U.S. patent application number 12/735620 was filed with the patent office on 2010-12-23 for hybrid solar heat power generation device.
Invention is credited to Kazuaki Ezawa, Takashi Kawaguchi, Toshihiko Maemura, Kounosuke Oku.
Application Number | 20100319678 12/735620 |
Document ID | / |
Family ID | 40985237 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100319678 |
Kind Code |
A1 |
Maemura; Toshihiko ; et
al. |
December 23, 2010 |
HYBRID SOLAR HEAT POWER GENERATION DEVICE
Abstract
Lower heat-collection efficiency and a much smaller amount of
solar heat may result from the providing of only a single receiver
on a supporting post to collect lights coming from both heliostats
located at nearby positions and heliostats located at faraway
positions. A solar heat power generation device to be provided by
the invention can avoid such problems. The solar heat power
generation device has the following characteristic features. The
solar heat power generation device comprises: a supporting post 4
including a receiver 1 that receives sunlight; and a plurality of
heliostats 6 which are provided concentrically around the
supporting post 4 and which reflect the sunlight towards the
receiver 1. The supporting post 4 includes at least two receivers
1a and 1b that are arranged in the up-and-down direction. The
receiver 1a provided at an upper-side position receives reflected
lights L1 coming from the heliostats 6a located at faraway
positions, and the receiver 1b provided at a lower-side position
receives reflected lights L2 coming from the heliostats 6b located
at nearby positions.
Inventors: |
Maemura; Toshihiko; (Tokyo,
JP) ; Ezawa; Kazuaki; (Tokyo, JP) ; Oku;
Kounosuke; (Tokyo, JP) ; Kawaguchi; Takashi;
(Tokyo, JP) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W., SUITE 600
WASHINGTON
DC
20004
US
|
Family ID: |
40985237 |
Appl. No.: |
12/735620 |
Filed: |
December 27, 2008 |
PCT Filed: |
December 27, 2008 |
PCT NO: |
PCT/JP2008/073869 |
371 Date: |
August 3, 2010 |
Current U.S.
Class: |
126/570 ;
126/573; 901/1 |
Current CPC
Class: |
Y02E 10/40 20130101;
F24S 2023/874 20180501; F24S 23/79 20180501; F24S 2023/833
20180501; F24S 40/20 20180501; F24S 23/70 20180501; F24S 20/20
20180501; Y02E 10/41 20130101 |
Class at
Publication: |
126/570 ;
126/573; 901/1 |
International
Class: |
F24J 2/46 20060101
F24J002/46; F24J 2/38 20060101 F24J002/38 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2008 |
JP |
2008-041941 |
Claims
1. A solar heat power generation device comprising: a supporting
post including a receiver that receives sunlight; and a plurality
of heliostats which are provided so as to surround the supporting
post and which reflect the sunlight towards the receiver, the solar
heat power generation device characterized in that the supporting
post includes at least two receivers that are arranged in the
up-and-down direction, the receiver provided at an upper-side
position receives reflected lights coming from the heliostats
located at faraway positions, and the receiver provided at a
lower-side position receives reflected lights coming from the
heliostats located at nearby positions.
2. The solar heat power generation device according to claim 1
characterized in that, when the light intensity of a reflected
light received by a receiver with a 90-degree incident angle is
100%, each of the receivers receives the reflected lights coming
from heliostats located at positions such that a light intensity of
60% or higher is achieved by each reflected light received by the
corresponding receiver.
3. The solar heat power generation device according to claim 1
characterized in that an incident angle of the reflected light
reflected by each heliostat located far away from the supporting
post towards the receiver provided at the upper-side position is
set at 75.degree. to 105.degree., and an incident angle of the
reflected light reflected by each heliostat located near the
supporting post towards the receiver provided at the lower-side
position is set at 75.degree. to 105.degree..
4. A solar heat power generation device comprising: a supporting
post including receivers that receive sunlight; and a plurality of
heliostats which are provided so as to surround the supporting post
and which reflect the sunlight towards the receivers, the solar
heat power generation device characterized in that one of the
receivers is provided at an upper-side position on the supporting
post, the one receiver receiving reflected lights coming from the
heliostats located at faraway positions, and a center reflector is
provided at a lower-side position on the supporting post, the
center reflector receiving reflected light coming from the
heliostats located near the supporting body, and another one of the
receivers is provided below the center reflector, the other
receiver receiving the sunlight having been reflected by the center
reflector.
