Group 066-03: Solar Powered Water Purification: 2014

Sunday, April 6, 2014

Weekly Progress

Week One:

In week one, we decided on the project we were most passionate about and investigated the problems present with building an apparatus like this one.

Possible Problems:
Difficulty to capture enough solar energy to effectively heat a solar coil enough to boil water (this will require further investigation and experiment in future weeks)
Price of solar panels on a small or large scale
Using the apparatus when the sun goes down, which would require storage of energy

We also drew a model of all of the parts needed and created an early estimate of the price of items needed to make the apparatus.

Week Two:

After some calculations, we realized that the system containing a solar panel to heat a heating coil wouldn't work because it requires 747 watts of power to boil the water. We would be able to get 5 watts maximum from each solar panel, and the price of this system would be simply too high. We had to go back to the "drawing board".

Through some more research and discovering this video, we decided that we wanted to pursue a system using directed light from the sun at a container to achieve boiling. This decision meant that we needed to reconsider everything we had done so far.

Calculations:
Q = mcdeltaT
m = 1000 g
c = 4.184
deltaT = 60 degrees Celsius (assuming room temperature in Africa at 40 degrees C)
Q = 250,000 J

Calculating amount of output for our proposed system:
milliJoules created by our system = solar constant*Adish*Time(seconds)
solar constant = 1.361 kW/m^2 = 136 mW/cm^2
Adish = pi*r^2, we did this to simplify calculations as the surface area of a concave dish is tough to calculate
Time will be 3600 s, an hour
We decided on a dish with radius, r = 16.51 cm

mJ = 136*16.51^2*pi*3600 = 422180 J

Finding amount of water boiled with this amount of energy:
Q = 422180 J
422180 = m(4.18)*(60)
m = 1683 g/hr = 1.683 L/hr

Because we want about ten liters per 12 hour day, this is an acceptable amount of output created for our system. We intend to use this system.

Week Three:

With our general planning done, we're beginning to solidly work on designing the process. We spent this week solidifying our intended design and looking for products to buy to complete the design. We've decided that we'll be building the apparatus with the mirror out of PVC piping and using a standard aluminum cooking pot to boil the water out of.

We intend to use a tripod along these lines to hold up the aluminum pot and air duct material to direct the water vapor to another bucket, where it will condense.

We also designed the way that the aluminum pot will be refilled. We intend to use a duct reducer (this) attached to the top of the pot, where it will funnel the water vapor into the ducting. At the point where the ducting meets the smaller end of the funnel, we intend to use Velcro to attach it. This way, the ducting can be removed by the user when they need to refill the pot.

Materials along with general prices:
Heating duct material: $15-20
PVC Pipe/PVC glue (one of our group members already has this): $20
2 quart pot: $10-15
Coffee Filter/Other Filtration: Free (we have these)
Pot to hold pure water: $10
Velcro Strips: $5

Total Estimated Price: $65-70

We officially delegated the roles of the group into the following subgroups:
Building the apparatus to hold the kettle and the mirror: Greg and Malik
Creo designs of that apparatus: Greg and Malik
Building the distillation apparatus: Brian, Sarah, Billy
Calculations: Billy and Sarah
Flow chart of the major processes: Brian

At the suggestion of Dr. Herczfeld, we drew a flow chart of the major systems involved in the process.

Week Four:

This week, we're working on solidifying our designs and drawing them in Creo Parametric before beginning to build. Also, we're redoing calculations and searching for more possible downfalls of our design.

Over the past week, we received the parabolic mirror and also purchased the heating tubes and duct reducer for the final design. We plan on going to Home Depot and purchasing the remaining materials by the end of this week so we can begin building officially by next week.

We used the information provided by this website:
http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

We intend to use an infrared thermometer to measure the change in temperature between the inside and outside in order to have enough information to find the heat transfer per unit area. This will give us a good idea of how much energy the aluminum will allow to be transferred through the surface.

