[HN Gopher] How to build a bike generator with control panel ___________________________________________________________________ How to build a bike generator with control panel Author : jfoucher Score : 84 points Date : 2022-03-07 16:21 UTC (6 hours ago) (HTM) web link (solar.lowtechmagazine.com) (TXT) w3m dump (solar.lowtechmagazine.com) | mixedmath wrote: | I'm impressed at the relatively high efficiency of the system. | Pedalling at 150 watts and recovering 100 watts of electricity is | higher than I would have expected from such a simple system. | | I'm very curious how much better the system would perform if the | flywheel were attached directly to the drive-train instead of via | friction roller. In practice this might not give much higher | efficiency, but I would guess that the chain and primary sprocket | would wear out slower than a tire friction-running a flywheel. | | (They mention that they don't do this because this because it | would be harder to build. I believe that. But I'm still curious.) | samatman wrote: | I've done enough bike wrenching to have raised an eyebrow on | that. | | What you need is two gears on the flywheel, rather than one, a | gear rather than a friction wheel on the generator, and some | way of tensioning the second chain which you run between them. | This isn't the kind of harder to build that should stand in the | way, although I will grant that the single gear was already on | the wheel and changing that does involve, well, changing that. | | This gets ~10% efficiency back, which for a generator is huge. | It's probably the only efficiency gain left, other than a gear | cassette to optimize power to a target voltage. | gruez wrote: | > I'm impressed at the relatively high efficiency of the | system. Pedalling at 150 watts and recovering 100 watts of | electricity is higher than I would have expected from such a | simple system. | | It doesn't seem very surprising that motion can be converted to | electricity at 66% efficiency. Normal power plants[1] can | convert heat to electricity at 64% efficiency. It'll be much | more interesting to see the end to end efficiency of this, ie. | how many calories were consumed compared to electricity were | generated. | | [1] https://en.wikipedia.org/wiki/Combined_cycle_power_plant | KennyBlanken wrote: | A well-trained athlete can achieve about 33% efficiency in | terms of calories used (not 'consumed' - we're talking about | energy coming from glycogen and fat, in addition to whatever | is eaten. The human digestive system can only process a | couple hundred calories per hour before it starts diverting | blood flow to the digestive system, which impairs athletic | performance significantly.) | 1-more wrote: | > but I would guess that the chain and primary sprocket would | wear out slower than a tire friction-running a flywheel. | | Yeah, direct drive trainers vs wheel-on trainers have the | advantage of not ruining a tire or requiring a trainer specific | tire. | gwbas1c wrote: | It's be interesting to have this wired to an electric car | charger. | ygra wrote: | I guess the more sensible option would just be to use a bicycle | to get around. Simply because with the car you require most | power just to get the car moving, not so much the person | inside. | dahfizz wrote: | At 100 Watts output, it would take 800 hours of biking to fill | a tesla battery pack. | Ottolay wrote: | This is so cool. Viable for LED lighting in an off-grid situation | when there is little sunshine for solar panels. | fuzzy2 wrote: | Reminds me of the toaster challenge video[1] where Robert | Forstemann, German track cyclist, powers a 700 Watt toaster for | over a minute on an exercise bike. Absolutely insane. | | [1]: https://www.youtube.com/watch?v=S4O5voOCqAQ | jdechko wrote: | That was my first thought as well. | rootusrootus wrote: | 150W is a pretty good workout sustained for an hour. Humans can | do what, maybe 1000W or so at peak? Non-athletes, I mean. But | nobody is putting out 1000W for very long. I'd have guessed that | over an hour 75W-100W is more realistic. I recall playing around | with a bike generator at the local power plant about 30 years ago | and it was _hard_ to keep a regular light bulb lit for any length | of time. | matsemann wrote: | I like to bike, but am just an amateur. My ftp is ~280W, which | is what I can sustain for a long time without accruing too much | lactic acid. I've held 200+W for hours. Just to give a | baseline. A heavier person could probably do even more. | | A track cyclist can reach 2000+W bursts, but they are freaks. | masklinn wrote: | > Humans can do what, maybe 1000W or so at peak? Non-athletes, | I mean. | | 1000W is "trained biker sprinting". | | > I'd have guessed that over an hour 75W-100W is more | realistic. | | The mechanical output which can be maintained over a work day | is generally estimated around 75W. So accounting for losses | 100We for an hours is realistic but vigorous effort. | thehappypm wrote: | It would be a lot easier today, LED bulbs are about 10x more | efficient! Someone outputting 100W could light up an apartment. | olau wrote: | I was curious whether they talked about the practicality of the | whole setup, and they do, e.g. | | > Electric kettles that run on grid power are often very powerful | and boil water in a matter of minutes or even