[HN Gopher] How to build a bike generator with control panel
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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:
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(page generated 2022-03-07 23:00 UTC)