5. A solar heat power generation device characterized in that at
least three supporting posts are assembled together to form a
pyramid shape, a columnar body is provided so as to extend upwards
from upper-end sides of the supporting posts, a center reflector is
fixed to the supporting posts that have been assembled together to
form the pyramid shape, in addition, receivers are provided below
the center reflector and on the columnar body, the receiver
provided on the columnar body receives reflected lights coming from
heliostats provided far away from the supporting posts, and the
center reflector receives reflected lights coming from heliostats
provided near the supporting posts, and the receiver provided on
the supporting posts receives the lights passed on to the receiver
by the center reflector.
6. The solar heat power generation device according to claim 4 that
includes: the supporting post equipped with the center reflector;
and the plurality of heliostats provided so as to surround the
supporting post, the solar heat power generation device
characterized by comprising: a frame formed in an arc shape that
fits a wall surface of the center reflector having a semicircular
arc sectional shape, the frame having one of its ends supported by
the supporting post; a cleaning robot which is attached to the
frame so as to be capable of moving along the frame; and moving
means for moving the frame with the cleaning robot in a
circumferential direction of the center reflector; and the solar
heat power generation device characterized in that the cleaning
robot includes a spray device that sprays a cleaning liquid onto
the wall surface of the center reflector.
7. The solar heat power generation device according to claim 4
characterized in that the receiver provided below the center
reflector includes a cone-shaped light receiving portion, and
dust-prevention means for allowing the transmission of the sunlight
therethrough but for blocking entry of dust such as sand is
provided to cover a light entrance for the sunlight formed in the
light receiving portion.
Description
TECHNICAL FIELD
[0001] The present invention relates to a power generation device
using solar heat. More specifically, the present invention relates
to a solar heat power generation device which is capable of
increasing the light collection efficiency for the light reflected
by heliostats and which is thus capable of enhancing the
power-generation efficiency.
BACKGROUND ART
[0002] Recently, there has been an increase in interest in the
global environments such as: global warming caused by exhaust gas
produced by the combustion of fossil fuels; and the depletion of
fossil fuels. In addition, alternative energy that may replace the
aforementioned fossil fuels has attracted more public attention.
For such alternative energy, wind power generation and photovoltaic
power generation have been spreading.
[0003] Meanwhile, there is a concentrating-type solar heat power
generation device in which a heat-transfer medium is heated by use
of heat produced by concentrating solar rays, steam is produced by
the heat of the heat-transfer medium, a steam turbine is driven by
the steam, and consequently electric power is generated. The device
has attracted public attention because the device can be operated
with similar power-generating facilities to those for the
conventional thermal power station and can achieve a high output
level.
[0004] Various types of concentrating-type solar heat power
generation devices have been proposed thus far, including a
trough-type solar heat power generation device (see, for example,
Patent Document 1), a dish-type solar heat power generation device
(see, for example, Patent Document 3), and a tower-type solar heat
power generation device (see, for example, Patent Document 2). The
trough-type device includes: reflectors each having a semi-circular
sectional shape and having a light-reflecting surface formed in one
surface thereof; and pipes extending in the axial directions of the
respective reflectors, and a heat-transfer medium is introduced
into the pipes. The tower-type device includes: a tower placed at
the center and provided with a heat-transfer-medium heating portion
on a top portion thereof; and multiple heliostats placed around the
tower. The dish-type device includes: a bowl-shaped reflector
having a light-reflecting surface formed in one surface thereof;
and a heat-transfer-medium heating portion provided near the
reflector.
[0005] In addition, a beam-down-system solar heat power generation
device has been proposed (see, for example, Non-Patent Document 1).
The beam-down-system solar heat power generation device includes a
large number of heliostats arranged around the center; a
heat-transfer medium heating unit provided in a lower portion; and
a curved reflector mirror (center reflector) provided above the
heat-transfer-medium heating unit.
[0006] Patent Document 1: WO2005/017421
[0007] Patent Document 2: Japanese patent application Kokai
publication No. 2004-169059.
[0008] Patent Document 3: Japanese patent application Kokai
publication No. 2005-106432.
[0009] Non-Patent Document 1: Solar Energy, Volume 62, Number 2,
February 1998, pp. 121-129 (9)
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
(Trough Type)
[0010] The reflector of the trough-type solar heat power generation
device has quite a large dimension in the width direction of the
reflector. A large number of reflectors are arranged in lines and
rows, and cause a problem that the solar heat power generation
device needs quite a large area to install the reflectors.
(Dish Type)
[0011] The dish-type solar heat power generation device is a
compact-sized device because each reflector dish collects the
sunlight and heats the heat-transfer medium. There is a limit to
the size of each reflector dish. Accordingly, the dish-type solar
heat power generation device has a problem of being inappropriate
for mass-scale power generation.
