Pedal power

I found interesting information about using pedal power at this link. Thought a few here might find it interesting, as well.

http://www.lowtechmagazine.com/2011/05/pedal-powered-farms-and-factories.html



I had no idea one could plow a field by pedaling.

The pedal powered air compressor was an interesting thought. Seems like a way to store the energy for later use. But, I wonder if a large spring wouldn't be a better bet for storing that energy. I'm thinking of a powerful wind up spring, wound up with the bicycle and/or a windmill.

Also, a universal PTO hookup wound allow a multitude of appliances and tools to run off the same unit, whether that unit is the bicycle or a wound up spring. Blender, water pump, air compressor, food processor, grinder, drill, skillsaw---whatever.

Thinking of off grid uses, here. Or, for the day when energy from big providers becomes too expensive for most to afford.

How about a raised weight as a method of energy storage?
Man that cable plowing is very cool, I think I could rig that myself....

I built a hand wound permanent magnet alternator for a free exercise bike I acquired. One of the results of my experiments was the magic number 100 watts. That's about the max that a reasonably fit person could ever expect to produce for any length of time.

For people who are not at the high end of the fitness chart, the number was closer to 60 watts.

That's not a lot of heating power, regardless of the mechanism of converting the muscle energy into the heat energy.


Also, springs exhibit very low energy density compared to lead acid batteries, just as a rule of thumb/general idea. It takes a lot of spring to store 100 watt hours. Also note that spring steel is good/expensive alloy steel, so the cost per kilowatthour of storage will be expensive.


I purchased a BayGen radio b/c I liked the concept so much. THat's a radio where you wind a spring and that runs the radio for ~ 30 minutes. It was a big bulky box for essentially a tiny am/fm radio, just because of the spring. It cost over a hundred bucks, just because of the spring/engineering. Warnings all over the place to -NEVER- open the radio due to safety concerns about the spring.


None of this is to say that springs are not legitimate energy storage devices (hey, I bought one!), but just to give a data point of how well they function and what they might cost for a given application. One drawback is that they are generally not user serviceable. Even clock springs can be viciously dangerous to work on and are best left to the pros.


Here's a fascinating data point for gravity/mass storage of energy, the Gravity Light: https://www.youtube.com/watch?v=QX32yQgybaw

I helped fund their indigogo fundraiser. I have one of the first production models. It's cool! However, it takes 16+ pounds, raised 6 feet, to run a pretty feeble led for 20-30 minutes. I haven't measure it, but I would estimate it produces a watt or two. Again, this is not to denigrate the concept, but just to give a data point to see what's possible.


troy

Troy Rhodes wrote:I purchased a BayGen radio b/c I liked the concept so much. THat's a radio where you wind a spring and that runs the radio for ~ 30 minutes. It was a big bulky box for essentially a tiny am/fm radio, just because of the spring. It cost over a hundred bucks, just because of the spring/engineering. Warnings all over the place to -NEVER- open the radio due to safety concerns about the spring.

On the other hand I have an emergency radio with both a crank generator, and a small solar panel. It also runs for about 30 minutes after I wind it, or all day if in the sun. It contains a small battery and some capacitors. I think it cost about $40. Just another data point.

Thank You Kindly,
Topher

Topher Belknap wrote:

Here is some of the math. Average humans can generate about 1/10 of a horsepower. For your pedaling to make coffee example, a pound of water heated from 50°F to 200°F requires 150 BTUs, 1/10 of a horsepower is 4.3 BTUs per minute. So, heating your coffee water (perfectly efficiently) would require 35 minutes of pedaling. 1/10 of a horsepower is about 75 watts, that is equivalent to about 1 foot² of solar panels (during sunny times), that is about $60 worth of panels (plus BOS, so maybe twice that). Since we get about 4 sun-hours per day in my climate, a human's eight hour day is the equivalent of 2 foot² of solar panels, or 1/50th of a gallon of gasoline (per day), or 0.6 kWh per day (10 cents worth for me).

