Direct accumulation tank for heating water with solar energy

A direct accumulation tank, defining a closed volume (2), comprising an inlet (3) for filling the tank with a fluid, and an outlet (4) for emptying the tank of the fluid, and exhibiting an upper surface (Ia) exposed to solar rays. The upper surface (Ia) exhibits a plurality of reliefs (5, . . . 5n) for defining a greater surface extension exposed to the solar rays.

TECHNICAL FIELD

The invention relates to a direct accumulation tank for heating water using solar energy.

The device is applicable in the field of renewable energy sources, and in particular in the sector of production of hot water by exploitation of solar energy.

BACKGROUND ART

The prior art comprises direct accumulation systems and circulation systems, the latter being further sub-dividable into natural circulation systems and forced circulation systems.

While the latter systems are structurally more complex, more expensive and require a laborious and costly installation involving masonry work, direct accumulation tanks are more economical and easy to install, being substantially defined by a tank which functions as a heat absorbing element. Accumulation tanks exhibit an inlet and an outlet for the water which are is connected to a small-volume and flat or squeezed-configuration tank (in order to increase the surface-volume ratio) superiorly provided with a glass or plastic covering.

These devices, which require locating in a position which is directly exposed to the sun's rays, have a mean performance which is considerably below that of circulation systems.

Their use is preferred in occasionally-used dwellings, such as for example holiday homes, camp sites and mountain refuges, where consumption of hot water is of modest entity and where easy dismounting for winter storage is required.

The prior-art devices exhibit the drawback of lower overall performance than their competitors among the other systems.

The heating of the volume of water contained in the tank is, in reality, “layered”, where the upper layers are hot (i.e. the layers more directly in contact with the surface exposed to the solar rays) and where the lower layers are less hot, as they are further from the surface exposed to the solar rays.

It is also possible that a kind of short circuit can establish itself in the above-described accumulation tanks, i.e. a sort of by-pass, in which the incoming water tends to flow directly towards the outlet conduit without stopping internally of the tank to absorb the sun's heat.

A partial solution to the above problem can be applied by drastically reducing the height of the tank.

This design choice, however, penalises the capacity of the tank on the one hand, and on the other reduces the overall size of the surface thereof.

A further disadvantage is the considerable delicacy of the tanks.

To improve heat exchange between the surface exposed to the sun's rays and the volume of water contained in the tank, it is preferable to construct the surface to be exposed to the solar rays with a smaller thickness.

This design choice causes a smaller resistance to impacts which can occur both during transport of the tanks and during exposure thereof to climatic events such as, for example, rain or hail.

The aim of the present invention is to provide a tank with is easily installed and which has highly robust qualities.

A further aim of the present invention is to provide a tank which delivers a better performance than usual tanks present on the market, on a like-for-like basis.

A further aim of the present invention is to provide a tank which internally exhibits a small temperature gradient.

These aims and advantages and more besides are all attained by the invention as it is characterised in the appended claims.

With reference to the accompanying figures of the drawings,1denotes in its entirety a tank of the direct accumulation type.

The tank1includes a closed volume2containing a fluid, water, which is heatable by exposing an upper surface1athereof to solar rays.

The tank1is supplied by means of an inlet3and is emptied, or partially emptied, by means of an outlet4.

The inlet3and the outlet4are in reciprocal hydraulic communication via a plurality of conduits6, . . .6n, which delimits the closed volume2of the tank1.

The plurality of conduits6, . . .6n, is hydraulically located in series.

The plurality of conduits6, . . .6n, is defined by a first conduit6, connected to the inlet3via a first opening7, a final conduit6n, connected to the outlet4via a final opening7n, and a series of intermediate conduits6′ . . .6n-1, each contiguous and hydraulically connected to a preceding conduit and a successive conduit via a respective intermediate opening7′ . . .7n-1.

As can be seen in the accompanying figures, the first conduit6is the base conduit, connected to the inlet3, and the final conduit6nis the conduit located at the top of the tank1and connected to the outlet4, and the intermediate conduits6′ . . .6n-1, are interposed between the first conduit6and the final conduit6n.

In the specific example the initial conduit6is in hydraulic communication upstream with the inlet3, via the opening7, and downstream with a second conduit6′, belonging to the series of conduits6′ . . .6n-1, via the opening7′.

The second conduit6′, in turn, is in hydraulic communication, via an intermediate opening7″, with a third conduit6″ which is also part of the series of conduits6, . . .6n.

The final conduit6nis in hydraulic communication upstream with the penultimate conduit6n-1, the series of conduits6′, . . .6n-1, by means of the final opening7n-1 and downstream with the outlet4.

