US20140202448A1

US20140202448A1 - Production of Electricity and Heat Storage Using Solar Mirrors

Info

Publication number: US20140202448A1
Application number: US13/745,735
Authority: US
Inventors: David Dor-el
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-01-18
Filing date: 2013-01-18
Publication date: 2014-07-24

Abstract

A solar energy collection array includes a plurality of individual mirrors and a plurality of receiver facets. The mirrors form a fixed multifaceted curved collection of mirrors. Each individual mirror is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces. The receiver facets are disposed as fixed curved multifaceted receivers. Each receiver facet is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces and wherein each individual mirror is aimed at one of the receiver facets so that each receiver facet is optically aligned with one of the individual mirrors thereby creating a small mirror multiple target. Different facets are utilized at different times of day and season based on the sun's position.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to solar power generators, more particularly to concentrating solar collectors.
2. Description of the Prior Art
U.S. Pat. No. 4,137,897 teaches a reflector array that provides for the collection and concentration of a relatively constant daily total quantity of usable energy for one or more energy receivers through use of a collector array support configuration that provides for the efficient use of collector surface and land. This is accomplished by combining a plurality of collectors with a support structure wherein the collectors are carried by a terraced support surface of the structure and the reflective surfaces of the collectors lie in essentially a common sun facing plane at noon. The terraced support surface is a terraced east-west extending wall of an enclosure such as a residential, commercial or industrial building. The system collects and concentrates solar energy for providing highly concentrated solar energy to an energy receiver. The system includes support mechanism which includes a terraced support structure, a plurality of substantially reflective collector elements mounted on the support mechanism in closely spaced apart generally non-inter-element shading relationship as a unified array of operative elements. The collector elements having surfaces formed as confocal parabolas for effective direction off axis with respect to the energy receiver during most of the period for which sunlight is available. A plurality of collector elements is positioned for reflecting solar energy collected generally horizontally to the energy receiver and means for driving the collector elements in tracking relationship with the sun while continuously reflecting solar energy toward the energy receiver.
The continuing depletion of fossil and nuclear fuels may be one of the most significant long term problems facing the world. There is condiderable disagreement regarding the size of the depletable fossil and nuclear fuel resources. Thus, increasing interest is now centered about renewable energy resources such as solar energy. The collection and concentration of solar energy is an ancient art and accordingly over the span of many centuries numerous solar energy collector and concentrator systems have been devised. Until relatively recently the total solar energy collection and concentration capability of such systems was relatively small and generally confined to heating systems or endothermic industrial processes requiring relatively low levels of energy input.
These prior art systems generally can be characterized as fixed or movable arrays of reflectors wherein the array elements may be fixed at a given azimuth or configured to comprise heliostat elements that include means for adjustment that enables automatic or manual tracking of the sun to maximize solar energy collection and concentration. The movable arrays are generally carried by a sun tracking support that is moved through a predetermined orbit to track around an axially disposed energy receiver, such as a furnace, boiler, vaporizer, etc. As will be readily appreciated, the energy collection capability, or capacity, of such movable arrays is as a practical matter rather limited in view of the engineering problems attendant the movement of relatively large arrays. Thus, more recent attempts to collect relatively large amounts of solar energy for concentration and utilization for electrical power generation, industrial uses, and the like, have been centered about the utilization of a solar array collector system herein referred to as a distributed field heliostat array. As is well known, the collector arrays presently generally used in the United States Energy Research and Development Administration Solar Thermal Conversion Central Power Projects utilize the distributed field heliostat array that distributes numerous heliostats over a field, commonly a very large tract of land, and wherein the substantial number of heliostats are each separately supported on pedestals, or foundations, in the distributed field. Since large expanses of collector surfaces are expensive, and since land values in industrialized areas are generally very high, a primary factor in reducing the capital investment directly attributable to the development of solar energy for industry is the efficient use of collector surface and land.
