US-12620932-B2 - Photovoltaics panel, photovoltaics system and evaporating system for photovoltaics system

US12620932B2US 12620932 B2US12620932 B2US 12620932B2US-12620932-B2

Abstract

A photovoltaics (PV) panel includes a PV module ( 102, 202 ) with a front face ( 102 a, 202 a ) for exposure to sunlight and absorbing solar energy for conversion to electric energy and a back face opposite to the front face, and an evaporator ( 104, 204, 312 ) engaged with the back face of the PV module, an upper end ( 106, 206 ) of the evaporator being in close proximity to or in contact with a water source for absorbing the water by capillary action, the evaporator being of a structure allowing the water to move through, and the PV module being in a heat-transferrable relationship with the water moving through the evaporator.

Inventors

Wei Wu
Fuxiang LI

Assignees

CITY UNIVERSITY OF HONG KONG

Dates

Publication Date: 20260505
Application Date: 20240517

Claims (20)

1 . A photovoltaics (PV) panel including: a PV module with a front face for exposure to sunlight and absorbing solar energy for conversion to electric energy and a back face opposite to said front face, and an evaporator engaged with said back face of said PV module, wherein a first end of said evaporator is adapted to be in close proximity to or in contact with a source of a cooling medium for absorbing said cooling medium by capillary action, wherein said evaporator is of a structure allowing said cooling medium to move through, wherein said PV module is adapted to be in a heat-transferrable relationship with said cooling medium moving through said evaporator, wherein said evaporator is of a porous structure allowing said cooling medium absorbed by said evaporator to move from said first end of said evaporator to an opposite second end of said evaporator and to exit said evaporator from said second end, wherein said evaporator is configured to permit at least a portion of said cooling medium to evaporate to an environment as said cooling medium is absorbed by said evaporator, and wherein said environment is outside of said photovoltaics PV panel.
2 . The PV panel of claim 1 , wherein said evaporator is made at least of a cooling medium absorbent material.
3 . The PV panel of claim 2 , wherein said evaporator is engaged with said back face of said PV module via a thermally-conductive layer.
4 . The PV panel of claim 3 , wherein said thermally-conductive layer is made at least of an adhesive thermally-conductive material.
5 . The PV panel of claim 1 , wherein said second end of said evaporator is adapted to be in close proximity to or in contact with a lower container for collecting said cooling medium exiting said evaporator from said second end.
6 . A photovoltaics (PV) system including a PV panel according to claim 1 .
7 . The PV system of claim 6 , wherein said PV module is inclined relative to the horizontal, and wherein said evaporator is of a porous structure allowing at least a portion of said cooling medium absorbed by said evaporator to move under gravity from said first end to an opposite second end which is lower than said first end to exit said evaporator.
8 . The PV system of claim 6 , wherein said evaporator is engaged with said back face of said PV module via a thermally-conductive layer.
9 . The PV system of claim 8 , wherein said thermally-conductive layer is made at least of an adhesive thermally-conductive material.
10 . A photovoltaics (PV) system including a PV panel including: a PV module with a front face for exposure to sunlight and absorbing solar energy for conversion to electric energy and a back face opposite to said front face, and an evaporator engaged with said back face of said PV module, wherein a first end of said evaporator is adapted to be in close proximity to or in contact with a source of a cooling medium for absorbing said cooling medium by capillary action, wherein said evaporator is of a structure allowing said cooling medium to move through, and wherein said PV module is adapted to be in a heat-transferrable relationship with said cooling medium moving through said evaporator, said PV system further including: a pump operable to pump said cooling medium to an upper container to be absorbed by said evaporator, an irradiance sensor, a liquid-level sensor, and a control system, wherein said control system is adapted to: stop operation of said pump when solar irradiance on said PV panel as measured by said irradiance sensor is below a threshold level, activate operation of said pump for a first predetermined period of time to pump said cooling medium to said upper container when solar irradiance on said PV panel as measured by said irradiance sensor is above said threshold level, and activate operation of said pump for a second predetermined period of time to pump said cooling medium to said upper container when solar irradiance on said PV panel as measured by said irradiance sensor is above said threshold level and said cooling medium in said upper container as sensed by said liquid-level sensor is below a pre-set level.
11 . The PV system of claim 7 , further including a path allowing said cooling medium exiting said evaporator from said second end of said evaporator to move to a pump.
12 . The PV system of claim 11 , wherein said second end of said evaporator is in close proximity to or in contact with a lower container for collecting said cooling medium exiting said evaporator from said second end.
13 . An evaporating system for a photovoltaics (PV) system, including: an evaporator engageable with a back face of a PV module, and an upper container for a cooling medium, wherein a first end of said evaporator extends in close proximity to or at least partly into said upper container and is adapted to absorb said cooling medium in said upper container by capillary action, wherein said evaporator is of a structure allowing said cooling medium to move through, wherein, when said evaporator is engaged with said PV panel, said PV module is adapted to be in a heat-transferrable relationship with said cooling medium moving through said evaporator, and wherein said evaporator includes a face facing away from said front face of said PV module allowing at least a portion of said cooling medium absorbed by said evaporator to evaporate to an environment outside of said PV system.
14 . The evaporating system of claim 13 , wherein said evaporator is made at least of a cooling medium absorbent material.
15 . The evaporating system of claim 13 , wherein said evaporator is of a porous structure allowing at least a portion of said cooling medium absorbed by said evaporator to move under gravity from said first end to an opposite second end which is lower than said first end to exit said evaporator.
16 . The evaporator system of claim 15 , wherein said second end of said evaporator is in close proximity to or in contact with a lower container for collecting said cooling medium exiting said evaporator from said second end.
17 . The evaporating system of claim 13 , wherein said evaporator is engageable with said back face of said PV module via a thermally-conductive layer.
18 . The evaporating system of claim 17 , wherein said thermally-conductive layer is made at least of an adhesive thermally-conductive material.
19 . The evaporating system of claim 13 , further including a pump operable to pump said cooling medium to said upper container to be absorbed by said cooling member.
20 . An evaporating system for a photovoltaics (PV) system, including: an evaporator engageable with a back face of a PV module, and an upper container for a cooling medium, wherein a first end of said evaporator extends in close proximity to or at least partly into said upper container and is adapted to absorb said cooling medium in said upper container by capillary action, wherein said evaporator is of a structure allowing said cooling medium to move through, and wherein, when said evaporator is engaged with said PV panel, said PV module is adapted to be in a heat-transferrable relationship with said cooling medium moving through said evaporator, said evaporating system further including: a pump operable to pump said cooling medium to said upper container to be absorbed by said cooling member, an irradiance sensor, a liquid-level sensor, and a control system wherein said control system is adapted to: stop operation of said pump when solar irradiance on said PV panel as measured by said irradiance sensor is below a threshold level, activate operation of said pump for a first predetermined period of time to pump said cooling medium to said upper container when solar irradiance on said PV panel as measured by said irradiance sensor is above said threshold level, and activate operation of said pump for a second predetermined period of time to pump said cooling medium to said upper container when solar irradiance on said PV panel as measured by said irradiance sensor is above said threshold level and said cooling medium in said upper container as sensed by said liquid-level sensor is below a pre-set level.

