Group Project: Passive Solar Air Heaters
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Final Report PH213 2008
Group Project: Passive Solar Air Heaters (a compilation) Table of Contents
Prototyping Reports
Group I 3 Ben Hogstad, Ken White, Group II 7 Brianna Toler, Brent Packebush, Kera Tucker, Dan Stout
Modeling Reports
Group I 13 Brandon Luzier, Brad Barrett, Zak Modrell Group II 21 Luke Foster, Jacob Owen, Matt Steigleder, Jeff Garrison
Testing Reports
Group I 28 Tiffany Stevens, Katrina Gamble, Sara Schroeder, Cassie McCraw Group II 36 A.J. Nelson, Brett Harris, Michael Allen, Paul Aloro
Appendices
Appendix A 53 Raw Data
2 Prototyping Report: Group I
We are going to build a prototype hot air panel heater to be used on a small scale for subsidizing heating costs for broke college students A basic design for a hot air panel is a window with a metal sheet a few centimeters directly behind. The principle idea is that the sun will shine on the metal, greatly heating it up, whereas the glass will keep the heat within the box. As the air temperature increases, it rises. At the top of the box is an outtake valve, which leads to the designated area. The hope is that the air expelled from the system will heat the designated area using the environmentally friendly solar energy.
The basic design of this project is a thermally conductive piece of metal put inside of a box with one side of the box being a window that allows the sun to heat the metal in the box. The metal then heats up the air in the box and air is circulated throw the box heating up the air that leaves the box. We decided to us aluminum because it has a high thermal conductivity, which will transfer heat from the metal to the air fast. Although alternatives have higher thermal conductivity, the prices and availability for those alternatives were far out of reach for the scope of this project. Aluminum is cheap, easy to get, and is far more effective then steel or other reasonable alternatives.
Figure 1
For the window, we had a few choices: sliding, double paned, single paned, and a two-way mirror. The sliding window would block a portion of the light, which is supposed to penetrate it. The two-way mirror is ideal but far too expensive and difficult
3 to find. The double paned window will have a layer of noble gas between each pane. This will act as an insulator. Because of cost issues, availability, and efficiency, the single paned window was chosen. A second layer of air was added behind the sheet of metal to collect the heat lost from the backside of the aluminum. A foam backing was chosen because of its insulation properties. This reduced the amount of heat lost through the rear side. We wanted to be able to absorb both sides of the metal, but we did not think that the dispersal of heat would be equal on both sides. In addition, we wanted to absorb heat from the entire area of the metal. In order to meet this goal, we designed channels forced the air the travel up and down along the backside and side to side along the front. This aspect increased the area of metal, which the air touched, which in turn increased the heat absorbed. Our initial design only had a few channels on both sides and is shown in figure 1. We decided to change the direction of the channels on both sides. On the back the channels would go up and down, and the front, side to side. The backside initially had a possibility of air escaping through the intake valve. By changing the front channels, we changed the path of the air. This allowed the air to pass over different portions of the aluminum sheet, increasing both area and heat absorbed (figure 2).
Figure 2
During the design and building process, we found many flaws with the design. With the design, the air did not reach the entire metal surface. To solve this we added channels to force the air to touch the majority of the metal. One issue that came up while building the model was trying to get the metal channels to seat properly against both the window on the front side of the box and the insulation on the backside. Due to minor cutting errors, gratuitous amounts of silicon sealer was used in order to insure a proper seal, and
4 proper distribution of airflow. One minor thing that could be improved on was the materials used for the frame. The medium density fiber (MDF) that was used split during assembly, even though precautions such as pre-drilling were taken.
Solar Panel
60
50 C s e 40 e r g e Direct Temp °C d n i 30 Exit Temp °C e r Room Temp °C u t a p 20 m e T
10
0
Time in Minutes
Figure 3
The data above (figure 3) shows the panel subject to an artificial sun’s heat for 60 minutes. The pink line is the temperature of the air after it has traveled through the panel. The blue line is the temperature of the air directly in front of the panel (directly absorbing the “sunlight”). The yellow line is the temperature of the air coming into the panel. As you can see the air in front of the panel was much faster to heat up, whereas the air exiting the panel took 45 minutes to catch the temperature of the room. Because the metal panel was relatively thick, the amount of time for it absorb heat will take longer then a soda can. Given the slope of the temperature exiting the panel, the temperature would increase for a period of time after the test finished. With only a few hours of sunlight a day, this time it took for the system to warm up is too long. To fix this a thinner sheet of metal would be preferred, this would allow the system to heat up faster, but cool down faster as well. Heat is generally wanted early in the morning, and not so much later at night, so the thinner metal would be preferred. However, too thin a sheet would cause the system to lose its heat generated if a cloud passed over the sun, therefore
5 a moderately thin sheet seems like the best choice. One which will retain heat for a short amount of time, but will not take 45 minutes to see a worthy output.
6 Prototyping Report: Group II
How We Did It: A Complete Explanation to Our Solar Hot Air Collector Project Brianna Toler, Brent Packebush, Kera Tucker, Dan Stout Every physics conundrum starts with a question, and ours was no different. We were faced with the challenge of building a flat-panel solar hot-air collector. So we did what any other physicist would do first: we went to Wikipedia.org and youtube.com and had many conversations about what to do. From some basic research and a growing knowledge of what these solar- contraptions look like, our group chose an idea and ran with it. The rest of this paper will guide you through how we went from an idea to a finished product. What We Did: There are a plethora of flat-panel solar hot air collectors out there, all of which generally consist of a flat, frame-like-box with metal inside (for heat conduction via the sun) and a piece of glass covering the box to keep heat in. Our group chose what seemed to be the most cost-efficient and effective design. Ultimately, we chose to do a hot air siphon that utilized pop cans as not only the tubes for the siphon, but also as heat conductors. Once we had the basic idea of the design, the materials required, and the basic construction of the hot-air collector, our group was able to start building.
This is a picture of an un-finished pop-can hot air siphon that our group chose to build (this is not a picture of our contraption). As you can see, there is a wooden frame, with a plywood backing and long towers of cans that act as the siphons. Our design was not as long as this one, due to limited resources.
After we knew the design that we were going to use, we had to implement a schedule to make sure things actually got done. Below is a “Gantt chart” depicting a timeline for the work that we planned on doing:
7 How We Did It: The first assignment for our group was for each member to collect materials. Each group member was required to buy or find some of the following: Aluminum soda cans
Wood (preferably two-by-fours) for the frame
A pane of glass (perhaps from a window)
Flat-black spray paint
Foam insulation
Aluminum glue (known as JB Weld)
Contractors adhesive
A calking gun
A small sheet of plywood for the back of the frame
After all of these materials were collected, construction could be started. Below is a step-by-step process expressing the stages of our construction: 1. First of all, you need to know how big your frame is going to be. Once you know the size of the frame, you can measure out how many cans you can fit in it (make sure there is room at the top and bottom for a hole for air to move in and out). Our frame was 26¾ by 33¾ inches. Build the frame first (out of two-by-fours)!
2. Once the frame is built, you can start tinkering with the pop cans for the hot-air siphons. Based on the size of the frame, we were able to calculate an amount of cans needed. Ultimately, we used 45 cans
8 that would make nine rows of 5-can-high columns. The tricky thing is figuring out how to cut uniform holes in the top and bottom of each can. Our group ended up cutting the top and bottom out of 45 cans by using a hole saw.
3. The next step is to assemble the pop cans into tube-like columns. Make sure all of the cans are clean (inside and out) by washing out any soda-residue with water (and soap if need be). Make sure they are all completely dry before gluing them together! Also, it may be a good idea to take sand paper and roughen the part of the can that will be glued to make sure the glue will stick to the aluminum. Finally, start gluing the cans together by using JB Weld. Make sure the glue goes all the way around the rim of the can to make sure it’s as air-tight as possible. Once you have glued all of your cans together, let the columns sit for 24 hours for the glue to set.
