GB2054829A - A focussing solar collector - Google Patents

Abstract

A focussing solar collector is adapted to focus solar radiation on a surface (12) mounted above a fixed support frame (11) by means of an optic system. The optic system comprises a plurality of flat, essentially rectangular, reflectors with reflecting specular surfaces (3). The reflectors are placed side by side and are identical with one another and the surfaces (3) lie in planes orientated at constant, predetermined angles with respect to each other. The reflectors can be rotated about their longitudinal axes to follow the apparent motion of the sun and to reflect the radiation thereof onto the surface (12) provided for this purpose, the said predetermined angles between the surfaces (3) remaining constant to enable this to be accomplished. <IMAGE>

Description

SPECIFICATION A focussing solar collector The present invention relates to a focussing solar collector for the interception and the focussing of solar energy onto a surface since, under normal reception conditions, solar radiation is of an insufficient intensity for most technological and practical uses.

Conventional solar collectors are of two types, namely non focussing collectors (with a flat receiving surface), and focussing collectors (with a parabolic reflecting surface).

The collectors of the first type, known as solar panels, are designed around the principle that a black surface exposed to the sun absorbs solar radiation and transforms it into heat in the collector this heat is then transmitted to a heat exchanging fluid contained within the panel itself.

The collectors of the second type, known as focussing collectors and to which the invention relates, are, in accordance with the known art, constituted by a mirror with a parabolic surface that is able to focus solar radiation falling thereon to form a single straight line or a point on a pipe containing fluid to be heated.

With focussing collectors, it is possible to attain high temperatures and, therefore, great efficiency.

However, the use of the said aforesaid known solar collectors presents the following serious problems: (1)With particular regard to the solar panels of the non-focussing type, these have a low standard of performance, especially during the winter months since the fact that the solar radiation is not focussed means that high temperatures cannot be reached.

(2) Solar focussing collectors as a result of being constituted by a parabolic mirror that must be large, cause, first and foremost, the manufacturing and installation costs of the collector to be high. Secondly, they require a complex mechanical structure in order that they may be set up in such a way as to resist the force of the wind and inclement weather. Thirdly, they require driving mechanism which is complex since the axis of the parabolic mirror has to be constantly kept pointing towards the sun.

Fourthly, installation problems arise when they are to be installed on buildings and they are not only difficult to maintain but they are also aesthetically unpleasing.

The object of the present invention is to overcome the aforementioned difficulties, particularly in respect of those mentioned for the solar focussing collectors.

The problem, that is at the root of the invention, relates to overcoming the disadvantages to which prior reference has been made and to allowing the creation to be achieved of a solar collector that is flat in the same way as a solar panel and fixed, yet is of the focussing type. The invention is based on the conceptual idea that it is not necessary to focus solar radiation to form one thin line, as is the case with collectors that have a parabolic reflecting surface, since the pipes that carry the fluid to be heated are of a limited area and, therefore, that it is sufficient to concentrate incident radiation over the whole profile (particularly the longitudinal section of symmetry of the said pipe).

According to the present invention there is provided a focussing solar collector comprising a support frame on which is mounted a plurality of flat substantially rectangular rotary reflectors each with a reflecting surface adapted to focus solar radiation on to an adjacent surface, the reflectors being substantially identical with one another and arranged side-by-side with their longitudinal axes parallel and coplanar in a row and the reflecting surfaces being orientated at predetermined angles with respect to one another so that when the reflectors are rotated about their longitudinal axes the said predetermined angles remain constant.

The main advantages the use of the solar collector according to the invention has to offer, is that it offers a focussing solar collector (and thus one with a high performance) that is essentially flat. Thanks to this the manufacturing, installation and maintenance costs are low. Furthermore, a solar collector of this nature can be installed directly on roofs of buildings or elsewhere.

Additionally, the fact that the support frame is fixed gives rise to a simple structure devoid of the requirement for a complicated movement mechanism and, therefore, avoids the complete solar collector having to be rotated.