(Tower Type)
[0012] The tower-type solar heat power generation device has the
following problem. As FIG. 9 shows, a receiver 105 has a
light-receiving surface 105a irradiated with a reflected light
R109, a light coming from each heliostat 102 that is located away
from a tower 100. The incident angle .theta.1 of the reflected
light R109 into the light-receiving surface 105a is approximately a
right angle. Such an incident angle .theta.1 decreases the area
irradiated with the reflected light R109, and increases the amount
of light per unit area. The illuminance is thus enhanced and the
higher illuminance results in a larger amount of heat collected by
each heliostat 102. The light-receiving surface 105a is irradiated
also with a reflected light R108, a light coming from each
heliostat 101 that is located close to the tower 100. The incident
angle .theta.2 of the reflected light R108 into the light-receiving
surface 105a is an acute angle. Such an incident angle .theta.2
increases the area irradiated with the reflected light R108, and
decreases the amount of light per valley area. The illuminance is
thus lowered down and the lower illuminance results in a smaller
amount of heat collected by each heliostat 101.
[0013] Assuming that the heat-reception efficiency is represented
by sin .theta. (incident angle), the heat-reception efficiency for
each heliostat 102 located at the faraway position is approximately
100%, and that for each heliostat 101 located at the nearby
position is approximately 50%.
(Beam-Down Type)
[0014] The beam-down solar heat power generation device has the
following problem. As shown in FIG. 10, a center reflector 116 has
a reflection surface 116a. A reflected light R119, alight coming
from each heliostat 112 that is located far away from the center
reflector 116 enters the reflection surface 116a at an acute
incident angle. To put it differently, the reflected light R109
enters the center reflector 116 in a quite oblique manner. Such an
oblique incidence of the reflected light R119 results in a larger
area of the center reflector 116 irradiated with the reflected
light R119 coming from each heliostat 112 that is located at the
faraway position. Consequently, the heat-collection efficiency
becomes lower.
[0015] In addition, even when the heliostats are provided in an
area having a radius of approximately several hundreds of meters,
the center reflector must have an approximately 100-m diameter. A
center reflector of this size may weigh several hundreds of tons.
Such a heavy center reflector poses a problem of the strength of
the structure for supporting the center reflector.
(Present Invention)
[0016] In view of the aforementioned problems that the conventional
techniques have, an object of the present invention is to provide a
solar heat power generation device capable of achieving a higher
illuminance by reducing the area of the receiver irradiated with
the reflected light which is cast, onto the receiver, by each
heliostat located close to the receiver and with the reflected
light which is cast, onto the receiver, by each heliostat located
far away from the receiver.
Means for Solving the Problems
[0017] A hybrid solar heat power generation device according to the
present invention has the following configuration.
[0018] 1) The solar heat power generation device includes: a
supporting post including a receiver that receives sunlight; and a
plurality of heliostats which are provided so as to surround the
supporting post coaxially and which reflect the sunlight towards
the receiver. The solar heat power generation device is
characterized in that the supporting post includes at least two
receivers that are arranged in the up-and-down direction, the
receiver provided at an upper-side position receives reflected
lights coming from the heliostats located at faraway positions, and
the receiver provided at a lower-side position receives reflected
lights coming from the heliostats located at nearby positions.
[0019] 2) The solar heat power generation device is characterized
in that, when the light intensity of a reflected light received by
a receiver with a 90-degree incident angle is 100%, each of the
receivers receives the reflected lights coming from heliostats
located at positions such that a light intensity of 60% or higher
is achieved by each reflected light received by the corresponding
receiver.
[0020] 3) The solar heat power generation device is characterized
in that an incident angle of the reflected light reflected by each
heliostat located far away from the supporting post towards the
receiver provided at the upper-side position is set at 75.degree.
to 105.degree., and an incident angle of the reflected light
reflected by each heliostat located near the supporting post
towards the receiver provided at the lower-side position is set at
75.degree. to 105.degree..
[0021] 4) The solar heat power generation device includes: a
supporting post including receivers that receive sunlight; and a
plurality of heliostats which are provided so as to surround the
supporting post coaxially and which reflect the sunlight towards
the receivers. The solar heat power generation device is
characterized in that one of the receivers is provided at an
upper-side position on the supporting post, the one receiver
receiving reflected lights coming from the heliostats located at
faraway positions, and a center reflector is provided at a
lower-side position on the supporting post, the center reflector
receiving reflected light coming from the heliostats located near
the supporting body, and another one of the receivers is provided
below the center reflector, the other receiver receiving the
sunlight having been reflected by the center reflector.
