1. WORK REPORT
To: Concerned Authorities, Indian Institute of Science, Bangalore
From: VISHAL CHANDRASHEKAR
Designation: Junior Research Fellow
Department: Divecha Centre for Climate Change, Indian Institute of Science, Bangalore
Guide: Dr. SHEELA K RAMASESHA, Visiting Faculty
Date: 16 APRIL 2014
Duration of the term: 1 AUGUST 2013 TO 31 MAY 2014
Subject: Summary of the work carried out by the Candidate during his tenure at the Indian Institute
of Science, Bangalore
1. INTRODUCTION
This report intends to put in words the work that had been carried out by the candidate during the
tenure at the Indian Institute of Science. Figures, graphs and tables have been provided wherever
necessary. Conclusions, results and further work that may be carried out have also been discussed.
2. LIST OF PROJECTS UNDERTAKEN
Some of the projects required constant innovation, design changes and others required periodic
up-keeping and trouble-shooting. The details of the projects undertaken have been described in the
following paragraphs and the role played by candidate.
2.1 PARTIAL SOLAR POWER FOR TRAIN COACHES
Solar power is a useful auxiliary power source. Solar alone cannot replace the traction provided
by locomotives. But can they be used to cater for the lighting loads of the coaches? Lighting loads
are catered by the alternators in the coaches or by power cars. The power cars have Diesel powered
generators which satisfy the electrical lighting loads (including fans, lights, emergency lights etc.)
Diesel generators consume enormous amount of Diesel. Can this consumption of fuel be avoided

2. or mitigated?
Fig.1 Schematic of the proposed design
The tops of the solar panels are exposed to solar radiations almost throughout the year. The aim of
this work was to determine the feasibility of utilizing incident solar energy on the roof top of the
coaches to supply for the electrical lighting loads. This intention is to use the solar radiation to
minimize the consumption of diesel thereby conserving resource and prevent substantial emissions
of CO2.
Fig.2 Representation of the proposed scheme on a model coach
It was proposed that the roofs of the coaches be mounted with solar modules. It was difficult to
mount the solar modules as such, since they cannot be bent to fit the shape of the roof surface. We

3. proposed to use the same cells but without the external frames. Alternately the cells may be
sandwiched between two thick sheets of plastic or thin film modules may also be considered.
Table.1 Calculations of fuel savings
This table has been taken from our published paper (July 2014).
Table.2 Calculation of emissions reduced by implementing the scheme
This table has been taken from our published paper (July 2014).
It was estimated that 90,804 litres per year per rake would be saved if this system was implemented
(Table.1). This figure was calculated taking into account Alstom-LHB coaches of the Indian
railways and solar irradiation in India. Not only would there be a significant reduction in fuel
consumption, CO2 emissions of around 240 Tonnes would also be prevented (Table. 2).
Note: This project has been a tremendous success. The Indian Railways have implemented this on

4. a couple prototypes around the country. Upon analysis from the trials, it is possible that this idea
will make its way onto long distance trains across the nation. This paper has been presented at the
IAFOR North American Conference on Sustainability, Energy and the Environment organized at
Rhode Island in September 2014.
2.2 S.S.C.U ROOFTOP TRACKER PROJECT
Trackers are performance enhancement devices which improve the achievable efficiency of a PV,
CPV or CSP systems. These devices are electronically controlled and orient the entire assembly
of panels such that they are normal to the direction of the Sun’s rays during the sun light hours.
This way the portion of the diffuse radiation incident on the panels is less. More the amount of
direct radiation incident, more the power that can be generated as the incident light will be more
intense.
The role played in this project was to make sure the system works well. This tracker unit was
installed atop the S.S.C.U (Solid State Structural Chemistry Unit) building. In the same area is also
present fixed solar system; the idea behind was to compare the efficiencies that can be achieved
by the both the systems subjected to the same sun light, wind, and other conditions.
Water seepage into one of the actuators (servos motors) was a major flaw in the manufacture of
the system. The system was dysfunctional because of it and spare components are hard to find
according to the agency in charge of maintenance.
Preliminary experiments were conducted into the effect of wind on the temperature of the modules.
A full day measurement of temperature was carried and it was determined that Dual-axis tracker
is gets cooler than fixed system when there a sudden gust of wind blows. The data collected was
counter posed on the weather data and it was determined that the wind indeed reduce the
temperature of Dual-axis systems more than fixed systems.
The data obtained was interesting and lead to the development of a new idea: to incorporate wind
data into the solar tracking algorithm. By doing this, it is possible to orient the modules for a
sometime such that the back of the module faces the wind. But not to misalign the module too far

