Solar panels are arrays of interlinked solar cells. A solar panel normally forms part of an overall Photovoltaic (PV) electrical system to generate and distribute electricity.
PV panels do not sometime function at all and even it works; it does not generate power at optimum levels. There are many reasons for malfunctioning of the solar panel. But the question is, how do you troubleshoot a faulty solar panel?
Here are 4 of the causes for malfunctioning of home solar panels and possible solutions to overcome the problem.
1) Over-heating problem.
If the solar panels are installed in comparatively warm areas; the panels are likely to absorb sweltering heat. In the midday, during the scorching sun, the solar cells function at above their normal temperature limits resulting in considerable drop in voltage of the solar panel system.
This is a usual feature and they recover once the atmosphere cools down. For example, a normal 18V capacity PV cell is designed to operate at around the voltage range of 17 to 18 at 25° C. Even if the efficiency level decreases due to high temperatures, the voltage of solar cells can be still around 12.
However, if the voltage drop is much below this level; it may be due to either a weak PV cell or defective electrical connections at some place in the array.
2) Corrosion and expansion of connections due to heat.
Oxidation and expansion of electrical wiring due to heat can result in increase of resistance and consequent reduction in power generation. Wrapping with a sheet or pour water over it, without removing its outer covering may help in cooling the array.
Once the system is cooled, the voltage may return to a normal range and if it does not happen, there may be a faulty cell in the array. A ‘shading test’ will help in locating any faulty cell in the system.
In order to carry out a Shading Test, the panel should be dismantled first and after that, the faults in the cells or electrical wiring can be identified by just shading portions of the panel by turns. Keeping the panel disconnected, check the output with a multi-meter or test the load using a small fan.
If in spite of shading a portion of the surface of the panel, the power does not drop, it means that cells in that portion of the panel are not functioning efficiently.
In order to locate the faults, all the tabs and wiring at intersections of the nearby sequence of cells should be checked. Any indication of corrosion at any point in the sequence of cells may be the origin of the malfunction of the system, leading to decrease in power generation. This problem requires immediate attention and if it is not rectified soon, it may damage a cell due to excessive heat.
The additional resistance due to faulty soldering increases the load as well as the overall resistance and the prolonged excessive heating of the cells leads ultimately to its breakdown. Besides a visual check of all connections, the Shading Test can be helpful to spot the defective area of the panel. The problem may be due to poor soldering.
3) Moisture in solar panel.
If by any chance the moisture gets into the cell, it will be a very big problem. Moisture is the root cause of oxidation and it corrodes all electrical connections.
If the home is situated close to seashore, all electrical connections can get corroded because of salty moist breeze coming from the sea. Moisture can also make wood go out of shape and twisted wooden panel container can cause breaks in electrical connections or cracks may develop in cells.
In order to overcome this sort of problem, it is advisable to use aluminum or Perspex sealed panel even if it means an additional expenditure. All corroded metal parts and connections should also be replaced without any delay.
4) Damaged blocking diode.
Most of the PV arrays use a “blocking diode” to stop array from discharging the batteries at night. Though not very common, a damaged blocking array can also contribute to the system failure. If this is the problem, there will not be any power output at the connecting leads.
If possible faults in all other vulnerable areas are eliminated; the next course of action is to carry out a “Diode Test”. If the diode is defective, it should be replaced immediately. If one is in a remote place, the diode should be taken out from the circuit till a replacement is procured.
The panels should be disconnected at night till a replacement is obtained; otherwise your battery bank will get totally discharged. In order to minimize expenses, some people try to group several smaller diodes to correspond with the “blocking amperage”.
However, it is not at all advisable to use smaller diodes. This is because the electric current will first flow through the smallest diode, the lowest point of resistance, till it gets overheated and fails, then the current flows through the next diode till it also stops working and ultimately. Everything short circuits and blows with disastrous consequences to the whole electrical system.
If you want to have a diagnostic test carried out on blocking diodes, it is advisable to information about the said diode before proceeding.
Solar panels are, generally, dependable, even in cloudy atmosphere or in snowy conditions, if they are properly maintained and kept clean. Moisture causes a lot of damage and therefore panels should always be in sealed condition.