Final Project Documentation

In the past few decades, we have witnessed huge transformations of every day things around us, specially in their physical sizes. A lot has changed from heavy unmovable space-eating giants into highly mobile portable things that fit well in our pockets or backpacks. Computational devices are a prime example for this transformation.

Surprisingly, refrigeration hasn’t evolved into a such highly portable form yet. There is nothing  we can carry in our backpacks when we go for an outing to chill our canned beverages or bottles of water. To this end, in this project I propose a cooling mechanism which uses the compressed air as the coolant. If successful this mechanism would enable building portable cooling devices to chill beverages “on-demand” within few minutes. To complement our main theme of “Heat for good”, I decided to present this idea as  solar powered chiller, which uses the power generated from solar panels to compress the air.

The cooling mechanism of this device is based on Amontons’ Law of Pressure-Temperature : The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas’s absolute temperature.

With this theoretical back ground I tested the practical feasibility of this system using a simple setup. My test setup was consisted of DC air compressor and a copper tube- one end connected to the compressor. The other end had a valve.

Mechanism: 

  • Air-compressor pumps the air to the copper tube and increase the air pressure inside the tube.
  • After the inside air pressure reached a desired level,  user open the valve allowing the air pressure to decrease drastically resulting a temperature drop. This results a temperature difference between the liquid(beverage/water) and the air inside the copper tube. Therefore a heat transfer will happen from the liquid to air through the wall of the copper tube.

After several failed attempts I was able to use the system to reduce the temperature of water (around 750ml) from 2C degrees. But I couldn’t reproduce the same results because of the problems I had in my setup.

After this initial experiment, I realised even though the concept of the system is somewhat formidable, building a functional prototype is beyond the DIY level because of the following reasons.

  • Compressor draws around 5A current which is hard to supply from Solar panels.
  • Difficulties in making the copper tube air tight at the two ends
  • Difficulties in re-shaping of the copper tube to have a coil shape

Even though, making of a functional system is not feasible, I believe this idea has a potential of becoming a reality at industrial level with tailor-made components and techniques.  Because of this, I shifted my focus to speculate on future design possibilities through the following non-functional prototype.

unnamed

 

Final Project Status Update

My initial idea for the DIY Science final project is to build a Solar powered chiller using compressed air. Main idea here is to implement an experimental setup since this idea is facing a heap of implementation challenges.

I received the components needed in the second week of November- a copper tube and a DC air compressor. I tested the practical feasibility of this system using a simple setup. After several failed attempts I was able to use the system to reduce the temperature of water (around 750ml) from 2C degrees. But I couldn’t reproduce the same results because of the problems I had in my setup.

After this initial experiment, I realised even though the concept of the system is somewhat formidable, building a functional prototype is beyond the DIY level because of the following reasons.

  • Compressor draws around 5A current which is hard to supply from Solar panels.
  • Difficulties in making the copper tube air tight at the two ends
  • Difficulties in re-shaping of the copper tube to have a coil shape

Even though, making of a functional system is not feasible, I believe this idea has a potential of becoming a reality at industrial level with tailor-made components and techniques.  Because of this, I shifted my focus to speculate on future design possibilities rather than making a fully functional system.

Solar Powered Chiller

For the final project I’m planning to build a Solar powered chiller to complement our main theme of “Heat for good”. Chilling canned drinks or other beverages is a common need of many people specially when they are going out for an outing in a hot environment. In this project I propose a cooling mechanism which uses the compressed air as the coolant and plan to build an experimental prototype. If successful this portable device will be able to chill beverages “on-demand” within few minutes and it will take the burden of carrying heavy mobile refrigerators or cooling boxes off while you are enjoying outdoors.

This proposal is largely motivated by Mitchell Joseph’s work on building a self chilling can.

Self-Chilling can
Self-Chilling can

Theoretical background: 

Amontons’ Law of Pressure-Temperature : The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas’s absolute temperature.

Proposed Setup:

copper

Mechanism: 

  • The Solar powered air-compressor pumps the air to the copper tube and increase the air pressure inside the tube when it is exposed to the sun light.
  • After the inside air pressure reached a desired level, user can place the drink-can inside the coiled copper tube. (See figure)
  • Then user removes the cap allowing the air pressure to decrease drastically resulting a temperature drop. ( See the theory) This results a temperature difference between the drink-can and the air inside the copper tube. Therefore a heat transfer will happen from the canned drink to air through the wall of the copper tube. An insulating material will be used to cover the copper tube from outside environment to eliminate the heat transfer to the outer environment.