4. After the can-columns are fully adhered and stable (not wobbly), paint them black. Painting the columns black will help with heat conduction. Make sure you use a flat-black spray paint and try not to coat too heavily. Our group left an unpainted strip so that it would adhere better to the box.
5. By now, you have a frame, and your aluminum can- columns. Now all you need to do is to put all of the parts together. Start by placing the insulation onto the plywood (that is already cut to size to fit perfectly with the frame) and screw the plywood backing to the frame.
6. Now, use a hole saw to cut a hole in the top and bottom of the backing so that air can come in and out. Make sure that the holes are not overlapping with the cans (so leave enough room for your columns to fit in the box without interfering with air flow).
7. Now, adhere the columns to the box. Use construction adhesive and a caulking gun to apply the adhesive to the columns of the cans, and then press each column firmly to the back of the box. Hopefully your columns fit snugly and happily into their new home.
9 If there is extra room on the sides, make a strip or two of insulation and stuff it in between the cans and the perimeter of the box. Let the adhesive set for a few hours.
8. Next, take some extra insulation and cut it so that it is the right size to fit in between the cans and the glass. Make two of these cut-outs so that it blocks air from the bottom and top of the box from mixing and skewing the overall temperature.
9. Finally, glue and clamp down the glass to the top of the box. Make sure that you use construction adhesive and caulk a thick strip around the perimeter of the frame. Make sure that it is as air tight as possible! Let the glue set for about a day to make sure your glass doesn’t slide off. That would not be good.
10.You are done! To get the heat going from the box to your house, get some heating duct and put it on the back of your box (on the top hole, not the bottom one) and then place the other end of the tube in your house. Enjoy!
Looking Back: There is a stark difference between what our group thought was going to happen and how everything actually unfolded. There were certain aspects of our prototype that took much longer and demanded more thought than originally perceived. Below is an explanation involving the aspects of the project that took much more time than initially expected: The columns of cans. It turns out that adhering an aluminum can to another aluminum can is not as easy as we would have liked it to be. Aluminum is slippery and smooth, and not many glues available can even stick to it, let alone glue two aluminum surfaces to each other. Finally, we found JB Weld, which worked quite well. However, another issue we came across was how to cut the holes in the cans. Each group member had different ideas of how to do it, and using a hole saw seemed un-safe and potentially ineffective. On the other hand, there really are not many other options to go with, which is why we ultimately ended up using a hole saw anyway.
The sheet of glass. Our group debated whether or not we should even use glass. Some group members suggested synthetic materials, like plexiglass or plastic. However, every material we looked at seemed too expensive. There was also the issue of how effective it would be in conducting heat, or reflecting rays of sun. Our group ended up using what was available, and fit perfectly with our frame.
10 Should we use a fan? This was quite the debate within our group. One argument was that using a fan would more effectively move air in and out of our box, while another argument was that it would move too much cold air in, making it harder for air to heat up. Also, a solar-hot-air siphon seems to have a lot more mechanical integrity if it doesn’t even need a fan. So, our group tried using the hot air siphon with and without a fan, and it seemed to work better in absence of a fan. Ultimately, a fan did move too much cold air into the box, making it nearly impossible for any air to heat up.
What would we have done differently? In the end, our group was very content with our unique idea for a solar-hot air siphon. The only “regrets” we may have involve not acquiring materials on time (such as cans). Perhaps building and finishing everything a little earlier would have been more time-efficient and given the other groups more time to test our end product. We started out this project within our scheduled time as it is shown on the Gantt chart shown on page 2. As time went on we began to deviate from the schedule slightly. This was mostly due to the fact that there should have been more time allotted to building the prototype. We were not anticipating some of the delays in finishing the project such as the time for the JB Weld to dry on the cans. To make a professional version of our prototype we would expect it to take about ten weeks. This is only accounting for the building portion of the project.
What next? The ultimate goal of our solar-hot-air collector was to use it in an actual home, which is the one thing that did not happen. Moreover, if our group could continue this project, the next step we would do is to install our design into a house. We would need to utilize some kind of flexible ducting in order to get the hot air from the contraption to the home itself, which could be easily installed. In addition, another un-touched aspect of our project was to take the feedback from the testing group and re-structure our design accordingly. Perhaps there was not enough heat being produced, so we would have to adjust the height and length of the frame and pop-can-tubes. In the end, there didn’t seem to be enough time to build, test, and re-build and re-test our design, which would be a wise thing to do for other groups in the future. This may be difficult, however, since you would have to completely rebuild everything, from scratch, to adjust your design. On the other hand, if the hot-air-collector is to be utilized by a large audience, more testing and re-designing would have to be done. This also means future groups would have to take this into consideration when planning out their timeline and Gantt chart. For future groups, it may be a good idea (if the groups are large enough) to build two prototypes at once. This way the group won’t have to wait for feedback to adjust their design, they just have another one ready to go. This may sound like a counter-productive idea, but if the group knows what they want to do right off the bat and can foresee any issues that may arrive, they can re-design their design and build accordingly. This is definitely optional though.
11 In the end, our group was very content with our design. It was innovative, unique, very effective, and just plain cool-looking. We encourage the general public to consider this design for their home if lowering the cost of heat sounds appealing. Our design for a flat-panel-hot-air siphon has parts that are easily accessible, and that are easy to assemble and implement into almost any home.
Cost Summary
This section was originally intended to document the cost per watt of our modestly sized solar hot air collector. Unfortunately, upon testing the unit my suspicion was confirmed that unit was not adequately sized to produce easily measurable air velocity via convection. It was evident that there was a decent volume of hot air being exhausted, but it was still less than measurable by any simple means. If I were to suggest a solution to this problem it would be to build a larger unit rather than purchase expensive instruments. Of course a larger collector would introduce other challenges for the prototyping and testing groups. Even though our prototype did not produce measurable exhaust air velocities, it did produce a delta t of about 20° C which is substantial. It is my belief that a collector twice the size with the same design could produce measurable air velocities and would be a worthwhile project suitable for a small room, workshop, studio or doghouse.
Solar Hot Air Collector Estimated Cost Material Size/Quantity Cost OSB Chip Board 1 3/8” x 4’ x 8’ Sheet $8.00 Fir 2 X 4 Lumber 1 10’ Length $2.00 Screws/Fasteners Misc. Estimated $5.00 Sheet Insulation 1 1/2” 4’ x 8’ Sheet $14.00 Glass 2’ x 2’Sheet Estimated $20.00 Construction Adhesive 1 Tube $3.00 JB Weld 2 Packages $9.14 Flat Black Paint 2 Cans $4.00 Aluminum Cans 45 12 Ounce $0.00 Total $65.14 Note: This table represents the estimated material costs if one were to buy all of the materials.
Solar Hot Air Collector Actual Cost Material Size/Quantity Cost OSB Chip Board 1 3/8” x 4’ x 8’ Sheet $0.00 Fir 2 X 4 Lumber 1 10’ Length $0.00 Screws/Fasteners Misc. $0.00 Sheet Insulation 1 1/2” 4’ x 8’ Sheet $0.00 Glass 2’ x 2’Sheet $0.00 Construction Adhesive 1 Tube $0.00 JB Weld 2 Packages $9.14
12 Flat Black Paint 2 Cans $4.00 Aluminum Cans 45 12 Ounce $0.00 Total $13.14 Note: This table represents what our group actually spent on our material given that most of the materials were donated at no cost to us.
Modeling Report: Group I
The Task
As a modeling group, our task was to create mathematical expressions that would predict the behavior of the prototype group’s solar hot air collector. We had to find or figure out the relevant equations, constants and variables needed to predict the key performance parameters of the panel. Specifically, we needed to determine the amount of energy going into the panel through the glass front and the amount of energy that leaked out of the collector box by the various mechanism of heat transfer. The difference between these quantities would be the net energy available to extract from the collector.
