LUNENBURG — At the water’s edge of a 119-year-old boatyard in
Lunenburg, engineers are perfecting a surprisingly simple method
of harnessing the sun’s energy to melt metals.
The Prometheus Project uses an ordinary mirror — albeit quite huge
at five metres square — that bounces the sun’s energy onto a
smaller mirror that then directs it into a crucible where it melts
a lump of aluminum at 660 C.
Inventor Peter Kinley said the groundbreaking results have
astonishing potential for the industrial and residential sectors.
It can be used as an environmentally friendly way to melt metal
and to heat water to warm houses.
"It’s a good time to look at renewables."
With the high cost of oil, it is expensive to melt the metals the
foundry needs to create parts for boats and ships, and burning oil
hurts the environment. Kinley wanted to find a way to concentrate
the sun’s energy and harness it to melt metals.
This invention started out as a little experiment four years ago
behind his farmhouse in Lilydale, just outside Lunenburg.
"We wanted to find a renewable source of energy for the foundry,
something that was able to give us a reduction in costs over our
current methods and that was sustainable and long term," said
Kinley, president and CEO of Lunenburg Industrial Foundry
& Engineering Ltd.
The folks working on this solar furnace, with its patented Kinley
Dual Mirror System, are usually refurbishing boats — from Theodore
Too to the Bluenose II and luxury yachts. But Kinley said it’s an
ideal setup for his invention — he has the carpenters,
electricians, plumbers and welders he needs to refine the
technology, as well as the space to store the contraption in a
huge boat shed.
His first prototype, Alpha, was rudimentary, using polished
stainless-steel sheets inside plywood casing.
"I was surprised at how well our system worked from the get-go. We
were able to melt metal the first time out."
It generated a temperature of 407 C, melting a metal called
babbit, which is made from lead and zinc.
He called the National Research Council the next day to see who
else was studying such technology and was shocked to learn no one
was in Canada or anywhere else in the world.
His team has been refining that original prototype a little more
each year.
"We decided to find a way to inexpensively duplicate what a
magnifying glass would be able to do on a much larger scale,"
Kinley said.
With his initial success, he knew he had something big on his
hands, but he didn’t want word to get out before he patented the
design. So he dubbed the project Prometheus, for the Greek
mythological character who stole fire from Zeus and gave it to
people.
"Prometheus is a name that we adopted as a code word for the
project because our patent attorneys advised us to keep it under
wraps until the patenting process was complete. So the name sort
of stuck."
Instead of telling people he was working on a solar project, he
would tell the curious he was working on Prometheus, and they just
assumed it was a boat.
As the foundry tweaks its invention, it has been working with
Dalhousie University in Halifax to create a computer model of the
temperatures the current system, Gamma II, has generated.
It has reached recorded temperatures of 1,800 C, although Kinley
suspects it gets far hotter, even though it hasn’t been proved yet
because the Gamma II has melted the platinum thermocouples that
were used to measure the temperature. They can withstand
temperatures of 1,755 C. There were signs of vaporization when the
Gamma II melted iron recently, and that happens at 2,800 C.
As the Prometheus team continues to refine the Gamma II so that it
can melt larger amounts of metals, and do it safely, a smaller
version is undergoing six months of testing by Alberta Innovates —
Technology Futures, the former Alberta Research Council, in
Edmonton.
The foundry is looking at the potential to commercialize the Gamma
II by making it more automated and to provide solar heat in houses
by heating water that passes through pipes.
Kinley said he would also like to work with a university doing
research in high-temperature physics.
In the short term, the foundry plans to use the Gamma II to create
all its smaller castings, such as decorative door knockers,
souvenir dories and Bluenose II replicas, by this summer.
"It’s completely carbon neutral, and we’d also like to increase
the amount of metal it melts to displace our regular forms of
melting."
WO2008046187
TWO-STAGE SOLAR CONCENTRATING
SYSTEM.
Inventor(s): KINLEY PETER J [CA] + (PETER J.
KINLEY)
Applicant(s): LUNENBURG FOUNDRY &
ENGINEERIN
Classification: - international:
F24J2/10; F24J2/52; F24J2/00; F24J2/06 -
European: F24J2/14; F24J2/16; F24J2/18;
F24J2/54B4
Also published as: CA2562615 // EP2069694 // CN101460788 //
WO2008046187
Abstract -- An improved
solar concentrating system (100) uses a two-stage arrangement of
mirrors wherein the rays of the sun are reflected and concentrated
to a point focus. The solar concentrator ( 100) may be used to
increase the temperature of a substance such as metal, for use in
a variety of applications including the melting of metals in a
foundry furnace. The solar concentrating system (100) comprises at
least two single-curved parabolic mirrors (10, 20) connected in an
operable arrangement. The rays of the sun are reflected from a
first single-curved parabolic mirror ( 10) to a second
single-curved parabolic mirror (20). The plane of symmetry of the
second single-curved parabolic mirror is arranged substantially
orthogonal to the plane of symmetry of the first single-curved
parabolic mirror thereby concentrating the rays of the sun to a
point focus.