Experimenting “Kiribath”

“Kiribath” (kiri = milk, bath = rice, hence milk rice) is a traditional Sri Lankan dish made from a special kind of rice called “Kekulu”. Be it rich or poor, Kiribath is an essential dish for any special moment in Sri Lanka, specially in celebrating the Sinhalese New Year. Kiribath is cooked and served as the first meal after the dawn of the new year.

Sri Lankan traditional new year dining table featuring "Kiribath".
Sri Lankan traditional new year dining table featuring “Kiribath”.

To cook a proper kiribath dish we need following essential items; Kekulu rice, coconut milk with right amount of thickness, clay pot and firewood hearth. Since, it is hard to find these exact items in this part of the world, I did an experiment on cooking kiribath using Basmathi rice, canned concentrated coconut milk and a rice cooker.

IMG_20151019_184428

Even though, basmathi rice is somewhat  similar to Sri Lanka kekulu rice in physical shape, kekulu contain higher amount of water in them. Therefore I made a (kind of) calculated adjustment to the recipe increasing the amount of water per cup of rice. Despite of not having the perfect conditions such as controllable temperature, clay pots, correct kind of rice and fresh coconut milk I was able to cook a kiribath dish which is somewhat similar to what my mom makes back home.

IMG_20151019_191213

A feature of a correctly cooked kiribath dish is the ability to cut them into trademark diamond shaped smooth pieces. My kiribath pieces wasn’t the best when it comes to shape, but they were almost there.

IMG_20151019_192508

Through this experiment I realised that the correct conditions, right materials and equipment are key requirements for making a perfect kiribath. Anyway, the kiribath made with the stuff we have here wasn’t too bad both in shape and taste. It was an attempt to be proud of, at least until I hit an authentic Sri Lankan kitchen again!

Bio indicators

Since I’m still new to Phoenix, I have interviewed one of my friends, a resident in Phoenix since birth to get an idea about local bio indicators. She mentioned about the activities of mosquitoes as an indication of rain. According to her, mosquitoes come out noticeably in numbers few hours before a rain. Personally I have neither experienced this in last two months here in Phoenix nor in places I lived before.

But I have a similar experience in Sri Lanka with a bird species called Hirundo rustica. In singhalese we call it “wahi-lihiniya” which means rain bird. They started to fly as groups indicating a rain is coming soon. According to my experience this is kind of a reliable indication.

Further, I have gone through a scholarly article on using  Ant groups as bioindicators of Forest Health in Northern Arizona Ponderosa Pine Forests. According to them the size, kind and the activities of the ant groups can be used as indicators to measure the severity of the disturbances happened to the forest eco system as results of wildfires.

Unfortunately I was unable to experience any bio indicators specific to the Phoenix area by my self yet.

Soil System

Composition and properties of the soil directly influence the successful growth of any plant. Different plants need different soil conditions. In high scale commercial farming, experts measure and maintain the the quality of the soil to get better results.

Even at the domestic level, gardeners and farming hobbyists have the ability to measure the properties of their garden or backyard easily, thanks to the simple soil test kits. These kits are easy and simple enough to use without any expert knowledge and pretty accurate given the small scale used. In spite of the easy operation, I felt some people may find it difficult to relate the results of these tests to what they want to plant. Simply- “ I got dark green for my pH test and I want to plant an apple tree. What should I do?” Therefore in my project I propose a way of simply representing these information in a tabular form.

As a part of this information base I created the following table to be used with the Rapitest ph test kit as an example.

Screen Shot 2015-09-29 at 11.45.10 AM

Arduino based temperature sensing

For this project, I used an Arduino Uno board and  MCP9808 heat sensor from adafruit. In the firmware I used Adafruit_MCP9808 library provided with the sensor and Arduino wire library for I2C  communication. With this setup I was able to get the temperature reading from the sensor through serial monitor without a trouble.

IMG_20150922_232026

Next part is to visualize the temperature reading meaningfully. I decided to try out a very simple mechanism to provide a visual expression about the current temperature. Here my goal wasn’t to visualise the exact temperature value, but to provide a sense of in which range the temperature is. Derived from the previous work “Unlocking the Expressivity of Point Lights” by Harrison et al, I decided to use a single LED to create a temperature visual expression.

I modulate the temperature reading to a square single as follows and send it to the LED. In my experiment I used 110F as the upper limit.

pulse width = (110- temp_reading) * 10

wave

So, the LED will blink faster as the temperature increases and slower as the temperature decreases.  