Additionally, we had to communicate with the prototype team to align our model with their design. Since their design would evolve throughout the term, we had to make our initial model flexible enough to make any changes necessitated by changes to the panel design. The dimensions of the collector, the materials used to form the sides and the back of the box, and the type, quantity and thickness of insulation used were all unknown when we started out.
The prototype team also needed some information from us. It was of interest to them how hot the collector plate would get, for determining what materials could come in
13 contact with the plate, and how much insulation was needed to make the collector viable in an outdoor environment.
We were also to collaborate with the other modeling team via our manager to share information and ideas. Each team was modeling different collectors, but the fundamental issues were the same for both groups. By regularly comparing our work each group could get a better feel about being on track share information about common constant values like the thermal conductivity of glass.
The Solution
We very quickly discovered that the task was large. In order to avoid getting overwhelmed and to just get started, we initially made some assumptions about the panel dimensions and materials and focused on conductive heat transfer. By ignoring heat-loss from the panel due to convection and radiation, and assuming a constant 1000W/m^2 of energy input, we were able to develop a basic calculation of the heat retained in the panel.
This fundamental work got us started in the “Equation Set-up” phase of the project shown in the Gantt chart below.
10/30 11/4 11/9 11/14 11/19 11/24 11/29 12/4
Equation Set-up Heat from sun Equation Heat loss Equation Heat Storage Calculating volume of air Transmission - Sun rays to Metal Transmission - Metal Heat to Air Thermo conductivity - Wood Thermo conductivity - glass Maple Model proto 1 Finished Maple Model
14 The Gantt chart shows the categories that we divided the project into as well as the proposed time-period in which each was to be performed. The idea here was to divide the project into steps, some to be performed in parallel as each member of our team took a different task, and some steps had to wait for results of other steps. The Gantt chart summarizes the scope of the project as we imagined it at the beginning and the time-line in which we hoped to accomplish it.
Details of the model:
Section 1: This section shows a function of the energy into the box as a function of time throughout the day. This function will allow us to find different totals of energy through integration. The Time (t) value is in hours, where (t) is military time (starting at midnight). Our model is for daylight savings time, so depending on the time of the year you will have to change your (t) accordingly. We put the energy function, total energy through the daylight hours and the area of the box in a section at the top of our maple program so we could use it throughout the program.
Area of the box (top or bottom) > Energy through the day > Total energy in one day >
Section 2: This section of our maple program models the bottom portion of the box.
This section of the model starts with the dimensions of the box and materials so, they can be changed and effect the total usable energy calculation at the end of the section. This section also gives us the ability to change the k values of our materials; this will still
15 change the total energy calculation. We also included a place to put the difference in temperature between the inside of the box and the outside of the box. This will change based on what the temperature is in the testing environment. With the previously discussed variables, we can now calculate the thermal conductivity through the different materials and see how much energy is lost through the different materials. The energy in and out of the box allows us to find the total amount of energy that will leave the box through the exit into the next section. The energy that goes into the bottom box is not zero. There is heat radiating through the aluminum. With a model of the heat going into the bottom box, this section of the model will give us the amount of energy that will enter the top box.
Bottom Box Dimensions of box Area of the sides (bottom box) > Thickness of materials (bottom box) > > K Value of materials (bottom box) Range of K for sides (.14-.05) > > Temperature inside and outside (bottom box) > > Thermal conductivity through materials (bottom box) > > Energy out and in (bottom box) > > Net energy (bottom box) >
Section 3: Section 3 is the same layout as section 2 with different materials. The only differences are the temperature in the box and the energy entering the top box. The temperature in the box in both section 2 and 3 should be an equilibrium temperature or a
16 function that shows the temperature increasing to equilibrium. The energy entering the top box, will be described by the function in section one. Now the final difference in energy at the top box is the total energy that will come out of the box. A few different aspects that we did not get to explore will change our model and make it more realistic will be discussed later.
Top Box Dimensions of box Area of the bottom (top box) > Area of the sides (top box) > Thickness of materials (top box) > > K Value of materials (top box) > > Temperature inside and outside (top box) > > Thermal conductivity through materials (top box) > > Energy out and in (top box) > > Net energy (top box) >
The Reflection
In implementing the original solution, we found that it was a lot harder to find reputable data and consistent forms of equations to use in our project. An example would be of finding thermal resistivity values (R, U, and k values). We had an extremely difficult time finding them at all, and when we did find them, there were huge variances between sites. We started out finding R values but discovered that these are not as
17 reliable as U values. In addition, we could not use the U values (which are American values) because they are in SAE units, so we had to go with European U values (which, consequently, are equal to 1/R, or the inverse of R).
During the process of developing a model, we had to modify our equations constantly to keep our results reasonable. We made a basic model that just took into account the area of the box and the heat of the metal on the inside. The box we were modeling had two chambers in the box (front and back of the metal) and had medians to direct the air over both sides of the metal to take advantage of the full the heat put off by it. Our model didn’t take this into account so we tried to come up with a way to alter it but didn’t end up getting there. We had the idea of treating the box as one length with changing temperature with half of it taking into account the sun and half without, but we ran out of time.
In order to be more successful next time, we could have taken Bruce’s advice and looked around on Maple forums and seen what else there was out there on this topic and borrowed a basic model to work with. This way we could’ve focused more of our time on the difficult parts such as the problem in the paragraph above that we didn’t have enough time to complete. Another thing we would have greatly benefited from would have been to receive data from the testing group so we could have used this data to compare what we were finding in our calculations with something.
We had trouble figuring out how to model the radiation heat transfer through the glass since light can pass through, but it traps heat. We also had trouble integrating the
Stephan-Boltzmann constant.
18 We got about half of the Gantt chart done but at different times than what it had.
We didn’t see the Gantt chart when we started working on our model so it doesn’t reflect the processes we went through in our model.
I would estimate it would take around a month to complete the project. This is because from what we have observed about design teams, they are working on multiple projects and the same time.
Where we were going with the model:
We had several goals that we never have to explore because we ran out of time, so we will tell you where we were going with this model. We left off with finding a reasonable model for energy into the box throughout the day. The model takes into consideration the angle of sun and the intensity at different times. Below is a list of several issues that we did not get to with our model.
1. We were going to find a way to represent the aluminum plate worming the air in
the bottom box; this would be the energy into the bottom box. You can see our
model will find the energy into the top box. We also wanted to find how the
aluminum plate affected the temperature of the top box. The temperature of the
aluminum plate will change how much heat can transfer into the bottom box,
which brought us to the next problem.
2. We discovered that we would need an equilibrium temperature that the plate
would reach and the air in the bottom box would reach. These all depend on;
mass, volume, density, time, and intensity of energy. With this information, we
wanted to come up with a model of inside temperature of the bottom and top box
as time (t) goes on.
19 3. Knowing total energy into the top box from the bottom box will allow us to find
equilibrium temperatures in the top box. If we know how hot the top and bottom
box can get when it is “closed”, we then wanted to find how fast the air should be
circulated through the solar heater.
4. We wanted to be able to come up with some plots that would represent different
aspects of the heater. We wanted to show how decreasing the outside temperature
would affect the total energy out, and the speed of the fan to maintain a certain
temperature. We also wanted to show how the area of the box would change the
energy out of the box and the fan speed.
5. The biggest factor that we found when working on this project was temperature.
We found that almost everything depended on the temperature difference from
outside to inside.