FIELD OF INVENTION
The present invention relates to a solar concentrator. In
particular, the present invention relates to a two-stage solar
concentrating system wherein the rays of the sun may be reflected
and concentrated to a desired focus- optionally, a square focus.
More particularly, the present invention relates to a two-stage
solar concentrating system wherein the rays of the sun are
reflected and concentrated to a point focus. Such a solar
concentrator may be used to increase the temperature of a
substance such as, for example, metal, for use in a variety of
applications including, inter alia, melting of metals in a
foundry.
BACKGROUND OF THE INVENTION
As the world- wide demand for energy increases exponentially,
there is a heavy burden placed on traditional sources of energy,
such as non-renewable fossil-based fuels. The price of crude oil
has shown significant historical fluctuations. The spiraling cost
of crude oil in recent years adversely effects the bottom-line of
many small and medium scale energy- intensive industries such as
foundries and the like. Therefore, alternate sources of energy,
e.g., solar power, have become increasingly attractive in recent
times. There is an environmental benefit to adopting cleaner
energy sources as reduction of burning of fossil fuels helps to
reduce greenhouse gas emissions
Solar energy technology has developed significantly since the
ancient Greek civilization learned the art of concentrating sun's
rays. Over the years, solar energy research has helped develop
systems that have improved efficiency and are more economical.
However, a dearth of information, materials, complexity, and
manufacturing skills remain an impediment to large-scale
production and utilization of this abundantly available energy
source.
Solar concentrators are characterized and classified based on
several criteria including the means of concentration: reflection
or refraction; type of focusing: point, line, or non- focusing;
type of concentrator: fixed or tracking concentrator; and, type of
receiver: fixed or tracking receiver. As will be described and
illustrated hereinafter, there are three primary types of
reflective solar concentrating systems based on the type of
focusing they produce, viz. , (a) parabolic trough concentrators
that produce line focus; (b) central receiver-type concentrators
that concentrate sunlight onto distant and centralized towers;
and, (c) parabolic dish concentrators that produce a point focus.
Based on the end application, the different types of solar
concentrators are employed to achieve optimum results. For
example, the parabolic trough concentrators are employed to
produce electricity and heat. However, troughs have a low maximum
solar concentration, high receiver heat loss, and are expensive.
Central receiver-type concentrators are typically employed in
large scale applications for electricity generation and require
vast real-estate for proper deployment and are thus not economical
for small and medium-scale industries. On the other hand,
parabolic dish concentrators are highly efficient in concentrating
the sun's rays. The biggest impediment to parabolic dish
concentrators include, inter alia, the prohibitive costs
associated with compound and complex reflector curves and
expensive mirror substrates.
In a typical solar concentrating system used in furnace
applications, a high energy density solar radiation is provided to
a target receiver, thus raising the temperature of the target.
Depending on the degree of concentration, the optical properties
(solar absorption and radiation) of the target surface, the system
may be utilized to melt a target surface, thus forming a solar
furnace.
Over the years attempts have been made to design and construct
solar concentrators that provide point focus (high solar
concentration) with minimum complexity and cost. United States
Patent No. 5,374,317 (Lamb et al.) discloses a multiple reflector
concentrator solar electric power system. In this system, the
sun's rays first reach a plane of individual primary reflectors
(which may be flat or curved). The primary reflectors then reflect
the solar radiation to the location of secondary reflectors (which
may again be flat or curved) and are then passed through to the
photovoltaic component. The system disclosed by Lamb et al. uses a
large number of components other than primary and secondary
reflectors such as tertiary reflectors, optional cover plates, and
heat dissipation components particularly suited for solar power
generation. This results in a system that is complex and
expensive.
United States Patent No. 6,530,369 (Yogev et al.) also describes a
system comprising two reflectors that are successively arranged
along an optical path of the system so that the first of the two
reflectors reflects the radiation towards the second reflector.
The concentrated radiation from the second reflector is directed
to a solar receiver. However, the second reflector is realized as
a tower reflector. As discussed earlier, central receiver-type
concentrators are typically employed in large scale applications
for electricity generation and require vast real-estate for proper
deployment and are thus not economical for small and medium-scale
industries.
