1. BEng Mechanical Engineering
Design and manufacture of a solar tracking device
for implementation of a method for biofuel
production
Mohamed Shafeeqdeen MOHD RAFIK
May 2015
Professor Patrick Fairclough
Thesis submitted to the University of Sheffield in partial fulfilment of
the requirements for the degree of
Bachelor of Engineering
Department
Of
Mechanical
Engineering
2. ii
SUMMARY
A research was carried out to investigate the potential in converting Sun’s energy into
liquid fuel hydrocarbon by using algae as a medium. This step involved using a solar
tracking device that concentrates UV radiation from the Sun into algae via Fresnel lens.
To maximise the potential,solarpanel was to be used to power the tracker, indirectly the
Sun itself. Research was done to obtain the tracker’s daily power consumption at
different seasons as the Sun’s position will differ throughout.
Once the tracker is powered, it starts concentrating sunrays into the algae. UV had to be
filtered out from these mixed electromagnetic rays. Thus, a device had been designed;
incorporated with a UV pass filter that needs cooling when used due to absorption of
other rays. So, water cooling system was integrated with the design. After
manufacturing thefinal design, thedevice was tested in a laboratorycondition with a UV
light source and constant tap water flow for cooling system. The device worked well at
projecting the incoming UV onto algae cells for range of durations while simultaneously
keeping the UV filter safe from cracking. However, it seems to limit its performance as
UV dose duration increases.
3. iii
NOMENCLATURE
Roman Characters
A Cross-sectional Area (m2
)
F Force (N)
M Moments (Nm)
V Voltage (V)
I Current (A)
t Time (s)
r Radius (m)
d Distance (m)
v Velocity (ms-1
)
P Power (W)
E Energy (J)
TSI Total Solar Irradiance (W/m2
)
Q Volume Flow Rate (m3
s-1
)
Cp Specific Heat Capacity (J kg-1
K-1
)
NaCl Sodium Chloride
Greek Characters
ω Angular speed (rad s-1
)
α Angular difference
ρ Density (kg/m3
)
Subscripts
max Maximum value
A At the point A
H Horizontal direction
4. iv
V Vertical direction
CONTENTS
Summary.............................................................................................................ii
Nomenclature....................................................................................................iii
Contents.............................................................................................................iv
Acknowledgements...........................................................................................vi
1 Introduction..................................................................................................1
1.1 Background ................................................................................................1
1.2 Project Aim.................................................................................................4
1.3 Project Objectives......................................................................................4
2 Literature review – Solar tracker .................................................................5
2.1 History ........................................................................................................5
2.2 Slight Enhancement...................................................................................9
2.3 Electronic Parts Data................................................................................10
3 Solar Power Integration Research .............................................................10
3.1 Research on Sun’s positions in Sheffield.................................................10
3.1.1 Horizontal Motion Time Calculation......................................................12
3.1.2 Vertical Motion Time Calculation..........................................................13
3.2 Arduino Microchip Programming............................................................14
3.3 Data Collection.........................................................................................17
3.3.1 Measured Data.......................................................................................17
3.3.2 Calculated Data......................................................................................18
3.4 Results & Analysis ....................................................................................19
3.5 Discussions ...............................................................................................23
4 UV Filter & Algae Holder – Design.............................................................24
4.1 Design Aim ...............................................................................................24
4.2 Design Criteria..........................................................................................24
4.3 Design Proposal........................................................................................25
4.3.1 Initial Design...........................................................................................25
4.3.2 Improved Final Design ...........................................................................26
4.4 Manufacturing Materials List ...................................................................28
4.5 Parts List & Function................................................................................29
4.5.1 Top Plate.................................................................................................29
4.5.2 Main Body...............................................................................................29
4.5.3 Algae Chamber.......................................................................................30
4.5.4 Quartz glass............................................................................................31
6. vi
ACKNOWLEDGEMENTS
The author of this project would like to thank Professor Patrick Fairclough and PhD student
Thomas Sydney for their time, guidance and patience throughout the completion of this
project. Also, the author would like to point out much appreciation for the full
cooperation given by the technicians at the workshop of mechanical engineering
department, mainly the manager Karl Rotchell, during parts manufacturing.
7. 1
1 INTRODUCTION
1.1 Background
In 1973, following the Yom Kippur war, there was an oil crisis which shocked the world
with the increasing oil price as shown in figure 1.1 below. (1) Countries in the
Organisation for Economic Cooperation and Development (OECD) made of United
States, Japan, Germany, France, United Kingdom, Italy and Canada then responded to
the disaster by becoming more oil efficient. For the following decade, their total oil
imports descended by 14% while they still managed to grow their Gross Domestic
Product (GDP) by 19%. Coal and nuclear energy source utilisation greatly increased as a
substitute. (2) Energy conservation became priority.
The crisis effect on Brazil’s economy was catastrophic. Brazil relied on imports for over
80% of the country’s oil consumption during that year. As oil price kicked in, their import
bill went twofold higher, from $6.2 billion to $12.6 billion which caused their trading
balance to collapse. To recover their energy costs, Brazil implemented Second National
Development Plan (1975-1979) that gave them hydroelectricity & nuclear power sources.
With it, Brazil also introduced alcohol production from their sugar cane as a major means
of substitute to their oil imports, thus the biofuel production. (3) Since then, fuel ethanol
has been a major exported commodity of Brazil. It grew about 17 time more for the
exporting industry between the years 1998 and 2005. The average wage for this sector
were higher than the mean for all other sectors. (4)
If sugar cane was the key substrate for Brazil, the United States had corn in their hands.