seconds. Boiling | water using a bicycle generator will take a lot more time, but | it's perfectly possible. We acquired a commercial 12V electric | kettle with a vacuum insulated reservoir of one litre. During a | test, boiling water for one cup of tea took slightly more than | one hour at an average power production of 60W. | | To be honest, although I realize it would be ridiculous, but if | inverters were small and cheap, I would personally prefer having | an exercise bike plugged into the grid. That way my exercise | energy would at least be useful to someone, somewhere. | moltke wrote: | I think you'd be better off plugging it into a kettle or coffee | maker. At one hour per cup that sounds like good exercise and | having a goal sounds like good motivation. | Johnny555 wrote: | _but if inverters were small and cheap, I would personally | prefer having an exercise bike plugged into the grid. That way | my exercise energy would at least be useful to someone, | somewhere._ | | You'd likely never produce enough energy to offset the energy | used to create the inverter. | | Just to come up with a rough estimate, if the bicycle grid-tie | inverter cost $200, and 25% of that cost is due to energy @ | $0.10/Kwh, that's 500KwH of energy wrapped up in that inverter. | If you produce an average of 100W while biking, that's 5000 | hours of biking, or about 10 years of biking 10 hours a week. | | It might be more practical if you could harness all of the | bikes in a busy gym where you could get hundreds of bike-hours | of energy a day. | | (Ok, I made some pretty big assumptions here. First, I don't | know how much energy goes into making a product or how much it | costs, and it's not all electricity, there's diesel and natrual | gas in mining and processing raw materials, etc). | | (Edit: my guess is probably not too far off, a typical phone in | 2008 had around 180MJ/50Kwh of embodied energy [1], so 10X that | amount for a 10 or 20 pound grid-tie inverter might be in the | right ballpark. Aluminum alone has around 200MJ/kg embodied | energy so a 2 pound heat sink would account for around 50KWh of | the embodied energy of the device) | | [1] https://www.lowtechmagazine.com/2008/02/the-right- | to-35.html | qqqwerty wrote: | I have a philosophical issue with the embodied energy | critiques. Primarily, it is that individuals who are trying | to push the world in a carbon free direction would also | likely prefer that the goods that they consume also be | manufactured using carbon free energy. Additionally, these | analyses rarely take into account positive second order | effects. For example if someone puts solar panels on a | northern facing roof in Canada, they are unlikely to ever | realize a breakeven point, and the project might not offset | the embodied energy of the system (and associated emissions). | But that purchase means more revenues and jobs for the solar | industry. And in turn that means more investment and more | economies of scale. | | Basically, if we want to transition to a carbon neutral | world, it is going to require a lot of people | investing/purchasing projects/goods that do not make sense | economically and might not initially be carbon neutral after | accounting for embodied energy. Without early supporters we | can only rely on government subsidies (which we already do, | but obviously not enough). I personally don't think the free | market can solve climate change, but if it is going to have a | chance, we are going to need a lot of people to make these | types of purchases/investments. | | Also, another thing to consider is that the inverters | lifetime is going to be directly correlated to the operating | hours. So if the OP wants to hook up his exercise bike to the | grid (assuming it is legal in their area), and then down the | road decides to get some solar panels, that inverter will | work perfectly fine for that purpose and have minimal | degradation. | ASalazarMX wrote: | You can't deny that it's borderline foolish to spend much | more energy to build a device to save energy, even if you | think it could be repurposed in the uncertain future. If | we're going to be conscious about our | (carbon/pollution/etc.) footprint in this planet, we have | to make rational decisions about our consumption. It | doesn't mean we can't have fun, we just have to waste less. | dwighttk wrote: | > Basically, if we want to transition to a carbon neutral | world, it is going to require a lot of people | investing/purchasing projects/goods that do not make sense | economically and might not initially be carbon neutral | after accounting for embodied energy. | | Large shifts like that don't occur from people wasting | money they have left over after entertaining themselves, | they occur because the new way is much cheaper and the old | way can't compete. | masklinn wrote: | > To be honest, although I realize it would be ridiculous, but | if inverters were small and cheap, I would personally prefer | having an exercise bike plugged into the grid. That way my | exercise energy would at least be useful to someone, somewhere. | | The only thing it would do is fuck up the grid. Grids are not | sewers, they don't work by having randos throw shit into it. | Human power is way too low and unreliable to be of any non- | hyperlocal use. | [deleted] | Johnny555 wrote: | As long as he uses a proper grid-tie inverter, there's no | reason the grid couldn't absorb his excess energy. It | wouldn't be cost effective for him, though. | rruark wrote: | While impractical and not cost effective, having a bunch of | bikes connected to the grid and randomly producing power | would have no more of an impact on the grid than flicking a | 60W light bulb on and off. | fluoridation wrote: | I'm surprised they even got it to boil. I would have expected | the heat to escape faster than it's added before reaching the | boiling point. That aside, 60 W * 3600 s = 216 kJ. With ideal | thermal insulation, that would be enough to boil about 600 ml | of water. If they only managed to boil enough for a single cup | (~300 ml), that's a rather inefficient setup they're using. | pitaj wrote: | Yeah I'd suspect slowly charging up a battery with the bike | generator and then quickly discharging the battery to boil | the water would be quite a bit more efficient. | KennyBlanken wrote: | Internal resistance of the battery would be a significant | problem, you'd need a fairly sizeable battery, and most | lithium ion cells have a maximum discharge rate of around | 1-5C unless they're high-discharge-rate cells which are | usually more expensive and lower capacity. | | Using a vacuum flask would dramatically lower heat loss. | dahfizz wrote: | The kettle used was vacuum insulated. | mardifoufs wrote: | Some cheap lipo cells can get you a sweet 60-120C | discharge rate with a pretty okay capacity. They are also | widely available on the used market, usually sourced from | EV batteries or energy storage packs. But yes, for the | typical 18650/cylindrical li-ion battery, this wouldn't | be especially feasible at all | dylan604 wrote: | If it takes an hour to charge the battery or an hour to | boil the water, it still takes an hour. Based on the | previous comment of generating 60W, how much battery | charging will that do? I'm really asking as I don't have | the info at hand to do the maths. I'm assuming choice of | battery comes into play. | foxyv wrote: | I think that what they are saying is, if we remove the | heat losses from the 1 hour boiling time and instead boil | it in a burst of 5 minutes using a battery you would need | significantly less energy overall. As a result, using a | battery instead of directly utilizing the bicycle's | electricity, would take significantly less time. | blacksmith_tb wrote: | There are commercially-available exercise bikes etc. that have | inverters built in[1], though they're marketed to gyms who want | to buy a fleet of them it looks like. I am skeptical it'd be | practical, but it might not be a terrible idea if you were | buying your first machine (and not replacing a perfectly good | existing one). | | 1: https://www.gosportsart.com/product/g516-indoor-cycle/ | wyager wrote: | > That way my exercise energy would at least be useful to | someone, somewhere | | What very few people (who haven't worked on grid modeling) | realize is that injecting energy into the grid from random | locations tends to make operating grids harder and more | expensive, rather than making it easier by reducing load. | | This applies to everything from bikes (which on balance won't | really make any detectable difference, and certainly won't ever | make an economically positive contribution vs the cost of | hooking them up) to home solar panels. Getting paid grid rates | to dump extra solar energy back into the grid is actually a | (very inefficient) subsidy benefitting solar panel owners. If | the grid charges you fixed 10c/kWh for power, and has to pay | you 10c/kWh when you dump solar surplus onto them, they're | almost certainly losing money on you, and it's probably making | the grid less efficient. | | Here's a good starting point if anyone is curious why grid- | dumping isn't socially efficient. Once you understand how | socially efficient power pricing works (e.g. LMP pricing), it's | pretty straightforward. https://www.eba- | net.org/assets/1/6/6._[Savitski][Final][165-... | dml2135 wrote: | Is less efficiency okay though if selling back to the grid | results in more clean energy overall? | vkou wrote: | Depends on what the trade-off is. | | If that efficiency would have gone to shareholders, sure. | | If that efficiency would have gone towards building | utility-scale renewables, no. | fluoridation wrote: | Not if the added inefficiency totally consumes the added | clean energy and needs further non-clean energy to sustain | it. You could end up in a situation where taking energy | from residential solar panels leads to burning more coal | than if you hadn't done anything. | mcronce wrote: | Or natural gas...which has disastrous methane emissions | all throughout the supply chain | yongjik wrote: | Your exercise is already useful to you (and those around you): | it keeps you healthier and reduces future medical cost expected | by the society. | | It sounds like a fun project, so I'm not arguing against that, | but I don't expect it to "help the Earth" in any meaningful | way. Considering the fossil fuel usage by modern agriculture | (and all the energy spent on delivering the food to our | mouths), the net climate impact of using "human energy" is | probably worse than an electric kettle. | TheSpiceIsLife wrote: | Inverters are tiny and cost almost