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Old 03-04-10, 10:20 AM   #11
Lex Parsimoniae
 
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I would love to have 2.5 KW of PV (don't have the room for 2500 KW)..

I've also been looking at the idea of a ground mounted array of cheaper PV
for driving plain old resistive heating coils in my heating boiler.
See: http://ecorenovator.org/forum/solar-...eat-water.html

I think a few of these Kaneka Thin Film Solar Panel 110w
big fat Heavy boys might be in my price range.
(I could get 3 shipped for less than $700 and get 90 more watts).
330 watts is about 1126 BTU.. Not too shabby. Might save me some oil.

So far, I have not been able to locate the voltage specs on these new panels..

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Old 03-04-10, 10:44 AM   #12
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The PV is something I would do in increments. Bite the bullet and get the gridtie inverter I want, start with 2-4 PV panels, and a relatively small battery bank. Add panels as the budget permits. I'm thinking eventually two dual-axis trackers with ten panels each. At some point replace the battery bank with something larger and sell the first set of batteries to someone else who wants to build a small PV system. It'll take several years to complete, I'm sure.

Back to the solar water project: We currently have an ancient propane furnace in the house. The house is pretty well insulated, but some drafty windows need to be address. It's downright scary how much propane we've gone through this winter. As in, $10/day during a particularly cold week. My goal is to have the propane company take their tank away by the end of the year.

Not to get too off topic, but I've been following the The Homemade Heat Pump Manifesto thread started by AC_Hacker. (I can't link to it because I only have three posts so far - heh.) This is also something I want to try, tying one or two smallish AC units into a ground source heat loop for supplemental heat. If it works well I'd do a couple more for my detached shop.

Too. Many. Projects.
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Old 03-04-10, 10:45 AM   #13
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Default Peak Power and Average Power...

Quote:
Originally Posted by Xringer View Post
330 watts is about 1126 BTU.. Not too shabby.
Don't forget that the 330 watts is absolute maximum output, in peak sunshine. Most solar designers count on six hours of sun on a good day.


As you progress with the project, might want to see if you can scare up some real life performance examples.

Regards,

-AC_Hacker
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Old 03-04-10, 11:02 AM   #14
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Are you kidding me? This winter has sure shown me how unreliable the sun can be!
There is no way I'm counting on getting every watt that 'could' come my way.

My solar deck lamp has been giving me a very good indication of how unreliable PV would have been this winter..

However, if my boiler can be cheaply PV heated enough to over come it's heat loss,
I would be a very happy camper during the summer time..
(Well, maybe if it's not a repeat of last summer. Which was way too short).


The government thinks it can be done at $2 per watt PV prices..
BFRL: Solar Photovoltaic Hot Water System
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Old 03-04-10, 04:10 PM   #15
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Quote:
Originally Posted by jeffharbert View Post
The PV is something I would do in increments. Bite the bullet and get the gridtie inverter I want, start with 2-4 PV panels, and a relatively small battery bank. Add panels as the budget permits. I'm thinking eventually two dual-axis trackers with ten panels each. At some point replace the battery bank with something larger and sell the first set of batteries to someone else who wants to build a small PV system. It'll take several years to complete, I'm sure.

Too. Many. Projects.
I know what you mean by too many..

Anyhow, if you are going to be doing the slow incremental PV thing,
those panels that I'm looking at 120w solar panel, solar module 120w
have Vmp: 17.6V and are more suited to the type of 12V chargers that I already have.
And not so suitable for something like an EnPhase grid-tie inverter.

IMHO, the EnPhase units seem like the very best way for someone
to start off with a small system and built it up incrementally.

If you have not looked at Enphase, you should. They rock for small and large systems.
They are useful in the smallest (1 panel) to very large scale arrays.
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Old 03-06-10, 04:04 PM   #16
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Default Solar charger is working!

I didn't have very good luck with getting the mount to track today.
After replacing the old Actuator with the new one, installing the
little PV panel and the Tracker sensor, some high thin wispy clouds rolled in!

I manually pointed the mount at the sun and connected the power to the Tracker PCB.
The clouds cleared for a minute an the tracker locked on! It followed the sun!
After 10 seconds, the motor shut down.. A minute later, the clouds came back!

