WO1999020954A1

WO1999020954A1 - Dome-shaped solar powered heat accumulator

Info

Publication number: WO1999020954A1
Application number: PCT/IT1998/000268
Authority: WO
Inventors: Franco Vecoli
Original assignee: Franco Vecoli
Priority date: 1997-10-17
Filing date: 1998-10-08
Publication date: 1999-04-29
Also published as: IT1295669B1; ITFI970228A1; AU9643598A

Abstract

A solar-powered thermal accumulator for producing hot water and supplying it to a water system, comprising a tank (3) for containing said water, the tank (3) comprising a substantially dome-shaped heat exchange surface. An external transparent dome (7) is provided above the heat exchange surface and delimits with it an hollow gap (9). A hydraulic circuit (4, 5, 8) is provided to put the tank (3) in communication with the water system. Preferably the heat exchange surface has a hemispherical shape and defines said tank (3) in co-operation with a diametrical base (3a) connected to a support basement (1) to be fixed to a surface exposed to solar rays.

Description

H-E E

DOME-SHAPED SOLAR POWERED HEAT ACCUMULATOR

DESCRIPTION

Field of the Invention The present invention relates to the field of solar- powered thermal plants, namely for the supply of family users, and more specifically it concerns a kind of solar powered heat accumulator.

Description of the Prior Art It has been rather widespread in the past, in particular for low-consume users, the employ of thermal accumulators with solar panels, for the supply of hot water for sanitary use and more rarely, due to the seasonality of the solar source and then to its unreliable availability, for room heating. The merits of this kind of solution are not negligible, namely for what concerns its safety and its involvement of no ecological damages .

The so-called panels are the main component, i.e. the thermally active one, of such a plant. They usually comprise a pipe coil in which the water to be heated is circulated, extending on the back of a plane face exposed to the solar radiation. Unfortunately, the efficiency of existing panels, i.e. the efficiency of the conversion from the solar radiation energy to the thermal energy of the circulating water, is on the average very low and this has strongly restrained the diffusion of this kind of solution.

As a matter of fact, said efficiency is remarkably variable as a function of the angle of incidence of the solar rays on the exposed face. It is obviously the highest when such angle is about 90° and, since the average angle of incidence of the solar rays on the earth surface varies with the seasons, when for example a panel is placed in a substantially horizontal position it has a good efficiency in the period of the year in which the sun is nearer to the zenith. On the contrary, the efficiency strongly decreases when the sun stays on average low with respect to the horizon. In this period a substantially vertical arrangement of the panel would be advantageous . Analogous remarks can be made even for what happens through a single day, in which the inclination of the solar rays is obviously greatly variable, in particular during summer days .

Summary of the Invention

It is an object of the present invention to provide a solar-powered thermal accumulator having a higher efficiency than that of known and presently used panel plants, being in particular able to overcome the above mentioned drawback relating to the variations of the angle of incidence of the solar rays .

This object has been achieved with the solar-powered thermal accumulator according to the present invention, for producing hot water and supplying it to a water system. The accumulator comprises a tank for the water and is characterised in that said tank comprises a substantially dome-shaped heat exchange surface and that an external transparent dome is provided delimiting a hollow gap about the heat exchange surface. A hydraulic circuit is provided to put the tank in communication with the water system. Preferably, the hollow gap is vacuum sealed.

According to a preferred embodiment of the invention, the heat exchange surface has a hemispherical shape, and defines the tank in co-operation with a diametrical base connected to a support basement to be fixed to a surface exposed to solar rays. The hydraulic circuit comprises pipes for the inflow and the outflow of the water to and from the tank, and the dome sealingly engages with the basement coaxially to the tank.

Brief description of the drawings Other features and advantages of the thermal accumulator according to the present invention will be apparent from the following description of one of its embodiments, to be intended only as an example and not a limitation, with reference to the attached drawings in which:

- figure 1 is a side view of the thermal accumulator according to the present invention;

- figure 2 is a top plan view of the accumulator of figure 1. Description of the preferred embodiment

With reference to the above figures, the thermal accumulator according to the invention comprises a basement 1, to be fixed to the roof, or in any case to an external face, of the building where are placed the users to be supplied, so that it can be suitably exposed to the solar rays . In the depicted embodiment basement 1 has a cylindrical shape and from it a number of bearing blocks 2, cylindrically shaped as well, extend. Blocks 2 are placed near the centre and along the perimetral edge of basement 1 and support a hemispherical tank 3 , leaned thereon with a diametral base 3a, preferably made of aluminium and having a diameter which is lower than that of basement 1.

Tank 3 is hydraulically connected to water inflow and outflow from and to the water system to be supplied, provided with conventional circulation pumps. These means comprise a water outflow pipe 4, placed within the tank so as to end in correspondence to its highest portion, and an inflow pipe 5 communicating with the tank in correspondence to base 3a.

