Controller for Solar Generation - University of Strathclyde Project Report

Group 3: Controller for Solar Generation
Donald Bryson
Thomas Gibson
Benjamin McIntosh-Michaelis
Adam Stewart
Electrical and Mechanical Engineering
2013 - 2014
EM304
Integrated Design

EM304 Integrated Design Group 3: Controller for Solar Generation 2013/2014
University of Strathclyde
1
Abstract
This report contains detailed information on a student project undertaken at The University of
Strathclyde as part of 3rd
Year Electrical and Mechanical Engineering course EM304: Integrated
Design.
The project had the aim of designing and building a controller for solar generation, implementing a
device to track the position of the sun in the sky at the same time as heating a volume of water for a
practical application.
The project was run between October 2013 and May 2014 and was designed to test and develop the
group’s management and team working skills as well as emphasising investigative, design and
implementation abilities.
Statement of Academic Honesty
This submission is entirely the original work of the group.
Except where fully referenced direct quotations have been included, no aspect of this submission
has been copied from any other source.
All other works cited in this submission have been appropriately referenced.
Any act of Academic Dishonesty such as plagiarism or collusion may result in the non-award of the
degree.
The copyright for the material in this report belongs to those named on the cover page.

2
Contents
Abstract ................................................................................................................................................ 0
1. Introduction.................................................................................................................................. 4
2. Background................................................................................................................................... 4
3. Specification.................................................................................................................................. 5
4. Roles and Participation ................................................................................................................. 6
5. Mechanical Design and Function .................................................................................................. 7
5.1. Objective............................................................................................................................... 7
5.2. Design ................................................................................................................................... 8
5.2.1. Concentrator................................................................................................................. 8
5.2.2. Azimuth......................................................................................................................... 8
5.2.3. Elevation ....................................................................................................................... 9
5.3. Results/Demonstration of Success...................................................................................... 12
5.4. Scaling................................................................................................................................. 12
5.5. Conclusion........................................................................................................................... 13
6. Electrical Design and Function .................................................................................................... 14
6.1. Objective............................................................................................................................. 14
6.2. Design ................................................................................................................................. 14
6.2.1. Initial Concept ............................................................................................................. 14
6.2.2. Final Concept............................................................................................................... 14
6.2.3. Additional Functionality .............................................................................................. 16
6.3. Scaling................................................................................................................................. 17
6.4. Conclusion........................................................................................................................... 17
7. Water Heating System ................................................................................................................ 18
7.1. Objective............................................................................................................................. 18
7.2. Design ................................................................................................................................. 18
7.2.1. Heating Element.......................................................................................................... 18
7.2.2. Tank System ................................................................................................................ 20
7.2.3. Linking the Tank and Heating Element............................ Error! Bookmark not defined.
7.3. Results/Demonstration of Success...................................................................................... 21
7.4. Scaling................................................................................................................................. 22
7.5. Conclusion........................................................................................................................... 22
8. Procurement............................................................................................................................... 23
9. Improvements............................................................................................................................. 25

3
10. Conclusion............................................................................................................................... 26
11. Appendix 1: Fully Integrated Testing....................................................................................... 27
11.1. Objective......................................................................................................................... 27
11.2. Procedure........................................................................................................................ 27
11.3. Results............................................................................................................................. 28
11.4. Conclusion....................................................................................................................... 30
12. References .............................................................................................................................. 31

4
1. Introduction
Reliable water heating is important both domestically and in industry and since water heating takes
significant energy input, hot water supply is a major issue surrounding global energy supply.
Group 3 was made up of four students; Adam Stewart, Thomas Gibson, Donald Bryson and Benjamin
McIntosh-Michaelis. They were tasked with building a Controller for Solar Generation which would
track the movements of the sun and use its infrared radiation to heat water in the interest of killing
legionella bacteria. The timespan of the project was between October 2013 and May 2014 and had
to be completed within a budget of £100. The group’s primary advisor and ’customer’ who created
the initial specification was Dr Bruce Stephen and the secondary advisor was Dr Brian Stimpson, both
from the University’s Department of Electronic & Electrical Engineering.
2. Background
The aim of this project is to use solar power to control Legionnaires Disease in water systems. First
discovered in 1976 when 182 US Army Legionnaires contracted the disease which was fatal in 29
cases, it is spread most commonly by the Legionella Pneumophilia bacterium and results in a
pneumonia-like illness. This bacteria accounts for 90% of cases of Legionnaires Disease and has only
ever been discovered in water where it thrives in temperatures between 20 and 45 degrees Celsius.
It can only be contracted by consumption of infected water or inhalation of water droplets
suspended in the air which are contaminated with the bacteria. Common situations for the bacteria
to thrive are in hot water tanks and evaporative condensers used in large air conditioning systems
seen in hotels and office buildings. As well as an appropriate temperature, legionella also thrives
where substances such as rust, sludge or other organic matters are present. Temperatures around
60 degrees Celsius and over will kill the bacteria over time with higher temperatures taking less time
to kill the bacteria.
Solar energy systems in the United Kingdom have taken a slight hit in recent years due to the
downscaling of the feed in tariff offered to contributors in late 2011, but with the reducing cost of
Photovoltaic (PV) panels, solar energy systems are on the rise again. Solar power was in use in over
450,000 UK homes at the end of 2013 with around 2,000 additional installations each week. With
around 1 kW/m2
of thermal power available on a sunny day in the UK, the potential for solar energy
systems is still high. Solar water heating systems are less common in the UK than their Photovoltaic
counterparts but also have their place. They can be used to offset the temperature difference
central heating systems experience on start-up and can save significant amounts of electricity over
the course of a year.

