Study - 3

• 2. Investment and value for money (continued)

SOLAR ENERGY

A typical solar energy system components are:

1. Solar panels to harvest the sun's energy and change it to power.
2. Solar charger/controller to regulate the rate of charging for batteries and prevent overcharging.
3. A battery bank to store harvested energy.
4. An inverter to convert DC voltage to AC voltage for powering the home appliances.

As for the UPS, I will need the same battery bank, but what about the other components?

I have to choose solar panels with enough current to charge my battery bank as fast as possible. If I have a typical solar panel of 100 Watt and output voltage of 18 V DC, then the current output is about 5.5 Amperes. Charging 400 Ah batteries from 5.5 A solar panels requires 73 hours (if I assume that I will not discharge the batteries more than 50%, then the charging time will be calculated for only 200 Ah and will be equal to 36 hours). I must here account for the fact that sun does not rise at night, so every day I have limited amount of hours for charging my batteries.

In Cairo, Egypt, we are blessed by long solar radiation hours (hours that the sun is visible in our sky) which are an average of 9 Hrs per day (6.4 Hrs in December and 11.7 Hrs in July).

This results in about 9 hours of charging per day. For 36 hours of charge to fill the 200 A, I need 25 / 9 = 4 days. So I will be able to use my solar energy for one day (1.5 Hr) and keep it charging for 4 days.

If I doubled, tripled or multiplied my solar panels, the charging time will be reduced, but note that an average monocrystalline solar panel (types will be discussed later) costs about 200$ (add 30% for customs and shipping) equals 1820 EGP.

The voltage output for the solar panel is 18 V DC. Connecting that voltage directly on a battery pf 12 V DC

will ceratinly overcharge it, then the battery will be damaged (The damage ranges from overheating to explosion according to battery type which will have it's own discussion later). A charger controller is then needed to regulate the output voltage from the panel to charge the battery in a safe way.

Battery charger controllers are selected according to their input voltage and current. A typical charger controller for one panel is a 12 V DC, 10 A solar charger controller and can be bought for 15$ to 20$ for a basic function (without LCD or other options) equals about 180 EGP.

The last component is the inverter. I needed an inverter of 12 V DC inpuut and 220 V AC output and with

power enough for my 1.6 kW calculation. An 2000 kW off grid inverter (types will be discussed later) which outputs pure sine wave costs 280$ + shipping 80$ = 360$ equals about 3100 EGP.

To sum up the cost, I need at least a solar panel (1820) + charger controller (180) + inverter (3100) + the same battery bank (8000) = 13100 EGP

Take into consideration that I will get my power for free and that will be cut off my electricity bill (not too much but better than nothing)

I was very surprised to see that the cost of the solar energy system was less than that of a plug and play UPS by about 20% plus the fact that the power is for free.

At this point, both systems are not coping with my goal yet (I can't rely on a system that is powered once or twice a week for that price), so I decided to make some assumption/modifications/estimations/requirements.