WO2012093062A2

WO2012093062A2 - Thermal solar flat collector

Info

Publication number: WO2012093062A2
Application number: PCT/EP2011/074172
Authority: WO
Inventors: Heiko Hessenkemper
Original assignee: Tu Bergakademie Freiberg
Priority date: 2011-01-08
Filing date: 2011-12-28
Publication date: 2012-07-12
Also published as: DE102011008138A1; DE102011008138B4; WO2012093062A3

Abstract

The invention relates to a thermal solar flat collector, consisting of a heat transfer medium conduction system which is sealed in a water-proof manner at the edges and provided with an inlet and an outlet and which has at least two glass panes, which face the sun and are arranged spaced apart from each other, comprising a heat insulation layer facing away from the sun and a collector bottom, wherein the collector bottom forms the lower wall of the heat transfer medium conduction system and the innermost of the glass panes facing the sun forms the upper wall of the heat transfer medium conduction system, wherein the collector bottom is designed in the form of black glass and the heat insulation layer facing away from the sun is designed in the form of foam glass having closed porosity, having thermal expansion coefficients that are adapted to each other.

Description

Solar thermal flat collector

The invention relates to a solar thermal flat collector which finds application in thermal solar plants.

Flat plate collectors consist of the components absorber, transparent cover, housing and thermal insulation. At the same time, only little of the heat radiation from the absorber passes through the glass cover, which is achieved by double-glazing and optionally by a selective infrared-reflective coating of the cover glass can (greenhouse effect). The transparent cover prevents the removal of heat from the absorber by passing colder air (convection). Finally, together with the housing, it protects the absorber from the effects of the weather. Typical housing materials are aluminum and galvanized sheet steel, sometimes glass-reinforced plastic is also used.

The thermal insulation on the back of the absorber and on the side walls heat losses are reduced by heat conduction. The preferred insulating materials are polyurethane foam and mineral wool, in rare cases also mineral fiber insulating materials such as glass wool, rock wool, glass fiber or fiberglass. The core of a solar collector is the absorber, which usually consists of several narrow metal strips. The heat transfer medium is passed through a connected to the absorber strip heat transfer tube. In a plate absorber two plates are welded together, between which the heat transfer medium can flow. Typical absorber materials are copper and aluminum.

Flat plate collectors are characterized by a favorable price-performance ratio, as well as by a wide range of mounting options

(Http://www.solarserver.de/wissen/basiswissen/kollektoren.html).

DE 10 2008 007 799 A1 proposes the construction of a collector in which the collector liquid is in direct contact with the absorber plate and does not circulate through pipelines. Particularly advantageous is a collector is considered in which the collector liquid is above the bottom plate, which is self-absorbent or provided with an absorber layer. This bottom plate can be made of plastic or aluminum and must be protected by a common insulation against heat loss. In this collector valuable substances such as copper, in conventional collectors for the absorber plate and pipes) and titanium (as a basis for highly selective coatings) are saved.

DE 26 1 1 108 C2 claims a flat, designed in the manner of a multi-pane safety glass solar collector with a peripherally sealed watertight, provided with inlet and outlet heat transfer medium pipe system with at least two facing the sun, spaced glass panes, with a sun-facing heat insulation layer and a Collector floor, wherein the collector bottom, the bottom wall of the heat transfer medium duct system and the innermost of the sun-facing glass panes form the upper wall of the Wärmeträgermediumleitungssystems and is characterized in that the collector bottom is formed by a glass, which on its outer surface with a layer of black absorbent material is provided.

Known according to DE 25 27 742 A1 and collectors of the same type in which the bottom pan either made of black material or at least on its front, where it is in contact with the water, painted with a matte black color or provided with a matte black topcoat is. As black material for the formation of the tub and black plastic can be used. This However, this is a disadvantage in that then for the collector plate formed by the trough, a different material than for the previously arranged discs is to be used.

DE 10 2008 045 324 A1 relates to a flat collector for absorbing and transmitting electromagnetic energy from solar radiation to a fluid as heat transfer medium, in which a vacuum insulating glass unit is provided for insulating the absorber on the side facing the solar radiation and on the rear side. Between the vacuum insulation glass units there is an environmentally sealed cavity having a hydraulic structure through which a heat-adsorbing fluid flows through a fluid inlet and a fluid outlet opening and comprises a channel network in the form of a serpentine, a pad or a harp absorber. As a variant, it is provided in this publication, form a glass plate made of colored glass with a hydraulic structure as an absorber element. A disadvantage of this flat collector is that the very good efficiency is associated with increased manufacturing costs.

The object of the invention is to develop a solar collector, the production costs are at only a slightly lower degree of rotation compared to standard flat plate collectors at about one-third.

