THIS PORTION IS FOR THOSE INTERESTED IN TECHNICAL CONSIDERATION IN USING SOLAR ENERGY



The first step is to define the energy need/purpose. For example, the need is for a 20W flourescent lamp to be turned on 3 hours a night for a school child to study. Check the ampere that the bulb takes in and for a 20W f-lamp, it is about 1 ampere. So the need is for 3 ampere-hour daily.

Factor in the loss of energy in charging a battery. A good guide is theratio of 1.5:1,meaning 1.5 in and 1 usable. In short the battery has to be charged at 150% of the desired usable power.

In our case, 1.5 x 3 AH is 4.5AH. Thus, we have to put 4.5 AH into the battery. So, we must a battery that can absorb and DELIVER the 4.5AH. |Solar Panels usually delivers 17 voltsD.C., enough to charge a 12V battery. But battery capacity is in AH. The smallest car battery is 40AH.
That is excessive four our need.We can buy a 7AH battery or a 12AH battery. The one shown in the pix is the latter.

Now, producing 4.5AH with solar cells is a function of the ampere the cells can deliver and the time charging. First, we have to estimate average sunlight available. The standard established for the Philippines is 5 hours. ok, let's use that. To produce 4.5AH over 5 hours,we would need a Solar Panel delivering 4.5/5 ampere or that is .9 ampere or 900 milliampere.A 15watt SP delivers .87 amp and a 20W SP delivers 1.16 amp. |We sould be conservative to use a 20W SP.

However, we can reduce the requirement if we use more efficient lightbulbs such as the LED. Whilethe claim is that the LED power consumption is 1/5 of the conventional bulbs, it is on the prudent side to just use 1/2 or 50%.Thus, if we used LED bulbs above, we would need only a 10W Solar Panel such as the one hled by the author in the picture.

From hereon, it is easy to "extrapolate". If we wish to double our bulbs, well, double our SPs. But we also have to raise the capacity of our battery.

THE ROLE OF THE CONTROLLER

The controller protects the battery from overcharge and from overdischarge. When the battery is fully charged, the controller "dumps" the energy from the SP. That is why it is foolsih to have excessive SPs to what the battery can hold. The controller shuts off the load(the lamps) when the battery has reached a criticallevel and in the test done,it is 11 volts. Some controller, has an auto switch to turn on the lamp at dusk and off in the morning. The SP itself is the sensor.

Next, we shall discuss cost effectiveness of Soalr Energy.....