Toyota R&D team improves free piston linear generators

linear generator

Unlike a traditional ICE, which propels a drive shaft, a free piston engine linear generator (FPEG) is designed to generate electricity directly. Magnets attached to the piston move within a linear coil, converting kinetic energy to electrical energy.

A team from Toyota Central R&D Labs presented a prototype FPEG to the SAE in 2014. Now the Toyota researchers have developed a new FPEG control method that improves the stability and flexibility of the piston motion control.

In “Development of Free Piston Engine Linear Generator System Part 3—Novel Control Method of Linear Generator for to Improve Efficiency and Stability,” presented at the recent 2016 SAE World Congress, Kaznunari Moriya and colleagues explain that they had developed a target positon feedback control method, which worked well at low power, but was not able to maintain the piston swing motion when output power was increased. To address this issue, the team developed the new method, called “resonant pendulum” control.

“There are some technical challenges in ensuring an FPEG can achieve continuous operation over a long period,” write Moriya and his team. “Among these challenges, the piston motion control is the most significant factor in improving the robustness and efficiency of the FPEG because the combustion characteristics depend strongly on the piston motion, which is controlled by the linear generator. This paper describes a novel linear generator control method which realizes the simple harmonic oscillation governed by the piston mass and the air spring pressure.”


Source: Toyota via Green Car Congress

  • Electric Bill

    I wince to read such stories. We may need these fossil fuel contraptions for a few years more, but they feel ever so much like just so much root canal surgery– the most unwelcome parts of our lives, but inescapable. Oh, how I look forward to that day when we can live fume-free.

    • Tim Jonson

      By far the most effective thing humanity can do to fix our effect on climate is to reduce our population thru attrition. Say, one kid per urban couple and 2 or 3 for poor rural couples.

      • Jim Felder

        Actually considering that at least 18%(1) and perhaps as much as 51%(2) of the total net climate change impacts humans are having is due to what we choose to eat, namely animal agriculture. For comparison, the entire transportation sector (every car, truck, bus, train, ship and airplane) accounts for only 15%. So true there are too many of us for our little planet to bear long term, however the solution for that is also long-term. But, we can dramatically and immediately reduce the impact of those of us already here by changing what we eat. In addition animal agriculture is responsible for approximately 50% of all freshwater use (3) as well as as much as 90% of deforestation in the Amazon rainforest (4). So, yes we should address the population problem, but we all can have an immediate and profound impact today by simply eating different. Oh, and 70% of all chronic diseases and premature deaths have been found to be due to animal derived foods (and highly refined plant foods) (5). So doing what is good for the environment also ends up being what is good for you not to mention what is good for all the animals living in the hell on earth also known as industrial animal agriculture (just search for “Mercy for Animals” on YouTube (just don’t eat lunch first).


        • Tim Jonson

          So, keep overpopulating the earth with vegetarians….

          • Jim Felder

            Nope, we have to do both. We need to first stop the growth of the world’s population and then we have to slowly encourage the population to contract to something that the planet can withstand for the long term without crashing our economy. But that is going to take decades if not centuries and we need to make immediate changes right now, today, to avoid going over the edge of the climate change cliff. The only thing that we can do as individuals today is change our personal habits and the most impactful thing that we, especially in the industrial countries, do is decide what we put on our plates.

            In my opinion it is impossible to consider one’s self an environmentalist and consume animal products.

          • Johnny Van Styn

            In arid environments, meat from cows is the only product that can be raised – unless we start eating hay.

          • Jim Felder

            This is true that there people whose very survival is dependent on eating the animals that eat the meager grass that they can not. But that has nothing to do with the food environment in developed countries. We live in an environment of incredible excess where we can with ease obtain all the calories and nutrients we require from plant foods. So the needs of some people to rely on animal foods for survival is irrelevant to our situation.

            Consumption of animal products, especially those from factory farms, in the developed and developing countries is the largest single source of climate change of any other human activity. Thus our survival as a culture and possibly as a species depends on us not eating animals.