Also, to prepare for the build, we estimated how much the aluminum pot and water system would weigh (how much force our stand would have to hold up). The calculations are as follows (assuming 1.5 liters of water in the pot at any given time):

Total Mass = weight of pot + weight of water = 230 grams (from the website for the pot) + (1.5 Liters * (1000 mL/L) * (1 g/mL)) = 1730 grams = 1.73 kilograms

Gravitational Force pulling the pot down = m*g = (1.73 kg)*9.8 = 16.9 N

16.9 N is not a very strong force and should not be difficult to support using a simple stand made out of PVC piping.

Week Five

This week mostly involves getting the materials needed to build the apparatus. During class time, Malik and Gregory went to Home Depot to buy the PVC piping and other materials needed to begin building. Building will begin this week.

Materials Acquired:

Pictured: Heating duct material, PVC piping of multiple sizes, PVC T joints, Velcro Strips, Heating duct band

List of things to accomplish this week:

Gather materials/inventory
Build rudimentary base to hold mirror for experiments
Update Calculations
Prepare for thermometer test
Measure focal point of the mirror
Decide how to test final water quality

Week Six:

During lab period, Sarah, Brian, and William are going to work in Myers Hall on building the apparatus to hold up the pot while Malik and Gregory work on finishing their design. The Creo Parametric design is almost finished, but needs final touches.

Roles for final report:

Malik: Abstract, Problem Overview

Brian: Existing Solutions, Project Objectives

Gregory: Project Timeline, Project Budget

William: Results, Future Work

Sarah: Abstract, assist other people with any problems they have

Additional Supplies Needed:
Drill/PVC cutter
Elbow joints for PVC
More PVC (thinner than 1 inch)
Screws
Command Hooks (maybe)
Duct tape

Progress of the Sarah/Brian/William group:

Pot connected to duct reducer and heating duct

The pot, connected to a duct reducer with velcro strips and connected to heating ducts

Progress on the stand for the pot

Week Seven:

In week seven, the project has reached the point where building is the focal point of our progress. The build has been coming along fairly well, as the adjustable stand for the mirror is built.

Pictured above is the stand for the mirror, built using PVC pipe connected with PVC glue

During lab period, the group left early to go work on building the stand for the pot. In the time there, we constructed the stand, again using PVC piping and glue. We did, however, run into a problem with the size of the pot we had intended to use. It is too big, and our duct reducer will not fit onto it correctly. We intend, over the next week to check multiple shops for smaller pots that will fit the duct reducer.

Our progress on the stand for the pot:

We used PVC piping and various joints to construct the stand as shown above. We intend to drill through the T-joint in the middle to connect a system to hold up a pot once we are able to locate and purchase a sizable one.

Throughout the week, we've searched multiple stores in the local Philadelphia area for the correct size pot, but to no avail.

We intend to go as a group during week eight to search for a pot. At this point in the term, our build is virtually finished and simply requires a correct size pot, testing, and general adjustments to achieve maximum efficiency.

Week Eight:

We were unable to find a pot to buy, but we decided on a stainless steel bowl that we will cover in aluminum foil. After purchasing the bowl and the aluminum foil, we constructed the system completely, with only minor adjustments to make by the end of the term.

Here are pictures of the completed design:

The full build, completed but missing the mirror, which would typically rest on the PVC stand on the ground

Close up of the bowl, covered in aluminum foil, and the duct reducer and the heating duct that are attached to the bowl

Above view, showing how the bowl hangs and how it is fastened at the top. It is connected using ribbon (which was a temporary solution just for testing purposes, as we didn't have actual nylon rope), and at the top is fastened by tying the ribbon through a small loop of PVC.

The small loop of PVC with ribbon tied through it

Important Note:

These pictures aren't of a completely finished project, as the ribbon needs to be replaced by rope. We only used the ribbon in order to have the apparatus built in order to test it. The ribbon won't hinder the production of the build, but doesn't look professional and is considerably less durable than the nylon rope we intend to use.

Testing Progress:

We completed the project Tuesday night, and haven't been able to test yet this week. We tried a few times to use it outside, but it's been too cloudy for a reasonable test. When we tried, the sun simply wasn't shining well enough because it was obscured by clouds. We intend to test the build at the next sunny day.