5
3. Specification
At the start of the project the group was given the task to build a controller for solar generation with
the following objectives:
 Must follow the sun in both the azimuth and elevation paths during daylight hours
 Will be land based
 Will operate in the UK
 Will ignore the effect of clouds
 Will operate under its own power
 Will produce 250L of water at 60°C in a week
Given the above requirements, the group agreed that a
full scale working system would be unfeasible given the
time and budget restraints. It was decided instead to
create a ¼ scale model and it was calculated that this
would correspond to heating 2.5L of water up to 60°C in
an hour on a bright day. Additionally the group decided
to add in a sleep function to the Arduino
microcontroller so that the entire system could be shut down over night and for short but frequent
periods throughout the day. This decision was taken to reduce the overall power consumption of the
project.
The general idea of the solar concentrator would be to reflect sunlight using a parabolic reflector
which would rotate and tilt in order to track the sun and keep the focused sunlight on a heating
element. Water would be cycled between a tank and the heating element in order to heat up the
whole volume of the tank.
From the outset it was obvious that accurately tracking the position of the sun throughout the day as
well as efficiently transferring heat energy from a heating element to a tank full of water would
prove the biggest difficulties that would have to be overcome.
Figure 3.2 System Design Block Diagram
Figure 3.1 Azimuth, Elevation and Zenith Angles

6
4. Roles and Participation
At the beginning of the project all group members put forward the parts of the project they would
be most interested in working on and those roles have not changed once they were initially agreed
upon. Participation has been evenly spread between the four team members who have been kept in
close contact throughout the academic year and have worked well together as a group, with only
one person working on the project at a time being a rare occurrence.
Adam put himself forward for team leader which was unanimously accepted, in first semester he
organised the weekly group meetings where the group discussed the specification of the project and
how the problems could be solved. The group also discussed resources and where some of the major
components required could be procured. In second semester Adam also took on the role of resource
representative which involved placing all the orders with the electrical workshop. It also involved
submitting work to be done by the mechanical workshop and ensuring it was being completed as
desired by the group to fit in with the rest of the components. The linear actuator which was
produced by the mechanical workshop required a lot of discussions with the staff at the workshop as
they were often inclined to use different materials and were occasionally unsure of the designs.
Adam also helped out with some of the early stages of writing the code required to calculate the
position of the sun but primarily with the integration of the different components to deliver the final
solution.
Tom has performed the role of technical director and has been instrumental in the design and
implementation of the base concept of the project and particularly in the movement sub system. He
has devised the concepts used for many different areas of the project and has played a major part in
the assembly of all the components. Tom has also kept track of the budget throughout the project
and was able to procure the three of the potentially most expensive components in the project, the
satellite dish, Arduino microcontroller and battery, for free which has had a key impact on the
budget.
Donald has worked on the electronic side of the project, writing the code for the motor controller to
drive the pump as well as the motors for the azimuth and zenith angles to ensure that the dish is
always pointing at the sun during daylight hours. He has also constructed a real time clock with more
functions which has enabled the Arduino to turn itself off and then wake itself up. This has helped
the project to save a significant amount of power both at night and throughout the day when it is in
its low power state.
Alongside working with the Vertically Integrated Project, Ben has completed the majority of the
work for the water heating system. He procured the tank where the water will be stored and
insulated it as much as possible with the resources available. He also helped in the implementation
of the pumps, tubing and the bending of the copper pipe used for the heating element. Most
valuably, he has consistently helped in the assembly of the project as a whole and has been involved
with design decisions throughout the project.

7
5. Mechanical Design and Function
5.1. Objective
The mechanical design of the solar concentrator is concerned with the physical parts requires to
concentrate the sunlight to a point, as well as move the concentrator to be aligned with the sun,
based on signals from the Arduino.
The system must rotate the concentrator to align it with the azimuth angle as well as tilting the
concentrator to align with the sun’s elevation.
By implementing these systems the concentrator complied to the specification of tracking the sun
throughout the day, and provided a much more efficient system as the sunlight is always in direct
sight of the concentrator.
Figure 5.1 below demonstrates how such a system can improve the effectiveness of a solar
concentrator by controlling the focal point.
Figure 5.1 Comparison between Fixed Concentrator (Top) and Solar Tracker (Bottom) in Azimuth Plane
As can be seen above, with a fixed concentrator the focal point moves across the dish relative to the
sun, whereas with the tracker the focal point remains central to the dish. This is favourable when a
collector or heating element is required as it can then remain in the same position relative to the
dish. A similar situation occurs with the elevation angle.
Sun
Focal Point
Concentrator
AM PM

8
5.2. Design
5.2.1. Concentrator
To focus the sunlight it was decided that a parabolic reflector would be used, as opposed to a lens.
Where a lens may have produced a more intense focal point, it was considered that a reflector
would be easier to mount and control, and would provide a more useful and traceable focal area.
The reflector was made from a recycled satellite television receiver dish, covered with a reflective
thermal blanket bonded to the dish with PVA glue. The blanket was chosen thanks to its high
reflectivity of both visible light and infrared radiation, so that as much solar energy as possible could
be captured. The thermal blanket was applied in narrower strips, giving a smooth and highly
reflective surface. As seen in Figure 5.2 below, the concentrator was tested using lasers to find the
approximate size and position of the focal area.
Figure 5.2 Laser Testing of Solar Concentrator
The dish had dimensions of 720 mm X 560 mm and an area of approximately 0.317 m2
, and since it is
estimated that the sun has a power rating of 1 kW/m2
the concentrator could collect 317 Watts of
thermal power. The dish had a scaling factor of 10, so the reflected light was focused on an area 72
mm wide by 56 mm high.
5.2.2. Azimuth
To rotate the concentrator to the azimuth angle it was mounted on
an MDF turntable, using a mounting pole purchased from Onecall,
thus allowing 360° of revolution. MDF was chosen for this and the
base of the assembly since it was available immediately and free of
charge from the EEE mechanical workshop. To reduce friction and
to balance the turntable, castor wheels were added. The turntable
arrangement can be seen in Figure 5.3.
The original plan was to use a small motor and gearbox mounted
on top of the turntable. A shaft would protrude through the
turntable from the gearbox, and drive a pulley against a large gear
wheel fixed to the base of the assembly, as illustrated in Figure 5.4.
Figure 5.3 Turntable Arrangement