            Oh, and desertification in parts of the world where people are dependent on animal to turn inedible plant foods into edible meat, milk and eggs is largely due to overgrazing by those very same animals. They are locked into a death spiral largely of the own making. So unless we want to do the same thing to the entire earth, I strongly suggest we choose a different path.

        • Stewart

          Thanks for this post Jim. Very good summary. I also noticed you did a critical evaluation of climate change impact percentage and gave a range. We may eventually narrow it to something more precise but that broad range is extraordinarily compelling even on the low end.

      • Johnny Van Styn

        Yes. Let’s have stupid people have all the kids…

  • Ian Paterson

    Quite an innovative way of generating electricity. Would imagine the V/I will be way ahead of conventional alternator, quite brilliant concept.

  • Jim Fox

    I must be dumb- can’t see any advantage over shaft-driven generator, just added cost and complexity. And it still has problems??

    • Electric Bill


      I’m not sure I understand your question. 8 it is that you think a conventional generator with pistons and a crankshaft would be better, that would not necessarily be the case unless this design has problems with fouling spark plugs, vibration , etc.

      Any conventional four – stroke engine has lots of moving parts– the piston, connecting rod, crank shaft, valves, springs, cams, etc. The more moving parts, the more stuff to wear out, cause friction and inertial losses. That 80 one of the biggest advantages to EVs– very few moving parts. One of my own EVs only has 5 moving parts–not even a reverse gear.

      This generator design appears to only have one moving part, but like most piston engines appears to have a lot of sliding friction that could reduce efficiency. I also do not see how it could dampen vibration without more parts to counterbalance. I would not want to pass judgment on its efficiency or other mechanical aspects except to say that anything that runs on combusted hydrocarbons is environmentally bad and keeps us dependent on fossil fuels.

      • Tim Jonson

        The sliding piston is but a fraction of the friction in a conventional engine and drivetrain, variable compression and hcci is achievable, and they can gang the cylinders in groups of 4 to cancel vibration.

  • Knut Erik Ballestad

    The main thing with piston engine generators are these
    – The piston engines are extremely small (2 feet by 8 inches round)!
    – The engines have higher thermal efficiency than any traditional ICE engine.

    Therefore, this kind of engine is extremely well suited for plug-in hybrid vehicles.
    Even the BMW i3 Rex engine is big compared to these engines, and the fuel will give a lot more kWh’s with the piston engine.


  • Paul Maher

    You got the Thermal part right, but you don’t need this contraption. Thermoelectric Generators are on the rise.

    The interface between lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3) is a notable materials interface because it exhibits properties not found in its constituent materials. Individually, LaAlO3 and SrTiO3 are non-magnetic insulators, yet LaAlO3/SrTiO3 interfaces exhibit electrical conductivity,[1] superconductivity,[2] ferromagnetism,[3] large negative in-plane magnetoresistance,[4] and giant persistent photoconductivity.[5] The study of how these properties emerge at the LaAlO3/SrTiO3 interface is a growing area of research in condensed matter physics.

    So all you need is an LENR hybridized heat source and you’re in business. You say, “LENR is not a mature product !” Consider this upcoming meeting of Armed Services Committee and the Department of Defense’s report on the state of LENR, and perhaps other exciting new ways to extract energy from Matter.

    Potentially exciting news from the US with Congress’s Armed Services Committee requesting a new Report on the growing activities in LENR R&D in its FY2017 National Defense Authorization Act.
    “The committee is aware of recent positive developments in developing low-energy nuclear reactions (LENR), which produce ultra- clean, low-cost renewable energy that have strong national security implications. For example, according to the Defense Intelligence Agency (DIA), if LENR works it will be a ‘‘disruptive technology that could revolutionize energy production and storage.’’ The committee is also aware of the Defense Advanced Research Project Agency’s (DARPA) findings that other countries including China and India are moving forward with LENR programs of their own and that Japan has actually created its own investment fund to promote such technology. DIA has also assessed that Japan and Italy are leaders in the field and that Russia, China, Israel, and India are now devoting significant resources to LENR development. To better understand the national security implications of these developments, the committee directs the Secretary of Defense to provide a briefing on
    the military utility of recent U.S. industrial base LENR advancements to the House Committee on Armed Services by September 22, 2016. This briefing should examine the current state of research in the United States, how that compares to work being done internationally, and an assessment of the type of military applications where this technology could potentially be useful.”
    Join the discussion
    LENR Forum
    Twitter me @pmaher_art

