Backpack Generator.

**MisterSweetie** · 09-09-2005, 10:12

http://www.globetechnology.com/servl...ry/Technology/

By OMAR AKKAD Thursday, September 8, 2005 Updated at 2:01 PM EDT

Researchers at the University of Pennsylvania have invented a backpack that not only improves the way you walk, but also uses your movement to generate enough electricity to power several electronic devices at once.

In a paper published in the Sept. 9 issue of the journal Science, University of Pennsylvania biology professor Dr. Lawrence Rome and three colleagues describe the "Suspended-load Backpack," which can generate up to 7.4 watts of power. Typical cellphones, night-vision goggles and similar small electronic devices require less than one watt of power.

The electricity can be used as it is generated, or stored in a lightweight rechargeable battery.

The backpack takes advantage of the hip's movement to generate electricity. When a person walks, they place one foot on the ground and vault over it with the rest of their body. This movement causes the hip to move up and down about 4 to 7 centimetres.

The backpack's load plate is mounted to the pack and suspended by springs, which allows the load to echo the hip's movement. This drives a rack-and-pinion device, which in turn powers a motor that acts as a generator. The result is a conversion of the body's mechanical energy to electricity.

As an added benefit, rather than requiring additional energy on the part of the person walking, the backpack actually improves the way its wearer walks, making their movement more efficient, scientists found.

While Dr. Rome and his colleagues aren't yet certain why the backpack makes walking more efficient, they say the finding confirms the device is practical. They also found users can generate more electricity by walking faster, carrying a heavier load, or both.

The device could prove invaluable to explorers and scientists in remote regions, who would be able to shed the weight of extra batteries. U.S. soldiers stationed in Afghanistan, who must carry as much as 10 kilograms of extra batteries, may also end up using the backpack.

"Metabolically speaking, we've found this to be much cheaper than we anticipated," Dr. Rome said in a release. "The energy you exert could be offset by carrying an extra snack, which is nothing compared to the weight of extra batteries."
http://img80.imageshack.us/img80/495...ack20020tv.jpg

Neat, in any event.

**Rain Man** · 09-09-2005, 13:42

So, it's basically a backpack with shock absorbers, more or less?

Not for the ultra-lighter, but a nifty idea for everyone else.

However, might give a new meaning to night hiking! In the day, they all can be talking on cell phones and listening to boomboxes, and at night they can hike with spot and flood lights!!! LOL

Rain

Man

.

**Lanthar Mandragoran** · 09-09-2005, 14:13

many things non-light weight become so at some point

the thing that interests me (and i think it's more of a future for this) one sight mentioned this as a great thing for college or high-school students having to lug heavy text books around

**TankHiker** · 09-09-2005, 16:58

I just found another article on this:
http://news.yahoo.com/s/nm/20050909/tc_nm/backpack_dc

The good news is that you get 7 watts of electricity. The bad news is that you have to carry 85 pounds.

----------------------

WASHINGTON (Reuters) - A backpack that converts a plodding gait into electricity could soon be charging up mobile phones, navigation devices and even portable disc players, U.S.-based researchers said on Thursday.
Their backpack design converts mechanical energy from up-and-down movement of the backpack's cargo to electricity during normal walking.
Fueled by a snack, hikers can put the spring in their steps to good use, the researchers write in Friday's issue of the journal Science.

The backpack is deliberately designed to shake around a bit. The up-and-down movement of the backpack's cargo compartment against the frame of the pack turns a gear connected to a generator.

The simple magnetic coil generator is similar in principal to those seen in hand-cranked radios, flashlights that work after a rhythmic shaking and other devices.

Humping along just under 85 pounds (38 kg) of weight in the backpack can produce up to 7 watts of electricity, Lawrence Rome and colleagues at the University of Pennsylvania report.

This is more than enough electricity to simultaneously power an MP3 music player, a personal digital assistant, night vision goggles, a handheld global positioning satellite navigation device, and a mobile telephone.

