US 20080184989 A1
A solar blackbody waveguide that captures and uses sunlight to heat a thermal heat transfer fluid. One or more systems of optical mirrors provided on each tower captures and concentrates the sunlight. Each system of optical mirrors is movably mounted on its tower to track the daily movement of the sun and to maintain the proper angle with the horizon throughout the year. Each system of optical mirrors directs the light into an associated short light pipe which delivers the light into a curved solar coil contained within an enclosure. Energy from the light rays is absorbed by the solar coil and transferred to thermal working fluid or heat transfer fluid flowing between the solar coil and the enclosure. The energy laden thermal heat transfer fluid is gathered from a plurality of towers for use with existing technologies, such as with a combined cycle gas turbine, boiler, or steam generator.
1. A solar blackbody waveguide for high pressure and high temperature applications comprising:
a means for collecting and concentrating ambient solar flux,
a hollow lossy solar coil surrounded by an insulated enclosure,
a means for directing the concentrated flux from the means for collecting and concentrating ambient solar flux into an interior of the hollow lossy solar coil in a manner that the concentrated solar flux makes repeated reflections off interior surfaces on the solar coil causing the energy from the concentrated solar flux to be absorbed as heat energy into the solar coil, the solar coil being formed into a varying alignment configuration and located within the insulated enclosure,
said insulated enclosure spaced apart from walls of the enclosure so that an enclosed space is formed between the solar coil and walls of the enclosure; and
a thermal fluid moving within the enclosed space of the enclosure in a manner that the thermal fluid receives heat energy from the solar coil which can be used as a source of energy inside the enclosure or can be used as a source of energy outside the enclosure upon removal of heated thermal fluid from the enclosure.
2. A solar blackbody waveguide for high pressure and high temperature applications according to
a dual-axis tracking means attached to the means for collecting and concentrating ambient solar flux in order to maintain the means for collection and concentrating ambient solar flux in proper angular alignment with the sun by constantly and automatically tracking the apparent movement of the azimuth angle and altitude angle of the sun with respect to the location of the solar blackbody on earth as the earth rotates daily and progresses through its annual orbit about the sun.
3. A solar blackbody waveguide for high pressure and high temperature applications according to
a system of optical mirrors.
4. A solar blackbody waveguide for high pressure and high temperature applications according to
a system of optical lenses.
5. A solar blackbody waveguide for high pressure and high temperature applications according to
a lossless optical waveguide.
6. A solar blackbody waveguide for high pressure and high temperature applications according to
7. A solar blackbody waveguide for high pressure and high temperature applications according to
a hollow lossy waveguide for electromagnetic radiation;
said hollow lossy waveguide being constructed of metallic or other electrically and thermally conductive materials so that concentrated solar flux introduced into the lossy waveguide at a series of acute angles to the longitudinal axis of the waveguide will tend to propagate along the longitudinal axis making numerous reflections on interior walls of the waveguide with a loss of energy upon each successive reflection and causing energy contained in the solar flux to be converted into heat energy which is conducted through the solar coil to exterior walls of the lossy waveguide.
8. A solar blackbody waveguide for high pressure and high temperature applications according to
said solar coil provided externally with appurtenances to enhance thermodynamic heat transfer processes between the coil and the thermal fluid.
9. A solar blackbody waveguide for high pressure and high temperature applications according to
10. A solar blackbody waveguide for high pressure and high temperature applications according to
11. A method for converting solar flux to heat energy employing a one or more solar blackbody waveguides for high pressure and temperature applications comprising:
capturing and concentrating light rays from the sun using a system of optical mirrors or a system of optical lenses,
guiding the concentrated light rays through a lossless waveguide into the interior of a hollow continuous solar coil contained within an insulated enclosure,
converting the concentrated light rays into heat energy by multiple reflections of the concentrated light rays against the walls of the solar coil,
transferring the heat energy from the walls of the solar coil into a thermal fluid contained in a space provided between the enclosure and the solar coil, and
using the heat energy contained within the thermal fluid for any process requiring heat.
