Abstract:
A solar energy system comprising linearly focusing optical components and at least on receiver. The solar energy system comprises a device for assembling and disassembling the receiver, wherein the receiver ( 2 ) is slidably arranged on a longitudinal rail ( 4 ), which enables the receiver in its entirety, or in parts to be slid into and moved to a desired position in the solar energy system, or disassembled, respectively.

Description:
BACKGROUND ART 
       [0001]    A rapid development is currently occurring in the field of solar energy. The technological development encompasses a multitude of different areas within the field of solar energy, from simple flat thermal solar collectors for water heating in swimming pools to advanced solar cell systems that by concentrating the sunlight by a thousand times converts sunlight to electricity with an efficiency of over 30%. 
         [0002]    In concentrating solar energy systems sunlight is focused using different optical systems such as reflectors or lenses onto a receiver, in which the concentrated sunlight is converted into other forms of energy, for instance electricity or heat. 
         [0003]    One type of concentrating solar energy systems is parabolic troughs where the sunlight is concentrated into a longitudinal line. An example is the 84 m long and 6 m wide Euclides at ITER on Tenerife, that converts sunlight to electricity, and the “Parabolrinnen” by the German company Solar Millennium AG, that heats oil to 400° C. 
         [0004]    A concentrating solar energy system comprises a number of components, optical components for concentrating the light, components for continuously tracking the sun, receivers for receiving the concentrated solar radiation, and different kinds of ancillary equipment, such as turbines or hot water heaters. 
         [0005]    To date, the receivers have commonly been integrated with the reflector systems and may only be removed with great difficulty. US2008/0083405 discloses an example of such a solar energy system. In particular, for systems over a few metres the receiver has not been possible to remove in its entirety, except by disassembling the receiver into shorter units. The result is that the receiver is difficult to receive and that cleaning and service is complicated. 
         [0006]    Hence there is a need to provide an improved and flexible method of assembling receivers in solar energy systems in order to overcome the above problems. 
       DISCLOSURE OF INVENTION 
       [0007]    The purpose of this invention is to achieve an improved and flexible method of assembling receivers in solar energy systems. 
         [0008]    In the design according to the invention the receiver can by supplied and removed in a very simple way without requiring disassembly. This leads to a number of positive, surprising effects for the solar energy system:
       The receiver can easily be replaced when better technology is available. For receivers with solar cells the technology is expected to develop quickly towards an ever increasing efficiency.   Cleaning or service, which is usually lengthy because it is done with the receiver in place in the solar energy system, can instead be performed with the entire receiver removed and transferred to a suitable site.   The entire solar energy plant can be assembled in situ without a receiver. The receiver can then be assembled in a simple final step before commissioning. This is favourable as the time from start of construction to commissioning can be long and the receiver is both expensive and sensitive.       
 
         [0012]    The invention is intended for parabolic troughs but may also be implemented on other types of optics for concentrating solar energy systems. 
         [0013]    A parabolic trough is defined as a trough substantially shaped as a truncated two-dimensional paraboloid extended into a semi-cylindrical pipe. 
         [0014]    The invention relates to a solar energy system comprising optical components with a linear focal point and at least one receiver, wherein the solar energy system comprises a device assembling and disassembling the receiver. The receiver is arranged slidable along a longitudinal rail, which enables the receiver to be slid into and moved to a desired position in the solar energy system, or be disassembled respectively, in its entirety or in parts. 
         [0015]    One or more rails are arranged on the surface of the reflector or on a possible glass covering enclosing the reflector, along which the receiver can travel. This may be achieved by attaching the reflector to one or more slides with sliding surfaces or wheels that travel easily along the rail. 
         [0016]    This design allows the receiver to be assembled to a desired length remote from the trough and then be mounted in the trough by sliding it in from the short end of the parabolic trough. Conventionally, the receiver is mounted from the front, at right angles to the reflector, in short lengths using fixed attachments. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  shows a perspective view of a solar energy system in the form of a parabolic trough on legs in perspective; 
           [0018]      FIG. 2  shows a cross-section of a trough with a receiver, rail and slide; 
           [0019]      FIG. 3  shows a perspective view of the rail in  FIG. 2 ; 
           [0020]      FIG. 4  shows a perspective view of the slide in  FIG. 2 ; 
           [0021]      FIG. 5  shows a perspective view of a portion of the receiver in  FIG. 2 ; 
           [0022]      FIG. 6   a  shows the receiver partially assembled with the direction of assembly indicated with an arrow; 
           [0023]      FIG. 6   b  shows the receiver mounted in place in the trough. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    The present invention will now be described with reference to the attached drawing figures, which are intended for illustrative purposes only. 
         [0025]    A solar energy system of the parabolic trough type ( FIG. 1 ) has been equipped with this device in order to simplify the assembly of a receiver. The trough may be approximately one metre wide and five metres long. 
         [0026]    At the rear end of the trough there are two linear adjusting devices (not shown in the figure) which are used for rotating the trough towards the sun so that the receiver is positioned in focus. The front of the trough is in some embodiments covered by a transparent covering sheet ( 14 ) made from for instance glass or transparent plastic that enclosed the reflector in order to protect the reflector sheet or to increase the stiffness of the trough. 
         [0027]      FIG. 2  shows a cross-section through the trough with the receiver assembled. A rail or track ( 4 ) is arranged on the surface of the reflector, in which rail one or more slides ( 3 ) are arranged. A receiver ( 2 ) is arranged on the side/slides.  FIGS. 3-5  show a portion of the receiver, the slide and the rail. 
         [0028]      FIG. 2  shows a trough made from a reflective metal sheet ( 1 ). The metal sheet of the reflector can be a 1 mm steel sheet with a coating of, for instance, a silver film. The reflector metal sheet ( 1 ) focuses the light onto a receiver ( 2 ), also called an absorber, the surface of which is provided with solar cells ( 5 ). 