With starch-based ethanol from corn, the United States worked its way up to be the
second major fuel market at that time. The fuel production market went skyrocket in
2002 , after the banning of methyl tertiary butyl ether (MTBE) due to its oil spilage, and
increased about 7 times more for the following decade as shown in figure 1.2. (5)
8. 2
Figure 1.1 – Historical Oil Price, yearly averages (6)
Figure 1.2 – Historic Fuel Ethanol Production in the United States (7)
0
2000
4000
6000
8000
10000
12000
14000
16000
1975 1980 1985 1990 1995 2000 2005 2010 2015
MillionsofGallons
Year
9. 3
All these data above, being a clear evident, shows and agrees with the high potential
growth of biofuel as a substitute to the widely used gasoline and other petrochemical
liquids. That’s probably because, as we all know, solar energy is a free, non-depleting &
non-polluting ultimate energy source and with the present limit of technology, liquid
hydrocarbons are the most preferred & convenient way of carrying stored energy. Thus,
transforming the solar energy directly into liquid hydrocarbon presents itself as an
attractive process & progress.
Not only sugar cane and corn, but there are many other plants that synthesis
hydrocarbons through solar power, nutrients and fertilisers. (8) Some examples are such
as soybean, cotton seed, peanut, oil palm and algae. However, the problem arises as
more farming crops, especially food crops, are being fed to the production of biofuel. It
contributes directlyto the increase in price for food. (9) The after effect was the dramatic
world food price crisis which occurred in 2007 & in the first 2 quarters of 2008. (10) Algae,
on the other hand, present itself as a promising live feedstock for the production of
biofuel. Primarily, because of its high hydrocarbon contents that can reach major
proportion of the total plant’s mass. (11) Hence, cultivation and harvesting algae for
biofuel will be able to produce much higher oil yield than any of the present sources as
shown in figure 1.3.
10. 4
Figure 1.3 – Oil Yield of Feed Stocks for Biofuel (12)
This present thesis draws theattentionof algaeas a medium of converting solar energy
into hydrocarbonliquid fuel as a means of stored energy. In order to produce feasibleand
affordablebiofuel,maximum solar energy usage has to be integrated in theprocess of
biofuelproductionfrom algaeas it is a free and non-diminishing energy source. Thus,
thisproject involves usage ofdirect UVand sunlight from the sun to break down algae
cells into lipidsandproteins. Lipids are then converted to biofuelthrough
transesterification. (12) Also, theproteinas a by-product can beprocessed into food
source to help reduce world food prices. (13)
1.2 Project Aim
The overall aim of this project is to maximise solar energy in algae biofuel production by
developing and enhancing a solar tracking device, which concentrates UV from the sun
into algae to break its cells into lipids and proteins thus making biofuel an economically
viable solution.
1.3 Project Objectives
1. To enhance the solar tracker to track the sun accurately and periodically
11. 5
2. To power the solar tracker using solar power to reduce energy cost
3. To designa devicewhich holdsUVfilter and algaeat thefocallength of the lens
4. To integrate water-cooling system for the UV filter in the holding device where
the extracted heat can be further used to heat an algal growth chamber for
optimum growth
2 LITERATURE REVIEW – SOLAR TRACKER
2.1 History
Sam Davidson, a 2nd year MEng student from the University of Sheffield designed the
solar tracking device. It was designed to collect the UV radiation from the sun to break
down the algae cells. He used a Fresnel lens to focus about 0.28m2 area of sunlight into
an area, A of just 0.0025m2 to radiate concentrated sun’s UV onto the algae samples. The
tracker also, as its name suggests, has to track the movement of the sun and orientate
the lens so that it is always perpendicular to the incident sunlight. Maximum tilting angle
in Sheffield is about 57o, the highest solar angle the sun reaches and his design
accommodated up to 60o angle tilting on the solar tracker. (14)
The design was quite fascinating, where it was based on a cubic frame with Light Diode
Resistance (LDR) mounted on each of the 4 corners to measure light sensitivity. Fresnel
lens mounted onto the middle of the frame, with sliding capability along the frame to
adjust and control the focal point of the lens. A large square metal sheet attached at the
otherend of theframe, which acts as a platformto holdalgaesamples at the focallength
of the lens. This whole frame was then attached to a Lazy Susan turntable to allow
motion that tracks the sun as shown in figure 2.1.
Platform
12. 6
Figure 2.1 – Front view of the Solar Tracker (15)
With this design, the square platformis always parallelto the mounted Fresnel lens and it
works on a dual axis basis which allows motion for solar tracking. First motion is where
the whole frame revolves around the turntable to give horizontal displacement, which
follows the azimuth angle of the sun. Second motion, following the zenith angle of the
sun, is where the device tilts the platform and lens together to get incident sunlight rays.
This is done by a heavy duty linear actuator while supporting the whole weight of the
lens and the platform as shown in figure 2.2.
Figure 2.2 – Rear View of the Solar Tracker (15)
Electronic Module
Platform Rear
13. 7
The figure 2.2 also shows the dc motor and pulley, which drives the primary circular
motion around the Lazy Susan turntable. Linear actuator with its motor mounted on the
back of the platform frame where it extends and retracts its arm to control the elevation
angle of the device. These two motors are connected and controlled by Arduino
microcontroller chipset that responds to the digital measurement of light sensitivity of
theLDRs. Themicrocontroller is placed in the electronic module box to keep it safe from
exposure to water. A limit sensor is added to prevent full extension of the linear actuator
that will break the device when it is at its lowest angle as shown in figure 2.3. The
actuator is in a rest position when the device is at its highest elevation angle as shown in
figure 2.4.