5. off from the Azimuth/ Elevation of the sun (Normal position). In normal circumstances, higher
temperature leads to significant reduction in efficiency. This may be countered to a calculable
extent by orienting the modules back slightly toward the wind. The modules would be cooled
hence performing at higher efficiency. This was inferred by looking at the Graph.1; the spikes in
the temperatures of the Dual-axis tracking system was attributed to wind effect. A paper was
written on this algorithm but was not published due to lack of testing and time.

6. Table.3 Temperatures of the fixed panels and dual axis tracking panels at different times
Time Fixed Panel Temperature in ⁰C Dual Axis Temperature in ⁰C
07:45 24 30
08:00 25 32
08:15 26 32
08:30 26 33
08:45 26 35
09:00 30 35
09:15 30 36
09:30 32 37
09:45 35 38
10:00 36 40
10:15 37 41
10:30 39 43
10:45 40 43
11:00 40 45
11:15 43 47
11:30 47 47
11:45 45 46
12:00 51 48
12:15 51 47
12:30 42 41
12:45 41 36
13:00 45 45
13:15 47 46
13:30 49 48
13:45 47 51
14:00 49 50
14:15 49 51
14:30 46 51
14:45 45 51
15:00 45 52
15:15 42 49
15:30 39 50
15:45 34 46
16:00 32 47
16:15 29 42
16:30 28 36
16:45 29 33

7. Graph.1 Variation of the temperatures with time of the Fixed panel compared with panels on Dual-axis tracker
2.3 SOLAR REFRIGERATION
Refrigeration is very important in modern community. It helps to store food, medicines etc.
Refrigeration is again a very modern invention and is widely available for urban people.
Penetration of the refrigeration in rural areas are very small as the grid does not reach many of the
villages and the system is quite expensive taking into account the income of rural people.
The intention of the work was to fabricate and test a system functioning based on Adsorbtion
phenomenon. The refrigerant or working substance was Methanol. Methanol adsorbs onto the
surface of the charcoal when temperatures are lower and desorbs when temperatures are higher.
The entire system was kept in vacuum. During the night time one valve into the chamber was kept
open and the other leading to the tubing was closed. The Methanol would get adsorbed onto the
surface of finely powdered charcoal. During the day time, valve leading out of the chamber was
opened and the one leading into it was closed. Since the chamber is kept exposed to the external

8. radiation, methanol would desorb. This vapor of methanol now moves through the tubing made of
copper. At the bottom is kept an ice box where ice/cold water is obtained. As the methanol vapor
passes through the tubing, it condenses subsequently expanding through a capillary valve. Out of
this emerges saturated Methanol liquid which flows to the evaporator part of the tubing. Here the
tubing absorbs heat from the water in the box and turns into vapor. This vapor then moves back
into the chamber when the respective valve is opened. During the night time the vapor would
adsorb again onto the charcoal substrate.
Fig.3 Refrigeration tubing that was used in the setup

9. Fig.4 Completed adsorption refrigeration system
The system works only satisfactorily. Due to unreliable valves and regulators, leaks cannot be
prevented leading to dissipation of vacuum. The lowest temperature obtained at the ice box was
around 10 - 15⁰ C lower than the ambient temperature.
2.4 INSTALLATION OF C.P.V ATOP C.A.O.S BUILDING
Concentrated solar Photovoltaic is preferred where large amount of power must be generated from
a small area, also where the cost must be reduced (it must be noted that the tracking system
increases the cost of the system). Solar modules cost more because of the high purity of silicon
semi-conductor that is used. High purity silicon will consume more resources to manufacture. The
idea here is to reduce the amount of silicon semi-conductor material used by concentrating the
light onto a small strip of silicon (semi-conductor). Essentially the utilization of the semi-
conductor becomes higher as it is exposed to more sunlight. But, silicon is a material with a finite
band-gap. Only a small portion of the incident whose energies are more than band gap can excite

