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Solar Thermal Ice Production Adam Gage, Peter Shoaf, Jeromie Webster, Logan Olsen
Dr. Alex Yokochi*, Justin Pommerenck, Peter Kreider
Chemical Engineering 2013 Senior Project
Oregon State University, Corvallis, OR
Abstract
Theoretical Background Adsorption is the accumulation of molecules of a gas (adsorbate) to
adhere to the surface of a solid (adsorbent). Adsorption refrigeration
consists of the evaporation and condensation of a working fluid to draw
heat from the system. It does not use any mechanical energy
decreasing maintenance for continued operation. Figure 1 shows a
Clapeyron diagram illustrating an adsorption refrigeration cycle.
Bill of Materials
Acknowledgements
References
Thanks to Dr. Alex Yokochi, Justin Pommerenck, Peter Kreider,
Andy Brickman, & Dr. Philip Harding.
The project objective is to complete a set of plans, instructions, and bill of materials for a low cost solar
thermal ice production system purposed for vaccine storage without electricity. The design will produce 2 kg
ice/day to keep a 2 L refrigerant space between 2 and 8 ˚C for vaccine storage. Experiments were performed
for each of the four thermodynamic saturation steps: desorption, condensation, evaporation, and adsorption.
An adsorbance ratio was determined to be 358 g methanol/kg and 253 g ethanol/kg. A 95 % confidence
interval of 46 g methaonl/kg biochar and 52 g ethanol/kg biochar was determined respectively. A 36 cm air
cooled 5 mm diameter copper tube condenser was calculated to be sufficient to condense methanol vapor.
Evaporative cooling experiments were performed by utilizing two methods: forced convection and a vacuum
assembly. The vacuum assembly was able to cool water to 7 ˚C at a rate of 2.4 W while the forced convection
method cooled water to 0 ˚C at a rate of 32 W without ice forming.
Ice Production
Biochar (adsorbent) • Charcoal created by pyrolysis of biomass
• Supplied by Pacific Northwest Biochar
• Widely available in developing countries
• No chemical additives which can interact in
the system
Methanol (adsorbate) • Produced from the fermentation of biomass
• Also known as “wood alcohol”
• Heat of Vaporization: 1200 kJ/kg
• Boiling Temperature: 64.7 ˚C
Adsorbate Path • BC: desorption of adsorbate
from adsorbent due to solar
radiation
• CD: condensation of desorbed
adsorbate
• DA: evaporation of adsorbate
from evaporator
• AB: readsorption of adsorbate
by adsorbent
Forced convection was
employed to increase
the evaporative cooling
rate of water. 250 mL of
water was cooled at a
rate of -1.9 ˚C/min, which
corresponds to a heat
removal rate of 32 W. At
10 minutes, 0 ˚C was
achieved and sustained
for 20 minutes where 115
g of ice was expected to
have formed.
A vacuum was implemented to create a pressure driving
force. The cooling rate was determined to be -8.3 ˚C/hr
for methanol and -9.6 ˚C/hr for ethanol. Further cooling
was not attained due to evaporated alcohol mixing with
the water.
Project Objective
Material Cost Plywood (21"x 20"x1/4") $ 1.25
7 feet of 2x4 $ 2.25 Spray Paint $ 4.00
Caulking $ 2.00 Valves (2) $ 7.00
ABS tubing $ 3.00 Copper coil $ 9.00
Biochar Free Methanol $ 5.00
Styrofoam Cooler $ 5.00
Total Cost $ 38.50
Develop a low cost solar thermal ice production system to refrigerate
vaccines in developing countries utilizing adsorption/desorption cycles.
Figure 3: Vacuum driven evaporative cooling
Figure 2; Forced convection evaporative cooling
Figure 4: Attempted system Integration results
Methanol
T = -8.3t + 18.0
R² = 0.9643
Ethanol
T = -9.6t + 16.3
R² = 0.897
0
5
10
15
20
0 1 2 3 4 5 6 7 8
Tem
per
atu
re (
oC
)
Time (hr)
Methanol Temp
Ethanol Temp
Figure 1: Adsorption refrigeration cycle
[1] Dieng, A. O., & Wang, R. Z., 2001. Litterature review on solar adsorption technologies for ice-
making and air-conditioning purposes and recent developments in solar technology. Renewable
and Sustainable Energy Reviews, Vol 5, page 331.
[2] M. Li, et. al. 2004 Development of no valve solar ice maker, Applied Thermal Engineering, Vol
24, Issues 5–6, Pages 865-872.
[3] Vasta, S., et al. 2008. An Adsorptive Solar Ice-maker Dynamic Simulation for North
Mediterranean Climate. Energy Conservation and Management, Vol 49, Pages 3025-3035.
[4] Sumathy, K., Zhongfu, Li., 1999. Experiments With Solar-Powered Adsorption Ice-maker.
Renewable Energy, Vol 16, Pages 704-707.
The cost of construction of one ice-production unit is as follows:
Adsorption/Desorption
Three adsorbance tests were run to determine an adsorbance. Methanol
and ethanol was boiled and passed through a biochar-packed column.
The adsorbance ratio was determined to be 358 g methanol/kg and 253
g ethanol/kg. A 95 % confidence interval of 46 g methaonl/kg biochar
and 52 g ethanol/kg biochar was determined respectively.
Table 1: Methanol/biochar adsorbance results
At 30 minutes, 100 mL of methanol was added in an
attempt to completely crystalize the water. No ice was
visible. Ambient heating was believed to have
overcome the evaporative cooling, melting the ice.
“Sandbox” Collector
• 2.25 x 2.25 m wood
frame with acrylic cover
• 23 kg biochar
• 900 mL methanol
Vaccine Storage
• 2 L stainless steel
Evaporator
• 28 qt Styrofoam cooler
• 2 L copper evaporator
Condenser
• 36 cm air cooled 5 mm
diameter copper tube
Overall System
biochar
methanol
𝑄𝑐𝑜𝑛𝑣,𝐻𝑥 = ℎ𝐴∆𝑇 ℎ𝐿
𝑘= 𝑁𝑢 = 0.52𝑅𝑎0.25
𝑄𝑟𝑎𝑑,𝑠𝑢𝑛 = 𝜖𝐴𝜎𝑇4
𝑚𝐸𝑡𝑂𝐻∆𝐻𝑣𝑎𝑝,𝐸𝑡𝑂𝐻 = 𝑚𝐻2𝑂(∆𝐻𝑓𝑢𝑠,𝐻20 + 𝐶𝑝,𝐻2𝑂∆𝑇)
Thermocouple 1
T = -1.87t + 19.5
R² = 0.9502
Thermocouple 2
T = -1.84t + 19.4
R² = 0.9899
-5
0
5
10
15
20
0 10 20 30 40 50 60
Tem
per
atu
re (
oC
)
Time (min)
Thermocouple 1
Thermocouple 2
The water and air temperature of the sealed vacuum
container during the evaporative cooling experiment is
shown in Figure 4. 0.5 kg of biochar was used to adsorb
the evaporated methanol. The goal of the experiment
was for the biochar to adsorb the evaporated methanol
and inhibit the alcohol mixing with the water.
Additionally, the successful adsorption would be the first
step in system integration.
Ethanol Adsorption (g/biochar kg)
Average 253
Error +/- (95% CI) 52
Methanol Adsorption (g/biochar kg)
Average 358
Error +/- (95% CI) 46
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