Figure 2.3 – Tracker at its lowest angle (15)
Limit Sensor
14. 8
Figure 2.4 – Tracker at its highest angle (15)
As mentioned earlier, the linear actuator holds the whole weight of the lens and the
platform. In figure 2.5, the diagram shows force resulting on actuator as the tracker tilts
to its maximum angle. This can simply calculated using force balancing formula. The
actuator used has a maximum force, Fmax limit of 4000N. Calculation shows that the
maximum reached force in this device is only 75% of it.
15. 9
Figure 2.5 – Resultant force of the Linear Actuator (15)
[All measurement are in mm units and gravitation acceleration, g = 9.81 Nm-2]
The device is hinged at joint A, thus taking the moment at A, MA = 0.
CW @ A +ve: ∑MA = 0 [Equation 2.1]
Fmax sin 3o x 139 – 15g cos 60o x 300 = 0
This gives the maximum value for F as:
Fmax = 3034 N
It follows from the assumption stating that the combined load of lens and platform is
about 15kg. When the actuator initiates, it will definitely exceed this maximum force
value. However, the acceleration is so small that this extra acceleration force is
negligible. Hence, the 4000N maximum limit was sufficient for this design. (15)
2.2 Slight Enhancement
The device was working well at tracking the sun. The PhD supervisor, Tom Sydney has
been using the tracker since the start of the semester. However, there was a slight
problem with the magnification area of the focused point. Under the sun, it was slightly
larger area than it was supposed to be. Tom diagnosed the problem and came up with
the solution to increase the length of the LDR shades.
Tom’s new shade design was pretty much the same except the shading length increased
about 2.8 times more than the previous shade. After having it manufactured from the
workshop and assembled them at each of the LDR corners, it was tested and it indeed
helped to reduce to area of the focused point. This time the area was much nearer to the
expected value of about 0.0025m2.
16. 10
2.3 Electronic Parts Data
Part Electronic Device
Rotating mechanism Driven by a geared 12V DC motor with low output
speed. Mechanicaldrive from a pulleymoving around
a timing belt adhered to the Lazy Susan bearing.
Tilting mechanism Employs a 12V DC linear actuator to tilt lens and
platform together. Max load 4000N. Applied load
reaches about 75% of this value
Programming and electronics Arduino mega 2560 with motor shield. 12V output
across each motor. Max current, I = 2A.
Table 2.1 – Electronic Parts Data
Table 2.1 shows simple technical specification of the electronic items used in the solar
tracking device.
3 SOLAR POWER INTEGRATION RESEARCH
3.1 Research on Sun’s positions in Sheffield
Figure 3.1 belowshows a normal sun path diagramin Sheffieldarea that is at 53oN. In this
figure, it agrees with themaximum tilting angleneeded for thedevice to meet theZenith
angle is about 60o. This occurs during the summer period. However, the range for the
Azimuth anglevaries largelythroughout theyear where it goes through about 2700 angle
change in a day during summer whereas only 90o during winter days.
17. 11
Figure 3.1 - Sun Path Diagram on November 17th 2014 (16)
Using SunEarthTools website, more detailed information on the angular position of the
Sun at specific time intervals were obtained (17). The site even gave the data in an excel
file format, which made it easier to analyse. This data combined with the speed
parameters of the solar tracking device provided by Sam Davidson; calculations of the
active tracking time of the tracker were possible. One of the tabulated data examples is
shown in Table 3.1 below.
Date: 21/12/2014
coordinates: 53.381129, -1.470085 (Sheffield)
No Hour Elevation Azimuth Motion Time
230 Horizontal (s) Vertical (s)
1 08:19:10 0 130.34 68.26027397 0
2 08:30:00 0.37 132.5 1.479452055 0.112217
3 09:00:00 3.5 138.63 4.198630137 0.949181
/ November 17
18. 12
4 09:30:00 6.27 144.95 4.328767123 0.840032
5 10:00:00 8.63 151.47 4.465753425 0.715714
6 10:30:00 10.53 158.17 4.589041096 0.576225
7 11:00:00 11.94 165.04 4.705479452 0.427628
8 11:30:00 12.83 172.02 4.780821918 0.269926
9 12:00:00 13.18 179.07 4.828767123 0.106151
10 12:30:00 12.97 186.13 4.835616438 0.063691
11 13:00:00 12.23 193.13 4.794520548 0.224433
12 13:30:00 10.95 200.03 4.726027397 0.388203
13 14:00:00 9.17 206.78 4.623287671 0.539835
14 14:30:00 6.93 213.35 4.5 0.679327
15 15:00:00 4.27 219.72 4.363013699 0.80668
16 15:30:00 1.23 225.9 4.232876712 0.921894
17 15:48:43 0 229.66 2.575342466 0.37304
Table 3.1 – 30 min-1 Frequency Data on Sun’s Position on Winter Solstice
Using the speed parameters in Table 3.2 below, the motion time for horizontal and
vertical axis were calculated. The horizontal motion is quite straight forward calculation
whereas the vertical motion needs a few steps to convert the degree change into
distance travelled by the linear actuator.
Parameters Value
Lazy Susan turntable (Horizontal) 1.45o/s
Linear Actuator (Vertical) 8mm/s
Table 3.2 – Parameters of the Solar Tracking Device
3.1.1 Horizontal Motion Time Calculation
As obvious as it can be, motion time are equal to distance divided by speed. For the
horizontal time,
19. 13
Horizontal time = azimuth angle difference / angular speed
tH = α / ω [Equation 3.2]
tH = (230 – 130.4) / 1.45
= 68.26 s
This calculation is an example for the first horizontal motion time in Table 3.1.
3.1.2 Vertical Motion Time Calculation
For the vertical motion time, a diagram as shown in figure 3.2 had to be set up to ease
the calculations. The diagram shows the linear actuator straight path line as well as the
hinged part A that was shown previously in figure 2.5.
