A DEVICE AND A METHOD FOR UTILIZATION OF SOLAR RADIANT ENERGY EMPLOYING TRANSPARENT PASSAGEWAY AND HEAT TRANSFER FLUID WITH DEFINITE COEFFICIENT OF ABSORPTIVITY AND A HYDRAULIC SYSTEM USING THESE DEVICE AND METHOD

Abstract

The present invention relates to a device and method for utilization of solar radiant energy employing transparent passageway and heat transfer fluid with definite coefficient of absorptivity and a hydraulic system using thereabove. The device of this invention is a flat panel comprises a base member, extruded from transparent rigid material, two collectors imperviously attached to the both opposite transverse ends of the base member and four lids arranged to close imperviously the openings of the collectors. The method of utilizing solar energy used in this invention is held by absorbing solar radiant energy directly in heat transfer fluid which coefficient of absorptivity is exactly definite. Such kind of heat transfer fluid can be a solution, colloidal solution or suspension of carbonblack and non frozen fluid as ethylene-glycol, or water based fluid.

Description

BACKGROUND OF THE INVENTION

Many devices for utilizing solar energy have been developed. Among the various known solar collectors are structured employing insulating base, a transparent cover spaced thereabove, and black fluid-carrying piping between the transparent cover and the insulating base, which are used effectively utilizing solar energy. The majority of solar collectors presently in commercial use utilize metal tube affixed in heat transfer relationship with a blackened metal plate. The heat transfer fluid (water or antifreeze) is passed through the tube and into a hot water tank or other reservoir directly or through heat exchanger.

The total radiant heat energy absorbed and emitted by a surface is proportional to the fourth power of its absolute temperature (Stefan-Boltzmann law) and the nature of the surface as well. Objects that are good absorbers are also good emitters (Kirchhoff's radiant law). A blackened surface is an excellent absorber as well as an excellent emitter of radiant energy. In the solar panels mentioned above, the solar radiation is transformed into useful heat energy by the blackened metal plates. Then by conduction, the heat energy is transferred to the metal tubes and by convection, to the fluid flowing inside the tubes. Conduction heat exchange depends on the thickness and the type of metal used for the blackened plate, and of the quality of the fixation between the plate and the tubes. Even though the conductivity of all metals is sufficiently high, the conductivity in the surface contact between the tube and the plates is low, because of the so called contact resistance. As a result of the corrosion of the contact surfaces the contact conductivity has a tendency to get even worse with time. This leads to an increase in the temperature of the blackened plates and consequently to a significant increase in the heat lost by radiation because as was mentioned before, the heat lost by emission is proportional to the fourth power of the temperature. The convectional heat exchange between the tubes and the fluid flowing inside them depends on the physical condition of the flow. The turbulence increases the heat exchange while steadiness decreases it. In most solar heating collectors that are presently in commercial use the tube diameter is 0.5 inch or more, and the fluid flow inside the tube is basically in laminar state. On the other hand, normally the water contains some amounts of calcium and magnesium carbonates which with time lead to the formation of a hard, adherent scale on the inside walls of the pipes. During exploitation, as a result of the corrosion on outside surfaces of the tubes and the blackened plates and the scale formed on the inside walls of the tubes, the heat transfer significantly decreases, notably reducing the thermal efficiency of the solar systems. This process shortens the period of time that the panels can be used efficiently, long before the expiry of the materials used for their fabrication.

Another group of solar collectors described in U.S. Pat. Nos. 1,042,418; 2,680,437; 3,215,134; 3,918,430; 3,965,887; 4,062,350, and many others, comprise of two or more plastic or metal sheets—flat or wavelike (corrugated). The fluid used for heat transfer passes between those sheets. These types of solar panels avoid some of the disadvantages of the previously described ones. But the marketing of such panels was not successful because of manufacturing difficulties.

Another widely used type of solar panels is the thin film solar panel. One such thin film solar heater is disclosed in Yellott U.S. Pat. No. 3,146,774 and uses water at essentially atmospheric pressure which is allowed to flow downwards within a thin film behind a heat absorber collector such as a pliable plastic film. Other elastomeric or plastic water heaters have been disclosed in Andrassy U.S. Pat. No. 3,022,781, and Okuda U.S. Pat. No. 3,029,806.

