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33) On a sunny day a PV cell with an area of 10 cm by 10 cm will deliver a current of 2 A

and a voltage of 0.5 V.

(a) How much power does this PV cell produce?

(b) How many of these cells are needed to produce 15 W electrical power?

(This is the power necessary for one low energy light bulb, which provides the same level of

light as an old style 60W light bulb.)

(c) What is the total area of PV material (in m2) to produce 15 Watts?

(d) How many of these low energy light bulbs can be lit when the area of PV material is 1

m2?

34)One PV module has 48 monocrystalline silicon PV cells.The area of each cell is a pseudo square with an area of 12 cm by 12 cm.

(a) What is the area of one PV cell (assume that each PV cell is a true square)?

(b) What is the total area of PV material in this PV module (in m

2

)?

(c) The efficiency of one PV cell to convert energy from the sun into electricity is about

16.4%. How much power from the sun is required to get 100 W of electrical power output

from one PV cell?

(d) On a very bright sunny day the amount of light from the sun is 1000 W/m2.

How much power would this PV module produce at this time?

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37) Imagine a family living in Africa. They have no grid connection and hence no electricity

so they intend to buy a Solar Home System (SHS). This will allow them to have light and to

watch TV in the evening. You must help them to look at their electricity requirement to see

what size of SHS will provide enough electricity.

In Africa, where their home is, the energy from the sun averages 6 kWh/m2each day.

That means the energy provided from the sun is equivalent to a light intensity of 1000W/m2

for six hours each day. In fact there would be about 12 hours of sunlight during which time

the light intensity would vary but the daily total would be 6 kWh/m2.

(a) The PV module in a SHS has a power output of 50 Wp. Assuming that the module

operates at 25C (i.e. at STC), how much electricity will it provide every day?

(b) The family wants to have one light in the main room of the house, one light in the kitchen

and one on a table where the children do their homework. Of course they would use low

energy light bulbs, which require between seven and twenty Watts.

(Equivalence of low energy light bulbs to standard light bulbs: 7 W @ 40 W, 11 W @ 60 W,

16 W @ 75 W & 20 W @ 100 W).

Which light bulbs would it be best to use for the different lamps and why?

(c) Assume that the main light is used for four hours a day, the kitchen light for two hours

per day and the table light for three hours each day. How much electrical energy does eachlight use each and what is the total daily requirement of the lights? What power output would

a PV module require to supply this electricity?

(d) The family also likes to watch TV. If their television requires 50 W and they watch every

day for two hours, what is its daily electrical energy requirement?

(e) Does the PV module in the SHS supply enough energy for all their needs?

(f) Discuss the result.

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32) For a Photovoltaic (PV) powered calculator, please calculate the following:

(a) The PV material on a PV powered calculator is a rectangle measuring 20 mm by

5 mm. What is its area in mm2?

(b) Its efficiency, to convert power from the sun into electrical power for the calculator, is

10%. How much power input is required to get a power output of one mW?

(c) What is the light intensity (in mW per mm2) that is necessary to get this power output

from the PV material in the calculator?

(d) On a bright sunny day the amount of light from the sun is 1000 W per 1m2.

Show that this is equivalent to 1 mW per 1 mm2. How much power output does the PV

material in the calculator produce on this day?