US4154219A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Prismatic solar reflector apparatus and method of solar tracking
Assignee: Entech Inc
•
Filing: 1977-03-11
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Granted: 1979-05-15
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Expires: 1997-03-11
Abstract
Abstract A prismatic plate is mounted with its flat face exposed to the sun on a reflector panel for use in a solar energy collection system. The plate includes a plurality of triangular prisms with parallel longitudinal axes shaped to provide total internal reflection of incident light rays. Each prism has a cross section forming a right-angled isosceles triangle with the two equal-length, rear faces of the prism oriented at 45 degrees relative to the front face of the plate. The base of each prism forms or is parallel to a front plate surface which receives incident solar light rays. The rays are transmitted through the plate cross section without refraction in the plane of the cross section to be reflected from the two rear faces and back out the front face toward a solar receiver. The prism material has an index of refraction equal to or greater than the square root of two so that there is total internal reflection from the prism faces. The prismatic plate is mounted on a movable heliostat panel controlled by a tracking system to reflect to a solar receiver. The panel has a fixed axis directed toward a central receiver and a moving axis orthogonal to the fixed axis. The prismatic plate is mounted on the panel with the longitudinal axes of the prisms perpendicular to the moving axis. Tracking is accomplished by adjusting the panel orientation so that the plane of incidence of the incident solar rays is parallel to the longitudinal axes of the prisms and also so that the reflected solar rays intercept the receiver.
Inventors
- 👤 Youdhishthir P. Gupta
- 👤 Mark J. O'Neill
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 11:45
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/78; G01S3/782; G01S3/785; G01S3/786; G01S3/7861; F; F24; F24S; F24S23/00; F24S23/10; F24S23/70; F24S23/74; F24S23/80; F24S30/00; F24S30/40; F24S30/42; F24S30/425; G05; G05D; G05D3/00; F24S25/00; F24S25/10; Y; Y02; Y02E; Y02E10/00; Y02E10/40; Y02E10/47
Claims Analysis
Total Claims: 44
Claim 1
Independent Claim
124 words
Apparatus for reflecting and concentrating solar rays in a solar energy collection system, comprising a receiver for collecting said reflected solar rays, and a prism member having an index of refraction equal to or greater than the square root of two to provide total internal reflection of incident solar rays toward said receiver, said prism member including a first face for receiving the incident solar rays and transmitting the rays through the prism member, and a plurality of pairs of prism faces each pair being oriented at substantially 90 degrees relative to each other to totally reflect each transmitted ray back through said first face to the receiver in a plane of reflection parallel to the plane of incidence of the corresponding incident ray.
Claim 2
Dependent Claim
124 words
Apparatus for reflecting and concentrating solar rays in a solar energy collection system, comprising a receiver for collecting said reflected solar rays, and a prism member having an index of refraction equal to or greater than the square root of two to provide total internal reflection of incident solar rays toward said receiver, said prism member including a first face for receiving the incident solar rays and transmitting the rays through the prism member, and a plurality of pairs of prism faces each pair being oriented at substantially 90 degrees relative to each other to totally reflect each transmitted ray back through said first face to the receiver in a plane of reflection parallel to the plane of incidence of the corresponding incident ray.
Claim 3
Dependent Claim
47 words
The apparatus of claim 1 wherein said prism member comprises a unitary plate having a first transparent flat, front surface to receive the incident solar rays and a second prismatic rear surface, each said pair of prism faces forming an equal-sized right angle triangle in cross section.
Claim 4
Dependent Claim
49 words
The apparatus of claim 1 wherein said prism member comprises a plurality of separate triangular prisms having parallel longitudinal axes, the base of each prism lying along a common line to form said first face and the sides of each prism forming one of said pair of prism faces.
Claim 5
Dependent Claim
134 words
Apparatus for reflecting and concentrating solar rays in a solar power tower energy collection system, comprising a stationary receiver in a solar power tower for collecting said reflected solar rays, and a prismatic heliostat member having an index of refraction equal to or greater than the square root of two to provide total internal reflection of incident solar rays toward said receiver, said prismatic heliostat member including a first face for receiving the incident solar rays and transmitting the rays through the heliostat member, and a plurality of pairs of prism faces each pair being oriented at substantially 90 degrees relative to each other to totally reflect each transmitted ray back through said first face to the receiver in a plane of reflection parallel to the plane of incidence of the corresponding incident ray.