International Patent Publication No. WO 2005/022047 A2 (Shifman)
discloses a solar energy utilization unit comprising a solar
radiation concentrating component and a solar energy receiving
component. The concentrating component comprises a concave primary
reflector and a convex secondary reflector, for concentrating
incident solar radiation and forwarding the concentrated radiation
into the receiving component. However, the reflectors are
dish-shaped and require high precision curved surfaces for
obtaining proper concentration effects.
United States Patent No. 4,784,700 (Stern et al.) describes a
point focus solar concentrator which uses various geometries of
cylindrical reflector strips as primary and secondary reflectors
to simulate a point focus by overlapping the line foci of each
segment at a coincident point. Although, the Stern et al. device
uses cylindrical rather than dish- shaped parabolic mirrors that
are easier to form and polish since they have a simple curvature,
the arrangement of the reflector strips in a Fresnel-type mirror
arrangement requires high manufacturing skills and therefore
increases its cost.
United States Patent No. 3,118,437 (Hunt) discloses a system of
two reflective surfaces or two sets of reflective surfaces facing
each other in an arrangement that causes all rays striking the
first reflective surface to converge onto a substantially one
point or limited area. Although Hunt discusses a system of two
reflective surfaces, wherein the effective axes of curvature of a
second surface or set of surfaces are being normal to the
effective axes of curvature of the first surface or set of
surfaces, the practical embodiments of Hunt's reflective system
are complex and require elaborate infrastructure, such as, for
example, carriages and tracks.
There is accordingly a need for an improved solar concentrating
system that overcomes the limitations associated with using
complex construction requiring high degree of skills. Moreover,
there is a need for an improved solar concentrating system wherein
the prohibitive costs associated with manufacture and deployment
of a traditional solar concentrating system are minimized thereby
making it attractive for use by small and medium scale
energy-intensive industries.
SUMMARY OF THE INVENTION
An object of the present invention is thus to provide an improved
solar concentrating system using a two-stage construction wherein
the rays of the sun are reflected and concentrated to a point
focus. Such a solar concentrator may be used to increase the
temperature of a substance such as metal, for use in a variety of
applications including melting of metals in a foundry furnace.
According to an aspect of the present invention, there is provided
, a solar radiation concentrating system comprising: a first
single-curved reflective surface and a second single- curved
reflective surface, said system including a mounting structure
associated therewith, said mounting structure being so arranged as
to cause variance between said first and second curved reflective
surface, wherein the rays of the sun are reflected from the first
single-curved reflective surface to the second single-curved
reflective surface, and wherein the principal plane of symmetry of
the first reflective surface is arranged substantially orthogonal
to the principal plane of symmetry of the second reflective
surface, thereby concentrating the rays of the sun to a point
focus.
According to another aspect of the present invention, there is
provided, a solar radiation concentrating system comprising: one
or more than one first single-curved reflective surface and one or
more than one second single-curved reflective surface; and a
mounting structure, the mounting structure comprising: a platform;
and a primary and secondary boom mounted to the platform, wherein
the primary boom and the secondary boom are hingedly attached so
as the angle between the first and second boom be varied and,
wherein the principal plane of symmetry of the first reflective
surface is arranged substantially orthogonal to the principal
plane of symmetry of the second reflective surface.
The first single-curved reflective surface has a focal length
greater than that of the second single-curved reflective surface.
In one embodiment of the present invention the first and second
reflective surfaces are parabolic cylinders.
In another embodiment of the present invention, the single-curved
reflective surfaces are mounted on a support frame. The support
frame may be made of wood, steel, aluminum, thermoplastic,
composite materials, bronze alloy, copper based alloy or other
synthetic material.
In a preferred embodiment of the present invention the support
frame comprises means for accommodating the reflecting surface,
means for changing the curvature of the reflective surface, or
both thereof. In still another preferred embodiment of the present
invention the support frame comprises fasteners, stiffeners,
braces, or combinations thereof to maintain the shape of the
reflective surface and for preventing gravitational sag.
In still another preferred embodiment of the present invention the
reflective surface is made from polished stainless steel, mirrored
glass, polyester film (PET) sheets, preferably coated with
aluminum or synthetic material having a suitable refractive index
so that it may be effectively used for the mirror surfaces, or
combinations thereof.
In still another preferred embodiment of the present invention the
mounting structure comprises a support member for each reflective
surface, wherein the support member is provided with tilting means
to adjust its tilt angle. The support member preferably comprises
a sliding mechanism engaged with and movable along the first and
secondary boom.