In addition, an energy receiver generally associated with a distributed field array comprises an energy receiver means mounted on a tower and wherein the energy receiver requires an entry port for collected and concentrated solar energy. In such an installation the entry port has a relatively wide aperture angle and to increase the energy input to the central receiver the spacing between the collector array and the central receiver must increase if the central receiver entry port aperture angle remains constant. In the distributed field collector array systems this requires vertical separation between the collector array and the central energy receiver. The system described, which has been referred to as a power tower system in a presently proposed project for 100 MWe being developed as a booster system for an existing electrical generation plant, contemplates acres of mirrors in a field to reflect the sun's heat to a water boiler stop a 1000-foot tower. More specifically the proposed project envisions the utilization of at least 170 acres of land to accommodate the distributed field of collectors, or heliostats. Alternatively the same project proposes to attempt to utilize three towers each 430 feet high instead of a single 1000-foot tower. At central receiver towers of the aforementioned height introduce possible air space and construction problems. Further, the energy concentration ratio for a given collector array is partially a function of shading of one collector element by another due to sun position or angle off the axis of the central receiver energy collector aperture and also shading of collector elements by the tower and boiler structure. Shading in the distributed field collector, or heliostat, array systems is a function of both solar declination and the time of day. An open sky collector system is exempified by U.S. Pat. No. 3,118,437, Jan. 21, 1964, which also appears to be closely related structurally to a solar energy collection system at Odeillo, France. Such systems are considered to be representative of the prior art systems that attempt to concentrate, as well as collect solar energy from the previously discussed distributed field heliostat arrays. These systems are characterized by the utilization of duplex reflector systems which it will be appreciated are not generally suitable for concentration of solar energy at a high order as is required for cost effective solar energy utilization for power generation, and the like.
U.S. Pat. No. 7,906,722 teaches a concentrating solar collector cell includes primary and secondary mirrors disposed on opposing convex and concave surfaces of a light-transparent optical element. Light enters an aperture surrounding the secondary mirror, and is reflected by the primary mirror toward the secondary mirror, which re-reflects the light onto a photovoltaic cell mounted on a central region surrounded by the convex surface. The primary and secondary mirrors are preferably formed as mirror films that are deposited or plated directly onto the optical element. A concentrating solar collector array includes a sheet-like optical panel including multiple optical elements arranged in rows. The photovoltaic cells are mounted directly onto the optical panel, and the primary mirrors of the individual collector cells include metal film segments that are coupled by the photovoltaic cells to facilitate transmission of the generated electrical energy. Bypass diodes are connected in parallel with the photovoltaic cells. The concentrating solar collector includes a solid, light-transparent optical element having a first side including a relatively large convex surface, a second side including an aperture surface, and a relatively small curved surface defined in a central portion of the aperture surface, wherein the aperture surface is substantially flat such that parallel light beams directed perpendicular to and passing through the aperture surface remain parallel while passing through the optical element between the aperture surface and the convex surface; a primary mirror disposed on the convex surface and a secondary mirror disposed on the curved surface. The concentrating solar collector also includes a photovoltaic element disposed in a central region surrounded by the convex surface.
