Patent Application
20190157483
The present invention generally relates to photovoltaic devices, particularly for solar modules integrated in solar energy concentrator systems. More specifically, the principal embodiment of the present invention relates to the internal electrical circuitry connecting solar cells in a solar module.
With the worldwide population growing steadily, demand for energy scales up. This intensifying demand takes place in a time when traditional sources of energy face particular pressure due to the scarcity of resources as well as stronger calls by customers and households for energy sources that minimize the negative environmental impact. To help solve this problem, solar energy constitutes an attractive and reliable alternative based on a readily available energy source—solar light. In this context, there is a need for a better use of solar energy, more specifically, for means that provide a better collection of concentrated solar radiation.
A solar cell is typically made of semiconductor materials, such as silica, with at least one layer of positively charged materials and one layer of negatively charged materials together creating an electric field. When solar radiation impinges on a solar cell, electrons are knocked off and wander around in accordance with the electric field. If the layer of positively charged materials is paired with the layer of negatively charged materials through a conductive component, the electrons that are knocked off will rather move to and through this conductor, thereby forming an electrical circuit. Electrons traveling through this conductor can be used as electrical energy by external applications, before returning to the solar cell. A plurality of solar cells can be grouped together as a solar panel or module in order to cover a larger area and, this way, generate more electrical current or power, or more of both.
When a solar module is oriented toward the sun without obstacles, the solar radiation impinging on the solar module is uniform throughout the surface of the solar module. With this orientation, each solar cell constituting the solar module receives the same amount of radiation. As a result, each of these solar cells generates more or less the same current intensity. When connecting these solar cells in series, their voltage is added, while the current that is generated is equal to the lowest current generated by any of the solar cells. Consequently, because solar cells receiving uniform solar radiation generate more or less the same current intensity, they can be connected in series to increase the voltage output of the module without substantial loss in current intensity.
In a solar energy concentrator system, the solar module is rather oriented toward a concentrator, which typically redirects solar radiation unevenly. Because of this uneven diffusion, there is a significant difference between the current intensity produced by each of the solar cells constituting the solar module. Should the solar cells of the solar module be connected in series, the resulting current intensity of the solar module would be equal to the least-performing of the solar cells, despite the fact that some of those solar cells generate more current. This loss is significant, affecting the technical performance of solar energy concentrator systems as well as their cost-efficiency. Should the solar cells in a solar energy concentrator system be connected in parallel instead, the voltage that would be generated might be too low for the current to flow smoothly through the circuit's resistance. An energy-intensive convertor, a charge pump or an equivalent device would be required to increase the voltage, thereby negatively affecting the overall performance and cost-efficiency of the system.
The present invention implements a particular configuration of solar cells and circuitry that, when integrated into a solar energy concentrator system, circumvent the problems described above. Despite being particularly beneficial when integrated to a solar energy concentrator system, it can function in combination with non-concentrating solar energy systems. Solar energy concentrator systems offer various benefits over non-concentrating solar energy systems: for an equivalent electrical output, significantly less resources and space are required to operate a solar energy concentrator system. However, the operation of solar energy concentrator systems with solar modules involves particular inefficiency factors such as the uneven diffusion of solar light, heat and electrical resistance. These factors must be addressed in an efficient solar energy concentrator system.
In a solar module characterized by the principal embodiment of the present invention, a very high number of solar cells are assembled together. The solar cells are distributed into multiple sets, each of these sets containing a certain number of solar cells. In a two-part electrical circuit, solar cells within each set form a parallel circuit, while the sets are connected together in series. Preferably, the solar module comprises a large number of sets, and each set connects numerous solar cells together.
The solar cells that constitute a set are determined with a particular configuration by which the current intensity generated by each of the sets is more or less the same. In the second stage of the electrical circuit, the sets are connected together in series, thereby increasing the voltage of the electrical circuit of the solar module. Since sets are determined such that the current intensity of each set is relatively the same to one another, current intensity inefficiencies in the second stage of the electrical circuit are small or minimal.
In the principal embodiment of the present invention, the solar cells constituting each of the sets are numerous and randomly selected. With these set selection characteristics, it is very probable statistically that the current intensity generated by each of the sets is more or less the same. Since the current intensity of each set is very likely to be similar to one another, the probability of current intensity inefficiencies in the second stage of the electrical circuit is small.
