How to build a bike generator with control panel
solar.lowtechmagazine.com
solar.lowtechmagazine.com
> 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.
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
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.
A watthour next to a hydroelectic powerplant has a very different value that a watthour in an off grid cabin during arctic winter.
Sometimes energy prices even go negative - it would be wonderful if these surpluses could effectively be utilized to manufacture solar.
But if everyone on the planet started doing it, I might rethink my position.
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.
Too many people get hung up on the idea of pulling out the hook (the current carbon-positive processes that we use) and not about the ultimately least painful and most successful way of removing the hook (pushing forward with pressure to transition to carbon-negative systems even if in the in-between time that causes more carbon to be released into the atmosphere)
We would generate a ton of carbon to build and roll out an EV replacement for every ICE vehicle on the planet, not to mention the extraordinary expenses of generating enough electricity and charging plants for them.
If that were done in an amazing single year by military force or something, it would be the year of the most carbon production ever on the planet.
But the centuries afterwards with the extraordinary reduction in Carbon Dioxides and Monoxides and other exhaust gasses would be worth it, right?
That's the plan, work over time, get better every day, little by little, don't worry about perfection, focus on drawing closer to good enough.
Biking super hard for 16 hours a day for an entire year would produce $29 of electricity (assuming 100% efficiency in the generator and electronics).
And from an environmental standpoint, it would be better to idle on your couch while you burn the food you'd consume in an ICE.
Even if you did, the energy going into the bike isn't usually green. It's very, very far removed from the sun, especially if you eat lots of beef. Even if you don't, lots of gas was spent to get your food to your mouth, so you'd be much better off just not wasting the calories.
If you were planning on exercising, any energy you feed back is completely "free," regardless of your food source (minus the embodied energy of the equipment you hook up, as above).
Fit people need to eat more. Muscle takes calories to maintain. You can't maintain muscles without exercise. Your body expects that you're running down prey on a periodic basis. If you don't meet those expectations not everything will work as it should.
Using a vacuum flask would dramatically lower heat loss.
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-...
If that efficiency would have gone to shareholders, sure.
If that efficiency would have gone towards building utility-scale renewables, no.
The latter is easy to do with firewood but charging batteries is not.
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.
You could literally pedal bitcoins. ;)
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.
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...
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.
"would personally prefer having an exercise bike plugged into the TV..."
When I replied to it.
However, I have no proof and am often wrong.
I am imagining a 1kW sprint run by Uni students for microwaved ramen noodles!
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.
I too found the charge level indicator too distracting to be able to read the article as-is.
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.)
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.
Instead, would it make sense to have a heavy flywheel, a fixie gear, and a way to slowly ramp up the power draw, so the power draw itself is the "gear" that allows you to go from a hard-to-start heavy wheel to a smoothly-running wheel?
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
Yeah, direct drive trainers vs wheel-on trainers have the advantage of not ruining a tire or requiring a trainer specific tire.
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.
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.
Still not enough to be even remotely practical as a generation method, but substantially more than 100-150W
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.
What a neat idea
A track cyclist can reach 2000+W bursts, but they are freaks.
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.
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.
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.
the hardest part would perhaps be to reenact the water cycle?
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
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.
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.