Hi guys! We're Bhoomika Mhatre and Aadish Bakliwal from India. This blog is a part of our final assessment for our elective. Hope it helps you out in one way or another or just piques your interest!
One of the assignments that we were given by our professors required us to list down five problems that we come across on a day-to-day basis that also have social importance to it. Living in my college's hostel, one of the problems that I[Bhoomika] faced was impure drinking water from the coolers on my floors. The water in my hostel has always tasted weird but there have been times when I've bought packaged water because the water from the coolers was just undrinkable. While writing that assignment, I realized that this was a problem faced by millions of people[in a more severe manner] around the world. Our next assignment was to pick out one problem from the five and work on its solution with a partner. Seeing its importance, I chose the unfiltered water problem. Aadish found my problem interesting and hopped on board with me. We were then asked to come up with solutions to this problem. Initially, we thought of 3 methods through which we could make this project a reality. First was using the properties of a LifeStraw to make a mini-filter which could be installed inside the coolers. Lifestraw does not filter out filters. The second was replicating a Slingshot water purifier. From this we got the idea of using solar heat to purify water. We could not go ahead with this as it required time, money and heavy expertise in the field of engineering- all of which we were short on. The final idea was the one that we decided to work on and that was the use of a fresnel lens. Our professors helped us come up with this idea as neither of us was aware of the Fresnel lens at that time. We have incorporated the properties of all our ideas into the final model.
What it does:-
Taking the support of a Fresnel lens and using the unique capillary action properties using a tissue paper, the device heats up the wet tissue paper [which itself is dipped in impure water] and generates steam from it. This steam is then collected and condensed to help us get pure, clean and drinkable water. We decided to go with distillation as it completely filters out every impurity in the water, including fluorides.
4 feet of PVC pipes
4 elbow joints
Glass/ glass jar
Cover cap [for the glass]
Black spray paint/ Black paint
Step 1: Setting Up the Base
To make the rectangular like base, we need four PVC pipes and four elbow joints and 1 T-joint. Cut the pipe into four pieces. The two pipes acting as the length of the rectangle must be 20cm long and the two pipes acting as the breadth of the rectangle must be 25-30cm wide. Join the pipes using the elbow as shown in the picture. One of the pipes will be cut in half [7cm each] and attached by the T-joint.
Step 2: Attaching the Fresnel Lens
Join a small pipe to the middle hole of the T-joint in a way that it's aligned with the other pipes [lying down]. Now join another T-joint with the middle hole facing upwards like in the picture. Attach another pipe which will act as a support to the fresnel lens. The length of this pipe will be decided by the focal length. Ours is around 15cm. It took some trial and error to figure it out but if the same dimensions are used the focal length shall be same too mostly. Join another T-joint to the top of the pipe. This T-joint will have a slit on one of the sides for the lens. Attach the lens to the T-joint. It is kept at a fixed angle of 15 degrees. This is the latitude of Pune, which is the city we are currently residing in. You need to figure out the latitude of the place you live in so that the lens in always aligned with the sun and all you have to do is rotate it with the movement of the sun.
Step 3: Tissue Paper Set Up
Use a small pipe of any length [6cm in pic] and cut out a V in its front. This pipe will be attached to the front of the T-joint like in the picture. This is where we'll place the tissue paper. Use the spray paint to blacken the tissue paper. You can use any method to paint the tissue black. We have used spray paint as it is easier and faster. This step is needed as black absorbs the sunlight fastest. Douse this tissue with water and place it inside the pipe in such a way that the side exposed to sun is flattened out. This is done so that we get maximum area and the tissue paper becomes thinner which fastens the process.
Step 4: Role of the Glass
When sunlight hits the tissue paper, it will heat up the paper and start generating steam. The easiest way of collecting this steam is using a glass [pictured is a glass jar]. The simple reason for this is, without an enclosed covering around the tissue, the generated steam will very easily get blown away by the wind and hence, making it impossible to collect and condense. Glass allows maximum sunlight to enter in, without making it lose its strength, and hence using a glass vessel would be preferable over any other material. Put the glass around the tissue paper pipe. The glass jar can be of any shape and size as shown in the picture, as long as it covers the area around the tissue properly, without letting any disruption of air movement or sunlight.
Step 5: Covering the Glass
Additionally, apart from just putting a glass around the tissue as shown in the previous step, we need to ensure that the mouth of the glass is properly covered as we don't want the steam to escape or air to get it since that would completely hinder the condensation process. To do that, using the cutter you can either cut a hole in the center of the lid of the glass jar according to the pipe dimensions and put it on the jar with the tissue inside. Apart from that cut a small hole at the edge of the lid to allow the condensed water to come out and get collected. That way the entire compartment within the jar is completely sealed and maximize the efficiency of the model and output of the condensation process.
Step 6: Initiating the Purification Process and Water Collection System
Once the device is all prepped up and ready, put it out in sun in the north-south direction. Adjust the Fresnel lens in such a way that the focus point of the Fresnel lens makes a clear, extremely bright dot on the tissue paper. Eventually, you will see steam coming out of the tissue paper and the condensation taking place on the glass. You'll be able to see droplets that will collect on the sides of the glass. Through the small hole on the edge of the cover that we made, which should be adjusted in such a way that the condensed water is able to come out of it by keeping it at the bottom edge of the mouth of the jar. This fresh water will trickle down to a container that we put under the glass. You can now drink this water without any worries.