10 Grant Award Report Ack Wl

7/27/2019 10 Grant Award Report Ack Wl

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Harvesting Solar Energy From Asphalt Pavement

Undergraduate Research Grant Report Spring 2010

Budget Report

Since the project started from last semester and the Undergraduate Research Grant was

awarded a little late, we were able to borrow some monies (secured for purchasing solar panels

for the second phase) from URI Foundation account to purchase necessary items, e.g., PEX pipes

etc. Copies of purchase orders have been attached in this report. Thus, the grant award will be

used instead to fund the second phase of this project as it runs into the summer months. This

phase is the inclusion of rigid and flexible solar panels as comparisons to each other to see what

is more efficient to use in real life applications. The grant award will be used specifically for the

solar panels themselves, charge controllers needed for the panels, and the associated battery banks for harnessing the electricity generated from the panels. After purchasing, we can provide

receipts for solar panels also, if needed for further proof. The project summarized below was the

same one that was explained in the abstract for the research grant initiative. This part of the

project is the one that is always ongoing and will continue when other phases of the project are in

motion. The solar panel phase is one that needed to be accessed immediately, so as to be ready

for the summer months.

Project Summary

The apparatus must be tested using regular asphalt layers that are local to Rhode Island

before it can be used to test different contents and methods of extraction. There were five layers

in total, these layers are (bottom to top) a 5 in. subgrade soils, a 12 in. granular subbase, a 3 in.

Hot Mix Asphalt (HMA) base layer, a 2 in. HMA binder course and a 2 in. Class I-1 HMA

wearing course. These layers were be made following the RI Department of Transportation

(DOT) Standard Specifications for Road and Bridge Construction (Blue Book), as well as

associated AASHTO procedures for pavement construction. These thicknesses were chosen because it has been found that temperature becomes constant within a pavement structure at this

depth (Gui et al. 2007). This would be the basis behind the control layers, since further testing

will need to be done to find optimal asphalt contents (OACs) in the specific layers.

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To set up the apparatus for testing, holes were drilled in the exact center in the walls of

plexi-glass at two inches down from the top lip. These holes are ½ in. size, and are used to

accommodate the ½ in. PEX tubing that will be used for thermal extraction, explain later in the

procedure. The ½ in. piping was determined as the control, since it is the middle size of the three

different pipe diameters (1/4 in., ½ in., and ¾ in.). The side of the apparatus should be marked

with a marker at the desired layer thicknesses. For example, the subgrade soil level will be

marked 3 in. above the base of the apparatus. These marks were be used as a guide for the

compaction of the layers within the apparatus.

To monitor the temperature within the apparatus there were 10 thermocouple ends used

through it. These ensure for constant monitoring of the apparatus without having to destroy any

part of it. The surface layer of asphalt would be monitored by a laser thermometer directly in the

center. Each of the thermo couples was placed at either the middle of a layer, or when there is

contact between two layers. The length of the wire for the thermocouple shall be long enough to

make sure the tip of the wires are in the direct center of the area they are in. This ensures for a

constant temperature reading throughout the apparatus, directly in the middle of the diameter of

it. These wires will have the appropriate connects at the ends hanging out of the apparatus, so

that they can be easily attached to a thermocouple reader to attain the temperatures for the

different layers in the apparatus.

The apparatus was first filled with enough subgrade soils so that it reaches its mark on the

side of the plexi-glass when compacted to 95% of its optimum density. This percentage was

constant for each layer, as it is a specification by the RI DOT. Compaction was done with an

11.25lb circular weight with an 8 in. diameter which was dropped from a height of 2 in. with

enough repetitions to reach the density needed. The layer should be added in thirds so as to

accomplish evenly distributed load impacts for an optimal compaction. When proper density is

reached, and the layer meets the required thickness, the granular subbase can be added. This

layer was added like the layer before it and was compacted to it associated level. Next the

asphalt base course was added and compacted in a similar fashion. All asphalt layers were made

by AASHTO procedures, and tested as such. When the base course is compacted into place, this

is the time to snake the PEX pipe through the apparatus. Cover the tip on the pipe with taped so

that the diameter is cover in a way that particles will not be able to go inside. Snake the pipe

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through the drilled hole in one side of the apparatus and a put it through the hole on the opposite

side. Pull enough length of pipe through so that it reaches the water reservoir on one side, and

the pump on the other side. The asphalt binder course should then be placed on top of the pipe

and compacted so that the pipe is sandwiched firmly between the base and binder course. The

wearing course should then be placed as the final layer on the top and compacted till it is even

with the top lip of the apparatus.