Figure 3.2 – Diagram to help vertical motion time calculation
The purple line shows distance to be travelled by the actuator. To get to a specific
elevated angle, the linear actuator has to go through a few distances through its path
line. This can be calculated using the elevation angle from the diagram above. Since the
dotted line and the vertical line are of same length, a simple perpendicular bisector
method was used to calculate the length of distance to be travelled. The figure 3.3 below
shows the same triangle in another orientation.
Figure 3.3 – Perpendicular Bisector line
Path Line of
Linear Actuator Hinged at A
Distance to travel
Elevation angle
20. 14
The red line represents perpendicular bisecting line. Hence, the purple line length which
represents distance to travel by linear actuator can be calculated via:
Distance to Travel, d = [2 x r x sin (zenith angle difference/2)]
Time to Travel, tV = d/ Velocity,v [Equation 3.3]
tV = 2 x 139 x sin [(0.37-0)/2] / 8
= 0.1122 s
This calculation is an example for the first vertical motion time in table 3.1.
So, these calculations give a rough estimation on the active tracking time for the device.
From the table 3.1, it shows that for every half an hour time interval, the device will be
tracking for about 5 seconds maximum at every interval. An exception does occur on the
initial tracking point as it requires the tracker to return back to the east most position of
the sun from the last position of the sun on previous day (west). Thus, this device will go
through thisroutine dailyand will always have the longest active tracking time on its first
interval of the day.
3.2 Arduino Microchip Programming
From figure 3.4 below, it shows the original coding with no timer. This causes the chip to
continuously read the incoming signal from the LDRs, and as the light sensitivity
difference between the 4 LDRs go below a certain tolerance level; motors are activated
accordingly to move the tracker in certain direction. Once the tracker moves, the chip
reruns and re-reads the LDR signals instantaneously to check their tolerance level. This
repeats infinitively throughout till the time solar tracker is switched off. This was the
original code designed by Sam Davidson.
21. 15
Figure 3.4 – Initial Running Arduino Code
Here, in figure 3.5 below, the code has been modified. New time dimension was
introduced to the code. Every Arduino chip has its own sense of time using the function
‘millis’; it returns the time since the chip was switched on. With that, a timer can be
introduced, which basically runs a specific function for constant intervals. From the figure
3.5, the timer has been set to run the code every 60000 milliseconds or simply, a minute.
So, the chip will start ‘StartMotor’ function for every one minute pass by.
22. 16
Figure 3.5 – Reformatted running code to run with specific frequency
The next line which states ‘void StartMotor’ is the defining phase; it tells which codes to
run when the timer is up and ‘StartMotor’ is triggered. At the very start, the code always
updates the ‘StartTime’ constant. Combining this with a ‘while’ function, the Arduino
simply goes into a loop mode. As long as the statement inside the ‘while’ function is not
true, the chip will continuously run the defined codes under the ‘while’ function. (18)
In the ‘while’ statement, the difference between the current time (millis) and the
‘StartTime’ must be below a specific interval, in this case 3000 milliseconds, to
continuously run the original Sam Davidson’s code. Hence, for every 1 minute passed,
Timer Specific
Function
Defining
The Function ‘While’
Statement
(True/False)
23. 17
the tracker will start and track the sun movement for a maximum of 3 seconds. This is
how the new code works.
3.3 Data Collection
3.3.1 Measured Data
With all the programming done, next step involved direct data measurement of the
energy intake for the solar tracker. For this, a wattmeter, as shown in figure 3.6 below,
was used. It was a simple plug-in power device that monitors the current power
consumption and total energy used of the device plugged into it since it is switched on.
Figure 3.6 – Wattmeter Monitor
The initial plan was to measure accumulated energy of the device while it uses the newly
developed Arduino code. This can help to measure energy intakes for different
frequencies such as 1, 3, 5, 10 & 30 min-1 on the tracker. The accumulated energy
consumption then can be compared and analysed to produce the best frequency option
for the tracker. It will be also used for calculations to find a suitable solar panel & storage
that will provide the solar tracker’s independent power source.
However, a slight wiring problem was present with the solar tracker and it cannot be left
running for a day without supervision. So, the accumulated energy could not be
measured. However, only the instant specific power for both the motors and also the
standby power of the device could be measured. This data is shown in table 3.3 below.
24. 18
These values were computed to get an approach on the energy usage and got the results
analysed.
Parts Power, P (Watt, W)
Horizontal Motor 6
Vertical Motor 50
Standby Mode 2.5
Table 3.3 – Tabulated Measured Data
3.3.2 Calculated Data
With the simplest equation, where
Energy, E = Power, P x Time, t [Equation 3.4]
the energy required was worked out. The power value can be obtained from the table 3.3
and the time variable can be obtained from the horizontal and vertical time motion.
When the device is stationary between motion times, it turns into standby mode which
consumes extremely low energy. By constantly adding these energy values at each
interval; one could work out the accumulated energy, which is needed for a day by the
tracker. But, the most affecting factor in this calculation method is the constant motor
start-up time.
Usually, a motor takes about 500-800ms for its inertial start-up that has to be considered
at each interval. This causes a significant different in energy requirement level when
applied to the variable frequencies @ 1, 3, 5, 10 & 30 min-1.
An example of the calculation method is shown below on table 3.4. It also shows the
energy requirement at each interval up to 10 intervals, the total time for the motors to
run, thetotalstandbyduration time in between motion & at night and the overall energy
required by the tracker for a day during Winter Solstice.
