WO2011063810A2

WO2011063810A2 - Improvement of a solar collector panel

Info

Publication number: WO2011063810A2
Application number: PCT/DK2010/000155
Authority: WO
Inventors: Hans Jørgen CHRISTENSEN
Original assignee: Christensen Hans Joergen
Priority date: 2009-11-24
Filing date: 2010-11-24
Publication date: 2011-06-03
Also published as: WO2011063810A3; EP2504635A2; DK200901238A; DK177472B1

Abstract

The invention relates to a solar collector panel (2) configured for collecting thermal energy by heating of air, said solar collector comprising an axial fan (1), which fan (1) comprises an electrically driven impeller (3), wherein the fan (1) during operation is arranged to transport air heated within a volume (12) of the collector panel (2), away from the collector panel (2), through an air outlet (9) extending to the exterior of the solar collector panel (2), and wherein said fan (1) comprises one or more flow straightening members (6) arranged at the suction side (7) of the fan (1) acting on the flow of air through the fan (1) during operation of the fan (1).

Description

IMPROVEMENT OF A SOLAR COLLECTOR PANEL

The invention relates to a solar collector panel comprising an axial fan, an axial fan and use of an axial fan in a solar collector panel.

Background of the invention

In the resent year solar collector panels have been improved to increase the efficiency of heat energy gathered from solar energy, and to decrease the size of such solar collector panels. Such heat energy may e.g. be gathered to heat up air so that the air heated by the collector panels can be supplied to one or more rooms of a building by means of a fan. WO 03/048655 discloses an example of such a solar collector panel. For aesthetic reasons, it would be advantageous that the thickness of the solar collector panel is small. However, the pressure drop within the solar collector panel increases with decreasing thickness due to increased air velocities, thus requiring a larger fan and a higher consumption of power by the fan. It is an object of the present invention to provide solar collector panels where these drawbacks and possibly other drawbacks by decreasing the thickness of the solar collector panel are counteracted.

The invention

The present invention relates to a solar collector panel configured for collecting thermal energy by heating of air, said solar collector comprising an axial fan, which fan comprises an electrically driven impeller, wherein the fan during operation is arranged to transport air heated within a volume of the collector panel, away from the collector panel, through an air outlet extending to the exterior of the solar collector panel, and wherein said fan comprises one or more flow straightening members arranged at the suction side of the fan acting on the flow of air through the fan during operation of the fan. When an axial fan impeller is operating, it develops a pressure resulting in the generation of an axial flow of air through the fan and possibly an increase in static pressure over the fan. Furthermore, the impeller also causes a rotation or swirl of the air flow after it has passed the fan, i.e. at the pressure side of the fan, as well as a rotation of the air in front of the impeller. This swirl requires an amount of power to be generated and is of no advantage to the operation of the fan. The use of flow straighteners downstream of the fan are known in the art for stopping the swirl and thus increasing the pressure generation of the fan.

However, the use of downstream flow straighteners will require that an air outlet tube extends a substantial distance from solar collector panel, and an alternative solution is sought for.

Furthermore, in the present use of a fan in a solar collector panel, the impeller will preferably be situated close to the internal volume of the panel and the impeller would without the presence of the flow straightening members induce a rotation in the air inside the volume, causing a disadvantageous mixing of warmer and colder air inside the volume. Due to the introduction of the flow straightening members, the mixing inside the volume is efficiently prevented and the swirl of the flow in front of the impeller and consequently also after the impeller will be reduced and the power fed to the fan is to a higher extend utilised to drive the axial flow through the impeller. The overall consequences of the introduction of the flow straightening members are thus that the mixing inside the volume is prevented and that the flow rate of heated air out from the solar collector panel by equal power consumption is increased, i.e. that the pressure developed by the fan is increased. Hereby, the heated air can be transported over a longer distance without having to increase the rated power of the motor of the fan.

