DE8806127U1 - Solar collector - Google Patents

Description

The innovation relates to a solar collector with an absorber that is largely designed as a black body, which is housed in an elongated absorber housing that is filled with collector fluid flowing in the longitudinal direction and that is designed to be radiation-permeable with low losses at least on the sun side, as well as with a cover housing provided at least on the sun side that insulates against heat conduction and radiation losses.

Solar collectors of the type mentioned above suffer from losses for various reasons which impair their efficiency to such an extent that their use in areas with cool weather, i.e. cool or low air temperatures and frequently overcast skies, is called into question because it is hardly possible, or not possible at all over long periods of time, to collect enough heat to prepare hot domestic water or to make the operation of a heat pump economical.

There are many suggestions to reduce the losses mentioned and thus increase the efficiency, but this requires expensive measures and materials, and it is often necessary to accept that the solar panels become extremely heavy. The high weight of solar panels often prevents their use, for example if they are to be installed on roofs, but their load-bearing capacity is suitable for the high weight of the solar panels. Expensive materials and other expensive measures lead to high purchase prices or investment costs, so that

particularly in areas where the energy yield is already low, the cost amortisation is called into question.

A large part of the losses mentioned occur in the known solar collectors because the desired and achieved increase in temperature of the collector fluid or the absorber creates a temperature difference between them and the environment. Heat flows through direct heat conduction or convection from the higher temperature location towards the lower temperature location. This heat conduction or convection acts like a leak through which solar energy converted into heat constantly flows away. These losses can be reduced by thermal insulation measures on the sides and back of the solar collector, but this increases the volume and weight of the solar collector. On the sun side, however, thermal insulation is more difficult because the energy yield depends on the unhindered, as low-loss as possible entry of sunlight into the absorber housing. Therefore, cover housings are used that are designed according to the principle of double-glazed windows. Such cover housings are most effective when there is a vacuum between their two transparent plates; however, such cover housings are naturally very expensive and have a high weight.

Another loss factor is the heat emission through radiation. Every warm body loses heat through radiation, i.e. emission, which is in the infrared range, even without heat conduction. Gases and liquids also radiate heat. Such radiation heat is the

The reason for this is that insulation of the type mentioned above also heats up in solar collectors, so that solar energy that has already been converted into heat is lost.

Since the cover housing must be permeable to radiation so that the solar collector can work, the greatest radiation losses occur through the cover housing. Solutions are already known for using selectively permeable glass or layers on the cover housing in order to reduce these radiation losses, but such techniques are very expensive. However, such selective permeability to radiation in the cover housing often also leads to a certain loss of permeability to radiation in the desired direction, so that less solar energy reaches the absorber or the collector fluid than without these selectively permeable layers.

The third cause of loss occurs in the absorber itself. The concept of the black body or the black surface is a physical ideal that does not exist in practice. The black body or the black surface is supposed to absorb all incident radiation without reflection. However, absorbers that can be manufactured in practice inevitably reflect more or less large proportions of the incident sunlight. However, sunlight reflected in this way cannot be converted into heat.

A solar collector of the type mentioned above is disclosed in DE-OS 28 26 937. This known solar collector has a cover housing in

Double glass technology and, arranged at a distance below, an absorber housing. Water is used as the collector liquid, and the absorber, which approximates the conditions of a physical black body, is to be formed by the collector liquid. For this purpose, it is mixed with organic or inorganic color pigments in soluble form and distributed as finely as possible.

This well-known flat collector is neither intended nor suitable for reducing the three types of losses mentioned. Since both housings, namely the absorber housing and the cover housing, are intended to be able to be controlled by collector fluid, the cover housing cannot be used to protect against losses due to heat flow and radiation. The losses that usually occur due to heat radiation and heat conduction on the back of the sunny side are, to a certain extent, desirable with this well-known flat collector, because it is intended to serve as a roof element for air conditioning halls, greenhouses, sports halls and the like. Since these absorbers are intended to be roof or ceiling elements for greenhouses, sports halls, etc., but also to let in daylight, it goes without saying that the collector fluid with the absorbed, finely distributed pigments must be very far removed from acting as a physically black body, because otherwise it would not be able to let in daylight. The well-known flat collector may therefore be useful for air conditioning halls and houses to provide shade from bright sunlight, but as a solar collector it has a very unsatisfactory level of efficiency.

Based on this state of the art, the innovation is based on the task of designing a solar collector of the type mentioned at the beginning in such a way that, through cost-effective, space- and weight-saving reduction of the losses described, such a high level of efficiency is achieved that even in bad weather, temperatures of the collector fluid are achieved that are suitable either for direct heat use for domestic water or the like or for the economical operation of a heat pump.