No Hour Motion Time
Energy (J)
Horizontal (s) Vertical (s)
1 08:19:10 68.26027397 0 65.26552
25. 19
2 08:30:00 1.479452055 0.112217 37.25569
3 09:00:00 4.198630137 0.949181 80.47282
4 09:30:00 4.328767123 0.840032 75.08092
5 10:00:00 4.465753425 0.715714 68.934
6 10:30:00 4.589041096 0.576225 62.0216
7 11:00:00 4.705479452 0.427628 54.65039
8 11:30:00 4.780821918 0.269926 46.80318
9 12:00:00 4.828767123 0.106151 38.63861
10 12:30:00 4.835616438 0.063691 36.51903
Motor Time (s) 153.7218 Motor Energy (J) 1748.374
Standby Time (s) 26819.28 Standby Energy (J) 67362.68
Night Time (s) 26973 Standby Energy (Night) (J) 118854
Daily Total Energy (J) 187650.6
Table 3.4 – Daily Energy Requirement Calculation for Winter Solstice
The same steps were repeated on the Summer Solstice and March Equinox for a variety
of frequencies @ 1, 3, 5, 10 & 30 min-1. The calculated data then were tabulated as shown
in table 3.5 below.
Time of the Year
Winter
Solstices
March
Equinox
Summer
Solstices
Frequency (minutes-1) 1 200533 J 218241.1 J 236749.5 J
3 191579.8 J 203831.5 J 216589.3 J
5 189829.9 J 200988.8 J 212558.2 J
10 188509.9 J 198797.5 J 209497.2 J
30 187650.6 J 197372.2 J 207160.6 J
Table 3.5 – Calculated Data for Daily Energy Requirement
3.4 Results & Analysis
By using a bar graph, the data can be analysed for the daily energy consumption during
different seasons of the year in Sheffield.
26. 20
Figure 3.7 – Bar graph Comparison of Daily Energy Consumption
The bar graph in figure 3.7 above shows that the energy consumption per day is getting
reduced as the tracker’s motion frequency reduces. This is quite true theoretically as
more frequent any device is, it takes a lot more energy to cover inefficiencies in parts.
Furthermore, thegraph also agrees that the difference between the energy consumption
of consecutive frequencies gets smaller as the trend goes. This means that, somewhere
along the frequency line, the energy difference will become almost negligible and that
perhaps will be the optimum frequency to run the tracker. However, this will not be the
limiting factor for this case.
As it was mentioned earlier, the tracker was mounted with a Fresnel lens. To track the
sunrays effectively, the lens had to be always inconsistent with the incident ray’s angle. If
the tracker did not move consistent enough, a large angle difference with the sunray’s
incident angle will be produced and the rays won’t be converged to its focal point. Thus,
it became an important factor when choosing the motion frequency of the tracker. In
simple words, if the device tracks using a large time interval, the Sun will be extremely
0
50000
100000
150000
200000
250000
Winter Soltice March Equinox Summer Soltice
Energy/J
Time of the Year
Daily Enery Consumption
1 minute
3 minutes
5 minutes
10 minutes
30 minutes
27. 21
off position and so does the sunrays. The converged rays will be completely off from the
focal point of the lens.
Figure 3.8 – Transmission Curve for Fresnel Lens (20)
So, the transmission curve of the lens (Traditional Fresnel lens 1) in figure 3.8 above has
to be studied and analysed. To get a high transmission that is above 90%, the angular
difference between the lens and the sunrays should be about ±0.6o. (19) Hence, the
average angular difference, α for different frequencies has to be compared as shown in
the table 3.6 below.
Frequencies (min-1) Average Angular Difference
1 0.22o
3 0.67o
5 1.11o
10 2.02o
30 6.32o
Table 3.6 – Average Angular Difference for Different Frequencies
28. 22
From comparison table 3.6, the 3 min-1 frequency seems to be the best choice although
the angular difference is slightly off by 0.07o. This reduces the transmission to about 85%
but it saves about 4.5% of energy on daily usage.
During summer and equinox, there is plenty of sunlight which gives enough solar power
to meet their daily energy consumption. Therefore, the problem arises during the winter
period where sunlight is extremely rare to be harvested.
Daily Energy Consumption (winter, 3 min-1) = 191579.8 Joules, J
= 53.22 Watt-hour, Wh
To be able to measure in 12 V battery storage = 4.435 Ampere-hour, Ah
So, to full fill the energy requirement, twice the actual battery size; about 10 Ah of 12V
battery capacity would be sufficient. Also, it’s a precaution to not completely drain out
the battery and also as a contingency measure as most lead batteries are only 85%
efficient in storing energy. (20)
By research, solar panels only produce a fraction of energy from sunlight during winter
compared to summer days. Winter assumption is that a specific power rated solar panel
will produce an hour worth of energy per day. (21) For example, a 70W rated solar panel
will produce about 70Wh energy per day in winters. So, to recharge the battery, about
120Wh capacity with an energy storage efficiency of 85%, it needs about 141Wh rated
thesolar panel. Best optionavailablewith that rating for the tracker is 150W solar panels.
The table 3.7 below shows all the chosen criteria for the solar tracker to be powered with
solar energy via solar panels & batteries so that it runs at optimum frequency
independently.
Feature Value
Frequency 3 min-1
12V Lead – Acid Battery 10 Ah
Solar Panel 150 W
Table 3.7 – Chosen Criteria for Each Feature
29. 23
3.5 Discussions
One of the key discussion points is on the solar power generated during winter. Although
it can be assumed that the panel could produce an hour worth of the rated solar energy
per day (21), it actually fully relies on the day’s weather which is naturally an
unpredictable phenomena. In real life cases, there will always be ups and downs in the
harvest of solar energy that will affect the tracker’s performance.
