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