To solve this problem, the solar collector mentioned at the beginning is characterized according to the innovation in that the absorber is a solid body in the form of a roll or sheet that is folded in an accordion-like manner parallel to the length of the absorber housing, with the folds having slightly concavely curved flanks facing each other on the sun side, that the absorber is black on the sun side and on the back, that an unfolded, flat absorber runs across the rear tips of the folded absorber and is black at least on the back, that a reflective or radiation-reflecting surface is arranged on the back behind the folded absorber, and that a heat-insulating body is provided behind the reflective surface.

The measures of the innovation are primarily aimed at optimizing the absorption of sunlight. A film-like or sheet-like, solid body as an absorber can be made so thin that the usual temperature difference between the absorber surface and the absorber core, which is considered a disadvantage, becomes negligible because the thickness is negligible. Because

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immediately and immediately released into the flowing collector fluid.

If the collector fluid also washes over the sunny side as;&ogr; the concavely curved flanks facing each other, reflections occur through the collector fluid and have the further effect that the collector fluid is also heated to a certain percentage.

Just as a black body emits, i.e. loses heat through radiation, and the warmer it is, the more heat it emits, the surfaces of the accordion-folded absorber radiate heat both on the sun side and on the back. During these radiation processes, the concave curvature of the fold flanks facing each other on the sun side, i.e. wave sump or wave trap, holds back a large part of this radiation. However, heat is also radiated from the back. Therefore, another flat, i.e. airtight absorber, which is at least black on the back, is spread out over the tips of the back of the folded absorber.

This measure means that the heat radiated from the back is either absorbed by the flat absorber or reflected against the back of the folded absorber and absorbed again there, and therefore cannot be lost. The black back of the flat absorber makes it possible to recover as much of the heat as possible that could result from the heating of the absorber housing, the collector fluid, etc. and that would be lost through radiation.

The black back of the flat absorber is ^particularly effective when a reflective surface is provided between it and a heat-insulating body behind the absorber housing, which insulates the latter against heat conduction losses. This means that all the heat energy that could be lost through radiation towards the heat-insulating body is optimally reflected against the flat absorber and converted into heat, which is passed on to the collector fluid.

This means that the efficiency losses of known solar collectors are significantly reduced in an astonishingly simple and effective way. The low yield due to the refracting action of sunlight is avoided by the wave traps or wave sumps created. The losses due to radiation are kept very low by reflection and the black surfaces on the back of the absorber. The result is that the efficiency of the conversion of sunlight into thermal energy is extremely high, and this without the cover housing having to be designed to be selectively permeable to radiation, which is therefore expensive. Even inexpensive materials such as plexiglass can be used for the cover housing and the absorber housing. This significantly reduces the price of a solar collector and also reduces the weight, which is very important in many applications.

An zig-zag-shaped absorber is disclosed in US-PS 46 49 902. However, it is not specified whether this is a spiral or a folded, flat body, and it is

only a remote application is possible because evaporated liquid, i.e. steam, is passed through this absorber as the collector medium. Regardless of whether steam or liquid is used as the heat transfer medium, a zigzag-shaped folded surface offers the advantage of an increase in surface area, but it cannot avoid the not inconsiderable losses due to reflection, so that the efficiency remains unsatisfactory despite accordion-like folded surfaces. Since this publication says nothing about radiation losses to the rear and also contains no disclosures as to how such heat conduction or radiation losses are to be avoided, the use of a zigzag-shaped absorber, which can be viewed more as a heating coil, cannot provide a solution to the problem underlying the innovation.

According to another feature of the innovation, the concave curved surfaces of the folded absorber are black and shiny as "non-Lambert-like" surfaces.

This measure achieves a further, significant increase in efficiency. This measure allows for a large-scale avoidance of the losses that would have been caused by radiation as emitted heat radiation from the surface of the absorber. The inventive measure with which this success is achieved appears at first glance unreasonable and wrong, because a shiny surface reflects more strongly than a matt surface, even if it is black. If the folded absorber were not designed in such a way that the

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If the flanks facing each other on the sun side are concavely curved, the surface could not be made black and shiny, because then there would be significant losses due to reflection. However, because the space between two concavely curved flanks facing each other acts as a wave sump or trap, it does not matter how often the captured sunlight is reflected back and forth between the facing flanks. The energy of the light is converted into heat in any case.

To avoid the losses caused by Heat radiation from the heated absorber is

However, it is of considerable importance that the sun-facing surfaces of the concave curved

Flanks are shiny black. The reason

This is based initially on the Kirchhoff vision

Radiation law, according to which the relationship between Emissivity and absorption capacity of a body

is the same for every wavelength and temperature.

Regarding the surfaces of a body, however,

the radiation from a matt surface that Lambert's law is effective. In a Lambert we see

A sphere is formed if the light intensities

as correspondingly long arrows from a !-mission point from in different directions.

The tips of the arrows lie on the surface of a Sphere, which is the surface element that radiates,

The situation is different for a so-called

non-Lambertian surface, ie a non-matt, ·]'

but shiny surface. With such a

non-Lambertian, i.e. shiny surface^ arises as f, characteristic of reflection or emission none |

• ·· II III ·· ·

sphere, but rather a body that is more like an ellipsoid. The greatest radiation intensities run at right angles to the radiating surface or approximately at right angles, while the radiation power is significantly reduced in smaller angle ranges.