In case of poor solar panel harvesting efficiency due to weather, the tracker then will not
be powered effectively to function. It will cause an extremely low chance at directing the
UV light into algae, which affects the overall efficiency of the system in creating a
feasible biofuel from algae. So, to save energy using solar power, the system’s efficiency
seemed to be compromised. Decrease in system’s efficiency will only increase the cost of
biofuel production.
Furthermore, thenext big discussion on the line is the direct reliability and validity of the
calculated & computed data which has been used to simplify and analyse all these
theories. The bar graph on figure 3.7 although agrees with theory, it still comes from
calculated values based on incomplete collected data with uncertainties. Since the sun
tracking is an extremely weather dependent activity, there is really no way to justify if
these calculations would actually simulate real life conditions. The chances are very slim.
For instance, during cloudy & rainy days, the tracker would not be able to track the sun
accurately. This will confuse the tracker and might induce more motion time than the
calculated period.That day’s daily energy then might have been completely off from the
calculated value and the deviation from this value cannot be estimated or predicted.
Once again, the system’s efficiency had to be compromised for this action.
Therefore, as the supervisor pointed out, the data above cannot be heavily relied on due
to its extreme high uncertainties. No solar panels or the batteries were introduced with
the tracker as the data is full of uncertainties although it shows great potential through
research.
30. 24
4 UV FILTER & ALGAE HOLDER – DESIGN
Mentioned earlier, the trackers aim is only to track the sun. Once it tracks the sunlight,
the sunrays are captured using Fresnel lens and directed them into the algae. However,
only the UV light from the sunrays is needed as any other electromagnetic rays from the
sunlight will just harm the algae. Hence, a pro - UV filter is needed before the mixed rays
reach the algae.
The problem arises as the infrared and visible light being captured by the filter causes a
massive increase in the temperature of the UV filter. Therefore, a whole new design is
needed to get the UV filter together with an algae chamber. At the same time, the
designed product must be able to cool the filter to not let the temperature rise too high
with an integrated water cooled system. Running tap water is used to ensure that heat is
cycled out of thefilter. Also, as obvious it sounds, theproduct must be ableto let through
theconcentrated lightsall the way into the algae chamber via the UV filter. This was the
design phase of this project.
4.1 Design Aim
To design a product that holds UV filter and algae chamber with water – cooling system
for the UV filter.
4.2 Design Criteria
1. Allows concentrated sunrays at the focal length pass through the device into the
filter and algae chamber.
2. UV filter placed right before the ray hits the algae chamber to remove unwanted
electromagnetic rays.
3. Water cooled system integrated with the product to keep the UV filter cool
4. Material has to be heat resistant & strong to hold the UV filter in place when
running water passes through it.
31. 25
4.3 Design Proposal
4.3.1 Initial Design
The initial design for the product is shown below in figure 4.1. It composed of 3 major
body parts where, the first one on the top is the top plate, middle large one is main body
and the last part is the algae chamber. There are holes on the main body and algae
chamber, two on each side for inlet and outlet purposes.
Figure 4.1 – Initial Design CAD Isometric View
The sectioned view belowin figure 4.2 gives an ideaof how theinside looks like.The inlet
holes are shown and the circular cavity inside the product gives a large volume of water
to pass through. However, as you can see from the diagram, the black UV filter place is
not held properly by any support. This was the first flaw of the design. The filter is also
placed on top of a quartz glass on one side which will cause thermal imbalance on the
filter as one side of the filter is fully exposed to water and the other is not. Another
problem was the circular body which will cause many eddy currents in the flow of water
during cooling. The volume on the main body and the algae chamber was also too large
and had to be reduced. For the algae, a much narrower chamber was needed.
32. 26
Figure 4.2 – Initial Design CAD Section View
4.3.2 Improved Final Design
After a few improvements, a final design on the product was made. Tom had an amazing
idea to hold the UV filter in place with a rectangular glass at the sides. This will hold the
filter right in the middle and enables water to run along both sides’ surface of the filter.
The cavitiesinside thebodieswere changed to a rectangular shape to reduce turbulences
during flow as my supervisor advised. This is shown in figure 4.3 below.
Figure 4.3 – Improved Final Design CAD Isometric View
33. 27
Figure 4.4 – Improved Final Design CAD Section View
Section view in figure 4.4 shows the concept of Tom’s idea, where the filter is being held
by just glass at the sides. Water inlet hole lets running water in to cool and fills up the
rectangular space. As it is filled up, the water is brought out through exactly a mirrored
hole on the opposite side. The water then cools the filter as it gets heated up due to
electromagnetic ray absorption.
On the bottom body, the algae chamber, the channel is shaped slightly curved and
reduced in size by a lot compared to the previous design. This is to ensure that all the
algae run right in the middle lane of the product so that it will be in contact with
incoming UV rays. The curved channel will help reflecting UV lights back into algae thus
increasing the efficiency of the product.
Below, in figure 4.5, you can see a simulated sunlight hitting the product. The size and
shape is carefully designed to absorb maximum sunlight from top to bottom at the focal
length of the Fresnel lens. It also shows how the light cone will hit the algae chamber.
Then, the curved surface will reflect the UV light back into the channel full of algae.
The design was agreed upon and then made its way to the manufacturing process. The
inlet & outlet holes were designed with an NPT threading to be fixed up with standard
ready - made NPT fittings.
