Gym Equipment Converted To Generator

Energy cannot be created or destroyed, but the most likely eventual conclusion of changing it from one form or another will be relatively useless heat. For those that workout with certain gym equipment, the change from chemical energy to heat is direct and completely wasted for anything other than keeping in shape. [Oliver] wanted to add a step in the middle to recover some of this energy, though, and built some gym equipment with a built-in generator.

Right now he has started with the obvious exercise bike stand, which lends itself to being converted to a generator quite easily. It already had a fairly rudimentary motor-like apparatus in it in order to provide mechanical resistance, so at first glance it seems like simply adding some wires in the right spots would net some energy output. This didn’t turn out to be quite so easy, but after a couple of attempts [Oliver] was able to get a trickle of energy out to charge a phone, and with some more in-depth tinkering on the motor he finally was able to get a more usable amount of energy to even charge a laptop.

He estimates around 30 watts of power can be produced with this setup, which is not bad for a motor that was never designed for anything other than mechanical resistance. We look forward to seeing some other equipment converted to produce energy too, like a rowing machine or treadmill. Or, maybe take a different route and tie the exercise equipment into the Internet connection instead.

39 thoughts on “Gym Equipment Converted To Generator

  1. Would be of interest and potentially open markets rather for home power generation & to mains or home battery but, would need regulatory authorities to come on board with modern electronics such as if feeding power back into mains through domestic plugs with appropriate interlock safeties. Not difficult to phase usefully into AC mains and if done well increases overall power factor too Eg Feed back bulk at highest peak (reduce flat topping etc) where many power supplies around still don’t have power factor corrections. Looking forward to comments, cheers

    Thanks for posting :-)

    1. It would be an utter waste of resources. The amount of energy involved is insignificant. There are far better uses of labor and capital than something like this.

      It’s a fun project for the sake of a project but this is not a viable energy source.

    2. There are already some everyday devices in your home that feed power back into the grid briefly.

      For example, if you take an electric whisk and adjust the speed from “high” to “low” the extra momentum as the motor slows down is put back into the grid. There is no certification required of a whisk to do that. The effect is substantial enough that you can see a mechanical electricity meter turn backwards briefly while you do it.

    3. Average fit human will output something around 150W to 250W for one hour – that would be a real training not just casual ride. That is very little when compared to how much average house consume. To give you good picture check youtube for “toster challenge” where Olympic medalists are trying to make a tost using stationary bike. If you assume that whole familily at once would output 1kW from their set of bikes this would be less than good vacuum cleaner or air conditioner.

      But if we could only plug it to our TV so that we can watch it only when ridding we would watch less of it and excersize more. It is also interesting option for blackout situation. You could charge your phone or provide some light, maybe even make a moka if you are fit.

      1. I’d put the moka on a little alcohol burner, heating up that water and the whole moka pot is quite an intensive workout.

        But otherwise, you can run the coffee grinder (200w for 10 seconds or so) with relative ease, light up a room brightly with LED lights, run a modem and router, and charge a laptop.

    4. Interestingly enough, my exercise bike had this feature as standard. It has two USB ports for charging an iPad or so. These ports work even when not exercising if the bike is plugged into the wall, but there only work while exercising if the bike isn’t plugged in.

      1. I used to work out on a cross trainer that had a power output reading that seemed to have been driven by the power generated in the electrically loaded generator it used to control the load.

        It would take me about twenty minutes to coax the idiot computer controlling the thing to jack up the load. Once I got the stupid thing to understand that, yes, I really did want to work out slow but hard it would jack up the load to its maximum of 500 watts.

        Fat and out of shape as I am, I could push that 500 watts for over an hour without a break.

        Most exercises seem to be laid out to be as inefficient as possible. The cross trainer would let me work as efficiently as my body would go.

        I expect there’s a lot of improvement you could make to a human driven generator – if you concentrate on efficiently extracting power.

        Not to say that the power meter of the cross trainer was accurate – it may have been way off.

        Regardless, I was the only one in the gym who ever drove it to its limits because I worked to get the most power output rather than running fast or whatever.

          1. This is why I won’t let my wife chuck out that 400W single cup coffee maker. … way more likely to be able to find 400W than 1200 when the inevitable collapse of society happens any moment now.

        1. 500 W for an hour? Dubious in the extreme.
          If that’s like the trainers at my gym, its very likely *input* power or food energy, in kcal per hour, kJ/hr, or watts (user selectable on the fly). Output power is, at best, 30% of input, and more usually 20%.
          Still, 100 W actual output power for an hour is pretty darned good for “Fat and out of shape”.

    1. There are (or at least were) some gyms that advertised by delivering human created electric energy back to the power net but it does not seem practical to me, and the amount of energy is negligible. something you pay EUR10 to work yourself into sweat, and then you generated 5ct worth of energy. I suspect that even over the whole lifetime of the equipment the generated electricity won’t even cover the cost of the dynamo’s, wiring and inverters to get the energy on the ‘net.