Everything Else
Group Members: Brandon Luzier, Bradley Barrett, Zak Modrell
"Radiation Laws." Astronomy 162 Stars, Galaxies, and. University of Tennessee . 10 Dec 2008
20 Modeling Report: Group II
Our Physics class decided to use the remainder of our trimester to attempt at creating a hot air collector. In order to achieve this we first decided to brainstorm all the necessary parts that were needed to complete this task. After much deliberation we decided that there should be three different groups that the tasks will be distributed amongst in order to be more efficient in our efforts.. In this project we were not only trying to create a product, but were trying to go through the entire process of what we could expect to see in a career situation.
This last portion of the course was designed to expose us to what we could expect if we were handed a RFP. In order to achieve as much as we could we decided that we would need 3 major groups. The three major groups that we decided to split up were the modeling, prototype, and testing groups.
Our task as the modeling group was to create a mathematical representation of how we would expect the hot air panel to operate. In order to achieve our task of creating our model we used a very beloved and familiar software program called Maple. What our task contributes to the group is a representation constructed of various functions that would predict the behavior of the hot air panel. The significance of this is that we could use our model to adapt and change certain specifications to optimize efficiency. Our program could model any changes in the design and we could hypothesize the outcome. In order to create our model we began discussing our knowledge of thermodynamics and lack there of. After realizing we only had half the knowledge
21 needed to complete this model we quickly began researching the missing elements needed to construct this model.
Our initial approach to this was to first conceptualize the physics involved.
We decided that at the most basic level we needed to find equations for the energy coming into the box, the energy lost from the physical characteristics of the box, and the energy stored which would then be transferred into the room.
These equations would account for the overall energy movement within the system. We knew once we had the equations of the energy flow through the system we could input those equations into maple and come up with a visual representation of the data. We first decided to find the equations of energy transfer in general terms using variables so that when the prototype group came to us with specific dimensions we could simply put in the scalars and produce a visual. We decided to construct a Gantt chart that would help keep us on track of the tasks at hand. After much research we found that the equations were far more complex then we had initially anticipated. The energy that came into the box was just a scalar multiple constant of energy at the surface of the earth multiplied by the surface area exposed of our conducting metal. The energy lost equations were where it started to get intricate. In order to calculate the energy lost we had to find energy transferred through the different mediums chosen, and the energy transferred if we insulated those mediums. Another part of the energy lost equation was the energy lost through the glass by the radiation from the energy source. After we found the energy lost we could solve for the energy that was retained, which could then be extracted. We will go further into these concepts in the following paragraph. After we had conceptually worked out some
22 of the necessary equations we began collaborating with other groups and sources to try and form general equations.
We used the following Gantt Chart to keep an adequate pace. This was our projected timeline, however we were not able to get as far as we would have liked to. Some of the necessary pieces of the equations were too complicated to achieve in our allotted time.
Here are explanations of the Maple process. > SA(Conductor):=((3.145*d)/2)*h1*45;
SA is constant created in Maple to show the surface area of the can affected by the energy of the sun. > Energysun :=1000*J/(m^2*s);
This is the energy of the sun on the surface of the earth as a constant called Energysun > EnergyIn:=SA(Conductor)*Energysun;
“EnergyIn” is the product of the surface area multiplied by the Energy of the sun.
23 > kwood:= .13;
> KSides:= (1/(1/kwood))*(Aside*T); # Thermal conductivity of sides
> kply:= .13: #u value for plywood > kglass:= 5: #u value for glass > kinsul:= .085: #u value for insulation These European “k” values are easy to convert to U values, which are thermo conductivity coefficients that describe heat transfer through different mediums. > ktotal:= kply+kinsul;
In order to calculate the “k” value for the back of the flat panel box, add the “k” value for plywood and insulation, which is the medium of the back of the box. > KBack:= (1/(1/ktotal))*(Atop*T);
This is the change in heat using the “k” values over time of heat traveling through the back of the box. > KGlass:=(1/(1/kglass))*(Atop*T);
This is the change in heat using the “k” values over time of heat traveling through the top of the box through the glass. > EnergyOut:=(KSides+KBack+KGlass);
This is the total amount of heat lost through all different mediums of the box. > EnergyNet:=EnergyIn-EnergyOut;
This is the amount of energy that is retained in the box and could potentially be extracted for use in heating a structure.
Our solution included four different aspects, the energy in, energy lost, energy retained, and finally the energy harvested. Energy lost was where we ran into multiple roadblocks that interfered with our ability to find both the energy retained and the energy harvested. Firstly K values where hard to find having to hunt through the internet and sometimes finding conflicting values. A K value is thermal conductivity through a medium. The K values that we found only
24 considered heat transfer through a substance but not radiation through that substance. From there we had to find thermal conductivity radiation constants.
These values, known as U values were found using European information sources. Another problem that we were never able to resolve completely was the heat transfer through a window. We know that light passes efficiently trough glass but we were never able to find a reliable source that told us how radiation is reflected through a window. Our Gantt chart was very reasonably accurate from implementation to finalization. Our two corrections where adding on an additional week to the overall timeline and taking out the finalization of the equations. The model equation for hot air flow through the box was too complicated for the time allowed so we did not even include its completion in out
Gantt chart. On a professional level, we think it would take about a month to completely finish every aspect of this project. A professional would probably have several projects to work on at the same time so they wouldn’t be able to focus on this one project 100%. Also there are several different equations that would take some time to develop accurately.
In order to fully model a solar hot air collector we needed to concentrate on four different areas. Heat collected by the box, heat lost trough the box, heat retained by the box, and heat harvestable out of the box. Our group mostly concentrated only on how heat would be lost trough the box and partially on how the heat is collected by the box. We used the model that the prototyping team was building to outline the constants and equations we needed to model the system. This limited us to a simple small box with no insulation and a single glass sheet as a window. To advance our goals we needed to work on more areas of the heat
25 equations and create a model that was able to include a wider selection of materials. The equations that we were able to finish where mostly heat loss through materials. To get the whole picture we needed to more accurately model how radiation is reflected by glass. We were only able to find what looked like the window acted like an open door. The next problem would be figuring out how as the metal heated up how it would affect the air inside the box. Would the air heat up as the metal heated up or would the metal have to reach a certain temperature before it started to heat up the air. Other than the problem with finding this equation is finding how different metals would react. How the metal in the box heats up depends on how long it is contact with sunlight. We did find that this would require an integration problem. All of the details of this problem are unsolved but with more time we would have been able to find these. Most of the problem with this was determining if we had to integrate from 0 to 12 hours, or from 0 to 90 degrees. With an equation that shows how much energy is entering the box, an equation for how the energy left the box, and an equation for how the metal heats up the air in the box then your next problem would be to work out harvestable energy. This would include how much hot air you could move out and how fast you could move the air without effecting how hot the air was. There should be some middle ground where you can pull air out of the box at the same rate that it heats up. Once all the equations are worked out then the next step would be to build a model that included all possibilities for building materials. Different metals, different thickness of metal, different types of insulation and different types of windows are just a few possible parameters that
26 could be explored. The difficulty with this would be to find the U values for all the different materials and changing the equations for multi layered materials.
Group members:
Luke Foster, Jacob Owen, Matt Steigleder, Jeff Garrison
Sources: http://www.chomerics.com/products/documents/thermcat/heat_transfer_fund.pdf http://www.engineeringtoolbox.com/overall-heat-transfer-coefficients-d_284.html http://almashriq.hiof.no/lebanon/600/610/614/solar-water/unesco/21-23.html
27 Testing Report: Group I
Tiffany Stevens Katrina Gamble Sara Schroeder Cassie McCraw Final Assessment of Solar Energy Project 1. Core Tasks:
The core task was to develop a plan for actually testing the energy output from the carefully designed solar panels. We wanted to determine this based on the amount of heat coming at the plate, how much heat is getting trapped within the plate, and how much it is releasing. If time allowed, this information could be used to determine whether the use of such a product on a home could supplement the cost of heating during the winter months.
o The overall outcome we were trying reach was the cost/mJ of energy produced by use of a solar panel.