The not-so-graceful human gait is a big help in making the pack work, they reported.

Human hips rise and fall about 2 inches with each step and a backpack worn by a person who is walking rises and falls as well, they said.

"As humans walk, they vault over their extended leg, causing the hip to rise 5 to 7 centimeters on each step. Since the backpack is connected to the hip, it too must be lifted 5-7 centimeters," Rome said in a statement.

"It is this vertical movement of the backpack that ultimately powers electricity generation."

But nothing is free, so what does this energy cost the hiker?

Little more than a snack, said Rome.

"Metabolically speaking, we've found this to be much cheaper than we anticipated. The energy you exert could be offset by carrying an extra snack, which is nothing compared to weight of extra batteries," Rome said.

"Pound for pound, food contains about 100-fold more energy than batteries."

**Freighttrain** · 09-09-2005, 18:03

HAHAHA and all it takes is a tiny little snack to power up to carry the 85lbs!!

hmmm 85lbs vs a few extra AA batteries

the colleagues at the University of Pennsylvania where it was developed need to take that 85 swinging pounds and go hiking over the Pa rocks... then tell me how great it is

i wonder what the dry weight is

**Panzer1** · 09-09-2005, 23:26

Let me get this straight. Are they saying that this device weights 85 pounds and can only generate 7 watts of power?

Panzer

**Granger** · 09-12-2005, 14:09

Originally Posted by Panzer1

Let me get this straight. Are they saying that this device weights 85 pounds and can only generate 7 watts of power?

Panzer

"Humping along just under 85 pounds (38 kg) of weight in the backpack can produce up to 7 watts of electricity, Lawrence Rome and colleagues at the University of Pennsylvania report."

Sounds like they are saying the amount of weight carried dictates the amount of energy produced. 85lbs = 7 watts

**Rain Man** · 09-12-2005, 21:36

I'm guessing y'all are mistaking the amount of weight the soldiers carry for the amount of weight necessary to produce the up and down motion.

My guess is an ultra-lighter would produced perhaps the same 7 watts. It's the natural 2" up and down motion of the hips, not the weight on them, that jiggles the generator shaft.

Rain

Man

.

**Frolicking Dinosaurs** · 09-13-2005, 08:22

I would think such a device could be used to trickle charge rechargable AA and AAA batteries making carrying extra batteries unnecessary for things like flashlights, headlamps, other items primarily used while not hiking unnecessary. (put them in the charger by day and the item by night) I would also think that using such a device as an alternative power source for items used during the hiking day would make batteries last much, much longer - meaning no extra batteries would need to be carried between resupplies for things like MP3 players that aren't necessary for survival.

Re the relationship between load and power generated - I'm betting an engineer could come up with an alternative placement for the generator that would increase the power output and /or make it independent of weight carried.

**Two Speed** · 09-13-2005, 15:32

Originally Posted by Frolicking Dinosaurs

. . . Re the relationship between load and power generated - I'm betting an engineer could come up with an alternative placement for the generator that would increase the power output and /or make it independent of weight carried.

Don't know about that. The power generated is going to be dependent on the weight moving over a distance. I suspect they may be able to tweak the efficiency via ergonomics, mechanics and the generator itself, but I'm pretty sure power output will be largely dependent on the distance (2") and the weight (85 lbs

).

The bad part is your message is giving me the worst itch to break out the ol' physics text and check that. Do any of my fellow enginerds on this site remember the relationship or formula?

(Enginerd: half engineer, half nerd. Most common type of engineer found in North America)

**Bob Baker** · 09-13-2005, 16:20

Anyone know how many watts are in a 9v battery or even a car battery? Im just curious to see how much you could power with 85 pounds of batteries.

**dougmeredith** · 09-13-2005, 20:03

Originally Posted by Bob Baker

Anyone know how many watts are in a 9v battery or even a car battery? Im just curious to see how much you could power with 85 pounds of batteries.

