U.S. patent application number 12/990773 was filed with the patent office on 2011-10-27 for solar energy absorber.
This patent application is currently assigned to Electra Holdings Co., Ltd.. Invention is credited to Yuji Satoh, Takashi Yabe.
Application Number | 20110259319 12/990773 |
Document ID | / |
Family ID | 41255099 |
Filed Date | 2011-10-27 |
United States Patent
Application |
20110259319 |
Kind Code |
A1 |
Yabe; Takashi ; et
al. |
October 27, 2011 |
Solar Energy Absorber
Abstract
It aims to provide a solar heat collecting apparatus that can
efficiently collect energy from solar light. The solar heat
collecting apparatus comprises an opened container part 22 that
accumulates heat, a closed part 25 that closes the container part
22 and has an opening part 26 to let the collected solar light in,
and a light absorbing part 36 that absorbs the solar light
dispersed by passing through the opening part 26 so that it is
converted into heat.
Inventors: |
Yabe; Takashi; (Kita-ku,
JP) ; Satoh; Yuji; (Tokyo, JP) |
Assignee: |
Electra Holdings Co., Ltd.
Tokyo
JP
|
Family ID: |
41255099 |
Appl. No.: |
12/990773 |
Filed: |
April 28, 2009 |
PCT Filed: |
April 28, 2009 |
PCT NO: |
PCT/JP2009/058347 |
371 Date: |
January 24, 2011 |
Current U.S.
Class: |
126/573 ;
126/680; 126/698; 126/702; 126/709 |
Current CPC
Class: |
F24S 23/00 20180501;
Y02E 10/47 20130101; Y02E 10/44 20130101; F24S 23/31 20180501; F24S
23/12 20180501; F24S 60/30 20180501; F24S 70/60 20180501; F24S
30/40 20180501 |
Class at
Publication: |
126/573 ;
126/680; 126/709; 126/702; 126/698 |
International
Class: |
F24J 2/08 20060101
F24J002/08; F24J 2/46 20060101 F24J002/46; F24J 2/38 20060101
F24J002/38; F24J 2/02 20060101 F24J002/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2008 |
JP |
2008-120538 |
Aug 7, 2008 |
JP |
2008-203940 |
Claims
1-14. (canceled)
15. A solar heat collecting apparatus, comprising: a
heat-insulating container comprising a circumferential wall and a
bottom wall configured as a heat-insulating wall, and an upper part
closed with a heat-insulating closing member having a translucent
opening window formed therein; a light absorbing body contained
within the heat-insulating container; and a light collecting
mechanism located outside the heat-insulating container and
disposes with a focal position substantially matches with position
of the translucent opening window formed in the closing member of
the heat-insulating container, wherein, the heat-insulating
container is filled with a liquid medium to a liquid level in which
the light absorbing body within the heat-insulating container is
immersed therein, and configured such that the solar light entering
from the translucent opening window is absorbed by the light
absorbing body and transformed to heat energy for heating the
liquid medium.
16. The solar heat collecting apparatus as defined in claim 15,
wherein the translucent opening window comprises at least one
elongated slit, and the heat-insulating container is positioned
such that the lengthwise direction of the slit is directed
substantially along a movement path of the diurnal motion of the
sun.
17. The solar heat collecting apparatus defined in claim 16,
wherein the width of the slit of the opening window is dimensioned
corresponding to the diameter of the sun imaged by the light
collecting mechanism.
18. The solar heat collecting apparatus as defined in claim 16,
wherein the width of the slit of the opening window is
substantially five times as large as the diameter of the sun imaged
by the light collecting mechanism.
19. The solar heat collecting apparatus as defined in claim 16,
wherein the lengthwise direction of the slit of the opening window
is substantially east-west direction.
20. The solar heat collecting apparatus as defined in claim 16,
wherein the light collecting mechanism comprises a plurality of
lenses arranged to collect the solar light at different positions
in the lengthwise direction of the slit of the opening window.
21. The solar heat collecting apparatus as defined in claim 20,
wherein a plurality of slits are formed in parallel and spaced from
each other in the width direction, and the light collecting
mechanism comprises a plurality of lenses provided corresponding to
each of the slits.
22. The solar heat collecting apparatus as defined in claim 16,
wherein a tracking mechanism is provided to track the annual motion
of the sun to change at least one of an orientation of an optical
axis of the light collecting mechanism or an orientation of the
opening window within a plane perpendicular to the lengthwise
direction of the slit.
23. The solar heat collecting apparatus as defined in claim 15,
wherein the light collecting mechanism is at least one Fresnel
lens.
24. The solar heat collecting apparatus as defined in claim 23,
wherein one of the sides of the Fresnel lens oriented to the
heat-insulating container is curved to form a concave.
25. The solar heat collecting apparatus as defined in claim 15,
wherein the opening window formed in the closing member of the
heat-insulating container is arranged at a position reentrant than
other portion of the closing member and immersed in the medium with
the heat-insulating container.
26. The solar heat collecting apparatus as defined in claim 15,
wherein the translucent opening window of the closing member is
mounted with a light guide including an upper part having an
entrance and a lower part having an exit provided with an inner
surface formed as reflecting surface, wherein the upper part of the
light guide has a cross-section gradually widening from the
entrance part towards the lower part, and the lower part has a
cross-section gradually narrowing towards the exit.
27. The solar heat collecting apparatus as defined in claim 16,
wherein the slit configuring the opening window is mounted with an
elongated light guide which an upper part having an entrance and a
lower part having an exit and provided with an inner surface formed
as reflection surface, wherein the upper part of the light guide
has a cross-section gradually widening from the entrance towards
the upper part, the lower part has a cross-section gradually
narrowing towards the exit, and the light guide having a shaped in
which height thereof is low at the center part in the lengthwise
direction and high at both ends.
Description
FIELD OF THE INVENTION
[0001] The present invention is related to a solar heat collecting
apparatus that collects energy from solar light.
BACKGROUND OF THE INVENTION
[0002] As we today are concerned about global warming, many studies
have been conducted for seeking a renewable energy that does not
use electricity. In particular, how to take advantage of the
abundant energy from the sun is an increasingly important issue for
the future. With the background, the heat collecting apparatus and
desalination apparatus etc. that use the solar light are the most
impending items to be realized. In order to realize these, it is
necessary to efficiently absorb the heat from the solar light and
increase the temperature of fluid etc. For example, Patent Document
1 discloses a heat collecting apparatus that is provided with one
or more heat collecting units comprising a tubular heat collector
inside which there is a path for the fluid in order to convert the
received solar light into heat and to increase the temperature of
the fluid, and a reflector plate that is partially surrounding the
heat collector in order to reflect the solar light thereto, wherein
the reflector plate is rotatably supported about the tubular heat
collector.
PRIOR ART DOCUMENT
Patent Document
[0003] Patent Document 1: JPA 2002-22283
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0004] As the above-described conventional example, a general
method for obtaining hot water from the sun is to produce a high
temperature medium by leading the solar light through transparent
glass or plastic that covers the front part of the casing so that
this light hits and heats an absorber. However, the heat loss due
to radiation and convection from the high temperature part becomes
significant as the temperature gets higher. Therefore there was a
limitation on the temperature that can be efficiently achieved by
the solar light.
[0005] The present invention is made to solve the above problem,
and the present invention aims to provide the solar heat collecting
apparatus that efficiently collects energy from solar light.
Means of Solving the Problem
[0006] In order to solve the above problem, the invention as
claimed in Claim 1 comprises an opened container part that
accumulates heat, a closed part that closes the container part and
has an opening part to let the collected solar light in, and a
light absorbing part that absorbs the solar light dispersed by
passing through the opening part so that it is converted into
heat.
[0007] The invention as claimed in Claim 2 is the solar heat
collecting apparatus as claimed in Claim 1, wherein the opening
part is provided with a slit.
[0008] The invention as claimed in Claim 3 is the solar heat
collecting apparatus as claimed in Claim 1 or Claim 2, wherein the
width of the opening part is five times greater than the diameter
of the focal point of the collected solar light.
[0009] The invention as claimed in Claim 4 is the solar heat
collecting apparatus as claimed in any one of Claim 1 to Claim 3,
wherein further a light guide is placed at the opening part and is
provided with a reflection surface that reflects the solar light
and leads it into the container part.
[0010] The invention as claimed in Claim 5 is the solar heat
collecting apparatus as claimed in Claim 4, wherein the light guide
is provided with an entrance part of the solar light and an exit
part that output the solar light into the container part, and the
light guide gradually widens from the entrance part towards the
exit part.