The hazy sun was charging the battery and keeping me toasty warm,
but the tracker didn't like the clouds!! It stayed like that all day!!

I think it's time to start hacking..





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Old 03-06-10, 06:20 PM   #17
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Wooo, very nice.

What is the next step?
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Old 03-06-10, 08:15 PM   #18
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There is a 9.1k resistor in series with a 100K that forms the reference voltage for the
East and West comparators. The ref voltage is about 1.18v when using 13.7Vcc.

The manual says that 9.1k can be replaced with a 10k pot (10 turn).
I don't have a 10 turn, but I did find a 13k trim pot that I will install tomorrow.

During bench testing, the only way I could get the test motor
to switch rotational direction, was to aim the sensor unit at the VERY bright sunlight.
I was actually it holding outside the window (on a cold day) just to get it working right.


One thing that's worrisome right now, it's pitch black out there and the tracker is just sitting dead.
It didn't return to the home posistion (max east).
During testing today, I put a black cover over the sensors and it just sat.
So, I think maybe something else might be wrong.
Last month, Blocking all light worked okay on the bench. The test motor took off for east.

The reference voltage might be the key, since today both the E & W
relays were energized (by the E & W comparators).
A close look at the circuit, shows when both relays are on, there is no juice to the motor..

If it's not the ref voltage, it can only be the IC (LM399)..

~~~

Anyways, when I get this thing tracking like it should, I plan to purchase some real PV for it.
Maybe a couple of 120 watt panels!

Last edited by Xringer; 03-07-10 at 05:43 PM.. Reason: typo on IC number
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Old 03-07-10, 05:12 PM   #19
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Default Sun Tracker is tracking with new battery.

Today was a good day. I installed a 20 turn pot and replaced the bad IC (LM339).
The outputs of two of the comparators were stuck at 5V. Should have been
zero or 12V, to drive the relay coils. The new chip (RadioShack) did the trick.

The mount is tracking the sun very nicely. The return-to-east even works.
(I put a black cover over the sensor pod).

So, tonight when the sun goes down, it will go back towards the East until it hits the end limit
(built into the actuator), so it will be already to go at sun rise.
(Note: It just got dark and the Tracker went to the East Home posistion)!

I'm pretty sure the East relay is going to be on all night.
Draining my battery and overheating the LM339?
I guess we will find out in a few days, if it can keep functioning.

Instead of an old SUV battery, I was wondering if a smaller battery
could be used for the actuator motor.?. So, would a small 12V at 7.2AH work?

This afternoon, I watched the charger LEDs and when the mount was moving normally,
the green 'Charged' LED would light, but after I did some test runs of the motor,
the yellow 'Charging' LED would come on for about 10-20 minutes and before it was back to 'Charged' again.

This is the nice little battery I found. It was marked for change in 2008,
but was taken out of service in late 2009.
It may have been over-charged by a wall-wart. It had been disconnected
for about 4 months and still had 13 volts showing..
Hope it has to kahunas to move an array reliable, because it fits inside the waterproof box, very nicely.

It's a valve regulated lead acid battery, and here's my question,
is it okay to run this battery on it's side? (Standing on one end actually).



On top of the battery is the 3A fuse and main cut-off switch, wired to the red (+) battery clip.
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Old 03-08-10, 10:28 AM   #20
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Default Accurate tracking!

I could not use the sensor pod shadow to gauge how well the tracker was working this morning,
it wasn't manufactured symmetrically, it's off-set up and to the right of it's base.

So I installed an 11" threaded 1/4" rod in the center, so I could see the shadow it cast.



As you can see, it's shadow is about 0.25" long. So far, that's as long as it ever gets.
The mount seems to be moving about every 80 seconds.
The motor hums for about 1 second and stops.





Hey! 86,400 seconds per day / 360 degs =240 seconds passing during each degree of rotation?
240 / 80 sec = 3.. Does that mean I'm seeing 1/3 of a degree accuracy ?

That can't be right!
I hope that isn't going to be too hard on the West relay!

The Charger is keeping the new battery right up there.
That little 5-10 watt panel is working very well.
I'm thinking of hooking another charger (I have 2 spares) on to those PV
lines, to keep the old SUV battery up to par..

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