You assume a COP of one, yes? How about spinning a heavy flywheel to even out output and gearing it to run a heat pump compressor? Shouldn't it be possible to cut the time to less than half your estimate? Maybe use one side to cool a cold pack to take with my lunch and the other side to heat my coffee, both with less time than many people devote to a morning exercise routine and no need for grid power.

Connor Macreno wrote:

You assume a COP of one, yes? How about spinning a heavy flywheel to even out output and gearing it to run a heat pump compressor? Shouldn't it be possible to cut the time to less than half your estimate? Maybe use one side to cool a cold pack to take with my lunch and the other side to heat my coffee, both with less time than many people devote to a morning exercise routine and no need for grid power.

Yes. If you have seen a heat pump small enough to be hand cranked and produce a cup of heated water, I would be fascinated to see it. No need for the flywheel, compressors work fine with slight variations in input.

If we are going to try to avoid grid power at all costs, we should really calculate what that cost is. How much money, energy, pollution, etc. are caused by the food you need to eat to pedal the bike to make your coffee? US food production and distribution make electricity production and distribution look efficient.

Thank You Kindly,
Topher

Most people when pedaling produce more than slight variations in power. I think the creator of the pedal powered prime mover has a nice write up about the issue. Four efficient use with a heat pump, where changing pressure is also changing efficiency, I think the flywheel is a good idea, but I'll be glad to try it without and see how it turns out.

This doesn't have to be about off grid at any cost.
People doing bicycle randonneuring may already be carrying a percolator and a cooler, adding a compressor and a way the combined unit can be connected to the bike for power may be feasible.
Coffee and mini fridge with my bike? Yes please.

I haven't seen a heat pump on this scale, but there's no reason it can't work. I've seen mini air compressors used with vortex tubes that boil water and are the appropriate size, but the COP would be low. I'm now really thinking I need to build this.

Just remembered PC phase change cooling systems. Trying my search again...

Connor Macreno wrote:I'm now really thinking I need to build this.

Let us know how it works out.

Thank You Kindly,
Topher

Any idea where I can buy a cheap compressor out scavenge one that would be suitable?

Connor Macreno wrote:Any idea where I can buy a cheap compressor out scavenge one that would be suitable?

Dehumidifer or dorm fridge would be where I would start looking. Or rather not, since I am not confident about securing the chemicals they use in them, which should NOT be released.

Thank You Kindly,
Topher

Even ignoring the issue of how to empty the system, don't those normally have the drive motor and compressor in one housing?

I think pedal power has a lot of potential. Engineering tweaks that we haven't thought of yet may astonish us. I have the hand crank radio too and I'd rather be pedaling than cranking. Imagine all the people driving fossil fuel vehicles to gyms where they use exercise machines that are plugged into the wall! Human muscle power may not pack the biggest punch, but lunch is a more renewable resource than coal or gasoline!

I'm glad you brought this topic up, Bill. I've been talking to an engineer friend about the possibilities of pedal power a lot recently. We have a couple of business schemes that could get the ball rolling, so to speak. I really appreciate brainstorming and a positive attitude of innovation.

Here's an example of perfectly appropriate use of pedal power.

The guy who owns this rides it to the market every week, carries his groceries home on it, sharpens the knives for the locals and earns himself a bit of money.

What's not to love?

I remember watching an episode of Shark Tank where the guy was doing a bike powered smoothie shop. The sharks hated it of course, but I thought that there was a lot of potential there for a marketable product in the form of an exercise bike with multiple attachments. A blender, a food processor, a grinder/mill, etc. If I had the funds to put down on components, I think it would be a great project with potential to really explode in a niche market. They already make most of the attachments in 'hand powered' forms anyway and it wouldn't take a ton to modify them I would think.

Looks like the guy with the juice stand did a kickstarter as well.