[0011] The invention as claimed in Claim 6 is the solar heat
collecting apparatus as claimed in Claim 5, wherein the light guide
gradually widens from the exit part towards the entrance part.
[0012] The invention as claimed in Claim 7 is the solar heat
collecting apparatus as claimed in Claim 5 or Claim 6, wherein the
entrance part of the light guide is further provided with a
spherical entrance window.
[0013] The invention as claimed in Claim 8 is the solar heat
collecting apparatus as claimed in any one of Claim 1 to Claim 7,
wherein the closed part has a depressed part, and the opening part
is formed with a transparent material that lets the solar light
through to the bottom of the depressed part.
[0014] The invention as claimed in Claim 9 is the solar heat
collecting apparatus as claimed in any one of Claim 1 to Claim 8,
further comprising a light collecting means for collecting the
solar light.
[0015] The invention as claimed in Claim 10 is the solar heat
collecting apparatus as claimed in Claim 9, wherein the light
collecting means is a Fresnel lens that curves towards the opening
part to form a depression.
[0016] The invention as claimed in Claim 11 is the solar heat
collecting apparatus as claimed in any one of Claim 1 to Claim 10,
further comprising a tracking means for tracking the sun in
accordance with the movement of the sun.
[0017] The invention as claimed in Claim 12 is the solar heat
collecting apparatus as claimed in Claim 11, wherein the tracking
means moves the light collecting means with reference to the
container part.
[0018] The invention as claimed in Claim 13 is the solar heat
collecting apparatus as claimed in Claim 10 or Claim 11, wherein
the tracking means is provided outside the opening part and has a
rotation axis to rotate the light collecting means, and the
entrance part of the light guide is positioned on the rotation
axis.
[0019] The invention as claimed in Claim 14 is the solar heat
collecting apparatus as claimed in any one of Claim 11 to Claim 13,
wherein the tracking means moves the container part.
Advantageous Effect of the Invention
[0020] According to the present invention, by comprising the opened
container part that accumulates heat, the closed part that closes
the container part and has an opening part to let the collected
solar light in, and the light absorbing part that absorbs the solar
light dispersed by passing through the opening part so that it is
converted into heat; the collected solar light enters the container
part from the opening part opened at the closed part, thus the
solar light can easily get into the container part and the heat
generated from the light absorbing part that absorbed the solar
light dispersed from the focal point is less likely to escape from
the container part, allowing to provide the solar heat collecting
apparatus that can effectively collect energy from solar light with
a little heat loss.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the first embodiment according to the present
invention.
[0022] FIG. 2 shows a schematic diagram that illustrates the
principle of the solar heat collecting in the solar heat collecting
apparatus of FIG. 1.
[0023] FIG. 3 shows a pattern diagram that illustrates a schematic
configuration example of the conventional solar heat collecting
apparatus.
[0024] FIG. 4 shows a diagram that indicates the radiant heat loss
and the amount of heated water for temperatures.
[0025] FIG. 5 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the second embodiment according to the present
invention.
[0026] FIG. 6 shows a schematic diagram that illustrates a
schematic configuration example of the first alternative example of
the solar heat collecting apparatus of FIG. 5.
[0027] FIG. 7 shows a schematic diagram that illustrates a
schematic configuration example of the second alternative example
of the solar heat collecting apparatus of FIG. 5.
[0028] FIG. 8 shows a schematic diagram that illustrates a
schematic configuration example of the third alternative example of
the solar heat collecting apparatus of FIG. 5.
[0029] FIG. 9 shows a schematic diagram that illustrates a
schematic configuration example of the fourth alternative example
of the solar heat collecting apparatus of FIG. 5.
[0030] FIG. 10 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the third embodiment according to the present
invention.
[0031] FIG. 11 shows a schematic diagram that illustrates an
example of the tracking means of the solar heat collecting
apparatus of FIG. 10.
[0032] FIG. 12 shows a schematic diagram that illustrates another
example of the tracking means of FIG. 11.
[0033] FIG. 13 shows a schematic diagram that illustrates a
schematic configuration example of an alternative example of the
solar heat collecting apparatus of FIG. 10.
[0034] FIG. 14 shows a diagram that illustrates an example of the
temperature time characteristic wherein the heat of the solar light
is collected into water by using the solar heat collecting
apparatus of FIG. 10.
[0035] FIG. 15 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the fourth embodiment according to the present
invention.
[0036] FIG. 16 shows a schematic diagram that illustrates an
example of the optical path in the light guide of the solar heat
collecting apparatus of FIG. 15.
[0037] FIG. 17 shows a schematic diagram that illustrates an
example of the optical path in the light guide of a comparative
example.
[0038] FIG. 18 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the fifth embodiment according to the present
invention.
[0039] FIG. 19 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the sixth embodiment according to the present
invention.
[0040] FIG. 20 shows a schematic diagram that illustrates an
example of the tracking means of the solar heat collecting
apparatus of FIG. 19.
[0041] FIG. 21 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the seventh embodiment according to the present
invention.
DESCRIPTION OF EMBODIMENTS
[0042] With reference to the drawings, the embodiments of the
present invention are described hereinafter.
Embodiment 1
[0043] First, with Reference to the Drawings, the Schematic
Configuration and Functions of the solar heat collecting apparatus
regarding the first embodiment according to the present invention
is described. Although the drawings are used for describing the
present invention which solves the above-described problem, the
present invention shall not be limited to the embodiment
illustrated in the drawings.
[0044] FIG. 1 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the first embodiment according to the present
invention.
[0045] As shown in FIG. 1, the solar heat collecting apparatus 1
comprises a Fresnel lens 10 that collects the solar light S, a
heat-insulated water tank 20 that has an opened upper part 20a and
accepts the solar light Sf that is collected by the Fresnel lens 10
to accumulate the heat of the solar light, a visor 25 that is an
example of the closed part that closes the upper part 20a of the
heat-insulated water tank 20 and has the opening part 26 for
letting the collected solar light Sf in, and a light absorber 30
that is installed inside the heat-insulated water tank 20 and
absorbs the solar light dispersed by passing through the opening
part 26 so that it is converted into heat.
[0046] The Fresnel lens 10 is made of plastic and has a concentric
groove in one side. The Fresnel lens 10 is supported by four
supporting members 15 installed on the heat-insulated water tank 20
so that the focal point can come close to the surface of the
heat-insulated water tank 20. The Fresnel lens 10 that is supported
by the columns (supporting members 15) is placed at the upper part
of the box (heat-insulated water tank 20). As described above, the
Fresnel lens 10 is an example of the light collecting means for
collecting the solar light, and has a function as an apparatus to
collect the solar light. This Fresnel lens 10 sets the opening part
26 in the top surface of the box (heat-insulated water tank 20) as
the focal point and narrows the solar light down small at this
point. The solar heat collecting apparatus 1 is configured so that
the light that has passed through the focal point is re-dispersed
to heat the inside of the box.
[0047] Next, the heat-insulated water tank 20 has a shape of
rectangular parallelepiped, and the surface on the side that the
solar light S enters forms the opened upper part 20a. The side and
the lower part of the heat-insulated water tank 20 has heat
insulating properties and prevents the heat accumulated inside the
heat-insulated water tank 20 from dissipating. The heat-insulated
water tank 20 has water W that is an example of the medium or
liquid as a heated object at the bottom of the inside. The water W
becomes a high temperature medium due to the light absorber 30 that
has absorbed the solar light. The heat-insulated water tank 20 is
an example of the opened container part that accumulates heat. The
closed container is formed by the container part and the closed
part. Instead of water W, molten salt may be used as the medium or
liquid.
[0048] Next, the visor 25 closes the upper part 20a of the
heat-insulated water tank 20, reflecting the radiant heat from the
inside of the heat-insulated water tank 20 and thus having the heat
insulating function. The opening part 26 is formed at the center of
the visor 25. As described above, the visor 25 is an example of the
closed part that closes the container part and has an opening part
to let the collected solar light in. The closed part such as the
visor 25 may be formed together as the upper part 20a of the
container such as the heat-insulated water tank 20. In this case,
the container part is the part other than the upper part 20a of the
container, that is, the side and the lower part of the
container.