The series including the first opening7, final opening7n, and series of intermediate openings7, . . .7n, is arranged alternatedly with a separator wall8crossing the plurality of conduits6, . . .6n.

In this way the various openings facilitate, in collaboration with the separator wall8, a water circulation, from the inlet3to the outlet4, with a spiral progression in an alternated concentric direction as denoted inFIG. 2by the letter V.

In this way the water performs a forced passage, first in an anticlockwise direction on a first conduit6, then in a clockwise direction on a second conduit6′, in hydraulic communication with the preceding, and newly following the same alternated sequence up to reaching the final conduit6nlocated on the top of the tank1.

The geometric conformation of the plurality of conduits6, . . .6nis preferably symmetrical, each conduit being concentric to a contiguous conduit.

In the preferred embodiment, illustrated in the accompanying figures of the drawings, each conduit of the plurality6, . . .6nexhibits a circular is progression with a decreasing radius, starting from the first conduit6up to the final conduit6n.

In a further preferred conformation, each conduit belonging to the plurality6, . . .6nexhibits a polygonal progress, with a decreasing radius starting from the first conduit6up to the final conduit6n.

The upper surface1aof the tank1is defined by a plurality of reliefs5, . . .5nwhich enables obtaining a greater surface extension exposed to the solar rays with respect to the usual substantially planar surfaces of the traditional accumulation tanks.

The plurality of reliefs5, . . .5nis covered by a cover12, having a substantially truncoconical shape, of translucent plastic material defining, with the plurality of reliefs5, . . .5n, an air chamber which causes an effect known as the “greenhouse effect”.

The translucent cover12also has the objective of providing a mechanical defence of the tank, and further facilitates cleaning-away of encrustation, powder or other substances covering the exposed surface.

Each conduit6, . . .6ndefines the respective relief of the reliefs5, . . .5n, though the convex upper portion thereof.

For example, in a case in which the conduit has a curved transversal section, defined by an upper curved segment joined to a lower curved segment, each upper curved segment defines a relief of the plurality5, . . .5n.

Each polygonal edge or each closed curved edge (illustrated in the figures) has the above-cited function, i.e. the definition of reliefs constituting the upper surface1aof the tank1.

As can be seen inFIG. 3, each conduit belonging to the plurality6, . . .6nis raised with respect to a contiguous and external conduit.

More precisely, an upper curved segment belonging to a conduit, for example belonging to the conduit6′, is raised with respect to the upper curved segment of the corresponding contiguous and external conduit, which in the example is the first conduit6.

In this way, when the solar rays are not perpendicularly incident on the upper surface, the perpendicular incidence being a situation which occurs only in the first hours of the afternoon, there is all the same an optimisation of the surface struck by the rays.

Thanks to this design choice, in a case in which the solar rays strike the upper surface1awith an inclined direction, the top of the convex upper portion of a conduit does not place the base of the convex upper portion of a respective contiguous conduit and internal of the preceding conduit in the shade.

Each conduit of the plurality6, . . .6nsuperiorly exhibits, at each relief of the plurality of reliefs5, . . .5n, a corrugated progression, defined by a plurality of ribs10.

Each rib10belonging to the plurality of ribs10is arranged transversally of the development of each conduit, and preferably has a radial arrangement, in order to further facilitate a greater surface extension of a normal circular surface.

As can be seen in the figures of the drawings, the outlet4is arranged transversally of the inlet3.

While the inlet3is arranged almost tangentially of the first conduit6, the outlet4is perpendicularly incident to the tank1and in communication with the final conduit6n.

The outlet4is then, at the lower tract thereof, subdivided into a first chamber4aand a second chamber4b.

The first chamber4ais in hydraulic communication with the final conduit6nthrough a hole11communicating with the final opening7n.

The second chamber4bcrosses the final conduit6n, and consequently the tank1, in order possibly to be connected to a further source for direct supply of cold water.

The tank1can comprise, at the first tract6thereof, a safety valve18for safeguarding the integrity of the tank1from pressure peaks.

Further, the first tract6can be provided with a pair of handles9,9′ for facilitating the displacements of the tank1.

The structural and geometric conformation of the tank1exhibits various advantages.

Firstly, the sub-division of the closed volume2of the tank1into a plurality of conduits enables a smaller temperature gradient of the fluid contained in the tank1to be obtained.

Further, the conformation of the upper surface1a, exposed to the solar rays, enables an increase of the surface area struck.

The presence of ribs further improves the surface area struck by the sun's rays, apart from giving the tank further characteristics of sturdiness.

The raised positioning of each conduit further facilitates absorption of the solar rays during the range of the whole day.