Technology Comparison

Solar Powered Coffee Maker School of Chemical, Biological, and Environmental Engineering

CBEE

Acknowledgements: Dr. David Hackleman, Dr. Philip Harding, Andy Brickman, Nicolas Sitts, Rainwater Sterilization Team

Motivation • Low efficiency of solar cells with low conversion efficiency • Direct conversion of solar radiation to thermal heat • High efficiency solution for portable coffee production

Objective • Develop and construct a portable prototype for coffee production • Capable of producing an 8 oz. cup of coffee within 15 minutes • Propose refined design

Experimental Results

Portable Design

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Tem

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re (

°C)

Time (min)

Without black paintWith black paint

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5:00 AM 8:00 AM 11:00 AM 2:00 PM 5:00 PM

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o M

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1 P

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Inci

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Sola

r R

adia

tio

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W/m

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Time of Day

Incident Solar Radiation

Time to Make 1 Pot

Umbrella Design A umbrella will be constructed with a reflective inner lining to use as solar collector.

Design • Specially shaped solar collector focuses light off center • Tripod mount for coffee pot to allow for terrain adjustments • Adjustable collector mount allows for easily adjusted angle

𝑚𝑤 = mass of water in pot 𝐶𝑃 = heat capacity of water Δ𝑇 = change in water temperature 𝑚𝑒 = mass of water vaporized Δ𝐻𝑣𝑎𝑝 = heat of vaporization of water

𝑡 = time to make coffee 𝐼0 = incident solar radiation 𝐴𝑐 = area of collector

Useful = 𝑚𝑤𝐶𝑃Δ𝑇 +𝑚𝑒ΔHvap= 54.4%

Radiative = 𝑡𝐴𝑟𝜖𝜎(𝑇𝑟4 − 𝑇𝑠𝑘𝑦

4 ) = 4.3%

Convective = 𝑡ℎ𝐴𝑟(𝑇𝑟 − 𝑇∞) = 12.2%

Material = (1 − 𝜌𝛼) = 9.8%

Other = 19.4% • Geometric Loss • Conductive losses • Assumptions made

for values in other equations

𝜌 = reflectivity 𝛼 = absorptivity ℎ = convective heat transfer coefficient 𝐴𝑟 = area of radiation 𝜖 = emissivity of surface 𝜎 = Stefan-Boltzmann constant 𝑇𝑟 , 𝑇∞, 𝑇𝑠𝑘𝑦 = surface, ambient, and sky

temperature

Energy used to heat and vaporize the water

Team: Sam Callen, Jared Fitzpatrick, Yuta Sugimoto,

Alex Yunker

Sponsored By: Dr. David Hackleman

Figure 1: A graph comparing no coating on the moka pot to Thermalox 250 coating. The paint allowed the water to change 60 °C in 8 minutes versus 55 °C change over 50 minutes.

Figure 2: A graph showing the change in incident solar radiation throughout the day and the time to make a pot of coffee at those times.

Solar Collector • Cheap • High efficiency • Portable • Limited purposes • Limited coffee pot design • Difficult to set up

Solar Panel • Expensive • Low efficiency • Requires installation • Multiple purposes • User-friendly

Propane stove • Cheap • Portable • Easy to use • Limited purposes • Requires fuel • Limited fuel carrying capacity

References Sitts, N. et. al. Solar Steam Generator for Peppermint Oil Extraction. Rep. N.p.: n.p., 2012. Print. Kreith, F. et. al. Principles of Sustainable Energy. Boca Raton, FL: CRC, 2011. Print. Welty, J. et al. Fundamentals of Momentum, Heat, and Mass Transfer. 5th ed. Hoboken: Wiley, 2008. Print.

Image Sources Moka Pot: Wikipedia Parabolic Reflector: http://www.weule.com Hiking Coffee: http://www.smart-hiking-and-camping-tips.com Solar Panels: http://csirosolarthermal.files.wordpress.com Propane Stove: http://www.sail.ca Umbrella: http://aliexpress.com

Front View

Back View

Kite Design An oval reflective fabric with pouches on the backside for supportive rods which provide rigidity and curvature.

Total = 𝐼0𝐴𝑐𝑡