Our original task list included: o Making sure the equipment was working properly o Finding the intensity of the light coming from the sun to determine where we would need to place the panel in front of the heat lamp to get the same intensity o Quickly retesting the equipment and then testing the prototype both indoors and outdoors o Revising our testing procedure to make sure we are able to reach our intended outcome o Analyzing the data collected from our first series of tests o Retesting the prototype with our revised testing procedure o And finally making a final analysis of the data we collected 2. Initial Form of the Solution
The initial solution we ultimately set out to produce was whether solar panels were an efficient energy heat source during the winter months. To accomplish this we figured that we would need to find
The intensity of the sunlight/artificial sunlight
The rate of the air flow out of the panel
28 The heat that hits the panel vs. the heat that gets trapped within the panel vs. the heat that is released
The temperature of the absorbing plate
Determine at which angle the panel absorbs the most heat energy (30, 60, 90, 45 degrees)
There were many variables that we thought would be important in determining the successfulness of each solar panel but found that we did not have the time or the resources to collect all the necessary data. The original timeline of the Gantt chart become irrelevant when the necessary cooperation with the other groups fell apart and the weather did not cooperate (e.g. we could not test the panels before the prototyping group completed their prototypes, and could not test the true effectiveness of the panels outside on a cloudy day).
3. Solution Details
In the end the only thing that time allowed us to test was the efficiency of the panels when placed in front of the artificial sunlight (the heaters). We were not able to test outside because go figure....10 days of sunshine followed by 1 day of clouds which happened to be the lab period in which we had hoped to test. From the data we were able to collect by placing the solar panels in front of the artificial sunlight we found that both heaters worked as they were intended to, but the passive system made using aluminum cans heated more quickly. The test we actually performed required the use of a heater (“artificial sunlight”) and a labquest with 3 temperature probes for each of the 2 solar panels. The temperature probes were used to monitor the temperature of the room, the temperature of the heater, and the temperature of the air inside the solar panel.
29 (These temperatures are shown on our graphs; blue=room temp., purple=heater temp. orange= panel temp.) For the data we collected we can gather that both of the blue lines are at about the same temperature and stay constant, which is a good thing since they were measuring the temperature of the room. When comparing the purple lines we can see that the heater placed in front of the non-passive system (the one with the steel plate) took longer to heat up, and gave off a lot more heat. And the orange lines (the one’s we really care about) show that air inside the passive system (made with aluminum cans) rose in temperature at a constant rate and was beginning to flatten out at 53°C, and the temperature of the other system (made with the steel panel) followed suit and had very similar results, although it heated up at a faster rate. An explanation for the variation in the data the graphs showed can be rationalized by the use of different materials to construct each panel and the difference in the heaters. Aluminum cans are much thinner and less dense, than steel plate which would explain why they heated up faster. Also the heaters varied in the amount of heat they gave off. The newer one gives off much more heat and less light, while the other one is more equal in its transmission of heat and light.
**** The labquest graphs are attached separately and are labeled 1 and 2. Graph 1 corresponds to the aluminum can panel and Graph 2 corresponds to the steel plate.
4. Reflection
This project opened up a whole new prospective for us. None of us were truly jazzed about the idea when we started because we had no idea where to go or even begin. As time went by, this project really grew on us and we became more and more excited about it. We were all fired up and ready jump into testing to get results and find out whether this whole homemade solar panel thing really worked, but didn't have anything to test. Unfortunately, the prototyping groups took longer than we had anticipated which didn’t give us much time to test. We were not able to perform all the test we had hoped because by the time the prototypes were ready we were out of time in the term.
When it came down to actually testing we had to throw out variables that were important contributing factors, but that we just simply did not have time to test. In the end we were only able to run one test which showed that the solar panels did in fact work and seemed to be efficient. In the future, now that we have some idea of where to go with this project, we would spend more time testing the things we originally set out to test including the airflow in and out of the panel, the angle (which translates to the time of day) at which the plate is most efficient in absorbing the most energy, and whether the plate is as effective outdoors in true sunlight, as it is in the lab with our artificial sunlight.
30 If we had the opportunity to do this project again, I don’t think we would take a different direction we would just simply spend more time testing and developing more detailed tests that would lead us to our desired outcome.
Throughout this process are biggest problems came from unpredictable weather that made it difficult to effectively test our prototype and calibrate our photo detector to the correct intensity.
The original schedule was not accurately reflected on our Gantt chart because testing was reliant upon the completion of the solar panels for which we were at the mercy of the prototyping groups.
Now that the solar panels have been constructed we think that about 3-5 weeks should be enough time to thoroughly complete the task we undertook at the professional level. This timeline would be sufficient assuming that not every single factor acting against the solar panel is considered, just the ones that we deemed most important including the intensity of the sun’s rays relative to the outdoor temperature, the angle at which the panel is most effective, the airflow into and out of the panel, and the temperatures on, into, and out of the solar panel.
5. Next Steps
To continue this project we need additional testing time and a sunny day. Further tests that still need to be conducted include
o How the airflow into and out of the panel affect the efficiency
o One idea we had was to put toilet paper over the holes and calculate how far out the paper moved (meaning the angle).
o How the panel works in the sun and whether or not is efficient
o The angle at which the panel is absorbing and putting out the most energy
o Finding a way to efficiently demonstrate the sun with each of the different heaters.
o Find some way to make sure the intensity of the light being reflected on the panels is equal for both heaters and the sun.
31 Potential problems include having a nice day on which to test the panel outside, knowing how and having the proper equipment to measure the angle of the sun, and having some device with which to measure the airflow. 6. All other information Testing Group Awesome! Week 1 Basically what we are trying to get from this whole process is a feel for what is like to go through the motions of actually planning, building and testing the efficiency of a product to solve a problem or prove a point. We are constructing a solar panel to determine whether the use of such a product on your house could supplement the cost to heat your home during the winter. The Outcomes we are trying to reach: The cost/ mJ of energy produced in this way
What we are actually testing for: The intensity of the sunlight (both inside using our
The rate of the air flow out of the panel
The heat that gets trapped within the panel vs. the heat is released
The temperature of the absorbing plate
Determine at which angle the panel absorbs the most heat energy (30, 60, 90, 45 degrees)
How we will actually test: Equipment
1. Heater
2. Lab Quest (with temp probe and photo probe to measure intensity of the light)
3. Meter Stick
4. Calculator, Computer, Timer
Set the panel 1 meter from the energy source (heater in our case) and find the amount of heat that is being absorbed
Task List: Equipment test Sun test Lamp test Test equipment
32 Test Prototype Revise Analyze Test Prototype Revise Analyze
Week 2
Intensity of the Sunlight on the ground: Average: 1000 watts/m² Summer: 1029 watts/m² Winter: 868 watts/m²
Use a photo probe to get the intensity outside and then use the same probe to get the intensity of the heater (artificial sunlight)
13, 000 lux Outside 11:00am on 11/6/08 32,000-130,00 Lux on a given day in direct sunlight 10,000-25,000 lx In full daylight (not direct sunlight) Inside light sensor needs to be set at 6000lux Outside light sensor needs to be set at 150,000lux
Week 3
A note from Bruce: Focus more on what we see and what is happening and worry about the calculations and calibration later. Another note from Bruce: Compare the two prototypes with the heater inside an outside in the sun. Don’t worry so much about all the variables that come into play o Variables that we are not taking into consideration: 1. Outside is visible light which the probe is more sensitive to, inside the heater produces more infrared light which the probe doesn’t detect as well 2. The angle at which the rays are hitting the panel 3. The difference in temperature inside vs. outside Calibrating the lab quest photo sensor: http://www2.vernier.com/booklets/ls-bta.pdf Slope at 6000lux 1692 Slope at 150,000lux 38424 Calibrated to a 100 watt light bulb o The light emitted by the light bulb is spherical in shape . Ft candle=10.76391 Lux
33 . 5250 lux= .0007 watts/cm² . 100 lux= 1 watt/ m²
Prototype 1: Thermosiphon: o Using aluminum cans, spray painted black to retain the heat. Testing: o Airflow in and out of hole at top and bottom o Temperature of air in and out of hole at top and bottom o Temperature of outside air hitting the glass o Intensity of the light that it is hitting the glass o Get a temperature as a function of time . Stick the temp. probes into solar panel and watch temperature rise until it stabilizes (which it should do!) Prototype 2: Cold air and warm air is being cycled through by a fan. o The cold air will be pulled in the bottom, then directed through the panel to optimize the temperature of the air that is being blown into the house. Testing: o Airflow in and out of hole at top and bottom (check to make sure the fan is accurate) o Temperature of air in and out of hole at top and bottom o Temperature of outside air hitting the glass o Intensity of the light that is hitting the glass o Get a temperature as a function of time . Stick the temp. probes into solar panel and watch temperature rise until it stabilizes (which it should do!)
