FIELD OF THE INVENTION
This invention relates to the utilization of solar energy using a closed hemi-cylindrical solar heat
collector, which fulfills the gap between conventional Flat Plate Collector (FPC) and
Concentrated Collector.
BACKGROUND OF THE INVENTION
Various types of collectors are being used to utilize solar radiations, which includes
concentrating collector, non-concentrating collectors, and convex lens based. P.P. Patil et al.
(2015) designed a solar water heater to obtain hot water for the domestic and industrial
applications. The work has been done in the field of cover materials, absorber plate materials,
absorber and glazing coating. Designing a solar water system involves appropriate selection of
each component for the desired capacity and location of installation for solar water heater to
produce hot water. Various factors and correlations for design of collector, storage tank and
insulating material are briefly discussed in this paper [1]. Bashrat Jamil et al. (2016) studied the
availability of solar radiation for south-facing flat surfaces in humid sub-tropical climatic region
of India [2]. Y. Raja Sekhar et al. (2009) worked upon flat plate collector and its application for
domestic hot-water, space drying/heating and also for applications requiring fluid temperature
less than 100oC. The collector efficiency is dependent on the temperature of the plate which in
turn is dependent on the nature of flow of fluid inside the tube, solar isolation, ambient
temperature, top loss coefficient, the emissivity of the plate/glass cover and slope [3]. Zhong Ge
et al. (2014) proposed the concept of the local heat loss coefficient and examined the calculation
method for the average heat loss coefficient and the average absorber plate temperature. Energy
rate distribution was analysed when ambient temperature, solar irradiance, fluid mass flow rate
and fluid inlet temperature are set to 20 °C, 800 W/m2, 0.05 kg/s, and 50 °C, respectively [4].
Otanicar, Todd P. et al. (2009) worked on the measurement of total direct radiation on the
plane of the collector, ambient temperature, wind speed, water flow rate, and inlet and outlet
temperatures of the water inside the absorber tube are collected and employed in studying the
performance of the flat plate collector. The values of useful heat gain, overall thermal efficiency,
instantaneous efficiency and hourly thermal efficiency are calculated [5]. M. Jamil Ahmad et
al. (2009) examined the theoretical aspects of choosing a tilt angle for the solar flat-plate
collectors used at ten different stations in the world and makes recommendations on how the
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collected energy can be increased by varying the tilt angle. [6]. Kumari et al. (2015) predicted
the performance of flat plate collector tested for 3 different days, using an application of water
heating. The material used in the work is absorber plate, tube or pipe made of GI, casing and
glass. The absorber plate material is mild steel and tube or pipe material is galvanized iron. Mild
steel material have absorptivity is about 0.8 with black paint coated. The tube material is
galvanized iron which is mild steel with coated with zinc for corrosion resistance. For this
selection of material the maximum efficiency obtained was 9.75% at temperature 670 oC [7].
M.S. Sodha et al. (1981) presented a simple transient model for predicting the thermal
performance of two novel water heaters which combine both collection and storage of solar
energy in a single configuration. [8]. Ari Rabl (1976) compared a variety of different solar
concentrators in terms of their most important general characteristic namely concentration,
acceptance angle, sensitivity to mirror errors, size of reflector area and average number of
reflections. [9]. Soteris Kalogirou et al. (1997) presented a parabolic trough solar collector
system used for steam generation. [10]. M.J. Brookes et al. (2006) tested a parabolic trough
solar collected for development in a solar energy research programme. [11]. Kazy Fayeen
Shariar et al. (2011) improved the design of collector trough in terms of efficiency, lessen the
heat declination, and eliminate the sun tracker mechanism. Most of the existing solar
concentrators use open type trough which cause the rapid heat declination. The design attempted
to lessen the rapid declination and improve the efficiency by introducing Closed Environment
Collector Trough (CECT). The CECT consists of spherical collector trough having a reflective
bottom surface, five evenly distributed lenses, 30° apart from each other, on the upper half of the
sphere to eliminate the sun tracker and hexagonal glasses to make the environment closed and
impose greenhouse effect on the system [12]. Hongbo Liang et al. (2015) summarized the one
dimensional (1-D) mathematical models under different assumptions and details for PTCs. [13].