Claim 6
Dependent Claim
134 words
Apparatus for reflecting and concentrating solar rays in a solar power tower energy collection system, comprising a stationary receiver in a solar power tower for collecting said reflected solar rays, and a prismatic heliostat member having an index of refraction equal to or greater than the square root of two to provide total internal reflection of incident solar rays toward said receiver, said prismatic heliostat member including a first face for receiving the incident solar rays and transmitting the rays through the heliostat member, and a plurality of pairs of prism faces each pair being oriented at substantially 90 degrees relative to each other to totally reflect each transmitted ray back through said first face to the receiver in a plane of reflection parallel to the plane of incidence of the corresponding incident ray.
Claim 7
Dependent Claim
162 words
In a solar energy collection system for focusing the solar energy to reflect solar rays to a central location, the combination comprising a central receiver positioned at the central location to collect the focused solar energy, and a reflective surface for focusing the solar energy comprising a unitary transparent uncoated plate of material having an index of refraction equal to or greater than the square root of two, said plate having a smooth front surface, an intermediate thickness and a prism-shaped back surface, said back surface having a plurality of triangular prisms with parallel longitudinal axes, each prism having a cross section forming an isosceles, right-angle triangle with first and second sides oriented at substantially 45 degrees relative to the front surface, whereby solar rays incident to the front surface are transmitted through the intermediate thickness, totally internally reflected from the first side and the second side and transmitted back through the intermediate thickness and out the front surface to the receiver.
Claim 8
Dependent Claim
162 words
In a solar energy collection system for focusing the solar energy to reflect solar rays to a central location, the combination comprising a central receiver positioned at the central location to collect the focused solar energy, and a reflective surface for focusing the solar energy comprising a unitary transparent uncoated plate of material having an index of refraction equal to or greater than the square root of two, said plate having a smooth front surface, an intermediate thickness and a prism-shaped back surface, said back surface having a plurality of triangular prisms with parallel longitudinal axes, each prism having a cross section forming an isosceles, right-angle triangle with first and second sides oriented at substantially 45 degrees relative to the front surface, whereby solar rays incident to the front surface are transmitted through the intermediate thickness, totally internally reflected from the first side and the second side and transmitted back through the intermediate thickness and out the front surface to the receiver.
Claim 9
Dependent Claim
13 words
The apparatus of claim 5 wherein said plate material comprises extruded acrylic plastic.
Claim 10
Dependent Claim
177 words
In a solar energy collection system for focusing solar energy to reflect solar rays from a heliostat panel to a solar power tower, the combination comprising a central stationary receiver positioned in the solar power tower to collect the focused solar energy, and a reflective surface on the heliostat panel for focusing the solar energy comprising a unitary transparent uncoated plate of material having an index of refraction equal to or greater than the square root of two, said plate having a smooth front surface, an intermediate thickness and a prism-shaped back surface, said back surface having a plurality of triangular prisms with parallel longitudinal axes, each prism having a cross section forming an isosceles, right-angle triangle with first and second sides oriented at substantially 45 degrees relative to the front surface, whereby solar rays incident to the front surface are transmitted through the intermediate thickness, totally internally reflected from the first side and the second side and transmitted back through the intermediate thickness and out the front surface to the receiver of the solar power tower.
Claim 11
Dependent Claim
177 words
In a solar energy collection system for focusing solar energy to reflect solar rays from a heliostat panel to a solar power tower, the combination comprising a central stationary receiver positioned in the solar power tower to collect the focused solar energy, and a reflective surface on the heliostat panel for focusing the solar energy comprising a unitary transparent uncoated plate of material having an index of refraction equal to or greater than the square root of two, said plate having a smooth front surface, an intermediate thickness and a prism-shaped back surface, said back surface having a plurality of triangular prisms with parallel longitudinal axes, each prism having a cross section forming an isosceles, right-angle triangle with first and second sides oriented at substantially 45 degrees relative to the front surface, whereby solar rays incident to the front surface are transmitted through the intermediate thickness, totally internally reflected from the first side and the second side and transmitted back through the intermediate thickness and out the front surface to the receiver of the solar power tower.