Photovoltaic solar energy collection devices used to generate electric power generally include flat-panel collectors and concentrating solar collectors. Flat collectors generally include photovoltaic cell arrays and associated electronics formed on semiconductor (e.g., monocrystalline silicon or polycrystalline silicon) substrates, and the electrical energy output from flat collectors is a direct function of the area of the array, thereby requiring large, expensive semiconductor substrates. Concentrating solar collectors reduce the need for large semiconductor substrates by concentrating light beams (i.e., sun rays) using, e.g., a parabolic reflectors or lenses that focus the beams, creating a more intense beam of solar energy that is directed onto a small photovoltaic cell. Thus, concentrating solar collectors have an advantage over flat-panel collectors in that they utilize substantially smaller amounts of semiconductor. Another advantage that concentrating solar collectors have over flat-panel collectors is that they are more efficient at generating electrical energy. A problem with conventional concentrating solar collectors is that they are expensive to produce, operate and maintain. The reflectors and/or lenses used in conventional collectors to focus the light beams are produced separately, and must be painstakingly assembled to provide the proper alignment between the focused beam and the photovoltaic cell. Further, over time, the reflectors and/or lenses can become misaligned due to thermal cycling or vibration, and become dirty due to exposure to the environment. Maintenance in the form of cleaning and adjusting the reflectors/lenses can be significant, particularly when the reflectors/lenses are produced with uneven shapes that are difficult to clean. What is needed is a concentrator-type PV cell and array that avoids the expensive assembly and maintenance costs associated with conventional concentrator-type PV cells.
U.S. Pat. No. 4,103,151 teaches a solar powered engine and tracking system which includes a piston working within a cylinder for turning a drive shaft for driving an electrical generator or performing other useful work, a solar concentrator having a plurality of mirrors, each reflecting Sun light on a common focal point on the end of the cylinder for heating a flash boiler located thereon, preheated water from a source is injected into the flash boiler by a pump powered by the drive shaft timed according to piston movement after operating the piston, the steam is then vented from the boiler by valve means operated from the drive shaft. A starter motor is provided to initially start the engine operating by rotating the drive shaft until the piston movement is self-sustaining. The entire device is enclosed in a solar energy collector panel for elevating the temperature of the system so as to maintain the water at a sufficient temperature with a minimum of external heating. The collector may also be utilized for separate external heating purposes. Sensor controlled motors track the relative movement of the Sun and Earth and continually position the collector for maximum solar energy concentration.
U.S. Pat. No. 7,872,192 teaches a planar concentrator solar power module which has a planar base, an aligned array of linear photovoltaic cell circuits on the base and an array of linear Fresnel lenses or linear mirrors for directing focused solar radiation on the aligned array of linear photovoltaic cell circuits. The cell circuits are mounted on a back panel which may be a metal back plate. The cell circuit area is less than a total area of the module. Each linear lens or linear mirror has a length greater than a length of the adjacent cell circuit. The cell circuit may have cells mounted in shingle fashion to form a shingled-cell circuit. In an alternative module, linear extrusions on the circuit element have faces for mounting the linear mirrors for deflecting sun rays impinging on each mirror onto the shingled-cells. The linear extrusions are side-wall and inner extrusions with triangular cross-sections. The circuit backplate is encapsulated by lamination for weather protection. The planar module is generally rectangular with alternating rows of linear cell circuits and linear lenses or linear mirrors. The planar concentrator solar power module apparatus includes a planar base, base formed by a planar metal back sheet and an electrical insulating film on the metal back sheet, plural parallel linearly spaced aligned arrays of linear photovoltaic cell circuits on the base, the cell circuits further comprising plastic sheets and silicon cells sandwiched between the plastic sheets, the arrays being spaced apart on the base more than a width of an array, a metal frame surrounding the module and extending upward away from the planar base, a glass front plate mounted on the metal frame and spaced from the silicon cells, and an array of linear planar Fresnel lenses on the glass front plate spaced above the base for directing focused solar radiation on the aligned arrays of linear photovoltaic cell circuits, and wherein the metal back sheet spreads and conducts heat laterally away from the silicon cells sandwiched between the plastic sheets on the base.