In a first alternate embodiment, the solar cells constituting each of the sets are not selected randomly but instead determined on the basis of prior simulations or calculations maximizing the current output of the set that produces the least current. Calculations yielding this result are known as “minimax”. The simulations or calculations can also be achieved during operation, with the sets being mechanically or electronically re-configured mid-operation. In this first alternate embodiment, the two-stage electrical circuitry within and between the sets is the same as in the principal embodiment.
In a second alternate embodiment, the solar cells constituting each of the sets are selected radially instead of being randomly determined. In this configuration, each set of the solar module follows a radial pattern, diverging in line from the center of the solar module. A solar energy concentrating system can be operated in a way that aligns the center of the solar module with the center of the target area of redirected solar radiation. In these circumstances, the current intensity of the various sets designed radially is very likely to be roughly the same. In this second alternate embodiment, the two-stage electrical circuitry within and between the sets is the same as in the principal embodiment.
In a third alternate embodiment, the solar cells constituting each of the sets are selected circularly instead of being randomly determined. In this configuration, each set of the solar module follows a roughly circular, oval, spiral or helical pattern designed around the center of the solar module. Preferably, the solar cells constituting each set are not adjacent to one another. As the solar cells constituting each set are widely distributed across the surface of the solar module when they are not adjacent, the expected output obtained with this embodiment can be somewhat similar to the expected output of the principal embodiment whereby sets are determined randomly. In this third alternate embodiment, the two-stage electrical circuitry within and between the sets is the same as in the principal embodiment.
In a fourth alternate embodiment, the solar cells constituting each of the sets are selected linearly instead of being randomly determined. In this configuration, each set of the solar module follows a roughly linear pattern passing by or near the center of the solar module. Preferably, the solar cells constituting each set are not adjacent to one another. A solar energy concentrating system can be operated in a way that aligns the center of the solar module with the center of the target area of redirected solar radiation. In these circumstances, the current intensity of the various sets designed linearly is very likely to be roughly the same. In this fourth alternate embodiment, the two-stage electrical circuitry within and between the sets is the same as in the principal embodiment.
In a fifth alternate embodiment, the solar module is constituted of many sub-modules. In this embodiment, the solar cells constituting each of the sets are selected on the basis of their position in each sub-module instead of being randomly determined. As the solar cells constituting each set are widely distributed across the surface of the solar module, the expected output obtained with this embodiment can be somewhat similar to the expected output of the principal embodiment whereby sets are determined randomly. In this fifth alternate embodiment, the two-stage electrical circuitry within and between the sets is the same as in the principal embodiment.
In an additional embodiment of the present invention, the resistance of the circuit is significantly reduced even when the solar cell receives concentrated solar radiation up to thirty suns or more, thus allowing a high output of electrical conversion. In this additional embodiment, solar cells are connected together to form an electrical circuit. The solar cells can be standard solar cells so long as they are designed in a way that their electrical contacts and other conductive elements are positioned on their back sides, whereon conductors with relatively high resistance are located. The solar cells are installed on a printed circuit board or any other equivalent support. The printed circuit board comprises a substrate and conductors with relatively low resistance, which are typically thicker or wider (or both) than the conductors with relatively high resistance on the solar cells. The conductors with relatively high resistance on the solar are coupled to the conductors with relatively low resistance on the printed circuit board through one of various means, for instance, solder balls. The solar cells are connected to the printed circuit board through the solder balls and, both ends of the solder balls are respectively aligned with the conductors with relatively high resistance on the solar cells and the conductors with relatively low resistance on the printed circuit board. Therefore, the conductors with relatively low resistance on the printed circuit board are aligned with the conductors with relatively high resistance on the solar cells in a design that reduces the resistance of the overall electrical circuit.
The invention is described in more detail below with respect to an illustrative embodiment shown in the accompanying drawings in which:
The components in the figures are not necessarily drawn to scale. Where used in the various figures of the drawings, the same numerals designate the same or similar parts.
