Solar Cooker Stand Initial Thoughts

To my devoted readers -

I have been sick for the, so I haven't been able to publish my most recent blog posts. Fortunately for all of you, they will hopefully be online by tomorrow!! In the meanwhile, please enjoy the notes from my initial brainstorming session with Eva for our final project. We are working on how to design and build a cheaper and simpler solar cooker stand. Click here to see what we have so far.

See you soon!!

Ananya

Biodigesters

Today in class, Eva and I learned about biodigesters and how they can be used to create methane in an eco-friendly manner, which can then be used for cooking.

Some of our starting points when looking up biodigestors: https://www.uwosh.edu/sustainability/internal-documents/materials-by-topic/uwo-biodigester-fact-sheet

-biodigestor fact sheet

-University of Wisconsin

-simple explanation of what a biodigester is

-explains anaerobic digestion

http://www.src.sk.ca/about/featured-projects/pages/biodigester.aspx

• “A biodigester is like a mechanical stomach. It is fed with organic material, which is broken down (decomposed) by micro-organisms (bacteria) is an oxygen-free (anaerobic) environment to produce a renewable energy called biogas (methane and carbon dioxide) and other material that is mainly used as fertilizer.”
• video on how a biodigestor works

http://www.fao.org/docrep/w5256t/w5256t06.htm

-brief history of fuel-related issues and hazards around the world

- two main designs

*the floating canopy (Indian): "consists of a drum, originally made of mild steel but later replaced by fibreglass reinforced plastic (FRP) to overcome the problem of corrosion. The reactor wall and bottom are usually constructed of brick, although reinforced concrete is sometimes used. The gas produced is trapped under a floating cover which rises and falls on a central guide. The pressure of the gas available depends on the weight of the gas holder per unit area and usually varies between 4 to 8 cm of water pressure. The reactor is fed semi-continuously through an inlet pipe, and displaces an equal amount of slurry through an outlet pipe"

*fixed dome (Chinese): "consists of a gas-tight chamber constructed of bricks, stone or poured concrete. Both the top and bottom are hemispherical and are joined together by straight sides. The inside surface is sealed by many thin layers of mortar to make it gas-tight. The inlet pipe is straight and ends at mid-level in the digester. There is an inspection plug at the top of the digester to facilitate cleaning, and the gas outlet pipe exits from the inspection cover.The gas produced during digestion is stored under the dome and displaces some of the digester contents into the effluent chamber, leading to gas pressures in the dome of between 1 and 1.5 m of water. This creates quite high structural forces and is the reason for the hemispherical top and bottom. High-quality materials and expensive human resources are needed to build this kind of digester”

-both designs are flawed/expensive

-full material list of needed supplies for “low cost” biodigester

-outlines methodology for choosing a location and selecting appropriate materials

http://extd120bidigester.blogspot.com

blog post of ENGR120 students from Spring of 2013

looked at if it would be feasible to create more biodigesters for Sabana Grande

come to the conclusion that it would not be feasible or very beneficial

https://prezi.com/r8irrknjqvzq/break-even-biodigester-assumptions-and-calculations/

presentation by ENGR120 students from Spring of 2013

explains the assumptions they made when going through their calculations

demonstrates that with their assumptions, biodigesters break even with propane in the long run

How biodigesters work:

-Takes human/animal waste and encloses it to decompose

methane is released

methane travels upwards

fills bag with gas

gas is routed to be used for cooking fuel

Questions to ask members of the community:

1. what is your current source of energy for cooking
2. Is your village/farms spread out over a lot of space?
3. Do you have farms/livestock?
4. Are you comfortable cooking with methane from animal and human waste?
5. What is your current fuel source for cooking?
6. Is this something you would want to change?
7. How much time procuring fuel for cooking per day?
8. Is there space for a biodigester?
9. Who does the cooking?
10. Who gathers fuel?
11. How much money do you spend on fueling cook-stoves/lights?
12. Follow up--how much of your income go towards fueling your cook-stoves/lights?
13. How far apart are homes in the village?
14. Could members of the community share a biodigester?