9
It was soon found that this system was not appropriate, since the motors tried were not capable of
producing a high enough torque, nor could the gearbox transfer enough power when bigger motors
were used. It was also very difficult to align the pulley with the fixed gear, especially with the lack of
space between the base and the turntable.
Therefore the azimuth drive system was redesigned to
incorporate a larger and more powerful motor that
could easily provide the torque required. The motor
was mounted to the assembly base and a Meccano
wheel was used to transfer the power from the motor
to the turntable. A series of spur gears were used
between the motor and the wheel to reduce the
motor speed, so that the turntable had a resultant
speed of around 0.6 rpm, allowing precise control of
the turntable.
A potentiometer was mounted to the axle of the turntable, which remained stationary relative to
the turntable. The body of the potentiometer was mounted to the turntable so that it rotated with
the turntable, feeding a signal back to the Arduino so that the azimuth angle could be calculated.
Figure 5.6 Azimuth Potentiometer
5.2.3. Elevation
The control of the elevation angle of the concentrator was one of the more complicated issues
among the mechanical design of the project. An early idea is outlined below, with initial drawings
shown in Figure 5.7 and a card model seen in Figure 5.8.
Turntable
Gear Wheel
Motor/Gearbox
Pulley
Castor Wheel Base
Figure 5.4 Original Turntable Design
Figure 5.5 Motor, Gearing and Drive Wheel

10
Figure 5.7 Early Elevation Actuator Drawings
Figure 5.8 Early Elevation Actuator Design
A threaded rod would be placed within the base component, running through a threaded hole in the
strut. As the threaded rod would turn, the base of the strut would travel along the base, in turn
raising or lowering the stand. While this method may have been successful for the project, it was
decided against since it was likely to be a bulky approach and possibly unstable. It would have also
been difficult to attach such a device to the concentrator dish.
Several other approaches were also considered, including using a chain connected between the top
and the base of the dish driven by a motor positioned at the back of the turntable, but it was finally
decided that a linear actuator would be the best approach. The preferred suppliers were searched
for such devices, but it was impossible to find an appropriate device within budget so designs were
drawn up and submitted to the EEE workshop to have an actuator made, as seen in Figure 5.9.
Stand
Strut
Base

11
Shaft
Carriage
Threaded
Rod
This design also used a spinning threaded rod as the basis of the actuator. The carriage part has a
threaded hole through the centre so that as the rod is turned the carriage moves along its length. A
shaft connects between the carriage and the dish so that as the carriage moves the base of the dish
is pushed up and out, or is drawn back in. A potentiometer is used as the axle between the carriage
and the shaft, sending a signal to the Arduino relating to the elevation angle of the dish.
The threaded rod was turned using a motor, with a built in gearbox with 100:1 ratio. It was found
that this motor provided an adequate speed for the actuator, so a 1:1 gear ratio was used to connect
between the motor and the threaded rod. To save time and money, the gears for this part of the
project were laser cut using the equipment in the DMEM department, after the appropriate part
files were downloaded from the Rush Gears Website.
Figure 5.10 Linear Actuator (Left) and Gearing (Right)
Figure 5.9 Linear Actuator Design

12
5.3. Results/Demonstration of Success
Through the implementation of these methods, if was found that both operated very successfully.
The azimuth motor provided enough power to drive the turntable with relative ease, even under
reasonably heavy loading. The range of the turntable was limited to between 30° to 270° from
north, due to the limited range of the axial potentiometer used to measure azimuth angle and the
bolts that secure the linear actuator ends to the turntable since they protrude through the turntable
directly in the path of the drive wheel. To improve this part of the system these bolts may be
countersunk, and a potentiometer with a greater range may be used. An issue also arose with the
first potentiometer used, as the shaft was very stiff to turn there was a tendency for the
potentiometer shaft to shear. To combat this a different potentiometer was used which rotated
much more easily, reducing the shear stress applied to the shaft.
The linear actuator also provided the ideal system for tilting the concentrator dish and proved highly
successful. There were concerns whether the device would function effectively without the use of
bearings in the carriage and end supports, omitted in the interest of saving costs. However it was
found that with appropriate lubrication the effects of friction were minimal. The linear actuator was
designed to have a length of 50 cm, allowing for the full range of elevation of the solar concentrator
(0° – 57°), however to focus the sunlight onto the desired focal point the concentrator had to be
lowered by 25° from the elevation of the sun. Therefore the actuator could have been made
shorter, saving some space and weight on the turntable.
5.4. Scaling
This project was concerned with constructing a ¼ scale model in terms of area of the concentrator
dish, i.e. the full scale model would have a dish of around 1.4 m wide by 1.1 m tall. Of course, by this
scaling factor the mass of the concentrator would be greater, so the actuation methods described
above would have to be larger and stronger. Also the full scale system would ideally have a specially
made parabolic reflector with a much smoother surface than the reflector built in this project,
providing a higher reflectivity and efficiency.
The turntable and base would be constructed from a much more durable material such as steel,
aluminium or composite to increase their resistances to weathering, since MDF cannot withstand
water. More suitable castors or bearings would be used between the turntable and the base to
further reduce friction and add support. A skirt may be added around the turntable to prevent
anything from entering the space and blocking the castors. A rack and pinion system may replace
the drive wheel so that the dish cannot move under external influences such as wind.
As well as an increase in size the linear actuator would make use of bearings between all the moving
parts to reduce friction and the effects of wearing. The threaded rod may be enclosed to keep it
clean and to ensure that wires cannot get caught, as well as increasing the safety of the system. If
enclosed the lower part of the actuator could be oil filled to avoid dirtiness and wearing in the
threaded parts. Otherwise weathering may present a significant risk and cause the system to seize.
A professionally made linear actuator could be used but these can come at a much greater cost.
The gearing in each system would also be replaced with metal gears enclosed in oil filled gearboxes.
The motors required would also need to be increased in size, as will the systems for powering these
motors.