If the sun-facing surfaces, i.e. the concave curved surfaces of the folded absorber, are now designed as non-Lambertian surfaces, they also emit radiant heat. But the main amount or main energy that arises from the heat radiation itself is essentially radiated at a right angle to the surface. This means

• that this radiation hits the opposite flank, where it is partly absorbed and partly reflected. The same applies to these heat rays

&bull; about that _<the mutually facing, concavely curved flanks of the folded absorber act as a wave sump or &bull;trap, i.e. heat is radiated, but it is absorbed again and converted into heat.

Of course, losses still occur due to emissions from the absorber, even with the new technology. However, they are only a fraction of the losses that occur with known tonnoko I absorbers.

If the solar collector according to claim 1 is combined with the further inventive design, a previously unattainable, almost utopian level of efficiency is achieved. Heat loss through conduction is kept within limits by the cover housing. The accordion fold of the absorber multiplies the absorber surface area. The concavely curved design of the sun-facing flanks of the folded absorber

creates a wave pool, with the result that there are hardly any losses due to reflection of the incident light. The losses due to heat radiation towards the sunny side are reduced to a fraction of the usual level by designing the concavely curved surfaces as non-Lambertian surfaces. The effect of all these measures means that the sunny side of the solar collector designed in accordance with the innovation comes much closer to the theoretical black body than all previously known solar collectors. This special effect is made even more valuable by the fact that no expensive technology or high-quality materials or measures that increase volume and weight are required. Rather, the high absorption efficiency allows concessions in the choice of material and design for the absorber housing or the cover housing. Such concessions can be advantageous for reducing volume and weight. The measures that prevent radiation and losses to the rear serve to preserve the heat gained. This includes the black back of the folded absorber, the black back of the flat absorber, the reflective surface and heat- insulating bodies.

According to claim 3, the sun-facing fold tips of the folded absorber are slightly wave-shaped across their length.

Due to this profiling, vortices are created in the flowing collector fluid, which promote the heat transfer from the absorber to the collector fluid.

According to claim 4, it is provided that thin or fine black metal nets, folded more bluntly than the absorber, are inserted on both sides between the folds of the absorber with the fold tips pointing towards the back, and that a flat, black metal net is folded on the inside over the tips of the folds of the absorber.

As already mentioned, so-called light-Lambert surfaces can also prevent all radiation losses. If the black metal nets are installed according to claim 4, they act to a certain extent as auxiliary absorbers for the reflected light rays and the reflected heat radiation, particularly in the upper wide, pointed area of the folded absorber, due to their fineness. The flat, fine metal net, which is stretched over the tips of the folds of the absorber on the sun side, acts to a certain extent as the last auxiliary absorber surface for reflection and radiation losses. The folded, fine metal nets on the back have the same effect for the reflected heat radiation in this area. As the fine, black metal nets heat up through absorption, their large surface area helps to improve the heat transfer between the absorber and the collector fluid.

According to claim 5, it is provided that the collector liquid is mixed with suspended black dye.

In principle, due to the very high efficiency of the innovated solar collector, this could be done from the DE-OS 28 26 937 quoted at the beginning.

t ·■■!·· * ■<· a

This already known measure can be dispensed with, however, if the weather conditions are extremely bad, this measure can still help to ensure the economic operation of a solar collector even if the measures already mentioned are no longer satisfactory. Mixing the collector fluid with black dye has the advantage that it does not result in a high price, nor does it increase the weight or volume of the solar collector.

The newly designed solar collector can be implemented in various construction variants and can be ideally adapted to the given conditions.

In the embodiment according to claim 6, the cover housing and heat-insulating body are designed as a common Plexiglas tube with a circular cross-section, and the absorber housing is arranged in the middle of the Plexiglas tube. Such tubular solar collectors are useful wherever there are no large areas available, but only narrow, elongated areas. A vacuum can also be created between two coaxial tubes using Plexiglas. However, due to the extremely high efficiency of the solar collector designed in accordance with the innovation, it is also possible to work without vacuum technology using air as an insulating medium.

A particularly advantageous embodiment of such an embodiment is characterized in claim 7 by the fact that the absorber housing is designed as an inner P lexig las tube with a circular cross section, that the absorber housing is concentrically mounted in the outer P lexig las tube

is arranged so that the flat absorber
side of the inner Plexiglas tube facing away from the sun
inn &igr;? &eegr; half-shell-like covered that his, the
folded absorber facing side mirrored
Is formed, and that the outer Plexiglas tube on the sun-facing, cross-sectional half inside,
because I have a Len-like mirror finish.