10. the electrons to valence bands generating electricity. Therefore, much of the incident radiation is
not at all used. One of the solutions is to use multiple semiconductor materials of different band-
gaps. The materials are placed on top of each other, forming a multi-junction diode. As light passes
through each of the materials, a portion of the total incident spectrum is imbibed. As light passes
Fig.5 CPV system partially assembled
through three consecutive layers, lot more of the energy of the incident radiation is absorbed to
generate energy.
Solution is still not feasible. Since the light is concentrated incident radiation has to be normal to
the panels for it focussed properly at the panels. Therefore, the entire system has to be tracked with
respect to the position of the sun. A new tracker system was obtained from Greensource Pvt. Ltd.,
Taiwan. This had to be mounted and installed on the rooftop. I supervised the laying of foundation
to be perfectly smooth. Each component was supplied to us by the company. This had to be
assembled on the roof. Couple of days were spent in preparing a plan, laying the foundation,
inventory of the shipped components etc.. The experts from Taiwan had come to instruct us in

11. order to assemble all the components and make it function. We spent around three full days in
getting the components in order and assembling it. Later a flat panel was also kept in the same
assembly. This was done to compare the efficiencies and temperature effects of flat panel with
concentrated modules both being tracked.
Fig.6 Fully assembled and functional CPV system with flat panel mounted
2.5 PARABOLIC CONCENTRATOR – WATER DISTILLATION UNIT
Clean drinking water is a scare commodity. In remote, poor areas this is even more so. The aim of
this project was to design, build and test a solar powered distillation unit. This device has to be
inexpensive and be made out of locally available materials. We decided at the beginning that every
aspect of the project shall be thought and re-designed if necessary to optimize performance as well
as cost; hence numerous characteristics of the concentrator differ from the convention.

12. 2.5.1 Initial Trials
Initially, a PVC pipe of 30 cm diameter was cut into half. The inner surface of the pipe was coated
with Aluminium foil. At the point where reflected light was most intense, a receiver was placed to
collect the heat being concentrated on it. A black painted metal tube was used as the receiver. The
orientation of the assembly was kept in-line with the North-South direction. Conventionally a East-
West orientation of the axis is preferred. But, it was found that North-South orientation showed
higher receiver temperature compared to East-West orientation. Hence the parabola was kept with
its axis in-line with North-South direction thereafter. Fig.8 shows the initial design that was used
along with the preferred orientation. The temperatures of the collector tube observed for East-West
orientation recorded was 37ºC, lower than 58.5ºC for the North-South orientation. These
observations were recorded on 3 January 2014 (GHI 5.15 kWh/m2
).
Fig.7 Initial design of the parabola using half-cut PVC pipe

13. Fig.8 North-South orientation of the Parabola axis- temperature observed was 58.5ºC
Table.4 Temperature observations of tube and water temperatures at the end of trial
SI No Time of Temperature of the Tube in Temperature of the
observation °C Water observed at
outlet in °C
T 15:30 42
1
44
T 15:55 45
2
T 16:05 48
3
Table.4 presents the data collected on 12 January 2014 (GHI 5.57 kWh/m2
). It can be seen from
the above data a lot has to be improved. If the collector tube was kept at the focus of a parabolic
the temperature obtained would be higher.
2.5.2 Design and Fabrication of Parabolic surface
All the incident radiation normal to the axis of the parabola will be reflected onto the focus. A
parabola was designed keeping in mind the constraints of the dimension of the PVC pipe. Aperture
was taken as 30 cm. Fig.9 shows the Auto-CAD diagram of the required parabola. The parabola
was made out stainless-steel. 3mm thick S.S 308 sheet was rolled to the dimensions dictated by
the Auto-CAD diagram. Cold rolling was used to bend the entire sheet to the specified dimension.
The concentration ratio was around 11. The next aspect was to design a suitable collector tube.

14. Fig.9 Auto-CAD diagram of the profile of the required parabola
2.5.3 Collector Tube Design
Collector tubes are another feature that was to be re-designed. Conventional collector tubes used are
usually black metal tubes enveloped by glass cylinder of slightly larger diameter. The glass covering
prevents radiation losses. These kinds of receiver tubes are very expensive and require deep
technical expertise. Generally, the gap between the metal tubes and glass envelope are evacuated.
Maintaining the vacuum means delicate operational requirements and makes the system more prone
to damages.
The initial design for receiver tubes involved a glass tube with bent ends serving as inlet/outlet for
water/steam. Fig.10 shows the fabricated glass receiver tube. The tube was filled with sand initially
to act as the heating agent that will subsequently transfer the heat absorbed to water and vaporize it.
Sand has a lower heat capacity than water and therefore would heat up a lot faster than water. The
idea was to constantly heat up water until it turns vapor and sustainably doing the same for the
prescribed flow rate.