13
5.5. Conclusion
The mechanical aspect of this project was concerned with concentrating the sunlight to a point so
that it could be put to good use, as well as tracking the sun so that as much solar energy could be
captured as possible with high efficiency.
To implement these movement techniques several designs were considered before the turntable
and linear actuator were chosen, and after assessment it can be concluded that these were the best
approaches to take, yielding great results with high positional control and minimal mechanical
losses.
Figure 5.11 Rear View of Final Solar Concentrator Design Showing the main Mechanical Components

14
6. Electrical Design and Function
6.1. Objective
The electrical system is required to supply power to all the relevant mechanical parts such as the
motors and pump, as well as the Arduino microcontroller. It also concerns the implementation of
solar panels to allow the project to operate under its own power. The electronic side of the project is
necessary to use inputs such as time and geographical position, then use algorithms to calculate
where the sun is in the sky, then send appropriate signals to the motors to ensure the orientation of
the dish is optimal for solar water heating. The Arduino Uno was used for the microcontroller as it
was cheap and has an excellent online community which would aid in the writing of code as there
were many examples which could be adapted for the required uses. The system was supplied power
from a 1.3Ah lead acid battery as this was readily available and an adequate size for the purposes of
the system.
6.2. Design
6.2.1. Initial Concept
The original concept for performing this function was to track the sun with a set of light sensors on
either side of the dish in order to produce an accurate real time position of the sun. However it was
reasoned that this was not practical due to the inherent complexities this would introduce.
6.2.2. Final Concept
The final concept tracked the sun the using equations which are very accurate and reliable for many
years. The calculated position of the sun would then be compared with the orientation of the dish. A
few sources were initially used to calculate the position of the sun but they proved inconsistent. In
the end the equations from EEE class EE317: Renewable Energy Technologies were used as these
proved to give results which were consistently accurate. The equations used were as follows:
( )
[1]
[2]
( ) [3]
[4]
[5]
(( ) ( )) [6]
(
( ) ( )
) [7]
Table 6.1 below shows the symbols and what they represent in these equations.

15
Table 6.1 Position of the Sun Equation Symbols and Meanings
Symbol Meaning
B Placeholder for use in EoT calculation
EoT Equation of Time
δ Declination Angle
Ts Solar Time
λzone Longitude
ω Hour Angle
φ Latitude
α Elevation Angle of the Sun
θ Azimuth Angle of the Sun
When these equations were implemented on the Arduino microcontroller it was found that it
provided wildly inaccurate results, although the equations had been checked using Microsoft Excel.
It was later discovered that the Arduino does not have sufficient arithmetical capabilities to perform
complex equations in one go. They therefore had to be split up into smaller calculations with lots of
intermediate variables introduced to cope with this.
From testing it was found that if the concentrator lined up exactly with the sun then the focal point
would be much higher than the heating element mounted on the dish. Through trial and error the
elevation angle of the dish was lined up with the actual elevation of the sun minus 25 degrees to
focus the sunlight onto the heating element by making changes to the code. To save power the
Arduino would only move the dish West when the azimuth angle of the dish was less than that of
the sun, and would then move to 5 degrees past the actual azimuth angle of the sun. As the heating
element was longer than necessary, this kept the focused light on the heating element at all times
and required the dish to be moved less often. The concentrator would only be moved East if the
azimuth angle of the concentrator exceeded that of the sun by 10 degrees. The elevation angle
would be kept within -25 and -30 degrees of the elevation angle of the sun.
Due to the placement of the potentiometer measuring the angle of the elevation of the dish, the
relationship between the resistance of the potentiometer and the elevation angle of the dish was
non-linear. To resolve this issue, the resistance of the potentiometer was mapped to the
corresponding elevation angle of the dish and stored as a 2D array in the Arduino code. The table
entries give the resistance of the potentiometer at set elevation angles 5° apart. When the elevation
angle is read into the code, the resistance of the potentiometer is compared to the lookup table and
the elevation angle is determined from there. The resistance of the potentiometer is set to the lower
value of the two values it is in-between in the table and the corresponding elevation angle is used.
The time is read into the microcontroller from a Real Time Clock (RTC) which accurately keeps the
time to the second. The RTC originally used was a Maxim DS1302 Real Time Clock which was
purchased on a PCB with a coin battery and relevant resistors. Code to enable the Arduino and the
RTC to communicate was required and downloaded from the GitHub website [vii]. An L293D motor
controller chip was used to drive the motors due to its availability and cost, however as the pump
was sourced after the motors and controller and had a high power demand it was not suitable to be
run directly from the motor controller.