In this design, the inner plexiglass tube is also the absorber housing, the flat absorber runs like a half-shell over the lower half and the outer plexiglass tube is mirrored inside like a half-shell, whereby the sunny side of the flat absorber can be
Absorber housing mirrored on the sun side and the
Back to increase the absorption effect
Be trained in black.

Another embodiment of this type is characterized according to claim 8 in that the absorber housing is designed as a flat, cuboid-shaped Plexiglas hollow body and is arranged diametrically in the outer Plexiglas tube, that the lower wall of the Plexiglas hollow body is mirrored on the inside, and that the folded absorber is arranged with the upper fold tips at a distance from the upper wall of the Plexiglas hollow body, and with the lower fold tips at a distance from the lower wall. In this
The absorber housing is a flat
cuboid-shaped Plexiglas hollow body, and it is ensured that both the folded and the flat
Absorber distance from the upper or lower wall of the

: Plexiglas hollow body, which is preferably

heat-insulating supports or the like
This measure ensures a
perfect, all-round flushing of the absorber with

K &ogr; LI '..· ^ } ;· f" ^r ';i 3 &tgr;&tgr;'j'' cit and at the same time prevents 3 heat from being transferred into the Plexiglas tube by conduction.

As already mentioned, in tube technology - due to the shape of the tube - regardless of whether a tube or a flat body is arranged in the plate as an absorber housing, vacuum technology can be used to conduct heat to the outside. The vacuum technology according to claims 6 to 9 ^has a low weight, small dimensions, a low ^price due to the materials required but a high level of efficiency.

line other design of the new

&bull; the solar collector disclosed in claim 10. This design is characterized in that a plurality of flat, square absorber housings running parallel to one another and communicating with one another at the ends are integrally combined in a Plexiglas lobe/web plate, that the folded and flat absorbers are each inserted into the hollow spaces at a distance from the lower and upper walls of the double web plate, that the reflective surface is arranged on the outside of the lower wall of the lobe/web plate, that the

&bull; ärmei soli &euro;·._"■ de body as plastic insulation plate

aB Styrofoam plate is formed and arranged adjacent to the back of the reflective surface, that the double-web plate and the plastic insulation plate are enclosed and held together by a rectangular frame consisting of inwardly open U-profiles, and that the frame has a connection nozzle for the flowing collector liquid on both end faces, diagonally opposite each other.

This design can be considered the most economical, least expensive version, because the so-called Plexiglas double-wall panels are commercially available as extruded items sold by the meter. They have formats that can be used to create suitable flat collectors as defined in claim 10. All that is needed is to use the cover housing and remove the webs in the middle area as the absorber housing so that the individual channels or parallel cavities communicate with each other to allow the collector fluid to flow through. Appropriate connection devices must of course be provided at both ends. All that is needed then is to insert the absorbers into the cavities. The reflective surface is applied to the outside rear of the absorber housing and a plastic insulating plate, e.g. a polystyrene plate, is placed against it as a heat-insulating body. The entire structure is combined into one element in a frame made of U-profiles with the interposition of spacers between the cover housing and the absorber housing and by applying sealing measures.

See also claim 11!

Due to the very high, previously unattained efficiency, an absorber according to claim 10 can be used without a cover housing and still achieve satisfactory results if an extremely flat design is required. Such an extremely flat design can be desired, for example, if roof hatches or skylights are to be replaced by solar collectors of this type. Where there is no shortage of space

the design according to claim 11 with cover housing is used, which naturally has the better efficiency.

Weather resistance and protection against heat insulation is provided by the further development according to claim 12 in that the plastic insulating body or plastic insulating plate is covered on its back with heat-insulating and weather-protection-providing plastic layer, for example glued on.

The further development according to claim 13 uses the cavity already present in the double-web plate to use those edges of the absorber housing that are in contact with the U-frame as insulation chambers, so that heat conduction losses into the frame are prevented. In complex designs, these chambers can also be provided with a vacuum.

The solar collector designed in accordance with the innovation is particularly inexpensive - regardless of the specific design - because all reflective surfaces are made of aluminum foil - claim 14 -. Aluminum foils are high-gloss on one side, matt on the back and are available in stores for a low price.

Materials that conduct heat well and are easily blackened can be used for the absorbers - the folded and the flat absorbers. According to claim 15, the folded and the flat absorbers are made of metal sheet that is no thicker than 1 mm, preferably 0.1 to 0.3 mm, with a blackened, if necessary, coating.

with a glossy black surface, whereby at least the folded absorber is elastically springy in its shape.

It is essential for the folded absorber to have an elastic, springy shape, as it can heat up considerably and expand accordingly due to the large area accommodated in the folds. The elastic, springy design is important so that it retains its shape and thus its effect during such thermal expansion.

According to claim 16, it is expedient for the absorbers to be made of copper. Copper can be blackened particularly easily, even provided with a shiny black surface, and has the advantage of being a good heat conductor.