A solar heater disclosed in A. Meagher U.S. Pat. No. 3,239,000 includes a box, having two end walls, and two side walls. A pane of glass or other transparent material preferably covers the top of box, and is supported on a number of transverse rigid members, the ends of which rest on cut-out portions of the side walls. A number of tubular sections are provided for the solar water heater, which are preferably formed of a polymerized resin material impregnated with carbonblack. Two headers are provided for the solar water heater, which comprise an elongate member formed from a polymerized resin, rubber, or like material, having the transverse cross section. In transverse cross section the header includes a circular portion having two diametrically opposed ribs projecting therefrom. Two spaced, parallel flanges project outwardly from portion in a direction normal to ribs, with the flanges being in communication with a longitudinally extending opening formed in circular portion. The flanges are spaced apart a distance, which is substantially the same as the distance between the exterior surfaces of side walls. The process of assembling the tubular sections and headers to form a part of a solar water heater includes of cutting a number of tubular sections of the same length, and step-by step glue each to other and to the headers. A brush is utilized to apply the adhesive.

Each of these devices is provided to be disadvantageous for one or more reasons. The main disadvantages of the above described solar panels are low thermal efficiency, constant heat transfer capability and difficulties to be manufactured by automated production lines. Additionally, each of the prior art methods and apparatuses are relatively expensive. It is necessary to point out to the wide range of solar radiant energy available. It depends of the weather condition, the seasons and the geographical region. Each particular engineering project for solar heating system should be designed in such a way as to be capable to produce the required quantity of heat even in the worst possible solar radiation conditions. This presumes a large number of solar panels to obtain enough heat transfer surface. However during the times of maximum solar radiation such a system will generate large amounts of heat, due to the constant heat transfer capability of the present devices. As a result the temperature increase to a level at that the heat losses by radiation are commensurable to the useable heat transfer. Such high temperature is also dangerous for the system itself. This problem can be resolved by using a system with variable heat transferring capabilities.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a device and method for utilization of the solar radiant energy employing transparent passageway and heat transfer fluid with definite coefficient of absorptivity and a hydraulic system using thereabove.

The device of this invention is a flat panel which comprises a base member, extruded from transparent rigid material, two collectors imperviously attached to both opposite transverse ends of the base member and four lids arranged to close imperviously the openings of the collectors.

The base member consists of three chambers. The upper insulating chamber is provided to be transparent for sun radiation and contains air as insulation. The middle chamber is designed as a passageway for the heat transfer fluid. The bottom insulating chamber can be filled up with insulation material such as polyurethane or polystyrene foam or could contain air. All chambers are divided by numerous longitudinal ribs conjoining their walls.

A variant of the base member exists where the middle chamber is designed without the longitudinal ribs. In this variant a passageway, manufactured from material with deferent physical and mechanical properties can be inserted within the base member. Using this variant of the base member also gives the possibility to insert a solar radiance controlling screen parallel to the base member. This screen can use the liquid crystal phenomenon for automatic control of its transparency depending on temperature of the heat transfer fluid.

The collectors are designed with two chambers. A central tubular chamber which is used to collect the heat transfer fluid and has a slit through its wall, and concentrically to it there is an insulation chamber. Each chamber has a couple of conjunctive strips to be imperviously connected to the respective fluid passageway and insulation chambers of the base member. Both chambers are connected to each other by ribs.

The lids are designed to close imperviously the transverse openings of the collectors and have nipples for connecting the panel to the tubing of the water heating system.

The above described device is designed to be used for both open and close loop water heating systems.

The essence of the method of utilizing solar energy used in this invention is that the solar radiant energy is absorbed directly by the heat transfer fluid which has a definite coefficient of absorptivity. Such a heat transfer fluid can be for example a colloidal solution or a suspension of carbonblack in a non-freezing fluid such as polyethylene-glycol, or a water based fluid. Further using a specially designed hydraulic system consisting of two or more reservoirs makes possible the application of heat transfer fluids with different coefficients of absorptivity depending on the intensity of sun radiation. This provides flexibility to the system with different levels of utilization of the solar energy depending on the season and region and allows for safely using solar panel batteries with large surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents the top and the right views and several partial section views of the assembled panel.

FIG. 1A presents the panel composed with unparallel collectors.

FIG. 1B presents the top and right views and several partial section views of the assembled variant of the panel with inserted passageway section.

FIG. 2 presents several views of the base member of the solar panel.

FIG. 2A presents the second variant of base member, where the middle chamber is free of dividing ribs.

FIG. 3 presents the shape of the collectors.

FIG. 4 presents several views of the lids.

FIGS. 4A and 4B present several view of lids used in panels arranged with unparallel collectors.

FIG. 5 presents an isometric sectional view of the assembled panel.

FIG. 6 presents a partial isometric view of the passageway insert.

FIG. 7 presents a sectional view of the second variant of base member with inserted passageway.

FIG. 8 presents a partial sectional view of the base member from FIG. 7 with additional insert as a solar radiation controlling screen.

FIG. 9 shows a sample of system utilizing solar energy with a solar panel battery fully covering a house roof.

FIG. 10 present a sample of hydraulic diagram of system utilizing solar energy designed with two reservoirs containing heat transfer fluids with different coefficients of absorptivity.