12. A method for converting solar flux to heat energy employing a one or more solar blackbody waveguides for high pressure and temperature applications according to
moving the system of optical mirrors or optical lenses so that optical mirrors of the system of optical mirrors are constantly facing the sun and track the sun through its daily and seasonal apparent movement across the sky.
1. Field of the Invention
The present invention relates to a solar blackbody waveguide that captures and uses sunlight to heat a thermal working fluid, such as air or water. A system of optical mirrors associated with each solar blackbody waveguide collects and concentrates the sunlight and the sunlight is then directed to the solar blackbody waveguide. The system of mirrors is preferably mounted on a tower so that the system of mirrors can be moved on a dual axis to track the daily movement of the sun and can be tilted to maintain the proper orientation as the angle of the sun with the horizon changes throughout the day and the year. The light rays are directed form the system of mirrors into the solar coil component of its associated solar blackbody waveguide. Energy from the light rays is absorbed by the solar coil and transferred into a thermal working fluid in the space provided between the solar coil and an enclosure vessel in which the solar coil component of the solar blackbody waveguide is located. A plurality of these solar blackbody waveguide units can be connected together so that they cooperate to produce a large volume of energy laden thermal working fluid. The resulting energy laden thermal working fluid can then be used with existing technologies, such as any type of commercial or industrial application requiring hot water, steam or heat. For example, the present invention can be used as an air preheater to heat air for use in association with a combined cycle gas turbine. If water is used as the thermal working fluid, the present invention could be used as a steam generator for use in steam cycle turbine plants or other commercial or industrial processes requiring steam.
2. Description of the Related Art
The effective use of solar flux as a source of heat to drive heat engines has been the aim of numerous thermal-solar energy technologies. Unlike photoelectric solar cells which convert solar energy directly into electrical energy, thermal-solar technologies convert solar energy into heat which is then converted into mechanical energy and finally into electrical energy. Typically, at the center of this conversion process in current technologies is the steam or Rankine cycle.
Low cost production of electricity using current steam cycle technologies is based on magnitude-of-scale production. Production of electricity in the Megawatt (MW) range requires enormous amounts of heat. Assembling enough energy from weak solar energy in a single location to power a generator in this range remains the defining technical challenge of this form of solar energy.
The low energy-density of ambient sunlight requires that the geometry of concentrator assemblies be very large. Assembling enough energy in one location to power a large heat engine has been handled by three primary methods. The first method uses thermal transfer fluid to accumulate heat as it passes from one incremental heat generator to another. The second method transmits large quantities of solar energy over large distances in a nearly lossless manner to a single “receiver” point. The third method generates electricity using small generator systems and the total produced power is then assembled via a distributed electrical bus.
Systems involving each of all of these three methodologies have been developed to the point of operation. However, each system has introduced its own technical complications, thermal losses, and inefficiencies as described briefly below.
Several trough systems were built in the mid to late 1980's. One such system was the parabolic trough system. This type of system incrementally accumulates energy by using a heat transfer fluid. Sunlight is focused using a parabolic trough-shaped mirror on to a pipe containing a heat transfer fluid, typically thermal oil. This hot oil is passed successively through a number of parabolic trough concentrators until the temperature of the oil is heated to approximately 390° C. (735° F.). This hot oil is then passed through a heat exchanger to generate superheated steam from which electricity is generated using a conventional steam turbine.
The parabolic trough system has several drawbacks. This system has high thermal losses due to the fact that the oil-filled pipe at the center of the. concentrator trough is not insulated and re-radiates the accumulated heat back into space. Also, not all the solar energy incident on the pipe containing the heat transfer fluid is absorbed by the fluid. In fact, most of the energy is reflected. In addition, use of a heat exchanger in the steam generator loop increases the overall inefficiencies of the system. These components combine to limit the gains that can be acquired from magnitude-of-scale operation. In addition, there are other limitations for these implementations since these systems do not track the sun from east to west, although they do track the seasonal inclination angle. As a result, they are typically constructed with a “due-south” orientation and are most effective in the late morning to early afternoon.