In still another preferred embodiment of the present invention the
solar radiation concentrating system comprises a tilt angle
adjusting means and a folding and deploying means. Preferably the
tilt angle adjusting means comprises one or more winch &
pulley mechanisms, gear trains, hydraulic cylinders, or
combinations thereof. Preferably, the folding and deploying means
comprises one or more hydraulic cylinders or threaded rods for
effecting movement of the sliding mechanism, folding or deploying
the mounting structure, or combinations thereof.
In still another preferred embodiment of the present invention a
tension wire, chain, or rope and a pulley are used to adjust the
tilt angle of the reflective surfaces in connection with the
support member.
In still another preferred embodiment of the present invention the
solar radiation concentrating system comprises solar tracking
means for tracking the sun and maintaining the focus on a desired
position. The solar tracking means may comprise wedges, hinges,
castors, rails, bearings, foundation mounts, etc. and may be
actuated manually or by electric or hydraulic motors and
associated control devices.
In still another preferred embodiment of the present invention the
mounting structure sits on a trailer for ease of transportation.
The trailer preferably, but not limited to, comprises a trailer
chassis, a plurality of wheel supports attached to the trailer
chassis, a ground engaging wheel rotatably mounted to each of the
wheel supports, and a drawbar attached to the trailer and
projecting outwardly therefrom to a free end carrying a trailer
hitch adapted to be hitched to a tow bar for towing the trailer
chassis behind a vehicle. According to an aspect of the present
invention, there is provided a method for concentrating radiation
to a coincident focus comprising reflecting an incident radiation
off a first single-curved reflective surface onto a second
single-curved reflective surface, wherein the principal plane of
symmetry of the first single-curved reflective surface is arranged
substantially orthogonal to the principal plane of symmetry of the
second single-curved reflective, whereby the second single-curved
reflective surface concentrates the incident radiation to the
focus and wherein the first and second reflective surfaces are
interconnected by a mounting structure the mounting structure
comprising: a platform or base; and a primary boom, or a primary
boom and secondary boom operably associated with the platform,
wherein the primary boom and the secondary boom are adapted for
operable attachment, whereby the angles between the first and
second boom, and base may be selectively varied.
According to another aspect of the present invention there is
provided a method for concentrating radiation to a substantially
rectangular, cross sectional area comprising reflecting an
incident radiation off a first single-curved reflective surface
onto a second single-curved reflective surface, wherein the
principal plane of symmetry of the first single- curved reflective
surface is arranged substantially orthogonal to the principal
plane of symmetry of the second single-curved reflective, whereby
the second single-curved reflective surface concentrates the
incident radiation to the focus and wherein the substantially
rectangular, cross sectional area is defined by a plane orthogonal
to the principal axis of the second single-curved reflective
surface at an intermediate point between a vertex and the focus of
the second reflective surface and wherein the first and second
reflective surfaces are interconnected by a mounting structure the
mounting structure comprising: a platform, or base; and a primary
boom, or a primary boom and secondary boom operably associated
with the platform, wherein the primary boom and the secondary boom
are adapted for operable attachment, whereby the angles between
the first and second boom, and base may be selectively varied.
According to yet another aspect of the present invention there is
provided A method for concentrating radiation to a substantially
rectangular, cross sectional area comprising reflecting an
incident radiation off a first single-curved reflective surface
onto a second single-curved reflective surface, wherein the
principal plane of symmetry of the first single- curved reflective
surface is arranged substantially orthogonal to the principal
plane of symmetry of the second single-curved reflective, whereby
the second single-curved reflective surface concentrates the
incident radiation to the focus and wherein the substantially
rectangular, cross sectional area is defined by a plane orthogonal
to the principal axis of the second single-curved reflective
surface at a point situated after the focus of the second
reflective surface and wherein the first and second reflective
surfaces are interconnected by a mounting structure the mounting
structure comprising: a platform or base; and a primary boom, or a
primary boom and secondary boom operably associated with the
platform, wherein the primary boom and the secondary boom are
adapted for operable attachment, whereby the angles between the
first and second boom, and base may be selectively varied.
According to another aspect of the present invention, there is
provided a method for forming single-curved mirrors from polished
sheets comprising bending the polished sheets into a single-curved
shape and supporting the bent polished sheets in the single-curved
shape by support frames for use in a solar concentrating system.
In other preferred embodiments the reflective surfaces may be
formed into a curve, preferably a parabolic curve, by applying
opposite compression forces at the ends thereof, the compression
forces may be applied by using, for example, tension wires. In
another preferred embodiment the reflective surfaces may be formed
into a curve by means of, for example, curved slots. In still
another preferred embodiment the reflective surface may be formed
into a curve using gravity sag. When silvered mylar is used, the
reflective surface may be formed into a curve, for example, by
slinging the silvered mylar sheet by cords from supports at each
end thereof (catenary method).