      Human powerd bycicles have been used for emergency purposes (such as those atomic bomb shelters) and very remote locations.

      For a gym, it seems more practical to turn of the airco and put fans on the bicycles, so you only get a breeze when you pedal fast enough. That also gives some direct feedback to keep up the motivation.

      Note though, that I’ve never been in such a gym myself. I just don’t get the idea to pay money to go sweat in an enclosed room.

      1. I know a nearby 1950’s era “civil defense” shelter here has 4 bicycles for “emergency power generation”. They were connected to one common axle, which turned a small dynamo that powered something like a few 6V bicycle lights in every room (only enough light to not bump into things after you’ve adjusted for 15 minutes). Also connected (mechanical, not electrical) was a fan to keep the air filtration and ventilation systems working. I suppose that took the majority of power input.

        There was a tour and a lady asked “Oh, is this the gym”? The tour guide: “In the 1950’s there weren’t gyms. Life itself was the gym!”

      2. The amateur radio club I’m in has in the club room an old stationary exercise bike (the kind with a large solid wheel and a tension belt to provide resistance) with a car alternator attached to it. Every now and then it gets pulled out for ARRL Field Day. Someone pedaling the bike can provide enough power to run an HF radio in receive mode but once someone hits the transmit button, the load on the alternator brings everything to a stop and it’s like riding into a wall. It’s a fun exercise to demonstrate an alternative power source and good for a few laughs.

    2. This article from Road Bike Rider https://www.roadbikerider.com/average-wattage-cycling/ suggests cycling power-output, scales with the rider’s weight and ranges, depending on ability, from 2.4 to 5.6 W/Kg for a one hour ride. Assuming an 80Kg cyclist and 50% efficiency that gives 96Wh.

      There’s the Toaster Challenge on YouTube, where participants have to toast bread with a bike hooked-up to a 700W toaster. Robert Förstemann succeeds https://www.youtube.com/watch?v=S4O5voOCqAQ.

    3. When I worked at Intel, the stationary bicycles had USB ports for charging your smartphone or tablet. It predates USB-PD so only 10W, but it’s something.

      I’d imagine an updated version with USB-PD would be great in a public area. A quick workout that charges up your device a decent amount.

    4. This has the sound of a very dark sci-fi movie where all the humans on Earth must take shifts in gyms generating power for our computer machine overlords. Do I take the Red pill or the Blue pill ?

    1. The process of figuring out the voltage at the maximum power point isn’t as simple as it seems because you aren’t merely trying to extract as much energy as possible right now, but to consider the momentum of the pedals (ie. extracting a lot of energy to the extent the user can no longer maintain that pedalling pace is no good). You also really want to know the level of ‘tiredness’ of the pedaller – you may get more energy out if they pedal gently for 2 hours vs pedalling really hard for 5 minutes.

      Unlike the MPPT tech of solar panels, where there is no consideration necessary for ‘tiring out the sun’.

  2. I had a colleague years ago that had one of these for the shared television in his kid’s rec room.

    To keep the TV on, they had to cooperate so that one of them kept pedaling. They didn’t need to generate all the necessary power for the television, just a token amount to keep a relay closed. The idea was to let them watch some television like normal kids, but dissuade them from wasting hours in front of it mindlessly.

    There were enough smarts in the system to keep the show going for the time it took them to swap out riders. Apparently it devolved into a race between Gary and his kids to develop software that was lenient enough to allow them to take a momentary break, but not let them game the system.

  3. Even if the power output is minimal? Wiring it so you could plug a USB power pack in to charge it a little while you do cardio is not nothing.

    Plus it’s just plain neat. Park your bike on this thing and on rainy/cold/etc days, hop on this thing for awhile.

    1. … to power a fridge. Even back then I thought it was ridiculous. A fridge eats 1 kWh/day.
      But then, the whole movie was ridiculous, even worse than the book.

      Hey, waitaminute… the movie was set in 2022…

  4. I was about to add that too.
    In the late 70’s AMF the bowling pinsetter people bought Harley Davidson and at the time I saw in one of those pop-sci zines the AMF exerciser stationary bike with a revolutionary plastic drive belt. Yeah it rotted into pieces. A couple of decades ago I saw one on the curb and it has sat on my porch since then. It has a Chrysler alternator(tm) and a line powered time and load computer panel. Under the yellow plastic hood along with everything else is a big power resistor that is the heat dump.
    A Harley bike generator who’d have guessed!

    1. I have calculated the energy needed to power my recumbent tricycle as between 100 and 130 watts on the level, depending on speed. As a 70+ year-old, I can manage 150 watts for a few minutes. A well-trained youngster could probably double my figures. I recall the first human-powered aircraft required about 250 watts to maintain level flight and needed both fit and capable cyclists. My estimate is that it would be hard to exceed 250 watts for periods of hours, although the successful flights of human-powered aircraft show it is possible. 500 watts seems improbable.

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