Week Nine:

This week, testing is our highest priority. We really need a sunny day to test the build before week ten, and the weather forecast for the next ten days seems ominous, as virtually every day will be cloudy. We will continue to be vigilant and test whenever we can.

Also, we've purchased the nylon rope and intend to replace the ribbon with the rope tonight (Tuesday night).

The type of nylon rope we decided to use. One eighth inch is plenty of width and the weight it is supporting is far less than the 90 lbs the product says it can hold.

In order to be able to test our project, we obtained 200-watt halogen lights to simulate sunlight. Results were unfortunate, as the testing resulted in no boiling or vapors. We intend to test using actual sunlight on the next available day.

Week 10

Fortunately, sunlight was abundant early this week. Through our testing, we've discovered that while our project can heat water a considerable amount (25 degrees Celsius), it is unable to boil water, which is an integral part of the entire project.

The temperature of the water after testing (45 degrees Celsius)

The physical bubbling in the water following our testing

The full build, including mirror and clean water containing pot

Results

While the project was overall unsuccessful because it is unable to heat water effectively to boil it, it was successful in many other ways. It managed to create bubbles, which shows that with improvements to the system it could completely boil the water as intended. Also, it is a compact and portable prototype that can easily be transported, and we are even going to take it to the site of our presentation because it's compact.

Possible Improvements:

A more conductive metal container would have given us more heat transfer through the metal, which would have resulted in a higher temperature of water. This lack of conductivity could have made the difference between boiling water and just lightly bubbling water.

Another improvement we could have made would have been to purchase or construct a larger reflector, as more surface area would have resulted in more heat transfer.

Together, these two improvements could have made the difference between success and failure to boil water.

Background/Tutorial/FAQ

Background

The practice of this project involves the capturing of sunlight with a concentrator (an object that concentrates light, in this case a parabolic mirror). The concentrator will have a focal point, the point where all of the light will be pointed towards, and that will heat up the object it is aimed at.
We intend for our purificator to work in Nigeria, a country which is very close to the equator and so, has generally constant amounts of sunlight. This means that we do not have to worry about changing the tilt angle of the parabolic mirror as the day progresses. If however, we were to modify it to work in a place like Philadelphia, that would be the first thing on our list to change.
Solar energy works as follows:
The Sun creates beams of sunlight which carry energy. This energy comes in the form of thermal energy and can be harnessed as such or solar panels can be utilized to change the solar energy into electrical energy. This thermal energy can be utilized to heat objects very well, particularly if a concentrator is used. A concentrator, such as a mirror, is an object that directs sunlight towards a small area, making the collective force larger.

Definitions:

Concentrator - an object that captures sunlight (or light in general) and redirects it, making it focus on a smaller area
Thermal Energy - energy due to heat, in the case of this project this thermal energy comes from the sun and is redirected by the concentrator
Distillation - the process of separating the component substances within a liquid through the process of boiling and condensation, in this project, the boiling will be accomplished through thermal energy from the sun redirected by the parabolic mirror towards a conductive metallic pot.

Tutorials

How to:

Collect/concentrate sunlight:

To collect or concentrate sunlight, a reflective surface is required, preferably one that is curved in a parabolic way such that it can collect the sunlight and concentrate it on a single point, called the focal point. With a parabolic mirror, this is easily accomplished, as the mirror will concentrate the light on its own. We decided to buy one, not make one, because it would make the process much easier since none of us had any experience with working with glass. It was relatively easy to buy it : we got it off ebay.com.

Distill water:

Distillation is a simple process, involving boiling and condensation. It works on the principle that different liquids have different boiling points and we can use these differences in boiling point to separate them.
In order to boil the water, supply heat to a container, in this case an aluminum pot with heat applied from sunlight being redirected by the concentrator. Condensation is a little bit trickier. A tube must be attached for the boiled water to flow through, leading to another cooler, container, where the water vapor can condense and return to liquid form. A filter will be placed right before the cooler container to further remove impurities. We have hopes of using a charcoal filter with a sieve length of 0.5micrometers or less, but that all depends on the cost we accrue for other, very important parts. If we cannot, we will improvise with normal filters.