15. Fig.10 First design of the collector tube
There were some flaws in the design of the collector tube. The evaporated water would collect at
the top of the collector tube. Due to temperature differences between the top and bottom of the tube,
the water deposited at the top would condense. The entire assembly was kept an incline. So, the
water droplets start moving along the top surface toward the outlet. As it moves, the drops become
larger (heavier) and plunge into the dirty collector (sand) bed. The water that was distilled becomes
impure again by mixing with the sand.
There was another problem. Glass being transparent, some of the radiation that was incident on the
collector tended to escape from the collector itself. The solution to this problem was simple. The
top half of the collector tube was lined with Aluminium foil on the outside. The foil being reflective,
bounced back most of the radiation that earlier used to escape. A temperature difference of about
30ºC was observed because of this. This experiment was conducted on 16 April 2014 (GHI 5.60
kWh/m2
). Fig.11 shows the improvement that had been done.
Fig.11 Top surface lined with Aluminium sheet (here it is covering half the length, this is for illustration purpose
only)
To counter the above mentioned flaws, a new collector tube had to be designed. Fig.12 illustrates
the new tube that was fabricated. One of the ends is tapered and bent upwards; this is the inlet for
water from the tank. Along the top inner surface of the tube, a glass pipe of small diameter was
placed. This glass pipe was held in place using strong metal wire. The intention of placing the glass
pipe was to guide the passage of water smoothly without it dropping into the collector bed. At the

16. outlet end a boat shaped component was fused with the basic tube. This component collects the
water from the glass rod and delivers to a beaker through a pipe.
Fig.12 New collector tube design
Sand was mixed with charcoal to give it a black tinge. This helped to absorb more heat. Sand was
not suitable to be used as a heating agent; this is because sand being free-flowing tends to collapse
onto itself when water passes through it. This prevents the flowing of water as the sand blocks its
passage. For this reason, small dark colored pebbles were used instead of sand as the heat collecting
medium. There are gaps between the boundaries of pebbles, thereby not obstructing the flow of
water the medium. Pebbles were mixed with charcoal to enhance heat absorption.
2.5.4 Selection of reflector material: invention of a novel reflectivity measurement
unit
Objectives
The purpose of this study is to compare the reflective performance of different materials. These
materials are to be used in Parabolic concentrators to effectively and coherently transmit the incident
normal light. Incident light has to be transmitted or converged on a specified point called FOCUS.
A Receiver collects all the normal incident radiation focused at it (reflected by the parabolic
surface).
Current concentrators use materials that are very expensive and exclusively made by multi-national
giants. The materials essentially use silver/ Aluminium metal coatings on a thin transparent
polyester/plastic substrate. These metals are very rare and/or energy intensive to extract/ deposit.
Therefore, alternatives have to be found which are adequate for the focusing of light and yet have
to be inexpensive compared to the alternatives. The effectiveness of paper and plastic were
evaluated. A photodiode was utilized to measure the power of the concentrated radiation. The
performance of different selected materials was compared. Solar Mirror 1100 was taken as the

17. reference material. It would be wrong to pursue the quest of finding a suitable material that will
outperform Solar Mirror 1100 product. A material whose performance is comparable to that product,
adequate for the specific use and available at a fraction of the cost is what this study intends to
investigate.
Method
To compare performance of reflective materials, it was necessary to test. The unavailability of a
spectrometer/ reflectivity measurement unit spurred the author to invent his own! Two
characteristics of parabola were exploited for this study. First, a light source kept at the focus of a
parabola will produce coherent rays. It is important to produce coherent (parallel) rays in order to
replicate the incoming rays from sun which is near coherent. Second, coherent rays incident on the
parabola (parabola mirror) normal to its axis will be reflected onto a single point called the Focus.
Fig.13 Setup showing light-source and photodiode

