6 mo. ago • 98%

Exercise bike that can store 2KWh of electricity

mastodon.social Chris Adams (@mrchrisadams@mastodon.social)

Attached: 1 image This is an industrial designed exercise bike from Lithuania that can store 2KWh of electricity generated by your own exercise. The electricity can then be used for loads of stuff - it has a bunch of DC outputs, like USB-C (up to 60W) and USB-A, and AC outputs (can output up to 2K...

This is an industrial designed exercise bike from Lithuania that can store 2KWh of electricity generated by your own exercise.

34 comments

TLDR: It's a great concept but it's about 100× more exhausting than you imagine.

I absolutely love stuff like this, and I also love cycling.

However, there is a big caveat here: I've been cycling for years and know my own power output:

Output -- Time Window -- Heart Rate

1400 W* | 60 seconds | 208 bpm

385 W | 20 minutes | 162 bpm

148 W | 6 hours | 110 bpm

*(yes, I know. My thighs are larger than some people's torsos and it scares me too)

That means that on average, around 13 and ½ hours of pedalling to charge this thing. (2 KWh is also worth $0.68¢ where I live at standard residential rates).

Humans are not great at converting their physical and thermal energy into kinetic or electrical (20-24% for most bodies).

Pedal power is amazing for things like charging phones or powering small devices and computers though, or for something completely meta: Charging up a eBike or electric scooter (120W), to then use without pedalling later.

Which then begs the question -- if our "human/person power output" is like 150 watts constant .. and the sun provides 1.4 kW/m² of energy -- why not just lay down a 150W photovoltaic solar panel ($89) in the sun and sip on some unsweetened iced tea instead?
76
- While what we can generate is negligible. If, for example you had these in all gyms, that's generating something. Not a lot, but more than nothing. Also all houses should have batteries and being able to remove the cost of a phone charge from what you suck from the grid would be nice.
  
  16
  
  Wasn't that the second episode of Black Mirror?
  
  17
  
  It's still unlikely to pencil out to do this given the opportunity cost of actually going through the effort of building, buying and connecting these things, to be honest.
  
  I'm fascinated by the idea but it's important to remain realistic.
  
  Here's a good article on the concept of bicycle generators: https://solar.lowtechmagazine.com/2022/03/how-to-build-a-practical-household-bike-generator/
  
  Personally, I think the best application of this concept is probably direct use of the mechanical energy, without converting the energy to electricity at all. See the bicimaquinas-concept: http://www.mayapedal.org/index.en
  
  One of the wonderful things about bicycles is how extraordinarily efficient they are - very little energy is required in relation to how much transportation work you get out of it. This works against us in the case of power generation, though - little power going in means little power going out.
  
  11
  
  It's a really good business idea that I've had more than once -- a self sustaining "green gym".
  
  Members would leave their electronic devices in special hardened lockers, plug them in, and then go to work out, and the power from central battery bank would then charge everything that's in the lockers.
  
  I also had an idea for credit system where the more power you generated the cheaper your monthly bill/subscription would be for the gym (only a few bucks here and there), or some kind of perks, like a free t-shirt once a year if you generated over 1 MWh (1000 kWh) or whatever.
  
  The power generated by such a place would probably be negligible but it would give people the same emotional high as other pro-social tasks.
  
  9
- 1400W for a minute is insane. You are either a pro track cyclist, or you should quit your job and become a pro track cyclist!
  
  9
  
  Haha, I wish -- they call it the hour record for a reason!
  
  I've got explosive short-term speed, but it doesn't last, and I get dropped within 20 minutes, as my power output dips below the optimized pros who can do 400W constantly for entire Tour stages.
  
  I appreciate the comment though!
  
  8
- If you look at the "about us" section on their site, I don't see anyone with human performance expertise (though who knows if any of them are hobby cyclists with a huge depth of knowledge). The seat and pedal design is definitely geared more towards aesthetics than performance, too. I probably wouldn't want to do more than a hundred watts on there.
  
  I definitely appreciate that the portability and aesthetic quality is a major design consideration for them, though. I see this more as a battery pack that you can pedal, than a bike that stores power.
  
  4
- Pedal power is **amazing** for things like charging phones or powering small devices and computers though, or for something completely meta: Charging up a eBike or electric scooter (120W), to then use without pedalling later.
  
  Skip that step and get a chainless digital drive bike. Same concept but you charge it as you ride.
  
  2
  
  With abysmal conversion efficiency
  
  4
3,442 Calories (14,388 kJ) is required to generate 2 kWh at a (generous) overall storage-work-storage efficiency of 50%.

For comparison, that is roughly:

one pound of body fat

a marathon

a full day of cycling
20
- Rule of thumb efficiency of humans is about 25%, which is about the kJ to Calorie conversion, too --- so 14kJ of energy output burns ~14,000 Calories.
  
  6
  
  True, I only included kJ equivalent because some countries use kJ on nutritional panels instead of Calories. Actual conversion rate of human energy stores to usable power is, at a guess, more like
  
  Calories * 0.25 * 0.6 * 0.8 - dt
  
  where t is time, d is the self-discharge rate of the battery, 0.6 is the efficiency of the generator, and 0.8 is the efficiency of the battery.
  
  So, user better eat their wheaties.
  
  3
Love things like this, but at 3.500€, that's a massive ask. Hopefully the concept catches on.

12
- 2kwH is worth about $0.18 here. I'd have to charge it ~19,500 times to offset the cost in electricity.
  
  11
  
  So only about 30 years of constant pedaling.
  
  8
  
  It's not about saving money. It's about using the energy that would otherwise not be used, and incentivizing exercise. If I could keep my phone charged from exercising, that would be cool. But yeah the price point is quite high.
  
  6
A fun toy. But a normal exercise bike already converts the energy to heat. This heat then warms up the apartment.

Of course, with electricity, a heat pump for heating or cooling could be used, which is more efficient. But it's not like the energy remains unused with a normal exercise bike, as long as it is cold outdoors.

6
- But sometimes it's hot outside 😓
  
  3
I always wondered why are they not generators as well. I mean, free electricity right there, however not much there is.

4
- Especially for gym owners
  
  3
They need to put these in all of the gyms in the cardio equipment. Just think of the power they could store.

4
I've been wanting this for years. But maybe not at that price.

3
- As it seems to double as a balcony solar inverter if you add some PV pannels the price seems to be not so bad. A 2KWh LiPO4 battery, charge-controller and inverter alone will cost you at least half of the asking price.
  
  6
  
  Maybe making a bike for half the price that can just plug into an existing inverter / battery would be more versatile then.
  
  6
  
  That definitely changed things a bit there.
  
  2
I'm pretty sure this was the premise of a Rick and Morty and a Black Mirror.

2
- Peace among worlds 🖕
  
  1

You've viewed 34 comments.