WO2007129985A1 - Integrated photovoltaic solar thermal panel - Google Patents

Integrated photovoltaic solar thermal panel Download PDF

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Publication number
WO2007129985A1
WO2007129985A1 PCT/SG2006/000118 SG2006000118W WO2007129985A1 WO 2007129985 A1 WO2007129985 A1 WO 2007129985A1 SG 2006000118 W SG2006000118 W SG 2006000118W WO 2007129985 A1 WO2007129985 A1 WO 2007129985A1
Authority
WO
WIPO (PCT)
Prior art keywords
panel
solar thermal
photovoltaic solar
integrated photovoltaic
laminated
Prior art date
Application number
PCT/SG2006/000118
Other languages
French (fr)
Inventor
Peng Seng Toh
Kian Lip Teo
Original Assignee
Grenzone Pte Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Grenzone Pte Ltd filed Critical Grenzone Pte Ltd
Priority to PCT/SG2006/000118 priority Critical patent/WO2007129985A1/en
Publication of WO2007129985A1 publication Critical patent/WO2007129985A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
    • H02S40/40—Thermal components
    • H02S40/44—Means to utilise heat energy, e.g. hybrid systems producing warm water and electricity at the same time
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S10/00—Solar heat collectors using working fluids
    • F24S10/70—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits
    • F24S10/75—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits with enlarged surfaces, e.g. with protrusions or corrugations
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S25/00—Arrangement of stationary mountings or supports for solar heat collector modules
    • F24S25/60—Fixation means, e.g. fasteners, specially adapted for supporting solar heat collector modules
    • F24S2025/601—Fixation means, e.g. fasteners, specially adapted for supporting solar heat collector modules by bonding, e.g. by using adhesives
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S80/00—Details, accessories or component parts of solar heat collectors not provided for in groups F24S10/00-F24S70/00
    • F24S2080/01—Selection of particular materials
    • F24S2080/015—Plastics
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/60—Thermal-PV hybrids

Definitions

  • the present invention relates to an improvement in solar energy conversion using photovoltaic and solar thermal collection, and in particular to an apparatus in which solar energy is collected by an integrated photovoltaic solar thermal panel. This apparatus reduces the overall cost including production and installation cost.
  • PV Photovoltaic
  • solar thermal collectors are used to harness solar radiation for heating up water or air.
  • PV collects solar energy and converts it to electrical energy.
  • PV panel and PV module are used interchangeably in the disclosure of this invention.
  • the PV panel is heated up when exposed to the sun since only a small fraction of the solar radiation is converted to electricity by photovoltaic effect.
  • the conversion efficiency is inversely proportional to the photovoltaic panel temperature. This is commonly known as the negative temperature coefficient of a photovoltaic panel indicating how much a solar panel power output is reduced with the increase in temperature.
  • PV panel Besides glass, multi-layered laminated polymers (such as TPT and TPE) are widely used as backsheet. Due to their smaller thickness than glass, they dissipated heat better.
  • the perimeter of the PV panel is usually enclosed by a frame of aluminum, steel or molded polymer. The most common one being aluminum profile.
  • the frame serves the purpose of sealing the photovoltaic panel as well as providing mechanical support and protection.
  • the frame also provides means for mounting to other structures in an installation.
  • the PV panel and laminated PV panel has to be differentiated.
  • the PV panel is referred to laminated PV panel with frame and ready to be installed.
  • the laminated PV panel is one without frame.
  • a typical laminated PV panel is a treated multilayer structure with a top transparent cover of glass or clear polymer, follow by a layer of encapsulant such as EVA (Ethylene Vinyl Acetate), interconnection solar cells, another layer of encapsulant (usually EVA) and backsheet of glass or composite laminate.
  • EVA Ethylene Vinyl Acetate
  • the laminated PV panel is an integral unit as the multilayer structure encasing the solar cells are adhered together by the encapsulants and protected by the front cover and backsheet. Electrical connections from the interconnection solar cells are brought outside of the laminated PV panel.
  • the glazed solar thermal collectors are usually arranged within a glass cover with flat plate heat absorber and therefore commonly known as flat plate collector.
