Solar Trough Field System

Abstract

A solar trough field system according to the invention comprises multiple parabolic reflectors; a thermal receiver tube, center of which coincides with the focus of the parabolic reflectors and which consists of a metal heat receiving pipe (1) and a glass tube (2) which are nested (the glass tube surrounds the metal heat receiving pipe from outside); a ‘vacuum seal and glass tube connector system’ (E) which connects the glass tubes (2) and the thermal heat receiving pipe (1) to each other; a rotating support unit (21), which connects the parabolic panel to the glass tube connector system (E) and provides the thermal receiver tube (1) to stay stationary while the parabolic panel is rotating around it; ‘flexible expansion unit’ (29) located at the end of each parabolic trough unit which provides vacuum seal while the Heat Receiving Pipe (1) is moving due to heat expansion; and a vertical loop (52) located at the discharge side of the parabolic unit, which can be used instead of water separator and which also provides the heat expansion of the Heat Receiving Pipe (103).

Description

TECHNICAL FIELD

This invention relates to developments on parabolic trough-shaped collectors which concentrate the sunlight on an axis of focus, converting it into other energy forms such as heat and electricity.

PRIOR ART

Currently, trough collectors (solar trough field system) are used to collect the sun's energy in order to obtain electricity and heat there from. These systems comprise trough-shaped long parabolic reflectors, thermal receiver tubes which are placed on the focus of the reflectors where beams coming from the reflector are collected and in which a fluid exists, and a rotating mechanism which aligns the reflectors to the sun. The beams coming to the reflectors which are directed towards the sun are reflected and collected on the thermal receiver tube which is located on the focus of the reflector. Thermal receiver tube is provided with two nested tubes where a vacuum setting is located in the space there between. A fluid, which provides the heat transfer, is passed through the inner tube. The outer tube is made of glass. By concentrating the beams coming from the reflectors on the thermal receiver tube, this tube reaches very high temperatures; therefore, the fluid located in the inner tube can be heated. Heat energy can be converted into the electric energy, when desired, by means of this fluid which reaches high temperatures.

The existing Solar through Field type of Thermal Energy technologies have some design problems which cause thermodynamic efficiency losses and increase fabrication, installation, operation and maintenance costs. These design problems are:

By its nature, a reflective parabola must receive solar incidence at a perpendicular angle to it's aperture in order to be able to concentrate it to its focal point. Since the radius of the heat receiving pipe (around 8 cm) located at the focal point of the parabola is relatively small to the aperture of the Parabola itself (about 570 cm), even small shifts from this perpendicular position causes the quality of the concentration to drop and eventually miss the heat receiving pipe. Therefore, it is required that the “parabolic trough” accurately fallow the Sun all day long at a speed equal to the rotation of the Earth (0.004 Degree/Sec. or 0.25 Degree/Min.).

All of the current designs are based on placing the centre of rotation at the gravitational centre of the total weight of all of the rotating parts. This is done to reduce the amount of energy required for rotation.

However Since the “centre of rotation” and the “focal point” (B) of the Parabola are not superimposed in these systems, as shown in FIg. 1, the heat receiving pipe has to be rotated all day long to keep it at the focal point of the Parabola (B) which is continuously moving. This in turn requires that the end connection pipes that connect the moving heat receiving pipe to the stationary steam pipeline on the ground must be flexible.

The solar trough field systems which are built on California (USA) by LUZ can be given as an example for these systems. In that system of LUZ, the parabolic reflectors which are many meters long and the thermal receiver tubes which are located on their focus are rotated together. The most fundamental problem of this system is that the thermal receiver tubes which are made of a fragile material are movable. As long as the thermal receiver tubes are movable, they are subjected to more torque load and the flexible hoses are used in the connections of the beginning and ending points of the parabolic reflectors with the fixed tubes. The thermal receiver tubes which are subjected to the torque loads have a higher possibility of breaking. On the other hand, it is understood that the flexible hose connection is not a safe system since the temperature of the fluid which is transferred within the thermal receiver tube is 300-500° C. In addition, it has been obtained from the field observations that the truss structure, which supports the parabolic mirrors, is also weak against the torque and the moment loads acting due to the drive unit of the system and the wind. Because of these loads, the parabolic reflectors are frequently broken, thus causing the operating costs to increase.