[0022] 5) The solar heat power generation device is characterized
in that at least three supporting posts are assembled together to
form a pyramid shape, a columnar body is provided so as to extend
upwards from upper-end sides of the supporting posts, a center
reflector is fixed to the supporting posts that have been assembled
together to form the pyramid shape, in addition, receivers are
provided below the center reflector and on the columnar body, the
receiver provided on the columnar body receives reflected lights
coming from heliostats provided far away from the supporting posts,
and the center reflector receives reflected lights coming from
heliostats provided near the supporting posts, and the receiver
provided on the supporting posts receives the lights passed on to
the receiver by the center reflector.
[0023] 6) The solar heat power generation device includes: the
supporting post equipped with the center reflector; and the
plurality of heliostats provided so as to surround the supporting
post. The solar heat power generation device is characterized by
including: a frame formed in an arc shape that fits a wall surface
of the center reflector having a semicircular arc sectional shape,
the frame having one of its ends supported by the supporting post;
a cleaning robot which is attached to the frame so as to be capable
of moving along the frame; and moving means for moving the frame
with the cleaning robot in a circumferential direction of the
center reflector; and the solar heat power generation device
characterized in that the cleaning robot includes a spray device
that sprays a cleaning liquid onto the wall surface of the center
reflector.
[0024] 7) The solar heat power generation device is characterized
in that the receiver provided below the center reflector includes a
cone-shaped light receiving portion, and dust-prevention means for
allowing the transmission of the sunlight therethrough but for
blocking entry of dust such as sand is provided to cover a light
entrance for the sunlight formed in the light receiving
portion.
[0025] 8) The solar heat power generation device is characterized
in that a receiver is provided at an upper-side position on a
supporting post so as to receive the reflected lights from a
plurality of heliostats provided concentrically around the
supporting post, and the light receiving surface of the receiver is
formed in a bowl-like shape so that the incident angle of the
reflected light coming from each of the plurality of heliostats can
be either a right angle or an angle close to a right angle with
respect to the light receiving surface.
EFFECTS OF THE INVENTION
[0026] 1) In the solar heat power generation device, the receiver
provided at an upper-side position on the supporting post receives
the reflected lights coming from the heliostats located at faraway
positions whereas the receiver provided at a lower-side position on
the supporting post receives the reflected lights coming from the
heliostats located at nearby positions. In addition, the light
receiving plate of each receiver has a depression angle so that the
reflected light coming from each receiver can form either a right
angle or an angle close to a right angle with the light receiving
plate. Accordingly, an incident angle of 90.degree. or of an angle
close to 90.degree. with the light receiving plate of each receiver
is achieved by each of the corresponding reflected lights coming
from the heliostats located in an area extending from positions
close to the supporting post to positions far away from the
supporting post. With such an incident angle, each reflected light
entering the corresponding receiver can form a smaller irradiation
area, and thereby a higher illuminance can be achieved. The higher
illuminance increases the amount of heat received by the receiver,
and enhances the heat-exchange efficiency with the molten salt.
Consequently, more heat can be generated.
[0027] 2) The solar heat power generation device use more
efficiently the reflected lights coming from the heliostats
provided in an area extending from nearby positions to faraway
positions. Accordingly, a larger-scale solar heat power generation
device can achieve a higher output capacity.
[0028] 3) The cleaning robot removes sand and dust that adhere to
the surface of the center reflector. Though such sand and dust
would otherwise make the center reflector reflect light towards the
receiver less efficiently, the cleaning robot can prevent such
lower efficiency from occurring.
[0029] 4) Without the dust-prevention means, dust particles such as
sand that enter the light receiving portion of the receiver would
dirty the surface of the internal wall of the light receiving
portion, resulting in lower heat-exchange efficiency with the
molten salt. The dust-prevention means can avoid such lower
heat-exchange efficiency.
[0030] 5) Each light receiving plate is formed in a shape that can
achieve an incident angle of a 90.degree. or an angle close to
90.degree. for each of the reflected lights cast onto the light
receiving plate of the corresponding receiver by the heliostats
provided in an area extending from the nearby positions to the
faraway positions. Such an incident angle increases the amount of
heat collected by each receiver, resulting in an increase in the
amount of power generation. In addition, an increase can be
achieved in the heat-collection efficiency for the reflected lights
coming from the heliostats located at faraway positions.
Accordingly, a larger-scale solar heat power generation device can
be constructed to achieve a higher output capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic diagram illustrating a solar heat
power generation device according to the present invention.
[0032] FIG. 2 is a schematic sectional diagram illustrating a
receiver of the solar heat power generation device according to the
present invention.
[0033] FIG. 3 is a chart illustrating the incident angle of the
sunlight that is cast onto the receiver and the area irradiated
with the sunlight.
[0034] FIG. 4 is a chart illustrating the incident angle of the
sunlight that is cast onto the receiver and the amount of generated
power.