34 Make note of different variables (outside temp., thickness of the glass, light intensity) Data: 1. Intensity of sunlight (outside): 94,000-97,000 lux o Setting: 150,000 lux o With polarized lens: 55,000 lux (about ½ which proves correct calibration) 2. Distance from heater to model sun: 69 cm away which will give us a 1 meter cone of testing area. o Setting: 6,000 lux ***There is not enough light coming out of the heater to accurately model the intensity of the sun o The diameter of the heater is 40cm
35 Testing Report: Group II
In this project, we are trying to get a feel for what is like to go through the motions of actually planning, building and testing the efficiency of a product to solve a problem or prove a point. As a class, we are constructing a solar panel to determine whether the use of such a product on your house could supplement the cost to heat your home during the winter. Week 1 During week 1, we were getting together with our groups and discussing all possible options to test the two different prototypes. The Outcomes we are trying to reach: The cost/ mJ of energy produced in this way
What we are actually testing for: The intensity of the sunlight (both inside using our
The rate of the air flow out of the panel
The heat that gets trapped within the panel vs. the heat is released
The temperature of the absorbing plate
Determine at which angle the panel absorbs the most heat energy (30, 60, 90, 45 degrees)
Equipment with which we will actually test: Equipment
5. Heater
6. Lab Quest (with temp probe and photo probe to measure intensity of the light)
7. Meter Stick
8. Calculator, Computer, Timer
36 Set the panel 1 meter from the energy source (heater in our case) and find the amount of heat that is being absorbed
Overview/Introduction:
As a group, we worked closely with the prototyping groups in their designs and ideas for the solar hot air collector. We discovered that there are many ways of creating a functional collector, as we had both a passive and active model emerge from the two groups. We figured out that the air collectors each worked in virtually the same way. They absorbed heat from a source on the surface of the model. They took in the air from inside the house (or room it was in) and transferred it up through the collector, where it was slowly heated by the surface until it was released back into the room as heat.
We originally had many ideas for this project. We had some ideas that were reaching rather far, and then had to revise these when we realized we only had about a month and a half to complete this experiment. We wanted to test the prototypes in both the natural sun as well as in front of the heater. We also planned on recording the cost of each material and then find materials that would be more cost efficient in the future. We also planned on giving the prototype group feedback early on so that they could make their models more efficient. Unfortunately, with the time given, we were only able to test in front of the heater, and were unable to complete the supply list or enough feedback to be effective.
Gantt Chart: Tasks Start Date Duration (in days) End Date Equipment test 11/6/2008 10 11/16/2008
Sun 11/13/2008 1 11/14/2008
37 Lamp 11/13/2008 1 11/14/2008
Test equipment 11/6/2008 7 11/13/2008
Test Prototypes 11/13/2008 14 11/27/2008
Setup 11/13/2008 1 11/14/2008
Test 11/13/2008 14 11/27/2008
12/1/2008 6 12/7/2008
Analyze Data 11/22/2008 10 12/2/2008
proto 1 11/22/2008 10 12/2/2008
proto 2 11/22/2008 10 12/2/2008
Start Chart 39,749.00
End chart 39,794.00
39,730.00
38 Gantt Chart Test
10/29 11/8 11/18 11/28 12/8 12/18 Equipment test Lamp Test ProtoTypes Test Analyze Data proto 2 Above is a Gantt Chart regarding the previous information and the time it took to complete each task. We actually didn’t get to follow this chart exactly… for instance, we tested each prototype on 12/8 as opposed to our original hope, which was on 11/18 or 11/28.
Week 2
Intensity of the Sunlight on the ground: Average: 1000 watts/m² Summer: 1029 watts/m² Winter: 868 watts/m² We found these numbers on the internet.
Use a photo probe to get the intensity outside and then use the same probe to get the intensity of the heater (artificial sunlight), and this is the data we collected from the LabQuest of natural sunlight.
39 13, 000 lux Outside 11:00am on 11/6/08 32,000-130,00 Lux on a given day in direct sunlight 10,000-25,000 lx In full daylight (not direct sunlight) Inside light sensor needs to be set at 6000lux Outside light sensor needs to be set at 150,000lux
Week 3
A note from Bruce: Focus more on what we see and what is happening and worry about the calculations and calibration later.
Another note from Bruce: Compare the two prototypes with the heater inside and outside in the sun. Don’t worry so much about all the variables that come into play o Variables that we are not taking into consideration: 4. Outside is visible light which the probe is more sensitive to, inside the heater produces more infrared light which the probe doesn’t detect as well 5. The angle at which the rays are hitting the panel 6. The difference in temperature inside vs. outside Calibrating the lab quest photo sensor: http://www2.vernier.com/booklets/ls-bta.pdf Slope at 6000lux is 1692 Slope at 150,000lux is 38424 Calibrated to a 100 watt light bulb o The light emitted by the light bulb is spherical in shape, and below are some conversions we found online, whether or not they are directly relevant to our goal. . Ft candle=10.76391 Lux . 5250 lux= .0007 watts/cm² . 100 lux= 1 watt/ m²
40 Prototype 1:
Rough sketch of potential model for prototype 1
Thermosiphon: o Using aluminum cans, spray painted black to retain the heat, with a dark background to absorb the heat from the sun as well. Testing: o Airflow in and out of hole at top and bottom o Temperature of air in and out of hole at top and bottom o Temperature of outside air hitting the glass o Intensity of the light that it is hitting the glass (note: We didn’t get to this step in our calculations and actual testing). o Get a temperature as a function of time . Stick the temp. probes into solar panel and watch temperature rise until it stabilizes (which, we predict, it should do!)
41 Example picture of Prototype 1: Using the aluminum cans to produce heat… this is the front view of the model. We placed a LabQuest temperature probe on a ring stand in front of the glass in direct way of the heater.
42 Back view of prototype 1: The heater is approximately 69 cm away from the face of the model.
43 Using toilet paper to very roughly determine the amount of air flow from the hole at a given time: We taped one of the temperature probes here to test the air coming out of the model.
The hole through which the colder air was sucked in: We placed a temperature probe here as well.
Prototype 2: Cold air and warm air is being cycled through by a fan. o The cold air will be pulled in the bottom, then directed through the panel to optimize the temperature of the air that is being blown into the house. Testing: o Airflow in and out of hole at top and bottom (check to make sure the fan is accurate… there was not enough air flow to test it using our Airflow device, which we thought we could do at first; hence, the toilet paper test) o Temperature of air in and out of hole at top and bottom
44 o Temperature of outside air hitting the glass o Intensity of the light that is hitting the glass (We didn’t get to this step) o Get a temperature as a function of time . Stick the temp. probes into solar panel and watch temperature rise until it stabilizes (which it should do!)