18. For this setup to work effectively, we need two identical parabola surfaces kept opposite to each
other. Let us call these P1 and P2. P1 is made out of stainless steel. It was made by machine rolling
a sheet of stainless steel having 3 mm thickness precisely as per specified to obtain a perfect parabola
surface derived from standard equations of the curve. P1 is coated with the Solar Mirror 1100 film.
The reflective performance of this film considered as the optimum (100 percent). At the focus of P1
was kept the photodiode. P2 on the other hand was made by bending reflective Aluminium sheet so
as to form a mirror image of P1. The shape was kept intact by using fasteners. At the focus of P2 is
the light source. Here the light source utilized was a CFL bulb, power consumption is 11W.
According to the website of the manufacturer the Luminous Flux to this particular bulb was recorded
at 600 Lumen. Color of the light seen was cool-white.
Fig.14 The whole assembly with two parabolas and the photo-diode control box
Now that the setup is assembled, let us start with measurement of reflectivity values and further
move onto comparison of the property in various materials. The aim of the experiment is to measure
the reflectivity of various materials. Photo-diode does not measure reflectivity. It only measures the
energy of light that is incident on a point. Assuming that P2 produces coherent rays, P1 will reflect

19. the entire incident light on the focus of P1. The photo-diode will measure the power incident at the
focus of P1. If the reflection is absolute, then all the incident rays will converge at the Focus of P1;
if the reflection is not perfect then some radiations will be reflected diffusely. Hence all the rays will
not converge at the focus. The power that is measured at the focus of P1 is different for different
materials used as reflecting sheets. Since the light source is same for all the materials and the surface
that makes the light coherent (P2) is same; it will make comparing the performance of various
materials easier.
Material/ Material-Combinations Used
As mentioned earlier, the Solar Mirror 1100 film was considered as the reference. The performances
of various materials were compared with respect to this film. The materials must be easily available
and be relatively much cheaper. Below are described the measurements of the various materials/
material combinations considered along with relevant graphs. Ultimately, comparative studies of
the performances of various materials have been carried out.
The wavelengths of 405 nm and 650 nm correspond to violet and red colors respectively.
Material 1 – Solar Mirror 1100
This material was developed by 3M, whose expertise lies in tint films for homes and automobiles.
This film was tested by NREL and has reflectivity of around 98%. The material is essentially
silver deposited onto a substrate. The substrate may be either polyester or some other material.
This material is widely regarded as the best in the industry.
Table.5 Power received by photo-diode for Solar Mirror 1100
Wavelength in nm Power reflected measured in mW
405 0.705
650 0.412
830 0.249
980 0.2023
1060 0.42

20. The trend in the reflection of wavelength seems to comply with the other materials as well. The
measurement was done for the various wavelengths that can be measured by the device.
Material 2 – Lykar Sheet + OHP Sheets
Lykar is the material that is used to print poster or business cards. The performance of this material
without any other material combination is around 60% that of Solar Mirror 1100. Lykar has a
porosity that is less than plain white sheet of paper. This is attributed to the presence of plastic/wax
coating on the top surface. It can be easily understood there is a change in the reflectivity of the
combinations of materials as soon as OHP sheets are added. General optics would state that the
overall reflectivity will increase with the increase in the number of layer of plastic. This may be
because the overall porosity of the material is reduced and making the reflection more specular. In
this case an ambiguity is apparent. This logic does not hold good.
Table.6 Power received for various combinations of Lykar and OHP sheets
Wavelength in nm Power in mW
Plain sheet 1 OHP 2 OHP 3 OHP
405 0.348 0.326 0.347 0.362
650 0.206 0.191 0.204 0.212
830 0.1294 0.121 0.1298 0.1349
980 0.0986 0.092 0.0985 0.1031
1060 0.205 0.194 0.207 0.217
The reason for decreasing reflectivity when the first layer of OHP is added seems to be because of
the imperfections on the surfaces of the plastic layers. It is known that when light moves from one
material to another having different refractive indices, there is bound to be change in path of the
light. It may be that as the number of OHP layers increase there is a gradual change of refractive
indices i.e: the lights moves from air to a plastic layer and there may be air gaps which negates the
initial refraction by much. This material is inherently less porous and therefore more specular than
the non-coated Lykar paper. The reason for it having less porosity may be because of the top layer
of wax/ plastic.