At least two power tower systems were built in the mid 1980's to mid 1990's. This type of system concentrates sunlight over a large area by transmitting it in a lossless manner through ambient air to a receiver point located at the top of a power tower. Mirrors or heliostats are mounted on the ground surrounding the power tower. These heliostats track the sun and reflect the light from the sun up to the power tower where a thermal fluid system is located. The power tower is in essence a large, fragmented collector dish distributed over a large area. The heat transfer fluid is molten sodium which is heated to approximately to 570° C. (1050° F.) as it passes through the receiver at the focal point of the power tower. This thermal fluid is then passed through a heat exchanger to generate superheated steam from which electricity is generated using a conventional steam turbine.
The power tower system also has several drawbacks. This system has high thermal losses. With the receiver suspended in the air with limited insulation, it re-radiates accumulated heat back into space. Additionally, use of a heat exchanger in the steam generator loop increases the overall inefficiencies of the system. These thermal considerations combine to limit the gains that can be acquired from magnitude-of-scale construction and lower the overall thermal efficiency. In addition, there are other limitations for power towers since self-shadowing of the heliostats keeps them from providing power over the entire day.
Dish engine systems are in the advanced prototype phase with test facilities deployed in the late 1990's. These systems use an array of parabolic dish-shaped mirrors to focus solar flux to a small “receiver” located at the focal point of the parabolic mirror assembly. A thermal working fluid of air or hydrogen is heated to about 750° C. (1380° F.) and used directly to generate electricity using a small turbine or Stirling Engine attached to the dish without use of a heat exchanger. The electricity generated is collected using a system of electrical buses or collection systems for final connection to the utility electric grid. Due to the higher operating temperatures and elimination of heat exchangers, these systems have higher thermal efficiencies than parabolic troughs and power towers.
However, these dish engine systems do not overcome the same basic drawback of the other technologies, i.e. high thermal losses with the receiver suspended in the air with limited insulation and resultant re-radiation of accumulated heat back into space. These systems can track the daily progress of the sun, and therefore, provide power for longer periods during the day. The addition of turbines or Stirling Engines attached to the dish generator increases the structural load-bearing requirements of the support system. The structures required to support the dish and engine can become massive and expensive to construct.
The current art in solar-thermal energy recognizes the need to effectively accumulate the necessary amounts of heat for magnitude-of-scale production. However, the means for doing this as demonstrated in the art is not entirely physically realizable. An example is shown in U.S. Pat. No. 4,982,723 where solar energy is introduced into a thermal fluid inducing a photochemical reaction. In this process, the need for accumulation of energy is recognized, but the physical mechanism for making it happen on a large scale is sketchy.
Another technology is reflected in U.S. Pat. No. 4,841,946 in which a Cassegrain reflector is used to concentrate solar flux. This concentrated flux is transported via light pipe to a cavity where the solar energy is converted into heat energy. Although this patent contains some interesting abstract concepts, it does not obtain a complete solution when scaled up for actual power production levels. This proposed technology implies (without a realizable solution) that if more energy is required, the energy from a plurality of similarly situated reflectors can be conducted to a single receiver via a plurality of light pipes. An inherent difficultly that this technology fails to overcome is the transmission losses associated with moving highly concentrated solar energy via light pipes over long distances. Although these losses are small, they are not zero, and a transmission loss of one tenth of one percent (0.1%) in a light pipe carrying one (1) MW of energy is an enormous amount of energy to be absorbed by the material from which the light pipe is constructed. Nor does this technology propose any useful method for combining light from the plurality of light pipes into a single, common light pipe for long distance transmission.
Applicant's own previous invention which is described in U.S. Pat. No. 6,899,097 which was filed on May 26, 2004 and issued on May 31, 2005 for Solar Blackbody Waveguide for Efficient and Effective Conversion of Solar Flux to Heat Energy addresses many of these problems. However, one drawback of that previous invention is that the solar coil waveguide employed in that solar blackbody and into which a plurality of towers of solar arrays fed was linear. Because the solar coil was straight, the solar blackbody waveguide had to extend a long distance in order to capture sufficient heat energy to be commercially useful. Thus, the land requirements for this type of installation made the installation expensive and required the mechanical separation of large equipment components such as compressors and turbines. Also, relief of linear thermal stress presented some of the most difficult large scale engineering challenges.