A vent 6 is placed adjacent and parallel to outflow pipe 4. Vent 6 communicates with the tank to remove the air which accumulates thereinto, and is provided with a valve of a known type, not shown, preventing the inlet of water.

Both water outflow and inflow pipes 4, 5 and vent 6, coming from the respective joints with tank 3, enter basement 1 through its top side, getting out thereof radially through its side surface, grouped in an array 8.

A hemispherical dome 7, made of Plexiglas, PMMA or other transparent material, having a diameter greater than that of tank 3 , is placed on basement 1 coaxially to tank 3, defining a hollow gap between its inner face and the outer one of tank 3 itself. Dome 7 is fixed to basement 1 by means of a sealing connection, of a known kind and not shown in the figures, so that the air inside the gap can be sucked, creating a vacuum level which is compatible with the technical features and the functional needs of the structure. In this way a more efficient insulation of tank 3 can be achieved.

The accumulator according to the present invention operates in the same way as common panel plants. The water flowing into tank 3 is heated from the solar radiation and supplied to the users when they require it. A conventional floating device (not shown) or the like is provided to control the water level inside tank 3, possibly having a thermostatic control to prevent water wastes caused by the dilution of hot water with cold one coming from inflow pipe 5.

However, contrary to what happens with the panels, thanks to the hemispherical shape of tank 3 , whatever the inclination of the solar rays may be, they join the face to be heated with an angle of incidence of about 90°, this resulting in a always very high average efficiency of the accumulator. Besides, it will be appreciated how, contrary to common panel plants where an external water accumulator is provided, in this case the heat exchange surface and the accumulator are embodied in the same device, with important advantages in terms of compactness.

The outer face of tank 3 can be painted or anodised in a dark colour, e.g. black or more advantageously strong blue, in order to minimise the reflection of the solar rays. Furthermore, to reduce any possible heat loss, basement 1 can be coated by a layer made of an insulating material . An auxiliary electric system can be provided to feed in a known way, through blocks 2, conventional resistance water heating means placed inside tank 3, for the electrical operation of the accumulator at night or in cloudy days so as to have hot water always available. If required by the climate of the geographic area in which the accumulator is placed, two or more concentric Plexiglas domes 7 can be provided, optionally separated by vacuum gaps, so that a higher insulation level can be reached. In particular, if for temperate areas one dome 9 is enough, very cold areas may require the use of even three concentric domes .

To install the accumulator on leaning or differently structured roofs, the basement 1 can have various shapes, in order to fit the surface to which it has to be fixed. The foregoing clearly shows the advantages brought by the accumulator according to the invention. Namely, it offers a higher efficiency with respect to common panel plants, and besides with a simpler and very compact structure .

The thermal accumulator according to the invention will be made in a large number of sizes and consequent volumes, to be able to satisfy the specific needs of each user. Due to its particular compactness, choosing the suitable size, it can be advantageously installed also in campers, caravans, prefabricated mobile houses and the like. These and other variations and/or modifications that can be brought to the solar-powered thermal accumulator according to the invention fall within the scope of the invention itself as stated in the appended claims.

Claims

┬úLAIM┬ú

1. A solar-powered thermal accumulator for producing hot water and supplying it to a water system, comprising a tank (3) for containing said water, characterised in that said tank (3) comprises a substantially dome-shaped heat exchange surface and that an external transparent dome (7) is provided delimiting a hollow gap (9) about said heat exchange surface, a hydraulic circuit (4, 5, 8) being provided to put said tank (3) in communication with said water system.

2. The accumulator according to claim 1, wherein said heat exchange surface has a hemispherical shape, and defines said tank (3) in co-operation with a diametrical base (3a) connected to a support basement (1) to be fixed to a surface exposed to solar rays, said hydraulic circuit comprising pipes (4, 5) for the inflow and the outflow of the water to and from said tank (3) , said dome (7) sealingly engaging with said basement (1) coaxially to said tank (3) .

3. The accumulator according to claim 2, wherein said circuit comprises a vent (6) , communicating with said tank (3) to remove the air from its inside.

4. The accumulator according to claim 2, wherein said pipes are placed for a section within said basement (1) and get out of it sideways towards said water system.

5. The accumulator according to claim 2, wherein at least one further transparent dome is provided, having the same shape of said external transparent dome (7) to define at least one further hollow gap.

6 . The accumulator according to claim 1, wherein said heat exchange surface is painted or anodised in strong blue or black colour.

7. The accumulator according to claim 1, wherein electrically fed water heating means are placed within said tank (3) .

8. The accumulator according to the previous claims, wherein said hollow gap between the heat exchange surface and said transparent dome or between the two consecutive, concentric transparent domes is vacuum sealed.