Quartz
Glass
UV Filter
Acrylic
34. 28
Figure 4.5 – Figure showing Sunlight into the UV Filter & Algae Chamber
4.4 Manufacturing Materials List
Manufactured Part Material
Top Plate
Mild SteelMain Body
Algae Chamber
UV Filter Holder Acrylic glass (methyl methacrylate) (22)
O-ring Rubber
Table 4.1 – Manufactured Part Material List
The table 4.1 above shows the chosen materials for the parts to be manufactured. The
mild steel was chosen to give an ultimate strength to outer frame parts of the device so
that it keeps the internal parts uniformly intact during use and at all times. It also gives
space for temporary mechanical fasting such as screw which can be dismantled in case of
replacement of internal parts. For the UV filter holder, acrylic glass was chosen instead of
normal glass. Acrylic simply has much higher impact strength than glass. (23) This non-
shattering property makes acrylic the more suitable option. We do not want it to shatter
35. 29
during use and getting the filter disorientated. O-ring always has been made from rubber
for sealing purposes.
4.5 Parts List & Function
4.5.1 Top Plate
Figure 4.6 – Top Plate
The figure 4.6 above shows the part which holds the top quartz glass. It is designed with
an O-ring placement so that it acts as a cushion for Quartz glass thus preventing it from
cracking. The 8 holes around the perimeter are for M 2.5 x 10mm screws, which holds on
to the main body & keeping the top Quartz in place.
4.5.2 Main Body
Figure 4.7 – Main Body
36. 30
The main body of the product is shown on the figure 4.7 above. This also has an O- Ring
designed into it and a depth of cut to allow Quartz placed onto the body. The cut for
Quartz frame is slightly enlarged to allow thermal expansion during use. It is a mirrored
product thus looking exactly the same on the other side for second Quartz glass
placement with an O-ring too. The middle of the main body is empty to allow space for
UV filter and the holder to be held. The inlet & outlet holes are NPT ¼” threaded. The 8
holes on each side of the body are for screw inlet as both the top plate and algae
chamber will be screwed onto this body.
4.5.3 Algae Chamber
Figure 4.8 – Algae Chamber / Bottom plate
The algae chamber shown in figure 4.8 above, as the name says it all, is used to fill up
with algae for UV radiation. It is also known as the bottom plate as it works exactly like
the top plate in terms of keeping the Quartz glass in place. The design shows how similar
it is with the top pate, the 8 screw holes on its perimeter and the O-ring placement
design. The only difference this time will be the screws used, which will be M 2.5 x 20mm.
Inlet & outlet holes are NPT 1/8” threaded. The curved surface was initially planned to be
painted with an Aluminium layer, which is an excellent reflective surface for UV rays,
shown in the CAD picture in figure 4.8. However, due to the surface roughness, the paint
will not affect much and so the idea was discarded.
37. 31
4.5.4 Quartz glass
Figure 4.9 – Quartz glass
Quartz glass, shown in figure 4.9 above, has a main barrier function to prevent algae and
water from mixing together.Also, theQuartz combined with O-ring prevents leaking and
keeps the water running inside the product. A normal glass usually prevents UV ray
penetration thus Quartz glasses are used as a substitute. As the Quartz glasses are
exposed to heat, gaps of air cushion are placed around it to allow for thermal expansion.
It has a coefficient of about 0.6 x 10-6 K-1. (24)
4.5.5 O-ring
These rectangular O-rings have the most basic function, which is to seal and act as a
cushion for the Quartz glass. The cushion prevents crack on the glasses in case of tightly
screwed plates and also water leaking. Figure 4.10 below shows the two types of O-ring
used. The smaller one is specifically for algae chamber plate.
Figure 4.10 – Rectangular O-rings
38. 32
4.5.6 UV Filter
Figure 4.11 – UV Filter
Exactly as the name suggest, a band pass filter which only allows UV range of rays to
pass through and absorbs the rest. It is made of Schott glass and is of black colour as
show in figure 4.11. It has a thermal expansion of about 8 x 10-6 K-1. (25)
4.5.7 UV Filter Holder
Figure 4.12 – UV Filter Holder
The part above in figure 4.12, made up of two exact replicate, is just a medium to hold
the UV filter in place. Its main function is that it enables a thermal balance on the filter
because water can now run on top as well as bottom surface of the filter. The UV filter’s
sides are placed with great dimensional accuracy onto this part so that the filter does not
fall when the it is cooled down or cracks when it expands due to heat.
39. 33
4.5.8 NPT Fittings
Figure 4.13 – NPT Fittings
Figure 4.13 above shows the brass NPT fittings, 2 of each size that is ¼” and 1/8” for each
inlet and outlet holes. The other end is a barb hose for ease tube fitting. For the algae,
the barb hose selected was the same size of 1/8” whereas for the water, the barb hose
selected to be 3/8”, the usual standard water hose size.
4.6 Full Assembly
Figure 4.14 – Full Assembly
The figure 4.14 above shows the final product. You can see the final patches around the
product where thread seal tapes were used with the NPT fittings to decrease chances of
leak. The picture also shows some bits of an aquarium silicone sealant. It is placed to fix
the water sealing property of the device as the O-rings used were not efficient due to its
small sized design flaw. An aquarium quality silicone sealant used to ensure no algae-
harming chemicals present.
Thread Seal
Tape Silicone Sealant
40. 34
4.7 Heat Load Calculation
From the graph in figure 4.15, an assumption can be made that Sheffieldreceives sun
energy with highest peakofabout 900 W/m2 in a day.(26) (27)
Figure 4.15 – Statistics of Solar Irradiation in Sheffield
If assumed that 100% of this energy is absorbed by the UV filter, then
Absorption Power, P = Irradiance, TSI X Area of Fresnel Lens, A
= 900 X 0.283 [Equation 4.1]
= 255 W
This absorbed power is assumed to be fully transferred out into the cool running water.
Thus the specific flow rate is needed to calculate and justify the design.