16
When the motors were required to move, a signal was sent to the relevant channel of one of the
motor controller chips. One side of the motor controller chip was used to drive the azimuth motor
and the other side of the chip used to drive the elevation motor. Once movement operations were
complete a signal was sent to another motor controller which switched a relay used to provide
power to the pump. This pumped water around the water heating system for a minute before the
system entered a low power state which is explained in detail in part 6.2.3.
6.2.3. Additional Functionality
Due to the high power consumption of the pump and the relatively high power consumption of the
Arduino, it was necessary to take measures in order to save power. To combat the issue 2 solar
panels were used to trickle charge the battery, however it was also necessary to put the Arduino into
a low power sleep state while inactive. This would result in the system cycling through operations in
the following way: wake up, move if necessary, pump for a minute and then go back to sleep. Table
6.2 shows the power consumption and duration of each stage in operation.
Table 6.2 Power Consumption of System During an Average Day
Power In (W) Power Out (W) Typical Usage per Day
Arduino (Sleep) - 1.2 21 Hours 29 Minutes
Pump - 24 2 Hours 11 Minutes
Azimuth Motor - 9.6 10 Minutes
Elevation Motor - 4.08 10 Minutes
Solar Panels 8 - 13 Hours
As Table 6.2 shows, the pump is very high powered compared to the other components and on for a
considerable duration of time. Even with 2 solar panels the system still makes a net power loss.
Although the motors are also reasonably high powered they have a very low duty cycle and as a
result the whole system, without the pump, could run off of a single solar panel. By comparing the
net power while the pump is on and while the Arduino is asleep the ratio of time for which the
system is in the two states can be determined. The net power gain while the system is asleep is 6.8W
and the net power loss of the system while the pump is on is 16W. This means that the system
should sleep around 2.5 times longer than the pump is on in order to not lose power over the course
of a day.
For the Arduino to wake up from its low power state it needs to receive a signal to tell it to do so. For
these purposes a new Real Time Clock with a built in alarm function needed to be implemented
instead of the old DS1302 RTC. The new RTC used to fulfil this function was the Maxim DS1306 RTC
chip. The DS1306 chip was set up as shown in Figure 6.1 without the pull up resistor from the 1 Hz
signal output. A 3V coin battery was used to power the RTC and a 10kΩ resistor pulled pin 5 of the
RTC to +5V which was supplied by the Arduino’s voltage regulator. A 32.768 kHz crystal with a 6pF
capacitance was connected to pins 3 and 4 of the RTC as was specified by the chip’s datasheet.

17
Figure 6.1 Circuit Diagram of Real Time Clock
New code had to be written to allow the Arduino and the RTC to communicate with each other. This
included changing the registers used to read and write to the RTC and adding new functions to set
the Alarms on the RTC. Once the sun sets, the alarm for sunrise the next day is set and the system
goes into its low power state for the night.
6.3. Scaling
Scaling the system up would not affect the electrical control system much, however the accuracies
and tolerances of the system may have to be fine-tuned to be consistent with the new geometry of
the mechanical system. The power required by the motors and the pump would also be affected and
would likely require the implementation of motor controllers which are able to provide a higher
current.
6.4. Conclusion
The electrical and electronic system was required to accurately calculate the position of the sun and
send signals to the motor controllers to match the calculated position of the sun with the orientation
of the concentrator within a given tolerance. The control system successfully allowed the
concentrator to be accurately aligned with the sun to produce a focal area on the heating element.
The system made a net power loss on the day of testing the group managed to undertake however,
with a smaller pump that required less power and solar panels that provide more power, this could
be overcome, especially with the recent implementation of the sleep function to the Arduino. A
larger battery could also be used to reduce this problem.

18
7. Water Heating System
7.1. Objective
The water heating system needs to absorb the heat at the focal point of the concentrator and
transfer the energy to water, raising the temperature. This is done so as to heat 2.5 L of water per
hour from around 20 °C to 60 °C or slightly above during daylight hours with suitable light levels. The
full 2.5 L must be at 60 °C by the end of the hour.
7.2.Design
Two basic concepts were initially considered. Holding a vessel with the full 2.5 L in the focal point
and heating the full body at once. The other; heating up a small volume of water, flushing and
refilling the vessel with appropriate timing.
It was decided that a small volume would be heated and flushed. This decision was made because,
whilst 2.5 L was a feasible vessel size at the focal point, 250 L for a full scale system was not. Also
since the overall system design, would, in theory be used as a hot water supply system for a house
or something with similar hot water requirements, the means of taking water away from the system
needed to be considered. This was done by the flushing concept since it could be tapped; whereas a
tank at the focal point of the reflector would be much harder to tap.
The selected concept had three aspects required to be designed. The water needed to be held in a
heating element whilst being heated, it would then need to be held in a tank system which insulated
the water. The tank and heating element needed to be linked in such a way that the turntable could
still turn within the required range.
7.2.1. Heating Element
The basic functionality of the heating element is shown in Figure 7.1 where Q is the heat transferred
to the water.
Figure 7.1 Basic Functionality of the Heating Element

19
As shown in Figure 7.1 the focused light would be incident with and absorbed by the external
surface of the heating element. The energy would then be conducted through to the internal surface
where it was then transferred to the fluid.
This meant that the heating element needed to be as close to a black body to thermal radiation as
practically possible, and highly conductive. This would ensure that the maximum heat energy was
absorbed by the heating element’s external surface and was then transferred efficiently to the
interface with the fluid. According to the laws of heat transfer, both of these abilities are described
by the coefficients absorptivity, α and thermal conductivity, k.
Research found that common materials used for heating elements in solar water heating systems
are made from copper; α = 0.4 – 0.65 W/m K2
, k = 401 W/m K and Aluminium; α = 0.4 – 0.65 W/m K2
,
k = 205 W/m K [ii][vi]. Materials such as concrete have a much higher absorptivity but a drastically
lower thermal conductivity therefore copper and aluminium were the most appropriate choices due
to their fairly high values for these coefficients. Copper was the preferred material and was used for
the heating element.
Once the radiation had been absorbed by the external surface of the heating element, and the heat
had been transferred to the internal surface, the energy needed to be transferred to the fluid. This
could be done by forced or natural convection. Forced convection was chosen because it is a more
effective method of heat transfer, capable of transferring around ten times as much energy than
natural convection.
During heating, water needed to constantly flow through the heating element for forced convection.
Therefore the heating element was made from small diameter pipe, making the pipe relatively
simple to bend into a coil which meant that the water spent more time in the focal point. The
heating element covers the full 32 cm2
sized area that the radiation was focused onto.
A recycled copper coolant pipe was sourced from an old fridge and bent into a coil. It was sprayed
with matte black wood stove paint to enhance absorption and mounted at the focal point. The
mounted heating element is shown in Figure 7.2.
Figure 7.2 Mounted Heating Element