Another problem with Applicant's prior invention is that light collected from multiple towers was fed into a single solar blackbody waveguide, which required an elaborate and expensive system of solar light pipes, solar horns, etc. Also, because the solar flux was transmitted via the tower down to the ground, the light rays had to traverse the structural support and tracking mechanism by which the tower was positioned and tilted to follow the sun. This added to the complexity and expense of Applicant's previous invention and introduced potential energy losses via the light pipes.
Still another shortcoming of Applicant's previous invention is that the solar blackbody waveguide used in that invention was buried underground. This made initial installation of the equipment more complicated and expensive. And because the equipment was relatively inaccessible, this also made repair of the equipment more difficult and expensive. Additionally, because a large proportion of the equipment for Applicant's previous invention was located underground, this type of installation was not suitable for certain types of terrain, such as extremely rocky or swampy areas. Also, this type of installation was particularly susceptible to damage in the event of movement of the earth, such as in the event of earth tremors or earthquakes.
It has long been recognized that efficiency of a turbine based-heat engine is related to the combustion temperature and the compression ratio. Restated, this indicates the higher the temperature at the inlet to the turbine, the higher the efficiency and, simultaneously, the higher the pressure at the inlet to the turbine, the higher the efficiency. Applicant's previous invention was limited in its pressure and temperature capabilities, intrinsically limiting its overall efficiency potential.
One of the primary drawbacks to large-scale solar and wind farm generating facilities is the environmental impact resulting from the large land-usage on which these projects are sited. Every large power-generation plant to be constructed in the future in the United States will be subjected to state Environmental Impact Statement (EIS) processes or federal Environmental Impact Report (EIR) requirements. Often energy projects are subjected to both federal and state environmental studies during the permitting phases of the project. Assessment of project impact on Visual Resources is an important factor in regulatory considerations for approval of these projects. Applicant's previous invention contemplated land-use for solar technologies only.
The present invention addresses these shortcomings by employing a solar coil that is curved into a circular, helical, or spiral shape instead of being linear. Use of a curved solar coil provides for simple thermal stress relief and allows the present invention to be installed in much smaller areas and allows this system to be combined in the same area with other energy gathering technologies, such as, for example, within an existing wind power collection field. By employing the same land for both solar and wind power collection, the cost of land for installation is greatly reduced and the productivity per unit of collection area is increased. This dual land usage also decreases the overall environmental impact on Visual Resources, since the same land can be used to co-locate solar technologies, wind technologies, or other energy production facilities. Also, because of the smaller space requirements of this present invention over Applicant's prior invention, this present type of invention can be added as a retrofit into existing wind power collection fields.
The present invention also eliminates the need for multiple towers to feed into a single solar blackbody waveguide. By providing a separate solar blackbody waveguide in association with each system of optical concentrating mirrors and designing the system so that light rays do not have to traverse the mechanism for rotating and tilting the tower, the need for light pipe is minimized or eliminated altogether and the equipment needed to direct light from the collection and concentration mirrors into the solar coils in the present invention is greatly simplified over those required in Applicant's earlier invention. This results in a large reduction in installation and maintenance costs and an increase in the overall solar-to-heat conversion efficiency.
The improvements in the present invention also provide for higher operating pressures and temperatures of the thermal fluid, thus permitting increases in the thermodynamic efficiency of turbine-based heat engine technologies. Since the heat is accumulated in the thermal fluid, which is transported through a series of blackbody waveguides, the present invention can be hybridized using a variety of auxiliary fuels, including coal, nuclear, natural gas, and other renewable fuel sources such as biomass and trash. This is an improvement over the Applicant's previous invention which contemplated hybridization primarily with natural gas.
Finally, the most complex components of the present invention, i.e. those with the greatest need for maintenance, are installed above ground. By eliminating the need for the solar blackbody waveguide to be buried in the ground, the equipment is less complicated and more accessible. This reduces installation and maintenance costs and associated difficulties during operation. Also, with all of the critical equipment located above ground in the present invention, this type of installation is suitable for a wide range of terrains and is not as susceptible to damage in the event of earthquakes.