21. Fig.15 Power received versus wavelength for various combinations of Lykar sheet
Material 3 – Plain Paper (White Sheet) + OHP Layers
Plain white sheets are known to be reflective. White color is so because; it reflects all radiations
of all wavelengths absolutely. That is the basic principle on which optimum reflection relies. White
paper is generally porous resulting in diffuse radiation. White paint also results in diffuse if the
coating is not smooth; even imperfections at the nanometer level results in diffuse radiation. The
coating surfaces of the parabolas that are commonly used are usually gray – as close to white as
possible. It is required that reflecting surface must be metallic. Metals are by nature reflective.
Generally, transition metals are good conductors implying that the outermost rings of electrons are
quite mobile. It would be sensible to make reflecting surfaces out of metals: this is what is used in
mirrors. In my observation a good reflective surface has the following properties: it is dense and
atoms are tightly packed yet outwardly mobile and the surface subjected to light is extremely
smooth having minimum porosity. Needless to say thought this is the general trend; it is not
absolute. Some metals are more reflective/ lustrous than others. Mirrors used around the house
utilize silver as the reflective foil surface. The trend here seems to be different compared to that of
Lykar with OHP sheets.

22. Table.7 Power received for various combinations of paper and OHP sheets
Wavelength in nm Power received in mW
Plain sheet 1 OHP 2 OHP 3 OHP
405 0.335 0.4 0.331 0.357
650 0.198 0.231 0.192 0.210
830 0.1247 0.1459 0.1218 0.1328
980 0.0942 0.1106 .0926 0.1007
1060 0.198 0.231 0.195 0.212
Fig.16 Power received versus wavelength for various combinations of plain white sheet
Contrary to the earlier trend followed by the Lykar sheet; increasing the number of OHP layers
DOES NOT increase the performance of the sheet. Paper coated with one layer of OHP is better
than plain paper. This can be explained by reasoning that the overall porosity decreases making
the reflection more specular. However, adding another layer of OHP lowers the performance and
a third increases the performance of the sheet but only marginally. White paper inherently is much
more porous; addition of OHP greatly decreases the porosity rendering the reflected light more
specular. From the measurements of White paper and Lykar materials – there seems to be a strong

23. characteristic that may be inferred. Specular reflection depends on the amount/ type of plastic that
is used. There seems to be a optimum quantity of plastic for which performance would be greatly
increased.
Material 4 – Aluminium Sheet
Table.8 Power received when Aluminium sheet is used as reflecting surface
Wavelength in nm Power reflected measured in mW
405 0.626
650 0.343
830 0.2168
980 0.1616
1060 0.342
Aluminium sheets are quite versatile and the polished sheets are widely used to coat the reflector
surfaces. As with silver foils; Aluminium extraction is very laborious and resource depleting.
Another major problem with the use of Aluminium is spring back. The metal un-bends back to
initial state when released from the bent position. This means that the sheet may NOT retain the
shape of the required parabola for long.
COMPARISON OF MATERIALS
The better of the two paper-plastic combinations was selected and plotted in the same as the
Aluminium sheet and Solar Mirror sheet. This graph is represented in Fig.5. The performance of
materials seems to be very similar to each other in the near IR region of the spectrum. But, Solar
Mirror 1100 and Aluminium sheet outperform the combinations of sheets.
BUT, none the less this study proved something important. Addition of transparent OHP sheets to
the base reflective material (white paper/Lykar) varies the performance of the sheet greatly. It can
be seen that addition of a OHP sheet layer on white paper increases its performance by 20%.

24. Fig.17 Comparison of performance of various materials
Further Work to be Carried Out
This study presents the interim analysis. A thorough analysis must be again conducted to verify
the validity of the results; standard methods of measurements need to be used. Plastic sheets of
different thickness lined on the white paper/ Lykar may be considered for study. Refractive indices
of the materials must be ascertained in order to gain further understanding into the problem. The
parabola may be lined with the material/ material combination and tested out in the field. This is
necessary to gauge the ability of these materials to withstand UV, water vapor, heat etc.

25. Final Design
Fig.18 Final assembly of the parabola concentrator
Table.8 Volume of water collected for clear days for different GHI
Full day trials were conducted for a couple of days. Table.8 presents the data for three days when
the sky was clear and particularly hot. In the final design, two concentrators were fitted in the same
frame. One was that fabricated made out of stainless-steel and other was made by bending
Aluminium sheet approximately in the shape of a parabola. The stainless-steel parabola made lined
with Solar Mirror 1100. The parabola made out of bent Aluminium sheet heats up the receiver
(black painted metal tube to around 70ºC before being sent to the stainless-steel parabola. The
entire system was moved with the position of the sun once every one hour.
Trials Date GHI in kWh/m2
Volume of water
collected in L
1 MARCH 25 6.564 2.81
2 APRIL 16 5.60 2.4
3 APRIL 19 5.91 2.54