nothing. | | Here's one for under $50 that will do what you want: | | https://www.ebay.com.au/itm/Car-Power-Inverter-12V-to-240V-A... | samatman wrote: | Generating a dirty sine wave which will power an appliance is | fine, but that's not the goal here. | | The goal is to generate a clean sine wave which will benefit | _the grid_ when applied to it. This is probably impossible at | bike workloads, and is in any case quite a bit more of a | problem than just throwing an inverter at a DC source and | calling it done. | rootusrootus wrote: | A grid-tie inverter will be quite a lot more expensive. | explorigin wrote: | 200W isn't a lot of power. Most microwaves are 1KW. You'll | need an inverter that can do that at least to run a fridge | constantly and a microwave periodically. | exDM69 wrote: | You can power a smartphone or a flashlight for a very long time | with the energy it takes to boil a liter of water. | | The latter is easy to do with firewood but charging batteries | is not. | WalterBright wrote: | Think of all the CO2 you'll be exhaling from your exercise. | hbarka wrote: | I know this is way off-topic but in Calum's YouTube video about | British Intelligence in Gibraltar he mentions a pedal-powered | generator which was the primary source of power for the agents | working deep inside the bunker. | | https://youtu.be/2n97nh9PKH4 | horsawlarway wrote: | Alright - this is mostly off topic, but I see this website pop up | here fairly frequently, and I really _really_ hate the battery | level indicator. | | I find it makes reading the actual content far more difficult | than it should be. | | I get that it's intentionally drawing attention to the fact that | this site is solar powered, but it pulls my eye to the line | literally every time I scroll. | | I end up closing the tab out without finishing the article - it | bothers me so much. | | Personally - I'd really love to have an option to hide it. I'm | completely down for showing it by default - but after a minute or | two on the site, the novelty has worn off and I'd really rather | focus on reading your content. | Doe22 wrote: | If you don't mind a manual step, remove the "solar." from the | URL to get the same article on the regular site. | [https://lowtechmagazine.com/2022/03/how-to-build-bike- | genera... in this case. | horsawlarway wrote: | Thanks! Didn't know that was an option and it helps a ton. | savingGrace wrote: | I had no clue what you were referencing. I'm using Brave, and I | have it automatically turn on the 'Speedreader' mode. When I | disabled it, I then saw what you are referencing. I know the | other browsers also have a mode that gets rid of all the junk | and lets you just read the articles. Maybe you should give that | a try? | marcodiego wrote: | For this and other cases, I use this extension: | https://alisdair.mcdiarmid.org/kill-sticky-headers/ | seanb wrote: | Drop the `solar` subdomain: | https://www.lowtechmagazine.com/2022/03/how-to-build-bike-ge... | horsawlarway wrote: | Awesome! Thank you - I didn't know I could do that. | calvinmorrison wrote: | One thing I think that could be changed here is a different | storage medium. For example, flywheel storage instead of | batteries, or compressed air storage, instead of batteries. Since | batteries can't be charged faster than a certain rate, it creates | a limitation. Of course, compressed air is only so useful and not | so efficient to turn into electricity but, still an idea. | barbazoo wrote: | > This website runs on a solar powered server located in | Barcelona, and will go off-line during longer periods of bad | weather. | | What a neat idea | mywacaday wrote: | I was wondering what the 84% floating batteryicon was about | until I scrolled back up | gwbas1c wrote: | FWIW: https://www.lowtechmagazine.com/2022/03/how-to-build-bike- | ge... is much easier to read. The current link is the version of | the site where the server runs off of solar power. | codazoda wrote: | I like the solar version better. :shrug: | aliswe wrote: | I wonder what the HN pundits say about the efficiency? (no | sarcasm intended) | jeffalyanak wrote: | I think they made the right choice in designing it around | providing an adjustable mechanical resistance. | | As it's primary goal is for working out and charging cell | phones I think it's best compared to a normal workout bike, | which outputs all of the energy as heat (and sound). | | Sure, the usable energy is minimal, but it's higher than zero | and it can meaningfully top up your smaller electronics | devices. | WJW wrote: | It's not very high, obviously: energy is conserved and humans | are not particularly efficient in converting food into energy. | It's also not very effective: the article itself mentions that | boiling the water for a single cup of tea took almost an hour | at 60 Watts. Imagine how long you'd need to pedal to power a | microwave with this, or a clothes dryer. Each of those would | need at least 10x more power, so you'd be looking at 10 hours | of pedaling for a single load of laundry. At that rate it's | quicker to just do away with electricity entirely and wash your | clothes by hand. | | It could be useful in an emergency situation where you have | more food than electricity though, or if you really really need | something small that can only work on electricity like a HAM | radio. | aliswe wrote: | I'm more into the lines of "how would this be improved with | least amount of effort and most value"? | WJW wrote: | Honestly as long as it remains human-powered I don't see a | lot of value to be gained. Humans just don't generate a lot | of raw power. | | The quickest way to improve this system would probably be | to attach it to a set of wind turbine blades or a | waterwheel, but "how to build a very poor wind turbine" is | not nearly as catchy as a blog post title. | toast0 wrote: | For a washing machine especially, the inefficiencies of | turning mechanical energy to electrical energy and then back | are going to be be pretty bad. If you could work out gearing | to spin the tub mechanically, it might be better, although | the back and forth motion of agitation isn't something I'd | know how to do. Pumping the water and spin dry should be | relatively simple, although getting enough speed for | effective spinning may be a challenge. | pitaj wrote: | > although the back and forth motion of agitation isn't | something I'd know how to do | | A smaller wheel linked to a larger wheel, where the smaller | wheel is driven by the bike. As the smaller wheel spins, | the linkage will move back and forth. If the second wheel | is sufficiently larger, it won't be rotated enough on the | push stroke for the pull stroke to complete a rotation, and | will oscillate instead. | | https://imgur.com/B1ykmpB | rolph wrote: | >>back and forth motion of agitation<< | | apply torque in bursts, let the inertia help you. | | start turning the drum and contents stay in place, while | drum turns, until contents match speed. | | then stop torque , so the drum slows suddenly and contents | continue to spin until they slow down. | | the drum doesnt change direction, only the direction of | momentum, and the mass transfering the force does | kube-system wrote: | This still assumes, however, the perspective that a | spinning tub is ideal. It's convenient when you're starting | with rotational motion, like with a motor. But if we're | looking for the most efficient way a human could power it, | I'd suspect moving the clothes across a washboard with a | static tub is way more efficient. It also has zero moving | parts, outside of the human itself. | masklinn wrote: | Mechanical washing machines were a thing before ww2. You | might be better off finding one in an old barn and | replacing whatever it uses (likely a crank) with a PTO you | can link to a bike. Adapting a modern washing machine would | likely be quite a bit more difficult. | throwaway81523 wrote: | The main reason I want a bike generator is to power my laptop, so | that if I'm going to be sucked into web browsing regardless, I'll | at least have to get some exercise in the process. | kitd wrote: | A rowing machine employs a wider range of muscles and so will | enable more power to be produced. Here's a DIY rowing generator | that one guy built: | | https://www.lybrary.com/a-rowing-machine-which-generates-ele... | | He claims 100W steady output but I'm sure more is possible. | | One advantage of the bike over a rower is you can be doing other | things at the same time, like reading a book, or tapping on a | phone or keyboard. On a rower ,only passive activities like | listening to music or watching a screen are realistically | possible. | KennyBlanken wrote: | Leg muscles are the largest and most powerful in the human body | and it's pretty easy for them to exhaust the body's aerobic | capacity. | | The number of muscles involved is not a limitation for longer | duration power generation. There's aerobic capacity, but also | glycogen and oxidative (fat) energy pathway efficiency. | Experienced endurance athletes usually have quite high | oxidative energy capacity/efficiency. | | These sorts of projects are silly because even a decent average | adult male will struggle to make 100-150W for an hour. | kitd wrote: | Leg muscles are the most powerful in he body, but they are | not used to the extent on a bike as they are on a rowing | machine. Additionally, they extend the work done by the arms | and back, ie the work is not just the sum of the individual | muscle movements, but the combined action. | | Yes, it is silly and the author intimates that in the OP and | the article I linked too, but I don't think meaningful power | generation is the point of the exercise. | | BTW a decent average male should be able to do 100W easily | for an hour. I'm a (not particularly powerful) rower in my | 50s and can easily sustain 150W for an hour, ie circa 120W | accounting for generator inefficiencies. | mcronce wrote: | You're absolutely right that projects like these are silly as | anything more than a fun tinkering exercise, but that | 100-150W number is a low estimate. I'm fairly small and out | of shape and can produce 180W for an hour. In-shape amateurs | can do better than that. | | Still not enough to be even remotely practical as a | generation method, but substantially more than 100-150W | thehappypm wrote: | One kiloWatt-hour of electricity costs around $.24 in my state. | If you can output 100 Watts for 1 hour, that's .1 kWH. Do it | every day for a year that's ~36 kWH, or about $10 in electricity. | TobySKT wrote: ___________________________________________________________________ (page generated 2022-03-07 23:00 UTC)