Rough sketch of prototype 2
Make note of different variables (outside temp., thickness of the glass, light intensity)
45 Photo of prototype 2: Again we placed a temperature probe in direct way of the heater.
46 We used another, smaller piece of the toilet paper to roughly judge the amount of air flow from the model. We placed another temperature probe in the way of the outcoming air again.
This is the fan that was used in prototype 2 in order to suck the colder air in and heat it up before coming out from the hole above. We used another temperature probe in front of the fan.
Information to use: 3. Intensity of sunlight (outside): 94,000-97,000 lux o Setting: 150,000 lux o With polarized lens: 55,000 lux (about ½ which proves correct calibration) 4. We modified our original distance to place the model from the heater after testing the energy from the sun. Distance from heater to model sun: 69 cm away which will give us a 1 meter cone of testing area. We found this by using the LabQuest and testing the temperature of the heat emitted from several angles from the radiator. We thought were were going to use
47 the dimensions shown below, but ended up discarding the angles and only using the distance from the heater:
o Setting on the LabQuest: 6,000 lux
***There is not enough light coming out of the heater to accurately model the intensity of the sun o The diameter of the heater is 40cm
Results:
Unfortunately, on the day that we were to test these two models, it was overcast and foggy, and so we had to test both using a round heat radiator. We placed both heaters approximately 69 cm away from the model (as we had decided above, the distance from the heater that was most replicable of the sun’s energy). We used three temperature probes for each prototype. We placed one on a ring stand directly in front of the model to record the temperature of the heat traveling from the radiator to the surface of the model. We taped the second
48 probe so that the tip was directly in front of the out coming airflow. The third probe was placed at the end where the air was being sucked into the model.
We used the LabQuest to graph the temperatures. We took data for 1 hour, and took the temperature at 30 second intervals. After we tested the two prototypes, the following is the data that was collected: Raw data is listed in Appendix A.
Prototype 1:
Solar Panel no Fan
60
50 s e e r
g 40 e d
In Front °C C
n 30 Air out °C i
e
r Air in °C u t
a 20 p m e
T 10
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 2 4 6 8 0 2 4 6 8 1 3 5 7 9 1 3 5 1 1 1 1 1 2 2 2 2 2 3 3 3 Time in Seconds
Prototype 2:
Solar Panel with Fan
60
50 s e e
r 40 g e d Fan In Front °C C
n
i 30 Fan Air out °C
e
r Fan Air in °C u t a
p 20 m e T
10
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 7 1 2 5 6 1 2 3 4 5 8 9 0 3 4 7 0 2 4 6 8 1 3 5 7 9 1 3 5 2 4 6 8 1 1 1 1 1 2 2 2 2 2 3 3 3 Time in Seconds
49 Both Panels:
Both Panels
60
50 s
e 40 e r Fan In Front °C g e
d Fan Air out °C
C Fan Air in °C n
i 30
e No Fan In Front °C r u t No Fan Air out °C a p No Fan Air in °C m
e 20 T
10
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 2 8 4 8 4 0 6 2 0 8 4 0 6 2 0 6 2 8 4 1 3 5 7 9 0 4 9 3 7 0 4 6 2 6 8 1 5 8 2 1 1 1 1 1 1 2 2 2 2 2 3 3 3 3 Time in seconds
As you can see, Panel one heated up faster and leveled off quicker than Panel 2, but Panel 2 was still heating up at the end of the experiment.
Reflection:
As the testing group, unfortunately our opportunity to test these hot air panels had to come at the very latest time allowed for us to carry out the testing. With
50 time being the greatest issue, we could not test the panels as accurately as we would have liked. This lead to some questions that went unanswered that did not allow us to understand the capabilities of each panel in comparison to the other. Plus, we could not control the experiment as well as we would have liked to so that we could analyze the results and throw out as many factors as possible that might have affected the results. Nevertheless, just like the real world, there is not enough time to go back and re-try the experiment, so what we must do is analyze the results to the best of our abilities. After the analyzing process, trying to find out why the results turned out the way they did is an essential key in trying to improve any device. The results that we gathered from the experiment was clear, both solar heat panels did work. Both panels did warm the cool incoming air by circulating it through the panel and letting it escape into the room. However, what we found was that the two panels warmed the cool air at different rates and circulated the air at different rates. One panel warmed the air rather quickly and it was quite warmer than the incoming air. The other panel took a little longer to warm the air, but how warm of air it would have produced is still a question. Our job as the testing and verification group is to analyze what we got, and try to find answers to why the results are the way they are. By looking at the graphs, it appears that the thermosiphon panel had its outgoing air level off in the one-hour time interval. The other panel, however, took longer to warm up the air, but the temperature of the outgoing air was still rising when the experiment ended. After contemplating this result, we believe this happened for a couple reasons. The panel that used the passive-flow method had air within the panel for a longer time, because the air could not be circulated very fast. This made the panel produce air that was warmer than the heat hitting the panel on the outside for the entire experiment. The panel that had the fan circulating the air moved the air through the panel faster, which made for a slower warming of the air in the beginning of the experiment. This panel also had a thicker aluminum sheet inside of it, which was slower to warm up than the aluminum cans. For most of the experiment, the air warmed by the panel was cooler than the heat hitting the panel. However, once the experiment was
51 nearing the end, we found that the panel with the fan, finally produced air that was warmer than the heat hitting the outside of the panel. To understand this happening, the construction of the panels needs to be studied, and the test must be longer (especially for the fan-powered panel). The thermosiphon panel was made out of thin aluminum pop cans, with the metal being thin; it did not take long for them to warm up. Once the cans were warm, the air was warmed rather well. The panel with the fan however had much thicker aluminum inside helping to warm the air. With the metal in this panel being thicker, it took longer for it warm up. This explains why it took longer for this panel to create an outgoing air that was warmer than the air hitting the panel. One interesting idea is to find out what would have happened once the heat was switched off. We predict the panel with the fan would create an air that was warm because it would take much longer to cool the metal in the panel. To find out more about these two panels would have to require some more testing. For starters, using the same heater for the two panels would be the best way to see how well the panels performed in comparison to each other. Whether the heater is the sun, or the heaters that we used for our experiment, using the same heat source is the best way to go, even though it would be beneficiary to test both panels in the direct sunlight as well as the heater. Doing this would eliminate any possibility of giving one panel an advantage over the other. Letting the experiment run until both outgoing air temperatures leveled off would answer the question of which panel creates the warmest air. Since we could not get a reading on our air movement devices, determining the flow of air would show which panel circulated air the fastest, which would in turn warm the room the quickest. There are many aspects of these panels that can be looked at to not only answer questions of why they work the way they do, but also using those answers to try and improve the panels to make them as efficient as possible. It would also be beneficiary to test both products in front of the natural sun as well as the heater.
