sun
wind
water
oil,coke
any other????

static? gravity (could be covered by water)

Geothermal
water covers hydroelectric, waves and tides, but these are doubling up - wind causes waves but winds are solar powered. Tides are gravitational.

I think it is possible to use temperature differences between surface and deeper layers of water in the ocean, but this doesn't sound like it would be very efficient due to the relativley small differences.

My favorite ... biological systems.

It is very easy, and at least 40 year old technology, to build a battery in which bacteria are put into one side and sugar (organic waste products) on the other.

But given the lack of organic waste on this planet it will never be utilized commercially. ;-)

BTW: Any reason why fission and fusion weren't on anyone's list? How about generators/alternators turned by other forms of energy? Even oxen?

I've got it. Lets take all of the prisoners from all countries and put them into squirrel cages connected to generators.

I assumed biological came from the sun.
As to lack of mention of nuclear options - maybe we have been infected by a political correctness virus.

As for fusion, it is not a yet a viable option (other than the big yellow one).

There is one simplistic battery producing electricity which may not be included in the above replies. I know some replies are very inclusive but I will mention it any way. While working on my Egypt book I was wondering why the Queens chamber when originally discovered had a covering of salt of the walls. That item and the fact the floor of the chamber is recessed about 2 feet below the entrance, and due to other facts, convinced me it was used as a salt battery for producing a low voltage they used.

www.exo.net/~pauld/summer_institute/ summer_day15current/saltwaterbattery.html - 5k -

There have been no other viable explanations.
jjw

jjw,
I got a 404 not found error when I cut and pasted the entire link, and when I clicked on the highlighted link I got a directory of pages. Can you be more specific as to which link you are referring to?

http://nanotechwire.com/news.asp?nid=6903&ntid=&pg=1

Piezoelectric generators may hold some promise given a little time. Piezoelectricity has been around for years but only for igniting pilot lights and cigarette lighters. And a fad sneaker with little LEDs on it. Other small gadgets that never flew made appearances as well.

The above article addresses small-current items up to personal electronics but I have seen some news about a sidewalk implementation where the pressure from foot steps could power street lamps. I've lost that link but it was fairly recent.

Even if it only works out for MP3 players and phones and such, the shear numbers could add up to a significant saving on coal smoke, spent batteries and nuclear waste.

That is certainly some light show. Thanks for sharing. :-)

http://gizmodo.com/5105052/pedestrian-power-will-generate-holiday-lights-at-shibuya-station-tokyo

We were told the other day that under our town is a huge reserve of Hot Rocks!! We were also given to understand that these 'rocks' could be used to generate elecricity. I have lived here for 40 years and in all that time we had never been made aware of this valuable asset under our feet. We were assured that 'they' knew all about it. In the meantime we have massive deposits of dirty brown coal nearby, masses of sunshine and a tiresomely apparent amount of constant wind. Guess which one generates our power?

Are 'hot rocks' geothermal by the way? Which is what I was going to say at the start before I got political!

Aren't there a lot of under utilised potential energy sources around though?

The hot rocks to which you refer are most likely heated by a geothermal process or system. It would be that system, rather than the rocks themselves, that would be the potential energy source. Depending on the characteristics of your system, geothermal can be rather easily and inexpensively tapped, even by individuals, to heat a home. Using dirty, brown coal when this resource is available would be a poor choice. It does, however, require some initial capitalization.

Under utilized sources? Everything that moves is capable of producing energy. What we lack is not sources of energy but, rather, sources of imagination and effort.

Buy a drill and some piping. :>)

One simple word - Friction.

I dont think anyone mentioned Static Electricity plus a few experiments on the subject.

I havent read about all of the stuff in the above link , but if you want Static Electricity you should use GLASS and SILK I think for the best charge...

maybe use a glass bottle and silk brushes that rub against the glass bottle.

or you could just use the CFPFM technology , but that would be too simple.

have fun !!!

..

You forgot geothermal and biological.

Nuclear.

If we learn to harness the Casimir force, we can add QM.

Also, biological spans a number of things:
1. crops as fuel
2. waste as fuel (human, etc)
3. mechanical harnessing of animals (or possibly plants)

I suppose this is included in mechanical harnessing of humans but I'm a big supporter of the Potenco pull - http://www.potenco.com/
They should open up their product line for a much wider variety of applications.

I've used portable crank powered radios.. why are we still using batteries for mp3 players when we could easily power them for hours with a little crank generator or a potenco pull?

because batteries are a product that must be bought hundreds of times durring the lifetime of the product.

and we are mindless product buyers.

in other words , the same exact reason that we dont use
wind and solar or even nuclear power on a massive scale , and why we dont even dream of using free energy to power the few products we can afford to buy after
we pay for our energy.

I tested one of the hand cranked radio - flashlight combos recently , I cranked it for 1 full minute , turned the light on and it lasted every bit of 10 seconds.

the light had about 7 led bulbs , so I just figured they didnt really want you to have a battery less light.

the radio lasted until I turned up the volume a little so that I could hear what was being said.

the unit had a compartment for batteries.