Solar cells generate electricity but at a cost which is too high to compete with electricity from the electric power company. It is generally acknowledged that the solar panel cost will have to drop to approximately $1 to $2 per installed Watt before solar cells can compete in this large potential market. Today's cost for solar panels is in the $6 to $7 per Watt range. Three different approaches have been pursued in attempts to resolve this cost problem.
The conventional approach is to use large silicon solar cells tiled in planar modules where the cell area represents over 80% of the total panel area. The cells in this approach can be single crystal or large grain polycrystalline cells. This approach represents over 90% of the market but the cost of this approach has bottomed out and no further cost reductions are expected. The second approach is based on the assumption that the cost of silicon wafers is too high and one needs to make low cost thin film cells. The argument is that paint is cheap and that maybe a way can be found to make paints generate electricity. This thin film approach includes amorphous silicon and small grain-size polycrystalline materials like CuInSe2 and CdTe. The problem with this approach has been that destroying the crystal material degrades solar cell performance. To date, this approach has not yielded modules costing less than $8 per Watt. The third approach is based on concentrating the sunlight onto small single crystal cells using larger inexpensive plastic lenses or metal mirrors. This approach allows more efficient cells to be used and makes good technical sense. However, the problems with this approach are not technical but instead relate to business and politics. Solving the business problems inherent in this approach is the focus of this invention.
Serious attempts to develop solar concentrator photovoltaic systems can again be divided into three parts. First, attempts have been made to use point focus lenses and 30% efficient cells where the systems operate at high concentration ratios, e.g. approximately 500 suns. The problem here is not with the technology. The various components work, and systems have been demonstrated. The problem here is that the investment required to create positive cash flow is too large. Large companies will not take the risk and small companies do not have the resources and the government is not helping. The 30% cells are not being manufactured and investment is required here. Furthermore, trackers with the required accuracy are not being manufactured. Again investment is required. Investment is also required for the thermal management and lens elements. Finally, these systems are not cost effective unless made in large sizes and in large volumes and there are no intermediate markets other than the utility scale market. The second approach to solar concentrators involves the use of arched linear Fresnel lenses and linear silicon solar cell circuits. These systems are designed to operate at approximately 20 suns. This is also a technically proven approach but this approach also suffers from the investment problem. Here, investment is again required for special lenses, trackers, and thermal management systems. Here, the plan is that the cells will be available from the cell suppliers who make planar arrays. However, this presents two problems. The first problem is that the planar cells have to be significantly modified to operate at 20 suns. The second problem is that the planar cell suppliers are not motivated to cooperate. For example, suppose that the concentrator approach proves to be cheaper and the market expands by three times. The problem for the planar cell suppliers is that their part will actually shrink by 3/20 times. Again, these systems are not cost effective unless made in large sizes and in large volumes and there are no intermediate markets other than the utility scale market. The third approach to solar concentrator systems was initiated by the planar module manufactures. Realizing that if their one sun planar module were operated at 1.5 suns, they could produce 1.5 times more power and consequently reduce the cost of solar electricity by 1.5 times, they built a system using edge mirrors to deflect sunlight from the edge areas onto their panels. Unfortunately, this approach was technically naive. The problem encountered was that the modules then absorbed 1.5 times more energy and there was no provision to remove the additional heat. This then affected the module lifetime. Solar concentrators require very high investments to scale up production of a new concentrator cell. The investment required for manufacturing scale-up versions of a new cell is prohibitive. Another problem that needs to be solved is the cell-interconnect problem. There is a need for a solar concentrator module that is a retrofit for a planar module and that is easier and cheaper to make. The business infrastructure for trackers and lenses should already be in-place. The heat load should be easily manageable. Investment requirements should be manageable and it should not threaten existing cell suppliers. Cells to be used should be available with very minor changes relative to planar cells. Therefore, low cost cells should be available from today's cell suppliers. Finally, it should be usable in early existing markets in order to allow early positive cash flow.
