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Surprise, New Front Page poll Question
By wooferhound, Section Homebrewed Electricity Posted on Mon Nov 24, 2008 at 02:29:05 AM MST
Are You Connected to the Power Grid ?

I change the Front Page Poll question on the 21st of each month and it's a little late but the new poll is now available. The old front page poll was "What Type of batteries are you Charging?". The results can be seen here. If you haven't voted this question then you can do that here too.....
http://www.fieldlines.com/poll/1224590969_knnqrnvK
The New Poll Question is "Are you connected to the Power Grid?", The poll is not on this story page but is found on the lower righthand side of any of the main Front Pages, use your Back Button.
The poll section normally appears on the righthand side of the Main Page (not this page), at the bottom of the Info areas on that side. You must have "Polls" enabled to be able to see them. If you don't see the Polls section then enable them this way...
On the right side of this page find the Menu Box with your Username on it.
Inside that box click the menu item for "Display Preferences"
At the bottom of that page is a listing for "Boxes"
Make sure the "Poll" box is Checked
The front page Poll will now display on all your Main pages.
Save your new Settings.
Helpful Tip:
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"Number of story summaries to show" to 50
"Number of story titles to show" also to 50
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Surprise, New Front Page poll Question | 10 comments (10 topical)

Re: Surprise, New Front Page poll Question (3.00 / 0) (#1)
by Nothing40 on Mon Nov 24, 2008 at 05:45:20 PM MST

Well,I only have ~10W of solar,so not all of my power is from the grid,but like 99.99% of it is. :-(
I have been a bit better about conservation though!

Re: Surprise, New Front Page poll Question (3.00 / 0) (#2)
by richhagen on Tue Nov 25, 2008 at 02:14:11 PM MST

Ha, I just switched out my nearly murdered 48V bank for a new type of storage. It is very small at the moment, more of a buffer than a storage bank, but I have 27 Farads at 64 Volts of Capacitor storage. It will increase to 110F shortly, and I have been running it between 60 and 32 Volts. Currently it's only about 9.7 Watt Hours of useable storage, soon to be about 40 Watt Hours of useable storage, or half of the storage capacity of a reasonable laptop computer battery, although it can cycle rapidly and repeatedly with little detriment. It is more of a buffer at the moment, however there is no other storage connected now. It just doesn't quite fit any of the categories in the poll though. Rich
'A Joule saved is a Joule made'

Re: Surprise, New Front Page poll Question (3.00 / 0) (#3)
by Ungrounded Lightning Rod on Tue Nov 25, 2008 at 03:28:23 PM MST

I have 27 Farads at 64 Volts of Capacitor storage. It will increase to 110F shortly, and I have been running it between 60 and 32 Volts. Currently it's only about 9.7 Watt Hours of useable storage, soon to be about 40 Watt Hours of useable storage

I get forty watt MINUTES, not watt HOURS.

[ Parent ]

Re: Surprise, New Front Page poll Question (3.00 / 0) (#6)
by richhagen on Fri Nov 28, 2008 at 02:39:43 PM MST

UGL, begging your pardon for disagreeing with you, as usually it is you who are catching my errors, but I believe you have made an error. Having played around with these capacitors a bit, I have the units and figures down pretty well.

The energy stored in a Capacitor is equal to one half of the capacitance multiplied by the square of the voltage to which it is charged.

In SI units, A Farad is defined as a (A^2*s^4)(kg*m^2)

The energy difference between two voltage states is equal to one half of the capacitance multiplied by the difference between the square of the starting voltage and the square of the ending voltage.

For 27 Farads of capacitance starting at 60 Volts and ending at 32 Volts this would be .5*27*(60^2-32^2) = 34776 A^2*s^4*V^2(kg*m^2)
For this, Volt*Amps are Watts, and Watts * seconds = Joules
A Joule is a Kg*m^2/s^2, so the inverse would be a s^2/(kg*m^2)
Since Joules squared / Joule simplifies to Joules, our answer is simplified to 34776 Joules.

One Watt is equal to one Joule per second, so if we were to expend this energy in one minute we would have 579.6 Watts in one minute, or 576 Wattminutes. If we expended it in one hour, we would have 34776 Joules divided by 3600 Seconds, or 9.66 Watts for one hour, or 9.66 Watthours.