         [0029]    The receiver shown in  FIG. 2  has a triangular cross-section, which gives a good absorption of the rays of light reflected by the surface of the reflector towards the solar cells of the receiver. The receiver may also have other cross-sections which enable absorption of reflected rays of light from the surface of the reflector 
         [0030]    The receiver can also comprise two halves ( 7 ) having longitudinal slots ( 8 ) in which the slide ( 3 ) is mounted. Each half is also provided with through holes or channels ( 6 ) for coolant. If the receiver is given a triangular cross-section, then, suitably, so are the halves. The halves of the receiver can be manufactured by extrusion, which gives an effective manufacturing process. A suitable material is extruded aluminium, gives a high strength and low weight. An alternative to aluminium is a plastic material. 
         [0031]    An extended rail ( 4 ) is arranged at the bottom of the trough, which rail comprises a first section ( 9 ) intended to be attached to the trough, hereafter termed the attachment part, and a second section ( 10 ) on which the slide is slidable. The second section ( 10 ), hereafter termed the sliding means, can comprise one or more sliding elements ( 11 ), shaped as a device extending from the attachment part, the outer portion of which is shaped as a head ( 12 ). In  FIG. 2  a rail is shown having a sliding element on either side of the attachment part ( 9 ). 
         [0032]    The rail can be extruded, and is suitably made from aluminium, for high strength and low weight. Alternatively, the rail can be made from a plastic material. In order to facilitate transport and handling the rail can comprise a number of rail portions which are assembled end to end in the reflector trough. Each sliding element ( 10 ) may in this case be provided with a hole through its centre in the outer portion ( 12 ), in which hole a pin can be mounted in order to facilitate exact positioning of two sections during joining in their longitudinal direction. 
         [0033]    The slide ( 3 ) can comprise an extended continuous profile running along substantially the entire length of the receiver, or a number of discrete elements placed distributed along the length of the receiver. One end of the slide is provided with means ( 13 ) for attaching the receiver ( 2 ). These may comprise extending portions adapted to engage in slots ( 8 ) in the receiver, enabling a simple mounting of the slide onto the receiver. The cross-section of the slide can have a wing profile (see  FIG. 2 ) so that it is wider at the end that is closer to the rail ( 4 ) and the bottom of the trough in the assembled position, which gives a strong construction. The portion of the slide located between the receiver and the rail ( 4 ) is preferably hollow, giving a reduced weight. The slide can be manufactured from hydro-cut or extruded aluminium. 
         [0034]    At the end of the slide arranged to slide on the rail ( 4 ) there is provided at least one receiving means ( 13 ) shaped so that it can engage with the sliding elements of the rail ( 4 ). The receiving means ( 13 ) can be shaped so that its cross-section encircles the head ( 12 ) of the sliding element. Plastic inserts can be inserted in the receiving means to reduce friction between the receiving means and the sliding element. The slide can suitably be provided with at least two receiving means ( 13 ) for increased stability. In the embodiment shown in  FIG. 2  the slide comprises two receiving means ( 13 ) encircling the heads ( 12 ) of the sliding elements so that the receiving means and the sliding element are locked against relative motion in all directions except in the longitudinal direction of the rail (the sliding direction). 
         [0035]    Alternatively, the sliding element can be arranged on the slide and the receiving means on the rail. 
         [0036]    The rail and the associated slide can alternatively be arranged in different ways. For instance, the connection between the slide and the rail can be achieved by means of wheels, sliding bearings or roller bearings in different combinations. 
         [0037]    There are also other alternatives for the position of the rail in the trough. The rail may, for instance, be attached below a possible covering sheet ( 14 ); at the edges of the trough, or at the bottom of the trough or in combinations thereof. The rail may for instance be mounted both above the receiver attached to the covering sheet or below the receiver attached to the bottom of the trough. In this case the receiver is mounted between the rails which are connected by the slides. Connecting the covering sheet and the bottom of the trough in this way will increase the ability of the covering sheet to resist forces from outside. Assembling the rail at the bottom of the trough only will avoid the risk of the slide or the rail shading the reflector from incident sunlight. 
         [0038]    The rail can be mounted by, for instance, glue, tape, rivets, screws, bolts or be attached by placing the rail in slots or lugs arranged in the trough. If the rail is glued to the reflector metal sheet with reinforcing through bolts at the ends thereof, little damage is done to the metal sheet and assembly will be fast and simple. 
         [0039]    Alternatively, the rail can be an integrated part of some other function in the reflector trough, for instance a bent section in the reflector metal sheet, a longitudinal edge or a slit e.g. between the covering sheet and the reflector metal sheet. 
         [0040]    The receiver in the system shown in  FIG. 2  is intended for combined electricity and heat generation where solar cells ( 5 ) for concentrated light have been laminated onto the receiver. A coolant is pumped through channels ( 6 ) inside the receiver, which coolant cools the solar cells and extracts heat from the system that can be used for e.g. hot water. 
         [0041]    The receiver may have different embodiments and can be used for different types of energy conversion, such as generation of electricity only using solar cells (possibly cooled by air); only for extraction of heat using e.g. vacuum tubes or for chemical processes, such as hydrogen production using a receiver containing a catalyst. In all embodiments the receiver has a surface which can absorb light and convert it to one or more other forms of energy. 
         [0042]    Hence, it is possible to mount the received entirely outside the trough after which it is added to the system by sliding it onto the rail. Alternatively it may be assembled piece by piece outside the trough and successively be slid into the trough.  FIG. 6   a  and  6   b  shows how the receiver is mounted in the trough by displacing it onto the rail. 
         [0043]    When the receiver is to be removed it is pulled out in reverse order.