The entire pavement structure in the apparatus should be given a day to cool and settle

before heat testing. After this period, the piping system should be check to make sure there are

no obstructions in the system as well as the apparatus. Again the structure should be given some

time to rest, as a way to keep the entire apparatus at one constant temperature before testing. To

begin testing heat should be applied by direct light from the heating lamp assembly. The light

should be about 6 in. above the lip of the apparatus so that there is a sufficient amount of heat

transferred. The lamp will remain on for a period of at least 8 hours, so as to replicate a normal

day of uninterrupted sunshine. This is based on the diurnal solar radiation cycle for the area of

Southern RI and should be able to replicate the hottest day in the summer. Temperatures should

be recorded from on the surface as well as the middle of each layer every hour, including at least

8 hours after the lamp is turned off. This will create a normal graphical relationship between

time of day and depth of temperature recorded which should be used a control setting. This

should be done for three days, so as to find any differences in the control group.

After this initial control testing, cooling from water circulation was appliedwas

applied. The pump should be turn on during a normal testing period after about 3-4 hours of

sunlight, or at a point of maximum temperature that would be found using the control graph

relationship. The pump should remain on for at least 8 hours, this time can be changed, but it has

been found that this time duration will be the most suitable for this type of application. Again

temperatures should be taken as before, but now temperatures from the piping system should

also be taken into consideration. The water temperature in the cool water reservoir should

remain constant, as it will act as a base temperature to measure the amount of thermal heat

extracted. The temperature should be recorded at the exit of the pipe from the apparatus, or at a

point before the water returns to the reservoir. This temperature will be the final temperature,

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and it will be compared to the cool water temperature which will be the initial temperature. The

difference is the amount of heat that was extracted from the apparatus.

This testing should be done for at least 3 days for each type of test, no pump and pumped

water, to see if there are any differences between the recorded data. The pump durations can be

changed as seen fit through testing. If the time duration is changed, then the testing will just go

on for three days with the current setup. By the end of this control testing, optimal pump

duration should be found, as well as the time in which to apply the pump can be specified. This

testing will be a base testing to so how things differ with different blends of asphalt courses, and

the use of different diameter pipes within the piping system.

In the end of the preliminary testing session everything seemed to be running

smoothly. The next step in this process was to run the water system to find an optimal time

running. This would not only be a test of the biggest difference in temperatures, but for how

long can it replicate the temperature change. Base temperatures were found so that they can be

compared to the water system temperatures to see if there will be a noticeable difference. There

were some errors that could have occurred during this testing period. The timing for each of the

intervals may not be exactly the same time each hour, but they were done to as close to hour

intervals since it was a human interaction to gather this data. This may results in a small change

of temperature for each layer per hour. Also the ambient temperature in the room may change

randomly, which would affect the outside of the apparatus, which may unfortunately cool the

interior slightly. The test cycle it seems to be a little off, since the temperature only gets back to

about a twenty degree difference with their initial temperatures. This could be from the fact that

the cycle is not a twenty four hour cycle, but a shorter sixteen hour one; so in turn the asphalt

does not have enough time to cool sufficiently. Other than these few sources of error the project

itself has been a success. This seems to be the beginning for what may be a length testing period

ahead. There are some more variables that can be tested in the future, as in the pipe diameter,

heat light distance, time for water system to be on, and many others. This is just the base

information that was needed in order to move on towards other testing, it may take some time,

but hopefully the end results will be useable in real world applications

The diameter would be large enough to encompass the passing of one pipe though the

system, since it is also a way to test for the area affected by thermal extraction (Chen et al.).

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There are three different diameters for pipes: ¼ in, ½ in, and ¾ in. This would be done to

generate a relationship between the diameter of the pipes and the amount of heat extracted. The

pipes themselves will be PEX type A, this was chosen over a tradition copper pipe because the

PEX pipes encompass the same thermal properties, but are more flexible that copper. This will

in turn lessen the heat losses due to joints with in a piping system, since these will be lessened

greatly. These pipes will be connected within a pumping and cooling system. The pump will

pump cool water from a constant reservoir and will feed a certain diameter PEX pipe which will

go through the plexi-glass cylinder through the asphalt pavement, extract heat from the asphalt,

and then return to the cool water reservoir so that system is closed. The materials for building

the device was ordered as shown in the Appendix A.