Thus, after some trials they had to switch from “Direct Steam Generation” (DSG) to using oil as the “heat transfer fluid”. Even though hot oil does not have the dynamics of the steam, these hoses still burst occasionally, spilling oil all over the mirror lined parabolic troughs. Hot oil is than pumped to the central station where it is passed true heat exchangers to generate steam from water tanks. However this two stage operation results in thermodynamic losses up to 15%.

Due to the problems encountered in the above-mentioned system of LUZ, the EUROTROUGH project supported by the European Union is initiated. In the scope of this project, the lower part of the parabolic reflectors is supported by a truss structure which can resist more against the torque and the moment loads, and there are inflexible movable tubes attached to the rotary joints on the connection points of the movable thermal receiver tubes with the fixed tubes. Although the truss system which is developed with EUROTROUGH is safer than the system of LUZ, it could not completely eliminate the breaking problem of the thermal receiver tubes. It has been understood from the field observations that the possibility of breaking the thermal receiver tubes decreases only to some extent since they are movable in this system as well. In addition, it has been also revealed from the field observations that the hot fluid frequently leaks out from these connections of the thermal receiver tubes comprising rotary joint connection points.

Another design problem existing in current technologies can be seen from FIG. 2, which shows the connection between the glass tube (102) and the metal heat receiving pipe (103). In current technologies glass tube (102) is connected to the metal heat receiving pipe (103) from both ends by a metal expansion unit (101). These metal parts are connected to the glass tubes (102) by a special laser welding technique. Vacuum is formed in the annulus of the metal pipe (103) and the glass tube (102) during welding process. Then these units are welded together to form the full length of the Heat Receiving Element. However;

• • When the water reaches above 300° C. temperatures, some Hydrogen breaks out of water and passes through the steal pipe into the vacuum zone. Since there is atmospheric pressure outside, this Hydrogen remains in the vacuumed annulus and causes the vacuum to drop gradually. To prevent this, a special metal rod called “getter” is developed and placed inside the glass tube. However “getter” has a certain capacity to absorb Hydrogen. This is one of the important reasons why the current designs had to return back to using oil as heat transfer fluid instead of achieving the much desired Direct Steam Generation.
  • The metal expansion parts welded to glass has a very low heat resistance. Thus it gradually weakens the special connection to the glass tube.
  • This metal expansion piece inevitably conveys some of the vibration and torque created by the metal parts to the glass tubes, causing them to break.

A further design problem exists in high pressure separators (can be seen in FIG. 24). Since the Heat Receiving Assemblies (Metal pipe, Glass tubes etc.) are placed horizontally, depending on the water inlet flow rate (45), some part of the water (46) through the pipe can not become steam (47). Thus the discharge, especially from the first several units, contains hot water (46) as well as steam (47). This also prevents the steam (47) from being a dry steam which is necessary for steam turbines. To deal with this, the systems in the prior art use high pressure separators at the discharge of the first few parabolic trough units. Water separated by this separator is piped back to the inlet stream, recirculating it until it completely becomes steam. However this increases system inefficiency, as well as adds to the system cost.

The present invention provides a solar through field system which overcomes the above mentioned design problems with an increased efficiency and reduced fabrication, installation and maintenance costs.

SUMMARY OF THE INVENTION

In accordance with the present invention; which discloses the developments on the solar collectors with parabolic reflector, which rotate around a fixed thermal receiver tube; the solar through field system comprises;

A “vacuum seal and glass tube connector system” which allows the Heat Receiver pipe to expand and move freely within and independent of the glass tubes, provides a vacuum seal and provides support for the entire Heat Receiver Element;

A “flexible expansion unit” located at the end of each parabolic trough unit, providing the vacuum seal while the Heat Receiving Pipe is freely moving due to heat expansion

A vertical loop located at the discharge side of the parabolic trough unit, which can be used instead of separator at ground level and which simultaneously providing for the heat expansion of the Heat Receiving Pipe.

A wind breaker to surround the Solar Trough Field to deflect the wind above the parabolic troughs.

