power directly off of Panels?

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Posted by Thomas Allen Schmidt on July 18, 2008, 06:29:35 AM

Re: power directly off of Panels? (Reply #10)

What an amazing coincidence.
http://medievalwriting.50megs.com/scripts/letters/historyj.htm

I have got to say it if nobody else will.
"an attractive price of $5.00 a watt."
Are you sure you feel ok J.B.? Do you want me to call you a doctor or something? I am kidding, of course.
I know of a place selling PV at $7.00 a watt. Now they make $5 seem attractive. $5 would seem to be the going rate.
The PV industry could do better, you know?
I was thinking maybe, more like, $2 or $3 per watt.

(How about it PV manufactures? Don't you want to gives us "end users" a break for a change? Maybe instead of using both your hands to "rake" in your profits you could use just one for a while? Your arms must be getting tired by now.

Oh! I forgot. Thats not how the world works, is it? I mean, its always been the "end user" that suffers the burden of industry. In more ways than one. Why should RE be any different? Just following the trail left by those before you and all that sort of stuff hey?)

J.J., did you know that your human body uses 2 metals; Sodium (Na) and Potassium (K) along with body fluids which is mostly water (H2O) to produce bioelectricity for, among other things, your brains thought processes?
http://www.medicinenet.com/electrolytes/article.htm

Do you really need your computer? Oh sure, a computer can perform a lot faster but... Wait a second, has the company given you deadlines to meet or something? Have to make production do we? Well your not alone.

There are lyrics in a song I heard. A sort of prayer. I will not soon forget them. "I can see the concrete, slowly creeping, Lord take me and mine before that comes" (sung by the late Ronnie Van Zant)
Pity about Earth.

Posted by John D on July 18, 2008, 09:28:56 AM

Re: power directly off of Panels? (Reply #11)

James,

John B has done a good job in answering your question. Others have provided you with some good design and system hardware information. I would just like to add that using power directly from the solar panels to power a load is much more efficient than storing and retrieving it with batteries. So, IMHO, you should make sure that you have enough PV to fully power the load, with enough left over to fully charge your battery each day. Considering your smallish load, you're not going to be spending that much on batteries anyway. Personally, I would start with one 80 to 100ah battery, see how the system performs for a month or two, and add another battery if necessary. But hey, that's just me.

Thomas,

Yes solar panels are expensive, but once you've bought and installed them they should last for 25 years or more. I prefer to build my system now, rather than to wait and hope for a price reduction. With this crazy run-up in gasoline prices, you just never know what will happen in the future. I don't want to be in a situation where PV panels are in such great demand that they're hard to get at any price. People sometimes talk about the payback of solar PV, which IMHO is absurd. In addition to cutting your costs for electricity, putting up PV gives you protection from grid power outages. It can prevent your food from spoiling, protect your property, keep your communications working, etc. It's hard to put a price on those things.

Sure, I wish the cost of solar panels would go down, but I won't let their high cost prevent me from achieving my goals.

Posted by James Johnson on July 20, 2008, 05:45:21 PM

Re: power directly off of Panels? (Reply #12)

Quote from: John Dalhaus on July 18, 2008, 09:28:56 AM

James,
I would just like to add that using power directly from the solar panels to power a load is much more efficient than storing and retrieving it with batteries. Personally, I would start with one 80 to 100ah battery...

John D - you hit the nail on the head here..my idea is to be as efficient as possible hence the DC powered studio..good ot know I'm on the right track. As for battery size..again I think you nailed it..I'll get an 100ah battery and see how the system does..more than likely I'll get a battery monitor as well that handles multiple shunts, so I can monitor the pv array coming in and the battery power coming out..

John B - you're explanation below seems to spell it out perfectly for me..which is what I thought all along...

"...So if you have a pv panel capable of delivering 7 amps (84 watts for easy math) at 12v, and say your fully-charged battery requires 1 amp to maintain the float, then your 40 watt load would be drawing its 3.3 amps directly from the charge controller. The charge controller would also be delivering 1 amp to maintain the float voltage, so it will effectively be "de-rating" your 84w panel down to about 50w.

Now if you add a second 40w load, the charge controller would turn the panel power back up to 72w and service both loads while still maintaining the 1 amp battery float current. Add a third 40w load and suddenly you are drawing more current than the pv panel can deliver so you start taking current out of the battery....."

If the battery only needs 1amp to maintain float and the array is generating much more than the 1amp..the excess power will then be available for my DC use until I run over the array's amp output, which will then switch over to battery power. Needless to say, I'm sure this will fluctuate a quite a bit during daylight hours as the sun dances in and out of the clouds. So the Gobal Solar Panels might very well be the best choice for optimum "averageing" amp performance during the day...thanks again everyone..I'll post some photos as the system goes together..

James

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power directly off of Panels?

Posted by Thomas Allen Schmidt on July 18, 2008, 06:29:35 AM

Posted by John D on July 18, 2008, 09:28:56 AM

Posted by James Johnson on July 20, 2008, 05:45:21 PM

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