According to a further aspect of the present invention, there is
provided a solar concentrating kit comprising at least two
single-curved parabolic mirrors and a corresponding number of
support frames and, optionally, a mounting structure.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will be further described
with reference to the accompanying drawings, in which:
Fig. 1 is a representation
of different types of conventional solar concentrating systems
based on the type of focusing; (a) parabolic trough concentrator;
(b) central receiver concentrator; and (c) parabolic dish
concentrator;
Fig. 2 is a ray diagram
illustrating the principle of a two sheet mirror solar
concentrating system;
Fig. 3 is a schematic
representation of an embodiment of the two-stage solar
concentrating system according to the present invention;
Fig. 4 is a schematic
representation of another embodiment of the two-stage solar
concentrating system according to the present invention.
Fig. 5 is a schematic representation of an example of a
two-stage solar concentrating system according to the present
invention mounted on a trailer;
Fig. 6 is a schematic
representation of an example of a frame support according to the
present invention;
Fig. 7 is a
cross-sectional view of a receiver/target according to the present
invention;
Fig. 8 is a schematic
representation of an example of a two-stage solar concentrating
system according to the present invention mounted on a watercraft;
and
Fig. 9 is a top side elevational view of an exemplary
cigarette lighter using the two- stage solar concentrating system
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Fig. 1 shows three primary types of reflective solar concentrating
systems based on the type of focusing they produce, viz. , (a)
parabolic trough concentrators that produce line focus; (b)
central receiver-type concentrators that concentrate sunlight onto
distant and centralized towers; and, (c) parabolic dish
concentrators that produce a point focus. The underlying principle
of a two-stage solar concentrating system is illustrated in
Fig. 2. A two-stage solar concentrating system comprises two
single-curved mirrors (1, 2) curved in a parabolic shape so that
the rays of the sun are reflected and concentrated to a point
focus at a location (3). The two mirrors have two different focal
lengths. The primary mirror (1) has a long focal length and the
secondary mirror (2) has a short focal length. The rays of the sun
are concentrated to a line focus by the primary mirror (1). The
secondary mirror (2), with its plane of symmetry substantially
orthogonal to that of the primary mirror (1), then intersects and
concentrates the reflection from the primary mirror ( 1 ) so that
the total reflected rays converge to a point focus at the target
location (3). The secondary mirror (2) is located a distance away
from the focal point of the primary mirror (1) that is equal to
focal length of the secondary mirror (2).
Fig. 3 shows an exemplary embodiment of the two-stage solar
concentrating system (100) according to the present invention. A
first sheet mirror and a second sheet mirror are bent/curved into
first and second single-curved parabolic mirrors (10, 20) by a
first support frame (15) and a second support frame (25),
respectively. The support frames (15, 25) are constructed such
that the focal length of the first single-curved parabolic mirror
( 10) is longer than focal length of the second single-curved
parabolic mirror (20). The second single-curved parabolic mirror
(20) is located at a distance equal to its focal length in front
of the point of focus (line focus) of the first single-curved
parabolic mirror (10) so as to maximize the incidence of the
reflected radiation from the first single-curved parabolic mirror
(10). The rays of the sun (shown by dashed lines) are concentrated
to a line focus by the first single- curved parabolic mirror (10).