A half circular support and rotating structure which supports the parabolic reflectors and provides an efficient protection while at the same time allowing for simpler systems to track the Sun.

OBJECT OF THE INVENTION

The object of the present invention is to provide a solar through field system (with parabolic reflectors rotating around a fixed thermal receiver tube) having a “vacuum seal and glass tube connector system” which allows the heat receiver pipe to expand and move freely within and independent of the glass tubes and provides a vacuum seal and at the same time provides a support for the entire Heat Receiver Element.

Another object of the invention is to use a flexible expansion unit for providing vacuum seal after the last glass tube connector assembly at the discharge side of the parabolic trough, while the Heat Receiving Pipe is moving freely due to heat expansion.

Another object of the invention is to use a vertical loop between successive parabolic troughs (located at the discharge side of the parabolic trough units) to provide the heat expansion factor for the Heat Receiving Pipe and also to prevent the remained water (which has not evaporated) from passing to the next pipe and so it remains in the heat receiving pipe until it becomes steam.

Another object of the invention is to solve the wind load problem and to prevent the mirror breakage problem caused by the wind load, by using a wind breaker to surround the Solar Trough Field to deflect the wind above the parabolic troughs.

Yet another object of the invention is to decrease the maintenance and replacement expenses; which will arise in case of breaking the glass tubes; with the help of the “glass tube connector system”.

Another object of the invention is to use “glass tube connection system” to provide a continuous vacuum chamber for the full length of the parabolic through unit, allowing for the creation and repeated maintenance of the vacuum from a single valve located at either end of the parabolic trough unit, eliminating the need for the currently used “getter” sticks to absorb Hydrogen.

BRIEF DESCRIPTION OF FIGURES

The solar trough field system according to the present invention is shown in the attached drawings wherein:

FIG. 1 shows the solar trough field system designs in the prior art.

FIG. 2 shows the glass tube and metal heat receiving pipe connection in the prior art systems.

FIG. 3 shows the entire vacuum seal & glass tube connector system

FIG. 4 shows the front and side views of the ceramic unit

FIG. 5 shows the connection of two halves of the ceramic unit.

FIG. 6 shows the front and side views of the silicon unit

FIG. 7 shows the front and side views of the heat & UV protection of the silicon unit

FIG. 8 shows the glass tube and the silicon unit connection

FIG. 9 shows the stationary metal support unit

FIG. 10 shows the rotating support & housing unit

FIG. 11-FIG. 19 shows the installation steps of the entire glass tube connector system

FIG. 20 shows the flexible expansion unit connection

FIG. 21 shows the connection of the expansion unit to the heat receiving pipe

FIG. 22 shows the flexible expansion unit

FIG. 23 shows the expanded and contracted positions of the expansion unit

FIG. 24 shows the necessity of high pressure separators in prior art systems

FIG. 25 shows the simple vertical loop design

FIG. 26 shows the vertical loop design

FIG. 27 shows the wind breaker

FIG. 28-a shows the losses in the inlet and outlet sides of the heat receiving unit in the prior art systems

FIG. 28-b shows the additional glass tube at the discharge side

FIG. 29 shows a rotating structure supporting the parabolic mirror panel.

FIG. 30 shows the rotating structure supporting the parabolic mirror panel in different positions.

The parts in the figures are numbered one by one and the corresponding terms of these numbers are given below.