Water flow rate, Q = Inlet-Pipe Cross Section, A X Water Velocity, v (28)
= 1.91 x 10-5 X 0.5 [Equation 4.2]
= 9.55 x 10-6 m3s-1 @ 10 ml / s
Therefore, the increase in water temperature to cool down is
Raise in temperature, ΔT= P / (Q x Density, ρ x Water Heat Capacity, Cp)
= 255 / (9.55 x 10-6 X 1000 X 4200) [Equation 4.3]
= 6.36oC
Hence, the design has been justified since the change in temperature of water is
relatively small. The device then will be fully functional in summer & hot weathers even
with the minimum average tap water speed to cool it down. (29)
41. 35
5 DEVICE TESTING
5.1 Laboratory Experiment Method
Experiment was set up as shown in figure 4.16 below. The tap water flow was measured
and adjusted to about 10 ml/s. 4ml of algae solution was pumped into the algae chamber
and circulated using an algae pump. UV light source was switched on for 1 minute.
At the end of 1 minute, the 4ml algae solution was taken out and analysed using
Haemocytometer procedures to collect data. Experiment then repeated for 3, 5, 10 & 20
minutes UV light source duration. Readings were also taken from non–UV radiated algae
solution as a control specimen.
Figure 4.16 – Experiment Set Up
100µl from each of these 4ml specimens were mixed with 100µl of 0.4% Trypan Blue in
NaCl. This Trypan Blue stains increases visibility when seen under microscope using
Haemocytometer. 10µl of this mixed solution were put into the Haemocytometer as
shown in figure 4.17 below. Under a microscope, the Haemocytometer provides grid to
manually count live and dead cells in an area. These data are then combined from
different square grids to get an average reading. The data can then be tabulated and
produced into a scattered graph.
Water & Algae
(Parallel)
IN
OUT
Algae PumpUV Light
Source
Designed
Device
42. 36
Figure 4.17 – Haemocytometer with 10µl of Specimen & Trypan blue solution
5.2 Results & Analysis
Figure 4.18 – Graph of Cell Viability against Duration of UV Radiation
The graph in figure 4.18 shows a scattered plot of the cell viability against duration of UV
radiation on algae cells. The scattered plots somehow hover around a value with some
range. This is due to the uncertainty of the measurement from Haemocytometer. Using
statistics, the uncertainty in the graph can be analysed by plotting mean value with error
bars. This is done and shown in the next figure, 4.19 below.
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25
CellViablity(%)
Duration of UV Radiation (min)
Cell Viability Vs. Duration of UV Radiation
First Reading
Second Reading
43. 37
Figure 4.19 – Graph of Cell Viability Mean with Error Bars
5.3 Discussions
Viewing figure 4.18, the data points generally agrees with theoretical relation between
cell viability and the duration of UV radiation given to those specimens except for the
data point on 5 minute, which is slightly off the trend. The results still show a good
repeatability between tests, supported strongly by error bars in figure 4.19 despite the
high chance of uncertainty due to human error.
Increasing UV dose time effectively kills the surviving algae cells, thus reducing its cell
viability. This proves that the device successfully delivers UV rays onto algae. However,
the patterns at 10 to 20 minutes trend a limiting factor occurrence at about 30% cell
viability. The best explanation is that layers of algae cells are getting shaded due to the
deep channel in algae chamber. So, a much narrower gap needed in the future to
eliminate shading effects.
This device was tested till UV dose duration of 20 minutes, the maximum duration
intended to work under the Sun. At the end of every test, the UV filter was constantly
analysed. There was no sign of crack or any other deformations on the filter. So, this
0
20
40
60
80
100
120
0 5 10 15 20 25
CellViablity(%)
Duration of UV Radiation (min)
Cell Viability Vs. Duration of UV Radiation
Cell Viability Mean with Error Bars
44. 38
proves that the device is safe to work for given period of time as long as water is kept
running to cool the UV filter.
6 FUTURE WORK
This investigation has shown a great potential to use Sun’s energy source for biofuel
production, one is through solar energy conversion to power the tracker. However, this
has not been confirmed and only has been theoretically computed in this thesis. So, it
needs a validated reliable data to be proven with some sort of tests. A direct energy
measure data from the tracker would help to do so.
As for thedesigned device, it reduces cell viability effectivelybut seems to have a limiting
factor at about 30% cell viability. The deep channel in algae chamber might provide
shading to lower layers of algae cells. So, the algae chamber design needs to be
improved with a much narrower gap to be effectively radiated by UV rays uniformly
throughout the algae flow.
Also, the designed device proves to keep the UV filter cooled during its operation. But,
this has only been proven in laboratory standard so far. The question still remains on the
real outdoor scenario, whether the device will show the same performance with Sun’s
radiationlevel. This has to be tested and confirmed. Furthermore, the heat carried out by
the cooling water can be of some use such as regulating temperature on algae culture for
optimum or other heat cycles.
45. 39
7 CONCLUSION
Based on the findings of this project research, there is a great potential in solar energy,
which can be thoroughly exploited to reduce energy cost in biofuel production through
algae medium. Solar panels introduced to the tracker will help to do so. However, this
will only stand justified with a much more accurate data than the ones produced in this
thesis. Therefore, the daily energy consumption data has to be measured directly from
the solar tracker. This was the idea totally lacking in this investigation as the produced
data has been always computed from incomplete data.
Investigation also showed how the designed product helped to deliver the UV radiation
onto algae while keeping the UV filter safe. It was a clear evident from figure 4.18 & 4.19
that the device works pretty well. After the tests, the UV filter did not have any sign of
deformation or cracks. In conclusion, the designed device works at delivering its job but
only to an extent as there seems to be a limiting factor at about 30% cell viability when it
performs for longer durations and might require a much narrower channel design for the
algae chamber.
46. 40
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APPENDICES
Appendix A – Top Plate Dimensions