[0035] FIG. 5 is a diagram illustrating a solar heat power
generation device according to a second embodiment of the present
invention.
[0036] FIG. 6 is a schematic diagram illustrating a cleaning
apparatus.
[0037] FIG. 7 is a diagram illustrating a solar heat power
generation device according to a third embodiment of the present
invention.
[0038] FIG. 8 is a schematic diagram illustrating a receiver of the
solar heat power generation device according to the third
embodiment of the invention.
[0039] FIG. 9 is a schematic diagram illustrating a conventional
tower-type solar heat power generation device.
[0040] FIG. 10 is a schematic diagram illustrating a conventional
beam-down solar heat power generation device.
[0041] FIG. 11 is a chart illustrating the amount of generated
power and the radius of the area where heliostats are provided.
DESCRIPTION OF SYMBOLS
[0042] A1, A2, A3 solar heat power generation device [0043] L
sunlight [0044] L1, L2, L3, L11, L12, L21, L22 reflected light
[0045] c1 short distance section [0046] c2 middle distance section
[0047] c3 long distance section [0048] 1a, 1b, 1c, 11a, 12, 21a, 22
receiver [0049] 4, 14, 24 supporting post [0050] 6a, 6b, 6c, 16a,
16b, 26a, 26b heliostat [0051] 13, 23 center reflector [0052] 22a
opening portion [0053] 22b light collecting portion
BEST MODE FOR CARRYING OUT THE INVENTION
[0054] Hereinafter, a solar heat power generating device according
to the present invention will be described by referring to the
drawings.
Embodiment 1
[0055] FIG. 1 is a schematic diagram illustrating a solar heat
power generation device A1 according to the present invention. The
solar heat power generation apparatus A1 includes plural receivers
1a, 1b, and 1c, which are provided on a supporting post 4 and
arranged in this order from the top to the bottom. Each of the
receivers 1a, 1b, and 1c, is a heat exchanger which absorbs the
solar heat and which transfers the heat to a heat-transfer medium.
Multiple heliostats 6 (6a, 6b, and 6c) are provided concentrically
around the supporting post 4 with the receivers 1a, 1b, and 1c.
Each heliostat 6 includes a reflector mirror m made of plural small
mirror plates that reflect the sunlight, that is, the solar
heat.
[0056] As FIG. 2 shows, each receiver 1 includes a heat receiving
plate 1a and a heat-transfer-medium pipe 9. The heat receiving
plate 1a is a cone-shaped member formed by connecting multiple
plate-shaped heat absorbers. The heat-transfer-medium pipe 9 is
wound around plural times along the internal circumference of the
heat receiving plate 1a. Each heliostat 6 includes a device for
tracking the sunlight S and a driving device for driving a
reflector mirror m vertically and horizontally. Each heliostat 6 is
controlled so as to reflect the sunlight S towards the
corresponding receiver 1.
[0057] As FIG. 1 shows, the receiver 1a located at the highest
position on the supporting post 4 is designed to receive a
reflected light R1 coming from each of the heliostats 6a located
far away from the supporting post 4. The receiver 1b located at the
middle position on the supporting post 4 is designed to receive a
reflected light R2 coming from each of the heliostats 6b located at
an intermediate position. The receiver 1c located at the lowest
position on the supporting post 4 is designed to receive a
reflected light R3 coming from each of the heliostats 6c located
closely to the supporting post 4.
[0058] The incident angle of each of the reflected lights R1, R2,
and R3 into the corresponding one of the receivers 1a, 1b, and 1c
is adjusted by controlling the angle of the light receiving plate
1a of each of the receivers 1a, 1b, and 1c. The incident angles are
adjusted so that the intensities of their corresponding reflected
lights can be equal to or higher than 60%.
[0059] Specifically, as FIG. 2 shows, the incident angle of each of
the reflected lights R1, R2, and R3 ranges from the lowest incident
angle .beta.=75.degree. to the highest incident angle
.gamma.=105.degree.. As FIG. 3 shows, the irradiation efficiency of
the sunlight that is cast onto the light receiving plate 1a becomes
the highest when the incident angle of the sunlight into the light
receiving plate 1a is 90.degree. (i.e., in the case of
perpendicular incidence). As the incident angle becomes either
smaller or larger than 90.degree., the irradiation efficiency
decreases rapidly in an exponential fashion. Accordingly, the
incident angle is designed to range from 75.degree. to 105.degree.
because an incident angle within this range guarantees an intensity
of the reflected light that is equal to or higher than 60%.
[0060] In addition, the light receiving plate 1a is attached so as
to make a tilt angle .alpha. with the axial direction of the
supporting post 4. The tilt angle .alpha. is adjusted so that the
incident angles of the reflected lights R1, R2, and R3 coming from
the corresponding heliostats 1a, 1b, and 1c can be within a range
from 75.degree. to 105.degree..