Srinivasulu Avireni (2005) paper explains the principle of using a converging lens as solar
concentrator. Experiments have been carried out to reveal the effectiveness of such concentrator
for increasing the output of solar cells. [14]. Mayur G Tayade (2015) designed and fabricated a
parabolic trough solar water heater for water heating. [15]. M.T. de Leon (2015) proposed a
method of improving the efficiency of thermo electric generators by using a lens to concentrate
radiation on the heat source of a TEG. The effects of varying the thermo-element length, width,
and membrane diameter on the TEG’s performance are also characterized [16]. Sarada Kuravi
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(2013) presented a review of thermal energy storage system design methodologies and the
factors to be considered at different hierarchical levels for concentrating solar power (CSP)
plants [17]. Ankit S. Gujrathi (2014) investigated the potential of convex lens to be used for
water heating application. [18]. S.S. Kale et al. (2012) revealed the new innovative design,
development of the convex lens CSP system for hot water and steam applications. The CSP is
designed with the six convex lenses of total area 0.0471 m2 and copper receiver tube of size 5
mm I.D. and 8 mm O.D. [19]. Suman et al. (2015) highlighted the advancements made in the
field of solar technology in thermal applications. [20].Ogueke et al. (2001) reported that the
active systems generally have higher efficiencies than the passive systems. [21].
Chuawittayawuth and Kumar (2002) presented the details of experimental observations of
temperature and flow distribution in a natural circulation solar water heating system and its
comparison with the theoretical models. [22]. Ibrahim et al. (2009) showed that spiral flow
absorber collector at temperature of 55 °C (panel temperature) achieved the best mass flow rate
at 0.011 kg/sec and generated combined PV/T efficiency of 64%, with 11% of electrical
efficiency and maximum power of 25.35 W; while a single-pass rectangular collector absorber
obtained the best mass flow rate at 0.0754 kg/sec, when the surface temperature was 392 °C,
generated combined PV/T efficiency of 55%, with 10% of electrical efficiency and maximum
power of 22.45 W [23]. Michaelides et al. (2011) presented experimental investigation of the
night heat losses of hot water storage tanks in thermosyphon solar water heaters. [24]. Oghogho,
Ikponmwosa (2013) designed and constructed a solar water heating system for domestic use
using locally available materialsMaximum fluid output temperature, the collector temperature
and isolation of 55 °C, 51 °C, and 1,480 W/m2, respectively, were obtained on a sunny day [21].
One of the main disadvantages of the solutions proposed in the above listed documents is that
they all require a solar tracking system. The task of the solar tracking system is to rotate and
orient the equipment of the solar energy collector so that the collector’s surface is placed
perpendicular to the solar rays all day long to receive maximum solar energy. The solar tracking
system requires precision and also involves cost depending upon the complexity of the solar
tracking mechanism. Thus, solutions are required for utilizing solar energy so as to enhance the
heat collection capability of the solar energy collector and at the same time eliminate the
requirement of solar tracking for concentrated solar heat collector.
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Prior Arts:
1. Patil, P. and D. Deshmukh, Design Considerations for Flat Plate Solar Water Heater
System. International journal of Science, Spirituality Business and Technology (IJSSBT), 2015.
3(2).
2. Jamil, B., A.T. Siddiqui, and N. Akhtar, Estimation of solar radiation and optimum tilt
angles for south-facing surfaces in Humid Subtropical Climatic Region of India. Engineering
Science and Technology, an International Journal, 2016. 19(4): p. 1826-1835.
3. Sekhar, Y.R., K. Sharma, and M.B. Rao, Evaluation of heat loss coefficients in solar flat
plate collectors. ARPN journal of engineering and Applied Sciences, 2009. 4(5): p. 15-19.
4. Ge, Z., et al., Exergy analysis of flat plate solar collectors. Entropy, 2014. 16(5): p. 2549-
2567.
5. Otanicar, T.P. and J.S. Golden, Comparative environmental and economic analysis of
conventional and nanofluid solar hot water technologies. Environmental science & technology,
2009. 43(15): p. 6082-6087.
6. Jamil Ahmad, M. and G. N Tiwari, Optimization of tilt angle for solar collector to receive
maximum radiation. The Open Renewable Energy Journal, 2009. 2(1).
7. KUMARI, L., PERFORMANCE ANALYSIS OF SOLAR FLAT PLATE
COLLECTOR.
8. Sodha, M., P. Bansal, and N. Kaushik, Performance of collector/storage solar water
heaters: Arbitrary demand pattern. Energy Conversion and Management, 1981. 21(4): p. 229-
238.
9. Rabl, A., Comparison of solar concentrators. Solar energy, 1976. 18(2): p. 93-111.
10. Kalogirou, S.A., Solar energy engineering: processes and systems2013: Academic Press.
11. Brooks, M.J., Performance of a parabolic trough solar collector, 2005, Stellenbosch:
University of Stellenbosch.
12. Shariar, K.F., E.G. Ovy, and T.A. Hossainy. Closed Environment Design of Solar
Collector Trough using Lenses and Reflectors. in World Renewable Energy Congress-Sweden;
8-13 May; 2011; Linkö ping; Sweden. 2011. Linköping University Electronic Press.