Claim 12
Dependent Claim
150 words
In a solar energy collection system having a reflective surface for focusing the solar energy at a central location, and a solar receiver positioned at the central location to collect the focused solar energy, the improvement wherein said reflective surface comprises a prism member having an index of refraction equal to or greater than the square root of two to provide total internal reflection of incident solar rays, said prism member including a first face for receiving the incident solar rays and transmitting the rays through the prism member, and a plurality of pairs of prism faces each pair being oriented at substantially 45 degrees relative to the first face and at substantially 90 degrees relative to each other to totally reflect each transmitted ray back through said first face to the solar receiver in a plane of reflection parallel to the plane of incidence of the corresponding incident ray.
Claim 13
Dependent Claim
150 words
In a solar energy collection system having a reflective surface for focusing the solar energy at a central location, and a solar receiver positioned at the central location to collect the focused solar energy, the improvement wherein said reflective surface comprises a prism member having an index of refraction equal to or greater than the square root of two to provide total internal reflection of incident solar rays, said prism member including a first face for receiving the incident solar rays and transmitting the rays through the prism member, and a plurality of pairs of prism faces each pair being oriented at substantially 45 degrees relative to the first face and at substantially 90 degrees relative to each other to totally reflect each transmitted ray back through said first face to the solar receiver in a plane of reflection parallel to the plane of incidence of the corresponding incident ray.
Claim 14
Dependent Claim
152 words
A solar energy conversion system for intercepting, reflecting and collecting solar rays to generate useful energy comprising: reflecting means including a panel having a transparent front surface for receiving incident solar rays and a rear surface forming a plurality of prismatic faces having parallel longitudinal axes and being oriented for total internal reflection of the rays transmitted through the panel from the front surface to transmit the rays back through the front surface in a plane parallel to the plane of the incident solar rays; support means for carrying said panel and for orienting said panel to maintain the plane of incidence of the solar rays parallel to the longitudinal axes of the prismatic faces to transmit the reflected rays in a predetermined direction; and receiver means positioned to intercept the rays transmitted in said predetermined direction to absorb the rays and convert the solar energy from the rays to usable energy.
Claim 15
Dependent Claim
152 words
A solar energy conversion system for intercepting, reflecting and collecting solar rays to generate useful energy comprising: reflecting means including a panel having a transparent front surface for receiving incident solar rays and a rear surface forming a plurality of prismatic faces having parallel longitudinal axes and being oriented for total internal reflection of the rays transmitted through the panel from the front surface to transmit the rays back through the front surface in a plane parallel to the plane of the incident solar rays; support means for carrying said panel and for orienting said panel to maintain the plane of incidence of the solar rays parallel to the longitudinal axes of the prismatic faces to transmit the reflected rays in a predetermined direction; and receiver means positioned to intercept the rays transmitted in said predetermined direction to absorb the rays and convert the solar energy from the rays to usable energy.
Claim 16
Dependent Claim
35 words
The system of claim 9 wherein said support means comprises a heliostat structure and tracking system and wherein said receiver means comprises a central tower having a stationary receiver at the top of the tower.
Claim 17
Dependent Claim
42 words
The system of claim 9 wherein said support means comprises a parabolic cylindrically-shaped trough structure and tracking system and wherein said receiver means comprises a linear absorbing receiver spaced from and running parallel to the longitudinal axis of the parabolic trough structure.
Claim 18
Dependent Claim
37 words
The system of claim 9 wherein said support means comprises a paraboloidal-shaped structure and tracking system and wherein said receiver means comprises a point absorbing receiver centrally located and spaced from the center of the paraboloidal-shaped structure.