[0061] Now, assume that the area formed on the light receiving
plate 1a by the sunlight reflected towards the light receiving
plate 1a when the incident angle 90.degree. is 100. When the
incident angle ranges from 75.degree. to 105.degree., the area
formed on the light receiving plate 1a by the sunlight that is
obliquely cast onto the light receiving plate 1a is no more than
104. Accordingly, even the heliostat that does not cast the
sunlight perpendicularly onto the light receiving plate 1a can have
an irradiation efficiency that is equal to or higher than 60%.
[0062] In addition, as FIG. 4 shows, since the incident angle of
the reflected light that is cast onto the light receiving plate 1a
is restricted within a range from 75.degree. to 105.degree., even
the heliostat whose incident angle of the sunlight cast onto the
light receiving plate 1a deviates most from 90.degree. can have a
power-generation efficiency that is equal to or higher than
60%.
[0063] As FIG. 4 (illustrating the incident angle and the
power-generation efficiency) shows, the incident angle is adjusted
within a range from 75.degree. to 105.degree. so that the
power-generating efficiency can be equal to or higher than 60%.
Accordingly, as FIG. 4 shows, once the incident angle departs from
the above-mentioned range, the amount of power generation decreases
in an exponential manner. Assuming that the amount of power
generation with an incident angle of 90.degree. is 100, even the
heliostat whose incident angle of the sunlight cast onto the light
receiving plate 1a deviates most from 90.degree. can keep an amount
of power generation that is equal to or larger than 60.
[0064] As FIG. 1 shows, the heliostats 6 are divided into groups
and are individually adjusted so that the incident angle of each of
the reflected lights R1, R2, and R3 into the corresponding one of
the receivers 1a, 1b, and is can be kept within the above-mentioned
range. Specifically, a short distance section C1, a middle distance
section C2, and a long distance section C3 are formed in this order
from the area closest to the support post 4 outwards. The
heliostats 6a, 6b, and 6c are provided in their corresponding
sections C1, C2, and C3. The heliostats 6a, 6b, and 6c are adjusted
individually so that the sunlight can be cast onto their
corresponding predetermined receivers 1a, 1b, and 1c, and, in
addition, are adjusted so that the incident angle of each of the
reflected lights R1, R2, and R3 that are cast onto their
corresponding receivers 1a, 1b, and 1c can be within the
above-mentioned range (a range from 75.degree. to 105.degree.).
[0065] Specifically, in this embodiment, the heights at which the
receivers 1a, 1b, and 1c are positioned are: approximately 105 m
for the receiver 1a for long distance (the height h3);
approximately 60 m for the receiver 1b for middle distance (the
height h2); and approximately 30 m for the receiver 1c for short
distance (the height h1). The above-described sections are the long
distance section C3, the middle distance section C2 and the short
distance section C1 which respectively are approximately 100 m to
400 m, approximately 50 m to 200 m, and approximately 15 m to 60 m,
away from the supporting post 4. Accordingly, the incident angle of
each of the reflected lights R1, R2, and R3 that are cast onto
their corresponding receivers 1a, 1b, and 1c can be kept within a
range from 75.degree. to 105.degree..
[0066] In the solar heat power generation device A1 having the
above-described configuration, the predetermined receivers 1a, 1b,
and 1c receive their corresponding reflected lights R1, R2, and R3
that are cast by the heliostats 6. Thus, the heat-transfer medium
(such as a molten salt containing 40% sodium nitride, 7% sodium
nitrate, and 53% potassium nitrate, for example) supplied to the
receivers 1a, 1b, and 1c is heated up to approximately 500.degree.
C. Then, the high-temperature molten salt is introduced into the
heat exchanger provided next to the supporting post 4, and
generates steam, which drives a turbine power generator to generate
electric power.
[0067] The molten salt that has been heated up by the receivers is
stored in a high-temperature molten-salt tank, and is then sent to
the heat exchanger, where the molten salt is used for generating
electric power. After that, the molten salt is stored in a
low-temperature molten-salt tank. The high-temperature molten-salt
tank stores the molten salt of an amount capable of accumulating
heat that is enough to generate electric power even while the solar
heat is not available, for example, at night. Consequently,
electric power can be generated incessantly both day and night.
[0068] In this embodiment, plural receivers are provided on the
supporting post so that the incident angle of 90.degree. or an
angle close to 90.degree. can be achieved by each of the reflected
lights that are cast by the heliostats onto their corresponding
receivers. Accordingly, the light receiving area on each of the
receivers onto which the reflected lights from the corresponding
heliostats are cast becomes so small that the illuminance becomes
strong. Consequently, the amount of collected solar heat increases
so that the amount of heat given to the molten salt increases as
well. As a result, more electric power can be generated.