13. Liang, H., S. You, and H. Zhang, Comparison of different heat transfer models for
parabolic trough solar collectors. Applied Energy, 2015. 148: p. 105-114.
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14. Avireni, S., CONVERGING LENS SOLAR CONCENTRATOR AND THEIR
POSITION CONTROL USING A MICROPROCESSOR FOR INCREASING THE
EFFICIENCY OF SOLAR PHOTOVOLTAIC ENERGY CONVERSION. 2005.
15. Tayade, M.G., R. Thombre, and S. Dutt, Performance Evaluation of Solar Parabolic
Trough. International Journal of Nano Dimension, 2014. 5(3): p. 233-240.
16. de Leon, M.T., P. Taatizadeh, and M. Kraft, Improving the efficiency of thermoelectric
generators by using solar heat concentrators. 2010.
17. Kuravi, S., et al., Thermal energy storage technologies and systems for concentrating
solar power plants. Progress in Energy and Combustion Science, 2013. 39(4): p. 285-319.
18. Gujrathi, A.S. and D. Gehlot, Testing and Performance of the Convex Lens
Concentrating Solar Power Panel Prototype.
19. Kale, S. and N. Shinde, Design and Development of CSP Using Convex Lenses for
Domestic Water Heating and Steam Generation. IJMER, 2012. 1(2) 12): p. 74-78.
20. Suman, S., M.K. Khan, and M. Pathak, Performance enhancement of solar collectors—A
review. Renewable and Sustainable Energy Reviews, 2015. 49: p. 192-210.
21. Oghogho, I., Design and construction of a solar water heater based on the thermosyphon
principle. Journal of Fundamentals of Renewable Energy and Applications, 2013. 3(2013): p. 1-
8.
22. Chuawittayawuth, K. and S. Kumar, Experimental investigation of temperature and flow
distribution in a thermosyphon solar water heating system. Renewable Energy, 2002. 26(3): p.
431-448.
23. Ibrahim, D., Optimum tilt angle for solar collectors used in Cyprus. Renewable Energy,
1995. 6(7): p. 813-819.
24. Michaelides, I. and P. Eleftheriou, An experimental investigation of the performance
boundaries of a solar water heating system. Experimental Thermal and Fluid Science, 2011.
35(6): p. 1002-1009.
SUMMARY OF THE INVENTION
This summary is provided to introduce a selection of concepts in a simplified format that are
further described in the detailed description of the invention. This summary is neither intended to
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identify key or essential inventive concepts of the invention, and nor is it intended for
determining the scope of the invention.
According to an embodiment of the invention, the preset invention provides a solar hear collector
comprising a receiver base box, a hemi-cylindrical roof fixed on the receiver box, and plurality
of light concentrating lenses disposed on the hemi-cylindrical roof.
In an embodiment, the hemi-cylindrical roof is formed of a plurality of segments joined together,
with each segment being formed of an acrylic sheet strip having light transmittance of about 92%
and refractive index of about 1.49.
In another embodiment of the invention, each strip is provided with holes cut along of a length
direction for accommodating the plurality of light concentrating lenses.
In yet another embodiment of the invention, the plurality of light concentrating lenses are
arranged in two-dimensional matrix form on the hemi-cylindrical roof.
In still another embodiment of the invention, the hemi-cylindrical roof is further attached to the
receiver base box at both lateral ends thereof via covers.
In a further embodiment of the invention, the cover is in form of segment of an arc, with curved
surface of the arc being cut along multiple tangential lines for supporting the hemi-cylindrical
roof.
In a furthermore embodiment of the invention, the receiver box comprises an absorbing plate
configured to absorb at least a part of the concentrated light.
In another embodiment of the invention, the absorbing plate comprises a copper plate having
thickness of 0.4 mm and painted matte black color, the copper plate comprising hemi-cylindrical
grooves for accommodating fluid carrying tubes therein.
In yet another embodiment of the invention, a cold water supply source and a hot water receiving
unit is provided in fluid communication with the fluid carrying tubes.
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To further clarify advantages and features of the present invention, a more particular description
of the invention will be rendered by reference to specific embodiments thereof, which is
illustrated in the appended drawings. It is appreciated that these drawings depict only typical
embodiments of the invention and are therefore not to be considered limiting of its scope. The
invention will be described and explained with additional specificity and detail with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present invention will become better
understood when the following detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout the drawings, wherein:
Figure 1 illustrates a photographic view of segmented hemi-cylindrical roof, in accordance with
an embodiment of the present invention.