20
7.2.2. Tank System
Two options were considered when deciding where the water in the heating element comes from
and goes to. One option was to use two tanks. One containing colder water and the other, very well
insulated, would contain the heated water. This option presents many problems, if water below 60°C
leaves the heating element, the temperature in the second tank will reduce. Also one cycle through
the heating element is unlikely to be enough to heat the water to above 60°C on a reliable basis. As
the second tank would constantly lose a small amount of heat, the temperature would likely drop to
below 60°C.
The second option was to pump water through the heating element at a constant rate using one
well insulated tank as the source and destination of the water. This meant that the only control
needed was that which turns the pump on and off. This meant that initially the water was gradually
heated up by continually passing through the heating element and remixing. Once the tank was at
60 °C or above, it could be maintained at this temperature by continually passing water through the
heating element.
The tank needed to have the capacity of 2.5 L or slightly above, therefore a 3 L plastic bottle was
sourced for free. There were concerns that this would not have been able to hold its shape at 60°C,
although through experimentation it was found that the plastic bottle used held its shape up to
80°C, and no change was observed at 60°C. For insulation this bottle was covered in the same
thermally reflective material as the satellite dish, before it was Papier Mache’d for rigidity and
covered in foam to insulate. This is shown in Figure 7.3.
Figure 7.3 Insulating the Water Tank

21
The heating element was mounted on the satellite dish, which was mounted on the turntable. The
tank was placed off the turntable resulting in relative movement between the tank and heating
element. A suitable way of connecting these two elements was with flexible hosing which was
sourced by the group and had inner diameter 5 mm and outer diameter 8mm.
7.3. Results/Demonstration of Success
The system was tested at the Duke Street car park on Friday 18th
April 2014 (see Appendix 1 for
more detail).
During testing the water was pumped from the tank and through the heating element, absorbing
heat before returning to the tank. This was continued for four hours but was interrupted due to the
power issues regarding the water pump. It could be observed that the heating element was
appropriately located in the focal point, as shown in Figure 7.4. The surface of the heating element
reached very high temperatures, with a peak of 201°C.
Figure 7.4 Radiation Focused onto the Heating Element
During the first period of testing the tank temperature was raised through 8°C from 24°C to 32°C in
around 20 minutes, demonstrating that the system could heat water. After over an hour with the
reflector covered, the temperature of the water in the tank dropped by 1°C, demonstrating that the
tank was well insulated. After a second period of testing the water in the tank reached 42°C,
however this period was also cut short due to the pump running the battery down to the point
where it could no longer operate.

22
7.4. Scaling
A full scale system would see 250 L of water heated to 60 °C by the end of one week. The energy
required to heat 1 kg ( ) or 1 L of water from 20°C to 60°C was calculated as shown below.
[8]
250 l in one week relates to 35.7 l per day. An average day has approximately 8 hours of sunlight and
of these 8, 4 are assumed to be suitable for effective water heating, though this will vary throughout
the year. Therefore there should be 9 l heated every hour, equating to 2.48 ml heated per second, or
2.48 x 10-3
kg/s. Hence a power of 415 W is required for a full scale system.
Assuming 35 % efficiency of the system, the thermal power required would be 1185 W. The
irradiance of the sunlight is 1 kW/m2
in the UK on a bright day, so the area required for the full scale
system would be around 1.2 m2
. The area of the parabolic dish used was 0.32 m2
, relating to a ¼
scale model. The scaled system could heat 62.5 l of water per week, meaning about 10 l per day or
2.5 l per hour.
7.5. Conclusion
The heating system was successful in heating and storing water. The heating element absorbed
energy at the focal point and then passed it into the water flowing through the element. The
connecting pipes directed the water to and from the heating element. Insulation on the tank was
sufficient to prevent a great temperature drop.
A few improvements could be made, such as adding a coil inside the tank to implement a closed loop
system or insulating the connecting pipes to reduce heat loss as described in section 9. An
additional reflector positioned at the focal point at the back side of the coil would capture reflected
radiation which misses the coil as well as the radiation being emitted by the coil. This secondary
reflector could also be shaped to shield the coil from the wind.

23
8. Procurement
This project required a large range of parts, materials and equipment to be sourced on a limited
budget, so as much of this as possible was acquired for free or borrowed. Table 8.1 below indicates
the parts that have been used and where they were sourced:
Table 8.1 Items Procured for Project
Qty Item Description Supplier Part
Number
Cost Each
(£)
Total Cost
(£)
1 Arduino Uno RS 715-4081 18.00 18.00
1 32mm Dia. 6-15Vdc Motor 100:1 Gearbox
(Elevation)
RS 420-596
15.67 15.67
1* 12 Teeth Timing Belt Pulley 15mm width RS 184-594 5.44 5.44
2 Panasonic 3V CR2032 Coin Battery RS 513-2871 1.16 2.32
1 DS1306 RTC Alarm RS 540-2710 4.00 4.00
1* Motor and Gearbox (Kit Form) Rapid 37-1210 5.62 5.62
2 32.768kHz 6pF 2x6mm Radial Cylindrical
Watch Crystal
Rapid 90-3042
0.35 0.70
5 L293D Motor Driver Rapid 82-0192 3.73 18.65
2 L7812cv +12v 1a Voltage Regulator (st) Rapid 47-3292 0.42 0.83
1 4W Solar Briefcase Maplin N05HN 19.99 19.99
1 Loft Mounting Kit 18" Onecall AP02343 4.46 4.46
2 1.75" V Bolt and Nuts Onecall AP02245 0.32 0.65
2 1k potentiometers EEE 1KP 0.49 0.98
1 Linear Actuator Workshop - - -
1 Turntable and Base Workshop - - -
3 Elevation Gears DMEM - - -
5 Azimuth gears/wheel Previous - - -
1* Timing Belt and Gear (Original Azimuth) Previous - - -
1 Satellite Dish Donated [1] - - -
1 Aluminium Foil Tape Donated [2] - - -
1 MFA 919D Motor (Azimuth) Borrowed [2] - - -
1 Small Protoboard Borrowed [2] - - -
1 Large Protoboard Group - - -
1 12V Relay Group - - -
1 12V 1.3Ah Battery Group - - -
1 Water Pump Group - - -
1 Length of Flexible pipe Group - - -
1 Copper Pipe Group - - -
1 Water Tank Group - - -
1 Thermal Insulation Group - - -
1 Thermal Blanket Group - - -
1 PVA Glue Group - - -
3 Insulation Tape (Black, Red, Blue) Group - - -
Total: £97.31