• Center of gravity of all rotating parts (A)
• Focal point of the parabola (B)
• Aperture of the parabola (C)
• Metal expansion unit (101)
• Glass tube (102)
• Heat receiving pipe (103)
• Getter (104)
• Welding point (105)
• Heat receiving pipe (1)
• Glass tube (2)
• Insulator (3)
• Seal (silicon) unit (4)
• Top half of the rotating support structure (5)
• Bottom half of the rotating support structure (6)
• Heat receiver element, HRE (D)
• Vacuum seal and glass tube connector system (E)
• Ceramic unit (7)
• Ceramic unit halves (8)
• Ball socket (9)
• Bolt (10)
• Ball (11)
• Silicon unit back face (12)
• Silicon unit front face (13)
• Outer lip (14)
• Flanging part (15)
• Groove (16)
• Insulator back face (17)
• Stationary metal support unit (18)
• Bolt (19)
• U-ring (20)
• Rotating support and housing unit (21)
• Hinge (22)
• Assembly of balls/wheels (23)
• Connector (24)
• Vacuum sealing gaskets (25)
• Metal ring (26)
• Metal ring (27)
• Bolt (28)
• Flexible expansion unit (29)
• Blower (30)
• Metal ring (31)
• Screwed nipple (32)
• Screwed flange (33)
• Flexible ring (34)
• Silicon ring (35)
• Gasket (36)
• Metal ring (37)
• Bolt (38)
• The last glass tube connector assembly (39)
• The last Glass Tube, attached to the Flexible Expansion Unit (40)
• Connector assembly (41)
• Steam pipe anchor (42)
• Support leg (43)
• Support leg (44)
• Inlet flow rate (45)
• Hot water (46)
• Steam (47)
• The last glass tube and expansion unit (48)
• Sliding anchor (49)
• Fixed anchor (50)
• Glass tube of the next parabolic trough (51)
• Separator and heat expansion loop (52)
• Wind breaker (53)
• Parabolic trough (54)
• Wind (55)
• Inlet side (56)
• Outlet side (57)
• Additional glass tube (58)
• Foundation (59)
• Stationary structure (60)
• Rotating structure (61)
• Parabolic surface covered by mirror (62)
• Rope is fixed to the rotating structure (63)
• Ropes for system rotation (64)
• Half circular stationary structure (65)
• Wheels (66)

DETAILED DESCRIPTION OF THE INVENTION

A solar trough field system according to the invention comprises multiple parabolic reflectors; a thermal receiver tube, center of which coincides with the focus of the parabolic reflectors and which consists of a metal heat receiving pipe (1) and a glass tube (2) which are nested (the glass tube surrounds the metal heat receiving pipe from outside); a “vacuum seal and glass tube connector system” (E) which connects the glass tubes (2) and the thermal heat receiving pipe (1) to each other; a rotating support unit (21), which connects the parabolic panel to the glass tube connector system (E) and provides the thermal receiver tube (1) to stay stationary while the parabolic panel is rotating around it; “flexible expansion unit” (29) located at the end of each parabolic trough unit which provides vacuum seal while the Heat Receiving Pipe (1) is moving due to heat expansion; and a vertical loop (52) located at the discharge side of the parabolic unit, which can be used instead of water separator and which also provides the heat expansion of the Heat Receiving Pipe (103).

FIG. 3 shows the entire “vacuum seal and glass tube connector system” (E) connecting the glass tubes (2) to each other and to the metal heat receiving pipe (1). This system has three functions, these are: to allow the metal heat receiving pipe (1) to expand and move freely within and independent of the glass tubes (2); to provide vacuum seal; and to provide support for the entire Heat Receiver Element (D). The vacuum seal and glass tube connector system (E) also provides a continuous vacuum chamber for the full length of the parabolic through unit, allowing for the creation and repeated maintenance of the vacuum from a single valve located at either end of the parabolic trough unit, eliminating the need for the currently used “getter” sticks to absorb Hydrogen. This system also decreases the maintenance and replacement expenses; which will arise in case of breaking the glass tubes (2).

The vacuum seal and glass tube connector system (E) comprises a ceramic unit (7) which allows the heat receiving pipe (1) to expand and slide freely over the balls (11) located at the centre of the ceramic unit (7) and provides heat insulation between the heat receiving pipe (1) to be located at it's center and the glass tubes (2); a silicon unit (4) which provides vacuum seal around the glass tube (2) and provides enough flexibility to protect the glass tube (2) from vibrations and bending forces that may occur on the metal parts; a heat and UV protection unit (3) which provides UV light and heat insulation for the silicon unit (4); and a stationary metal support unit (18) to provide the base for all the glass tube connection units.

