Photovoltaics at Davidson College – a Community-Based Learning Project
Tim Gfroerer
Davidson College, Davidson, NC 28035
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.
The Rooftop
ELECTRICAL CHARACTERISTICS
THERMAL IMAGING
60 Devices in Series:
1
2
59
60
0.5V
0.5V
Current
0.5V
0.5V
0.5V × 60 = 30 𝑉𝑜𝑙𝑡𝑠
Load
Current
Current
I-V Curves Under Full Sun
The Cart
Some Devices Run Hotter:
Current (Amps)
8
Device Number
6
4
Vertical
o
30 from Vertical
o
53 from Vertical
2
0
10
20
30
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Hot!
Voltage (V)
Which Devices Heat Up Most?
Output Power vs. Load
50
Power Output (Watts)
Maximum Power
Point Tracker
(optimizes load)
Battery and
Inverter
(for AC output)
150
100
Vertical
o
30 from Vertical
o
53 from Vertical
50
0
0
5
10
15
Hottest
3 Hottest
40
30
20
10
0
0
10
20
Load (Ohms)
Efficiency
𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 𝑂𝑢𝑡
𝐶𝑢𝑟𝑟𝑒𝑛𝑡 × 𝑉𝑜𝑙𝑡𝑎𝑔𝑒
=
𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑂𝑝𝑡𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟
𝑆𝑢𝑛𝑙𝑖𝑔ℎ𝑡 𝑃𝑜𝑤𝑒𝑟 𝐼𝑛
× 𝑆𝑜𝑙𝑎𝑟 𝑃𝑎𝑛𝑒𝑙 𝐴𝑟𝑒𝑎
𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑛𝑡 𝐴𝑟𝑒𝑎
Example
𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 𝑂𝑢𝑡
200 𝑊𝑎𝑡𝑡𝑠
=
0.07 𝑊𝑎𝑡𝑡𝑠
𝑆𝑢𝑛𝑙𝑖𝑔ℎ𝑡 𝑃𝑜𝑤𝑒𝑟 𝐼𝑛
× 990 𝑚𝑚 × 1640 𝑚𝑚
2
𝜋 × 5 𝑚𝑚
Number of Occurences
200
= 14%
Acknowledgement
This project was supported by a curriculum development grant
from the Center for Civic Engagement at Davidson College.
30
40
Device Number
The Farmer’s Market
50
60