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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