The present invention is a solar blackbody waveguide that is particularly suitable for high pressure, high temperature applications. The solar blackbody waveguide captures and uses sunlight to heat a thermal working fluid, such as air or water. Once the thermal working fluid is heated, it can then be used in association with existing technologies. For example, the present invention can be used as an air preheater to heat air for use in association with a combined cycle gas turbine or in other industrial or commercial applications where heat, steam or hot water is needed.
The present invention employs a system of optical mirrors movably mounted on a tower so that the mirrors can be moved to track the daily movement of the sun across the sky due to the rotation of the earth and can be tilted to maintain the proper orientation as the angle of the sun with the horizon changes due to the annual orbit of the earth around the sun.
The system of optical mirrors collects and directs the concentrated light rays into a curved solar coil located above ground. The curved solar coil is attached to and fixed relative to the system of mirrors so that both the solar coil and the system of mirrors are movably mounted on the tower. Energy from the light rays is absorbed by the solar coil and transferred into the thermal working fluid flowing through a space provided between the solar coil and the enclosure of the solar blackbody waveguide. The energy laden thermal working fluid is removed from the space at an outlet of the enclosure so that it can be used with existing technologies, as previously described.
Referring now to the drawings and initially to
This embodiment of the invention 10 is an improvement to simple-cycle and combined-cycle gas turbine heat engines by preheating the air or thermal working fluid used prior to its introduction into the auxiliary fuel combustion chamber/heat exchanger 20 of the gas turbine 22, as will be more fully described hereafter in association with
Referring now to
Referring now to
However, the system of optical mirrors 18 is different in some key aspects from the optical systems used in telescopes. The section of the primary parabolic mirror 30 is rectangular rather than circular as in telescopes. This provides optimal land usage and shadowing effects. Further, the primary mirror 30 is not centered, only the upper half of the parabola is used. This prevents the primary mirror 30 from collecting water and snow as the altitude angle approaches vertical as would happen with a dish style mirror used in a telescope.
Once the concentrated light rays 40 pass through the hole 36 of the primary parabolic mirror 30, they enter into the short optical waveguide 42 which will direct the concentrated light rays 40 into a solar coil 44 located within an enclosure 46 of the solar blackbody waveguide 10. From the point that the concentrated light rays 40 enter the short optical waveguide 42, the path of the concentrated light rays 40 contained within the solar blackbody waveguide 10 will be referred to as concentrated light rays 40 regardless of whether the light rays are parallel, converging or diverging.
The short optical waveguide 42 is a flared, external extension of the solar coil 44 that penetrates through the enclosure 46 containing the thermal fluid. This external extension 42 is designed to capture any stray concentrated light rays 40 and make sure they are directed into the coil 44. This short optical waveguide 42 is internally coated or mirrored to be highly reflective so that minimal energy is lost in any reflections that occur outside of the enclosure 46. In addition, the hyperbolic secondary mirror 32 preferably reflects the concentrated light rays 40 to a focal point 34 that is internal to the solar coil 44 and within the interior of the enclosure 46, making the short optical waveguide 42 only necessary for capture of stray concentrated light rays 40.
Due to the convergence of the concentrated light rays 40 and the internally mirrored surfaced of the short optical waveguide 42, the concentrated light rays 40 arrive at the entrance to the solar blackbody waveguide 10, as illustrated in
As illustrated in
The dual-axis tracking mechanism 52 consists of a first axis or altitude drive motor 54 for driving the gear drive mechanism 58 for tilting the altitude angle of the system of optical mirrors 18 relative to the horizon 56 so that the system of optical mirrors 18 directly faces the sun during all seasons of the year and second axis or azimuth drive motor 60 for rotating the system of optical mirrors 18 so that the system of optical mirrors 18 tracks the sun through its daily movement through the sky. Both of the first axis or altitude drive motor 54 and the second axis or azimuth drive motor 60 are continuously controlled to maintain the system of optical mirrors 18 at approximately a 90 degree orientation to the sun's path as the earth makes its daily rotation on its axis and also makes its annual orbit around the sun.