Pros to having a biodigester:

• very environmentally-friendly
• can be made using local materials
• there will never be a shortage of human/animal waste to use as fuel

Cons to having a biodigester:

• very expensive
• as of right now, only works on a large scale

Design specifications:

• must have two chambers - one for fermentation and one for storing methane
• the chamber for storing methane must be close to the kitchen/house
• must be durable
• must include bacteria to ferment waste in the first chamber
• must be large enough to work but small enough to be on a household scale
• SAFETY

Our brainstormed prototype: There are two oil drums - one to hold manure and contain the fermentation process and another to store the methane produced and direct it to a cookstove. A flexible rubber inner bag within the drum used for storage will act as a diaphragm and expand and contract in conjunction with methane levels. We’d then pipe this gas into a cookstove for use. It could be buried for more year-round reliability and storage or it could be above ground for a simpler, more immediate solution.There would be some sort of pressure-sensitive valve to control the flow of gas outside of the storage drum. This valve would make the prototype much more safe - by including a stopper, we are ensuring that methane would not leak out of the device and accidentally ignite.

A 10 to 15 meter^3 biodigester is enough to 
power a two ring stove and a light. (http://www.slideshare.net/raddieman/an-introduction-to-biodigestors)

a basic example of a biodigester >>>>

Gravity-Powered LED Lamp

Assumptions:

• The LED bulb used is sixty watts, the same power as an average lightbulb.

Assuming that the average lightbulb needs two 1.5 volt batteries (so three volts total) to run for twelve hours, then in order for a bulb to run for thirty minutes, it would need .0125 volts. Using the equation R = (V^2)/P, R effectively equals 0. That's a little bit of a dead end, so instead, I'm thinking about how 9.8 m/s^2 is the magnitude of gravity. If one newton is the amount of force needed to raise a kilogram one meter against gravity and joules are newtons multiplied by meters, then the question becomes how many joules are needed to power a lightbulb? Well really, since lightbulbs' power is measured in watts and watts are joules per second, then a lightbulb would take sixty joules (at minimum) to be powered. Therefore, one would need sixty newtons to power a sixty watt bulb. This means that sixty kilograms would be needed to power this LED bulb.

This product seems viable because the magnitude of gravity remains constant no matter what, so the rocks would be enough to power the light no matter what the conditions outside. It is also viable because it does not rely on the weather conditions outside functions (unlike turbines or solar panels), so it can work every day throughout the year.

Time Management Reflection

Having two large assignments due on the same day did not worry me very much. Part of it was the fact that one of them was an individual assignment - I could stay behind after my group had finished working on our sharps container and work on my lantern at my own pace. Another part of it was the fact that I could come in to the engineering lab whenever I wanted as long as I brought a buddy with me, so I did not have to worry about rushing over right after class to use the lab while it woulds still be open.

I am used to group projects taking longer than individual projects normally would. It is often very difficult to find a time when everyone in the group can meet, decide on a single way to move forward, and ensure that everyone is working an equal amount. However, I did not expect the individual project to take so long. In high school, the rules were much more explicit: I had to follow the steps given to me in order to achieve the desired result. With this lantern project, though, I did not have any clear ideas of how I was going to start it. I finally figured out what I was doing through a murky-ish path or trial and error and so when the lantern finally worked, I was very excited.

Next time, I will definitely get in the lab and start playing with things to get a sense of what I want to do. I found that when building something, one can only do so much without actually testing out materials and seeing what works, so I will not try and make as many sketches and diagrams as I did for this project without setting aside some time for trial and error. I will also continue to exploit the fact that the lab is (technically) open at all hours so that there will be less pressure to finish things quickly.

Sharps Reflection

Switching into ENGR 120 halfway through the first week of school and missing a class meant that I never got formally introduced to this project. However, my amazing group-mates quickly caught me up to speed and showed me what their initial ideas were. Basically, the goal was to design an alternative container for the "sharps" (broken blades, dull blades, etc) produced in class to be disposed. My group (Ann, Diana, and Kavi) decided that the safest way to dispose of sharps would be to avoid touching them at all - we quickly determined that our sharps container would need to break off sharps as well as store them.

In order to do this, we came up with a design that includes a reinforced slot with which one may break off the blade of an Olfa knife. Our design also includes a diagonal piece of metal glued onto the  side of the can
just under the slot to redirect the falling blade as it breaks off. This piece was put in place to ensure that if the container is dropped, a blade cannot fall back out if it happens to randomly fall at the correct angle. Instead, the slit is directly shielded by the piece.