In FIGS. 4 and 5, the ceramic unit (7) is shown in detail. The ceramic unit (7) consists of two hollow cylindrical parts (8). On one side of each half (8), there exits a number of ball sockets (9) (preferably six ball sockets). Six balls (11) are housed in between the two halves (8) of ceramic unit (7), within these ball sockets (9), forming a type of “ball bearing”. These two halves (8) of ceramic unit (7) are glued together with heat resistant glue; making sure that the glue does not get close to the balls (11); after the balls (11) are placed in between them (8). In addition to glue, the Ceramic halves (8) are also bolted (10) together for additional strength. The balls (11) are preferably made up of ceramic, but other materials can also be used.

FIG. 6 shows the front and side views of the silicon unit (4). The silicon unit (4) is in the shape of a hollow cylinder, wherein the back face (12) of this hollow cylinder extends with a larger diameter and provides a flange like shape (15) and on the front face (13) of the silicon unit (4), there exists a circular groove (16) (the glass tube slides into this groove). The outer lip (14) of the silicon unit (4) is kept thin to increase its flexibility so that as vacuum is applied within the glass tube (2), Atmospheric pressure will cause it to seal on the outside surface of the glass tube (4), providing a strong vacuum seal. The material of this unit needs to be selected to provide good seal on the glass, be flexible under high temperatures and have a long operational life. For this purpose a special silicone material has been selected for the pilot unit, but it may be some other material to meet the same qualifications.

Even special silicon designed for high temperature use, are sensitive to ultraviolet light (UV). Thus it should be shaded from sunlight. This is especially important on the internal surface of the silicon unit where concentrated light might hit it. A flexible Insulator Unit (3) is used to slide in and cover the inner face, which also provides some insulation against radiant heat transfer through the vacuum to the silicon unit (4). The front and side views of the heat and UV protection unit (3) is shown in FIG. 7. As can be seen in this figure, the heat and UV protection unit (3) has a hollow cylindrical shape, wherein the back face (17) of this hollow cylinder extends with a larger diameter which also covers the front face (13) of the silicon unit (4) and provides a better insulation. This unit can be produced from any material which does not chemically react when subjected to light and heat, preferably ceramic wool is used.

In FIG. 8, the glass tube (2) and the silicon unit (4) connection is shown. The UV insulator (3) is placed in the inner hollow part, and the glass tube (2) is slide into the groove (16) of the silicon unit (4).

FIG. 9 shows the side and front views of the stationary metal support unit (18). As can be seen in FIG. 9, the base of the metal support unit (18) is a circular ring, with its outer lips forming a cylindrical u-ring (20). Bolts (19) to which gaskets, metal rings and silicon pieces will be fitted are welded to the metal piece to eliminate nuts inside the u-ring (20) where there will be alignment wheels and/or alignment balls.

In FIG. 10, the side and front views of the rotating support and housing unit (21) is shown. This unit comprises the assembly of alignment balls (or wheels) (23) which provide multi directional guide for this rotating support (21) and housing unit to glide around the glass tube connection system (E); the hinge (22) to allow the top half of this support unit (21) to open while the glass tubes (2) are installed and with the help of this hinge (22), after the glass tube (2) installation is completed, the top half of this support unit (21) is closed and fixed to the bottom half; a connector (23) to the support leg that is attached to the parabolic trough.

From FIG. 11 to FIG. 19, the installation of the entire glass tube connector system (E) is explained. These steps are:

• • 1. Stationary Metal Support Unit (18) is slid on to the Heat Receiving Pipe (can be seen in FIG. 11)
  • 2. Ceramic Unit is slid over the Heat Receiving Pipe (1) and fitted within the Stationary Metal Support Unit (18). (FIG. 12)
  • 3. Vacuum sealing gaskets (25) are fit on the bolts (19) on both side of the Metal

Support Unit (18). (FIG. 13)

• • 4. Metal rings (26) are fit on the bolts (19) on both side of the Metal Support Unit (18). The purpose of these rings (26) is; to press on the flexible gasket (25) to provide vacuum seal, and to provide guides to the silicone unit (4) in the centre, preventing it from sliding out of the Metal Support Unit (18). (FIG. 14)
  • 5. Glass tubes previously (2) fitted into silicone units (4) are slid in to position from both sides. (FIG. 15)
  • 6. Metal rings (27) are slid on the Silicon to press on it to provide vacuum seal. (FIG. 16)
  • 7. The entire unit is tightened up by the bolts (28). (FIG. 17)
  • 8. Whole assembly is set on the bottom half (6) of the rotating support and housing unit (21). (FIG. 18)
  • 9. The top half (5) of the rotating support and housing unit (21) is lowered and tightened up. (FIG. 19)

After the last glass tube connector system (E) is placed, the flexible expansion unit (29) is attached to the support unit (18) same as if another glass tube (2) assembly is being fit on (As can be seen from FIG. 20). (Same gaskets, metal rings, etc.). The purpose of this assembly is to provide vacuum seal while the heat receiving pipe (1) is moving due to heat expansion.