[0049] The opening part 26 is formed near the focal point of the
Fresnel lens 10, and at the center of the upper part 20a of the
heat-insulated water tank 20 where the collected solar light
enters, that is, at the center of the visor 25. The opening part 26
is formed in a circular shape with a size through which the
collected solar light can passes, and thus the solar light
collected by the Fresnel lens 10 passes through to the inside of
the heat-insulated water tank 20. Although the opening part 26 is
not covered by a heat insulating material such as the visor 25
etc., since it is formed into a part of the surface of the visor
25, it has a function to prevent the dissipation of the heat inside
the heat-insulated water tank 20 as much as possible. As described
above, the opening part 26 is able to efficiently lead energy from
solar light to the closed space in order to create a high
temperature, while having a small opening that can suppress the
radiation from or the convective loss of the heated medium
inside.
[0050] Here, if the Fresnel lens 10 is 50 cm and the diameter of
the focal point is about 1 cm, the size of the opening part 26 is
about 5 cm in diameter. In fact, the collected solar light is not a
point as such but is called a focal point, and the light intensity
has a form of the Gaussian distribution in the radial direction. In
order to take in as much solar energy as possible, the opening part
26 is better to have a large size, however it is better to be
smaller in terms of heat loss. If the diameter of the focal point
is set to .sigma., the standard deviation of the Gaussian
distribution, the cumulative function of Gaussian distribution is
.PHI.(3.sigma.)=0.49865 and .PHI.(4.8.sigma.)=0.50000, and
therefore if the size of the opening part 26 is set to 5.sigma.,
most of the solar energy can be taken in. In comparison with the
size of the Fresnel lens 10, the size of the opening part 26 is
1/10 of the size of the lens. As described above, the width of the
opening part 26 is five times of the diameter of the focal point of
the collected solar light.
[0051] Next, the surface of the light absorber 30 has been
processed, for example, a surface with indentation or colored in
black, so that the solar light can be easily absorbed and converted
into heat. The light absorber 30 is submerged in the water W stored
in the heat-insulated water tank 20. The light absorber 30 is an
example of the light absorbing part that absorbs the solar light
dispersed by passing through the opening part 26 so that it is
converted into heat. The light absorber 30 has a function as a
heating part that re-disperses and absorbs the collected solar
light to create a high temperature medium. As shown in FIG. 1,
although a plurality of light absorbers 30 may be aligned at the
bottom of the heat-insulated water tank 20 to which the solar light
that has passed through the opening part 26 is dispersed and
irradiated so that the light is absorbed between the light
absorbers 30 and is converted into heat, the light absorbing part
may be formed instead of the light absorber wherein the inside of
the heat-insulated water tank 20 may be indented or colored in
black. Furthermore, the light absorbing part may be formed with the
light absorber 30 and the inside of the heat-insulated water tank
20.
[0052] Next, the principle and operation of solar heat collecting
is described.
[0053] FIG. 2 shows a schematic diagram that illustrates the
principle of solar heat collecting in the solar heat collecting
apparatus 1, and also shows the principle of the means to solve the
conventional problems. FIG. 3 shows a pattern diagram that
illustrates a schematic configuration example of the conventional
solar heat collecting apparatus.
[0054] As shown in FIG. 2, the solar light S is collected by a lens
or mirror, and is lead into the heat-insulated water tank 20
through the small opening part 26 at the upper part of the
heat-insulated water tank (box) 20.
The solar light Sf that has passed the opening part 26 is
re-dispersed inside the heat-insulated water tank 20 and heats the
absorber (light absorber) 30 inside it. Although the temperature of
the inside of the heat-insulated water tank 20 becomes high, since
the radiation loss is proportional to the opening area, the smaller
the opening part is, the smaller the radiation loss becomes.
[0055] In contrast, as shown in FIG. 3, the conventional solar heat
collecting apparatus 100 lets the solar light Sf in through a
transparent plate 121 from the upper part of the heat-insulated
water tank (box) 120. The solar light S is absorbed by the inside
absorber 130 and heats this up to a high temperature. However,
although the heat loss due to radiation and convention becomes
large as the temperature increases, most of the loss is from the
transparent plate 121 in the upper part. For example, the radiation
loss is proportional to the biquadrate of the temperature, and
therefore the increase rate of this loss is significant. Therefore
once it reaches a certain temperature or more, the incoming heat
turns into a loss as a whole, not being able to increase the
temperature any more.
[0056] The solar heat collecting apparatus shown in FIG. 1 is an
embodiment of the heat collecting apparatus that uses the above
principle.
[0057] According to this embodiment, by comprising the opened
heat-insulated water tank 20 that accumulates heat, the visor 25
that closes the upper part 20a of the heat-insulated water tank 20
and has the opening part 26 to let the collected solar light Sf in,
and the light absorber 30 that absorbs the solar light dispersed by
passing through the opening part 26 so that it is converted into
heat; the collected solar light enters the heat-insulated water
tank 20 from the opening part 26 opened in the visor 25, thus the
solar light can easily get into the heat-insulated water tank 20
and the heat generated from the light absorber 30 that absorbed the
solar light dispersed from the focal point is less likely to escape
from the heat-insulated water tank 20, allowing to provide the
solar heat collecting apparatus 1 that can effectively collect
energy from solar light with a little heat loss.
[0058] If it comprises a light collecting means such as the Fresnel
lens 10 for collecting the solar light S, this light collecting
means allows the concentration of the solar light Sf at the opening
part 26 opened in the visor 25 (closed part) so that the solar
light Sf can easily get into the container part and the heat
generated from the light absorber 30 (light absorbing part) is less
likely to escape from the heat-insulated water tank 20 (container
part), allowing the effective collection of energy from solar light
with a little heat loss.
[0059] If the width of the opening part 26 is five times greater
the diameter of the focal point of the collected solar light, since
the distribution in the radial direction of the collected solar
light at the focal point can be considered to have the Gaussian
distribution, the size of the opening part 26 is 5.sigma. (where
the diameter of the focal point is set to .sigma., the standard
deviation of the Gaussian distribution), therefore most of the
solar energy can be taken into the container part. Since the width
of the opening part 26 is sufficiently wide, even if there is a
fluctuation of the solar light due to winds or a blurriness of the
focal point due to steam, the solar energy can be sufficiently
taken into the container part.
[0060] In addition, since the solar light dispersed by passing
through the opening part 26 is absorbed and converted into heat by
the light absorber 30 near the bottom of the heat-insulated water
tank 20, the heating does not occur near the opening part 26 where
the solar light is collected, reducing the heat loss. In
particular, if the opening part 26 is a mere hole, the solar light
can easily pass through near the opening part 26 where the solar
light is collected, further reducing the heat loss.
[0061] By maximizing the incoming solar light and minimizing the
loss as much as possible, the solar heat collecting apparatus 1 can
efficiently have the medium or liquid reach a high temperature with
the solar light. In addition, in the desalination by the
evaporation process, a high temperature required for the efficient
evaporation can be achieved with small costs and a significant
reduction in the heat loss by maximizing the incoming solar light
and minimizing the loss as much as possible. Furthermore, the solar
heat collecting apparatus 1 can generate a high temperature medium
by efficiently absorbing the solar light and suppressing the loss
due to radiation and convection etc., allowing to provide an
apparatus that can produce hot water or a high temperature medium
for households, agriculture and industries.
[0062] A general method for obtaining hot water from the sun is to
produce a high temperature medium by leading the solar light
through transparent glass or plastic so that this light hits and
heats an absorber. However, the loss due to radiation and
convection from the high temperature part becomes very large as the
temperature gets higher. Therefore there was a limitation on the
temperature that can be efficiently achieved by the solar
light.
[0063] In the case of solar heating desalination apparatus, the
higher the temperature reaches, the better the efficiency becomes.
However, since the loss increases as the temperature increases, the
optimum temperature is comparatively low. Therefore a vacuum
apparatus is required for facilitating the evaporation, making the
apparatus expensive.
[0064] Furthermore, in order to prevent such a loss, the water
heater for households or businesses is provided with various
arrangements at the heat absorbing part, or is required for a
technique of heating water while the water goes through the pipe,
etc., making the apparatus expansive.
[0065] Moreover, although it has been said that the water shortage
will affect 3 billion people by 2025, if the desalination is done
by reverse osmosis membrane, it will require an electric power of 9
trillion kWh. This will be 50% or more of the electric power usage
of the entire world, 16 trillion kWh in 2002. Therefore a
desalination apparatus that uses the solar light has been sought;
however, its practical application has been difficult in terms of
its efficiency and price.
