Solar Panel Output
Troubleshoot Solar Panels – A quick overview of locating problems with your DIY Solar Panel
Author: Greg Murry
The sun is out but there’s no electricity is being produced from your solar panel, what’s going on!
Let’s do some quick trouble shooting. Let’s assume that your array has been operating properly for some time and in a short time or suddenly, power output has fallen or simply stopped altogether.
Remember, your array produces electricity so take proper care of your safety, if you’re not confident, get a professional to assist. Remember, if you have more than one array and they are connected in parallel, the system will push out much more power(Amps) than a series connected system. Remember that shorting your battery terminals is extremely dangerous, so – respect electricity!
If your solar array is a commercial “off the shelf” system, pick up the phone, they should, have all the diagnostics needed. If your array is a DIY Solar Panel project then lets make start. We will also assume that you have checked the obvious, like someone hasn’t ripped the array output lead out with a ladder or something, and, there are no bullet holes through your array. Do the panel a favour, and clean the protective surface from dust. Now, this sounds obvious, but disconnect the array from your controllers and simply check that current is flowing at the output lead. If it’s operating properly, check your contoller system. Normally solar cells and arrays are extremely reliable and stand up to weather extremes and even hail if properly constructed. However, there are a few things to keep an eye out for.
Checking the array with a Selective Shading Test
Disconnect the array and monitor the output with a voltmeter or test load. This trick will help you locate a faulty cell or wiring section without disconnecting the array wiring. Shade at least 4 cells. Shading just a few cells should drop the arrays output to less than half. If it does not, then the cells in that area of the panel is not working properly, also look at the wiring of the nearby in-series cells.
Over-Heating Problems
Sometimes, the voltage coming out of the system drops during the hottest part of the day and is due to the cells operating outside their optimum temperature range. A typical 12V PV cell is designed to work at about 17 – 18V at 25C, in this case you should still get about 12V when efficiency falls at higher temperatures. If your “drop” is worse, then its very likely there is a weak PV cell or poor connections somewhere in the array. Check the array output by cooling the array, (pour water over the array – WITH the cover still in place or you’ll short out the array!). Disconnect the panel from the system and check the open voltage on your output lead, once cool, your voltage should return to normal. If it is below 18 volts, look for a faulty cell by shading each in turn while watching power output with a voltmeter or test load.
Faulty Connections
Over time, oxidation and corrosion can affect electrical metal connections. Screws can loosen, metal can warp, and electrical resistance can occur, warpping of the support can even crack a cell. Replace all corroded or oxidized metal parts and connections, rewire the cell tabs if needed. Look for damaged wiring and replace it. Most PV arrays use a blocking diode to prevent your array from discharging your batteries at night. Occasionally, a diode can short out, replace the diode – or if in a remote location, remove the diode from the circuit, BUT, remember to disconnect the array at night or you will drain your batteries. Good luck and may your panel keep converting.
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November 30, -0001
12:00 am
Solar panels are rated under standard test conditions (STC), a certain amount of light at a certain distance, at a certain temperature, etc. A kW, or kilo watt, is 1000 watts. So for the amount of time that the sun meets those conditions, the rate of output is 1500 watts. An average location has an average of 5 sun hours a day, the total time that you produce the rated output.
Watts is a rate, like miles per hour (mph), how fast it is going. Watt hours, or kilo watt hours (kwh) is a quantity, like miles. So if you drive 50 mph for 5 hours, you went 250 miles (50 mph x 5 hours). If you produce 1.5kw for 5 hours, you have the potential to produce 7.5kwh a day. Multiply that by 30 days in a month, you get 225kwh a month. In reality you will lose about 30% of the rated power from less than ideal weather, system losses, etc., so it’s more like 150kwh a month. You can look at your electric bill to see how many kwh you use a month, maybe around 1000kwh, and see what percentage of your usage a system like that can power.
November 30, -0001
12:00 am
A Watt is an instantaneous measurement. A watt hour is a unit of energy. A 200 Watt panel will produce about 200 Watts as long as the sun is shining. I’m not sure what your getting at here but I think you want converter Watt hours to another unit of energy such as BTU’s or joules.
November 30, -0001
12:00 am
Individual cells are about 1/2 volt each. How they are interconnected and how many cells there are determine the total voltage and current.
Larger ones are configured usually for 12 or 24 volts.
It’s like a bunch of 1.5 volt batteries. You can connect them all in parallel, all in series, or any of many series parallel combinations.
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November 30, -0001
12:00 am
By the sine of the angle. If you haven’t taken trig yet, I’ll just mention that the sine of an angle is the ration of the length of the adjacent side of a right triangle to its hypotenuse and refer you to wikipedia for more detail.
What you need to do is set up a light source such as a 100 watt light bulb perhaps about 1/2 meter over a table. Hot glue the straight sides of 2 protractors to the bottom of your solar cell. Then you can use little props like maybe a couple of erasers so that you can angle the solar cell any way you like, reading the angle indicated by the protractors where they touche the table top.
Then you need a voltmeter and a load. A good load for an average solar cell might be a 100 ohm resistor from Radio Shack. Connect the resistor across the output of the solar cell via a pair of wires, hook the voltmeter across the resistor, and take readings of the voltmeter at say every 10 degrees from 90 to 0 degrees. Make a graph.
I don’t know how sophisticated you intend to get with this, or your grade level. The above setup will give you a very basic experiment. The voltage output will increase with angle up to a peak at 90 degrees. But it is the power output of the solar cell that will be proportional to the sine of the angle of incidence, and power equals voltage times current. Email me if you want more information or have questions.
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November 30, -0001
12:00 am
That’s cool (so to speak) as a problem, but it’s hard to move the satellite toward or away from the sun if it is in orbit around a planet.
If it is free of any planet (a artificial satellite of the Sun) then that’s a whole additional thing.
You’ve got the right idea. Do you have equations for:
1. Electrical output vs. sunlight intensity
2. Electrical output vs. temperature
3. Temperature vs sunlight intensity
4. Sunlight intensity vs distance from Sun
Depending on the construction of the solar panel, you could arrange to have radiation cooling from the back of the panel to keep its temperature down. Even in earth orbit, this temperature vs. power budget tradeoff is an important engineering factor in solar panel and spacecraft design.
Good luck with the math.
September 5, 2007
3:57 am
how does the output of a solar panel vary with the angle of the light?
how does the output of a solar panel vary with the angle of the light? I need to do a experiment about it. Is anyone can help me create a experiment to test it? Thx.
September 8, 2008
4:37 pm
How to calculate Solar Panel output?
Im looking for some direction on solar panel stats such as:
When I buy a 200 watt solar panel, does that mean it produces 200 watts per hour? day?
And any more information would be great.
November 29, 2008
6:35 pm
Optimize the distance of the solar panel on satellite from Sun to give maximum power output.?
I need help doing this problem.
How can i differentiate and find out the optimum distance of the solar panel on satellite to give maximum power output.
When the solar panel is too close to the sun it will receive more light intensity and more temperature which will reduce the power output and when the solar panel is far away light intensity will decrease so less power output. So there should be a distance in-between this 2 variables where it produce max power output.
Thank you.
November 25, 2009
3:52 pm
What is the average voltage output for a solar panel?
What is the average voltage output for a solar panel? I’m speaking of the small sized ones that would go on the side of a house. Perhaps an answer given in per-area would be good.
Thanks!
July 27, 2010
9:12 pm
What does solar panel output refer to?
If a solar panel is a 1.5kW system, what length of time is it putting out that much power? Every hour?