Author Topic: High Voltage vs Low Voltage with Classic 150 (Read 16464 times)

Frank S · « **Reply #33 on:** September 22, 2012, 08:20:11 AM »

Chris; I'm guessing that since you are so far north and you probably have your panels on a South facing roof that any form of tracking system would be of very little advantage or possibly even a disadvantage especially when show could be involved

ChrisOlson · « **Reply #34 on:** September 22, 2012, 08:44:37 AM »

I tested that once by manually adjusting a solar panel and comparing it to a fixed one. There was not enough difference to mess with any sort of tracker. It's cheaper and easier to install more panels instead - with the added benefit that while a tracker produces no more power on an overcast day, more panels does produce more power.
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Chris

Frank S · « **Reply #35 on:** September 22, 2012, 10:23:54 AM »

That was about what I was thinking
someone in a lower latitude may see more benefit and around the equator I could see where they would see quite a bit more

DamonHD · « **Reply #36 on:** September 22, 2012, 10:49:52 AM »

When you most want every Joule, in mid-winter, at least here in the UK, the arc of the sun through the day is so small as to negate the value of a tracker IMHO.

I'm firmly in the "just add more panels" camp, and let my MPPT ignore any excess in summer that it can't use (no magic smoke will get let out) and indeed leave the panels at a fairly steep ~70 degrees all the time. My latest panel is been put up vertical on a due-south-facing wall in fact.

I concentrate on capturing *enough* energy mid-winter (to run my Internet-facing server and some lighting, etc) rather than maximising year-round generation with my off-grid system.

Rgds

Damon

ChrisOlson · « **Reply #37 on:** September 22, 2012, 10:50:23 AM »

Yep - the further you move south, the better a tracker works. In the winter the sun comes up in the SE and makes a little arc across the sky and goes down in the SW, and it's only above the horizon for about 7 hours. Simply facing the panels south and tilting them up to 75Â° is what I've found works the best. A single axis tracker would only move a few degrees either way off due south, and the sun is shining thru so much atmosphere at an angle that the gains from the tracker in early morning and late afternoon are so tiny that it just doesn't pay.

And that's on the perfect day. When it's overcast, we just take what we can get. That's why I spend my time putting up more wind turbines - the turbines supply 75-80% of our power in the winter time. It's not usual to get between 15-30 kWh/day from the wind turbines from mid-November to the first of April. I've had a lot of people ask me why I don't put up bigger wind turbines like 17 and 20 footers. Well, little ones are more reliable - it's kind of like a Boeing 747 with one big engine strapped to it vs four smaller ones.
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Chris

ChrisOlson · « **Reply #38 on:** September 22, 2012, 11:57:06 AM »

Quote from: DamonHD on September 22, 2012, 10:49:52 AM

My latest panel is been put up vertical on a due-south-facing wall in fact.

Just like my solar heating panel, those vertical wall mount panels work really good in the winter when there's snow and the light reflects off the snow into the panel. On a cold sunny day in the winter I get up to 13,000 BTU from that solar heating panel, where in the fall it only puts out about 6,000-8,000 BTU
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Chris

gww · « **Reply #39 on:** September 22, 2012, 05:51:30 PM »

Chris
Questions, Where did you get your solar heating panel? What type of roof is your solar panel on; shingle, tin? Does it cause quite abit of wear on you roof?
Thanks
gww

ChrisOlson · « **Reply #40 on:** September 22, 2012, 10:12:48 PM »

I built the heating panel. It has a steel corrugated collector.

The solar panels are mounted on a building with a steel roof. They cause no wear on the roof. The panel frames are bolted to the nailers that run between the trusses with 10 lag bolts on each frame (each frame holds a pair of panels. Nothing moves even in the strongest wind. And if the wind is going take those panels it's going to take the roof with it.

This is our latest pair (the ones on the right). There was just room left on the roof for this last pair I put up. Just got 'em slid in the rack at sundown tonight

High Voltage vs Low Voltage with Classic 150

The sidewalls on the building are 10 foot so it's easy to reach them with a snow rake from the ground, and the bottoms of the panels hang over the eave so the snow can slide off onto the ground and doesn't pile up on the roof at the bottom of the panels when it slides off.

I got one more notch to raise them yet for 75 degree tilt, but I won't do that until November.
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Chris

gww · « **Reply #41 on:** September 23, 2012, 05:29:10 AM »

Chris
Very nice. I have shingled roof and it would kind of scare me to roof mount.

