# Potential Energy

Discussion in 'Misc Electronics' started by Jasen Betts, Jun 5, 2009.

1. ### Jasen BettsGuest

an escalator driving a generator ?

2. ### karelaGuest

When we go upstairs we spend a lot of energy that gets stored as potential
energy. When we go downstairs we waste all the potential energy. Couldn't
anyone invent a good way of coming down so the potential energy could be
converted to other forms of energy that could be converted to electricity
when needed??

3. ### Doc O'LearyGuest

How much are you willing to spend on a contraption to power a 100W light
bulb for less than 1 minute?

<http://www23.wolframalpha.com/input/?i=potential+energy+of+100kg+at+5m>
<http://www23.wolframalpha.com/input/?i=100W+*+1+minute>

4. ### daestromGuest

Well in *theory*, yes you certainly could. Something as simple as a bucket
and rope tied to a pulley turning a shaft. When you want to go downstairs
you just climb into the bucket and let it lower you through a hole in the
floor. Of course there will be *some* losses.

But lets look at just how much energy we're talking about. Raising a 200
lbm man up 10 feet in normal gravity would put 2000 ft-lbf of energy into
the man. If you could recover *all* of that, that is a mere 0.75 watt-hours
(not kW-hr, just watt-hour). So if he goes up the stairs 20 times a day for
a year, he'll have used 20*365*.75 / 1000 = 5.5 kW-hr of energy. Recover
*all* of that perfectly and you have about \$1 worth of electricity for the
year.

Going up stairs 20 times a day is great exercise, but it won't generate much
energy for you.

daestrom

5. ### CharlesGuest

Jump onto a platform with pulleys and counter-weights. The resulting
rotational energy can be stored in a battery via a rotating generator. The
overall efficiency will be less than 15%. The time to pay of your
investment (for all of the pulleys, and gears, and a safe platform, and the
rotating generator with a storage battery) will be infinity years.

6. ### Don StaufferGuest

I worked on a program for defense dept. The idea was to keep soldier's
battery packs charged (a modern infantryman carries a lot of battery
weight). One idea we looked at incorporated piezo-electric strips in
the sole of shoes. We didn't win the contract.

Modern magnetic design software is extremely good, and is allowing very
efficient small generators to be designed these days. Notice the
profusion of wind-up flashlights. If wearable computers ever make it to
mass production something like that will likely appear to keep the
batteries for those computers charged- or at least extend the life.

7. ### RogerGibbGuest

Be sure to capture the energy from rain falling too. Especially
when it runs down the spout from your eavestrough.

8. ### Alistair GunnGuest

In alt.energy.homepower RogerGibb twisted the electrons to say:
One of the micro-hydro places near me has it's gutters set to dump the
water into the mill-race it's on. Okay, I'm never going to claim it (or
the micro hydro plant further down said mill-race) generates significant
amounts of power due to this but I do think it's an elegant simple piece
of design.

9. ### daestromGuest

So let's see, if you have a 45x28 roof, 20 ft up in the air and you get 4
inches a rain (quite a bit in most areas), and you manage 100% energy
recovery, that rainstorm would generate about 522480 ft-lbf of energy.

A whopping 197 watt-hours.

In my case, I wouldn't bother.

daestrom