Figure 2 illustrates a system including a solar heat collector, in accordance with an embodiment
of the present invention.
Figure 3 illustrates a schematic diagram of an absorbing plate, in accordance with an
embodiment of the present invention.
Figure 4 illustrates a photographic view of the absorbing plate, in accordance with an
embodiment of the present invention.
Figure 5 illustrates a blueprint of a stainless sheet used as the receiver box in accordance with an
embodiment of the present invention.
Figure 6 illustrates a schematic diagram of an interconnection of fluid pipes in between the cold
water tank, hot water tank, and the solar heat collector, in accordance with an embodiment of the
present invention.
Figure 7 illustrates an experimental graph indicating variation in water temperature and solar
intensity with time, using the solar heat collector in accordance with an embodiment of the
present invention.
Figure 8 illustrates an experimental graph indicating variation in thermal efficiency and temp
with time, using the solar heat collector in accordance with an embodiment of the present
invention.
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Figure 9 illustrates an experimental graph indicating variation in water temperature and solar
intensity with time, using the solar heat collector in accordance with an embodiment of the
present invention.
Figure 10 illustrates an experimental graph indicating variation in thermal efficiency and
temperature difference with time, using the solar heat collector in accordance with an
embodiment of the present invention.
Figure 11 illustrates an experimental graph indicating variation in water temperature and solar
intensity with time, using the solar heat collector in accordance with an embodiment of the
present invention.
Figure 12 illustrates an experimental graph indicating variation in thermal efficiency and
temperature difference with time, in accordance with an embodiment of the present invention.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity
and may not have been necessarily been drawn to scale. For example, the flow charts illustrate
the method in terms of the most prominent steps involved to help to improve understanding of
aspects of the present invention. Furthermore, in terms of the construction of the device, one or
more components of the device may have been represented in the drawings by conventional
symbols, and the drawings may show only those specific details that are pertinent to
understanding the embodiments of the present invention so as not to obscure the drawings with
details that will be readily apparent to those of ordinary skill in the art having benefit of the
description herein.
DETAILED DESCRIPTION OF THE INVENTION
For the purpose of promoting an understanding of the principles of the invention, reference will
now be made to the embodiment illustrated in the drawings and specific language will be used to
describe the same. It will nevertheless be understood that no limitation of the scope of the
invention is thereby intended, such alterations and further modifications in the illustrated system,
and such further applications of the principles of the invention as illustrated therein being
contemplated as would normally occur to one skilled in the art to which the invention relates. It
will be understood by those skilled in the art that the foregoing general description and the
following detailed description are explanatory of the invention and are not intended to be
restrictive thereof.
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Reference throughout this specification to “an aspect”, “another aspect” or similar language
means that a particular feature, structure, or characteristic described in connection with the
embodiment is included in at least one embodiment of the present invention. Thus, appearances
of the phrase “in an embodiment”, “in another embodiment” and similar language throughout
this specification may, but do not necessarily, all refer to the same embodiment. The terms
"comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive
inclusion, such that a process or method that comprises a list of steps does not include only those
steps but may include other steps not expressly listed or inherent to such process or method.
Similarly, one or more devices or sub-systems or elements or structures or components
proceeded by "comprises... a" does not, without more constraints, preclude the existence of other
devices or other sub-systems or other elements or other structures or other components or
additional devices or additional sub-systems or additional elements or additional structures or
additional components. Unless otherwise defined, all technical and scientific terms used herein
have the same meaning as commonly understood by one of ordinary skilled in the art to which
this invention belongs. The system, methods, and examples provided herein are illustrative only
and not intended to be limiting. Embodiments of the present invention will be described below in
detail with reference to the accompanying drawings.
Figure 1 illustrates a hemi-cylindrical roof (10) of a solar heat collector, in accordance with an
embodiment of the present invention. At the base of the solar heat collector, a receiver base box
(not shown in Figure 1) may be provided on which the hemi-cylindrical roof (10) may be fixed.
The hemi-cylindrical roof (10) is formed of plurality of segments (12) joined together. Each
segment (12) is formed of a strip of an acrylic sheet. In one embodiment, the acrylic sheet strip is
having light transmittance of about 92% and refractive index of about 1.49. A holding base strip
(16) is provided at the base of the solar heat collector attached to the bottom-most strips of
acrylic sheets to support the bottom-most segments (12) joined together. Further, as seen in the
Figure, each strip in a segment (12) is provided with holes cut along a length of direction, where
each hole accommodates a light concentrating lens (14). As such, a plurality of light
concentrating lenses (14) is disposed on the hemi-cylindrical roof (10). By way of an example,
the lenses (14) are fixed on the holes in the strips of acrylic sheets with the help of silicon. In
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accordance with an embodiment of the present invention, the light concentrating lenses (14) are
convex lenses. By way of an example, white glass convex lenses each of diameter 75 mm with
focal length of 300 mm may be used as the light concentrating lenses (14). Further, the thickness
of the convex lenses at the edge may be 3 mm and at the center, the thickness may be 6 mm.