Description

This application claims priority from U.S. Patent Application No. 63/508,481 filed on 15 Jun. 2023, the content of which being incorporated herein by reference in its entirety as if fully set forth herein. FIELD OF THE INVENTION This invention relates to a photovoltaics (PV) panel, a PV system with such a PV panel, and an evaporating system for a PV system. BACKGROUND OF THE INVENTION Solar energy is essential for achieving global energy sustainability, given its vast abundance and free availability. Photovoltaics (PV) can convert irradiance into usable electricity with zero carbon emission and thus holds great promise to harness solar energy. In recent decades, efficiency improvement and cost decline have enabled the commercialization of crystalline silicon (c-Si) PV technology. The cumulative capacity of PV installation is projected to increase from 700 GW in 2020 to 22 TW by the end of 2050. Despite the promising prospect, c-Si PV can only utilize a limited fraction (<25.6%) of the incident solar spectrum, with the rest wasted as heat. The resulting high temperature shortens the lifetime and decreases the power conversion efficiency of such panels, and may even cause fire hazards. The efficiency of typical c-Si panels decreases by about 5.0% and their aging rate doubles with every 10° C. increase in operating temperature. As the c-Si technology approaches the theoretical limit while the next-generation technologies (e.g., perovskite) are far from mature commercialization, improving the light-to-electricity efficiency via material progress becomes increasingly difficult. It is time to regulate PV temperature with thermal management technologies, thus enhancing efficiency and reliability. Ideal PV thermal management can reliably create the maximal cooling effect with the least cost. Existing PV thermal management technologies are classified into active (mechanically driven) and passive (naturally driven), depending on the energy requirement. Active technologies typically include forced circulation of fluids (e.g., air or water), requiring fan and pump powers. For example, forced ventilation on a hot PV surface or a backside heat sink can reject heat by airflow. However, this scheme was not widespread due to low cooling efficiency, high fan power, and additional air duct structures. Comparatively, water has a larger heat capacity and thermal conductivity and can absorb much heat during evaporation. These features enable advanced water spray, water veils, and backside direct-contact water to achieve high heat-removal efficiency. However, these processes can consume large amounts of water due to the fluidity of water and inefficient heat transfer design. The overall cost-effectiveness remains low with complex system configuration and massive pump power. On the other hand, passive technologies that rely on spontaneous processes provide attractive solutions to this problem. The finned structure is a typical example of enhancing heat convection at the cost of system compactness, and its heat removal efficiency depends on wind velocity. Radiative cooling (RC) is another method for PV cooling by rejecting the waste heat directly to the universe through the atmosphere transparency window from 8 to 13 μm. However, commercial PV glass is already a high-emissivity surface that limits the cooling efficiency of RC. A recent outdoor experiment indicated that RC only contributes to a temperature reduction of 3.6° C. in existing mainstream c-Si cells. In addition, phase change material (PCM) that can maintain a stable temperature during phase transition can be attached to the PV back for heat extraction. Although a well-developed PV-PCM system can achieve a temperature reduction of 7-21° C., low thermal conductivity, incongruent melting, and cyclic degradation are long-standing problems. Recently, passive evaporative cooling using a backside evaporator under the PV has received significant research interest. For example, a burlap-based evaporative cooler with a gravity-assisted water supply can enable a temperature drop of 15-20° C. A more recent biomimetic cooler was proposed based on bamboo bundles and packed hydrogels. In the lab-scale proof-of-concept prototype, the water for evaporation is supplied into the evaporator via capillarity and transpiration effects, with a temperature reduction of about 26° C. Hygroscopic sorbents (e.g., hygroscopic hydrogels and metal-organic frameworks) are another passive scheme option. Without using an additional water supply, this technology provides evaporative cooling by a sorption-evaporation cycle that removes waste heat via evaporation under the sun and recovers the moisture at night. These reported pilot cooling prototypes exhibited impressive temperature reduction (6-15° C.) when using fully charged sorbent layers. However, such systems are susceptible to dehydrate in the actual environment due to the slow sorption kinetics and cyclic degradation. In summary, active thermal mana