The second single-curved parabolic mirror (20), with its plane of
symmetry substantially orthogonal to that of the first
single-curved parabolic mirror (10), intersects and concentrates
the reflection from the first single-curved parabolic mirror (10)
to a point focus in the vicinity of a target (35). The first and
second support frame (15, 25) may be mounted on a solar tracking
means, such as heliostats, to maintain orientation with the sun
over time (not shown). In a preferred embodiment the first and
second support frame (15, 25) are made of wood, steel, aluminum,
plastic, composite materials, bronze alloy, copper based alloy, or
combinations thereof. The first and second support frame (15, 25)
may comprise means for accommodating the first and second
single-curved parabolic mirrors (10, 20), means for changing the
curvature of the first and second single-curved parabolic mirrors
(10, 20), or both thereof. In a preferred embodiment the support
frames (15, 25) comprise fasteners, stiffeners, braces, curved
slots, or combinations thereof for controlling the curvature of
the mirrors and for preventing gravitational sag. In still a
preferred embodiment of the two-stage solar concentrating system
according to the present invention the first and second support
frame (15, 25) may be mounted each on primary and secondary booms
(11) and (12), respectively. The primary and secondary boom (11,
12) may be, optionally, mounted to a platform (13). However, the
primary and secondary boom (11, 12) may be supported by any other
supporting structure envisaged by a skilled artisan. The primary
and secondary boom (11, 12) are attached, optionally, by means of
a hinge mount (28) so as the angles between the first and second
boom (11, 12) and the platform (13) be selectively varied so as to
track the rays of the sun and keep the point focus on the target
(35). Any means for manual and/or automatic variance of the angle
between the first and second boom (11, 12) may be used,
optionally, operably connected with sun tracking means and/or
indicia, to cause adjustment of the relative position of the
mirrors with respect to each other and the sun so as to produce a
coincident and/or a square focus according to the present
invention. In the embodiment illustrated in Fig. 3, the first
single-curved parabolic mirror (10) is shown to have its plane of
symmetry substantially parallel to the ground while the second
single-curved parabolic mirror (20) is shown to have its plane of
symmetry substantially orthogonal to the ground. However, any
other orientation of the two mirrors may be employed as long as
the planes of symmetries of the two mirrors are substantially
orthogonal to each other and the second single-curved parabolic
mirror (20) receives and further concentrates the sun rays
reflected from the first single-curved parabolic mirror (10) to a
point focus in the vicinity of the target (35). The size (area) of
the first single-curved parabolic mirror may be chosen in
accordance with the amount of energy needed. The continuous curved
mirror surfaces of the two-stage solar concentrating system
according to the present invention yield a very hot point focus.
For example, a 4ft (width) x 8ft (height) first single-curved
parabolic mirror (10) and an 8ft (width) x 4ft (height) second
single-curved parabolic mirror (20) arranged in accordance with
the present invention, resulted in a 4in x 4in square focus area
providing a concentration ratio of approximately 300:1. The
highest temperature recorded was 542[deg.] C. This temperature was
sufficient to melt Babbitt metal.
In another embodiment of the present invention, a plurality of
first (primary) and second (secondary) single-curved mirrors may
be employed to increase the concentration of solar energy. In an
exemplary embodiment Fig. 3 shows three first (primary)
single-curved mirrors (10) with support frames (15) and one second
(secondary) single-curved mirror (20) with support frame (25).
However, it is to be understood that the number of primary and/or
secondary mirrors may be suitably adapted, by a person skilled in
the field pertaining to the present invention, so as to fit
specific applications of the two-stage solar concentrating system.
However, it is to be understood that the underlying optical
principle of concentrating the sun rays with use of a two-stage
arrangement of mirrors remains the same. For example, a number of
primary mirrors may be arranged to focus through a single
secondary mirror thereby increasing the effective concentration
ratio. The plurality of primary mirrors may be mounted on a
supporting frame and made to track the sun directly as a single
unit in order to cast their combined reflection on a secondary
mirror and then onto a point focus. Alternatively, the secondary
mirror may also be mounted on the supporting frame together with
the primary mirrors. Additionally, different combinations of focal
lengths of the primary and secondary mirrors may also be employed.
The solar collector can be multi-purpose. That is more than one
receiver can me mounted so that the concentrated beam may be
redirected simply by changing the angle of the secondary mirror.
Different receivers can be installed for different purposes, such
as: melting, steam generation, heat extraction, electrical
generation, cooking, or others. Each receiver would have a
standard mount so that they would be modular. Different receivers
may be plugged in to the apparatus thus changing its application.
Furthermore, due to mirror aberration and/or mirror
irregularities, there may be a hot spot near the middle of the
focus area while peripheral areas are cooler. The depth of the
focus field may also be varied with different mirror arrangements.
For example, there may be a warm spot before the focus, a hot spot
in the center of the focus and a relatively cooler spot after the
focus. Thus, the temperature of the target may be controlled by
locating the target slightly off the point focus of the two-stage
solar concentrating system. Multiple mirror systems may spread the
energy to a number of targets within the same apparatus. Tertiary
focusing mirrors may also be employed to increase the focus. An
example of a tertiary focusing mirror is an internally mirrored
cone or a parabolic dish concentrator.
In the example described earlier, polished 20-gauge stainless
steel sheets were used to form the continuously curved cylindrical
parabolic mirrors (10, 20). Other materials such as mirrored
glass, silvered mylar(TM) or polyester film (PET) sheets,
preferably coated with aluminum or synthetic material having a
suitable refractive index so that it may be effectively used for
the mirror surfaces.