[0066] Next, a calculation example is described.
[0067] FIG. 4 shows a diagram that indicates the radiant heat loss
and the amount of heated water for temperatures, wherein the
calculation results of the increases in radiation and convective
loss are shown for temperatures.
[0068] Although the solar light in our county is 1 kW/m.sup.2 at
the maximum, it is often a half of this even on a sunny day.
Therefore, the radiation loss becomes the same as the solar light
at the temperature of around 90 degrees C. Since the radiation loss
is proportional to the radiation area, this loss can be reduced by
making the area of the opening part smaller than the area where the
solar light enters. The figure shows that the amount of water that
can increase its temperature by 10 degrees C. with an input from
which the radiation loss is subtracted, when the solar light of 1
kW enters. If the opening part has the same area as that of the
entrance plane, it shows that the water cannot go beyond 90 degrees
C. In contrast, if the opening area is reduced to one tenth, it
shows that the same hot water amount can be maintained in any
temperature range.
Embodiment 2
[0069] Next, the solar heat collecting apparatus regarding the
second embodiment according to the present invention is
described.
[0070] First, the schematic configuration of the solar heat
collecting apparatus regarding the second embodiment is described
with reference to the figure. Like symbols are used for like or the
corresponding parts as the first embodiment, and only different
configurations and functions are described. It shall be likewise
for other embodiments and alternative examples.
[0071] FIG. 5 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the second embodiment according to the present
invention, and also shows a schematic diagram of the solar heat
collecting apparatus that addresses the diurnal motion of the sun.
Furthermore, FIG. 5 indicates the arrangement that considers the
diurnal motion of the sun.
[0072] As shown in FIG. 5, the solar heat collecting apparatus 2
has a visor 25B and slit 26B (an example of the opening part)
different from those of the first embodiment.
[0073] Although the visor 25B just like the visor 25 of the first
embodiment closes the upper part 20a of the heat-insulated water
tank 20, it is formed into a long and narrow slit 26B.
[0074] The slit 26B has a width just about the same as or slightly
wider than the diameter of the focal point of the collected solar
light Sf, and has a length that can sufficiently absorb the effect
of the diurnal motion of the sun. The width of the slit 26B is set
to be wider than the size of the solar light at the focal length of
the solar light collected by the Fresnel lens 10 in consideration
of the fluctuation of the solar light due to winds or the
scattering of the solar light due to steam or dust. The length of
the slit 26B is set to a length that can accept the solar light
from angles with a degree that does not weaken the intensity of the
solar light due to the incident angle of the solar light slanted by
the diurnal motion of the solar light. Furthermore, the width and
length of the slit 26B is determined in consideration of the heat
loss.
[0075] Here, if the Fresnel lens 10 is 50 cm and the diameter of
the focal point is about 1 cm, the width of the slit 26B is about 5
cm in diameter. If the diameter of the focal point is set to
.sigma., the standard deviation of the Gaussian distribution, the
width of the slit 26B is 5.sigma.. The length of the slit 26B is
about the longitudinal width of the visor 25B, and it is made as
long as possible so that the solar light with an incident angle
significantly slanted by the diurnal motion can be taken in.
[0076] The solar heat collecting apparatus 2 is installed so that
the longitudinal direction of the slit 26B aligns with the
direction of east and west. When the sun comes down and the solar
light enters the slit 26B from a slanting direction, the solar
light passed through the Fresnel lens 10 is most collected above
the visor 25, and thus the Fresnel lens 10 may be up and down in
accordance with the diurnal motion. That means, the Fresnel lens 10
is provided with a far-to-near means for moving the Fresnel lens 10
close to and far away from the slit 26B in accordance with the
diurnal motion of the sun. Specifically, as the solar light slants,
the far-to-near means moves the Fresnel lens 10 close to the slit
26B.
[0077] In this manner, the opening part has the slit 26B. In
addition, a lens or mirror such as the Fresnel lens 10 is used for
collecting the light, and the slit 26B is provided as an example of
the opening part that can correspond to the movement of the light
collecting part which varies in accordance with the diurnal motion
of the sun.
[0078] Next, an example of the operation of the solar heat
collecting apparatus 2 is described.
[0079] When the sun moves from west to east, the light slantingly
enters the Fresnel lens; and the focal position moves to the
opposite side of the sun. Since this movement is linear throughout
the day, the slit 26B as shown in FIG. 5 is placed at the upper
part of the box so that the focal point that moves in accordance
with the diurnal motion is designed to move within this slit
26B.
[0080] As described above, according to this embodiment, the solar
heat collecting apparatus 2 is arranged so that the longitudinal
direction of the slit 26B aligns with the direction of the diurnal
motion of the sun, thereby the collected solar light Sf can be
taken into the heat-insulated water tank (container part) 20
without the tracking means that tracks the diurnal motion of the
sun, allowing the efficient collection of energy from solar light.
In addition, it is easy to set the area ratio of the solar light
receiving surface (upper part 20a) to the opening area of the slit
26B to 10 or more, thereby the heat loss can be set to 1/10 or
less.
[0081] Next, the first alternative example of this embodiment is
described. FIG. 6 shows a schematic diagram that illustrates a
schematic configuration example of the first alternative example of
the solar heat collecting apparatus 2, and also shows a schematic
diagram of the solar heat collecting apparatus that uses a fisheye
Fresnel lens for a fixed focal point.
[0082] As shown in FIG. 6, the fisheye Fresnel lens for a fixed
focal point 10B of the solar heat collecting apparatus 2B has a
structure that can comprise a curved lens or mirror etc. in order
to minimize the opening part.
[0083] FIG. 6 is an example that is designed to keep the focal
point at the same position at all times by curving the Fresnel lens
itself so that the focal position does not move. For example, it
can be created by curving a thin and flat Fresnel lens from side to
side. In this method, the Fresnel lens 10B is similar to the
fisheye lens, allowing the design of the Fresnel lens tailored to
the fisheye lens specification so that the solar light can be
collected from a wide range of angles. A lens that uses water can
be used as the Fresnel lens 10B.
[0084] As described above, since the light collecting means is the
Fresnel lens 10B that curves concave towards the opening part 26,
the solar light can be collected from a wide range of angles.
[0085] Next, the second alternative example of this embodiment is
described. FIG. 7 shows a schematic diagram that illustrates a
schematic configuration example of the second alternative example
of the solar heat collecting apparatus 2, and also shows a
schematic diagram of the solar heat collecting apparatus that
aligns an array of Fresnel lenses.
[0086] As shown in FIG. 7, the solar heat collecting apparatus 2C
comprises a Fresnel lens 10C in which small Fresnel lenses are
placed in a grid pattern of 3 (length).times.3 (width), a visor 25C
with a plurality of opening parts, and a plurality of slits 26C as
the opening parts. For example, the Fresnel lens 10C is formed with
a number of small light collectors such as lenses or mirrors etc.
in order to minimize the height of the apparatus; and each small
light collector has the slit 26C as a similar opening part that
keeps up with the solar light.
[0087] As shown in FIG. 7, in order to limit the height of the
apparatus as well as to make the manufacturing of the apparatus
inexpensive, small light collecting apparatuses are aligned in
parallel, and each apparatus is provided with a slit-like opening
part that predicts the movement of the solar light.
[0088] Here, the slit-like opening part that predicts the movement
of the solar light is an opening part with a slit along the path of
the movement of the light collecting point of the sun in accordance
with the diurnal motion and annual motion of the sun. The width of
each slit 26C is 5 cm, and the length of the slit 26C is about the
longitudinal width of the visor 25C. The length of the slit 26C is
up to the area adjacent to the small Fresnel lens in the Fresnel
lens 10C.
[0089] Next, the third alternative example of this embodiment is
described. FIG. 8 shows a schematic diagram that illustrates a
schematic configuration example of the third alternative example of
the solar heat collecting apparatus 2, and also shows a schematic
diagram of the reflective solar heat collecting apparatus.
[0090] As shown in FIG. 8, the solar heat collecting apparatus 2D
comprises a reflector plate (for example, concave mirror) 11 that
reflects the solar light Sfa collected by a Fresnel lens 10D, a
container 21 with a light absorber 30 and water W, a closed part
25D that closes the side 21a of the container 21, a slit (window
pinhole) 26D that is formed in the closed part 25D and can accept
the solar light Sfb from the reflector plate 11. Although the light
can be inflected for the slit-type opening part by providing a
reflector plate as shown in FIG. 8, various alternatives of those
can also be considered.