As an alternative to using copper, aluminum can also be used for the absorbers according to claim 17. Aluminum has the advantage that it is considerably lighter than copper. Copper and aluminum are characterized by corrosion resistance if appropriate measures are taken, so that the service life and freedom from maintenance of the solar collectors are also ensured.

Examples of designs and explanations of the solar collector designed in accordance with the new design are shown in the drawings. They show:

Fig. 1 - a schematic sectional view of the basic structure,

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Fig. 2 - a sectional view of a possible design of the solar collector,

Fig. 3 - a schematic sectional view of a further embodiment.

Fig.4

+ 5 - graphic representation of the reflection behavior of the absorber flanks when designed as a Lambertian surface according to Fig. 4 and non-Lambertian surface according to Fig. 5,

Fig. 6 - an explanatory diagram for the design of the accordion flanks of the absorber as a wave sump or trap,

Fig. 7 - a sectional view of a particularly advantageous design of a flat collector,

Fig. 8 - a schematic plan view of the absorber housing of the flat collector according to Fig. 7 and

Fig. 9 - a perspective partial schematic view of the accordion-shaped absorber.

Fig. 1 shows a solar collector 1, which has the basic elements of the inventive design. On the solar side, a collector housing 2 is provided, which is made using double-glass technology. Behind this is an absorber housing 3, through which collector liquid 4 flows in the longitudinal direction. In the absorber housing 3, a concertina-shaped

folded absorber 5, the folds of which run in the longitudinal direction of the absorber housing 3 and thus in the direction of the flow of the colloidal liquid 4. The special feature of this folded absorber 5 is that the facing, sun-side flanks have concave curvatures 6, so that they can hold incoming light rays in the manner of a wave pool or trap, according to Fig. 6, whereby losses due to reflection of incoming light can be reduced to a minimum.

As Fig. 6 indicates with an optionally indicated light beam 7, this is reflected by a concavely curved surface 6, directed towards the opposite concavely curved surface 6, reflected again by this, etc. Since every reflection is also associated with absorption and energy is transferred to the absorber 5, the accordion-like folded absorber 5 with the concave surfaces 6 acts as a largely reflection-free solar absorber with a very high degree of efficiency.

Since the absorber 5 heats up due to the absorption of solar light, it also radiates heat, especially at the rear sides, which are also surrounded by collector fluid. To ensure that the energy that is radiated as heat from the rear is not lost, a flat absorber 8 in an unfolded version is placed against the tips of the folded absorber 5, which is designed as a black surface at least on its rear side facing away from the sun. According to the principle already described, heat radiation is also reflected by the flat absorber 8 and a major part is absorbed. The

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The reflected part hits the convex sides of the folded absorber 5, is absorbed and partially reflected. A radiation loss from the space delimited by the flat absorber 8 and the flanks of the folded absorber 5 is not possible.

Since the collector fluid 4 also heats up, the absorber housing 3 also heats up, the latter can also radiate heat undesirably. In order to avoid such losses,

prevent, can be on the inside of a lower |

Wall 9 -see dotted line in Fig. 1- or »

on the outside of such a lower wall 9 a

reflecting surface 10 must be provided, which ^!

Radiation losses are largely avoided by reflecting heat radiation. If the reflective surface 10 on the inside of the lower wall 9

arranged, the heat radiation of the ^J

of the heated absorber housing.

If, however, the reflecting surface 10 is arranged on the outside, the radiation emanating from the absorber housing 3, directed towards j

rear-directed heat radiation largely for

avoided. 1

Behind the absorber housing 3, either behind the lower wall 9 or the reflective surface 10, there is generally an insulating body 11, which is intended to prevent heat losses through heat conduction.

As already mentioned, an essential aspect for achieving a high efficiency of the solar collector is the measure of providing the folded absorber 5 with the concavely curved surfaces facing each other. This measure

prevents energy losses due to reflection of the incoming light, because the concave curved surfaces 6 facing each other act as a wave sump or trap.

However, if the absorber 5 itself is partially heated, it radiates heat itself. According to Kirchhoff's radiation law, the ratio between this radiation or emission and the absorption in a given body is the same for any length and temperature. This means that the body itself cannot influence the amount of emission or the radiation that causes losses.

On the other hand, there is Lambert's law, which takes the surface of the body radiating heat into account. If the light intensities of the radiation intensities that a Lambertian surface element radiates in the various possible directions are plotted with arrows in the corresponding directions in such a way that the length of the arrows corresponds to the radiation intensity, the tips of the arrows drawn in this way lie on a spherical shell, if it is a Lambertian, i.e. matt surface. See Fig. 4. This radiation behavior would result in the emission of the folded absorber 5 in the area between the concavely curved surfaces giving off undesirably large amounts of energy in the direction of the sun.

