Patent Application
20110017282
The present invention relates generally to a photovoltaic module assembly in which a photovoltaic module is configured to transfer energy to an energy-receiving device through wireless coupling.
Photovoltaic technology has received remarkable attention as a method of supplying renewable energy to devices that require energy input. Energy transfer from photovoltaic modules to energy-receiving devices is typically achieved using external wires to connect from photovoltaic modules to metal access points within energy receiving devices.
One embodiment of the present invention includes a photovoltaic module assembly comprising a photovoltaic module and an energy-receiving device in which the photovoltaic module is configured to transfer energy to the energy-receiving device through the use of inductive coupling.
A second embodiment of the present invention includes a photovoltaic module assembly comprising a photovoltaic module and an energy-receiving device in which the photovoltaic module is configured to transfer energy to the energy-receiving device through the use of capacitive coupling.
Photovoltaic modules typically require the use of external wires to connect to metal access points in devices in order to transfer energy to those devices. However, many types of conditions can render such configurations disadvantageous, particularly in harsh environments. Under such conditions it might be desirable to harvest and transfer solar energy without the use of direct metal connections.
Under harsh conditions, it could be beneficial to implement a system in which a photovoltaic module can be brought in the vicinity of another device allowing energy transfer without the necessity of forming metal-to-metal wired connections between the photovoltaic module and the device. In such systems, coupling through a wireless configuration could be used to facilitate energy transfer. The resulting wireless coupling system could surmount some of the challenges that are presented by the use of metal wire connections.
The photovoltaic module and the energy-receiving device could each be separately sealed from the outside environment to facilitate efficient operation under harsh environmental conditions. Alternatively, the photovoltaic module and the energy-receiving device could be sealed together. Sealing could entail complete encapsulation allowing no externally exposed metal.
Embodiments of the present invention can be configured to apply in many situations, such as those in which a device needs to receive energy in harsh environments. For example, large ships generally operate under wet and salty conditions. In such circumstances, it could be advantageous to provide solar energy transfer without the use of direct metal connections that could increase the incidence of operational failure. To the extent that the present description describes energy transfer to an energy-receiving device, such description is not meant to limit the scope of the application of the technology.
Embodiments of the present invention can be configured to facilitate energy transfer in applications including but not limited to battery charging and primary energy source supply. Energy transfer in the present invention is intended to comprise power transfer as opposed to wireless information transfer. It is to be understood that the concepts of the present invention could just as easily be applied to facilitate other applications involving energy transfer.
Embodiments of the present invention provide a photovoltaic module and at least one energy receiving device. As used herein, the term “module” includes at least one photovoltaic cell and can include many electrically interconnected photovoltaic cells. The “energy-receiving device” is a device that is capable of receiving energy from a photovoltaic module.
Most photovoltaic modules harness solar energy and output direct current (DC). However, contactless energy transfer typically requires AC electrical excitation. Methods of energy transfer with no ohmic contact capitalize on the physics associated with permeability and/or permittivity of materials. These properties enable energy transfer at high frequency without use of direct current. As such, a photovoltaic module configured for contactless energy transfer may incorporate electronic circuitry which can perform functions such as interfacing with the electrodes of photovoltaic cells to create AC from DC.
Electronic circuitry capable of converting DC to AC is known to those skilled in the art. For example, conversion from DC to AC is employed in switching power devices, wherein high frequency capacitive coupling enables development of high side driver supplies. AC capacitive coupling is used in systems such as certain audio systems to permit only high frequency current to travel to small tweeters, as low frequency current can damage the tweeters. In another example, conversion from DC to AC is used to send energy magnetically at high frequency through a transformer whose primary is in a charging station and whose secondary is in an electric vehicle.
Electronic circuitry that converts DC to AC in the present invention could either be contained inside the large, flat portion of the photovoltaic module or could reside outside the photovoltaic module. In either circumstance, the electronic circuitry could be encapsulated with the photovoltaic module for protection from the outside environment.
