1.      They come in a range of sizes and outputs and are available as 12 or 24 volts.  24 volt panels normally start at 120 watt upwards below this they tend to be available in 12 volt only.

2.       If you want a 24 volt system by linking the positive on panel 1 to the negative on panel 2 then you have a pair of 12volt panels that have become one 24volt panel. The remaining negative from panel 1 and the remaining positive on panel 2 make your single output which you would carry either direct to the controller ( sometimes called a regulator ) or via a junction to link up with either other pairs or single 24volt panels.  A 24 volt system will half the power that is lost in the transmission stage through cables connections etc, it will also allow you to have twice the number of panels running through a controller, could be useful if you decide to add more panels to your system at a later date.

3.       Buy some red plastic cable ties and fit one to each end of the positive cable as soon as one end is connected, this will avoid making a reverse polarity connection (pos to neg or neg to pos )at a later date, or if for any reason you need to disconnect a component at a later time.  At the bare end of the cables use insulating tape to cover to stop them accidentally touching each other or other pieces of equipment.

4.       In bright sunlight always cover the panels until such time as they have been wired into the circuit as they will start to produce power as soon as light hits them , short periods are normally not a problem.  Do not connect them to the controller at this point.

5.       Check the voltage with a simple Multimeter. set to dc and see that the reading is the same as stated on the open circuit voltage, which will be about twice the voltage.  You would be around 21 volts from a 12 volt panel and 35 to 41 in a 24 volt panel or two 12 volt ones wired in series.  You will not be able to check the amps at this point but it will be that which is stated on the panel, if it says 7amps on a 24volt panel it should be 7 amps and if it says 7 amps on a 12 volt panel then it will be 7 amps either on one panel or on two wired together, you would expect the two wired together to give you 14 amps as there are two or them but by wiring them in series you have doubled the voltage and at the same time halved the amperage.

6.       The nominal voltage from a panel is shown as higher than the 12 or 24 volts ,about 30% more as to charge batteries, the panel has to give out a voltage greater to overcome the tension in the batteries, otherwise the batteries would not charge.

7.       As all panels heat up the power it gives out drops this is called a power curve , in a graph volts are shown along one axis and temperature along another, where the corresponding lines cross is the power you can expect at that temperature , this is important in Spain so always look for this information when buying panels,  just because they seem cheap and give the same nominal output in amps will not mean you will receive that when they start to warm up.

8.       Panels do not have to be placed on a roof or high up they work just the same on the ground.  Just make sure that there are no shrubs etc shading any part of them, as an example if you shade 20% of a panel, you can louse up to 80% of its output.

9.       Under 100 watts panels are not as cost effective so go for 100 watts or greater up to a maximum of 165 watts, any larger then they are difficult to handle , I  favour 125 or 140 watts as a good size and above 100 watts they are generally priced so much per watt be it 100 or 165.

10.   Different manufactures give varying guarantees from 5 to 25 years, these guarantees almost always guarantee a power output of 80% or more output throughout the guarantee period.

11.   After you have linked all your panels together in parallel ( all the positives to one common point and the same with all the negatives ) inside a watertight junction box I would recommend connecting a large three pin blue plastic female plug to the end of the single cable that will run from the common connections so that a male can be added to the longer length to carry the total output to your controller , you will then be able to isolate the panels at anytime just by pulling the coupling apart .always use your multimeter to check for polarity ( either pos or neg ) before any connection is made ,check and double check.

12.   Good panels are fitted with toughened glass , sometimes acid etched sometimes clear so they will not flex a lot, about 5% maximum across the diagonal corners,  so always use the holes provided to fix them to a sturdy support and if you do have to drill fresh holes place a piece of steel behind where you are going to drill as being fitted within an aluminium frame you will find a sharp drill will go through very quick and suddenly and if you should damage the white backing to the panel you may well have a problem as they are sealed to be watertight.

     12a.    Not really superstitious but why take a chance.  The last point that springs to mind just when I thought I had finished is, turning panels to face the sun.  If your panels are mounted on a movable rack with wheels, or a central post you can increase the daily output by about 10% by facing them south south east at the start of the day and moving them to face the sun every hour until they end the day facing south south west.  On a fixed system they need to be due south and either 30 or 45 degrees depending on the time of year.  Push a stick in the ground then around 1pm face the panels the opposite way to the shadow.  Tracker systems that use a sensor to track the sun, and through a system of links and using a motor move the panels to follow the sun, claim up to an extra 30% output but I doubt it and have never seen any proof in the ones that I have seen fitted, they do not take into account that the motor to drive the panels uses power from your system.  The most effective way to use this type of system is to have it move 10 panels or more to make the power needed to run it a lower percentage of the gain.  They sample the different light levels and many do not move at all on a cloudy day, as there is no appreciable light difference as the clouds diffuse the light.  In my opinion the money would be better spent on extra panels to increase the output from a system.  A simple calculation on the size of your systems output then add 30% to it then find out what the same amount of money would buy in terms of extra panels and the respective output that they would produce.

Article Kindly contributed by Mr. Dave Stead
 

Part 2