For reference purposes only, the present invention is disclosed as being integrated into a solar energy concentrating system. A person skilled in the art would recognize that the present invention can be integrated to many other concentrating and non-concentrating solar energy systems. An example of a solar energy concentrating system 1 is illustrated in
In that example of a solar energy concentrating system 1, the lateral arm 6 supports a solar module 8 that can be attached or connected to the lateral arm 6 in various ways. A motorized system inside the lateral arm 6 allows the solar module 8 to move along the lateral arm 6. In addition, a motorized system inside the two lateral beams 5a that support the lateral arm 6 allows the lateral arm 6 to be moved along the entire lengths of the two lateral beams 5a to which the lateral arm 6 is connected. The solar module 8 is installed in a way that allows its rotation. With the rotation of the solar module 8, the movement of the solar module 8 along the lateral arm 6, and the movement of the lateral arm 6 along the two lateral beams 5a to which the lateral arm 6 is connected, the structure is capable of moving the solar module 8 at or near any location of the focal area of concentrated solar radiation. A mirror reflector 9 can be fastened against the solar module 8. If there is solar radiation that is redirected by the concentrating reflector 2 and whose trajectory does not meet the space covered by the solar module 8, the mirror reflector 9 potentially diverts some of it toward the solar module 8.
In the principal embodiment of the present invention, illustrated in
Likewise, the optimal sizes for the solar module 8b and for the solar cells 12 would depend upon the particular solar energy system in which they are integrated. In the solar energy concentrating system 1 illustrated in
In the principal embodiment of the present invention, the solar cells 12 constituting each of the twenty-four sets are determined randomly. In
The electrical circuit in the present invention's solar module 8c is designed in two stages. In a first stage, the ten solar cells 12 constituting a given set form a parallel circuit: this way, the current that is generated by each of the solar cells 12 within a set is added up together, ensuring that the current intensity obtained for the set is at its full potential. When the solar cells 12 constituting each of the sets are numerous and randomly selected as is the case with the present embodiment, it is very probable statistically, in accordance with the central limit theorem, that the average current intensity generated by each of the sets is more or less the same. In other words, when the solar module 8c is operated, the set that generates the most current is unlikely to produce a lot more than the set that generates the least current. As the number of solar cells 12 per set increases, the expected variance between sets decreases, meaning that the likelihood of substantial differences between set outputs of current intensity decreases as the number of solar cells 12 per set increases.
In the second stage of the electrical circuit, the twenty-four sets are connected together in series, thereby increasing the voltage of the electrical circuit of the solar module 8c. Since the current intensity of each set is very likely to be similar to one another, the probability of current intensity inefficiencies in the second stage of the electrical circuit is small. Compared with a standard solar module 8a integrated to a solar energy concentrating system, the design of the present invention offers a significantly better technological performance and is more cost-efficient.
In a first alternate embodiment, the solar cells 12 constituting each of the sets are not selected randomly but instead determined on the basis of prior simulations or calculations maximizing the current output of the set that produces the least current. Calculations yielding this result are known as “maximin”. In most situations where simulations or calculations are achieved this way, they would require being adapted to the particular solar energy concentrating system into which the solar module 8b is integrated. For instance, environmental simulations with the solar module 8b may be necessary in order to accurately assess which areas of the solar module 8b tend to receive relatively more concentrated solar radiation than others once in operation. The simulations or calculations can also be achieved during operation, with the sets being mechanically or electronically re-configured mid-operation. Although the present embodiment is likely to offer a better performance than the principal embodiment, it is also more complex as its performance is dependent upon customization with the related solar energy system and with the location where the solar module 8b would be used. In this first alternate embodiment, the two-stage electrical circuitry within and between the sets is the same as in the principal embodiment.
In a second alternate embodiment, illustrated in
In a third alternate embodiment, illustrated in
In a fourth alternate embodiment, illustrated in
In a fifth alternate embodiment, illustrated in
Standard solar cells are designed to be oriented directly toward the sun and convert the resulting energy output into electricity. In an electrical circuit formed by a solar module constituted of standard solar cells that are concatenated, the energy is conducted to, and from, a convertor or inverter through conductors at the solar cells (which can comprise electrical contacts, metal contacts, conductive lines or any similar conductive element). When a solar cell receives concentrated solar radiation, the amount of energy that is generated is significantly higher than the amount otherwise generated when the solar cell is oriented toward the sun—for instance, potentially more than thirty suns with the solar energy concentrating system 1 described above. However, the conductors in a standard solar cell are not designed to conduct such a high amount of energy, causing a lot of resistance that reduces the efficiency of a solar energy concentrating system. To reduce the resistance directly at the solar cell's circuitry, some designs integrate wider and thicker conductors, but the dimensions of a solar cell impose inherent constraints to the width and thickness of conductors on a solar cell. Because of those constraints, even known-in-the-art designs with wider or thicker conductors on the solar cell are insufficient to efficiently conduct energy produced by a solar energy concentrator system.