Connection of the expansion unit (29) to the heat receiving pipe (1) can be seen in FIG. 21. These connection steps are;

• 1. Screwed nipples (32) are welded to the pipes (1);
• 2. Screwed flanges (33) are fitted on to the screwed nipples (32);
• 3. Flexible rings (34) are trapped in between the inner lips of the flanges (33) and the wall thickness of the screwed nipples. This is to provide additional seal for high pressure steam within the pipe (1);
• 4. A silicone ring (35) is fitted over the flange (33). The purpose of this silicon piece is to prove heat insulation between all the metal parts and the flexible expansion unit (29);
• 5. A gasket (36) is used to provide vacuum seal;
• 6. Metal rings (37) are used to tighten the flexible gaskets (36);
• 7. Bolts (38) are tightened to fix the entire assembly;

In FIG. 22, the last glass tube connector assembly (39) at the discharge side of the parabolic trough; the last glass tube attached to the flexible expansion unit (40); the flexible expansion unit (29); the connector assembly (41) fixing the expansion unit (29) to the steam pipe, which is the final vacuum seal point; steam pipe anchor (42) that allows the pipe to slide out as expands while preventing it from moving up and down; support leg (44) to the anchor unit and; support legs (44) attached to the parabolic trough, which units rotate along with the parabolic trough while providing support to the heat receiving assembly that is stationary, can be seen.

FIG. 23 shows the expanded and contracted positions of the expansion unit (29). As can be seen, while the steam pipe expands, there is no movement on the glass tube side.

The solar trough field system according to the present invention includes vertical loops (a simpler design can be seen from FIG. 25, the vertical loop can be seen from FIG. 26) between successive parabolic troughs connected in series, located at the discharge side of the parabolic trough unit. These vertical loops (52) can be used instead of separators.

Since water is heavier than steam, with the help of the vertical loop almost all of it will remain in the heat receiving pipe (1) until it becomes steam. If the flow rate of the water (45) is too high, some of the water can overflow through the first one or two of the vertical loops between successive parabolic trough units connected in series. However dry steam is achieved after the third or fourth parabolic trough units, eliminating the currently used multitude of separators located on the ground in between parabolic trough units.

The existing designs can not utilize this vertical unit since their Heat Receiving Assembly rotates along with the parabolic trough structure. In other words, as it rotates, it would loose its elevation and let the water flow out. This does not happen in the present invention since the heat receiving assembly is fixed.

As can be seen from FIG. 26, the vertical loop design (52) also provides the heat expansion function for the heat receiving pipe. According to this design, after the last glass tube and expansion unit (48) of the previous parabolic trough, the steam pipe passes trough the sliding anchor (49) and after forming a vertical loop (52) it reaches the fixed anchor (50) located at the inlet side of the next parabolic trough. By this way, the extension will increase the height or width of the loop, but it will not affect any of the parabolic troughs.

In an embodiment of the present invention, the solar trough field system also includes 2 m high wind breaker (53) to surround the solar trough field to deflect the wind (55) above the parabolic troughs (54). Wind loads both with and without this wind breaker (53) is simulated by running FLUENT and NASTRAN programs, and it is seen that with this wind reflector up to 125 Km/Hr winds can be reached without serious problems while the current designs have to be shut down at winds reaching about 60 Km/Hr. The effect of this wind breaker can simply be seen from FIG. 27.

Solar incidence hits the ground at an angle. This angle increases as we move further North or South from the Equator. In existing Solar Trough Field installations the total length of the glass tube (2) and heat receiving pipe (1) assemblies are equal to the length of the Solar Trough (As can be seen from FIG. 28a).