  • Metal pipes of copper or aluminum or their alloy are attached to the flat plate heat absorber to transfer the heat to the circulating fluid.
  • the fluid in the solar thermal collector can circulate with or without the aid of pumps or controls. When the fluid is circulating through the pipes without aided by pumps, they are referred to as passive system in which the thermosiphon principle is used. It relies on the natural convection where higher temperature fluid is lighter and rises above cooler fluid.
  • the inlet of the fluid must come from the lower side of the passive flat plate solar thermal collector and exit on the higher end.
  • the flat plate solar thermal collector has to be installed at an inclined angle with cold fluid inlet at the bottom side and heated fluid outlet on the top side.
  • the active solar thermal system uses pumps, sensors and controller to monitor the temperature of the fluid and activate the pumps accordingly to bring the heated fluid from the flat plate solar thermal collector to a heat exchanger or buffer tank.
  • the active system means that the solar thermal collectors need not be installed at an inclined angle but additional energy is required to drive the pumps.
  • PV panel converts solar energy to electricity but also gains heat and increases its temperature; the result is reduction in efficiency as PV panel has negative power temperature coefficient.
  • This invention sets to overcome the above limitations and drawbacks by integrating both PV and solar thermal panels together to improve the overall effectiveness in harnessing solar energy.
  • the invention also discloses the method to overcome the challenges in fabricating the integrated panel with dual purposes.
  • Reaction Injection Molding is known for a very long time for molding of large automobile parts such as bumpers and windscreen.
  • RIM Reaction Injection Molding
  • US4218543 discloses an invention of a process for the production of elastomeric moldings having a compact surface from polyurethane-polyurea elastomers.
  • US2002148496 is an invention relates to solar modules having a transparent polyurethane front side and to a process for producing such modules. This invention is also directed to photovoltaic components for the direct generation of electric power from sunlight. It does not include any form of solar thermal components.
  • the integration of both solar electricity generation by photovoltaic and heat collection by solar thermal absorption reduces production cost and installation cost and thereby making renewable energy means affordable.
  • the solar thermal absorption means transfers the heat gain by the photovoltaic elements to the circulating fluid and thereby reducing the photovoltaic elements temperature with a result of increasing conversion efficiency.
  • the photovoltaic panel serves the purpose of producing electricity as well as radiation heat absorption for the solar thermal collection means.
  • the photovoltaic panel further serves as glazing to the solar thermal collection to reduce convection and conduction loss from the top side.
  • Yet another object of the invention is the use of polymer to mold and encapsulate the integrated photovoltaic and solar thermal components into a single unit.
  • the molded body is preferred to be fabricated by Reaction Injection Molding using polyurethane formulation that can withstand outdoor applications.
  • the molded body ensures that the integrated photovoltaic and solar thermal panel is durable, light weight, strong, sealed, isolated and yet cost effective.
  • the molded body is a good thermal insulation to reduce heat loss from the solar thermal components to the surrounding.
  • a further object is to provide means for accommodating the thermal expansion between the different materials encapsulated within the molded body.
  • Figure 1 Appearance of the integrated photovoltaic solar thermal panel.
  • Figure 2 Exploded view of the integrated photovoltaic solar thermal panel.
  • Figure 3 Heat absorber assembly with parallel pipes and manifolds 24.
  • Figure 4 Heat absorber assembly with meander pipe.
  • Figure 5 Cross sectional view of a typical laminated photovoltaic panel.
  • Figure 6 Cross sectional view of the integrated photovoltaic solar thermal panel.
  • Figure 7 Multiple units of the invention forming an array with separate electrical and solar thermal connections.
  • the preferred embodiment describes an apparatus and the method of fabricating the integrated photovoltaic solar thermal panel 1.
  • the integrated photovoltaic solar thermal panel 1 is an apparatus comprises laminated photovoltaic panel 10, heat absorber assembly 25, polymeric molded body 30 and elastomer layer 31 between the heat absorber assembly 25 and molded body 30. It has two types of connection to the outside world namely electrical and fluid.
  • the electrical connection 22 refers to the output from the photovoltaic cells from the laminated photovoltaic panel 10.