Energy transfer through wireless coupling can be achieved using several different methods, including but not limited to inductive coupling and capacitive coupling. Inductively coupled systems require a means to guide magnetic field lines from one component (a primary) to a second component (a secondary). The magnetic field lines can pass through a non-magnetic material contained between two components.
Inductive coupling is particularly effective in situations where geometries of coupling interfaces allow current to flow in loops around iron cores, and wherein those iron cores can be configured so that magnetic field lines flow perpendicularly from one interface into another. In one example, photovoltaic modules might be able to develop 100 Watts of power. At such a power level, based on state of the art circuit components and techniques, inductive coupling can be employed to transfer energy from one sealed device to another. For inductively coupled systems, design elements include wire thickness, number of turns around an iron core, relative dimensions of the cross sectional area of the iron core to the distance between core pieces, iron core loss versus frequency, and turns ratios. This list is not meant to be exhaustive or limiting.
The E-core 8a contained in the photovoltaic module 2 could be mated with a second E-core, contained within an energy-receiving device 3 in order to facilitate energy transfer.
While the E-core 8a has been described herein as residing inside the photovoltaic module 2a, the scope of the present invention is not to be limited thereto. Other configurations could be envisioned that would not deviate from the spirit and scope of the present invention. For instance, the E-core 8a could be attached to the outside of the photovoltaic module 2a.
A substantially electrically non-conductive medium should be disposed between the photovoltaic module 2a and an energy-receiving device. For the present invention, a substantially electrically non-conductive medium should be selected such that the resistivity of the medium is between 0.01 ohm·cm and 1.0×1017 ohm·cm. Media with conductivity greater than this value may cause interference in energy transfer. Alternatively, the resistivity could be between 1.0 ohm·cm and 1.0×1015 ohm·cm. The substantially electrically non-conductive medium could comprise many different substances including but not limited to glass, non-conductive epoxy, fresh water, sea water, or air.
While certain embodiments of inductive coupling systems have been described herein, other embodiments of inductive coupling systems are within the scope of the present invention.
Capacitive coupling is an alternative method of wireless coupling that could be employed in the present invention. Capacitively coupled systems can be achieved by adjoining a large metal plate with another large metal plate in order to form a capacitor through which high frequency alternating current may flow. Applying a charge to the first plate causes the second plate to effectively act as a load by collecting the energy that is transferred thereto.
Electronic circuitry can be configured in the photovoltaic module to facilitate the conversion of DC to AC in a similar manner as described above. The AC could then couple through a capacitor of sufficiently low impedance from one side to a load to the other side. For capacitively coupled systems, the design elements include the amount of capacitance, the frequency of operation, the relative dimensions of cross sectional area to depth, and the available voltage.
A substantially electrically non-conductive medium should be disposed between the photovoltaic module 2b and the energy-receiving device 3b. For the present invention, a substantially electrically non-conductive medium should be selected such that the resistivity of the medium is between 0.01 ohm·cm and 1.0×1017 ohm·cm. Media with conductivity greater than this value may cause interference in energy transfer. Alternatively, the resistivity could be between 1.0 ohm·cm and 1.0×1015 ohm·cm. The substantially electrically non-conductive medium could comprise many different substances including but not limited to glass, non-conductive epoxy, fresh water, sea water, or air.
Both the capacitive and inductive interfaces described herein are preferably geometrically capable of virtually ideal coupling, as imperfect coupling leads to problematic electromagnetic emissions and wasted energy. In both capacitive and inductive coupling, the area of the interface should be much larger than the distance between them. This is easily achieved in capacitive coupling if, for instance, one meter metal plates are used with a 1 mm separation between encapsulated devices. Inductive coupling depends on the nature of the coupling and the physical implementation of the photovoltaic module. It is likely sufficient if each dimension of an iron core cross section were at least 10 times the distance, such as 10 to 1,000 times the distance, that separates primary and secondary core pieces.
While the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