This causes two sources of inefficiencies:

• a) A significant length of the Heat Receiving Assembly at the inlet side (56) does not receive the concentrated solar light;
• b) An additional significant length of the concentrated solar light misses the Heat Receiving Assembly at its discharge side (56).

For this case, in an embodiment of the present invention, an additional glass tube (58) is assembled at the discharge side and the solar energy that is missed in the existing system is recovered. This is possible due to the fact that the Heat Receiving Assembly is stationary in this present invention (see FIG. 28b).

FIG. 29 and FIG. 30 shows another embodiment of the present invention which shows a rotating structure (61) supporting the parabolic mirror panel (62) by pulling the ropes (64). This is just an example of such a support and rotation structure (61). Same can be achieved by many different detail modifications. The important thing here is that the rotating structure is rested on many wheels (66) positioned on a half circular stationary structure (65). These wheels (66) allow easy movement and good resistance to wind loads. These ropes (64) are pulled by a central motor with adjustable speed. The speed is adjusted as required by solar sensors, so that the tracking of the sun is accurate.

The developments in the above preferred solar trough field systems are not intended to limit the protection scope of the invention. According to the information described with the invention, modifications to be performed on the developments in this preferred solar trough field systems should be evaluated within the protection scope of the invention.

Claims

1. A solar trough field system, comprising multiple parabolic reflectors; a thermal receiver tube, center of which coincides with the focus of the parabolic reflectors and which consists of a metal heat receiving pipe (1) and a glass tube (2) which are nested, characterized in that to allow the metal heat receiving (1) pipe to expand and move freely within and independent of the glass tubes (2), to provide vacuum seal, to provide support for the entire heat receiver element (D), and to provide a continuous vacuum chamber for the full length of the parabolic through unit, a vacuum seal and glass tube connector system (E) connects the glass tubes (2) and the thermal heat receiving pipe (1) to each other; in order to provide the thermal receiver tube (1) to stay stationary while the parabolic panel is rotating around it, a rotating support unit (21) connects the parabolic panel to the glass tube connector system (E); in order to provide vacuum seal while the heat receiving pipe (1) is moving due to heat expansion, flexible expansion units (29) are located at the end of each parabolic trough unit; and in order to prevent the non evaporated remaining water to pass through other collectors and to provide the heat expansion factor for the heat receiving pipe (1), vertical loops (52) are placed between successive parabolic troughs connected in series, located at the discharge side of the parabolic unit.

2. A solar trough field system according to claim 1 wherein, the vacuum seal and glass tube connector system (E) comprises a ceramic unit (7) in order to allow the heat receiving pipe (1) to expand and slide freely over balls (11) located at the centre of the ceramic unit (7) and to provide heat insulation between the heat receiving pipe (1) to be located at it's center and the glass tubes (2); a silicon unit (4) in order to provide vacuum seal around the glass tube (2) and to provide enough flexibility to protect the glass tube (2) from vibrations and bending forces that may occur on the metal parts; a heat and UV protection unit (3) in order to provide UV light and heat insulation for the silicon unit (4); and a stationary metal support unit (18) to provide the base for all the glass tube connection units.

3. A solar trough field system according to claim 2 wherein; the ceramic unit (7) consists of two hollow cylindrical halves (8); on one side of each half (8), there exits a number of ball sockets (9); balls (11) are housed in between the two halves of ceramic unit (7), within these ball sockets (9), forming a type of “ball bearing”; these two halves (8) of ceramic unit (7) are glued together, making sure that the glue does not get close to the balls (11), after the balls (11) are placed in between them (8); in addition to glue, the ceramic halves (8) are also bolted (10) together for additional strength.

4. A solar trough field system according to claim 3 wherein, said balls (11) are made up of ceramic.

5. A solar trough field system according to claim 2 wherein; the silicon unit (4) is in the shape of a hollow cylinder, wherein the back face (12) of this hollow cylinder extends with a larger diameter in order to provide a flange like shape (15); on the front face (13) of the silicon unit (4), there exists a circular groove (16); the outer lip (14) of the silicon unit (4) is kept thin to increase its flexibility.