In accordance with an embodiment of the present invention, the plurality of light concentrating
lenses (14) is arranged in two-dimensional matrix form on the hemi-cylindrical (10). According
to an implementation of the present invention, the total number of segments (12) or the total
number of strips of acrylic sheets used in the hemi-cylindrical roof (10) is nine. Each segment
(12) out of the nine segments (12) is provided with seven of light concentrating lenses (14), for
example, the white glass convex lenses explained in the above example. In one example, acrylic
sheets of thickness 6 mm can be cut in dimension of 640* 115 mm and, in each strip seven
stepped holes are cut along the length of the acrylic sheets for the fitment of the convex lenses
(14). The distance between the centers of two consecutive holes in each strip is 85 mm. Thus, the
total number of light concentrating lenses (14) used on the hemi-cylindrical roof (10), including
nine of the segments (12), is sixty-three. Further, in this example, the holding base strip (16) can
be made of an acrylic sheet of 25mm width and 640 mm length attached to the bottom-most
acrylic sheet with help of solvent cement. The foregoing description shall explain further
embodiments of the solar heat collector and the hemi-cylindrical roof (10).
Figure 2 illustrates a system (100) including a solar heat collector (110) including a closed hemicylindrical
roof (10) (shown in Figure 1), in accordance with an embodiment of the present
invention. The system (100) includes the closed semi-cylindrical roof (10) including the
segments 12 (Figure 1) where each of the segments (12) includes a plurality of light
concentrating lenses (14) (Figure 1). Further, the system (100) includes covers (18), fluid pipes
(20, 24, 30), hot water tank (HWT) (22), cold water tank (CWT) (26), vent pipe (34), and a
temperature display (28).
According to an embodiment of the present invention, the hemi-cylindrical roof (10) is further
attached to the receiver base box (not shown) at both lateral ends thereof via covers (18). Further,
one of the covers (18) as seen in the Figure 2 is in the form of segment of an arc, with the curved
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surface of the arc being cut along multiple tangential lines for supporting the semi-cylindrical
roof (10). According to one implementation, the covers (18) are made of individual stripes cut
from 8 mm thick acrylic sheet cut along the 9 tangent lines (considering nine rows of segments
(12) in the above example) of 115 mm length of a semi-circle of 630 mm diameter. The center of
two base edges is 20° apart from semi circle’s center. At the outer side of end covers (18),
handles may be attached for easy handling of the solar heat collector.
According to an embodiment of the present invention, the receiver box of the solar heat collector
(110) comprises an absorbing plate configured to absorb at least a part of the concentrated light
received by the concentrating lenses (14). In one implementation, the absorbing plate comprises
of a copper plate having thickness of 0.4 mm and is painted matte black color so as to maximize
the heat absorption. Further, the absorbing plate comprises hemi-cylindrical grooves for
accommodating fluid carrying tubes therein. Figure 3 illustrates a schematic diagram of a flatplate
receiver (120) in accordance with the embodiment of the present invention, which receives
the absorbing plate (130). The fluid carrying tubes (36) are fitted upon the absorbing plate (130)
to facilitate flow of fluid which receives the heat absorbed by the copper plate of the solar heat
collector (110). In one implementation, riser tubes (the vertical fluid carrying tubes 36) and
headers (the horizontal carrying tubes) are used as means of fluid carrying tubes (36) arranged as
shown in Figure 3. The riser tubes and headers used herein are copper tubes. According to an
implementation, copper tube of 6.35 mm as outer diameter and 5.85 mm internal diameter are
used as riser tubes. As seen in Figure 3, there are total 16 riser tubes, 6 are left 6 are at right of
the center focus line. The spacing in between the risers to left and right sides is 42 mm from
center to center. Further, copper tube of 15.85 mm as outer diameter and 14.85 mm internal
diameter are used lower header and upper header. Further, one of the ends of the lower header is
used as an inlet (37A) to receive warm water from a hot water tank (HWT) (22) as shown in
Figure 2 by means of fluid pipe (20). And one of the ends of the upper header is used as an outlet
(37B) to transfer the heated water to the HWT (22) as shown in Figure 2 by means of fluid pipe
(30). By way of an example, Figure 4 illustrates a photographic view of the flat-plate receiver
(120) which also depicts the fluid carrying pipes (36) as riser tubes, central risers, lower header
and upper header. Further, Figure 4 also depicts an inlet pipe at the inlet (37A) and an outlet pipe
at the outlet (37B). The inlet pipe and the outlet pipe shall be explained with respect to the fluid
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pipes (20, 30) with respect to Figure 2 in the foregoing description. Further, Figure 4 also depicts
the absorbing plate (130) as a part of the base box, i.e., the receiver base box (38).