The object is achieved by a solar flat collector, consisting of a sealed with a watertight edge, provided with inlet and outlet heat transfer medium pipe system with at least two facing the sun, spaced glass panes, with a sun-facing heat insulation layer and a collector floor, said Collector bottom, the bottom wall of the heat transfer medium conduit system and the innermost of the sun facing glass panes form the upper wall of the heat transfer medium pipe system, and wherein inventively the collector bottom in the form of black glass and the sun remote from the heat insulation layer is in the form of foam glass with closed porosity. In this case, preferably, the insulation layer facing away from the sun in the form of black glass foam glass also forms the collector bottom in one structural unit. The collector according to the invention is most inexpensively made of foam glass. It can be easily machined from a single plate of about 10 cm thickness of the inner part. There is a 6 cm thick on the sides and bottom Insulating layer, wherein the geometric data can be varied according to insulation needs, weight and mechanical properties. Likewise, the quality of the glass foam material used results in variations in terms of density and pore size distribution. It makes sense to use dark glass. The two facing the sun, with a distance of about 1, 5 cm apart glass panes are preferably made of thermally tempered glass but can also be a photovoltaic module. These discs are glued to the glass foam. The adhesive must be waterproof for a long time and be able to withstand the temperature changes that occur. This gap serves as insulation, but it continues with hybrid modules in combination with PV modules. In this space, special gases can be introduced as in window panes when gluing in order to further reduce the convective heat transport. It is also possible to introduce infrared-reflecting layers on the underside of the cover plate, as in window construction. Appropriately, it is also z. For example, in the form of silica gel, apply moisture soaps to the edge areas to prevent dew formation between these two glasses in all weather conditions. Thus, a high long-term transmission can be ensured, in the actual absorber itself flow obstacles are worked out of the full foam glass, the surface also serves as a support and adhesive surface for the first cover glass. Here, geometries can be optimized depending on the collector size. The essence of the idea is that the whole collector of a foam glass block is easily and inexpensively mechanically herausarbeitbar, as a black body has optimal absorber properties, the foam glass at the same time optimal insulation, while the cover plates and the water inlet and drain with building-standard adhesives safely can be introduced. The insulation towards the irradiation side can, as described, optionally be made in different qualities as required. The collector impresses with a very low weight and with square meter prices of less than 50 € the price can be undercut the current normal collectors with significantly improved overall characteristics.

Since up to a third of the energy used in solar thermal energy is used for circulating pumps, it is necessary to minimize the flow resistances for the energetic pay-back time, especially for the porous glass surfaces. This is also necessary in series connections of modules. It may also be necessary to prevent the material from being externally crumbled. All of this can be achieved by sintering the glass surfaces and thus achieving smoothing, which is also an alternative for the molding process. For this purpose, in the production of foam glass in a closed mold with the required contours, at special temperature-time curves, the complete absorber with glazed overall surfaces can be formed, wherein thermal treatment of the surfaces for glazing could be necessary when hot. In this process, finely porous forms could be necessary.

The invention is illustrated by the figures 1 and 2. FIG. 1 shows the side view and the top view, and FIG. 2 shows the sectional view A-A and the detailed view F.

The invention will be explained in more detail in the following two embodiments: Example 1

The collector consists of a glass plate of mineral raw materials, which serves as an absorber, two glass panes as a cover and foam glass as a thermal insulation material. Possible compositions of the glass plate made of mineral raw materials and the foam glass are exemplified in Table 1 and given in DE 10 2009 022 575 A1.

Table 1: Composition and properties (expansion coefficient a, transformation temperature TG, density p, and liquidus temperature T _{Liq of} possible _{insert glasses}

Ma,% S1O2 ÄI2O3 CaO MgO Fe ₂ Q ₃ . Alkaa T _e p Tim

Glass at ³ ° C

1 46 21, 2 2 6 696 2,74 1232.

2 61 10 18 3 3 5 7.07 662 2.65 Ί 230

3 44 23 22 2 2? 7, 12 888 2.74 1 192

4 49 15 19 7 5 5 6,91 674 2,78 1236

5 45 10 18 9 6 6 7, 14 662 2.83 1257

6 46 19 15 3 10 7 7.22 655 2.82 12.20

₇ 53 15 17 8 2 5 7,19 677 2,72 1249 The heat transfer medium flows between the absorber plate and the lower cover. Fluid channels thereby create a structuring of the absorber plate during shaping in the rolling process. FIG. 3

Example 2 The absorber plate used in Example 1 is saved and the foam glass itself serves not only for thermal insulation but also as an absorber. The flood channels are milled directly into the easily processed foam glass. (Figure 4)

Claims

claims

1 . A solar thermal flat collector, comprising a heat-carrying medium duct system with at least two facing the sun, spaced apart from each other with a watertight edge, with a facing away from the sun Wärmeisotationsschicht and a collector bottom, the collector bottom, the bottom wall of the Heat transfer medium piping system and the innermost of the sun facing glass panes form the upper wall of the heat transfer medium piping system, characterized in that the collector bottom in the form of black glass and the solar heat insulating layer facing away from the sun in the form of foam glass with closed porosity with matched thermal expansion coefficients is formed.

2. A solar thermal flat collector according to claim 1, characterized in that the insulating layer facing away from the sun in the form of black glass foam glass in one unit at the same time forms the collector bottom.

3. A solar thermal flat collector according to claim 1 and 2, characterized in that the insulating layer facing away from the sun in the form of foam glass made of black glass with sintered surface in a structural unit forms the collector bottom.