The first and second support frame (15, 25) were made from plywood
frame in the experimental example (see Fig.6). However, frames
using aluminum extrusions, wood, steel, plastic, or other suitable
natural and synthetic material may also be used. The mirrors are
held in a cylindrical parabolic shape by inserting the two
opposing edges of the mirror sheets (usually the long sides) into
a curved slot (61) provided in a side panel (63) of the support
frame (15). The support frame may have separate slot holders that
are independent of the support frame for changing the curvature of
the mirror surfaces. Additional braces may be employed for
preventing gravitational sag and to maintain proper cylindrical
parabolic form of the mirrors. The support frame may be made up of
simple beam elements, or may be combined into a truss-like
structure. Fig. 6 shows an example of a support structure (15)
with adjustable focal length made of plywood. The support
structure is made of a back panel (62), side panels (63) and top
and bottom panels (64). The side panels (63) are provided with
separate slotted holders that are independent of the support frame
(15) so as to allow adjustment of the curvature of the reflective
sheet. Other braces may be employed to keep the ruled surface
elements straight to prevent gravitational sag and maintain the
cylindrical form of the reflective sheet. For example, diagonal
braces (65) are provided on the back panel for support. In
addition, hinges (66) may be provided to allow relocation of the
reflective sheet. It is to be noted that the main consideration in
the construction of the support frame is that it should be strong
enough to support the weight of the mirrors as well as possible
wind loads to maintain the desired alignment.
Fig. 4 shows an exemplary embodiment of a truss-like structure,
wherein a plurality of first single-curved mirrors (10) and a
second single-curved mirror (20) are mounted on a ring base (16).
As shown in Fig. 4 the truss-like structure may comprise means for
adjusting the relative position of the single-curved mirrors (10,
20) as well as means for retaining the mirrors in the desired
position. Other embodiments may be envisaged featuring, inter
alia, high hinge mount and balance beam boom connecting primary
and secondary mirrors. The two-stage solar concentration system
according to the present invention may further comprise solar
tracking means to adjust the orientation of the system to
correspond with local height and direction of sun at a particular
time. The tracking means may comprise wedges, hinges, castors,
rails, bearings, foundation mounts, etc. and may be actuated
manually or by electric or hydraulic apparatus and associated
control devices. Another embodiment of the two-stage solar
concentrating system according to the present invention mounted on
a trailer (75) is illustrated in Fig. 5. The trailer (75) may be
fitted with a pivot (30) and adjustable castors (29) and wheels
(85) so that it may rotate sideways to track the sun through the
day. Variance of the angles between the first boom (11) and the
second boom (12) and between the booms (11, 12) and platform/base
(14) as well as the pan and tilt angles of mirrors may be achieved
by a combination of winch and pulley mechanism (31 ) operably
interconnected to the frame support (15,20) and the booms (11, 12)
and the platform/base (14) by a tension wire, chain, or rope (95).
The position of the first and second support frame (15, 20) may be
adjusted along the boom (11, 12) by use of a sliding mechanism
engaged with and slidable along the first and second boom (11,
12). In an exemplary embodiment the sliding mechanism employs a
sliding carriage (23). In a similar manner the relative position
of the receiver (36) containing the target (35), in respect of the
first and second single-curved mirror (10, 20), may also be
adjusted by use of a sliding mechanism or any other adjusting
means known to a skilled artisan in the art pertaining to the
present invention.
The tilt angle of mirrors may be adjusted through the day to
provide desired focus arrangement. The individual elements of the
two-stage solar concentrating system may be folded, stacked and
packaged for transportation and erected in kit form for
application in many different locations. The trailer mounted units
may be towed to remote locations, unfolded and put into use.
An exemplary embodiment of a receiver (36) containing a melting
pot or target (35) is shown in Fig. 7. The exemplary receiver (36)
shown in Fig. 7 is shaped like a cube with one vertical side (37)
being made from a transparent material such as, for example, SiO2
or acrylic glass. The receiver (36) may have an insulation (38)
purposed to minimize thermal exchange between the target and the
environment. Any known insulation material may be used provided
that the various technical aspects known to person skilled in the
art such as the suitable thickness, reaction to high temperature,
means for attaching the insulation material to the wall of the
receiver, etc. are selected according to the design and purpose of
the specific application of the solar concentrating system of the
present invention. Different receiver and target designs should be
applied for melting solids, boiling liquids, or for electrical
production. Some targets may be vertical while others, horizontal
as the top of a pot. Receivers may or may not: be insulated, have
covers, be dish shaped, be movable or fixed and have valves for
control.