On the other hand, physics teaches that the emission of a non-Lambertian, i.e. shiny, surface exhibits a different behavior. The

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Principle for a non-Lambertian surface element, the arrows shown lie with their tips on a rotational ipsoid, the tip of which is on the surface element. This means that the majority of the emitted energy is radiated at right angles to the right amber surface and the main energies in directions that are close to the right angle. See Fig. 5! On the other hand, the radiation in directions that deviate very far from the vertical direction is significantly reduced. For this reason, the sun-facing, concavely curved surfaces of the absorber 5 are designed as non-Lambertian, i.e. shiny surfaces, but are black. In the flat absorber 8, the sun-facing surface can optionally be designed as a non-Lambertian surface, the back as a Lambertian surface.

This measure ensures that the main part of the emission, ie the heat radiation resulting from the heating of the absorber 5 or 8, is reflected back and forth between the concavely curved surfaces 6, particularly in the folded absorber 5. Since every impact of a beam on a surface is associated with an absorption of radiation energy and only a part of the impacting energy is reflected, the concavely curved surfaces have the advantage of also reducing the trillionths in connection with their opaque or black-glossy surfaces to the values that must be accepted with other absorbers.

To further increase the efficiency, the tips of the accordion-like folded

Absorber 5 has a thin or fine black metal net 12, which is folded at a more obtuse angle than the absorber 5, with the fold tip pointing downwards, inserted between the flanks of the folded absorber 5. In addition, another, flat, black metal net 13 is spread out over the tips of the folded absorber on the sunny side.

The effect of these measures is that the flat metal net 13 still captures a significant proportion of the emitted or remaining, small reflected radiation that can escape between the concavely curved surfaces 6, while the folded metal nets 12 lie in the path of the radiation reflection of both the incident light and the emitted light of the folded absorber 5 and the flat absorber 8 and thus convert radiation into thermal energy.

Since every radiation passage between the folded absorber 5 and the flat absorber 8 leads through collector liquid A, this is heated intensively both by radiation and in particular by contact with the heated surfaces, the absorbers 5 and 8 and the metal nets 12 and 13. Since both the absorbers 5 and 6 are very thin and preferably consist of sheet metal, such as copper or aluminum, which have good thermal conductivity, there is good heat transfer between absorbers 5, 8 or absorbing metal nets 12, 13 and collector liquid 5.

The efficiency of this absorber housing 3 is extremely high because hardly any reflected radiation and hardly any emitted radiation can be lost.

An additional improvement in efficiency can be achieved by adding black, finely distributed, suspended color pigments (not shown) to the collector liquid 4. This measure results in an additional absorption effect by the pigments each time a beam passes through the collector liquid 4 and immediate heating is achieved.

In order to ensure the shape and stability of the folded absorber 5 even when it is heated to higher temperatures, it is advisable to ensure that the accordion-like folded shape is elastically flexible, because thermal expansion can then be easily compensated.

The heat transfer from the absorber 5, 8 to the co I lector liquid 4 is particularly favoured by the extreme thinness of the absorbers 5, 8. Therefore, they should, as far as possible, have a thickness of around 0.1 to 0.3 mm. In addition, the transfer to the Collector fluid can be further improved by the fact that the tips of the sun side of the folded absorber 5 according to Fig. 9 have a slight wave profile 14 across their length. A wave profile at the tip causes vortex formation in the collector fluid flowing in the direction of arrow 15 in Fig. 9, which optimizes the heat transfer. In practice, the solar collector 1 shown and explained in principle in Fig. 1 can be implemented in different ways, depending on requirements, cost-effectively.

Fig. 2 shows a solar collector 1, in which an outer P Ie xig I as tube 16 and a coaxial inner

arranged Plexiglas tube 17 are provided. Both are coaxially arranged and kept at a distance. Air can be present between the two as a heat-insulating material. However, an airless space can also be provided. In both cases, however, the inner Plexiglas tube 17 also forms the absorber housing. Together with the outer Plexiglas tube, it forms the cover housing 2, and both together form the equivalent of a heat-insulating body 11 in the rear area. The folded absorber 5 is in this case inserted into the inner Plexiglas tube 17, i.e. the absorber housing 3, with its cross-section filled, and the flat absorber 8 covers the inside of the inner Plexiglas tube 17 in the lower, rear area in the form of a half-shell. It is mirrored on the sunny side and black on the back, so that it can convert all heat radiation coming from the back into usable heat energy by absorbing it. In order to increase this effect, the outer Plexiglas tube 18 is provided with a half-shell-like, reflective surface 18 on the rear half.

Due to the very high effectiveness of the previously described absorbers 5 and 8, the metal nets 12, 13 can be dispensed with in this design.

Fig. 3 shows a solar collector 1 with the already mentioned outer P LexigLas tube 16, which takes the place of the cover housing 2. In this, an absorber housing 3 is installed diametrically in the middle, the structure of which corresponds to the principle according to Fig. 1 if the heat-insulating body 11 is omitted. This heat-insulating body 11 is replaced by the distance of the absorber housing 3 from the P LexigLas tube 16.

In this case, the space between the absorber housing and the outer Plexiglas tube 16 can be evacuated.