Claim 19
Dependent Claim
177 words
A solar energy conversion system for intercepting, reflecting and collecting solar rays to generate useful energy comprising: reflecting means including a panel having a transparent front surface for receiving incident solar rays and a rear surface forming a plurality of prismatic faces having parallel longitudinal axes and being oriented for total internal reflection of the rays transmitted through the panel from the front surface to transmit the rays back through the front surface in a plane parallel to the plane of the incident solar rays; support means for carrying said panel and for orienting said panel to maintain the plane of incidence of the solar rays parallel to the longitudinal axes of the prismatic faces to transmit the reflected rays in a predetermined direction, said support means comprising a paraboloidal-shaped structure and tracking system; and receiver means comprising a point absorbing receiver centrally located and spaced from the center of the paraboloidal-shaped structure to intercept the rays transmitted in said predetermined direction to absorb the rays and convert the solar energy from the rays to usable energy.
Claim 20
Dependent Claim
177 words
A solar energy conversion system for intercepting, reflecting and collecting solar rays to generate useful energy comprising: reflecting means including a panel having a transparent front surface for receiving incident solar rays and a rear surface forming a plurality of prismatic faces having parallel longitudinal axes and being oriented for total internal reflection of the rays transmitted through the panel from the front surface to transmit the rays back through the front surface in a plane parallel to the plane of the incident solar rays; support means for carrying said panel and for orienting said panel to maintain the plane of incidence of the solar rays parallel to the longitudinal axes of the prismatic faces to transmit the reflected rays in a predetermined direction, said support means comprising a paraboloidal-shaped structure and tracking system; and receiver means comprising a point absorbing receiver centrally located and spaced from the center of the paraboloidal-shaped structure to intercept the rays transmitted in said predetermined direction to absorb the rays and convert the solar energy from the rays to usable energy.
Claim 21
Dependent Claim
159 words
A solar power tower energy conversion system for intercepting, reflecting and collecting solar rays to generate useful energy comprising: reflecting means including a panel having a transparent front surface for receiving incident solar rays and a rear surface forming a plurality of prismatic faces having parallel longitudinal axes and being oriented for total internal reflection of the rays transmitted through the panel from the front surface to transmit the rays back through the front surface in a plane parallel to the plane of the incident solar rays; heliostat structure for carrying said panel and for orienting said panel to maintain the plane of incidence of the solar rays parallel to the longitudinal axes of the prismatic faces to transmit the reflected rays in a predetermined direction; and a central tower having a stationary receiver positioned to intercept the rays transmitted in said predetermined direction to absorb the rays and convert the solar energy from the rays to usable energy.
Claim 22
Dependent Claim
159 words
A solar power tower energy conversion system for intercepting, reflecting and collecting solar rays to generate useful energy comprising: reflecting means including a panel having a transparent front surface for receiving incident solar rays and a rear surface forming a plurality of prismatic faces having parallel longitudinal axes and being oriented for total internal reflection of the rays transmitted through the panel from the front surface to transmit the rays back through the front surface in a plane parallel to the plane of the incident solar rays; heliostat structure for carrying said panel and for orienting said panel to maintain the plane of incidence of the solar rays parallel to the longitudinal axes of the prismatic faces to transmit the reflected rays in a predetermined direction; and a central tower having a stationary receiver positioned to intercept the rays transmitted in said predetermined direction to absorb the rays and convert the solar energy from the rays to usable energy.
Claim 23
Dependent Claim
28 words
The system of claim 14 wherein said panel is curved along the longitudinal axes of the prisms to enhance focusing of said solar rays on said stationary receiver.
Claim 24
Independent Claim
154 words
A system for use in the reflection of solar rays to a solar energy receiver, comprising: a reflector panel for intercepting the solar rays and reflecting the intercepted solar rays to the receiver, said panel having a transparent front surface for receiving the solar rays and a back surface forming a plurality of prisms having parallel longitudinal axes and having a configuration to totally internally reflect to the solar energy receiver a light ray transmitted through the panel from the front surface having a plane of incidence parallel to the longitudinal axes of the prisms; support means for mounting said reflector panel and for rotating said panel about multiple axes; and tracking means for controlling said support means to maintain the orientation of said panel so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms and the reflected solar rays intercept the solar energy receiver.
