1 A MODULAR SINGLE AXIS SOLAR TRACKING DEVICE AND A SYSTEM USING SAME FIELD OF THE INVENTIONThe present invention relates in general to systems for utilizing solar radiation, and particularly to solar systems implementing a single axis tracking technology. BACKGROUND OF THE INVENTIONThe ever-growing environmental problems of increasing energy demand and resource shortages require new technologies for utilizing energy sources and particularly utilizing renewable sources. One such technology relies on using solar trackers which are configured to tilt their solar collecting surfaces towards the sun. Among these solar trackers one may find solar panels, parabolic troughs, and heliostats. For flat-panel photovoltaic systems, where solar radiation is converted into electric energy, the trackers are used to minimize the angle of incident between the incoming sun rays and photovoltaic panels. Reducing this angle increases the amount of energy produced from a given amount of installed power generating capacity. As the pricing, reliability and performance of single-axis trackers have improved, the systems have been installed in an increasing number of utility-scale projects. In certain photovoltaics applications, trackers are used. Tracking systems are used because for such systems to operate, the collection efficiently of solar radiation is enhanced when the optical axis of the trackers is aligned with incident solar radiation, so that the solar photovoltaic collector is able to maintain its relative position throughout the day by remaining in a normal 2 position relative to the incident solar radiation. In other words, the use of a single axis tracking is implemented by having the collector oriented at azimuth north to south, and the tracking is affected in one direction – east to west across the day. Such field of photovoltaic collectors are typically characterized by having a long chain of photovoltaic panels, extending from south to north that is mounted on a tracker frame which tracks the sun from east to west. Such fields of photovoltaic panels typically make use of a single motor for the rotation of such a chain of photovoltaic panels in order to improve the system’s cost effectiveness. Thus, the trackers implemented in these fields that are known in the art, are designed for a maximal load of panels per tracker, using heavy duty components and reinforced materials. Such a design may further support another need, namely, having fields’ configuration that is robustness to torque that might develop due to wind forces that act on the long chain of collectors. In other words, using a wide massive beam as well as heavy duty components and reinforced materials is the prior art common solution to minimize the risks of exposure to failures due to developing torques and moments on the collectors’ structure. Moreover, the cost optimized design of photovoltaic ("PV") fields relies on using very long tracking chains where the supporting skeleton beam and rotating mechanism are mounted on the collector as described for example in the publications US 20190199276, US 9806669 and US 8459249. Another solution was proposed by US 20190199276 that discloses combining several long single axis trackers by using one moving motor via a linear rod or a cable that link all the rotating axes of the trackers. This way, the rotation of many panels can be affected by 3 a single motor. The beam can have a rounded cross section (US 20210103302) or a square cross section (US 9806669). However, the prior art solutions have a number of drawbacks. Rotating an increasing number of PV panels using the same rotating motor, results in an increasing weight which causes problems that adversely affect the motor’s operation. Especially, having a large number of panels in a chain might create a large momentum, particularly under windy conditions, in which case, the motor will not be capable to operate properly by rotating the chain of panels as required. Another disadvantage of the prior art systems in which such rigid tracking arrays designs are implemented, is, that the area used for the installation of a PV field should have a uniform topography (e.g., a flat area, a single slope area, etc.), as otherwise if the area is not leveled, the moment that will be developed at the rigid beams will cause its failure. Consequently, a typical solution to this disadvantage is flattening of a large area designed for the installation of the PV field, which is a cumbersome task that has to be performed by using heavy machinery. Moreover, there is another disadvantage of the prior art systems which has an increasing significance lately. This disadvantage arises from the need to install PV trackers on non-flat areas such as roofs, areas with non-uniform topography, fences, etc. Due to the nonuniformity of the ground level at which the PV panels are installed, there is a need to change the angles or orientation of the panels which are part of the chain of panels. Furthermore, the relatively recent use of bi-facial PV panels, which are more efficient but need clear space from both sides of the panel, create a challenge where 4 the rigid beam causes a penalty of shadowing and/or a need to rotate the heavy beam itself. Another disadvantage of the prior art solutions is, that the heavy structure of the tracker has to be mounted on a large number of supports along the rotating axis. These supports cause certain shadowing that blocks radiation reflected from the ground. When implementing a bifacial PV technology, such a shadowing effect becomes quite a substantial disadvantage. Another disadvantage associated with the prior art solution is the maintenance issue. Since these prior art solutions rely on using rigid structures that include heavy motors and arrays that comprise many units, once there is a need to carry out a repair/maintenance, it leads to a shutdown of many operational units. Yet another problem that the prior art trackers have, arises from the recent trend that photovoltaic solar fields would not have