According to a preferred embodiment, said one or more flow straightening members comprises one or more flat members extending substantially perpendicular to the rotor plane of the impeller of the fan.

Hereby simple, inexpensive and at the same time efficient flow straightening members are achieved.

It is furthermore advantageous that said one or more flow straightening members extends at least partly into said volume of said collector panel.

This is advantageous in that the fan can minimize the consumption of space in depth of the collector panel whereby the collector panel may be constructed with a smaller thickness.

It is preferable that the fan comprises at least two flow straightening members arranged substantially parallel to each other.

Two parallel arranged flow straightening members arranged at the suction side of the fan has proven in our tests to increase the pressure developed by the fan significantly, without increasing the rated power of the fan.

However, in other embodiments of the invention, the fan may comprise one, three, four or even more flow straightening members. Furthermore, the flow straightening members may in other aspects of the invention be arranged in an angle to each other, e.g. to form a cross or the like.

The one or more flow straightening members have preferably an extent in the direction away from the rotor plane of the impeller of within the range of 0.08 to 0.5 times the impeller diameter, preferably within the range of 0.16 to 0.32 times the impeller diameter. Alternatively, the extend of the flow straightening members is defined as being within the range of 1 to 6 centimetres away from the rotor plane of the impeller, preferably within the range of 2 to 4 centimetres.

The distance between the one or more flow straightening members and the impeller is preferably less that 10 millimetres, more preferred less than 5 millimetres. In an example according to the invention shown below is the distance as low as 1 millimetre.

According to a preferred embodiment, the distance between the front of the impeller on the suction side of the fan and the internal volume of the solar collector panel is less than 20 millimetres, preferably less that 10 millimetres, and most preferred less than 5 millimetres. In an example according to the invention shown below is the distance as low as 1 millimetre. Hereby, the fan takes up very little space in the depth of the solar collector panel for which reason it may be designed with a smaller thickness.

It is advantageous that the collector panel comprises a solar cell arranged to supply electrical power to an electric motor of the fan for driving said impeller.

Preferably, the solar cell is arranged inside the mentioned volume of the collector panel, but in other aspects of the invention, the solar cell may be arranged away from the collector panel. The solar cell makes the collector panel self sufficient with power thereby facilitating advantageous and easy installation at locations remote to fixed electric power installations for driving the impeller. It is furthermore advantageous that the relationship between the rated power of the fan and the surface area of heat absorber means of the collector panel for heating of air inside the volume is within the range of 1 to 8 W per m² surface area, preferably within the range of 2 to 5 W per m². .

Thereby an advantageous self sufficient collector panel which has low energy consumption and comprises a cost efficient fan and an advantageous and cost efficient solar cell can be achieved.

The rated power of the motor of the fan is in most cases less than 10 W, preferably less than 8W.

According to a preferred embodiment, the thickness of said solar collector is less than 8 cm, preferably less than 6 cm. In a specific example of a collector panel according to the invention, the thickness of the collector panel is about 5.5 cm, which is made possible by application of the present invention which counteracts the increase in pressure loss caused by the narrower space, i.e. the internal volume, where the air is forced flow by means of the fan. A significant part of this reduction in thickness from to almost half the thickness of known collector panels is made possible by introducing the flow straightening members.

The invention furthermore relates to the use of an axial fan in a solar collector panel configured for collecting thermal energy by heating of air, wherein said fan comprises one or more flow straightening members at the suction side of the fan acting on the flow of air through the fan during operation of the fan.

Likewise, the invention relates to a an axial fan comprising an electric motor configured for driving an electrically driven impeller, wherein said fan comprises one or more flow straightening members acting on the flow of air through the fan during operation of the fan , and wherein the one or more flow straightening members are arranged at the suction side of the fan.

Figures

The invention will be described in the following with reference to the figures in which: fig. 1 illustrates a schematic example of a solar collector panel according to the invention, fig. 2 illustrates an example of the fan of the solar collector panel according to the invention, seen in perspective, and fig. 3 illustrates a schematic example of the fan of the solar collector panel according to the invention.