[0091] Next, the fourth alternative example of this embodiment is
described. FIG. 9 shows a schematic diagram that illustrates a
schematic configuration example of the fourth alternative example
of the solar heat collecting apparatus 2. FIG. 9 has a structure
with the opening part wherein the transparent plate that could have
been fogged by the evaporation from the liquid surface at a high
temperature is submerged in the liquid, showing a schematic diagram
of the solar heat collecting apparatus with a structure not
contacting with the steam.
[0092] As shown in FIG. 9, the solar heat collecting apparatus 2E
comprises a visor 25E as an example of the closed part so that the
upper part 22a of the container 22 is closed. The visor 25E has a
depressed part 27, and the opening part 26E is formed by window
glass 28 as an example of the transparent material that lets the
solar light through to the bottom of the depressed part 27.
[0093] When heating the liquid, steam is generated and attaches to
the transparent plate (window glass 28) of the opening part 26E,
scattering the incoming solar light. FIG. 9 shows an example of the
apparatus to prevent this. Submerging the opening part 26E as shown
in the figure can prevent the steam from attaching. In the prior
art, submerging the window causes the attachment of salt content or
dirt, making it difficult for the light to enter, however, if the
light is collected as shown in this technique so that the intensity
is increased, the attached substances can be dissolved and thus
removed. For example, in the case of salt content, it melts at 800
degrees C. or higher, and therefore, if quartz glass with the
softening point of 1650 degrees C. is used for the window glass 28,
the salt content can be removed without melting the window glass
28. This melting is performed, for example, when the water fills
only a part of the container and does not completely fill up, and
when the water W does not touch the window glass 28. The light
collecting means brings the solar-light-concentrated focal point
near the window glass 28, thereby the temperature of the window
glass 28 becomes high, melting the salt content etc. Although the
intensity of the solar light is increased by the maximum light
collection near the window glass 28, since it is re-dispersed and
then reaches the light absorber 30 after passing through the focal
point, the light absorber 30 will not be damaged.
[0094] As described above, the solar heat collecting apparatus 2E
comprises the light collecting part (Fresnel lens 10 etc.) that
achieves a high light intensity at the degree that even when the
dirt or salt content in the water attaches to the submerged opening
part 26E and blocks the incoming solar light, the solar light can
be converged so that the attached substances can be melted; and the
opening part 26E with a size in conformity to the light collecting
part.
[0095] As above, when the closed part has the depressed part 27,
and the opening part 26E is formed with a transparent material that
lets the solar light through to the bottom of the depressed part
27, the inside of the container 22 is filled up with a medium such
as water to submerge the opening part 26E, thereby preventing the
steam from attaching so that the solar light can easily get inside
the container 22, allowing more efficient collection of energy from
solar light.
[0096] Conventionally, when the water is directly heated by the
solar light, the window glass is fogged by the generated steam,
thus scattering the light, thereby the solar light cannot enter the
medium and heating is interfered, and therefore the water is sealed
inside a steel pipe and the water can only be heated by the solar
light indirectly from the outside of this pipe. In addition, when
the inside of the container is filled up with water in order to
prevent the steam, there were problems of damaging the container
due to the high pressure at a high temperature and of blocking the
light due to the dirt or salt content attached to the window glass.
These problems can also be solved by the solar heat collecting
apparatus 2E.
[0097] If the opening part 26E is not submerged, the solar heat
collecting apparatus 2E may have the opening part of no more than a
simple hole with a size that can sufficiently prevent the loss,
instead of using a window material (window glass 28). In this case,
the incoming solar light will not be interfered by foggy window
glass 28, since there is no window glass 28.
[0098] By collecting the solar light with the Fresnel lens 10, a
sufficient high temperature can be generated for sterilization and
the prevention of the hatching of eggs of creatures; and in the
case of the desalination of sea water, it can prevent the apparatus
from being blocked, since eggs of shellfish etc. may be taken into
the apparatus along with the sea water and grow to adult shellfish
inside the apparatus.
Embodiment 3
[0099] Next, the solar heat collecting apparatus regarding the
third embodiment according to the present invention is
described.
[0100] FIG. 10 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the third embodiment according to the present
invention. FIG. 10 also shows the principle of the means to solve
the problem etc. of having less amount of solar light that enters
the lens as the solar light comes down to the direction of the
horizon.
[0101] As shown in FIG. 10, the solar heat collecting apparatus 3,
in contrast to the solar heat collecting apparatus 1 of FIG. 1,
comprises the tracking means 40 that tracks the sun in accordance
with the movement of the sun.
[0102] The tracking means 40 has a rotation axis (for example,
diurnal motion adjusting axis) 41, and arms 42 that are rotatably
installed at the rotation axis 41. The rotation axis 41 is
positioned on the side of the upper part of the heat-insulated
water tank 20.
[0103] The arms 42 have a rod shape, and the base end part of the
arm 42 is rotatably connected to the rotation axis 41 while the
apical part of the arm 42 is fixed to the Fresnel lens 10.
[0104] The Fresnel lens 10 is fixed to the arms 42 on both sides.
The apical part of the arm 42 to which the Fresnel lens 10 is fixed
draws a circle about the axis on the light collecting point. By
moving along this circle, the Fresnel lens moves perpendicularly to
the line connecting the focal point and the sun. These arms 42 are
configured to be rotated by a belt or rod etc. operated by a small
motor (not shown).
[0105] As described above, the solar heat collecting apparatus 3 is
configured by comprising an apparatus for tracking the sun
(tracking means) and the heating part (light absorbing part) for
creating a high temperature medium by letting the collected solar
light through the opening part. It also has a small opening part 26
that lets the solar light collected by the Fresnel lens 10 through;
and the other part forms a heat-insulating wall 20b that stops the
heat from escaping (partially forming a visor 25), configuring the
highly efficient solar heat collecting apparatus 3 which can
efficiently make the medium sealed inside (water W) have a high
temperature and can store it for a long time.
[0106] Next, the tracking means 40 including the driving part is
described with reference to figures.
[0107] FIG. 11 shows a schematic diagram that illustrates an
example of the tracking means of the solar heat collecting
apparatus. FIG. 11 also shows a schematic diagram of the solar heat
collecting apparatus that illustrates an example of the embodiment
of the efficient solar heat collecting apparatus comprising a
driving part that can move the lens for tracking in accordance with
the diurnal motion and annual motion of the sun, and illustrates an
embodiment of the solar heat collecting apparatus that uses the
principle shown in FIG. 10.
[0108] Since the solar heat collecting apparatus 3B has a
configuration more or less different from the solar heat collecting
apparatus 3 of FIG. 10, a configuration example of the solar heat
collecting apparatus 3B is first described below.
[0109] As shown in FIG. 11, the solar heat collecting apparatus 3B
comprises a plurality of Fresnel lenses 10, a cylindrical
heat-insulated water tank 22, and the tracking means 40, etc.
[0110] Each Fresnel lens 10 is respectively supported by two arms
42, and rotates about the rotation axis (diurnal motion adjusting
axis or annual motion adjusting axis) 41.
[0111] The upper part 22a of the heat-insulated water tank 22 has a
function as the visor 25E. A plurality of opening parts 26E is
formed in the upper part 22a (visor 25E) corresponding to each
Fresnel lens 10. That means, the solar heat collecting apparatus 3B
comprises a container with a heat-insulating wall (heat-insulated
water tank 22), which is provided with a small opening part 26E for
letting the solar light through; and the solar light that has
entered through the hole in the opening part 26E heats the water
inside the heat-insulated water tank (box) 22 up to a high
temperature.
[0112] Next, the tracking means 40 comprises a motor (driving part)
45 that can move the lenses (Fresnel lens 10) for tracking in
accordance with the diurnal motion and annual motion of the sun.
The tracking means 40 comprises circular rotating parts (wheel 43)
for tracking the diurnal motion; and the rotating part is fixed to
the Fresnel lens 10 and is rotated by a belt 44 etc. so that the
lens can be rotated while it is configured so that the focal point
does not shift by the rotation. Furthermore, as shown in FIG. 11, a
number of wheels 43 are rotated by a single belt 44.
[0113] The tracking means 40 is provided above the heat-insulated
water tank 22 and has a rotation axis to rotate the Fresnel lens
10, while the opening part 26E is positioned on the rotation
axis.