After few experiments with different temperatures (on top of my coffee cup, inside a ice cup and in normal room temperature) I learned this method is capable of expressing temperature levels, but human eye is not capable of identify the change of the blink rate when it increases gradually.

So in next steps I will need to try few other blinking patterns as Harrison suggested going beyond directly modulating to the pulse width in order to provide a rich visual expression of temperature using this simple method.

Heat, Life and Leisure

IMG_3583

Last Saturday afternoon, I went to “Tempe beach park” to conduct a semi-structured field study about the effects of heat on  leisure activities of the people in Phoenix area. By the time I entered the park the temperature was around 105 F (Source weather.com). Surprisingly, a considerable amount of people (around 20) were there mostly Kayaking on the lake. Another set of people were fishing under the rail bridge. A cyclist or two were rarely seen riding along the jogging path. I hardly saw any joggers or runners at that time. Quite understandable!

I met a set of teenagers doing a photoshoot. I asked them about how they experience doing photography in the heat. They said “Normally we don’t go out this time of the day, specially for photo shoots, but we have to do this shoot as soon as possible. So we came. It’s really hard to concentrate on what you do in this heat. Normally we prefer early morning.”IMG_3523
A couple, in mid sixties I would say, were fishing under the rail bridge. They happily shared their experience with me. “This is our hobby, we come here regularly. We are natives, so the heat doesn’t effect us. We can do fishing or camping any time of the year, heat is not a problem for us. Even in 120 F we can do this, because we are natives.”

They sounded like native “Mercurians” 😉IMG_3533
Then I talked to a couple, who brought their dog for a walk. “We bring her (the dog) out at least twice a month. In this time of the year, it is hard to go out with this heat. But we do this because it is good for her. Normally we come late in the evening.”

She must be a lucky dog!IMG_3569

I decided to stay a bit longer until sunset to observe more activities. So I started doing my favourite leisure activity – photography, and the “try” phase of the study. Heat kept on bothering me not allowing me to concentrate on what I’m capturing. Unlike other days, getting under a shade was my main target, than going for the best angles. Anyway thanks to the telephoto lens, I could take some long distance shots from under the shades of trees and bridges 😉 IMG_3635 IMG_3648
After few hours, the sun started to die allowing more people to the park. The Number of cyclists, kayakers and joggers started to grow. Interestingly, I saw parents bring their kids to the park in the evening. There were no kids in the park at the the time I entered.IMG_3644 IMG_3637

From this study I learnt the following key points.

  • People prefer to come to the park early in the morning or late in the evening to avoid the heat in the day time.
  • But still some people seem to enjoy their leisure activities even in the heat. Especially the kayakers.
  • And in my personal view, the amount of people I saw doing outdoor workouts, was very low compared to the other parts of the world I’ve seen. Heat could be a possible reason for that.

At the end, the sun started to set behind the bridge, compensating me with a wonderful view for all the trouble it gave me since afternoon. IMG_3675Thanks for reading!

HEAT is COOL!

Having to carry out daily activities under the flashing solar rays is not the nicest thing you experience in an “Arizona Summer”. My first impression, after arriving here was “OMG! this is an oven”. But later I realized there is a cooler side of being closer to sun than others. (yeah, few inches to Mercury!). The very same solar rays trying to bake us off can be used to charge our mobile phone or laptop, or may be light up our whole apartment without burning Petroleum. Yes, the Heat is Cool, when it gives free energy!

Idea

The idea of my project “Heat is Cool”  is to create solar sensitive self illuminating screen prints to be used as a simple awareness platform to indicate the potential locations to make solar powered energy. The message printed on the material, “Cool” in this case, starts to illuminate by changing to a contrasting color when exposed to the sun. “Hey, isn’t it cooler to put some solar panels here?”

Process

  • Cut the stencils using the vinyl cutter machine.
  • Create self illuminating ink by mixing white (or clear) base paint and solar dust.

    White colour base and Solar dust
    White colour base and Solar dust
  • Print on a thermo-chromic material which changes to a colour different from the illuminating colour when exposed to sun.

    Thermo-chromic fabrics
    Thermo-chromic fabrics

Results

IMG_20150906_165839
Not exposed to the sun
IMG_20150906_165421
Exposed to Sun
IMG_20150906_165459
exposed to sun

I tried few combinations to get the “self-illuminating” effect. And third one was the closest to my expectation.

Potential (if everything goes well 😉 )

_MG_5944 copy2

Thanks for reading, stay cool!