    • nordlyst

      Wow. There are STILL people out there who believe in the LENR thing?

      I would love to be proved wrong, but it is going to take a bit more than Armed Services Committees (who have a track history of being rather too open-minded, or dare I say, gullible) to convince me LENR isn’t just another homeopathy.

      Let’s stick to stuff that is actually proven when planning to save the Earth. We can and should of course simultaneously try to turn unproven things into proven ones, we just shouldn’t be basing our plans on assertions like “if it works it’ll change everything!”, which would be about as prudent as spending your money today based on thinking like “if I win first price in the powerball, I’ll have *tons* of money”.

      • AlainCo

        they just have investigated and analysed litterature.
        It is not easy.

        it is easier to believe the hasty position taken after 40 days of bad calorimetry and some tweaking of dissentings data.

        Start by reading the Current Science special issue on LENR

        if you can get the book of Beaudette

        or you can just wait we do the job.

        • nordlyst


          Unlike some, I am not prepared to believe something just because somewhere on the Internet, someone claimed it was true.

          It is easy to find a whole library of books and an army of bloggers who say homeopathy isn’t just placebo. They have invented imaginative theories about water molecules having “memory” to allow there to be *some* hope for a possible mechanism by which it could work (since homeopathic “medicine” is water and doesn’t contain even a single molecule of the supposed active ingredient). If they truly believed this they should be working hard to prove it, because it’s obviously Nobel Prize winning stuff to prove water molecules have utterly new physical properties like memory. They don’t, and when you ask them why it’s due to the global conspiracy of scientists and especially physicists.

          Sounds like a real nut job? Crazy babble? Guess what LENR proponents who link to a blog and recommend a book look like to me..?

          I am not saying LENR is impossible. I don’t know enough physics to evaluate such a thing. And maybe nobody does. We do learn new stuff, even in physics, and may have many surprises still. But I won’t leap from “not absolutely impossible” to “plausible” to “probable” to “certain; there MUST be a conspiracy keeping the truth hidden” for the same reasons I don’t think the earth is flat. So if you really want to try and convince me, you will need to use different tactics and arguments than those of homeopaths and flat-earthers.

          • AlainCo

            your approach is good, but you just need to read the scientific papers, learn about calorimetry, about epistemology, …

            yout belief that LENr was debunked, is just a myth like homeopathy is.
            it is 4 papers, 3 refuted, the last one refuting the others and just proposing an explanation for the smallest result, not the big burst.

            Start by reading Beadette, and then read the numerous cited papers, and then read the Current science review and the cited papers, then read the peer reviewed papers available, including Ed Storms “Status of cold Fusion”.

          • nordlyst

            No. You’re still doing the flat earth thing. I will not read some biased subset of science I don’t know how to evaluate and a book that you selected to help me “interpret” what I read.

            I’m sure you’ll agree we cannot all be leading experts in all fields at once. So to navigate the world we use our common sense.

            If LENR works it would solve the energy crisis and make it radically easier to reduce GHG emissions like most of the world’s nations have pledged to do. It could make a LOT of people unimaginably rich.

            That leads me to ask why those who know how to do it and even have actually done it, and replicated it so that they know they really did it, and didn’t just make a mistake or suffer from faulty instruments or something – why do those people not BUILD IT and become not just vindicated, but rich beyond their wildest dreams in the process??

            But they don’t. Physicists, meanwhile, generally agree (a couple of exceptions does not change this fact) that the science is crap, the studies are flawed, LENR cannot work even in theory. Why would they say so?