an adverse footprint on the environment. Hence, applications such as dual use of the fields’ areas became increasingly more interesting. For example, use of agriculture fields, green houses, fences, sideroads and roofs for generating solar driven energy thereat. Therefore, generating photovoltaic energy under complex topographical conditions becomes a leading necessity. However, to meet this challenge, systems unlike the prior art systems, require tracking solutions that can deal with such a complexity. The present invention seeks to provide a solution that overcomes the above disadvantages of the prior art systems. SUMMARY OF THE DISCLOSURE It is therefore an object of the present invention to provide a solar tracking device for use in a solar field which improves the operational efficiency of the solar field. It is another object of the present invention, to provide a solar tracking device having a substantially reduced weight, which in turn reduces certain problems described-above that occur while using prior art trackers. It is another object of the present invention, to provide a solar tracking module that enables using a flexible solar field design, by simply connecting any required number of panels’ modules to each other. It is another object of the present invention, to provide a solar tracking device that is adapted to be installed in a solar field in a way that is essentially free from problems associated with the installation of a solar field in a topographically non-uniform area. It is another object of the present invention, to provide a solar tracking module that reduces substantially maintenance problems associated with maintaining a solar field where the solar tracking modules are installed. It is another object of the present invention, to provide a solar tracking module that is adapted to substantially reduce shadowing effects in a field comprising such solar tracking modules. Other objects of the invention will become apparent as the description of the invention proceeds. According to a first embodiment, there is provided a single axis solar tracking module, comprising: at least two solar panels rotatably coupled to a rotational axis, wherein the rotational axis comprises a rod extending laterally along the at least two solar panels, wherein a first part of the rod extends laterally along a first of the at least two solar panels, and 6 comprises a protrusion that matches a cavity starting from an edge of the second part of that rod, and wherein the second part of the rod extends laterally along a second of the at least two solar panels that is located adjacent to the first solar panel, so that by inserting the protrusion into the cavity, the first and second solar panels are attached to each other thereby obtaining a combined rod, and wherein the combined rod is used as the solar panels’ rotational axis; a frame, for mounting the at least two solar panels thereat; a transmission system configured to rotate the frame of the single axis solar tracking module with the solar panels mounted thereat. In the following description and claims, the following terms should be understood to be used interchangeably while still having the same meaning: "single axis solar tracking module", "solar tracking module", "tracking module" and "module". Similarly, the terms "single axis solar tracking modules", "row of solar tracking modules" and "tracker" are also used interchangeably and have the same meaning. According to another embodiment of the present disclosure, the single axis solar tracking module further comprises a motor configured to rotate the single axis solar tracking module by using the transmission system thereof. In accordance with another embodiment of the present disclosure, at least one of the two solar panels is a bi-facial photovoltaic panel. According to still another embodiment, the single axis solar tracking module further comprises a static beam structure. The static beam structure is not located near the panels, and may be part of a structure that the 7 single axis solar tracking module is being installed thereat. By yet another embodiment, the protrusion and the cavity have both a polygonal cross section. According to another embodiment the single axis solar tracking module is configured to be associated with a structure beam located away from the rotational axis, at a distance which is equal to at least half of the solar tracking module’s width. In accordance with another embodiment, the single axis solar tracking module is configured to be connected to another such a single axis solar tracking module, by using a flexible joint. By still another embodiment, the frame of the single axis tracking module is configured to be attached to an object that has already been installed at a field where the single axis solar tracking module is about to be mounted. According to another embodiment, the single axis tracking module further comprises a radiation measuring sensor. Preferably, according to this embodiment, the single mode tracking module is configured to operate also in a solar backtracking mode. Solar backtracking mode refers to an operational mode that aims to minimize PV panel-on-panel shading, but yet be positioned as close as possible normal to the instantaneous sun orientation, (or in the present case, a row of the solar tracking modules on another row of the solar tracking modules), thus avoiding production losses, since a solar tracker, or a linked solar tracker row, when used near another, shades the adjacent other solar tracker particularly during early morning and late afternoon. According to another embodiment, the single axis tracking module is configured to operate in a way that 8 the two solar (photovoltaic) panels can reach up to ±90° relative to a virtual horizontal plane. By still another embodiment, the transmission system of the single axis solar tracking module is further configured to compensate for a distance extending between a center of the transmission system's final (last) gear wheel and between