[0069] In addition, the larger-scale solar heat power generation
device can increase significantly the amount of the collected heat,
so that mass-scale power generation can be made possible.
Embodiment 2
[0070] In this embodiment, as FIG. 5 shows, a receiver 11a is
provided at a higher position on a supporting post 14 whereas a
center reflector 13 and a receiver 12 are provided at lower
positions on the supporting post 14. The center reflector 13 is
made of multiple reflector mirrors 13a each of which has a small
mirror-plate shape. The multiple reflector mirrors 13a are
collected together to form the bowl-shaped center reflector 13 that
has a semicircular-arc sectional shape. The center reflector 13 is
fixed by means of either plural cables 13c or plural hanging means
13c attached to the supporting post 14.
[0071] A heat-collecting recessed portion is formed in the upper
surface of the receiver 12 provided at the lower position. The
heat-collecting recessed portion accepts the reflected light coming
from the center reflector 13. Multiple heat-transfer-medium pipes
are provided so as to surround the recessed portion, and the solar
heat can be given to the heat-transfer medium by means of these
heat-transfer-medium pipes.
[0072] As FIG. 5 shows, multiple heliostats 16 are provided
concentrically around the supporting post 14. The heliostats 16 are
divided into a group of heliostats 16b located near the supporting
post 14 and another group of heliostats 16a located far away from
the supporting post 14. Each of the heliostats 16b located at
nearby positions casts a reflected light R11 of the sunlight S onto
the center reflector 13 whereas each of the heliostats 16a located
at faraway positions casts a reflected light R12 onto the receiver
11a provided at the upper position on the supporting post 14. In
addition, the reflected light R12 that has cast onto the center
reflector 13 is collected by the receiver 12 located at the lower
position.
[0073] The heliostats 16b located at nearby positions and the
heliostats 16a located at faraway positions as well as the receiver
11a and the center reflector 13 are individually adjusted so that
each of the light-receiving areas formed on the receiver 11a and on
the center reflector 13 can be so small as to make its illuminance
stronger. To achieve small light-receiving areas, each of the
incident angles of the incident lights is a right angle or an angle
close to a right angle. Specifically, as in the case of the first
embodiment, the incident angle is within a range from 75.degree. to
105.degree..
[0074] The center reflector 13 is equipped with a cleaning means G
that cleans a wall surface (reflector-mirror surface) of the center
reflector 13. As FIG. 6 shows, the cleaning means G is formed in an
arc shape that can fit the wall surface 13c of the center reflector
13. The cleaning means G includes a frame f, a cleaning robot GR,
and a driving device m2. The lower-end side of the frame f is
supported on the supporting post 14. The cleaning robot GR is
attached to the frame f so as to be capable of moving along the
frame f. The driving device m2 moves the frame f, to which the
cleaning robot GR is attached, along the circumferential direction
of the center reflector 13.
[0075] The frame f is formed in a narrow width so as to reduce the
blocking of the reflected light that is cast onto the center
reflector 13. In addition, the frame f is made of a heat-resistant
alloy so as to resist high-temperature heat produced by the
reflected light cast by the heliostats 6. Incidentally, the alloy
is one of light weight. Some examples of alloys usable for this
purpose are high-nickel/iron alloys such as Inconel.RTM. alloys and
Hastelloy.RTM. alloys.
[0076] The upper-end side of the frame f is connected to a driving
device m1 that is provided on the ring-shaped perimeter edge
portion of the center reflector 13. The driving device m1 and the
driving device m2 provided on the lower-end side of the frame f
move the frame f. Note that the frame f may be one of cantilevered
type with the driving device m2 provided on the supporting post 14
being the only support for the frame f.
[0077] The cleaning robot GR includes a cleaning device n, which
sprays a cleaning liquid onto the wall surface 13c of the center
reflector 13. The cleaning device n includes a spray nozzle and the
like for the purpose of washing, with water, the dust or the like
that adheres to the wall surface 13c. In the surrounding area of
the cleaning device n, a synthetic-resin cover is provided to
prevent the washing liquid from leaking out. The cleaning liquid is
re-collected and filtered by a filtration device, and then is
sprayed by the nozzle. To put it differently, the liquid is
circulated and re-used. Alternatively, the nozzle may spray either
hot water or steam obtained by using the heat of the heat-transfer
medium (molten salt) for power generation.
[0078] The cleaning means G is designed to operate while none of
the reflected lights R11 and R12 enter the reflector, e.g., at
night. The cleaning means G is made to operate automatically at
night by a computer.
