.
Fortunately costs are falling fast.


IMO, for range extenders, which won't be used very much, you could just use nat gas or a liquid fuel, like gasoline or ethanol or a blend.
It won't be perfect (i.e. zero emissions) but it will be a whole lot better than doing nothing, or lugging huge batteries around (really ?).
Looking at Aquarius engines, I wonder why they (and all the other free piston engine companies) are not more successful.
@Dave, I have no objections to nukes - they could be used for electricity and district heating if people could get organised.


Car makers are considering high temperature PEM


Stellantis is going for fuel cell range extenders in its vans and trucks, from 5KW up to 45KW or more:

The system is already well proven, with substantial numbers of Renault Kangoo vans using them for some time.

Account Deleted

Does your knowledgeable energy forecaster think his Coal Company will pay for all the Coal Plant Tailings at every power plant and mine where millions of tons of waste are piled.
I have a long history of living and working around the problems with Coal (my first job was optimizing the dispatch of Coal from the mine to the power plant at Southern Company Services.
It is an archaic fossil fuel that needs to be kept in the ground and put into the history books like burning Whale Oil for lamps.


@ gryf

As I noted, he argues and costs for:

' He said 'external costs are just that, external'.'

I replied that responsible companies who want to stay in business such as TMC and Polestar would not even consider a submission which took no account of energy and GHG emissions, and they work to an accounting system for them as well as in dollars to reduce them to neutral.

And I further remarked that only loser companies would entertain submissions which were in no way in accord with either the clearly established science of AGW or the political realities, and that costings based on them were even worse and less realistic than the remarkably fanciful 'costings' of green nuts.

Strangely, he has not replied.....


@SJC - from Wikipedia
"Typically hydrogen engines are designed to use about twice as much air as theoretically required for complete combustion. At this air/fuel ratio, the formation of NOx is reduced to near zero. Unfortunately, this also reduces the power output to about half that of a similarly sized gasoline engine. "
This would explain why a 800 cc engine only generates 16 kW.
So the simple H2 ICE may have a place (as long as you can source Green or clean H2).

It looks like there is going to be a lot of green H2 (or ammonia) around in 5-10 years.


The bad news is that H2 combustion can produce dangerously high levels of nitrogen oxide (NOx). Two European studies have found that burning hydrogen-enriched natural gas in an industrial setting can lead to NOx emissions up to six times that of methane


However, at a stoichiometric air/fuel ratio, the combustion temperature is very high and as a result it will form a large amount of nitrogen oxides (NOx)

Liviu Giurca

The NOx emissions can be drastically reduced during combustion with water injection. This complicates the engine a bit but not at the level at which the fuel cell does. That is why it becomes interesting to use an engine as simple as possible, preferably supercharged, like the one described in
The proponents of the fuel cell forget to mention that the hydrogen used by this must have a purity of 99.97%. Otherwise the fuel cell can be destroyed. Not applicable for internal combustion engine.


Hi Livia

Your comments on purity are accurate for PEM fuel cells, although it should be noted that thousands of cars, buses and fork lift trucks have been refueled now for some years without their being destroyed, so although purifying the hydrogen to that degree is somewhat expensive in energy, we have mastered the technology.

It does not apply to other varieties of fuel cell such as SOFC

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