Is your heat panel convection or have you got a blower? Is it two piece metal with a gap covered with glass or just one piece of metal?
Thanks
gww

ChrisOlson · « **Reply #42 on:** September 23, 2012, 08:30:17 AM »

The heat panel has two blowers on it providing 160 CFM at the outlet. The collector is two piece, IIRC, and there's about 2" between the top of the corrugations and the glass. I used double glazed high solar gain Lo-E 180 glass on it with a solar heat gain coefficient (SHGC) of 0.69.

That glass was expensive but for a solar heat panel well worth the extra money compared to what most people use. The glass is coated with a very thin, optically transparent layer of silver sandwiched between layers of anti-reflective metal oxide coatings, and is argon filled. Once the heat is inside, it doesn't let it back out.

That sheet of glass is also very heavy - well over 100 lbs.
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Chris

gww · « **Reply #43 on:** September 23, 2012, 05:50:39 PM »

Chris
What do you do with the heat in the summer?

Am I waisting my time if I were to use two peices of barn tin painted black and sliding door glass If it where free? I have some of both and will use most for a greenhouse.
Thanks
gww

IIRC? Metal roofing? Gap between the IIRC?

ChrisOlson · « **Reply #44 on:** September 23, 2012, 06:50:35 PM »

gww,

There is no heat in the summer because the sun is overhead and can't shine into the panel.

That's all I used for a collector was corrugated building steel painted flat black. It works good. Your storm door glass will work OK, but it will lose more heat. You'll have to run higher CFM with single pane glass. If the glass feels warm to the touch when the panel is operating, then you need to increase the airflow in the panel until the glass runs cool. If that glass is warm you're losing panel efficiency due to heat getting back out thru the glass.
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Chris

gww · « **Reply #45 on:** September 23, 2012, 07:06:53 PM »

Chris
I looked at a bunch of sites diy solar hot water construction sites and some said to use two peices of glass with a small gap to combat heat loss and light ray angle. I also have one anderson slider that is double pain and still has the gass seal. Better or worse? On the metal part, is it one sheet or two and if two what is the gap between them.
Thanks
gww

ChrisOlson · « **Reply #46 on:** September 24, 2012, 12:59:00 AM »

I just have one collector sheet. It's make out of multiple pieces of steel, but it's just one layer.

It depends on the specs of the glass on that double glazed Anderson slider. Some of those are low solar gain and designed to reflect light to reduce solar heating. It might be double pane with argon in between the layers of glass to provide a higher R-value. But that does not mean it's suitable for a heating panel. What you want is high solar gain glass.

I know a lot of folks have used storm door glass and it works. But not all glass is the same. The glass I bought has a SHGC of .69. Most is below .40, and 20-30% more heat gain using high solar gain glass is a lot:
http://www.nfrc.org/documents/solarheatgain.pdf
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Chris

gww · « **Reply #47 on:** September 24, 2012, 05:20:37 AM »

Chris
Thank you for your help.
gww

dave ames · « **Reply #48 on:** September 24, 2012, 08:56:14 PM »

Quote from: ChrisOlson on September 21, 2012, 10:46:54 PM

I should be able to push that Classic right to its limit on the average day with 14 panels. I'll find out how good that controller is yet

SWEET! With any luck you should get up into *current limiting on a regular basis. IMHO This is using the equipment not abusing it.

Some day I hope to max out a controller..any controller!

Cheers, Dave

*supposed to start backing down in 5 Amp increments if it gets too hot.

gww · « **Reply #49 on:** May 19, 2013, 07:59:48 PM »

Chris
Did you leave your panels at the high voltage? How did it work out?
gww

ChrisOlson · « **Reply #50 on:** May 19, 2013, 11:44:17 PM »

Since we've gone to 48V (and also bought that yacht I showed in the photos) it was mandatory to wire the panels for 92.4 Vmp. We now have 6.0 kW (twenty four 250 watt panels) on one Classic controller. Can't use the full output of the array on a good day because the Classic amp limits at about 84 amps. But we didn't put in 6.0 kW of installed capacity for the perfect day. We put it in for the average day when the panels only operate at about 75-80% of nameplate. I could care less about getting full output on the perfect day.

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Chris

gww · « **Reply #51 on:** May 20, 2013, 05:11:12 AM »

You are now doing the east/west oreintation thing now correct.
gww

ChrisOlson · « **Reply #52 on:** May 20, 2013, 07:53:39 AM »

That is correct. We have 3.75 kW facing south, 1.5 kW facing due east, and .75 kW facing due west.
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Chris

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Author Topic: High Voltage vs Low Voltage with Classic 150 (Read 16464 times)