The power (in Watts) is calculated by multiplying the current by the voltage. So the power being supplied by the battery will vary with the load placed on it. There is a limit to how much instantaneous power a battery can provide. There is also a limit to how much total power a battery can provide over time (watt hours).

Also, they aren't saying that the pack would contain only batteries, so there would be less that 85 lbs of batteries.

So, to get back to your question (sort of), you would need to pick a weight for the batteries and calcualte the total number of watt-hours of capacity. You would then divide this number by the output of the generator, and this would tell you how much time you would get from the batteries. If this is more than required, the batteries win. If it is less, the generator wins.

Doug

**Two Speed** · 09-13-2005, 20:06

Originally Posted by dougmeredith

. . . If this is more than required, the batteries win. If it is less, the generator wins.

Somehow I'm having trouble viewing carrying 85 lbs as winning.

**HikerHobo** · 08-07-2006, 16:34

When walking, a person's hip moves up and down about two to three inches with each step. The movement occurs as the body vaults over each foot. Scientists were able to capture the energy of this up-and-down movement.

http://news.nationalgeographic.com/n..._backpack.html

**Time To Fly 97** · 08-07-2006, 16:54

I think they referred to the 85 pounds as an example of what the backpack could produce in watts (7.4 watts). If you hiked with 42 pounds, you would only generate 3.7 watts, etc. They say this is a small battery - probably not very heavy...but they don't say exactly how heavy the pack frame is...

I'm waiting for pack powered heated clothing!

TTF

**Just Jeff** · 08-07-2006, 16:57

Originally Posted by Time To Fly 97

I'm waiting for pack powered heated clothing!

Which would be great until it stops working in the field and you don't have a backup! Probably would be ok on most of the AT where bailout is pretty easy, though.

I'd use it to power my boombox/cell phone/disco light combo for shelter stays.

**blackbishop351** · 08-07-2006, 18:29

I can't remember where I saw it, but someone came up with a fluid system that did the same thing. Basically, there were fluid-filled tubes placed in strategic locations (in clothing, I think, not a pack). As you moved, the fluid was compressed and relaxed, and it drove a small turbine. I think they also figured out a way to have the fluid act as a cooling system, too.

**johnny quest** · 08-07-2006, 18:37

didnt the fremen in herbert's "dune" have special deep desert clothes that did roughly the same thing? muscle movement powered generators and such.

**RockyTrail** · 08-07-2006, 18:51

Originally Posted by Two Speed

Don't know about that. The power generated is going to be dependent on the weight moving over a distance. I suspect they may be able to tweak the efficiency via ergonomics, mechanics and the generator itself, but I'm pretty sure power output will be largely dependent on the distance (2") and the weight (85 lbs

).

The bad part is your message is giving me the worst itch to break out the ol' physics text and check that. Do any of my fellow enginerds on this site remember the relationship or formula?

(Enginerd: half engineer, half nerd. Most common type of engineer found in North America)

Ok, you asked...!!!!

The amount of energy generated in each step is the potential energy of the 85 lb pack dropping 2 inches. Converting to metric, 85lb=38.6kg and 2in=0.05meters. You also need to know the gravitational acceleration, which is a constant over most of the earth at approx 9.81 m/s^2.

Potential energy = mgh = 38.6*9.81*0.05 = 17.7 Joules.

The Joule is the unit of energy, but the power in watts is Joules per second, so if you took 1 step per second the watts generated would be

Watts = 17.7 Joules / 1 sec = 17.7 watts.

However, most generators are horribly inefficient, say only 40% or so of the mechanical energy gets converted to electricity (the rest is lost in heat).

So the net watts available would be

Watts = 17.7 watts * 0.40 = 7.1 watts.

So there you go....probably more than you wanted to know!

**blackbishop351** · 08-07-2006, 18:52

Nah, that was mostly for water purification and cooling. I'm looking around to see if I can find that link again...it's been a couple of years.

I could almost see the thing catching on for military application - used in an environment suit, for instance. But, like the one mentioned above, it's way too heavy for backpacking.

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