Detailed description

Fig. 1 illustrates a solar collector panel 2 according to the invention. The solar collector panel 2 may also for the purpose of this invention be referred to as collector panel 2.

The collector panel 2 comprises a transparent or translucent front panel 10 and heat absorber means 1 1 extending between and spaced from the front panel 3 so as to form a volume 12 between the front panel 10 and the heat absorber means 1 1. The heat absorber means 1 1 are preferably permeable to air to act as an air inlet as illustrated. The heat absorber means 1 1 are e.g. made from a heat absorber panel comprising a screen of black felt, and a back panel made from a similar perforated aluminium sheet (not illustrated) that is left with a blank side facing the heat absorber means 1 1. In an alternative embodiment, the heat absorber panel is made from a perforated aluminium sheet of e.g. 0.7 millimetres of thickness, which is painted black or anodised on both sides. The heat absorber panel and the back panel are arranged in parallel with a mutual distance so as to provide a thermal insulation of the heat absorber panel as long as the fan 1 drives a flow from the back side of the back panel through the space between the back panel and the heat absorber panel and out through the heat absorber panel and into the volume 12.

As illustrated in fig. 1, the solar collector panel 2 furthermore comprises a fan 1 which during operation generates a flow of air. This flow facilitates that air enters the volume 12 from the air inlet (in this case the air permable heat absorber means 1 1), and is heated by the heat absorber means 1 1, is transported away from the volume 12 of the collector panel 2 through an air outlet 9 of the collector panel 2 to a destination location. The fan 1 is an axial fan 1 and comprises an electric motor 4 for driving the impeller 3 of the fan 1 so that the fan 1 can create a flow of air from the volume 12 of the collector panel 1, through the air outlet 9. The fan 1 comprises an electric motor 4 which is supplied with electric power by means of one or more solar cells 5 preferably arranged inside the volume 12 to collect energy from the sun, thereby facilitating a collector panel 2 which is self sufficient with electric power. The impeller diameter of the fan 1 is in the present example 125 millimetres.

An embodiment of such a solar collector panel may be found in international patent application No. WO 03/048655 to the same inventor. The rated power of the electric motor of the fan is about 7 W for a 3 m² collector panel 2. The power consumption of the fan 1 may be dimensioned by a W/m relationship between the rated power of the motor 4 and the area of the heat absorber means 1 1. Likewise the fan 1 may be dimensioned by means of a m³/h relationship. Hereby, the capacity of movement of air per hour for the fan is selected dependent of the area of the heat absorber means 1 1 and/or the volume in m³ of the volume 12. An example of a W/m² of the present example may be 2-5 W/m² such as 4 W/m².

According to the invention, the fan 1 comprises one or more flow straightening members 6 which during operation of the solar collector panel 2 straightens the flow of air created by the fan 1 , and which are arranged at the suction side 7 of the fan 1.

The flow straightening members 6 comprise two flat members made from thin sheet of aluminium and are arranged so they extend into the volume 12 of the collector panel 2 and in the longitudinal direction substantially parallel to the longitudinal direction of the rectangular solar collector panel 2 and so that the height h of the flat members 6 extends substantially perpendicular to the rotor plane of the impeller 3 of the fan 1. Thereby, the heated air from the volume 12 that will flow in a direction parallel to the longitudinal extent of the collector panel 2 can enter the suction side 7 of the fan 1 parallel to the rotor plane of the impeller 3, as well as parallel to flow straightening members 6 substantially without being hindered by the members 6. This is possible due to that the heated air can enter the suction side 7 of the fan 1 from the ends 16 of the flow straightening members 6 which forms a spacing 18 (not illustrated in fig. 1) between the flow straightening members 6.

