It is estimated that half of the US would become obese by 2030. Fat has an energy density of about 50 times that of Lithium ion. Modern mobile computing devices are pushing the limits of battery technology. So why not make use of fat as an energy source?
I actually built a prototype of a device that (indirectly) converts fat to electricity. (More accurately, the user converts their fat into mechanical energy which the device converts into electricity.) It easily supplies over 100W, enough for almost any mobile electronic device. Now all that's left to do is to find ways to downsize it for mobile use and find a way to deal with the varying output. Initially, I was thinking of supercapacitors, but maybe high current Lithium ion would also work?
Graynomad:
It's called an exercise bike with a dynamo
...
So what is this gadget?
It's actually an exercise bicycle with a permanent magnet alternator. And a DC/DC converter to step up the voltage, a grid tie inverter, and control electronics. The grid tie inverter is of particular interest since it is a low cost design that would also be usable with other alternative energy sources.
As for why I'm working on it, I needed an interesting and useful project for senior design. I wanted something that had to do with power electronics, and I wanted something that helps the environment. The main contribution, however, is because my best friend Tiffany Yep is a model (and a digital communications engineer). After looking through some of her pictures, I wanted to be just as skinny as her.
Interesting post. BTW, there was a TV program I watched a while back on discovery/history talking about many models are (term for food-hating problem???) and live a degrading life pressured by public interest in a slim look. Don't do it! It's unhealthy to rip nutrient off your body to make certain parts look slim, which should be storing some healthy fats as backup batteries.
Oh, the project is only half the story of energy problem. You need efficient storage, and efficient charging/discharging methods. Batteries are good for slow discharge rates and charge rates while gas is good for fast rates. How are you going to charge fat? Going to a pig farm for more fat or having a fuel cell eat corn for a while and poop?!
As liudr says you probably need storage, however that adds a lot of expense and if you're in the grid maybe not.
If your inverter feeds back to the grid and your utility company pays for that I can see a good product here, an exercise bike that not only gets you fit but helps pay for itself.
Here in the US, fat is too renewable. I don't think there will be a way to use it all up, and even if that happened, it would only be a good thing. (The models would hope that doesn't happen, since that would cause being skinny to lose status.)
The inverter is too small (500W design rating) to completely supply every load in the average house. It does, however, offset the loads, which is the whole point. It is essentially using the grid as a battery with "unlimited" capacity and lifetime. The DC/DC converter can also be used by itself to power electronics independent of the grid, although the maximum load would be limited to about 35W or it goes unstable. It's also possible to use the alternator to charge a 12V battery, although MPPT would not be available and the efficiency would not be optimum.
I have a BMI of 27.5, which is really high for an Asian. I don't know any Asian who is fatter than me. In contrast, my best friend Tiffany Yep is very skinny by US standards but just about average by Asian standards: http://oi39.tinypic.com/s5xws5.jpg
Tiffany is not, however, the skinniest person I know - my friend Yiwei Cheng is even skinnier. (Sorry, I don't have a picture.)
It's funny (but sad) that despite stronger and stronger negative bias from the models, obesity in the US is in runaway. It somewhat resembles secondary breakdown in a bipolar transistor...
Ok so I mistook your project for a portable fat converter, which at some point will need fat to be reloaded. So it is more or less an exercise machine that convert fat grown on humans into electricity. A healthy human can probably output at least 75W of power if not hundreds in bursts. Good thing you are thinking for the overweight population. You could be the first benefector. On the longer time scale, hour or longer, the human outputs only at a small power rating though. Maybe rig a health club to see how much energy bill they can save doing that. Will be a nice case study and may convence others to join the effort.
Judging by that photo I'd say your friend is "healthily slim", only skinny in the context of the average western bloat.
Yep, offsetting loads is all you need to do. When you consider most exercise bikes lose all the energy in friction or moving air around I reckon one that you plug in but that has the power running the opposite way is a great idea. At 35W it won't exactly solve the energy crisis but it makes the bike a producer not a consumer.
That 35W figure is if you're directly running an electronic device. Ordinary switching power supplies approximate constant power loads, which are inherently unstable if they are large compared to the source. The inverter is designed to not exhibit that problem, so it easily puts over 100W into the grid. (The inverter itself has instability problems of its own, which I'm working to fix.)
I have some doubts that this will pay of. However I always wonder why exercise machines need a power supply. For braking? For their computers? I think it would be a very reasonable idea to use a small generator to make exercise machines self powered. This would get rid of the power cords and make them more "portable".
Anyway their brakes will convert the power to heat which (at least in winter and/or in cold regions) will help to lower the heating bill slightly.
liudr:
Ok so I mistook your project for a portable fat converter, which at some point will need fat to be reloaded. So it is more or less an exercise machine that convert fat grown on humans into electricity. A healthy human can probably output at least 75W of power if not hundreds in bursts. Good thing you are thinking for the overweight population. You could be the first benefector. On the longer time scale, hour or longer, the human outputs only at a small power rating though. Maybe rig a health club to see how much energy bill they can save doing that. Will be a nice case study and may convence others to join the effort.
I've seriously thought about that in the past, never got as far as NIHao has though
I've been told that an average person about 150 lbs generates about 100W in heat just living. That can be checked, how much energy in a 2000 kilocalorie (the real term but people say calorie) a day diet?
Same person on high fiber generates like 50% even more heat.
The hard part would be tapping a useful % of that without killing the 'generator'.
The US Army did experiment with devices in boots that generated power for communications and like. The trouble is that the things reduced the performance of the troops wearing them. Find those boots!