A further advantage comes from the fact that the optic system, constituted by a plurality of specular surfaces placed side by side, offers less resistance to the force of the wind and thus does not call for complex anchorage or wind resistant structures.

The present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a sectional view, of a solar collector according to the present invention along the line I-I in Fig. 2 which is perpendicular to the longitudinal axes of rotation of specular surfaces of the collector; and Fig. 2 is a plan view of the solar collector.

With reference to Figs. 1 and 2, the solar collector comprises a fixed rectangular support frame 1, the lower part of which is provided with a supporting cross member 2. A plurality of rectangular, specular reflectors with reflecting surfaces 3. The reflectors are placed side by side, each identical with the other, and are fixed to the support frame 1 at one end and to the cross member 2 at their other ends by means of a corresponding plurality of pairs of rotating supports 4.

The flat, specular surfaces 3, each lying in planes orientated at predetermined angles a to each other, are free to rotate around their longitudinal axes A, that are coplanar one with the other, and along which each pair of the said rotating supports 4 is disposed. The rotation around its longitudinal axis A of each of the flat, specular surfaces 3 is determined by a rotation device 5 in the form of a drive rod which is connected to the said rotating supports 4 via gears 6. The rod 5 is powered by an electric motor 7 coupled to it through the medium of a gearbox 8 which controlled by an electronic device that is able to establish the angle of solar radiation R incident on the specular surfaces 3.

With reference to Fig. 1 , there is provided an arm 9 for supporting an essentially cylindrical casing 10, which is made of a transparent material and in which is coaxiaily inserted a pipe 11 of rectangular section. The pipe 11 has an externally blackened focussing surface 12 and is placed opposite the specular surfaces 3. In addition, the pipe 11 is of a shape and size corresponding to each of the said specular surfaces 3. In an alternative embodiment the surface can be covered by photoelectric cells to generate an electrical current when struck by radiation reflected from the surfaces 3 St denotes a first straight line which lies lying in the plane occupied by one of the specular surfaces 3 and which is perpendicular to the axis of rotation A of the said specular surface 3.The line S, forms with a second straight line S2, which is perpendicular to each of the axes of rotation A and lying in the plane to which the axes of rotation A belong, a predetermined angle b which is arranged to be such that the surface 3 can reflect the solar radiation R incident thereon onto the focussing surface 12.

The specular surfaces 3 lies in planes which are orientated at the constant angles a to each other which angles a are different as each specular surfaces 3 are located at a different distance and angle from the surface 12.

As the angle of incidence of the solar radiation R alters, the variations in the angles b are, in fact, identical for all the specular surfaces 3.

Thus once the angles b of the individual specular surfaces 3 have been regulated, in order -to focus the solar radiation R on the surface 12 all that is needed is one single control mechanism which is the rotation device 5 driven by the electric motor 7.

When it is not wished to use the collector, a rotation of the specular surfaces 3 at an angle away from the surface 12 is all that is necessary.

Claims (6)

1. A focussing solar collector comprising a support frame on which is mounted a plurality of flat substantially rectangular rotary reflectors each with a reflecting surface adapted to focus solar radiation on to an adjacent surface, the reflectors being substantially identical with one another and arranged side-by-side with their longitudinal axes parallel and coplanar in a row and the reflecting surfaces being orientated at predetermined angles with respect to one another so that when the reflectors are rotated about their longitudinal axes the said predetermined angles remain constant.

2. A solar collector as claimed in claim 1, in which a rotation device is provided for the reflectors, which device is adapted to bring about an identical angular variation for each of the reflecting surfaces in order to enable solar radiation to focussed said adjacent surface.

3. A solar collector as claimed in claim 1 or 2, in which said adjacent surface comprises an elongate rectilinear member attached to the support frame with a flat working surface opposite to the reflectors.

4. A solar collector as claimed in claim 3, in which the working surface covered by photoelectric cells able to produce an electric current.

5. A solar collector as claimed in claim 3, in which the working surface is constituted by a black surface able to absorb the said reflected radiation for the production of heat.

6. A focussing solar collector substantially as hereinbefore described with reference to the accompanying drawing.