Although not specifically illustrated, the proper tracking angles, both azimuth and altitude, are calculated from the latitude and longitude of the tower's location via a small programmable logic controller (PLC) that controls the operation of the electric motors 54 and 60. The dual-axis tracking mechanism 52 permits the tower 12 to track the hourly movement of the sun through the sky from east to west so that the system of optical mirrors 18 always faces the sun. The PLC will generally be located remotely from the tower 12 and will serve to operate the dual-axis tracking mechanisms 52 on one or more towers 12 located at an installation of the invention. As taught in Applicant's U.S. Pat. No. 6,899,097, optical angle readers will preferably be employed to track the actual azimuth and altitude angles of the system of optical mirrors 18 relative to the tower 12. The optical angle readers use an optical compact disk or CD reader to read precise angular data encoded on a compact disk or CD to keep track of the actual azimuth and altitude angles of the system of optical mirrors 18. This angular data is used in a feedback control loop to control the position of the azimuth and altitude angles of the dual-axis tracking mechanism 52 and the position of the attached system of optical mirrors 18.
After passing the short optical waveguide 42, the concentrated light rays 40 enter the solar coil 44. As illustrated in
The developed heat is conducted from the interior walls 62 to the external or exterior walls 68 of the solar coil 44 and into a heat transfer fluid that flows through the enclosure 46 that surrounds the solar coil 44. The heat transfer fluid is illustrated in the drawings by arrows associated with the numeral 64. Unheated heat transfer fluid is denoted in the drawings as 64U and heated heat transfer fluid is denoted in the drawings as 64H. Exhaust of the heat transfer fluid from the system is denoted in the drawings as 64E. Thus the solar blackbody waveguide 10 functions to first convert the potential energy contained in the light rays 40 to thermal energy and then serves as a heat exchanger by transferring the heat from the interior wall 62 of the solar coil 44, through to the external wall 68 of the solar coil 44 and into the heat transfer fluid 64 that is flowing through an enclosed space 66 provided between the exterior walls 68 of the solar coil 44 and an interior wall 70 of the enclosure 46.
As illustrated in
As illustrated in
As further illustrated in
The enclosure 46 is preferably insulated by adding a high temperature refractory insulation system 90 to the exterior surface 92 of the enclosure 46 to minimize heat loss. The heat transfer lines 88 are similarly insulated.
The solar coil 44 works like a waveguide for the concentrated light rays 40 but is not lossless. Instead, the concentrated light rays 40 reflect off of the interior walls 62 of the metal solar coil 44, losing some energy to the solar coil 44 on each reflection. This energy is absorbed by the solar coil 44 causing the temperature of the solar coil 44 to rise rapidly. Heat travels from the interior walls 62 through the solar coil 44 to the exterior walls 68 of the solar coil 44. From the exterior walls 68, the heat transfers into the heat transfer fluid or thermal working fluid 64 such as air or water passing over the exterior walls 68 of the solar coil 44 within the enclosed space 66 provided between the solar coil 44 and the enclosure 46. As illustrated in
In essence, the solar coil 44 acts as a solar power heating coil within the enclosure 46. Due to the geometry of the solar coil 44, it acts as a lossy, blackbody waveguide absorbing nearly one hundred percent (100%) of the solar energy collected and injected into the coil 44 in the form of concentrated light rays 40. The coil 44 is preferably constructed of high temperature, poly-molybdenum steel suitable for operation at temperatures above 1200° F.
Other components of existing combine cycle technology illustrated in
Due to the variable nature of the energy input by the preheater 96 in
Each of the uses described above involve removing the transfer fluid 64 from the enclosure 46 for use in providing heat to a system located outside the enclosure 46. The invention is not so limited and the transfer fluid 64 can be used within the enclosure 46. For example, the enclosure 46 could be a building or other type of structure, the heat transfer fluid 64 could be air, and the solar blackbody waveguide 10 could be used in conjunction with the building's HVAC system as a means of heating the air within the interior of the enclosure 46 without the need to remove the air from the building.
While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for the purposes of exemplification, but is to be limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element thereof is entitled.