#### LESSONS OF EASTER ISLAND

March 17th, 2016

Electrical appliances usage:

• Four 7.2 W-12 VDC Linear LED lamps used for 5 h per day.

• Two 6 W-12 VDC fan used for 10 h per day.

• Other DC appliances 10 W for 2 h per day.

A. Power Consumption Demands

Total appliances use = (7.2W x 5h) + (6W x 10h) + (10W x 2h)

= 116Wh/day

Total PV panels energy needed = 116 Wh/day x 1.3 (the energy lost in the system)

= 150Wh/day

B. Size of the PV Panel

Sun energy is available for 4 h a day.

Total Wp of PV panel = 150/4 = 37.5Wp Actual requirement = 40 Wp one module

C. Battery Sizing

The battery should be large enough to store sufficient energy to operate the appliances at night and cloudy days.

Total appliances use = (7.2W x 5h) + (6W x 10h) + (10W x 2h)

= 116 Wh

Divide the total watt-hours per day used by 0.85 for battery loss = 116/0.85

= 136.47 Wh

Divide this number by 0.5 for depth of discharge = 136.47/0.5

= 272.94 Wh

Nominal battery voltage = 12 V Days of autonomy = 2 days

Battery capacity = (272.94Wh/12V)x 2 = 45.49Ah

Total ampere-hours required = 45 Ah (or better 75 Ah) deep cycle battery to

have a longer lifespan:

So the battery should be rated 12 V 50 A h for 2 days autonomy.

D. Solar Charge Controller Sizing

According to standard practice, the sizing of solar charge controller is to take the short circuit current (ISC) of the PV array, and multiply it by 1.3 PV module specifications

Pm = 40 Wp Panel voltage = 12 V

Solar charge controller rating = 40Wp/12 V = 3.33 A

So the solar charge controller should be rated 5 A 12 V or greater.

10 ft x 10 ft Kitchen illuminated by 7.2 W warm cool solar powered LED light |

[1] LED lamp 20 W

• Fluorescent lamp 22 W

• Incandescent lamp 100 W

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