AU2021105192A4 - A thermal solar energy concentrator system - Google Patents

Abstract

The present invention relates to a solar energy harnessing system. More particularly, the present invention relates to a thermal solar energy concentrator system with enhanced efficiency and reduced convective heat losses. The thermal solar energy concentrator system 5 comprises a parabolic Scheffler reflector having a focal point, and configured for focusing solar rays, a convex conical receiver disposed in proximity of the focal point of the parabolic Scheffler reflector, and configured to receive the focused solar rays from the parabolic Scheffler reflector, a water pipe disposed in thermal communication with the convex conical receiver, and configured to facilitate flow and heating of water therethrough, wherein the 10 convex conical receiver is tilted at a predetermined angle with respect to the horizontal axis of the convex conical receiver thereby facilitating increase in focal area which increases heat transfer thereby enhancing thermal efficiency of the system. 1 1/4 102 100- 104 102 112 106 FIG. 1

Description

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TITLE A THERMAL SOLAR ENERGY CONCENTRATOR SYSTEM FIELD OF THE INVENTION

The present invention relates to a solar energy harnessing system. More particularly, the

present invention relates to a thermal solar energy concentrator system with enhanced

efficiency and reduced convective heat losses.

BACKGROUND OF THE INVENTION

In the contemporary world, demand for energy is ever-increasing. At present, for powering

various machines, vehicles, and devices, fossil fuels are employed, which have had led to

harmful effects on climate along with pollution.

It is therefore desired to have sources of energy which avoids the harmful effect on climate

and pollution. That is, there is need of clean energy. One such source of clean energy is solar

energy.

Attempts have been made to harness solar energy. There are two methods for harnessing the

solar energy. The first one is to convert light or radiation in visible region to electricity, or

photovoltaic, and the second one is to convert thermal energy contained in the solar

radiations to electricity or any other useful form.

It is observed that the thermal energy conversion is most useful for heating and cooling

applications pertaining to the industrial processes. More specifically, concentrated solar power technology (CSPT) is being developed and particularly Scheffler fixed focus concentrator under is one of the most promising type solar thermal energy convertor.

In countries like India where solar energy is amply available, there is a vast potential for

solar power trapping. CSPT is comparatively new technology and is progressively used for

most of the industrial heat applications to reduce C02 emissions.

In a typical solar power concentrator system, a cylindrical shaped receiver is commonly used

with a Scheffler collector system. Receivers with other shape such as the conical shape

receivers are also employed instead of the cylindrical shape.

For a given type of solar power concentrator system, the thermal efficiency thereof is

influenced by parameters such as receiver shape, tilt angle, wind speed, and convection heat

losses etc. Hence, improvement in the thermal efficiency of the solar power concentrator

system can be achieved by reducing the convective heat losses.

Numerous attempts have been made, both experimental and numerical, for improving

convective losses in downward-facing cylindrical cavity receivers and modified conical

cavity receivers by considering the wind direction, wind speed, receiver configuration, and

receiver orientation.

Among the different bottom reflective shapes, the conical cavity receiver with the bottom

reflective cone has been found to exhibit higher optical performance but more convective

losses. So, there is a need to improve the efficiency by reducing convective heat losses.

In the known art, there have been attempts to improve the efficiency by reducing the

convective heat losses.

The US patent no. 4,030,477 titled solar collector with conical elements discloses a device

for collecting radiant energy with a conical surface to convergently reflect rays toward an

elongate energy absorbing structure which is disposed along a central focal axis. The conical

surface has a relatively high reflectivity (rho) coefficient while the outer surface of the

energy absorbing structure has a relatively high absorptivity coefficient and also is formed

of a material having a relatively high thermal conductivity (k) for efficiently transferring

thermal energy by convection to a heat exchange fluid. The energy absorbing structure

comprises a hollow tube which is coiled in a helix about the focal axis, with a transparent

cover enclosing the helix.

