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Tribes make Solar Posted at 01/19/10 - 05:35 AM

New Mexico's Jemez Pueblo tribe is working a deal to use their land for solar energy production. They will be the first Native American tribe to use solar energy as a way to make revenue.  The 3,000 members of the tribe are working to harness the energy from their 30-acre site. They plan on setting up over 14,000 solar panels. A plan is now in the works to sell electricity to outsiders from their four-megawatt plant. The completed plant would be able to power about 600 homes.

Author: Greg

Recent studies suggest that technological progress has reduced payback times to 1.5 to 3.5 years for crystalline silicon PV systems.




Checking Faulty Solar Panel Blocking Diodes

Solar power systems are very reliable, but every now and then, small problems can appear.  These may be simply a slow or unexpected drop in your power output from your solar panels, and it is not obvious where the problem lies.  Or, you seem to have no power in your batteries even though there has been good sunshine and nobody has been "hogging" the power. It is time to do a little detective work.  You will need a Multimeter(Voltmeter) to check your system, otherwise call an expert.  Remember you are dealing with electricity and if you don't know what you are doing, call a professional.

The most common problems will be poor connections affected by corrosion, or you may be looking at a defective Blocking Diode.  Just to remind you, if the solar panel is not producing current, the blocking diode prevents current flowing "backwards" out of your batteries and draining them. The blocking diode is a bit like a cut-off valve.  Each solar panel should have a blocking diode installed to prevent battery drain.  However, if the diode is faulty, it can mess with your whole system, especially when there are periods of low light such as a cloudy day or morning and evening.  

Once you have checked any obvious system problems, move on to checking the panels. Firstly, disconnect your panels from the system, and either remove the battery terminals or throw the isolation switch to your batteries.

First Test : Disconnect and check the output of each panel. If your panels are not producing power at the expected rate in full sunshine, you will have either a bad connections ( corroded), a problem cell or faulty diode.
Visually check connections for corrosion and see if any of the cells appear hotter than its neighbors. If all seems well, move on to checking the blocking diode.

Second Test : The Blocking Diode should be installed with the Silver Ring facing "away" from the panel toward the output connection (towards POSITIVE),  some diodes may have an Arrow pointing in the current flow. Make sure it is actually installed the right way.
Quick tip - the black multimeter lead is always connected into the socket marked COM, short for COMMON.  Using the multimeter set to read OHMS,  place the COM probe on the end away from the diodes Ring-End and the other probe at the Ring-End.  You should have a zero or low reading.  If you have a high reading, there is a problem with the diode.  Now we will double check with another test.  Reverse the probes so that the COM probe is now on the Ring-End of the diode. You now should get a high resistance, if not, the diode is faulty.  The solution is simple, replace it with the correctly rated blocking diode.

When it comes to blocking diodes, you should always install a single correctly rated diode.  If you try to cut corners or costs by using several smaller diodes in parallel, you are setting yourself up for real problems.  Since diodes are rarely equally matched, the weakest diode takes all the load and will eventually short out and fail. The load then passes to the next diode, which does the same and so on, finally leaving you with a blown circuit that cannot pass current to your batteries.

Some simple periodic checks of your system will usually prevent a small problem from becoming a big one, especially if you depend on your system to provide power. A Solar DIY panel system is a cost effective way to make electricity, just make sure you follow your instruction guide properly and keep your system in good shape.

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