The distance between the impeller 3 and the flow straightening members 6 is about 1 mm. The thickness TH of the collector panel from the front side of the front panel 10 to the back side of the heat absorber means 1 1 is in the present example about 5.5 cm.

In alternative embodiments of the invention, the air inlet is arranged at the bottom part of the collector panel 2 and the back side of the heat absorber means 1 1 is insulated so as to prevent loss of heat. Other alternative arrangements of the solar collector panel may also be envisaged within the scope of the present invention.

Fig. 2 illustrates the fan 1 seen in perspective comprising two flow straightening members 6 arranged parallel to each other at the suction side 7 of the fan 1. The fan 1 comprises a connection part 15 such as a flange connection as illustrated, for connecting the fan 1 to the collector panel 2. Furthermore, the fan 1 comprises a ventilation connection part 17 for connecting the fan 1 to a ventilation system, e.g. a pipe, thereby enabling the fan 1 to transport heated air into a ventilation system to a destination location in a building. The ventilation system may be connected to the ventilation connection part 17 inside the ventilation connection part 17, or at the outer surface of the ventilation connection part 17, if the ventilation connection part 17 extends through the heat absorber means 1 1 (not illustrated in fig. 2). The connecting of the ventilation system and the ventilation connection part 17 may e.g. be performed by means of a hose clip, glue, by means of a friction inducing connection or the like.

Fig. 3 illustrates the fan 1 seen from the side, at the ends 16 of the flow straightening members 6. The height h of the flow straightening members 6 is 3 cm in the present embodiment of the invention.

During operation of the solar collector panel 2, the infrared rays from the sun pass the front panel 10 and are absorbed by the heat absorber means 1 1. The sun light also causes the solar cells 5 to produce electrical power that drives the electric motor 4 of the fan 1 and thereby the impeller 3, which rotates and drives an airflow in through the back panel, through the heat absorber means 1 1 and into the internal volume 12 of the collector panel. The airflow is heated by the passage of the heat absorber means 1 1 as well as when the air flows parallel to the heat absorber means towards the fan 1. The fan 1 drives the heated air from the volume 12 and out through the back panel and further into a space to be heated and ventilated. A fan impeller 3 causes apart from the air flow also a rotation of the air flow after it has passed the fan 1, i.e. at the pressure side 8 of the fan 1 , as well as a rotation of the air in front of the impeller 3. This rotation or swirl requires an amount of power to be generated and is of no advantage to the operation of the fan or the solar collector. In the present use of a fan 1 in a solar collector panel 2, the impeller 3 is situated at a distance of about 1 mm from the internal volume 12 of the panel 2 and the impeller 2 would without the presence of the flow straightening members 6 induce a rotation in the air inside the volume 12, causing an disadvantageous mixing of warmer and colder air inside the volume 12. Due to the introduction of the flow straightening members 6, the mixing inside the volume 12 is efficiently prevented and the swirl of the flow in front of the impeller 3 and consequently also after the impeller 3 will be reduced and the power fed to the fan 1 from the solar cells 5 is to a higher extend utilised to drive the axial flow through the impeller 3. The overall consequences of the introduction of the flow straightening members 6 are thus that the mixing inside the volume 12 is prevented and that the flow rate of heated air out from the solar collector panel 2 is increased, i.e. that the pressure developed by the fan 1 is increased.

It will be understood that the invention is not limited to the particular examples described above but may be designed in a multitude of varieties within the scope of the invention, as specified in the claims.

List

1. : Fan of solar collector panel.

2. : Solar collector panel configured for collecting thermal energy by heating of air

3. : impeller of the fan

4. : Electric motor of the fan

5. : solar cell supplying the electric motor of the fan with electric power

6. : Flow straightening member(s) for straightening the flow of air from the fan 7. : Suction side of the fan

8. : Pressure side of the fan

9. : Air outlet of the collector panel for releasing air heated by the solar collector panel

10. : Transparent or translucent front panel of solar collector

1 1. : Air permeable heat absorber means of solar collector

12. : Volume between the front panel and the heat absorber means of the solar collector.