Claim 25
Independent Claim
154 words
A system for use in the reflection of solar rays to a solar energy receiver, comprising: a reflector panel for intercepting the solar rays and reflecting the intercepted solar rays to the receiver, said panel having a transparent front surface for receiving the solar rays and a back surface forming a plurality of prisms having parallel longitudinal axes and having a configuration to totally internally reflect to the solar energy receiver a light ray transmitted through the panel from the front surface having a plane of incidence parallel to the longitudinal axes of the prisms; support means for mounting said reflector panel and for rotating said panel about multiple axes; and tracking means for controlling said support means to maintain the orientation of said panel so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms and the reflected solar rays intercept the solar energy receiver.
Claim 26
Dependent Claim
27 words
The system of claim 16 wherein said prisms form isosceles, right-angle triangles in cross section, the sides being oriented at 45 degrees relative to the front surface.
Claim 27
Dependent Claim
18 words
The system of claim 16 wherein said panel is substantially flat for use in a heliostat reflector system.
Claim 28
Dependent Claim
28 words
The system of claim 16 wherein said panel is slightly curved along the longitudinal axes of the prisms to provide focusing of said solar rays at the receiver.
Claim 29
Dependent Claim
30 words
The system of claim 16 wherein said panel is substantially curved along the longitudinal axes of the prisms to form a parabolic cylinder for use in a trough collector system.
Claim 30
Dependent Claim
28 words
The system of claim 16 wherein said panel is curved along the longitudinal axes of the prisms to form a paraboloid for use in a paraboloidal concentrator system.
Claim 31
Dependent Claim
64 words
The system of claim 16 wherein said support means comprises means for rotating the panel about a first fixed axis directed toward the receiver, and means for rotating the panel about a second variable axis orthogonal with the first fixed axis, and wherein said panel is mounted on said support means with the longitudinal axes of the prisms perpendicular to the second variable axis.
Claim 32
Dependent Claim
82 words
The system of claim 16 wherein said tracking means comprises data processing means for computing the position of the sun relative to said panel and for generating a first signal representative of the computed position of the sun, error correcting means for sensing the position of the sun relative to said panel and for generating a second signal representative of the actual position of the sun, and control means for actuating said support means in response to said first and second signals.
Claim 33
Independent Claim
171 words
A system for use in the reflection of solar rays to a solar energy receiver, comprising: a reflector panel for intercepting the solar rays and reflecting the intercepted solar rays to the receiver, said panel having a transparent front surface for receiving the solar rays and a back surface forming a plurality of prisms having parallel longitudinal axes and having a configuration to totally internally reflect a light ray transmitted through the panel from the front surface having a plane of incidence parallel to the longitudinal axes of the prisms, said panel being curved along the longitudinal axes of the prisms to form a paraboloid for use in a paraboloidal concentrator system; support means for mounting said reflector panel and for rotating said panel about multiple axes; and tracking means for controlling said support means to maintain the orientation of said panel so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms and the reflected solar rays intercept the solar energy receiver.
Claim 34
Independent Claim
171 words
A system for use in the reflection of solar rays to a solar energy receiver, comprising: a reflector panel for intercepting the solar rays and reflecting the intercepted solar rays to the receiver, said panel having a transparent front surface for receiving the solar rays and a back surface forming a plurality of prisms having parallel longitudinal axes and having a configuration to totally internally reflect a light ray transmitted through the panel from the front surface having a plane of incidence parallel to the longitudinal axes of the prisms, said panel being curved along the longitudinal axes of the prisms to form a paraboloid for use in a paraboloidal concentrator system; support means for mounting said reflector panel and for rotating said panel about multiple axes; and tracking means for controlling said support means to maintain the orientation of said panel so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms and the reflected solar rays intercept the solar energy receiver.
Claim 35
Independent Claim
176 words
A system for use in the reflection of solar rays to a solar energy receiver in a solar power tower, comprising: a heliostat reflector panel for intercepting the solar rays and reflecting the intercepted solar rays to the receiver, said panel having a transparent front surface for receiving the solar rays and a back surface forming a plurality of prisms having parallel longitudinal axes and having a configuration to totally internally reflect to the solar energy receiver a light ray transmitted through the panel from the front surface having a plan of incidence parallel to the longitudinal axes of the prisms; support means for mounting said heliostat reflector panel and for rotating said panel about multiple axes; and tracking means for controlling said support means, including means for orienting said heliostat panel so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms and means for orienting said heliostat panel so that the reflected solar rays are intercepted by the solar energy receiver of said solar power tower.