            As far as I can see, I am required to buy into the whole “physicist conspiracy” to give this thing the slightest chance of not being bogus.

            Put your money where your mouth is. That Italian LENR scammer is always looking for investors (and never delivering anything).

          • AlainCo

            first of all, physicist don’t make money with something that work, but with something that is peer reviewed, and since LENR is mostly blocked in high impact journal, they prefer not to damage their career.

            see how pamela Mosir-Boss (ex US navy Spawar) describe the problem
   (first article page 6)

            Second, industrialist have funded LENR and found positive result, but only interesting for academic who are not interested by fear of reputation trap.
            LENR have a potential to be a fantastic energy source, but today it is a metalurgy and theoretical nightmare.
            Physicist are totally incompetent in that domain, where chemist and metallurgist are best, but since funding is blocked, things advance very slowly.
            eg see:

            what you say is just a catch 22.

            the catch 22 is evolving slowly because there is hope of application at medium term, maybe rationally, maybe irrationally, but only hope can make the hope be real.

            you should document more.

          • Johnny Van Styn

            And we have to use what works now instead of pinning our hopes on something that may never work out. We have the technology to go carbon neutral now, why not develop that now…

        • nordlyst

          How long do I need to wait? You see, the last round on this fad was ten years ago or so, and the practical home reactors were about two years away at that time, according to the smarties like you who convened in online fora with other believers to reinforce their faith in the product/Savior.

          Maybe you have a great explanation as to why people who are undoubtedly really smart, like Stephen Hawkins or Bill Gates or Warren Buffet, don’t invest in this stuff? Bill is even silly enough to invest in”high energy” nuclear (have a look at Terrapower, a more credible Savior than LENR).

          But a timeline would be welcome. Just so I know when to feel sure that you too have realized this stuff was just fluff.

      • Paul Maher

        You may find some of MY logic out of whack from time to time, But the same is not true of Louis DeChiaro from NAVSEA and Joseph Zawodny from NASA. Pull your head out of the sand long enough to listen to what those fellows have to say. NASA clearly wants to power Spaceplanes with LENR.
        Where did you leave your Forward Thinking spirit?

    • Tim Jonson

      Thermal Electric is an elegant, simple solution, yet with an order of magnitude deficient in efficiency, and no real hope of achieving the needed efficiency, so forget it.

      • Paul Maher

        What about TECTEG up in Canada?

    • Johnny Van Styn

      LFTR (Liquid Fluoride Thorium Reactor) was developed over 50 years ago in Oakridge National Labs. It’s technology that’s here now and was proven to work over 50 years ago. With LFTR, you can synthesize hydrocarbon fuels, desalinate water, generate electricity and make medical isotopes to treat cancer.

      Thorium will never run out. It’s too common and abundant on the earth’s crust.

      We can run around in our cars and airplanes with synthesized fuel made from CO2 in the air or oceans and make our deserts bloom with desalinated water from our oceans. The big difference is that we will be running our hydrocarbon powered vehicles in a carbon neutral manner instead of pumping carbon out of the ground and dumping it in the atmosphere as we do today.

  • Paul Maher

    It is nearly time to confront coming changes in our energy paradigms. Everybody is pussy footin’ around the several elephants in the room. Those Black Swan Pachyderm’s primarily being LENR, Photoswitching, advanced Thermoelectric-Photovoltaic Hybrids, and Zero Point Energy. There are NO moving parts in any of these rising technologies, and their adoption will free the world of fears of manmade global warming and sea level rise.
    I hope, and pray that the world is tuned into the UNCLASSIFIED parts of the Sept 22nd meeting of the Armed Services Committee and the DoE concerning the prospects of using LENR to power the Nation and its Military.

    • Tim Jonson

      Thermoelectics can achieve only a tiny fraction of the efficiencies of ICE engines, and LENR is only as safe as the culture it is used in. You really think Brazilians could handle this? In that country, literally everything is a failure.