24
 Various small components (nuts, bolts etc.) were found within the lab or sourced from
previous projects.
 Items marked * were not used in the final project.
 Items marked as “Previous” were reused from previous projects.
 Items marked “Group” were sourced separately by or borrowed from group members.
 “Workshop” represents the mechanical workshop in the EEE department, University of
Strathclyde.
 “DMEM” represents the Digital Manufacturing Studio within the Design, Manufacturing and
Engineering Management department, University of Strathclyde. With thanks to Mr Duncan
Lindsay.
 [1] With thanks to Miss Carolyn Gethin, Inverness.
 [2] With thanks to Mr John Redgate, University of Strathclyde.

25
9. Improvements
Given more time and resources, there are a few aspects of the project which the group would like to
improve. First and foremost, a small low power pump would replace the one which is currently in
use in the interest of saving power. Additional insulation would also be added to the system,
primarily to reduce heat loss in the tubing from the heating element to the storage tank. A closed
loop water system could also be implemented which would introduce another coil of pipe within the
water tank. The water in the tank would therefore be completely isolated from the heating system
and a thermal fluid would occupy the piping which would be more efficient at transferring heat from
the heating element to the water stored in the tank. A diagram of this can be found below in Figure
8.1.
An additional reflector could be added to the system so that any radiation reflected from the dish
that misses the heating element would be reflected onto the back of the heating element. This
would also reflect heat energy which is radiating off of the hot surface of the coil. More powerful
solar panels would also be used which would be give the project a net power gain on bright days as
well as being able to generate enough power to be sufficient on bright days with clouds. These solar
panels would be mounted on the turntable so that they also track the sun throughout the day. The
group would also like to implement a relay in series with the solar panels so that the Arduino and
motors would only receive power from the battery if the solar panels are generating enough power,
indicating that it is a nice enough day to be able to heat water with the concentrator. The entire
project would also be weatherproofed so that it could withstand heavy rain as well as moderate
wind. At the moment the base and the turntable are made of MDF which would break up if exposed
to water, this would be replaced with a metal such as steel or aluminium. An electronics box would
also be required to house the Arduino and its connections. Heat shrink tape and Tyco™ connectors
could be used on the wires to completely insulate them and the connections to the motors, pump
etc. Friction could also be reduced by adding bearings to the linear actuator and finding more
suitable casters for the turntable to turn on.
Cold Fluid
Hot Fluid
Parabolic Reflector
Heating
Element
Water Tank
Heat Exchanger
Figure 9.1 Proposed Closed Loop Water System

26
The last major thing the group would like to add to this project is temperature monitoring. This
would allow the temperature of the water coming out of the heating element to be checked and the
flow rate of the pump varied depending on this value. A function in the code could also be included
so that the dish could turn away from the sun if the heating element became too hot to the point
where it could cause damage. With these changes made the project could become a permanent, self
sufficient water heating system that would require very little maintenance and could run
autonomously.
10. Conclusion
This project should be seen as a success as the group successfully built a device capable of accurately
tracking the position of the sun during the day and using infrared radiation from the sun to heat
water. Although the temperature defined in the specification was not reached on the single test day
available to the group, it can be assumed that the project would have been capable of doing so
without the multiple disruptions to the test day. With a temperature of 201°C measured at the
heating element, this would prove more than adequate to heat the water to 60°C.
The project was well managed with weekly meetings of 3 hours to work on the project. Although the
majority of hours were put into the project outside this scheduled meet, all four members were
always present during this scheduled time which allowed effective communication between the
team members and gave an opportunity for integration problems to be discussed and a compromise
found. A high number of hours in the last few weeks of the project made a very large contribution
towards the success of this project as it was able to be in a reasonable working state two weeks
early. This allowed for the test day on what was one of very few sunny days in the last month of the
project, without which no meaningful results would have been obtained for the water heating
system. The budget was also kept very well throughout the year but took a steep drop in the last
week where component failure necessitated purchase of replacements.
Contacts were made throughout the university in the Electrical, Mechanical and Design,
Manufacture and Engineering Management departments where many members of academic staff
were of invaluable importance. The process of requesting permission to test the project out with the
university also provided valuable experience in producing a risk assessment, method statement,
obtaining insurance and communicating with members of different organisations.
This project has contributed extremely relevant experience of project work to all four of the group
members including resource and time management. The integration of designs from different
technical specialities has also been a valuable lesson which each of the students will be able to carry
on to future projects in university and beyond.

27
11. Appendix 1: Fully Integrated Testing
11.1. Objective
As each of the project sub systems were created and developed they were independently tested,
including the concentrator dish, azimuth and elevation actuators, and the Arduino coding. However,
fully integrated testing was required to demonstrate the success of the project, to make any
necessary adjustments and to establish what future work would be required.
The objectives of such testing were:
 To ensure that the concentrator could effectively track the sun’s position over a day, using
the coded Arduino Uno to calculate the required position based on the feedback from the
azimuth and elevation potentiometers, and operate the motors as necessary.
 To confirm that the solar concentrator would focus sunlight onto the heating element.
 To find the temperatures that system components could reach in direct sunlight, including
the temperature of 2.5 l of water in the storage tank and the surface temperature of the
heating element.
11.2. Procedure
The system was ready for integrated testing shortly after the spring break, so appropriate permission
was acquired for the group members to take the project to the top level of Duke Street multi-storey
car park, Glasgow, chosen for it’s ideal unobstructed view facing south over the city. For this
permission to be granted, a risk assessment and mission statement were written up, and public
liability insurance was secured from the university. Students taking part in the experiment had to
wear appropriate PPE including lab coats, sunglasses and sun cream. The top level of the car park
was closed to the public, this is normal for the car park since it is newly constructed and not yet fully
open.
The experiment was conducted on Friday 18 April 2014, with the equipment assembled on the car
park roof at 09:30. A thermocouple was inserted into the water tank so that the temperature of the
water could be measured, and a GoPro camera was set up to observe the experiment, taking a
photograph every 60 seconds.
Before this experiment, little time had been spent testing the water pump since it was a fairly new
addition to the project. At his stage it was connected directly to the battery, and was independent
from the Arduino.
Figure 11.1 Selection of GoPro Photographs