U.S. Pat. No. 7,388,146 teaches a planar concentrator solar power module has a planar base, an aligned array of linear photovoltaic cell circuits on the base and an array of linear Fresnel lenses or linear mirrors for directing focused solar radiation on the aligned array of linear photovoltaic cell circuits. The cell circuits are mounted on a back panel which may be a metal back plate. The cell circuit area is less than a total area of the module. Each linear lens or linear mirror has a length greater than a length of the adjacent cell circuit. The cell circuit may have cells mounted in shingle fashion to form a shingled-cell circuit. In an alternative module, linear extrusions on the circuit element have faces for mounting the linear mirrors for deflecting sun rays impinging on each mirror onto the shingled-cells. The linear extrusions are side-wall and inner extrusions with triangular cross-sections. The circuit backplate is encapsulated by lamination for weather protection. The planar module is generally rectangular with alternating rows of linear cell circuits and linear lenses or linear mirrors. The method of assembling a planar concentrator solar power module includes the steps of obtaining existing, readily available commercial planar solar cells, each solar cell having a continuous grid electrode, cutting the solar cells in segments, each resulting segment comprising a portion of the grid electrode, mounting the divided cells in precisely spaced rows on a metal beat spreader back plate and forming a circuit element, connecting the cells in series to form linear circuit rows, mounting flat, linear mirrors on the plate, alternating the linear circuit rows and the flat, linear mirrors in the circuit element, deflecting sun rays with the linear mirrors on to the linear circuit rows, concentrating solar energy into the linear circuit rows, transferring waste heat to the metal heat spreader back plate spreading the waste heat laterally through the metal plate so that a temperature of the metal plate is nearly uniform, and providing optimal thermal energy management. Solar cells generate electricity but at a cost which is too high to compete with electricity from the electric power company. It is generally acknowledged that the solar panel cost will have to drop to approximately $1 to $2 per installed Watt before solar cells can compete in this large potential market. Today's cost for solar panels is in the $6 to $7 per Watt range. Three different approaches have been pursued in attempts to resolve this cost problem.
The conventional approach is to use large silicon solar cells tiled in planar modules where the cell area represents over 80% of the total panel area. The cells in this approach can be single crystal or large grain polycrystalline cells. This approach represents over 90% of the market but the cost of this approach has bottomed out and no further cost reductions are expected. The second approach is based on the assumption that the cost of silicon wafers is too high and one needs to make low cost thin film cells. The argument is that paint is cheap and that maybe a way can be found to make paints generate electricity. This thin film approach includes amorphous silicon and small grain-size polycrystalline materials like CuInSe2 and CdTe. The problem with this approach has been that destroying the crystal material degrades solar cell performance. To date, this approach has not yielded modules costing less than $8 per Watt. The third approach is based on concentrating the sunlight onto small single crystal cells using larger inexpensive plastic lenses or metal mirrors. This approach allows more efficient cells to be used and makes good technical sense. However, the problems with this approach are not technical but instead relate to business and politics. Solving the business problems inherent in this approach is the focus of this invention. Serious attempts to develop solar concentrator photovoltaic systems can again be divided into three parts. First, attempts have been made to use point focus lenses and 30% efficient cells where the systems operate at high concentration ratios, e.g. approximately 500 suns. The problem here is not with the technology. The