[0114] As described above, this embodiment allows the absorption of
the change in the slanting of the solar light due to the diurnal
motion and annual motion of the sun by the tracking means 40,
thereby the solar light can easily get inside the container part
(heat-insulated water tank 22), and thus the solar heat collecting
apparatus 3 can efficiently collect energy from solar light.
[0115] When the opening part 26E is positioned on the rotation axis
41, even if the Fresnel lens 10 is rotated by the tracking means
40, the focal point of the Fresnel lens 10 can be positioned near
the opening part 26E, therefore the solar light is less likely to
get out from the opening part 26E even if tracking for the diurnal
motion and annual motion of the sun, thereby the solar light can
easily get inside the container part (heat-insulated water tank
22), allowing the efficient collection of energy from solar
light.
[0116] When the tracking means 40 moves the light collecting means
with reference to the container part, particularly when the light
collecting means is a Fresnel lens made of plastic, less power is
required for operating the tracking means.
[0117] Besides, the solar light is collected by a lens such as the
Fresnel lens 10 or a mirror, and is lead into a box through the
small opening part 26 etc. at the upper part of the box
(heat-insulated water tank) 20. The solar light that has passed the
opening part is re-dispersed inside the box and heats the absorber
(light absorber) 30 inside it. Although the temperature of the
inside becomes high, since the radiation loss is proportional to
the opening area, the smaller the opening part is, the smaller the
radiation loss becomes. However, if the system has the lenses and
opening parts that are fixed like these, as the solar light comes
down to the direction of the horizon, the amount of the solar light
that enters the lenses becomes less. Furthermore, when the incoming
sun significantly slants, the solar light enters the lens from a
slanting direction, thereby the amount of the incoming solar light
per unit area becomes less while the focal length varies, making it
difficult to tailor the opening part for the focal point of the
light collecting means. In the case of this embodiment, the solar
light that slantingly enters can be efficiently collected.
[0118] In addition, this embodiment can generate a high temperature
medium by efficiently absorbing the solar light and suppressing the
loss due to radiation and convection etc., allowing to provide an
apparatus that can produce hot water or a high temperature medium
for households, agriculture and industries and thus allowing to
perform power generation and water purification. That means, the
high temperature hot water generated by the solar heat collecting
apparatus 3 can be used as a heating source to achieve a complex
solar heat utilization system that drives the desalination
apparatus, cooling apparatus and power generation apparatus.
[0119] If this embodiment can store the high temperature hot water
for a long time, a temperature difference power generation becomes
possible by using the hot water, allowing a highly efficient power
generation with small costs, instead of the solar light power
generation which currently relies only on solar cells.
[0120] Next, another example of the tracking means of the solar
heat collecting apparatus is described.
FIG. 12 shows a schematic diagram that illustrates another example
of the tracking means of FIG. 11. FIG. 12 shows a schematic diagram
of the solar heat collecting apparatus that illustrates an example
of the embodiment of the tracking apparatus, comprising
circumferential rotating parts for tracking the diurnal motion; and
the rotating part is fixed to the Fresnel lens and is rotated by a
belt etc. so that the lens can be rotated while it is configured so
that the focal point does not shift by the rotation.
[0121] As shown in FIG. 12, a number of arms 42 are connected to a
single rod (not shown), and the rotation about the rotation axis 41
such as the diurnal motion adjusting axis can be given by the
motion of the rod in the horizontal direction.
[0122] The water W is stored inside the cylindrical heat-insulated
water tank 22 and the light absorber 30 is placed at the bottom of
the heat-insulated water tank 22. The rotation axis 41 of the
tracking means 40 is provided above the heat-insulated water tank
22, and is positioned at the height of the opening part 26E.
[0123] Next, an alternative example of the solar heat collecting
apparatus 3 is described with reference to figures.
FIG. 13 shows a schematic diagram that illustrates a schematic
configuration example of an alternative example of the solar heat
collecting apparatus of FIG. 10. It also shows a schematic diagram
of the solar heat collecting apparatus that illustrates an example
of the embodiment of the tracking apparatus, wherein in order to
track the annual motion, the base of the heat collecting apparatus
is formed in a cylindrical shape so that the rotation about the
axis of the cylinder is facilitated, allowing the tracking by this
rotation.
[0124] As shown in FIG. 13, the solar heat collecting apparatus 3E
comprises a Fresnel lens 10, a heat-insulated water tank 22 in
which an opening part is formed at the upper part and has water W,
and a tracking means 40.
[0125] The tracking means 40 has a motor 45B etc. that is connected
to a rotation axis (diurnal motion adjusting axis) 41, a rotation
axis (annual motion adjusting axis) 46, and a wheel. The
cylindrical heat-insulated water tank 22 is supported by a
plurality of wheels and is rotated on these wheels. This rotation
axis 46 is the annual motion adjusting axis. The motor 45B rotates
the heat-insulated water tank 22 about the rotation axis 46 in
accordance with the annual motion of the sun. As described above,
the tracking means 40 comprises a function of tracking for the
annual motion by the slanting of the entire apparatus.
[0126] As shown in FIG. 13, the body of the heat collector
(heat-insulated water tank 22) has a cylindrical shape; and the
axis (rotation axis 46) to adjust the annual motion is provided in
this cylindrical container in its axial direction, allowing to
track the solar elevation by the rotation about the rotation axis
46 of this annual motion adjusting axis. Arms 42 that rotate the
Fresnel lens are attached to the side wall of the cylindrical
container (heat-insulated water tank 22) and the Fresnel lens 10
fixed to these arms 42 tracks the diurnal motion. The part
including the arms 42 and the focal position moves along together
with the rotation about the axis of the cylindrical container
(rotation axis 41 of the diurnal motion adjusting axis), and the
speed of the motor 45B is adjusted so that the focal point and the
normal to the Fresnel lens 10 are aligned in a straight line
towards the sun.
[0127] As described above, an alternative example of this
embodiment can apply the tracking means 40 that moves a container
such as the heat-insulated water tank 22 for the slow movement of
the annual motion of the sun, thereby it can be separated from the
tracking means of the diurnal motion of the sun, simplifying the
mechanism of the tracking means 40.
[0128] Next, as an example of the light collecting means, a
comparative example wherein the Fresnel lens is used and not used
is described with reference to the experimental results.
[0129] FIG. 14 shows a diagram that illustrates an example of the
temperature time characteristic wherein the heat of the solar light
is collected into water by using the solar heat collecting
apparatus of FIG. 10. FIG. 14 also shows the results wherein the
solar light is let into a small hole opened in the heat-insulated
container (heat-insulated water tank) while tracking the solar
light.
[0130] The size of the container is 300.times.450.times.190 mm, and
2 liters of water is poured inside it. An acrylic Fresnel lens with
the size of 50 cm in length and width is used. As shown in FIG. 14,
if it is provided with a Fresnel lens, hot water at 100 degrees C.
can be obtained in approx. 5 hours.
[0131] In contrast, in the case of an ordinary method without a
Fresnel lens wherein the upper side is covered with glass without
light-collecting with a lens, the heating stops at around 60
degrees C. This indicates the advantageous effect of the present
invention.
[0132] Although an ordinary heat insulating material is used in the
experimental results shown in FIG. 14, if a calculation is made
with an evacuated insulating material with the currently highest
heat insulating performance having the heat conducting property of
0.002 W/mK (made by Matsushita Electric Industrial Co., Ltd.), the
results show that the hot water at 100 degrees C. only comes down
to 97 degrees C. after 24 hours for a cylindrical tube with 50 cm
in diameter that is half-filled with water. This is because, the
opening part is vanishingly small compared to the entire apparatus,
and thus the entire apparatus works just as a heat-insulated
container. Therefore, when this apparatus is used, hot water at
almost 100 degrees C. can be supplied for 24 hours, and a power
generation is possible with this hot water, indicating the
possibility to operate a desalination apparatus with this water
even during the night time without the sun.
[0133] Furthermore, if the Fresnel lens used in the experiment
shown in FIG. 14 is optimized and a container with a higher heat
insulating performance is used, 80% of the solar light can be used
for hot water. With this 100 degrees C. hot water as a heat source,
a power generation that uses the solar light is possible by using a
power generating apparatus based on the Rankine cycle that uses a
working fluid such as ammonia etc. that evaporates at a low
temperature. According to a trial calculation, the generating
efficiency in the Rankine cycle generation at near 100 degrees C.
is about 10%. Even if the hot water utilization efficiency from the
solar light is taken into consideration, it shows that it can reach
8%. In addition, the power generation becomes possible during the
day and night by storing the hot water, showing the possibility of
realizing a solar power generator that significantly outperforms
solar cells.
