Family Cartman has a small house in the country side which is not connected to the grid. The place enjoys 4 equivalent sun hours. Therefore, Mr Cartman has decided to install an off-grid PV system in the house to supply the required electicity in the house.

The house electricity needs are summarized in the table below.

Load Quantity Power per item (W) Time of use (h) Type
Light bulb 10 20 2 DC
TV 1 80 2 AC
DVD 1 40 2 AC
Fridge 1 100 4 AC

a) When all loads are connected, what is the total DC power load in W?

b) When all loads are connected, what is the total AC power load in W?

c) Assuming that the overall efficiency for the cables, batteries and charge controller is 85% and the efficiency of the inverter is 95%, how much energy in Watt-hours will the PV panels have to produce to cover the electricity demand?

4. STANDALONE PV SYSTEM II (1 point possible)
The available panels that Mr. Cartman is looking at have the following specifications:

Power output = 120Wp

Vmpp = 20V

Impp = 6A

Voc = 22V

Isc = 7A

d) Assume the panels work under MPP conditions. How many panels will be needed to produce that energy?

4. STANDALONE PV SYSTEM III (2 points possible)
Since the system is disconneced form the grid, the family Cartman will also need some energy storage. Mr. Cartman has specified that 3 days of autonomy will be sufficient. In this case, batteries with the following specifications will be used:

Battery capacity = 105Ah

Battery voltage = 12V

Maximum allowed depth of discharge = 60%

e) The system is designed to use 24V as operating voltage. What will be the minimum battery capacity needed in Ah?

f) How many of the batteries specified will be needed?