The present additional embodiment discloses a technical solution that circumvents the physical limitations of solar cells and successfully reinforces these conductors. With this embodiment, the resistance of the circuit is significantly reduced even when the solar cell receives concentrated solar radiation up to thirty suns or more. In this additional embodiment of the present invention, illustrated in
The conductors with relatively high resistance 19 on the solar cells 12 are coupled to the conductors with relatively low resistance 21 on the printed circuit board 20 through one of various means, for instance, solder balls 22. A person skilled in the art would recognize that equivalent coupling means can be used instead of solder balls 22, such as coined solder balls, solder pads, solder bumps, metal eyelets, a ball grid array, and so forth. A person skilled in the art would also recognize that the number, location, size and pattern of the solder balls 22 or equivalent coupling means can vary, so long as they produce a conductive connection or coupling between the conductors with relatively high resistance 19 on the solar cells 12 and the conductors with relatively low resistance 21 on the printed circuit board 20. A person skilled in the art would further recognize that, so long as they are conductive, there could be more than one coupling component between the conductors with relatively high resistance 19 on the solar cells 12 and the conductors with relatively low resistance 21 on the printed circuit board 20. In one embodiment, the conductors with relatively high resistance 19 on the solar cells 12 are coupled to the conductors with relatively low resistance 21 on the printed circuit board 20 through solder lines that are each adjacent to segments—or all—of both a conductor with relatively high resistance 19 on the solar cells 12 and to a conductor with relatively low resistance 21 on the printed circuit board 20.
When solar radiation impinges on the solar cells 12, the charge carriers—electrons and holes—are knocked off their atomic bonds and are free to circulate. Circulating electrons are collected by the conductors with relatively high resistance 19 on the solar cells 12. When electrons are conducted up to a solder ball 22, they then flow, through this conductive solder ball 22, toward the conductors with relatively low resistance 21 on the printed circuit board 20. The conductors with relatively low resistance 21 on the printed circuit board 20 thereafter bring the electrons to an electrical circuit (not shown) that is external to the solar cells 12. Within this circuit, they can be used as current for electrical purposes before being brought back in a similar way to the solar cells 12, where they can fall back into empty holes.
This exemplary structure reinforces the conductors 19 on the solar cells 12 and reduces the electrical resistance of the circuit in two ways. First, the electrons travel only a small distance in the conductors with relatively high resistance 19 on the solar cells 12 before moving, through a solder ball 22, in the conductors with relatively low resistance 21 on the printed circuit board 20. As a result, even if the solar cells 12 were to be designed as a series circuit, the conductors with relatively high resistance 19 on the solar cells 12 would only carry current for their respective solar cells 12 (except for the possibility of electrons circulating incidentally). Second, for the most part, the current flows through the conductors with relatively low resistance 21 rather than through the conductors with higher resistance 19, thereby considerably reducing the circuit's resistance in comparison with a circuit entirely designed on the solar cells 12.
The present additional embodiment increases the efficiency of a solar energy concentrator system by itself. Yet, its efficiency benefits accrue even more when in combination with the principal embodiment of the present invention, because reducing the resistance of the electrical circuit overcomes an important obstacle to an efficient implementation of the principal embodiment. A person skilled in the art would recognize that the present additional embodiment can be combined with a variety of solar cells or solar modules and does not need to be combined with the principal embodiment of this invention. In addition, the present additional embodiment can be integrated into concentrating as well as non-concentrating solar energy systems.
While this invention has been particularly shown and described with reference to exemplary embodiments, it will be understood by those skilled in the art that various additions and changes in form and detail may be made therein without departing from the spirit and scope of the invention. The invention in its broadest, and more specific aspects, is further described and defined in the claims which now follow.