various components work, and systems have been demonstrated. The problem here is that the investment required to create positive cash flow is too large. Large companies will not take the risk and small companies do not have the resources and the government is not helping. The 30% cells are not being manufactured and investment is required here. Furthermore, trackers with the required accuracy are not being manufactured. Again investment is required. Investment is also required for the thermal management and lens elements. Finally, these systems are not cost effective unless made in large sizes and in large volumes and there are no intermediate markets other than the utility scale market. The second approach to solar concentrators involves the use of arched linear Fresnel lenses and linear silicon solar cell circuits. These systems are designed to operate at approximately 20 suns. This is also a technically proven approach but this approach also suffers from the investment problem. Here, investment is again required for special lenses, trackers, and thermal management systems. Here, the plan is that the cells will be available from the cell suppliers who make planar arrays. However, this presents two problems. The first problem is that the planar cells have to be significantly modified to operate at 20 suns. The second problem is that the planar cell suppliers are not motivated to cooperate. For example, suppose that the concentrator approach proves to be cheaper and the market expands by three times. The problem for the planar cell suppliers is that their part will actually shrink by 3/20 times. Again, these systems are not cost effective unless made in large sizes and in large volumes and there are no intermediate markets other than the utility scale market. The third approach to solar concentrator systems was initiated by the planar module manufactures. Realizing that if their one sun planar module were operated at 1.5 suns, they could produce 1.5 times more power and consequently reduce the cost of solar electricity by 1.5 times, they built a system using edge mirrors to deflect sunlight from the edge areas onto their panels. Unfortunately, this approach was technically naive. The problem encountered was that the modules then absorbed 1.5 times more energy and there was no provision to remove the additional heat. This then affected the module lifetime.
Solar concentrators require very high investments to scale up production of a new concentrator cell. The investment required for manufacturing scale-up versions of a new cell is prohibitive. Another problem that needs to be solved is the cell-interconnect problem. There is a need for a solar concentrator module that is a retrofit for a planar module and that is easier and cheaper to make. The business infrastructure for trackers and lenses should already be in-place. The heat load should be easily manageable. Investment requirements should be manageable and it should not threaten existing cell suppliers. Cells to be used should be available with very minor changes relative to planar cells. Therefore, low cost cells should be available from today's cell suppliers. Finally, it should be usable in early existing markets in order to allow early positive cash flow. Effective solar flux at the earth's surface ranges between 100-200 W/m2.
Current technologies for solar collection include photovoltaic (PV) panels which directly convert light into electric energy, mirrors to redirect/concentrate solar power (CSP) onto a target heat collector which drives a generator, PV panels realistically produce an average output of 10-25 W/m2 (10-15% efficiency), depending mostly on geographical area and mirror based installations typically produce 35-55 W/m2 of mirrors, but a much larger area is needed for the complete installation so real output is about 5-10 W/m2. Efficiencies of the current technologies are predicted to increase by only about 50% over the next 15 years. The current cost for installation of a PV based system is about $200/m2. A mirror based system costs about $130/m2 of mirrors. The current cost of building a concentrated solar power station is typically about $2.5 to $4 per watt. Therefore, a 250 MW@peak station would cost $600-1,000 million to build i.e. yield power at 12 to 18 cents per kilowatt-hour. A 1,000 MW@peak coal or gas powered electric power station requires about 1 square kilometer of space. A 1,000 MW@peak PV or mirror based power station requires about 20-25 square kilometers. These low efficiencies, enormous land area requirements and high installation costs are still the major barrier to reasonable ROIs in this industry. Government incentives and subsidies are invariably involved in any small scale (home 3 KW systems—cost: $7,000 per KW) to large scale (50 MW and up) installations.
The inventors hereby incorporate all of the above referenced patents into his specification.