26. 2.6 CAM ACTUATED TRACKING
Tracking of the panels of a PV system would in theory increase the achievable efficiency to around
20% over the efficiency of fixed solar modules. Present tracking systems utilize reliable electronic
systems. Usually it consists of an I.C, storage, input and output cables. The motion being controlled
by servo motors.
Trackers are simple devices that boost the efficiency that can be achieved and improve the cost
effectiveness of a PV plant making it all the more feasible for the end user. Zenith positions of the
sun vary significantly with seasons. Very efficient tracking mechanisms track both the azimuth
angle and zenith angles, hence maximum solar energy is available to panels. In effect the wastage
of solar radiation is much reduced. Trackers are generally cost effective and capable of reasonable
accuracy. The common tracker is the chronological tracker that has a storage unit in them. This
log has recorded data for the optimal tracking position of a tracker for that latitude. The internal
electronics orient the entire assembly to a pre-determined position making it in harmony with the
movements of the sun.
Disadvantage of electronic tracking systems:
Prone to damage due to water/moisture seepage
Not robust, generally in need of much maintenance
Cannot be used in regions where electronic components are obsolete
Fluctuation in power supply leads to burning of the circuit
Auxiliary power is compulsory for powering the servo motors
Here, the idea was to create a mechanical tracker which utilizes little or no electronics. Eliminating
electronic components would be the drive behind this work. The system uses a gear, whose teeth
are of uniformly increasing length. A uniformly unwinding spring drives the gear which moves
the assembly uniformly throughout the day.
Design of Incremental Gear

27. For optimum tracking, it is sufficient to move the entire assembly in intervals of 15˚ azimuth
movements of the sun. Continuous azimuth tracking is ideal but this makes for mechanism that is
more complicated and the gain in efficiency over the intermittent tracker is not significant.
Movement of each gear has to move the entire assembly by 15˚. The radius of the first gear is
arbitrarily taken to be 10 mm.
For movement of 15˚ and first gear teeth being 10 mm, Arch length of motion is S.
S = 10 x (15 π/ 180) = 0.2617 mm
The arch lengths of the consecutive motions have to be multiples of this. The second motion has
to have twice the arch length and the angle traversed is 30˚ and so on.
Below are the calculations showing the gear teeth length of the consecutive gears, angle of motion
traversed.
The incremental gear would move the over-hang of the assembly in intervals of 15˚. it assembly
would remain there till the next gear comes into place where by the assembly is moved by a further
15˚ and so on. Locking mechanisms have been devised which would keep the assembly in position
until the consecutive gear moves into place. Locking is important to prevent wavering of the
position in consequence to wind and other factors.
Table.9 Specifications of the initial design of an incremental gear
Number of teeth 10
Step increment 15˚
Pitch Dia 500 mm
Length of first gear 10 mm
Effective azimuth covered during a
150˚
day

28. Table.10 Design of parameters of the incremental gear, radius of the consecutive gear teeth
Fig.19 Drawing of the initial gear design
SI No. S in mm r in mm Θ in Deg.
1 2.617 10 15
2 5.235 19.9 30
3 10.47 40.09 45
4 20.94 80.015 60
5 41.887 160.05 75
6 83.77 320.09 90
7 167.5 640.044 105
8 335.1 1280.09 120
9 670.2 2560.1 135

29. Design of CAM
Cams are used in automobiles to move the valves. Generally Cams have a rise period, two dwell
periods and a return period. But for purpose the Cam need have a Dwell period as the over-hang
has to be continuously moving. The return period is much shorter than the rise period. Varying
radii of the Cam make the assembly rotate continuously to be continuously orientated normal to
the sun.
Table.11 Specifications of the Cam
Follower type Knife Edge
Dwell Period 0˚
Rise Period 324˚
Return period 36˚
RPM 2.08 x 10-3
Base Circle Dia 10 mm
Fig.20 Design of the required Cam

30. Fig.21 Profile of the required Cam, the run and rise period are demarcated
Fig.22 representation of Rise and return cycles ingrained in the Cam

31. Fig.23 Dimensions of the gear teeth
Final Note:
A sincere thanks to all who were involved in these projects. Without the support of the staff and faculty at the Divecha
Centre for Climate Change much of this may not have been possible.