This matches fairly well empirically since it takes about 24 Seconds to discharge between these voltages through a 1300 Watt rated heater off of my inverter. (24 seconds*1300 Watts = 32500 Joules) given a bit of inverter loss.

Repeating the math for the larger bank gives the 40 Watthour figure.

Basically, I am looking to use it as a buffer combined with some other form of storage which can be applied in my urban environment. Rich
'A Joule saved is a Joule made'
[ Parent ]

Re: Surprise, New Front Page poll Question (3.00 / 0) (#7)
by richhagen on Fri Nov 28, 2008 at 02:44:58 PM MST

In the line above, my slash either disappeared or was never put in

the line: In SI units, A Farad is defined as a (A^2*s^4)(kg*m^2)
should read: In SI units, A Farad is defined as a (A^2*s^4)/(kg*m^2)

Rich
'A Joule saved is a Joule made'
[ Parent ]

Re: Surprise, New Front Page poll Question (3.00 / 0) (#8)
by richhagen on Fri Nov 28, 2008 at 02:47:42 PM MST

the line: would be .5*27*(60^2-32^2) = 34776 A^2*s^4*V^2(kg*m^2)
should be: would be .5*27*(60^2-32^2) = 34776 A^2*s^4*V^2/(kg*m^2)
for the same reason. Rich
'A Joule saved is a Joule made'
[ Parent ]

Re: Surprise, New Front Page poll Question (3.00 / 0) (#9)
by Ungrounded Lightning Rod on Sat Nov 29, 2008 at 04:13:44 PM MST

You're right. I get 9.66 Watthours for the 27 farad and about 39.4 for the 110.

I did it a slightly different way and slipped by missing one of the multiplications by the voltage (once for the number of amp-seconds to come to charge, again for volts * amps). That put it off by a factor near 60, so I thought you'd forgotten one of the two divide-by-60s going from seconds to minutes to hours. B-(

How I did it:

Farad is an amp second per volt.
Charging/discharging at a constant current ramps the voltage linearly between zero and full, so your voltage term is multiplied by 1/2 (area of the triangle versus the rectangle).

So watt-seconds to get from zero to a particular charge is amp-seconds to charge it times final voltage over 2. But amp-seconds to charge is volts times capacitance. (I think that's the volt term I missed.) So watt-seconds is volts squared times farads over 2. Of course since it's non-linear you need to take the difference in stored charge at the low and high voltage to get the usable storage.

= = = =

Back when I was a kid they still though realizing a farad would be impossible. I remember the ad for a major breakthrough in cap manufacture: A farad you could hold in your hand. Picture of a hand holding two half-farad, 1.5V electrolytics, each the size of a soup can.

Of course we've come a way since that - with people using many-farad caps to level the power for their automotive bass loudspeakers. But is that progress or regress? (Guess it's like weapons, fire, and atomic energy - whether it's good or evil depends entirely on how it's used. B-) )

[ Parent ]

Re: Surprise, New Front Page poll Question (3.00 / 0) (#4)
by ruddycrazy on Wed Nov 26, 2008 at 04:56:02 PM MST

Well next xmas day is 5 years off the grid here on the farm and loving it...

Re: Surprise, New Front Page poll Question (3.00 / 0) (#5)
by MattB on Wed Nov 26, 2008 at 08:13:40 PM MST

Good poll... but, as of now, 21% says no grid, 100% RE Power...

I wonder how many of them folks have backup generators that use... non-RE fuel. You can count me in as one.

Cheers!

Re: Surprise, New Front Page poll Question (3.00 / 0) (#10)
by twombo on Mon Dec 01, 2008 at 03:29:12 PM MST

Matt

I finally got my little diesel on Bio. Problem is, I use it so infrequently (and it uses so little) that I 'm a little concerned about the bio going bad. Last January I used it and it used a quart of fuel then.

Now to kick the propane habit (Refrigeration and back up to passive solar water heater).

Mike

[ Parent ]

Surprise, New Front Page poll Question | 10 comments (10 topical)

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