The US patent no. 9,383,122 B2, titled spiral concentrating collector with moving receiver

discloses an improved solar energy concentrating system and to a preferred way of moving

the receiver, along a curvilinear path above the mirror surface to the optimal location where

the instantaneous concentration of reflected rays is the largest. The system comprises a fixed,

trough concentrating collector formed with a concave curvature, shaped as a section of a

spiral, oriented along the East-West axis, with a movable receiver, inclined facing South and

capable of adjusting the angle of inclination periodically, preferably twice a year. The

invention is capable of capturing more solar energy, on a more constant basis throughout the

year and at a lower cost than the preferred, state-of the-art, trough parabolic concentrating

collectors oriented along the North South axis.

The US patent no. 9,297,554 B2, titled Cavity receivers for parabolic solar troughs discloses

a linear solar receiver comprising a solar radiation absorbing element having an outer surface

configured to circumscribe an interior volume, said interior volume designed to contain a

heat transfer medium, said solar radiation absorbing element designed to absorb an incident

flux of solar radiation and transfer an absorbed flux of energy to said heat transfer medium,

said heat transfer medium designed to receive and transport at least a portion of said absorbed

flux of energy, said heat transfer medium when transporting at least a portion of said

absorbed flux of energy being primarily in a fluid phase; In this way the conical cavity

receiver maximizes thermal efficiency and an optical efficiency.

The Chines Patent Application no 103090555 A titled wedge structure cavity type solar

energy discloses a wedge structure cavity type solar energy receiver and belongs to the

technical field of solar energy high temperature heat utilization. The wedge structure cavity

type solar energy receiver is formed by combination of a plurality of innovative designs

namely a cylindrical cavity, a wedge type absorber and a cone-shaped reflector. The wedge

structure cavity type solar energy receiver can operate in a disc type parabolic mirror solar

energy system with 10000 of concentration ratio, achieve 66 kilowatts of heat exchanging

amount in a limited heat exchanging space, enable heating medium gas to reach 11000 C of

outlet temperature, and have technical feathers namely compactness, high efficiency and low

flow resistance.

The Chinese Patent Application no. 103344048 A titled narrowing tube bundle structural

cavity solar receiver discloses a narrowing tube bundle structural-cavity solar receiver, and

belongs to the field of solar high-temperature heat utilization. A narrowing tube bundle heat absorber designed according to a light collection rule makes the receiver uniformly receive solar light rays, the difficult problem that energy in an existing receiver is not uniformly distributed is solved, an air channel structure formed by a truncated conical outer shell, cavity sealing glass, and a truncated conical inner cavity enables working media to flow uniformly in the receiver, accordingly energy flow is well matched, heat collection performance is well achieved. The receiver has the advantages of being compact, efficient and low in flow resistance, and has a significant meaning for improving competitiveness of a solar high-temperature heat utilization system, and making the solar receiver be high temperature and efficient.

However, the known solar concentrator systems exhibit relatively high convective losses.

Thus, there exists an acute need to improve the efficiency by reducing convective heat losses.

OBJECTS OF THE INVENTION

The some of the objects of the present invention of which at least one object is achieved by

the present invention include:

An object of the present invention is to provide a thermal solar energy concentrator system

which over comes one or more drawbacks associated with the conventional systems;

Another object of the present invention is to provide a thermal solar energy concentrator

system with enhanced efficiency; and

Still another object of the present invention is to provide a thermal solar energy concentrator

system with reduced convective heat losses.