[0134] As described above, a highly efficient solar heat collecting
apparatus that can store the solar light for 24 hours can be
realized by storing hot water heated up to a high temperature with
a heat-insulating wall. The high temperature hot water can be used
as a heating source to realize a complex solar heat utilization
system that drives the desalination apparatus, cooling apparatus
and power generation apparatus.
Embodiment 4
[0135] Next, the solar heat collecting apparatus regarding the
fourth embodiment according to the present invention is
described.
[0136] FIG. 15 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the fourth embodiment according to the present
invention. FIG. 16 shows a schematic diagram that illustrates an
example of the optical path in the light guide of the solar heat
collecting apparatus of FIG. 15.
[0137] As shown in FIG. 15, the solar heat collecting apparatus 4,
in contrast to the solar heat collecting apparatus 1 in FIG. 1,
further comprises a light guide 50 placed at the opening part.
[0138] The light guide 50 comprises an entrance part 51 from which
the solar light that is collected by the Fresnel lens 10 enters, a
reflection surface 52 that reflects the solar light and leads it
into the heat-insulated water tank 20, and an exit part 53 that
outputs the solar light into the heat-insulated water tank 20. The
light guide 50 has a shape similar to a barrel, and is composed of
an upper part 50a and a lower part 50b. Although the width of the
light guide 50 once widens in the upper part 50a, the lower part
50b narrows down towards near the opening part.
[0139] As described above, the light guide 50 gradually widens in
the upper part 50a from the entrance part 51 towards the exit part
53. The light guide 50 also gradually widens in the lower part 50b
from the exit part 53 towards the entrance part 51.
[0140] The entrance part 51 is formed at the top of the upper part
50a and has a circular shape. As shown in FIG. 16, the reflection
surface 52 has a reflection surface 52a that extends from the
entrance part 51 to the outside of the axis A1, and the reflection
surface 52b that extends from the exit part 53 to the outside of
the axis A1.
[0141] The reflection surface 52a is formed in the inner surface of
the upper part 50a of the light guide 50, and it has a function to
lead the solar light with a large incident angle with reference to
the light guide 50 inside the heat-insulated water tank 20 with
less number of reflections in the reflection surface 52. The
reflection surface 52b is formed in the inner surface of the lower
part 50b of the light guide 50.
[0142] The exit part 53 is formed at the lower end of the lower
part 50b and has a size that allows the connection with the
circular opening part 26. The shape of the entrance part 51 and
exit part 53 is not limited to a circular shape, and it may be an
elliptical shape or a polygonal shape such as square or
triangle.
[0143] The angle of the reflection surface 52b with reference to
the line (axis A1) extended perpendicularly to the opening part 26
is comparatively smaller than the angle of the reflection surface
52a with reference to the axis A1. By facing the reflection surface
52a downward to provide a large angle of the reflection surface
52a, the solar light with a large incident angle can be easily lead
inside the heat-insulated water tank 20. In contrast, since the
surface of the reflection surface 52b faces upward, its angle is
better to be smaller so that the solar light can be easily lead
into the heat-insulated water tank 20. The angle of the reflection
surface 52b also depends on the size of the opening part 26, and
how to design the size of the entire solar heat collecting
apparatus 4 including how to arrange the Fresnel lens 10. In order
to meet the above requirements, the upper part 50a becomes shorter
than the lower part 50b.
[0144] The shape of the light guide 50 is not limited to
symmetrical with reference to the central axis of the axis A1; and
even if it is asymmetrical, the light guide 50 gradually widens in
the upper part 50a from the entrance part 51 towards the exit part
53. It is acceptable if the light guide 50 has a shape in which the
lower part 50b gradually widens from the exit part 53 towards the
entrance part 51.
[0145] In contrast to the solar heat collecting apparatus 1, the
Fresnel lens 10 is installed the same height as the light guide 50
above the heat-insulated water tank 20 supported by four supporting
members 16. Therefore, the focal position of the Fresnel lens 10 is
positioned near the entrance part 51.
[0146] Next, the light path in the light guide 50 is described with
reference to figures.
[0147] As shown in FIG. 16, the solar light Sf1 with the incident
angle .theta.1 (small incident angle) with reference to the light
guide 50, is lead into the heat-insulated water tank 20 through the
reflection by the reflection surface 52b. The solar light Sf2 with
the incident angle .theta.2 (large incident angle) just like the
sun coming down, is once reflected downwards by the reflection
surface 52a, then is reflected on the reflection surface 52b, and
is lead into the heat-insulated water tank 20. Since it is
reflected further downwards, that means, the incident angle with
reference to the reflection surface 52a becomes large, the
reflection angle with reference to the reflection surface 52a also
becomes large, thus leading the solar light with less number of
reflections before reaching the exit part 53.
[0148] In comparison with the case of FIG. 17 that illustrates an
example of the light path in the light guide of the comparative
example, the intensity of the solar light Sf2, as shown in FIG. 17,
is attenuated as it is repeatedly reflected on the reflection
surface 55. In contrast, as shown in FIG. 16, the solar light Sf2
has less number of reflections due to the effect of the reflection
surface 52a in comparison with the case of the reflection surface
55. In the case of the solar light Sf3 with an even larger incident
angle, it is lead into the heat-insulated water tank 20 with three
reflections.
[0149] Here, if the reflectance of one reflection in the reflection
surface 52 is 90%, since three reflections cause the reduction of
the solar light intensity to 73%, and thus the number of
reflections is better to be smaller.
[0150] As described above, according to this embodiment, by
comprising the light guide 50 that is placed at the opening part 26
and has the reflection surface 52 reflecting and leading the solar
light into the heat-insulated water tank 20 (container part), the
solar light is easily lead into the container part through the
reflections in the reflection surface 52 of the light guide 50,
allowing the efficient collection of energy from solar light, even
if the collected solar light slantingly enters the opening part 26
etc., or if the focal position of the collected solar light shifts.
In addition, since the opening part 26 is not directly exposed to
the open air, the internal heat is less likely to escape and thus
the heat loss is reduced.
[0151] In addition, the light guide 50 has the entrance part 51 of
the solar light, and the reflection surface 52a extends from the
entrance part 51 to the outside, thereby when the collected solar
light slantingly enters the opening part 26, the solar light
reflected on the reflection surface 52a faces the opening part 26
due to the reflection surface 52a extending from the entrance part
51 to the outside, and thus it is easily lead into the container
part, allowing the efficient collection of energy from solar
light.
[0152] In addition, since the light guide 50 has the exit part 53
that outputs the solar light into the heat-insulated water tank 20,
and the reflection surface 52b extends from the exit part 53 to the
outside; the width of the light guide 50 is once widened due to the
reflection surface 52 (52a) extending from the entrance part to the
outside, however, along the way, the reflection surface 52 (52b)
extends from the exit part to the outside, and thus the width of
the light guide 50 narrows down near the opening part 26.
Therefore, the opening part 26 can be made smaller so that the
solar light can easily enter and the heat does not escape from the
inside of the heat-insulated water tank 20, allowing the efficient
collection of energy from solar light with a little heat loss.
Embodiment 5
[0153] Next, the solar heat collecting apparatus regarding the
fifth embodiment according to the present invention is described.
FIG. 18 shows a schematic diagram that illustrates a schematic
configuration example of the solar heat collecting apparatus
regarding the fifth embodiment according to the present
invention.
[0154] As shown in FIG. 18, the solar heat collecting apparatus 5,
in contrast to the solar heat collecting apparatus 2 in FIG. 5, is
further provided with a light guide 60 placed at the slit 26B.
[0155] Just like the light guide 50, the light guide 60 has an
entrance part 61, a reflection surface (not shown) that leads into
the heat-insulated water tank 20, and an exit part 63, and is
composed of an upper part 60a and a lower part 60b. The entrance
part 61 has a long and narrow rectangular shape that can absorb the
movement of the diurnal motion etc. of the solar light. The exit
part 63 has a size that allows the connection with the slit 26B.
The cross-sectional shape of the light guide 60 is the same as the
shape shown in FIG. 16; and the width of the light guide 60 once
widens in the upper part 60a, however, the lower part 60b narrows
down towards near the opening part. Instead of the axis A1 of FIG.
16, a symmetrical plane is assumed.
