DIY Solar Network

I built 5, 60w solar panels. Checked voltage before & after mounting on roof. Each produced 18.5v or more. Since i live at 41 degrees N. lat. I mounted them facing due south and at 41 degrees. They only produced about 14v at noon. I played with the angle and found 13 degrees worked best. They've been in service 6 wks now and I've noticed that they charge best from 7:00 to 10:00 am. And here is the wierd thing. On sunny days, they can barely charge 4, 35ah batteries to capacity. But on cloudy days it charges like it's on steroids. This has happened every cloudy day since they've been in use. Anyone have any ideas about this?

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Comment by dan baker on May 7, 2011 at 10:42am
Thanks for responding,Don. Wire gauge from panels to controller is 12 gauge as it's only about 15 feet. Only have 4, 35 amp hr batteries for now. All I could afford & wanted to get started right away. Controller is 2000w 160 amp. Got one bigger than I need so I don't have to buy another later when I add to the system. Inverter is 2500w, 5000w peak. Bike is DC also. Works great at night & when batteries are low. Am very interested in wind power. What can you tell me about your turbines? How many do you have, what size motors, distance from house, wire gauge, etc.? How many battery banks do you have & what must your capacity be to be off grid? Any info would be helpful & greatly appreciated. Thank you.
Comment by Don Dunklee on March 25, 2011 at 8:16pm
What gauge wire are you using from panels to house?  If gauge too small, when output increases to the point the wiring heats and increases resistance.  What polarity do you have on the bike?  One of my windmills starts charging below 12 volts when the wind is slow.  The battery charge goes down while it is turning slow, but when it stops the charge returns.  I guess if you add a lower voltage to a higher one they balance downward.  What batteries are you using?  As far as angle, the logic is matching latitude is supposed to make the plane of the panel perpendicular to the sun rays, thus more of a power gain with direct rays.  Other factors play into this.  For example, how much reflection you get from the foreground in front of the panels.   Snow and water reflect the sun as does light colored cement, metal roofing if light colors, etc.  maybe the angle that gives you more power is adding reflected light, or the box design and plexiglass itself is playing into this. Low e glass is better as plexiglass does not transmit as much light.  Could the plexiglass have a grain so to speak that is bending the light requiring a different angle?  Plexiglass expands and contracts more than glass and the seals can pop easier.  My experience here in Michigan is solar gives more total power during the year, however with less sun in the winter, the windmills make up the difference of less sunlight.  They also charge durning the night while panels won't.   What charge controller and inverter are you using?   ddd
Comment by dan baker on March 25, 2011 at 6:01pm

Thank you for responding. I agree with your assessment as it seems logical, but also, since last June when I put the panels in service we have gone through the 1st winter. They surely do love the cold. On cold days with even low sunlight they charge at between 19 & 20 volts. Much better than I ever expected. The panels are made of wood with heavy white paint. Clear plexigass is adhered with screws & the best silicone sealant I could find. Then I sealed all edges with exterior aluminum duct tape, covering all exposed wood even though it's well painted. Overkill perhaps, but I didn't want any leaks. After 10 months in service they look like new and thankfully no leaks. Each panel contains 36 cells. 4 rows of 9 soldered in series. Each of the 5 panels has it's own wiring running to buss bars. Then 1 positive &1 negative wire running into the house. A total distance of 15 feet. not much voltage drop for a 12v system. Anyone else find that matching the latitude where you live doesn't work? At my latitude,41 degrees, I could only get 14v. But at 13 degrees it jumped up to 18v. All the info I've read said you need to match your latitude. Why do people say that? Are they just repeating what they heard? I wonder if they played with the angle would their panels work more efficiently. I wonder if anyone has tried. My system is small for now, until it pays for itself, then I'll upgrade. I have $1200.00 invested and produce 300watts. $4.00 per watt. Not bad I think. Can't wait to add more panels & batteries. Right now I can run a t.v. for 6 hrs. on a full charge. but then it takes 2 or 3 days to fully recharge. I noticed recently that if i only use it 2 or 3 hrs. a day it recharges faster & I can use it every day. In the 10 months it's been in use my electric bill has decreased each month over last year even though the rates have increased. Solar isn't really cost effective but if you comparison shop & do all the work yourself you can actually make it worthwhile. I have no regrets so far. It's kinda fun too. Built a small wind turbine using a 12v treadmill motor but pushing 12v from the back of the property where there are no wind obstructions to the house is just too far for 12v. Got the motor free. Guess I'll have to invest in a 24v motor. I believe wind is much more efficient than solar. I also raised a bicycle on a stand & mounted another treadmill motor beneath the back wheel. Pedalling slowly gives me as much voltage as I need. If I really push it I can get 35+v. The panels run through a charge controller but the bicycle is hooked directly to the batteries. {when in use}  Somehow. when the panels are charging the batteries & I pedal at the same time the batteries actually lose some charge.  Don't get that. The faster I pedal the worse it gets. It's hard to pedal at an exact speed for a sustained period. I have voltage meters connected to everything so I can watch solar output, bike output, & battery voltage simultaneously.. At night when only the bicycle is in use it works great. Don't really need the bike just wanted to try it. Don't really want to do the pedalling either. lol. Comments, please. Thank you.

 

Comment by Don Dunklee on March 6, 2011 at 1:05pm
This is correct Tim,  My farm has been off grid for nearly 28 years and the highest amp charges are on the days when it is below zero and bright sun.  This much difference means the heat has no way to leave the panels.  Need a way to cool them on hot days.  What is the glazing and how are the cells sandwiched?
Comment by Timothy Benoit on December 14, 2010 at 9:49pm

This could directly be related to the fact that solar panels will lose efficiency as they heat up. The cloudy days may be cooler and therefore allow the panels to work better than when the sun is shining on them directly and heating them up.

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