Further, for an arrangement of the riser tubes and headers as shown in Figure 3 and 4, having the
dimensions as described in the examples used above with respect to Figure 3, the outer covering
of the receiver base box can be made using a stainless steel sheet of thickness 1 mm. By way of
an example, Figure 5 illustrates a blueprint of the dimensions of the stainless sheet for the outer
receiver base box.
Referring back to Figure 2, the system (100) comprises of a cold water supply source (26) and a
hot water receiving unit (22). The HWT (22) is in fluid communication with the fluid carrying
tubes (36) of the absorbing plate i.e. the flat-plate receiver (120) (refer to Figure 3) via fluid
pipes (20) and (30). The fluid pipe (20) carries warm water from the HWT (22) to the solar heat
collector (110) and the fluid pipe (30) carries hot water from the solar heat collector to the HWT
(22) based on thermo-siphoning principle. Herein, the fluid pipe (20) carries warm water by
virtue of being an interconnection pipe between the HWT and the solar heat collector (110).
Further, the fluid pipe (30) carries hot water which is supplied from the outlet (37B) of the fluid
carrying tubes (30) fitted thereupon the absorbing plate (130), as explained with respect to Figure
3.
Figure 6 illustrates a schematic diagram of the interconnection of the fluid carrying pipes (36),
fitted upon the absorbing plate (130) in the flat plate receiver (120), with the HWT (22) via the
fluid pipes (20, 30), and further the interconnection between the HWT (22) and the CWT (26)
via the fluid pipe (24). The CWT (26) has an inlet (24A) to receive fresh water supply and the
(HWT) has an outlet (32) for the hot water stored in the HWT (22). Further, the HWT (22) is
placed at a first height with respect to the ground level at which the solar heat collector (110) is
placed. The HWT (22) stores hot water which is gradually heated due to the heating achieved by
the solar heat collector where the heat is transferred by means of the fluid pipe (30) to the HWT.
For heat venting purposes, a vent pipe (34) is provided on the HWT. Further, a hot water outlet
(32) is also provided on the HWT. According to one implementation, the HWT (22) is a 5 liters
capacity tank made of stainless steel, placed at height of 300 mm from the ground level at which
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the solar heat collector (110) is placed. In one implementation, the HWT (22) is well insulated by
the 25 mm thick glass wool layer from all sides.
To maintain the water supply at the HWT (22), the HWT (22) is in fluid communication with a
cold water tank (CWT) (26) which is placed at a second height with respect to the ground level,
the solar heat collector (110) being placed at the ground level. The second height is higher than
the first height to create necessary pressure head for the flow of fluid to the HWT (22) and
further to the solar heat collector (110). Further, in one implementation, the CWT (26) is placed
at a height of 850 mm from the ground level and the the HWT (26) is placed at a height of 300
mm from the ground level, the solar heat collector (110) being placed at the ground level.
According to one further implementation, the HWT (22) is a 5 liters capacity tank made of
stainless steel and the CWT (26) is a 20 liters capacity tank made of stainless steel to maintain
the water level in the HWT (22).
Further, as shown in Figure 2, a temperature display (28) may be provided to indicate the
temperature achieved by heating of the fluid through the solar heat collector (110) in accordance
with the present invention. In one example, the temperature display (28) is a digital temperature
indicator having a resolution of 0.1 and is connected to RTD PT100 thermocouples.
Experimental Results
The closed-loop hemi-cylindrical solar heat collector (110) according to the embodiment as
shown in Figure 2 was tested for water heating. Different parts of the solar heat collector (110)
such as the hemi-cylindrical roof (20) and the plurality of light concentrating lenses (14)
disposed on the hemi-cylindrical roof (20) as per the details of Figure 1, the receiver base box
including the copper plate (130) as per the details of Figure 3, 4 and 5, and the arrangement of
the cold water supply (26) and the hot water tank (22) as per the details of Figures 2 and 6, were
employed in the test.
Different parameters were measured during experiments by using measuring devices and
instruments. Temperature of water was measured with the help of RTD PT100 thermocouples
which was connected with a digital temperature indicator having a resolution of 0.1, for example
the temperature display (28) shown in Figure 2. Dry bulb temperature and wet bulb temperature
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of ambient air was measured with the help of sling Psychrometer. The solar radiation intensity
was measured during the day time with a Pyranometer-Model CM11, of Kipp and Zonen,
Holland.