52 Appendices:
Appendix A: Temperature Data
Prototype I
Below is the data we collected from the Solar Panel with no fan:
Time In Air out Air Front °C in °C °C 0 29.3 40.7 21 30 29.4 39.5 21.2 60 29.5 38.7 21.5 90 29.6 38.4 21.4 120 29.4 38.4 21.5 150 29.4 38.6 21.5 180 29.6 38.9 21.5 210 29.6 39.3 21.6 240 29.5 39.5 21.6 270 29.8 39.9 21.7 300 29.9 40.2 21.7 330 30 40.7 21.8 360 30.1 40.8 21.8 390 30.1 41.1 22 420 30.2 41.4 22 450 30.4 41.8 22 480 30.5 42.2 22 510 30.4 42.3 22 540 30.5 42.6 22 570 30.5 42.9 21.9 600 30.5 43.1 21.9 630 30.5 43.4 21.9 660 30.4 43.7 21.9 690 30.5 44.2 22.1 720 30.6 44.3 22.1 750 30.6 44.5 22.1 780 30.6 44.8 22.1 810 30.6 44.9 22.1 840 30.7 45.2 22.1 870 30.7 45.2 22
53 900 30.9 45.4 22.1 930 30.9 45.5 22.1 960 30.9 45.8 22.2 990 31 46.1 22.2 1020 31 46.3 22.2 1050 31 46.4 22.2 1080 31.1 46.5 22.2 1110 31 46.7 22.2 1140 30.9 46.8 22.2 1170 30.9 47 22.1 1200 31 47.2 22.1 1230 30.8 47.5 22 1260 30.9 47.5 22.1 1290 31 47.8 22.1 1320 31.1 47.9 22.2 1350 31.6 48.3 22.2 1380 31.8 48.5 22.2 1410 32.1 48.5 22.2 1440 32.3 48.5 22.2 1470 32.5 48.6 22.5 1500 32.7 48.7 22.6 1530 32.9 48.6 22.5 1560 33.1 48.7 22.5 1590 33 48.7 22.4 1620 33.3 48.7 22.3 1650 33.4 48.9 22.3 1680 33.4 49 22.3 1710 33.5 49.2 22.2 1740 33.6 49.4 22.3 1770 33.8 49.6 22.3 1800 33.8 49.9 22.3 1830 33.9 50.1 22.4 1860 33.9 50.2 22.4 1890 33.9 50.3 22.4 1920 33.8 50.5 22.4 1950 33.8 50.6 22.5 1980 33.7 50.6 22.4 2010 33.8 50.7 22.4 2040 33.7 50.9 22.4 2070 33.8 50.9 22.4
54 2100 33.8 51.1 22.4 2130 34 51.4 22.4 2160 33.8 51.4 22.5 2190 33.8 51.6 22.5 2220 33.8 51.6 22.5 2250 33.6 51.6 22.5 2280 33.7 51.9 22.5 2310 33.9 51.9 22.5 2340 33.9 52 22.6 2370 33.9 52 22.5 2400 33.8 52 22.5 2430 33.6 51.9 22.4 2460 33.9 52.1 22.5 2490 33.9 52.2 22.5 2520 34 52.5 22.7 2550 34 52.4 22.7 2580 34 52.4 22.6 2610 34 52.5 22.7 2640 33.8 52.5 22.8 2670 33.7 52.7 22.8 2700 33.6 52.8 22.7 2730 33.6 52.7 22.7 2760 33.6 50.3 22.8 2790 33.6 51.8 22.8 2820 33.8 51.9 22.8 2850 33.8 52.5 22.8 2880 33.7 52.8 22.8 2910 33.8 52.9 22.7 2940 33.8 53 22.8 2970 34 53.2 22.6 3000 33.8 53.2 22.5 3030 33.8 53.3 22.5 3060 33.9 53.4 22.5 3090 33.9 53.3 22.5 3120 34 53.6 22.5 3150 34 53.9 22.5 3180 34.1 53.8 22.5 3210 34.3 53.8 22.6 3240 33.8 53.7 22.4 3270 33 52.6 22.4
55 3300 33.2 52.2 22.5 3330 33.3 52.2 22.5 3360 33.5 52.6 22.5 3390 33.7 52.9 22.6 3420 33.8 53.3 22.6 3450 33.9 53.3 22.5 3480 34 53.4 22.5 3510 34 53.6 22.5 3540 34.1 53.6 22.5 3570 34.1 53.9 22.5 3600 34.1 54 22.5
Prototype II
Time In Air Air in Front out °C °C °C 0 29.3 40.7 21 30 29.4 39.5 21.2 60 29.5 38.7 21.5 90 29.6 38.4 21.4 120 29.4 38.4 21.5 150 29.4 38.6 21.5 180 29.6 38.9 21.5 210 29.6 39.3 21.6 240 29.5 39.5 21.6 270 29.8 39.9 21.7 300 29.9 40.2 21.7 330 30 40.7 21.8 360 30.1 40.8 21.8 390 30.1 41.1 22 420 30.2 41.4 22 450 30.4 41.8 22 480 30.5 42.2 22 510 30.4 42.3 22 540 30.5 42.6 22 570 30.5 42.9 21.9 600 30.5 43.1 21.9 630 30.5 43.4 21.9 660 30.4 43.7 21.9
56 690 30.5 44.2 22.1 720 30.6 44.3 22.1 750 30.6 44.5 22.1 780 30.6 44.8 22.1 810 30.6 44.9 22.1 840 30.7 45.2 22.1 870 30.7 45.2 22 900 30.9 45.4 22.1 930 30.9 45.5 22.1 960 30.9 45.8 22.2 990 31 46.1 22.2 1020 31 46.3 22.2 1050 31 46.4 22.2 1080 31.1 46.5 22.2 1110 31 46.7 22.2 1140 30.9 46.8 22.2 1170 30.9 47 22.1 1200 31 47.2 22.1 1230 30.8 47.5 22 1260 30.9 47.5 22.1 1290 31 47.8 22.1 1320 31.1 47.9 22.2 1350 31.6 48.3 22.2 1380 31.8 48.5 22.2 1410 32.1 48.5 22.2 1440 32.3 48.5 22.2 1470 32.5 48.6 22.5 1500 32.7 48.7 22.6 1530 32.9 48.6 22.5 1560 33.1 48.7 22.5 1590 33 48.7 22.4 1620 33.3 48.7 22.3 1650 33.4 48.9 22.3 1680 33.4 49 22.3 1710 33.5 49.2 22.2 1740 33.6 49.4 22.3 1770 33.8 49.6 22.3 1800 33.8 49.9 22.3 1830 33.9 50.1 22.4 1860 33.9 50.2 22.4
57 1890 33.9 50.3 22.4 1920 33.8 50.5 22.4 1950 33.8 50.6 22.5 1980 33.7 50.6 22.4 2010 33.8 50.7 22.4 2040 33.7 50.9 22.4 2070 33.8 50.9 22.4 2100 33.8 51.1 22.4 2130 34 51.4 22.4 2160 33.8 51.4 22.5 2190 33.8 51.6 22.5 2220 33.8 51.6 22.5 2250 33.6 51.6 22.5 2280 33.7 51.9 22.5 2310 33.9 51.9 22.5 2340 33.9 52 22.6 2370 33.9 52 22.5 2400 33.8 52 22.5 2430 33.6 51.9 22.4 2460 33.9 52.1 22.5 2490 33.9 52.2 22.5 2520 34 52.5 22.7 2550 34 52.4 22.7 2580 34 52.4 22.6 2610 34 52.5 22.7 2640 33.8 52.5 22.8 2670 33.7 52.7 22.8 2700 33.6 52.8 22.7 2730 33.6 52.7 22.7 2760 33.6 50.3 22.8 2790 33.6 51.8 22.8 2820 33.8 51.9 22.8 2850 33.8 52.5 22.8 2880 33.7 52.8 22.8 2910 33.8 52.9 22.7 2940 33.8 53 22.8 2970 34 53.2 22.6 3000 33.8 53.2 22.5 3030 33.8 53.3 22.5 3060 33.9 53.4 22.5
58 3090 33.9 53.3 22.5 3120 34 53.6 22.5 3150 34 53.9 22.5 3180 34.1 53.8 22.5 3210 34.3 53.8 22.6 3240 33.8 53.7 22.4 3270 33 52.6 22.4 3300 33.2 52.2 22.5 3330 33.3 52.2 22.5 3360 33.5 52.6 22.5 3390 33.7 52.9 22.6 3420 33.8 53.3 22.6 3450 33.9 53.3 22.5 3480 34 53.4 22.5 3510 34 53.6 22.5 3540 34.1 53.6 22.5 3570 34.1 53.9 22.5 3600 34.1 54 22.5
59