[0156] As described above, the light guide 60 gradually widens in
the upper part 60a from the entrance part 61 towards the exit part
63. The light guide 60 also gradually widens in the lower part 60b
from the exit part 63 towards the entrance part 61.
[0157] If the opening part absorbs the movement of the diurnal
motion by the slit 26B, the light guide 60 can absorb the annual
motion. If the focal length of the Fresnel lens 10 is reduced in
order to downsize the solar heat collecting apparatus 5, the light
guide 60 can easily lead the solar light S that has entered from
the vicinity of the Fresnel lens 10 into the heat-insulated water
tank 20.
Embodiment 6
[0158] Next, the solar heat collecting apparatus regarding the
sixth embodiment according to the present invention is
described.
[0159] FIG. 19 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the sixth embodiment according to the present
invention. FIG. 20 shows a schematic diagram that illustrates an
example of the tracking means of the solar heat collecting
apparatus of FIG. 19.
[0160] As shown in FIG. 19, the solar heat collecting apparatus 6,
in contrast to the solar heat collecting apparatus 3 in FIG. 10,
further comprises a light guide 50 placed at the opening part
26.
[0161] The difference from the solar heat collecting apparatus 3 is
that, as shown in FIG. 19, the tracking means 40B has a rotation
axis supporting member 47 and the rotation axis 41 of the tracking
means 40B is provided outside the opening part 26 so that the focal
point of the Fresnel lens 10 can be positioned at the entrance part
51 of the light guide 50. As described above, the tracking means
40B is provided outside the opening part 26, and also has the
rotation axis 41 to rotate the Fresnel lens 10 (light collecting
means) so that the entrance part 51 of the light guide 50 is
positioned on the rotation axis 41.
[0162] In the solar heat collecting apparatus 6, the entrance part
51 of the light guide 50 is covered by a transparent hemispherical
entrance window 57.
[0163] Furthermore, in the case of the tracking means 40B with a
plurality of Fresnel lenses 10 as shown in the solar heat
collecting apparatus 3C of FIG. 12, each rotation axis 41 is
positioned at the height of the entrance part 51 with each rotation
axis supporting member 47 as shown in FIG. 20.
[0164] Each arm 42 has a link mechanism formed by a rod 48, and
each Fresnel lens 10 synchronously moves by sliding the rod 48.
[0165] As described above, according to this embodiment, the
tracking means 40B is provided outside the opening part 26, and
also has the rotation axis 41 to rotate the Fresnel lens 10 so that
the entrance part 51 of the light guide is positioned on the
rotation axis 41, thereby the focal point of the Fresnel lens 10 is
positioned near the entrance part 51 of the light guide even though
the Fresnel lens 10 is rotated about the rotation axis 41 by the
tracking means 40B, and thus the solar light is less likely to get
out the light guide when tracking the diurnal motion and annual
motion of the sun, therefore the solar light can be easily let
inside the heat-insulated water tank 20, allowing the efficient
collection of energy from solar light.
[0166] Since there is a rotation axis 41 outside the opening part
26, even if the Fresnel lens 10 is significantly slanted, the
Fresnel lens 10 is less likely to hit the upper part 25 of the
heat-insulated water tank 20. Particularly when two or more light
collecting means are aligned as shown in FIG. 20, it is
advantageous.
[0167] When the entrance part 51 of the light guide 50 is further
provided with a dome-shaped entrance window 57, the solar light
enters as perpendicularly to the entrance window 57 as possible
even if the solar light slants, thereby the reflection in the
surface of the entrance window 57 is prevented. In addition, the
entrance window 57 can prevent the diffusion of steam, thereby
preventing the dissipation of heat. As described above, energy from
solar light can be efficiently collected with a little heat
loss.
Embodiment 7
[0168] Next, the solar heat collecting apparatus regarding the
seventh embodiment according to the present invention is
described.
[0169] FIG. 21 shows a schematic diagram that illustrates a
schematic configuration example of the solar heat collecting
apparatus regarding the seventh embodiment according to the present
invention.
As shown in FIG. 21, the solar heat collecting apparatus 8, in
contrast to the solar heat collecting apparatus 2 in FIG. 5, is
further provided with a light guide 70 placed at the slit 26B. The
light guide 70 is a variation of the light guide 60 in FIG. 18.
[0170] Just like the light guide 60, the light guide 70 has an
entrance part 71, a reflection surface (not shown) that leads into
the heat-insulated water tank 20, and an exit part 73, and is
composed of an upper part 70a and a lower part 70b. The light guide
70, as shown in FIG. 21, has a central axis A2 as the center and is
separated into left and right; and its height lowers at the central
axis A2 and is gradually heightened as it goes to the ends. The
height of the light guide 70 is determined in accordance with the
focal position wherein the sun comes down and the solar light S
enters the Fresnel lens 10 from a slanting direction.
[0171] The entrance part 71 has a long and narrow rectangular shape
that can absorb the movement of the diurnal motion etc. of the
solar light. However, as shown FIG. 21, when the solar light S
enters the Fresnel lens 10 from a slanting direction, the focal
position moves away from the opening part 26B to the direction of
the central axis A2, and thus the plane of the entrance part 71
more or less slants towards the central axis A2. The entrance part
71 is blocked with window glass 77. The entrance part 71 may be
curved in accordance with the focal position wherein the solar
light S enters the Fresnel lens 10 from a slanting direction.
[0172] The exit part 73 has a size that allows the connection with
the slit 26B. The cross-sectional shape of the light guide 70 is
the same as the shape shown in FIG. 16; and the width of the light
guide 70 once widens in the upper part 70a, however the lower part
70b narrows down towards near the opening part. However, as shown
in FIG. 21, the width of the light guide 70 narrows as it goes
towards the central axis A2, and there will be no width near the
central axis A2.
[0173] As described above, in the case of this embodiment, the
Fresnel lens 10 does not need to be provided with a far-to-near
means for moving the Fresnel lens 10 close to and far away from the
slit 26B in accordance with the diurnal motion of the sun.
[0174] The Fresnel lens 10 etc. as the light collecting means may
be in a concentric pattern or in a linear pattern in order for the
light collection just like that of a cylindrical lens.
The function of the light collecting means may be able to lead the
solar light from the opening part into the container part in
accordance with the shape or size of the entrance part etc. of the
opening part or light guide.
[0175] Furthermore, the present invention is not limited to each
embodiment described above. Each embodiment described above is an
exemplification; and those with similar operational advantages by
having practically the same configuration as the technical idea
described in the claims of the present invention shall be included
in the technical scope of the present invention whatsoever.
[0176] JPA 2008-120538 and JPA 2008-203940 are herein incorporated
in its entirety by the reference thereto.
INDUSTRIAL APPLICABILITY
[0177] The conventional method can only use the efficiency of 50%
of the solar light even with hot water at 40 degrees C., and the
efficiency at a high temperature is significantly reduced, however,
according to the present invention, a heat collector with an
efficiency of nearly 100% can be offered even at a high temperature
of nearly 100 degrees C., and thus a wide range of application is
expected including solar heating steam electric generation and
solar heating desalination apparatus in addition to the use for
solar water heater. In addition, since high temperature hot water
can be efficiently produced, the high temperature hot water can be
supplied to the desalination apparatus while the hot water at
nearly 100 degrees C. is used for 24 hours to apply for turbine
generator by the ammonia evaporation such as the Kalina cycle,
possibly allowing a generating efficiency that outperforms solar
cells.
DESCRIPTION OF SYMBOLS
[0178] 1, 2, 2B, 2C, 2D, 2E, 3, 3B, 3C, 3D, 4, 5, 6, 7, 8: Solar
heat collecting apparatus [0179] 10, 10B, 10C, 10D: Fresnel lens
(light collecting means) [0180] 11 Reflection mirror (light
collecting means) [0181] 20, 21, 22, 20D, 20E: Heat-insulated water
tank (container part) [0182] 25, 25B, 25C, 25D, 25E: Visor (closed
part) [0183] 26, 26E: Opening part [0184] 26B, 26C, 26D: Slit
(opening part) [0185] 27: Depressed part [0186] 30: Light absorber
(light absorbing part) [0187] 40, 40B: Tracking means [0188] 41,
46: Rotation axis [0189] 50, 60, 70: Light guide [0190] 51, 61, 71:
Entrance part [0191] 53, 63, 73: Exit part [0192] 57: Entrance
window [0193] S: Solar light [0194] Sf: Collected solar light
* * * * *