System Operation:
The stepwise experimental procedure which is followed during the experiment is as follows:
Step 1: All the components of the closed hemi-cylindrical (CHC) solar heat collector (110) are
gathered and assembled together.
Step 2: The arrangement is placed at the open place on clean sky days at a location with
geographical coordinates 29° 58' 10.25''N and 76°52'41.81''E.
Step 3: Cleaning of the outer surface of CHC solar heat collector (110) is done to remove the
dust particles and moisture.
Step 4: The cold water supply tank (26) is filled with fresh and clean water and is placed at the
height of 850 mm from the collector (110) to create necessary pressure head caused for the flow
of working fluid through hot water tank (22) and copper pipes (36) and headers (36).
Step 5: The collector (110) is tilted at efficient angle to absorb maximum radiation.
Step 6: The collector (110) is exposed to the sun 30 minute before start of the experiment.
Step 7: While the water is passing through the collector (110) at the ambient temperature, inlet
temperature and outlet temperature of water are noted down.
Step 8: There should be no bend in the fluid pipes (20, 30) from hot water tank (22) to the
collector (110) and the collector (110) to the hot water tank (22) for proper flow by thermosyphon
principle.
Step 9: The readings are taken after every hour and are tabulated.
Step 10: The experimental procedure is repeated for the next day.
Analysis of experimental data:
The useful heat collected by the thermic fluid during time interval Δt is given by
Qu = m Cp (To-Ti) Δt (1)
Where, Qu is the useful heat gain during time interval Δ􀝐 (􀜬􀝋􀝑􀝈􀝁􀝏)
Cp is the specific heat of the fluid (J/Kg °C)
To is the inlet temperature of the fluid (°C)
Ti is the outlet temperature of the fluid (°C)
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m is the mass flow in Kg/sec
The Thermal efficiency of the CHC collector system is evaluated using following equation
η= 􀭕􀭳
􀭅􀭮􀭍 (2)
η= 􀭫 􀭇􀭮 􁈺􀭘􀭭􀬿􀭘􀭧􁈻 􀭼􀭲
􀭅􀭮􀭍 (3)
Where,
Qu is the heat gain from the collector during time interval of one hour.
Ap is the aperture area of the convex lenses which focuses at particular time and
I is the intensity of solar radiation received during time interval of one hour.
Aperture area for a convex lens Apl = 􀰗
􀬸 􀝀􀬶
= 􀰗
􀬸 75􀬶 = 4417.86mm2 = 0.004418m2 (4)
Aperture area for single row (7 lens) Apr = 7×0.004418 = 0.031 m2
Aperture area for four row of lenses Apr4 = 4×0.031 = 0.1237 m2
Aperture area for five row of lenses Apr5 = 5×0.031= 0.1546 m2
Hourly Thermal Efficiency
To find out the thermal efficiency, time interval has been taken as one hour.
Mass of water m = 5 kg/hr = 0.001389 kg/sec
Specific heat of water Cp = 4187 J/Kg K
Aperture area (5 Rows of Lenses) Ap = 0.1546 m2
Concentration Ratio (Cc) = 􀭟􀭮􀭣􀭰􀭲􀭳􀭰􀭣 􀭟􀭰􀭣􀭟 􀭭􀭤 􀭪􀭣􀭬􀭱
􀯖􀯢􀯡􀯖􀯘􀯡􀯧􀯥􀯔􀯧􀯘􀯗 􀯔􀯥􀯘􀯔 􀯢􀯙 􀯟􀯘􀯡􀯦􀯘
Cc =
􀴏
􀰰􀬻􀬹􀰮
􀴏
􀰰􀬵􀬴􀰮 = 56.25 (5)
Result and Discussions
The investigation conducted as per the operation described above was performed for three days
from 8th of July to 10th of July 2017 from 8:00 AM to 6:00 PM. During the experiments on all
the three days, it was found that the temperature of absorber plate and water rose up till 3:00 PM
even though the solar intensity falls after solar noon. Also, the highest temperature of 94 oC of
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water at 3:00 PM on 10th July 2017 was recorded with the help of the closed hemi-cylindrical
collector, i.e., the solar heat collector (110), while the temperature of absorber plate (130) was
recorded as 106 °C when the solar intensity was 886 W/m2, which was recorded maximum on
that day at solar noon. On the Same day the maximum hourly Thermal Efficiency was calculated
as 68.70% during 1:00 PM and 2:00 PM. The details of the investigated results are as follows:
(a) On 8th July 2017, the maximum temperature attained at 3:00 PM was 85°C when highest
solar intensity of the day was 910 W/m2 at 12:00 PM. The highest temperature of
absorbing plate at 3:00 PM was 100°C. After the solar noon, the solar intensity started
decreasing but the rise in temperature continued up till 3:00 PM. The temperature of both
water and absorbing plate started decreasing as shown in Figure 7.