28
11.3. Results
The experiment began at 10:00 and almost immediately it was clear that there were power issues,
since the water pump being used was quickly draining the battery, drawing so much current that the
azimuth and elevation motors could not move at the same time the pump was running. As soon as
the pump was unplugged the motors would operate normally. Therefore the system was only run
for around 50 minutes before the pump was disconnected to allow the battery to charge from the
solar panel. During this down time the concentrator was covered to prevent the heating element
from overheating. Before this, however, the temperature of the water had increased from 24°C to
30°C, as illustrated in Figure 11.2.
Figure 11.2 Thermocouple Reading of 30°C after 35 minutes of Experimentation
At 12:00, after 1 hour 10 minutes of downtime, the experiment was restarted, with an extra solar
panel to help provide more power to the battery. Over this time the water temperature had
dropped by only 1°C, and soon regained this heat once the experiment was underway.
Figure 11.3 Thermocouple Reading of 30°C at 12:17
The experiment was then run until 14:00, with a ten minute break around 13:00 to allow the battery
to recharge slightly. The maximum temperature reached just before the end of this phase of the
experiment was 42°C, a significant increase from the starting temperature, but not reaching the
target of 60°C. Figure 11.4 below shows the thermocouple reading just before the maximum was
reached.

29
Figure 11.4 Thermocouple Reading of 40°C at 13:40
After 14:00 the water in the tank was replaced with a smaller volume of 1l, and all the electronics
apart from the pump and the solar panels were disconnected from the battery to try and maintain
the experiment for as long as possible. The dish was moved by hand to save power. This however
did not last long since the battery died very quickly, before any useful results could be taken.
Therefore this method was abandoned around 14:30 so that the battery could be charged before
the capabilities of the dish to align to the sun from facing the wrong direction could be tested.
This commenced at 15:00, with the dish moved to face east at maximum elevation and the water
pump switched off the Arduino was powered and controlled the motors to align the dish accurately
with the sun. This was repeated three times and was successful with each attempt.
Throughout the day, the temperature of the heating
element was occasionally measured using the
thermocouple. This temperature was discovered to
be astonishingly high, remaining over 100°C
throughout the day. The highest temperature
recorded on the surface of the element was 201°C.
Figure 11.5 Surface Temperature of Heating Element
Reaching 201°C

30
11.4. Conclusion
This day of experimentation provided many useful results that were applied to the development of
the project, the main outcomes being:
 The system could accurately track the sun throughout the day, and could return to the
position of the sun should it become misaligned.
 The concentrator effectively focussed the sunlight onto a heating element, the surface of
which reached very high temperatures.
 While the solar panel chosen could maintain power for the Arduino and the motors, the
water pump was incredibly power hungry and would have to be adjusted before future
testing. This led to the implementation of the motor controller and relay to control the
pump so that it could be switched off while the motors were running.
 In three hours of testing, the water temperature in the tank only rose by around 20°C, but
areas for improvement were identified. These are explained in this report.
 The insulation covering the water tank was effective, only losing 1°C in over an hour.
Although there was unobstructed sunlight throughout the day, there was a fairly cool cross wind
blowing. The wind mainly remained gentle throughout the day with occasional gusting, and did have
a cooling effect on the water system. This was particularly noticeable in the afternoon when the
wind was stronger. The concentrator itself withstood this wind and did not become misaligned at
any time.
Figure 11.6 Test set up on Duke Street Car Park Top Level

31
12. References
[i] http://www.ijera.com/papers/Vol2_issue1/EF021822830.pdf, Accessed 18/02/14
[ii] http://www.solarmirror.com/fom/fom-serve/cache/43.html, Accessed 18/02/14
[iii] http://www.ijera.com/papers/Vol2_issue1/EF021822830.pdf, Accessed 18/02/14
[iv] http://m.instructables.com/id/Building-a-Parabolic-Solar-Hot-Water-Heater-using-/,
Accessed 18/02/14
[v] http://www.ecogeek.org/component/content/article/3439, Accessed 18/02/14
[vi] http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html,
Accessed 18/02/14
[vii] https://github.com/msparks/arduino-ds1302 Accessed 22/09/13
[viii] http://www.hse.gov.uk/legionnaires Accessed 01/04/14
12.1. With Special Thanks To:
 Dr Bruce Stephen, Supervisor, University of Strathclyde
 Dr Brian Stimpson, Secondary Supervisor, University of Strathclyde
 Mr John Redgate, Faculty of Engineering, University of Strathclyde
 Mr Duncan Lindsay, Department of Design, Manufacturing and Engineering Management,
Unicersity of Strathclyde
 Mr William Arthur, University of Strathclyde
 Miss Carolyn Gethin, Inverness

32

33

34

35

36

Controller for Solar Generation - University of Strathclyde Project Report

Recommended

Recommended

More Related Content

Similar to Controller for Solar Generation - University of Strathclyde Project Report

Similar to Controller for Solar Generation - University of Strathclyde Project Report (20)

Recently uploaded

Recently uploaded (20)

Controller for Solar Generation - University of Strathclyde Project Report