The pipes were placed between the binder course and base layers. This depth is sufficient

enough for thermal extraction (Asaeda 1996), and is also at a depth where the pipes will not be

disturbed by maintenance or loads on the layers above. Absorbtivity must be taken into account,

since this is the one factor that will determine the feasibility of this type of pavement structure

(Pomerantz 2000). Also layer temperatures can be predicted by either AASHTO T317-02

(Prediction of Asphalt-Bound Pavement Layers Temperatures) or by using the Enhanced

Integrated Climatic Model (EICM) (NCHRP 2004). Layer temperature prediction was useful in

testing. This generated a relationship between expected and experiment values, to see the

percentage of error within in testing.

As stated before to test for thermal extraction from asphalt, a plexi-glass cylinder and

PEX pipe system were used. Plexi-glass was used to see how the layer reacts to compaction, as

well as heating. Also it allows for a way to see the different layers within the pavement

structure, as well as a way to drill into specific locations through the entire depths for

temperature readings. These reading were taken from each layer as a way to generate a

relationship between the pavement depth and temperature (Asaeda 1996). Temperature readings

were also taken from the cool water reservoir, for a base temperature, and from the exit outlet

from the plexi-glass cylinder, for an end temperature. This gave a temperature difference that

can be graphed to show heat absorption of the water. This is the heat extracted from the

pavement structure. When this heat is extracted, a certain volume of structure would also cool

with a certain area of exposed asphalt. This was seen as a difference in the temperature readings

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throughout the structure. Heat was applied to the asphalt in the way of a radiant heating lamp, to

a degree that matches the expected solar radiation in a given area in RI (Bakirci 2008). The

asphalt pavement structure is expected to heat up as time goes on, and this heat transfers

throughout the structure as time increases. When the pump is turned on after a given amount of

time, the structure should be seen to cool from the area of the pipes outwards. As the area

surrounding the pipes cools, this in turn should bring the heat out of other areas in the structure

since it will want to stay a constant temperature (Chen et al.)

One change to the aforementioned procedure was the exclusion of the pump from the

entire system. This was done because unfortunately the pump was experiencing mechanical

problems at the time of testing. Since time was a factor and another pump could not be found, it

was replaced with a wall faucet. This was simply a sink faucet that was in the laboratory area,

and was capable of connecting to the system itself. Testing on this faucet showed that it would

transport the same amount of water per minute as the pump (5 gallons/ minute). Also the water

from the faucet would remain constant since it is continuously coming from the same source.

This is actually a plus over the pump, since the pump would cycle water in a tub; the water

would increase in temperature over time due to the ambient temperature in the laboratory,

thermal heat exchange from the pavement, and heat from the pump running, just to name a few

factors. In the future a pump will be used, as not to waste water, and so the flow can be changed

depending on experimentation

As previously stated, the first rounds of tests were performed to determine expected

values of temperatures in the apparatus. This was done so that comparisons can be made on the

difference of the temperatures throughout the pavement structure. In the base phase of testing,

this was accomplished by running water through the PEX system at full flow and recording the

associated temperatures as before, with the water running for eight hours, beginning in the

middle of the “day” and ending halfway through the “night”. This new data can then be

compared to the base values of just sunlight. Also the data can be used for future comparisons of

different flow values through the PEX system. This is to determine the optimal flow for the

water through a half inch PEX pipe.

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Importance of the Project

This project holds an importance to me because it is the beginning of my master thesis for

graduate school here at URI. I feel as though I have put a lot into this project over the past year,

and to see it goes from planning stages to construction stages, and finally to data collection

stages, is quite amazing to me. I feel as though a lot has happened over the past year that I hard

to put in words, but I do have to say one thing and that is that this project is only at its beginning.

This is only the beginning for a promissingpromising research project into greener technologies

for every dayeveryday use. Hopefully this type of research can be used into future technologies

or can be used with future research to continue the greener aspect. I only can foresee myself

continuing with hard work on this project to see it come to fruition, or at least to a point that I

can pass it on to future researchers.

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