FIG. 11 shows the shape of the heat insulated tubing used for systems utilizing solar energy.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings attached, the described device for utilization of the solar radiant energy generally consists of a base member 2, two collectors 3, and four lids 4 as shown in FIG. 1.

The base member 2 (FIG. 1) is a long body manufactured by continuous process of extrusion of rigid material transparent for the sun radiation. It consists of heat insulating chambers upper 207 and lower 209, (FIG. 2 view K) formed between walls 202, 205, 208, 212 and, 205 203, 210, 212 respectively. A number of longitudinal ribs 206 and 211, link wall 208 with 202 and 203 with 210, forming a firm body. The lower insulating chamber could be coated with reflective material such as silver to prevent heat losses by radiation. Between chambers 207 and 209 is located a chamber 200 designed as a passageway for the heat transfer fluid. Series of longitudinal ribs 204 transverse the walls 202 and 203 thus forming numerous longitudinal ducts 201. The transverse ends of the base member are cut in such a way so that the passageway 200 is longer than the insulating chambers 207 and 209 with a size “d” (about ¾ of inch). During the cutting, shallows grooves 213 (FIG. 2 view H) are formed on the walls 202 and 203. Another variant of the base member is shown on FIG. 2A. It consists of the same heat insulating chambers 207 and 209, ribs 206 and 21 1 transverse wall 208 with wall 202 and wall 203 with wall 210, and a chamber 201A, designed without transversal ribs. This configuration of the base member makes possible the insertion of a passageway within the middle chamber 201A. This passageway can be manufactured from a material with deferent mechanical and physical properties such as glass, more expensive plastic material, metal or other. The shape of such a passageway is shown in FIG. 6.

The collectors 3 (FIG. 1) shown on FIG. 3 are manufactured by continuous extrusion process and cut to a length equal to the width of the base member. Both collectors in the device have equal shape and are attached imperviously to the transversal ends of the base member thus linking the passageway. The collector consists of a tube 34 having longitudinal slit 33 whose width corresponds to the inside dimension of the longitudinal ducts 201 of the passageway (FIG. 1 view B). On both sides of that slit are incorporated two joining stripes 32 and 32a (FIG. 3 view M) with length “k” equal to the length “d” of the passageway 200 (FIG. 2). The distance “b” between the joining strips 32 and 32a corresponds to the thickness “e” of the passageway (FIG. 2 view H). On the inside walls of the joining strips are designed triangle-shaped teeth, 36 and 36a (FIG. 3 view M) with position and elevation corresponding to the shallows grooves 213 (FIG. 2 view H). After the assembly, (FIG. 1 view C) these teeth and grooves increase the mechanical strength of the construction. Concentrically to tube 34 there is a casing 38, having tangentially attached flat walls 31 and 31a. The inside distance “c” between the flat walls 31 and 31 a corresponds to the thickness “f” of the base member (FIG. 2) and its length “g” is approximately twice the length “k” of the joining strips 32 and 32a. The tube 34 and casing 38 are connected to each other by ribs 37, 37a, and 39, thus forming heat insulating space 35 and 35a. This heat insulating space could be filled up with polyurethane foam or left free of additional insulation.

The lids shown on FIG. 3 are designed to close imperviously the openings of the collectors. All lids are identical and are fabricated by mold injection process. FIG. 4 shows the shape of the lid. It consists of a flat surface 48, shaped as the cross-section of the collectors 3 FIG. 1. At the peripheral edge of the flat surface is mounted a strip 34 and tangentially to it ribs 44 and 49 having steps 47 at theirs ends. A cylindrical portion 42 is incorporated into the flat surface 48, concentrically to the strip 43 and with outer diameter equal to inner diameter of the tube 34 of the collector 3 (FIG. 3). A groove 46 is provided to correspond to the longitudinal slit 33 of the collector (FIG. 3). A square pin 45 mounted at the basis of groove 46 of the cylindrical portion 42 is provided to close securely and imperviously the end of the slit 33. A connecting nipple 41 is attached to the flat surface on the opposite side of the cylindrical portion 42.The nipple is provided to join the solar panels in a battery and to the installation tubing.

During the assembling process all contact surfaces of the assembled parts have to be covered with a thin film of sealing adhesive. Due to the small number of the parts comprising the solar panel device it could be assembled on an automatic production line with no significant investments.

The drawing on FIG. 9 presents a sample of solar water heating system which uses a battery built from the panels described above. The flexibility of this solar heating device allows existing roofs to be almost fully covered by panel array using the design of the panel shown on FIG. 1A.

