In the Fall of 2012, our junior-level electronics class conducted an investigation of photovoltaics at Davidson College. We started by touring the new 100 KW installation on the campus sports complex. Then we employed a solar cart (built by the physical plant using a spare 240 W panel) to study the circuitry required to store and utilize solar energy. The cart facilitated an in-depth examination of the practical, electrical, environmental, and thermal issues inherent in photovoltaic energy conversion. We concluded the study with a public exhibit at the local (Town of Davidson) farmer’s market.

Photovoltaics at Davidson College – a Community-Based Learning Project

Tim GfroererDavidson College, Davidson, NC 28035

The Rooftop ELECTRICAL CHARACTERISTICS

Some Devices Run Hotter:

60 Devices in Series:

I-V Curves Under Full Sun

THERMAL IMAGING

Which Devices Heat Up Most?

Acknowledgement

This project was supported by a curriculum development grant from the Center for Civic Engagement at Davidson College.

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1 2 6059

Load

0.5V 0.5VCurrent

CurrentCurrent

0.5V

0.5V 0.5V

0 10 20 30

2

4

6

8

Vertical

30o from Vertical

53o from Vertical

Cur

rent

(A

mps

)

Voltage (V)

Output Power vs. Load

0 5 10 15

0

50

100

150

200

Vertical

30o from Vertical

53o from Vertical

Pow

er O

utpu

t (W

atts

)

Load (Ohms)

𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟𝑂𝑢𝑡h𝑆𝑢𝑛𝑙𝑖𝑔 𝑡 𝑃𝑜𝑤𝑒𝑟 𝐼𝑛

=𝐶𝑢𝑟𝑟𝑒𝑛𝑡×𝑉𝑜𝑙𝑡𝑎𝑔𝑒

𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑𝑂𝑝𝑡𝑖𝑐𝑎𝑙𝑃𝑜𝑤𝑒𝑟𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑛𝑡 𝐴𝑟𝑒𝑎

×𝑆𝑜𝑙𝑎𝑟 𝑃𝑎𝑛𝑒𝑙 𝐴𝑟𝑒𝑎

𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟𝑂𝑢𝑡h𝑆𝑢𝑛𝑙𝑖𝑔 𝑡 𝑃𝑜𝑤𝑒𝑟 𝐼𝑛

=200𝑊𝑎𝑡𝑡𝑠

0.07𝑊𝑎𝑡𝑡𝑠𝜋 × (5𝑚𝑚)2× (990𝑚𝑚×1640𝑚𝑚 )

=14% 

Device Number

The Cart

Efficiency

Example

0 10 20 30 40 50 600

10

20

30

40

50

Num

ber

of O

ccur

ence

s

Device Number

Hottest 3 Hottest

The Farmer’s Market

Maximum PowerPoint Tracker (optimizes load)

Battery and Inverter(for AC output)

Hot!