SUMMARY OF THE INVENTION

The present invention relates to a thermal solar energy concentrator system. The thermal

solar energy concentrator system comprising a parabolic Scheffler reflector having a focal

point, and configured for focusing solar rays, a convex conical receiver disposed in

proximity of the focal point of the parabolic Scheffler reflector, and configured to receive

the focused solar rays from the parabolic Scheffler reflector, a water pipe disposed in thermal

communication with the convex conical receiver, and configured to facilitate flow and

heating of water therethrough, wherein the convex conical receiver is tilted at a

predetermined angle with respect to the horizontal axis of the convex conical receiver

thereby facilitating increase in focal area which increases heat transfer thereby enhancing

thermal efficiency of the system.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a schematic diagram of a thermal solar energy concentrator in accordance

with the embodiments of the present invention;

FIG. 2 illustrates a schematic diagram of a top view of a convex conical receiver with a rim

disposed there around;

FIG. 3 illustrates a schematic diagram of a side view of the convex conical receiver with the

rim disposed there around of FIG. 2; and

FIG. 4 illustrates a schematic diagram of an isometric view of the convex conical receiver

with the rim disposed there around of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a solar energy harnessing system and particularly to a

thermal solar energy concentrator system with enhanced efficiency and reduced convective

heatlosses.

The solar energy concentrator system of the present invention is now described with

reference to the accompanying drawings wherein FIG. 1 illustrates a schematic diagram of

a thermal solar energy concentrator in accordance with the embodiments of the present

invention, FIG. 2 illustrates a schematic diagram of a top view of a convex conical receiver

with a rim disposed there around, FIG. 3 illustrates a schematic diagram of a side view of

the convex conical receiver with the rim disposed there around of FIG. 2, and FIG. 4

illustrates a schematic diagram of an isometric view of the convex conical receiver with the

rim disposed there around of FIG. 2.

Existing conventional receivers have cylindrical, spherical and conical cavity shapes. The

receiver of the present invention differs from the conventional receivers in that the receiver

of the present invention is convex conical in shape with 45 inclination, which the inventors

of the present invention have observed to increase radiation heat transfer and increase the

focal area of heat transfer.

Further, in contrast with the existing conventional thermal solar energy concentrators, a rim

is attached on the circumference of the convex conical receiver to prevent airflow and hence

to reduce the convective heat losses.

The above mentioned two features have been observed to increase the overall thermal

efficiency of the system.

The present invention is now described with reference to FIG. 1 through FIG. 4. More

specifically, the thermal solar energy concentrator system (100) of the present invention

comprises a parabolic Scheffler reflector (102) having a focal point (102f), and configured

for focusing solar rays (104), a convex conical receiver (106) disposed in proximity of the

focal point (102f) of the parabolic Scheffler reflector (102), and configured to receive the

focused solar rays (104) from the parabolic Scheffler reflector (102), a water pipe (108)

disposed in thermal communication with the convex conical receiver (106), and configured

to facilitate flow and heating of water therethrough, wherein the convex conical receiver

(106) is tilted at a predetermined angle with respect to the horizontal axis of the convex

conical receiver (106) thereby facilitating increase in focal area (112) which increases heat

transfer thereby enhancing thermal efficiency of the system.

In accordance with one embodiment of the present invention, the predetermined angle is 45°.

In accordance with one embodiment of the present invention, a rim (110) disposed around the convex conical receiver (106), which is configured to prevent air flow in and around the convex conical receiver (106) thereby reducing convection losses and enhancing thermal efficiency of the system.

In accordance with one embodiment of the present invention, the convex conical receiver (106) includes a rim, wherein both the convex conical receiver (106) and the rim (110) are titled at an angle of 45°.

In accordance with one embodiment of the present invention, the focal area (112) is elliptical in shape.

The working of the system (100) is as follows:

The solar rays (104) from parabolic Scheffler reflector (102), are focused on the convex

conical receiver (106) (see FIG. 1). Water is passed through a water pipe (108) inlet, wherein

the water is allowed to get heated by the heat from the solar rays which are concentrated in

and around the focal area (112) to generate steam which is received at the outlet of the water

pipe (108), the steam being used for process applications.

The convex conical receiver (106) is tilted 45° to the horizontal axis of the receiver (106) so

that its focal area (112) is increased which leads to more heat transfer to obtain more thermal

efficiency. Also, the rim (110) around the receiver (106) prevents the air flow so that the

convection heat losses due to surrounding air, are reduced which leads to increase the

thermal efficiency. FIG. 2 illustrates a schematic diagram of a top view of a convex conical

receiver with a rim disposed there around, wherein the convex conical receiver (106) with

the rim (110) being inclined at 45°. The enlarged focal area (112) is in elliptical shape. The

enlarged focal area (112) of the conical convex receiver (106) with the rim (110) increases

the heat transfer and hence increases the thermal efficiency.