Another object of the present invention is a method for utilizing the solar radiant energy by it direct absorbing from a fluid having a definite coefficient of absorptivity. Such a heat transfer fluid can be a colloidal solution or suspension of carbonblack and non freezing fluid as ethylene-glycol, or water based fluids. This method provides an opportunity to significantly decrease the heat losses by radiation, which is the main disadvantage of the similar devices that exist on the market.

Further on, another object of the present invention is a hydraulic system shown on FIG. 10 that enables the use of heat transfer fluids with different coefficient of absorptivity. This provides flexibility to the solar water heating systems with respect to the solar radiation levels. FIG. 10 shows such a system, wherein 101 is a battery built from the above described solar heating device, 102 is a heat-exchanger, 103 is a pump, 104 105, 106 and 107 are electro-actuated valves, 108 and 109 are maximum pressure relief valves electrically operated. The purpose of these valves is to prevent draining of the fluid, and to hold up about 10 psi pressure in the system. The reservoirs 110 and 111 contain heat transfer fluids with different coefficient of absorptivity, 113 is a float type air vent and 112 is a temperature sensor. A simple electrical circuit (not shown) controls the function of the system. When the temperature of the heat transfer fluid is less than 130° F. the pump is off, valves 104 and 106 are open valves 105 and 107 are closed. If the temperature rises above 130° F. the pump starts up and the fluid from reservoir 110 begins circulate. If the temperature increases up to 200° F. the pump turns off, pressure valve 108 opens and the fluid drains gravitationally in the reservoir 110. During the draining the float type air vent 113 opens because of the vacuum formed and the system fills up with air. This procedure continues about 10-20 minute depending on the volume of the installation and is determined by an adjustment of a timer. When the timer switches over, valves 104 and 106 close, valves 105 and 107 open and the pump turns on. Thus the pump sucks heat transfer fluid with lower coefficient of absorptivity from reservoir 111, the air blows out from air vent 113 and the system start works at a lower efficiency. This procedure continues until the temperature drops down to 190° F. Then the pump stops, valve 109 opens the fluid drains in reservoir 111, valves 105 and 107 close, valves 104 and 106 open, the pump turns on, and the system starts using heat transfer fluid with higher coefficient of absorptivity from reservoir 110. During the time of low sun radiation when the temperature of the heat transfer fluid decreases below 130° F. the pump stops operating until the temperature increases above 135° F. All temperature and time ranges are as an example only and could vary depending on the capacity of the system and geographical region of operation.

Claims

1. A device for utilization of solar radiant energy consists of:

a base member

collecting means, attached imperviously to the transversal ends of the base member

closing lids attached imperviously to the openings of the collecting means.

2. A device for utilization of solar radiant energy as claimed in claim 1 wherein the base member is a long flat monolithic plate extruded from rigid material transparent for the sun radiation having three chambers partitioned off by four walls, two heat insulating outward chambers and one in the middle designed as a passageway, the walls are connected each other by longitudinal ribs thus forming a firm solid body.

3. A device for utilization of solar radiant energy as claimed in claim 2 wherein the walls defined the middle chamber are coated by a material having high coefficient of absorptivity.

4. A device for utilization of solar radiant energy as claimed in claim 2 wherein the middle camber is designed without the longitudinal ribs in such a way so that a separately manufactured passageway can be inserted in it.

5. A device for utilization of solar radiant energy as claimed in claim 2 wherein the walls of the lower insulation chamber are coated with reflective film.

6. A device for utilization of solar radiant energy as claimed in claim 1 wherein the collecting means is an extruded long body consisting of a central tubular opening having longitudinal slit through the wall, on both sides of that slit are incorporated strips, concentrically to the central tubular opening there is a casing having tangentially attached flat walls, the tubular opening and the casing are connected by longitudinal ribs thus forming a firm body.

7. A device for utilization of solar radiant energy as claimed in claim 1 wherein the closing lids are designed in manner to close imperviously collectors' openings and have a nipple for connecting the device for utilization of solar radiant energy to the system.

8. A method for utilization of solar radiant energy which expresses of direct transformation of the solar radiant energy to usable heat energy within a heat transfer fluid.

9. A method for utilization of solar radiant energy as claimed in claim 7 wherein the heat transfer fluid is a solution, colloidal solution or suspension of a substance with high coefficient of absorptivity.

10. A method for utilization of solar radiant energy as claimed in claim 8 wherein the solution, colloidal solution or suspension is carbonblack in ethylene glycol.

11. A method for utilization of solar radiant energy as claimed in claim 8 wherein the solution, colloidal solution or suspension is a blend of substances with different monochromatic absorptivity.

12. A hydraulic system consisting of array of devices for utilization of solar radiant energy as claimed in claim 1, at least two containers with heat transfer fluids having definite coefficient of absorptivity of radiant energy, employing the method as claimed in claim 7.