Although the solar concentrating system described herein has been
employed for concentrating solar energy for foundry applications,
the system may be employed for several other applications. The
applications of the two-sheet (cylindrical parabolic) mirror
focusing system are many and varied for wherever and whatever heat
energy is required. For example, the solar concentrating system
may be employed for providing thermal energy to space heating,
industrial processes, high temperature reduction of hazardous
wastes, metal extrusion forming, roll forming, surface treatment,
welding, fusing, annealing, or heat treatment of metals, and in
petrochemical industries. Applications may include thermal
industrial processes such as metal melting in foundry work for
metal casting, melting scrap for recycling or reduction of ores in
metal production. Units may be developed that serve the purpose of
metal welding, brazing or soldering. It is envisioned that the
solar concentrating system according to the present system may be
useful for processing oil sands and shale into usable oil products
with minimum emission of greenhouse gasses. It may be useful for
production of synthetic fuels using solar photochemical and/or
solar thermo-chemical processes and may include Hydrogen
production. The two-sheet (cylindrical parabolic) mirror focusing
system may be used for electrical production through a steam cycle
generating system, Sterling heat engine or, photovoltaic electric
generation systems. The two-sheet focusing system may be used for
space heating, domestically (home heating), institutional or
public space heating, whether the heat energy may be used right
away or stored in a thermal storage device for later use and/or
with heating ducts or thermal conduits to distribute the thermal
energy across a distance to other locations. The two-sheet
focusing system may be used for food processing, such as cooking
or drying. Barbecue sized units could be developed for backyard
applications on sunny days. The system may also be used in
cremation facilities. The two-sheet focus might be taught to
woodsmen or boy-scouts as a way to start a campfire. Small
hand-held units might be developed to provide a sort of novelty
cigarette lighter. For purposes of exemplification two
applications of the two-stage solar concentrating system are
illustrated in Figs. 8 and 9 and should not be construed as
restrictive in any way. Fig. 8 shows an exemplary application of
the two-stage solar concentrating system mounted on a barge to
allow tracking the sun through the day and concentrating the solar
radiation to a target area (35). A primary single-curved mirror
(10) is mounted on the barge (80) through legs (81). A secondary
single-curved mirror (20) is operably connected to the first
single- curved mirror (10) by one or more struts (82). The struts
may be attached directly to the barge and/or to the primary
mirror, preferably by means of a hinge mount (28). The struts are
provided at each end thereof with means to allow tilting and
movement of the mirrors. Preferably, but not limited to, the
mirrors are hingedly attached to the struts. In addition, means
for adjusting the relative position of the struts with respect to
the barge may be provided. Preferably, a sliding mechanism (83)
may be provided to allow horizontal movement of the struts with
respect to the barge. Solar tracking means may also be employed.
The position adjusting means and/or the solar tracking means may
comprise wedges, hinges, castors, rails, bearings, foundation
mounts, etc. and may be actuated manually or by electric or
hydraulic apparatus and associated control devices.
Fig. 9 shows another exemplary application of the two-stage solar
concentrating system. In particular, Fig.9 shows a cigarette
lighter (90) constructed according to the two- stage solar
concentrating system disclosed herein. The cigarette lighter (90)
may have a pedestal (91) as a base for a pillar (92). The pillar
(92) may be provided with a U-shaped structure (93) having
attached at the two ends thereof a horizontal arm (94) to which at
least one primary mirror and at least one secondary mirror may be
mounted in accordance with the present invention. The cigarette
lighter as described above may further comprise means for
adjusting the relative position of the single-curved mirrors (10,
20) as well as means for retaining the mirrors into a desired
position with a view to capturing solar radiation and
concentrating the radiation to an area so as to cause ignition.
Various modifications to the disclosed embodiments will be readily
apparent to those skilled in the art or science, and the general
principles defined herein may be applied to other embodiments and
applications without departing from the spirit and scope of the
invention. Thus, the present invention is not intended to be
limited to the embodiments disclosed, but is to be accorded the
widest scope consistent with the principles and features disclosed
herein. Accordingly, the principle of concentration and collection
of solar energy remain the same, only that is suitably chosen in
accordance with the end application.
The aforesaid description and drawings presented herein teach in
considerable detail workable embodiments within the broad concept
of the present invention. However, it is particularly noted that
the inventor has as a result of his experimental activity, testing
and further general development, arrived at possible additional
and alternative working structures, the specific operational
details will be readily discernible by a man skilled in the art.
Accordingly, the embodiments listed on the following 25 sheets of
drawings which include written footnotes to the drawings
identifying the subject matter thereof are presented as
alternative embodiments which are inextricably bound up in one and
the same inventive concept as the embodiments previously taught
herein.
INDUSTRIAL APPLICABILITY
The invention provides a solar concentrating system wherein the
rays of sun may be reflected and concentrated to a desired focus.
The solar concentrator may be used to increase the temperature of
substance such as, for example, metal, for use in a variety of
application including, e.g., melting of metals.
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