(b) The maximum hourly thermal efficiency of 65.5% was found during 1:00 PM and 2:00
PM, also the highest temperature rise was observed during the same period. After 2:00
PM the efficiency started decreasing but temperature rose up to 3:00 PM as shown in
Figure 8.
(c) In a second experiment conducted next day, the maximum temperature gained on 9th July
2017 was 92 °C at 3:00 PM, while the surface temperature of 105 °C was recorded with
highest solar intensity of the day of 900 W/m2 as shown in Figure 9. The maximum
efficiency of 64.5% was observed on 9th July 2017 during 1:00PM and 2:00 PM. The
efficiency rose with time from 9:00 AM to 2:00 PM then after it started decreasing as
shown in Figure 10.
(d) In a third experiment conducted on a third day, it was observed that the maximum
temperature of 94 °C was attained at 3:00 PM on 10th July 2017, while highest solar
intensity of the day was of 886 W/m2 recorded at 12:00 PM. The highest temperature of
absorbing plate was 106 °C at 3:00 PM. After the solar noon the intensity started
decreasing but temperature rose continuously up till 3:00 PM as shown in Figure 11.
(e) The maximum efficiency of 68.7% was observed on 10th July 2017 during 1:00 PM and
2:00 PM. The efficiency rose with time from 9:00 AM to 2:00 PM, then after it started
decreasing. The temperature differences increased up to 2:00 PM. After 3:00 PM
temperature difference changed from positive to negative as shown in Figure 12.
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The concentrated solar heat collector (110) also referred to as solar power collector, described in
the above embodiments can be used in a number of applications of water and air heating like
solar air conditioning, solar cooking and even solar power generation etc. The solar heat
collector (110) enhances the heat collection capability of flat plate collector by replacing the
glazing with array of convex lenses in the form of segmental hemi cylindrical roof (10). The
proposed setup eliminates the solar tracking requirement for concentrated solar collector,
achieving high thermal efficiency by reducing the convection losses and heating by Green House
effect due to closed environment.
While specific language has been used to describe the disclosure, any limitations arising on
account of the same are not intended. As would be apparent to a person in the art, various
working modifications may be made to the method in order to implement the inventive concept
as taught herein.
The drawings and the forgoing description give examples of embodiments. Those skilled in the
art will appreciate that one or more of the described elements may well be combined into a single
functional element. Alternatively, certain elements may be split into multiple functional
elements. Elements from one embodiment may be added to another embodiment. The scope of
embodiments is by no means limited by these specific examples. Numerous variations, whether
explicitly given in the specification or not, such as differences in structure, dimension, and use of
material, are possible. The scope of embodiments is at least as broad as given by the following
claims.

We Claim:
1. A solar heat collector comprising:
a receiver base box;
a hemi-cylindrical roof fixed on the receiver box; and
plurality of light concentrating lenses disposed on the hemi-cylindrical roof.
2. The solar heat collector as claimed in claim 1, wherein hemi-cylindrical roof is
formed of a plurality of segments joined together, with each segment being formed of
an acrylic sheet strip having light transmittance of about 92% and refractive index of
about 1.49.
3. The solar heat collector as claimed in claim 2, wherein each strip is provided with
holes cut along of a length direction for accommodating the plurality of light
concentrating lenses.
4. The solar heat collector as claimed in claim 1, wherein the plurality of light
concentrating lenses are arranged in two-dimensional matrix form on the hemicylindrical
roof.
5. The solar heat collector as claimed in claim 1, wherein the hemi-cylindrical roof is
further attached to the receiver base box at both lateral ends thereof via covers.
6. The solar heat collector as claimed in claim 3, wherein the cover is in form of
segment of an arc, with curved surface of the arc being cut along multiple tangential
lines for supporting the hemi-cylindrical roof.
7. The solar heat collector as claimed in claim 1, wherein the receiver box comprises an
absorbing plate configured to absorb at least a part of the concentrated light.
8. The solar heat collector as claimed in claim 1, wherein the absorbing plate comprises
a copper plate having thickness of 0.4 mm and painted matte black color, the copper
plate comprising hemi-cylindrical grooves for accommodating fluid carrying tubes
therein.
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9. The solar heat collector as claimed in claim 8, further comprising a cold water supply
source and a hot water receiving unit being in fluid communication with the fluid
carrying tubes.