FAQs

Why did you decide to use a concentrator rather than electric solar panels?

The choice to use a concentrator to redirect the light rather than electrical solar panels to boil the water was a simple one that came down to efficiency and price.
First of all, using electrical solar panels to conduct electricity didn't make very much sense, because doing that would be converting heat energy to electrical energy just to convert it back to heat energy in a heating coil. Because the solar panels would be ineffective at efficiently converting the energy, a lot of heat energy would be lost during the conversion process. This would require us to use multiple solar panels, which was not just feasible for our design( we want to be used by a family of six).
Also, price factors weighed heavily on the decision. We did our research on the price of solar panels and the amount of energy we would need, and our calculations said that we would need many solar panels to supply enough energy to sufficiently heat up a heating coil. Each solar panel was going to be at least thirty dollars, which would have been financially impossible to accomplish for the group. The price for getting the panels was estimated to be about 2000 dollars.
On the other hand, using a parabolic mirror removed any problems with funding and also our calculations showed that it should supply ample energy to adequately boil the water.

What difficulties do you expect with executing this project?
Having an up and running solar water purificatory system should not prove to be too much of a problem. But,we do expect challenges on the way.These challenges could include finding the most cost-effective way to solve the problems we might be presented with by this project. This might mean a lot of improvisation.
How do you know the mirror system will work adequately?

We did the following calculations to find a general (almost certainly low-range) estimate of the amount of energy created and the amount of water boiled by that amount of energy.

Are you going to know if the water produced is actually pure? You can't just have someone taste it, right?

We intend to purchase a water purity testing kit from Amazon.com to test the water at the end. This kit will give us reliable readings on the pH levels, any metallic impurities in the water, and bacterial problems with the water as well. If the test comes back positive for impurities, we will add some improvements like better filters for instance.

Calculating amount of output for our proposed system:
milliJoules created by our system = solar constant*Adish*Time(seconds)
solar constant = 1.361 kW/m^2 = 136 mW/cm^2
Adish = pi*r^2, (we did this to simplify calculations as the surface area of a concave dish is tough to calculate and estimating it as a circle rather than a dish gives us less surface area, meaning our estimate is on the lower range)
Time will be 3600 s, an hour
We decided on a dish with radius, r = 16.51 cm

mJ = 136*16.51^2*pi*3600 = 422180 J

Finding amount of water boiled with this amount of energy:
Q = 422180 J
422180 = m(4.18)*(60)
m = 1683 g/hr = 1.683 L/hr

How much does this project look like it is going to cost?
For now, we have put the cost of this project at $30 per group member( $150 in total). Due to improvisation though, this cost could go up slightly over the course of the following weeks.

How long do you hope this project will take?
We hope to have built and tested our project by week 9. We will then use the extra week to prepare for our presentation.

Where can I get more information on these kinds of projects?
Well, you can watch this video which gave us the idea of using parabolic mirrors, instead of solar panels here. Ignore the title, he doesn't technically have the power of 5000 suns.
Also, look at this article on CSP technology( Concentrating Solar Power) here

Project Overview

This freshman design project intends to create a solar powered water filtration system using the technique of distillation followed by a small filter, probably a sieve, to ensure clean water. We intend to design this apparatus in an abstract manner but also build a small scale model using a parabolic mirror to concentrate sunlight towards a conductive metal pot that boils the water and a tube, made of heating duct, that leads the water vapor into a smaller container with another filter. If we are successful, this system should be feasible using only solar energy and produce water that is more pure than the original.

The target use for this apparatus is mainly in impoverished nations near the equator, particularly in Africa, where there is an abundance of sun light and a lack of clean water. The system we create should be of use on a person to person basis at the very least if we are successful.

The final product of this project was unsuccessful in boiling water, but did manage to heat the water a reasonable amount and produce bubbling on the surface of the water. Though we were unsuccessful to create a system that boils and purifies water, the prototype was compact, portable, and easy to setup, we intended, and with minor improvements could have been a working system.