It proves to be particularly practical and cost-effective if all reflective surfaces 18, 10 are made of aluminum foil.

Fig. 7 and 8 show a particularly inexpensive design of a solar collector 1 in detail. According to Fig. 8 it can be seen that a section of suitable length of a commercially available Plexiglas double-web plate 19 , which can be purchased by the meter, is used as the absorber housing. The double-web plate or its webs 20 divide the double-web plate 19 into a plurality of elongated, flat, cuboid-shaped cavities 21 running parallel to one another. If the section of the double web plate 19 is treated at the ends in such a way that the middle webs 20 at the ends are removed and the front sides of the double web plate 19 are closed and the closed ends are provided with connecting pieces 22 for the passage of collector fluid 4, then a multiple absorber housing plate is present in a sense. Folded absorbers 5, flat absorbers 8, and if necessary also nets 12, 13, are now inserted into the cavities 21 from the front ends and held at a distance from the upper wall 24 and the lower wall 9 of the absorber housing or the double web plate 19 by means of heat-insulating spacers 23. Clear liquid or black pigmented liquid can be used as collector fluid. Against the back of the lower wall 9, an aluminum foil reflecting surface 10 is placed on the outside and behind it an insulating plastic layer 11, e.g.

a Styrofoam sheet, which is covered or glued on its back or outside with a plastic film 25 that provides weather protection and is also heat-insulating. A preferably elastic, heat-insulating edge strip 26 is placed all the way around the edge of the top of the absorber housing 3 or the double-wall sheet, and a section of another double-wall sheet 27 of the same size, closed at the end, is placed on top, the cavities of which can be evacuated if necessary. The plastic insulation plate 11, the double web plate 19 serving as the absorber housing 3, the further absorber plate 27 serving as the cover housing 2, including the spacer strip 26 and an additional similar spacer strip 28 placed on the top of the cover housing 2, are combined in a frame 29 which consists of inwardly open U-profiles, e.g. made of aluminum, and which is dimensioned such that it holds all of the above-mentioned components of the solar collector 1 together. In addition, sealing compound 30 against weather moisture can be applied to the ends of the U-legs.

In order to prevent heat loss from the absorber housing 3, i.e. the middle double-wall plate 19, to the metal frame 29, the left and right outermost webs 20 are not recessed like the middle ones, so that the outer cavity 20 on both sides of the double-wall plate 19 or the absorber housing 3 - as far as it lies in or under the frame 29 - is free of absorbers and collector fluid and thus - either filled with air or evacuated - serves as a heat insulation chamber 31 for heat insulation.

36

The solar collector 1 according to Fig. 7 can be very flat,
It is inexpensive and very light. Because of the
already described properties a high
degree of effect, can in special cases be referred to the
Cover housing 2 can be dispensed with. This measure is
This is advantageous when it comes to particularly low installation heights
in comes, ie if roof windows, hatches or similar are
lonnenkol Lektoren 1 should be replaced. The high
Effectiveness of the solar collector allows this
Keglassen of the cover housing in many cases.

Where cost-saving design is particularly important
the flat absorber 8 can also be omitted
because the reflecting surface 10 leads
radiated heat against the backs of the concave
curved surfaces 6 of the folded absorber 5 and
This keeps radiation losses to the rear within limits.
However, the omission of the flat
Absorber 8 a reduction in the heat transfer
surfaces so that the temperature gradient
twi see absorber temperature and collector fluid

temperature becomes slightly higher.

ts is due to the described designs of the .j firing-trained Sonne nkol Lektor 1

Bog I I, with relatively little financial '

Effort to build efficient solar panels, '

The effort is increased somewhat, but still ■ J

within the framework of economic amortization, so |

it is possible in climate zones for which a &Iacgr;

Solar collector 1 was previously unthinkable, in this way I

to generate heat energy. In addition, the innovation |

the possibility of using low weight and extremely <

small dimensions to convert solar energy into heat. ]

Il ' ■ I · · 4 -

ALL individual and combination features shown in the claims, the description and/or the drawings are considered essential to the invention.

The scope of protection of the innovation extends not only to the features of the individual claims, but also to their combination.

It goes without saying that the innovation is not intended to be limited to the exemplary embodiments shown and described. Rather, these only represent advantageous embodiments of the inventive concept.