We used a chickpea can for the container itself because we found the metal to be strong enough that an Olfa knife blade could not cut through it (even if that blade is sharp and has pressure exerted on it). We also kept in mind the project's theme of sustainability - because the entire contraption is made of one material (metal), the whole thing can be melted down without having to open it and take out the blades.

The main challenge we had with this project was that fact that we were not able to use the soldering iron. Being able to use it would have made the process significantly easier because then, we would not have had to use hot glue to secure all of the pieces together and the device would truly be made out of one material. We were lucky, though, because the rest of the project went fairly smoothly. The contraption we came up with snaps off the blade without one having to exert much pressure on it and the blade stays in the can, even when it is flipped upside down. I think we came up with a really elegant solution to a problem that the lab might face and I could definitely see the can being used in class during a work day, where it would just be set on the table and anyone who needs to use it would be able to.

                                       Side view                                                   Top view
 Until next time,

Ananya

Lantern Reflection

When the class was first told that we had to build a lantern using a resistor, a nine volt battery, and an LED bulb, I was nervous. How could I build anything so complicated that it required a familiarity with basic electrical engineering? I thought that there was no way that I could handle the monumental task of actually creating something (that worked) from scratch.

I was wrong. I ended up building a flashlight. I used a juice bottle that I had lying around (which I drank for science, of course) as my body. I took off the plastic wrapping, washed it out, and let it air-dry. While that was going on, I did a few calculations. Using Ohm's Law, I determined that I would need a resistor of at least 450 ohms so that the bulb didn't burn out. I would also need to fashion some makeshift wires out of metal so if the battery was at the bottom of the bottle, the bulb could stick out of the top. I used aluminum foil for those - it turned out to be highly malleable and easy to work with, and once I had wrapped my "wires" with electrical tape to secure them, they proved to function effectively.

The circuit itself was not very difficult to build because it had only three main components: the bulb, the battery, and the resistor (which ended up being 470 ohms because there was no resistor in the lab that was exactly 450 ohms). However, incorporating a switch turned out to be an interesting challenge. I decided to use a brad fastener as mine because it is sturdy and long. To turn on my lantern, one must wrap the exposed aluminum foil around the brad and the LED will shine brightly. I also faced a challenge in trying to intensify the bulb's light, but then I noticed that the aluminum foil I was using had a particularly reflective and shiny side. I exploited this by wrapping it around the mouth of my flashlight so it surrounded my bulb. In doing so, the light reflects off of the foil's surface and focuses in a singe direction (ahead of the bulb). In this sense, it is a true flashlight. I imagine that it could be used to light one's way in a very dark night. The benefit of this flashlight versus a regular one is that this one is much lighter and if need be, one can shake it around to make noise and scare away any animals or other predators. The bottle can also be crinkled to make a loud noise without damaging the quality of the light itself. Going outside in the middle of the night is easy because the light stays on if the aluminum foil is wrapped around the fastening brad.

This is my flashlight! I spiced its body up with some sharpies, but other than that, the design is purely functional. I am very proud of how I was able to pull it together, especially since I would not have imagined that I would have been able to as little as two weeks ago. After five very productive hours, here is my work:

Until next time, 

Ananya 

Keychain Reflection

On Friday in class, we learned how to use two power tools (a bandsaw and a drill press) and tried them out on our own by making keychains. For both of the machines, we are only allowed to use them when we are under Amy's or Jamie's direct supervision and if we are wearing our safety goggles.

To use a bandsaw, one must first determine if the material that is to be cut is thick enough for the machine to cut through. In order to cut through a material, the material must be at least three teeth on the blade tall and it can only be wood, plastic, or some types of metal (aluminum is fine; stainless steel is not). First, one must adjust the height of the safety foot so that the material can fit in between the table and the foot comfortably. To do so, there are two knobs on the back of the machine - one is used to loosen/tighten the safety foot and the other is used to draw it up or down. After it has been determined that the drill press is suitable for cutting the material and that the safety foot is properly placed and secured, one must ensure that their fingers are not in or around the yellow circle near the blade and then they must turn on the machine. Now, to guide the material toward the blade, it would be a bad idea to use one's own fingers because if those are cut off, it would be very painful and since we are not starfish and our limbs do not grow back, one would have to live a life without fingers.

