Test Results – Test Day 1
P08404 – Solar Water Pasteurizer
Date: 4/8/2008
Time: 10:30am – 2:00pm
Test Water Source: Tap Water
Weather:
Time
Morning
Noon
Afternoon
Sun
Sunny
Hazy
Sunny
Wind
Very Windy
Windy
Windy
Total Output (L): (Unknown)
Summary
The P08404 solar water pasteurizer was setup and successfully tested for the first time. Test water was
brought to an appropriately high temperature for an adequate period of time to be considered
pasteurized. Clean tap water was used for this test day, so pasteurization could not be confirmed
through a multiple-tube fermentation technique test. Upon reaching steady-state operation, output
flow was in the target range to achieve 100L/day total output. Due to debugging, no final water output
quantity was recorded.
An issue with air becoming trapped in the system was identified. A workaround was implemented in the
field, with a final fix planned before the next test day.
Temperatures in the system were higher than required for pasteurization, indicating an opportunity to
increase output flow rate. Methods of increasing flow, both increasing input pressure and decreasing
flow resistance, will be considered.
Results
(Note: Due to issues with DAQ, all time axes may be early by as much as 20 minutes. The initial warm-up
period was also missed.)
Sunlight and Ambient Air Temp
30
670000
25
660000
655000
20
650000
645000
C
15
640000
635000
10
630000
625000
5
620000
615000
10:30
10:38
10:47
10:55
11:04
11:12
11:21
11:29
11:38
11:46
11:55
12:04
12:12
12:21
12:29
12:38
12:46
12:55
13:03
13:12
13:21
13:29
13:38
13:46
13:55
14:03
14:12
14:20
14:29
14:37
14:46
0
Ambient Air
Solar Irradiance (Smoothed)
Graph 1: Weather Data
The day had strong sun and wind in the morning, becoming hazy around noon, and finishing in the
afternoon with good sunlight, light wind, and around 23 degrees Celsius ambient air temperature.
Unknown Linear Irradiance Units
665000
Surface Temperatures
120
670000
660000
655000
C
80
650000
645000
60
640000
635000
40
630000
625000
20
Unknown Linear Irradiance Units
665000
100
620000
615000
10:30
10:39
10:48
10:58
11:07
11:17
11:26
11:36
11:45
11:55
12:04
12:13
12:23
12:32
12:42
12:51
13:01
13:10
13:20
13:29
13:39
13:48
13:57
14:07
14:16
14:26
14:35
14:45
0
Hot Plate
Glass Surface
Cold Plate
Solar Irradiance (Smoothed)
Graph 2: Plate and Glass Surface Temperatures
As expected, the coldest point on the plate followed the hottest point on the plate, and the surface
temperatures were in order of descending temperature from hottest plate temperature, to coldest plate
temperature, and outside of glass temperature. Interestingly, the hottest point on the plate did not
exceed 100 degrees C, regardless of solar irradiance, possibly due to a phase change of the water in the
system.
Valve Temperatures
120
100
80
C
60
40
20
10:30
10:37
10:45
10:52
11:00
11:07
11:15
11:22
11:30
11:37
11:45
11:53
12:00
12:08
12:15
12:23
12:30
12:38
12:45
12:53
13:01
13:08
13:16
13:23
13:31
13:38
13:46
13:53
14:01
14:08
14:16
14:24
14:31
14:39
14:46
0
Valve - Plate Side
Valve - Output Side
Hot Plate
Valve Activation
Graph 3: Valve Temperatures
The plate came up to temperature quickly. The water in the valve remained low in the morning, likely
due to an issue with trapped air in the reservoir preventing the heat exchanger from operating normally.
After reaching operating temperatures, the valve tended to follow changes in the plate temperature.
Hot-Water Reservoir Behavior
100
90
80
70
60
C
50
40
30
20
10
10:30
10:37
10:44
10:52
10:59
11:06
11:14
11:21
11:28
11:36
11:43
11:50
11:58
12:05
12:12
12:20
12:27
12:34
12:42
12:49
12:57
13:04
13:11
13:19
13:26
13:33
13:41
13:48
13:55
14:03
14:10
14:17
14:25
14:32
14:39
14:47
0
Valve - Output Side
Reservoir Exit
Chart 4: Reservoir Behavior
This chart clearly illustrates the issue of air becoming trapped in the reservoir. After this air was
released, a high flow rate was realized and the water temperature at the reservoir exit increased
dramatically (this occurred around 12:40).
Valve Behavior
85
84
C
83
82
81
80
13:34
13:34
13:35
13:35
13:35
13:35
13:35
13:35
13:36
13:36
13:36
13:36
13:36
13:36
13:36
13:37
13:37
13:37
13:37
13:37
13:37
13:37
13:38
13:38
13:38
13:38
13:38
13:38
13:39
13:39
13:39
13:39
79
Valve - Plate Side
Valve - Output Side
Chart 5: Valve Behavior
This chart illustrates a potential problem with water flow through the system. Water on the plate side of
the valve remained around a constant 81 degrees. Water at the output tended to oscillate. This may be
due to air in the system causing irregular flow through the valve, and will be looked into in greater depth
during future tests.
Valve - Output Side
Reservoir Exit
Chart 6: Reservoir Behavior
The hot water reservoir behaves as expected. Temperature tends to follow the valve output
temperature, with a loss of about 2.5 degrees C.
13:39
13:39
13:38
13:38
13:38
13:38
13:38
13:37
13:37
13:37
13:37
13:37
13:36
13:36
13:36
13:36
13:36
13:35
13:35
13:35
13:35
13:35
13:34
13:34
13:34
13:34
C
Reservoir Behavior
85
84
83
82
81
80
79
78
77
76