Claim 36
Independent Claim
176 words
A system for use in the reflection of solar rays to a solar energy receiver in a solar power tower, comprising: a heliostat reflector panel for intercepting the solar rays and reflecting the intercepted solar rays to the receiver, said panel having a transparent front surface for receiving the solar rays and a back surface forming a plurality of prisms having parallel longitudinal axes and having a configuration to totally internally reflect to the solar energy receiver a light ray transmitted through the panel from the front surface having a plan of incidence parallel to the longitudinal axes of the prisms; support means for mounting said heliostat reflector panel and for rotating said panel about multiple axes; and tracking means for controlling said support means, including means for orienting said heliostat panel so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms and means for orienting said heliostat panel so that the reflected solar rays are intercepted by the solar energy receiver of said solar power tower.
Claim 37
Dependent Claim
29 words
The system of claim 25 wherein said panel is curved along the longitudinal axes of the prisms to enhance focusing of said solar rays on said solar energy receiver.
Claim 38
Independent Claim
83 words
A method of tracking the sun with a reflector panel having a plurality of prisms with parallel longitudinal axes to reflect incident solar rays to a solar energy receiver, comprising: orienting the panel relative to the incident solar rays so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms to totally internally reflect the rays; and orienting the panel relative to the receiver so that the receiver intercepts the totally internally reflected solar rays.
Claim 39
Independent Claim
83 words
A method of tracking the sun with a reflector panel having a plurality of prisms with parallel longitudinal axes to reflect incident solar rays to a solar energy receiver, comprising: orienting the panel relative to the incident solar rays so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms to totally internally reflect the rays; and orienting the panel relative to the receiver so that the receiver intercepts the totally internally reflected solar rays.
Claim 40
Dependent Claim
57 words
The method of claim 27 wherein the panel is oriented relative to the receiver by rotating the panel about a first axis until the receiver lies within a plane of reflection of the totally internally reflected solar rays, and then rotating the panel about a second axis until the receiver intercepts the totally internally reflected solar rays.
Claim 41
Independent Claim
93 words
A method of tracking the sun with a heliostat reflector panel having a plurality of prisms with parallel longitudinal axes to reflect incident solar rays to a stationary solar energy receiver in a solar power tower, comprising: orienting the heliostat panel relative to the incident solar rays so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms to totally internally reflect the rays; and orienting the heliostat panel relative to the stationary receiver so that the receiver intercepts the totally internally reflected solar rays.
Claim 42
Independent Claim
93 words
A method of tracking the sun with a heliostat reflector panel having a plurality of prisms with parallel longitudinal axes to reflect incident solar rays to a stationary solar energy receiver in a solar power tower, comprising: orienting the heliostat panel relative to the incident solar rays so that the plane of incidence of the solar rays is parallel to the longitudinal axes of the prisms to totally internally reflect the rays; and orienting the heliostat panel relative to the stationary receiver so that the receiver intercepts the totally internally reflected solar rays.
Claim 43
Independent Claim
98 words
A method of tracking the sun with a reflector panel having a plurality of prisms with parallel longitudinal axes to reflect incident solar rays to a radiation receiver, comprising: rotating said panel about a first axis directed toward the receiver to position the surface normal vector of the panel in a plane common to the incident solar rays, the center of the panel and the center of the receiver, and rotating said panel about a second axis perpendicular to the first axis and to the longitudinal axes of the prisms to direct the solar rays to the receiver.
Claim 44
Independent Claim
98 words
A method of tracking the sun with a reflector panel having a plurality of prisms with parallel longitudinal axes to reflect incident solar rays to a radiation receiver, comprising: rotating said panel about a first axis directed toward the receiver to position the surface normal vector of the panel in a plane common to the incident solar rays, the center of the panel and the center of the receiver, and rotating said panel about a second axis perpendicular to the first axis and to the longitudinal axes of the prisms to direct the solar rays to the receiver.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-05-14 | 1982-11-13 | 1983-05-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-05-14 | 1986-11-13 | 1987-05-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-05-14 | 1990-11-13 | 1991-05-15 | $7700.00 | Window Closed / Lapsed |