FIG. 3 illustrates a schematic diagram of a side view of the convex conical receiver with the

rim disposed there around of FIG. 2; and FIG. 4 illustrates a schematic diagram of an

isometric view of the convex conical receiver with the rim disposed there around of FIG. 2.

In accordance with one embodiment of the present invention, the convex conical receiver

(106) have a diameter of 450 mm and a length of 50 mm length. To maintain optimum

volume of 8 liter, the optimum axial length of the conical receiver is found to be 150 mm.

The construction material is mild steel. The frontal area of the receiver is black coated to

improve absorptive power to 91%. The receiver has a tilting arrangement equipped with an

inclinometer to measure the tilting angle and set it as 45°.

The conical receiver with 450 mm diameter, length of 50 mm and the height of 150 mm with

450 tilting arrangement shows improved efficiency in Big Scheffler dish size of 9.7 m2 . To

minimize the convection heat losses due to surrounding air, a rim of 450 mm diameter and

150 mm length and 6 mm thick is attached on the circumference of the conical receiver and

it enormously reduces the convection heat losses. The 45° inclined convex conical receiver

with the rim on the circumference increases the overall efficiency of the solar system.

To increase the area exposed to radiation heat transfer, the convex conical receiver is

installed. To increase the more focus area of heat transfer, conical convex receiver is titled

with 45° inclination. To prevent the air flow due to surrounding air and thereby reduce the

convective heat losses, the rim is fitted around the circumference of the convex conical

receiver. The above features increase the overall thermal efficiency of the Scheffler solar

system.

Dimensions and parameters of a typical system (100) constructions in accordance with the

embodiments of the present invention are listed in the table herein below:

Sr. No. Title Specification

1 Dimensions of Scheffler reflector Model - 9.7 m2

Ap - 6.5 m=

Major Axis - 4.22 m

Minor Axis -3.08 m

Concentration ratio - 41

2 Dimensions of convex conical Diameter - 450 mm

receiver Height - 150 mm

Volume - 8 liters

3 Dimension of rim disposed around the Diameter - 450 mm

convex conical receiver Height - 150 mm

Thickness - 6 mm

4 Convex conical receiver Focal area

Without tilt With tilt

0.024 m 2 0.045 m 2

TECHNICAL ADVANTAGES

The thermal solar energy concentrator system of the present invention has the following

advantages, wherein the system

1. is simple in construction;

2. is easy to install, operate, and maintain;

3. has increased efficiency; and

4. reduced convection loses.

Claims (5)

1. A thermal solar energy concentrator system comprising:

- a parabolic Scheffler reflector having a focal point, and configured for focusing solar

rays;

- a convex conical receiver disposed in proximity of the focal point of the parabolic

Scheffler reflector, and configured to receive the focused solar rays from the

parabolic Scheffler reflector;

- a water pipe disposed in thermal communication with the convex conical receiver,

and configured to facilitate flow and heating of water therethrough;

wherein the convex conical receiver is tilted at a predetermined angle with respect to

the horizontal axis of the convex conical receiver thereby facilitating increase in focal

area which increases heat transfer thereby enhancing thermal efficiency of the

system.

2. The system as claimed in claim 1, wherein the predetermined angle is 45°.

3. The system as claimed in claim 1, further includes a rim disposed around the convex

conical receiver, which is configured to prevent air flow in and around the convex conical

receiver thereby reducing convection losses and enhancing thermal efficiency of the

system.

4. The system as claimed in claim 1, wherein the convex conical receiver includes a rim,

wherein both the convex conical receiver and the rim are titled at an angle of 45°.

5. The system as claimed in claim 1, wherein the focal area is elliptical in shape.