Claims (1)

Dipl.-lng. P. HohMW>HMmtr. 21, T*L 02 «1 ·*«» KOBLENZ Protection claims: 1. Solar collector, with an absorber formed largely as a black body, which is housed in an elongated absorber housing, which is filled with longitudinally flowing Collector fluid is filled and is designed to be radiation-permeable with low losses at least on the sun side and with a cover housing provided at least on the sun side to insulate against heat conduction and radiation losses, characterized in that that the absorber (5) is a foil or sheet-like, solid body which is folded in an accordion-like manner parallel to the length of the absorber housing, wherein the folds have slightly concave flanks (6) facing each other on the sun side, that the absorber (5) is black on the sun side and the back, that an unfolded, flat absorber (8) runs across the rear tips of the folded absorber (5) and is black at least on the rear side, that a reflective or radiation-reflecting surface (10) is arranged on the back behind the folded absorber, and that a heat-insulating body (11) is provided behind the reflecting surface. Z. Solar collector in particular according to claim 1, characterized in that the concave curved surfaces (6) of the folded absorber (5) are black and shiny as "non-Lambertian" surfaces. 3. SonnenkoL Lektor according to claim 1 and/or 2, characterized in that that the sun-facing fold tips of the folded absorber (5) have a slightly wave-like profile across their length. (Pos.14) 4. Solar collector according to one or more of claims 1 to 3, characterized, that thin, or fine, black metal nets (12), folded at a more obtuse angle than the absorber, on both sides between the folds of the absorber (5) with pleat tips pointing to the back are used, and that a flat, black metal net (13) sunny side over the tips of the folds of the absorber (5). 5. Solar collector according to one or more of claims 1 to 4, characterized, that the collector liquid (4) with suspended, mixed with black dye. 6. Solar collector according to one or more of claims 1 to 5, characterized, that the cover housing (2) and the heat-insulating body (11) are designed as a common Plexiglas tube (16) with a circular cross-section, and that the absorber housing (3) is arranged centrally in the Plexiglas tube (16). 7. Solar collector according to claim 6, characterized in that the absorber housing (3) is designed as a cross-sectionally circular inner plexiglass tube (17), that the absorber housing (3, 17) is arranged concentrically in the outer P I e&khgr;ig I as pipe (16), and the fish absorber (B) covers the sun-facing side of the inner P Ie &khgr;ig I as pipe (17) on the inside like a half-shell, that its side facing the folded absorber (5) is mirrored, and that the outer PIe&khgr;ig I as tube (16) is mirrored on the inside, like a half-shell, on the half of the cross-section facing away from the sun. (Pos. 18) 8. Solar collector according to claim 6, characterized in that the absorber housing (3) is designed as a flat cuboid-shaped Plexiglas hollow body and is arranged diametrically in the outer P I e&khgr;ig las tube (16), that the lower wall (9) of the Plexiglas hollow body is mirrored on the inside, and that the folded absorber (5) is arranged with the upper fold tips at a distance from the upper wall (9) of the Plexiglas hollow body, and with the lower fold tips at a distance from the lower wall (9). 9. Solar collector according to one or more of claims 1 to 8, characterized, that the space between the absorber housing (3) and the outer P lexiglas tube (16) is empty of air. 10. Solar collector according to one or more of claims 1 to 5, characterized, a plurality of flat, cuboid-shaped absorber housings (3) running parallel to each other and communicating with each other at the ends in a Plexiglas double-wall sheet (19) are combined in one piece, that the folded and flat absorbers (5, 8) are inserted into the cavities (20) of the double web plate (19) at a distance from the lower and upper hand (9, 19) of the double web plate (19), that the reflective surface (10) is arranged on the outside of the lower wall (9) of the double web plate (19), That the heat-insulating body is designed as a plastic insulation plate (11), e.g. Styrofoam, and is arranged adjacent to the back of the reflective surface (10), that the double-web plate (19) and the plastic insulation plate (11) are enclosed and held together by a rectangular frame (29) consisting of inwardly open U-profiles, And that the frame (29) has on its two end faces, diagonally opposite each other, a connection piece (22) for the flowing collector fluid (4). 11. Solar collector according to claim 10, characterized in that in the frame (29) on the sun side at a distance from the double web plate (19) a further, upper double web plate (29) is accommodated as a cover housing (2). 12. Solar collector according to claim 10 and/or 11, characterized in that that the outside or back of the plastic insulation panel (11) is covered with a weatherproof and heat-insulating plastic film (25). 13. Solar collector according to one or more of claims 10 to 12, characterized, that the two outer cavities (20) of the double-web plate (19) designed as a multiple absorber housing (3) located under or partially in the U-profiles of the frame (29) are designed as heat-insulating chambers (31) that are sealed off from the flowing collector fluid (A) and are free of absorbers (5, 8). 14. Solar collector according to one or more of claims 1 to 13, characterized, that the reflecting surfaces (10) are designed as aluminium foils. 15. Solar collector according to one or more of claims 1 to 14, characterized, that the folded and the flat absorber (5, 8) consist of a maximum of 1 mm, preferably 0.1 to 0.3 mm thick metal sheet with a blackened, possibly black, shiny surface, whereby at least the folded absorber (5) is designed to be elastically springy in its shape. II t * B « ₉ 16. Solar collector according to one or more of claims 1 to 15, characterized, that the absorbers (5, 8) are made of copper. 17. Solar collector according to one or more of claims 1 to 16, characterized, that the absorbers (5, 8) are made of aluminium