[0079] Note that, while the heliostats 6 are casting the solar heat
onto the center reflector 13, the cleaning robot GR is held at a
position of either the upper-end side or the lower-end side of the
frame f so that the cleaning robot GR can avoid the influence of
the solar heat. In the Northern hemisphere, the heliostats located
at the northern side of the center reflector 13 receive stronger
sunlight than the heliostats located at the southern side thereof.
Accordingly, the frame f is moved to the southern side of the
center reflector 13, and thus both the influence of the solar heat
and the occurrence of the blocking can be reduced.
[0080] In this embodiment, the supporting post 14 is equipped with
the receivers 11a and 12, and is also equipped with the center
reflector 13. The reflected light R12 coming from the heliostats
16b located near the supporting post 14 is cast onto the center
reflector 13 whereas the reflected light coming from the heliostats
16a located far away from the supporting post 14 is cast onto the
receiver 11a. Accordingly, the reflected lights coming from
heliostats located in sections from a position near the supporting
post 14 to a faraway position can be received in a highly efficient
manner by the receivers 11a and 12.
[0081] Accordingly, even if the heliostats are provided in an area
(measured in terms of the radius) that is approximately the same as
the corresponding area in conventional cases, the amount of power
generation can increase as FIG. 11 shows. In addition, a
significant increase in power generating capacity can be achieved
by a larger-scale power generation device of this kind.
Embodiment 3
[0082] The device of this embodiment, as FIG. 7 shows, includes a
receiver 21a that is provided in an upper-side portion of a
columnar body 25. In addition, supporting posts 24 are provided so
as to open downwards to form a pyramid shape. A center reflector 23
is provided in the space thus formed under the supporting posts 24.
A receiver 22 is provided below the center reflector 23.
[0083] A light collecting portion 22b is formed on the upper side
of the receiver 22. The light collecting portion 22b has a
crucible-like shape, and collects the solar heat reflected by the
center reflector 23. A heat exchanging portion 22c is formed on the
lower side of the receiver 22. A heat-transfer-medium pipe 22f is
wound around the external circumference of the heat exchanging
portion 22c. The internal wall of the light collecting portion 22b
has a mirror surface so that the solar heat can be reflected inside
the light collecting portion 22b and can be introduced into the
heat exchanging portion 22c located below.
[0084] An opening portion 22a is formed in the light collecting
portion 22b of the receiver 22 that is provided below the center
reflector 23. A dust-prevention means g is provided on the opening
portion 22a. While the sunlight (solar heat) can pass though the
dust-prevention means g, dust such as sand cannot pass through the
dust-prevention means g. An example of the dust-prevention means g
is a lid plate made of borosilicate glass or the like.
[0085] Without the dust-prevention means g, dust such as sand may
enter the inside of the light collecting portion 22b of the
receiver 22 through the opening portion 22a of the light collecting
portion 22b, and may dirty the mirror surface and the heat
exchanging portion 22f, resulting in lower light-collection
efficiency and lower heat-exchange efficiency. The dust-prevention
means can prevent the entry of the dust, and thus the lowering of
the efficiencies can be prevented from happening. The receiver 22
has a height of approximately 5 m, so that it is not easy to clean
the inside of the receiver 22. Providing the dust-prevention means
g can save the user the trouble of performing the maintenance work
for the receiver 22.
[0086] In this embodiment, the reflected light coming from each of
the heliostats located at faraway positions is received by the
receiver provided on the upper side, whereas the reflected light
coming from each of the heliostats located at nearby positions is
received firstly by the center reflector provided on the lower
side, and then passed onto the receiver provided on the ground.
Accordingly, an incident angle that is close to a right angle can
be achieved for the sunlight that is cast by the heliostats located
in sections from nearby positions to faraway positions.
Accordingly, the intensity of the light with which the light
receiving surface of the receiver is irradiated becomes stronger.
The strong intensity of the light allows more steams to be
generated, resulting in an increase in the power generating
capacity.
[0087] In addition, the pyramid-shaped supporting posts provided to
support the center reflector gives higher strength to the
supporting structure, resulting in an improvement both in the quake
resistance and in the wind resistance.
[0088] In addition, the dust-prevention means is provided to cover
the light entrance of the receiver provided below the center
reflector. This prevents the lowering down of the heat exchange
efficiency between the molten salt and the reflected light, which
would otherwise be caused by dust such as sand dirtying the mirror
surface of the inside of the light collecting portion 22b.
[0089] In addition, the receiver provided below the center
reflector includes the light receiving portion with a crucible-like
shape, a difficult shape for the heat of the incident light to
escape from. Consequently, higher thermal efficiency can be
achieved.
* * * * *