6. A solar trough field system according to claim 2 wherein; the heat and UV protection unit (3) is a flexible insulator unit, used to slide in and cover the inner face of the silicon unit (4).

7. A solar trough field system according to claim 2 or claim 5 wherein; the heat and UV protection unit (3) has a hollow cylindrical shape, the back face (17) of this hollow cylinder extends with a larger diameter in order to cover the front face (13) of the silicon unit (4).

8. A solar trough field system according to claim 2, claim 5 or claim 6 wherein, the heat and UV protection unit (3) is made up of ceramic wool.

9. A solar trough field system according to claim 2 wherein, the base of the metal support unit (18) is a circular ring, with its outer lips forming a cylindrical u-ring (20), bolts (19) to which gaskets, metal rings and silicon pieces will be fitted are welded to the metal piece of this metal support unit (18) to eliminate nuts inside the u-ring (20) where there will be alignment wheels and/or alignment balls.

10. A solar trough field system according to claim 2 wherein; the rotating support and housing unit (21) comprises assembly of alignment balls (or wheels) (23) which provide multi directional guide for this rotating support (21) and housing unit to glide around the glass tube connection system (E); hinge (22) to allow the top half of this support unit (21) to open while the glass tubes (2) are installed and with the help of this hinge (22), after the glass tube (2) installation is completed, the top half of this support unit (21) is closed and fixed to the bottom half; a connector (23) to the support leg that is attached to the parabolic trough.

11. A solar trough field system according to claim 2 wherein; the entire glass tube connector system (E) is installed as follows; stationary metal support unit (18) is slid on to the heat receiving pipe (1), ceramic unit (7) is slid over the heat receiving pipe (1) and fitted within the stationary metal support unit (18), vacuum sealing gaskets (25) are fit on the bolts (19) on both side of the metal support unit (18), metal rings (26) are fit on the bolts (19) on both side of the metal support unit (18), glass tubes (2) previously fitted into silicone units (4) are slid in to position from both sides, metal rings (27) are slid on the silicon unit (4) to press on it to provide vacuum seal, the entire unit is tightened up with bolts (28), whole assembly is set on the bottom half (6) of the rotating support and housing unit (21), the top half (5) of the rotating support and housing unit (21) is lowered and tightened up.

12. A solar trough field system according to claim 10 wherein; after the last glass tube glass tube connector system (E) is placed, the flexible expansion unit (29) is attached to the support unit (18) same as if another glass tube (2) assembly is being fit on.

13. A solar trough field system according to claim 1 wherein; connection of the expansion unit (29) to the heat receiving pipe (1) comprises the following steps: screwed nipples (32) are welded to the pipes (1); screwed flanges (33) are fitted on to the screwed nipples (32); flexible rings (34) are trapped in between the inner lips of the flanges (33) and the wall thickness of the screwed nipples, a silicone ring (35) is fitted over the flange (33), a gasket (36) is used to provide vacuum seal, metal rings (37) are used to tighten the flexible gaskets (36), bolts (38) are tightened to fix the entire assembly.

14. A solar trough field system according to claim 1 wherein; after the last glass tube (2) and expansion unit (48) of the previous parabolic trough, the heat receiving pipe (1) passes trough the sliding anchor (49) and after forming a vertical loop (52) it reaches the fixed anchor (50) located at the inlet side of the next parabolic trough.

15. A solar trough field system according to claim 1 wherein, the system also includes a 2 m high wind breaker (53) to surround the solar trough field to deflect the wind (55) above the parabolic troughs (54).

16. A solar trough field system according to claim 1 wherein, an additional glass tube (58) is assembled at the discharge side of the system.

17. A solar trough field system according to claim 1 wherein, in order to allow the easy movement parabolic reflectors (62) and good resistance against wind loads, the system comprises a rotating structure (61) that is rested on many wheels (66) positioned on a half circular stationary structure (65).

18. A solar trough field system according to claim 16 wherein, the rotating structure (61) is supporting the parabolic mirror panel (62), by pulling the ropes (64) which ropes (64) are pulled by a central motor with adjustable speed.

19. A solar trough field system according to claim 17 wherein, the speed of the central motor is adjusted by solar sensors.