SUMMARY OF THE INVENTION

The present invention is generally directed to a solar energy collection array which includes a plurality of individual mirrors and a plurality of receiver facets.
It is a first aspect of the present invention that the mirrors form a fixed multifaceted curved collection of mirrors. Each individual mirror is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces.
It is a second aspect of the present invention that the receiver facets are disposed as fixed curved multifaceted receivers. Each receiver facet is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces. Each individual mirror is aimed at one of the receiver facets so that each receiver facet is optically aligned with one of the individual mirrors thereby creating a small mirror multiple target. Different facets are utilized at different times of day and season based on the sun's position.
Other aspects and many of the attendant advantages will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawing in which like reference symbols designate like parts throughout the figures. The features of the present invention which are believed to be novel are set forth with particularity in the appended claims.

DESCRIPTION OF THE DRAWING

FIG. 1 is schematic drawing of a small mirror multiple target (SMMT) for a solar energy collection array according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 a small mirror multiple target (SMMT) 110 for a solar energy collection array includes a plurality of individual mirrors 111 and a plurality of receiver facets 112. The mirrors 112 form a fixed multifaceted curved collection of mirrors. The receivers facets 112 are as fixed curved multifaceted receivers. Each mirror 111 is aimed one of the receiver facets 112. The individual mirror and receiver facets are small (less than 1 square meter each) and are constructed of inexpensive and easily replaceable surfaces. These are not focal plane focusing arrays (such as parabolic or Fresnel mirrors). Different facets are utilized at different times of day (and season) based on the sun's position. A larger installed mirror/collector area is required compared to concentrating systems but this is easily offset by the lowered installation and maintenance costs.
The rise in fuel prices in the world and environmental concerns have accelerated efforts to develop viable energy production through absorption of the energy of sunlight. This is currently done by several known methods—Photovoltaic (PV) panels—directly convert light into electric energy and solar mirrors to redirect/concentrate solar power (CSP) onto a target heat collector which drives a generator. PV facilities can be very large but also the size of an average house roof. CSP facilities require very large space, are typically far from cities and require transferring electricity over long distances and expensive routine maintenance. Construction costs of these facilities are huge. The result is power which is typically 3 to 5 times more expensive than common fossil fuel or nuclear technologies. An inherent drawback in solar energy utilization is the lack of energy input during night time and therefore, the need to store energy during the day for distribution during the night. The current technologies utilize expensive parabolic or tubular mirrors and complex solar tracking mountings. Heat is concentrated and delivered to a target which heats up the boilers used to drive the generators. We propose fixed multifaceted curved collection mirrors aimed at fixed curved multifaceted receivers. The individual mirror and receiver facets are small (less than 1 square meter each) and are constructed of inexpensive and easily replaceable reflective foil (aluminized plastic) surfaces. These are not focal plane focusing arrays (such as parabolic or Fresnel mirrors). Instead, different facets are utilized at different times of day (and season) based on the sun's position. A larger installed mirror/collector area is indeed required compared to concentrating systems but this is easily offset by the lowered installation and maintenance costs. One of the major maintenance problems of solar mirrors is dust and grime which collect on the mirror surfaces. The proposed foil surfaced mirrors will be constructed of long strips of foil which are rolled on the two sides or the surface and are continuously scrolled from one side to the other side. A simple fixed brush cleans the foil passing under it. Excess heat generated by the Small Mirror Multiple Target (SMMT) Solar Energy Collection Array will be stored by conduction via fluid filled metal pipes (heat exchanger) into an insulated underground sand/gravel heat accumulator. The sand will heat up to hundreds of degrees celcius during the day. At night, the fluid filled pipes will be used to collect the accumulated heat energy and deliver it to the boilers running the generators. Unlike existing mirror array facilities, SMMT is also suitable for small courtyards or roofs of domestic buildings and factories. Small local facilities save power and transportation costs as opposed to the giant facilities located away from the city that require expensive delivery infrastructure.
A fixed multifaceted curved collection of mirrors each of which is aimed at fixed curved multifaceted receivers. The individual mirror and receiver facets are small (less than 1 square meter each) and are constructed of inexpensive and easily replaceable surfaces. These are not focal plane focusing arrays (such as parabolic or Fresnel mirrors). Different facets are utilized at different times of day (and season) based on the sun's position. A larger installed mirror/collector area is required compared to concentrating systems but this is easily offset by the lowered installation and maintenance costs. Neither an aiming technology nor an expensive fabrication is required. Power generation uses accumulated heat to drive a working fluid. Conversely, heat can be used directly for HVAC, drying operations or industrial processing. The cost per m2 is expected to be below one third of current technologies. Roof-top installation is practical and this is the first rooftop installable CSP system!
From the foregoing it can be seen that a small mirror multiple target for solar energy collection array has been described. It should be noted that the sketches are not drawn to scale and that distances of and between the figures are not to be considered significant.
Accordingly it is intended that the foregoing disclosure and showing made in the drawing shall be considered only as an illustration of the principle of the present invention.

Claims

What is claimed is:

1. A solar energy collection array comprising:

a. a plurality of individual mirrors forming a fixed multifaceted curved collection of mirrors wherein each of said individual mirrors is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces; and

b. a plurality of receiver facets being disposed as fixed curved multifaceted receivers wherein each of said receiver facets is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces and wherein each individual mirror is aimed at one of said receiver facets so that each receiver facet is optically aligned with one of said individual mirrors thereby creating a small mirror multiple target (SMMT) wherein different facets are utilized at different times of day and season based on the sun's position.