In order to avoid this terrible fate, one must use a block of "sacrificial wood" to push the material that will be cut towards the blade. Using this means that if anything were to go wrong, the wood would get cut and not one's own fingers. Crisis averted. Mission accomplished.

Some benefits to using a bandsaw are that one can cut a large variety of materials with a single tool. The bandsaw also cuts quickly and cleanly. However, it cannot cut any dramatic curves - the blade would brake if one tried to cut out anything more than a slight curve. Another drawback to the tool is that it can dismember one's body via accidental amputation of the fingers.

To use a drill press, one must make sure that the drill in the machine is the size they want their intended hole to be. To replace the drill, one must use a monkey wrench-like tool to unscrew the teeth in the machine and release the drill in place and then one must put the new drill bit in and tighten the teeth using the same tool. Then, put the material which will soon have a hole in it into a vice so that it does not move around and so that one's precious fingers can be saved in case of any accidents. Finally, turn on the drill press and slowly lower it into the material and then bring it up. This allows the material being drilled away to escape from the drill bit. Continue this process until the drill bit reaches the other side of the material.

Some benefits to using the drill press are that it can create holes of varying sizes, depending on the drill bit used. It can also create holes in very specific places if those places are slightly indented beforehand so that the drill bit finds them easily. However, they only make circular holes, which may not be useful for every project.

I wanted my keychain to look like a domino, but I realized that there was no "router" tool that could create grooves in the metal, so I settled for a square with two dots in it. However, due to my poor estimation skills, my square turned out to be a very clear rectangle and my dots ended up being very far away from where they would be on an actual domino. In order to salvage my masterpiece, I rounded three out of the four edges on the keychain and renamed it "one of those text message bubbles on the iPhone," which, coincidentally, it actually looks like.

The Energy Crisis in a New Light

The "Poor People's Energy Outlook 2014" really illuminates the energy crisis that we all face in a light that not all of us get to see it in. When we think of a crisis, naturally, we think about how it would affect ourselves. However, this report seeks to extend our understanding of it to include its effects on those who live in poverty and the very simple changes that could be made in order to lessen it severity. For example, did you know that about 23% of all of the soot produced in the world comes from inefficient stoves? Soot, also known as "black carbon," is the second-most powerful driving force in climate change at the moment, behind carbon dioxide. Luckily, it washes away in the rain, but if it were not created in the first place, then there would be a sizable difference in the pace of global warming. Stoves are a good place to start because we already know what fuel we can use so that they burn cleanly - alcohol, gasoline, and electricity all produce almost no unhealthy by-products. Unfortunately, most of the time none of the three are readily available in developing countries, where they would make the most impact. Before reading the report, I had thought that it was limitations in existing technology that ushered forth climate change, but that is not entirely true, which surprised me. We have the technology to reduce the amount of soot in the atmosphere by roughly 23%. However, the infrastructure is not there - people in developing countries using inefficient stoves oftentimes cannot afford the more expensive fuels or there is simply no way for them to obtain the fuels due to a lack of suppliers. Therefore, one way to help ameliorate both the energy crisis and climate change (which I did not even think of before) is to usher forth globalization so that there is enough infrastructure to spread eco-friendly resources around the world.  

A Quick Introduction

Hi everyone! My name is Ananya Hariharan and I am a first year and a prospective Political Science Major. This past summer, my parents and I took a trip around the world so that I could see what my generation will inherit as we get older. Over those sixty days, I went through a lifetime's worth of experiences. I felt the fragility of humanity's infrastructure at the hands of nature when a volcano halted all of the flights entering and leaving Indonesia, effectively bringing its tourism industry to a standstill. I felt the the incredible ability of euphoria to unite masses as the prince of Sweden married his fiancée and brought throngs of people rejoicing into the streets of Stockholm. I felt the frightening immediacy of climate change in Beijing, where the sky was so eerily white that it was as if someone had carefully constructed a city perfectly and just placed a blank piece of paper above the buildings, hoping that it would suffice. This class interests me because it directly interacts with the world that I explored - it takes a practical approach to not only maintaining, but improving the earth so that future generations can enjoy it just as we are right now. I find tracking the progression of pregnant mothers in India via improvements in portable ultrasound machines to be particularly interesting. I have never taken a class in which most of the work comprised of hands-on learning, so I am very excited to get started!