a center of mass of the at least two solar panels, by using a shift movement being proportional to an angle generated between the single axis solar tracking module and the ground, by the transmission system's final gear wheel rotation. Such proportional shift can be achieved by using a further, smaller grooved wheel which is positioned concentrically to the (outer) final gear wheel. This smaller grooved wheel may be attached to a linear (or nearly linear) grooved rod so that any rotational movement of the final gear wheel will cause a proportional linear shift. The ratio between the last gear wheel and the additional smaller wheel, that is responsible for the linear shift transfer, can be adjusted by doing a 90° degrees panel shift, so that the linear shift will move the center of mass of the at least two solar panels, exactly above the rotation axis, thereby eliminating the adverse impact of the torque generated due to the at least two solar panels weight. In accordance with another aspect of the present disclosure, there is provided a system comprising a plurality of single axis tracking modules of the present invention, wherein part of the plurality of single axis tracking modules are installed and operative above the operating remaining static or single axis tracking modules belonging to the plurality of single axis tracking modules. 9 According to another aspect of the present disclosure there is provided a method for use in a solar system comprising a plurality of single axis tracking modules (i.e., photovoltaic panels), wherein the method comprises a step of utilizing a radiation measuring sensor installed remotely from one or more of the single axis tracking modules. In accordance with yet another embodiment of the latter aspect, the method further comprises a step of utilizing a sensor installed underneath the one or more single axis tracking modules’ plane in order to limit the angular tracking range of the one or more single axis tracking modules, to a minimal rotation. Preferably, the rotation of the one or more single axis tracking modules is limited to a near vertical angles, thereby limiting the shadowing of the one or more single axis tracking modules’ panels at the middle of the day and allowing passing of sun rays. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention, reference is now made to the following detailed description taken in conjunction with the accompanying drawings in which simplified schematics of the single axis solar tracking module are illustrated, wherein: FIG. 1 - illustrates the schematic view of a single axis solar tracking module construed according to an embodiment of the present invention; FIG. 2 - illustrates a schematic blown view of part of the single axis solar tracking module of FIG. 1; FIG. 3 - demonstrates two single axis solar tracking modules that are connected to each other, where each of these two modules has a different orientation from the other; FIG. 4 - presents an embodiment of the present invention for overcoming topography problems created when installing a plurality of single axis solar tracking modules on slanted roofs; FIG. 5 - demonstrates an embodiment of the present invention by which the single axis solar tracking module can reach up to +/- 90° position relative to the ground; FIG. 6 - exemplifies an embodiment of the invention for implementing solar backtracking mode; FIG. 7 – illustrates an embodiment of the present disclosure wherein a plurality of single axis solar tracking modules are installed in an agricultural field; FIG. 8A and FIG. 8B - illustrate an embodiment for implementing the single axis solar tracking modules of the present invention, on sideroad fences. FIG. 8A illustrates their tilt angle at about noon time, whereas FIG. 8B illustrates their tilt angle during morning or evening times; FIG. 9 - illustrates an embodiment for implementing the single axis solar tracking modules of the present invention on greenhouses; FIGs. 10A to 10C – demonstrate an embodiment of the present invention, implementing installation of the single axis solar tracking modules in a two levels’ configuration, where the different FIGs. present their different inclination angles during the day. DETAILED DESCRIPTION In this disclosure, the term "comprising" is intended to have an open-ended meaning so that when a first element is stated as comprising a second element, the first element may also include one or more other 11 elements that are not necessarily identified or described herein, or recited in the claims. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It should be apparent, however, that the present invention may be practiced without these specific details. The present invention aims to provide a solar tracking device that can be installed in areas having varying topography, existing infrastructures, roofs, greenhouses and fences, in other words, constrains to which the systems known in the art, cannot provide a solution. Preferably, when installing the single axis solar tracking modules of the present invention, they will be positioned so that their rotational axis will coincide with the north-south direction, thereby enabling them to track the solar irradiation effectively by moving from east to west throughout the day. FIG. 1 illustrates a schematic view of a single axis solar tracking module 15 construed according to an embodiment of the present invention. In this example, as can be depicted from this FIG., single axis solar tracking module 15 comprises two solar panels that are held within a frame, which is mounted on a solid beam 16 (the latter is not a part of the single axis solar tracking module 15 ). Beam 16 is associated with a support pillar 17 , so that the structure of beam 16and pillar 17supports the weight of tracking module 15 attached thereto. A thin rod, shown in this FIG. as a thin rod that comprises two parts 12 and 13 , has an axis connected to element 14 via a series of gears that are configured to rotate the frame of panel frame solar tracking module 12