13. : Electric wire connecting solar cell with electric motor

14. : Bottom part of collector panel.

15. : Connection part such as a flange for connecting the fan to the collector panel

16. : Ends of flow straightening members

17. : Ventilation connection part.

18. : Volume/spacing between flow straightening members.

TH : Thickness of solar collector panel.

h : Height of the flow straightening members

Claims

1. A solar collector panel (2) configured for collecting thermal energy by heating of air, said solar collector comprising an axial fan (1), which fan (1) comprises an electrically driven impeller (3), wherein the fan (1) during operation is arranged to transport air heated within a volume (12) of the collector panel (2), away from the collector panel (2), through an air outlet (9) extending to the exterior of the solar collector panel (2), and wherein said fan (1 ) comprises one or more flow straightening members (6) arranged at the suction side (7) of the fan (1) acting on the flow of air through the fan (1) during operation of the fan (1).

2. A solar collector panel (2) according to claim 1, wherein said one or more flow straightening members (6) comprises one or more flat members extending substantially perpendicular to the rotor plane of the impeller (3) of the fan (1).

3. A solar collector panel (2) according to claim 1 or 2, wherein said one or more flow straightening members (6) extends at least partly into said volume (12) of said collector panel (2).

4. A solar collector panel (2) according to any of the preceding claims, wherein said fan (1) comprises at least two flow straightening members (6) arranged substantially parallel to each other.

5. A solar collector panel according to any of the preceding claims, wherein the extent away from the rotor plane of the impeller of the one or more flow

straightening members (6) is within the range of 0.08 to 0.5 times the impeller diameter, preferably within the range of 0.16 to 0.32 times the impeller diameter.

6. A solar collector panel according to any of the preceding claims, wherein the extent away from the rotor plane of the impeller of the one or more flow

straightening members (6) is within the range of 1 to 6 centimetres away from the rotor plane of the impeller, preferably within the range of 2 to 4 centimetres.

7. A solar collector panel according to any of the preceding claims, wherein the distance between the one or more flow straightening members (6) and the impeller

(3) is less than 10 millimetres, preferably less than 5 millimetres.

8. A solar collector panel according to any of the preceding claims, wherein the distance between the front of the impeller (3) on the suction side of the fan (1) and the volume (12) is less than 20 millimetres, preferably less that 10 millimetres, and most preferred less than 5 millimetres.

9. A solar collector panel (2) according to any of the preceding claims, and comprising a solar cell (5) arranged to supply electrical power to an electric motor

(4) of the fan (1) for driving said impeller (3).

10. A solar collector panel (2) according to claim 9, wherein the relationship between the rated power of the fan (1), and the surface area of heat absorber means (1 1) of the collector panel 2 for heating of air inside the volume (12), is within the range of 1 to

2 2

8 W per m surface area, preferably within the range of 2 to 5 W per m .

1 1. A solar collector panel (2) according to claim 9 or 10, wherein the rated power of the electric motor (4) of the fan (1) is less than 10W, preferably less than 8W.

12. A solar collector panel (2) according to any of the preceding claims, wherein the thickness (TH) of said collector panel (2) is less than 8 centimetres, preferably less than 6 centimetres.

13. Use of an axial fan (1) in a solar collector panel (2) configured for collecting thermal energy by heating of air, wherein said fan (1) comprises one or more flow straightening members (6) at the suction side (7) of the fan (1) acting on the flow of air through the fan (1) during operation of the fan (1).

14. An axial fan (1) comprising an electric motor (4) configured for driving an electrically driven impeller (3), wherein said fan (1) comprises one or more flow straightening members (6) acting on the flow of air through the fan ( 1 ) during operation of the fan ( 1 ), and wherein the one or more flow straightening members (6) are arranged at the suction side (7) of the fan (l).