  • the fluid connections have at least one inlet 20 and one outlet 21 for fluid to be circulated through the heat absorber assembly 25.
  • a typical laminated photovoltaic panel 10, as shown in figure 5, typically consists of a piece of glass 13, an encapsulant 14, solar cells 12, electrical connection 15, another encapsulant 14 and a backsheet 11.
  • thermoelectric panel 10 As the glazing for reducing heat loss especially conduction and convection.
  • the laminated PV panel 10 is also the solar radiation thermal collector as only a small amount of the total radiation energy is converted into electricity while majority of the rest is converted to heat. A very small amount is reflected back to the surrounding.
  • Heat absorber assembly 25 consists of at least one heat collection pipe 23 preferably with extended heat absorbing fin 26 to enable collected heat to be transferred to the fluid passing within the pipe.
  • the heat collection pipe 23 and the heat absorbing fin 26 are made of copper or aluminum with excellent heat conducting property.
  • the fluid in the form of water or thermal fluid circulating in the heat collection pipe 23 carries the heat away from the heat absorber assembly 25.
  • the fluid for heat collection can either be water or other liquid. When water is used as the thermal fluid, it is added with antifreeze agent such as ethylene glycol to prevent freezing in the winter.
  • the heat absorbing fin 26 is attached to the backsheet 11 of the laminated PV panel 10 to absorb the heat away from the laminated PV panel 10. In the case where heat absorbing fin 26 is not in use, the heat collection pipe 23 can also be attached directly to the backsheet 11 of the laminated PV panel 10 with a reduced effect of heat transfer due to the reduction of contact area.
  • the body is one integral element formed by molding or casting in which Reaction Injection Molding (RIM) method is preferred to form a structurally strong, weather resistant and good thermal insulation polyurethane molded body 30 that encapsulates the laminated PV panel 10 with the tightly coupled heat absorber assembly 25.
  • RIM Reaction Injection Molding
  • the surface finishing of using RIM can be controlled to achieve water resistant and of the desired aesthetic.
  • the size of the present invention varies between 0.5 sq m to 2 sq m with typical size of about 1.2 to 1.5 sq. m. This means that RIM is highly cost effective to carry out the molding process to form the molded body 30.
  • the RIM molded body 30 forms the frame of the laminated PV panel 10 that enhances its resistant to moisture and water.
  • the molded body 30 also forms the thermal and electrical insulation to the laminated PV panel 10 and the heat absorber assembly 25. Mounting holes and brackets can be easily incorporated into the molded body 30 to facilitate installation.
  • the molded body 30 is sufficiently elastics to cater for the differences in thermal expansion between the different materials encapsulated within.
  • the top cover of the laminated PV panel 10 is usually glass with lower thermal expansion.
  • the relative change in size due to temperature change can be accommodated by the elasticity of the molded body 30 and therefore not inducing mechanical stress and deformation.
  • Commercially polyurethane formulations are available to produce light weight, durable and strong molded body 30 for extended period of outdoor use.
  • the change in dimension due to thermal expansion of different materials can be significant whereby the molded body 30 cannot accommodate.
  • the large difference in thermal expansion is expected between the molded body 30 and the heat absorber assembly 25 of copper, copper alloy, aluminum or aluminum alloy.
  • the typical coefficient of thermal expansion of copper and brass pipes is in the range of 0.017 to 0.019 mm per m per degree C.
  • the typical coefficient of thermal expansion of commercially available polyurethane is about 0.1mm per m per degree C.
  • a layer of elastomer material 31 that wraps around the pipes 23 of the heat absorber assembly 25 is used to absorb the relative change in dimension with respect to the molded body 30.
  • the elastomer material 31 is preferably precut into size and shape sufficiently covering the heat absorber assembly 25.
  • a wide range of elastomer precut sheet 31 such as rubber, silicone, EPDM, foamed PU, or fibrous matt can be used to serve the purpose of accommodating the thermal expansion.
  • the most cost effective and light weight elastomer precut sheet 31 being fibrous rockwool matt of thickness in the range of 5 to 10mm.
  • the fibrous rockwool matt has sufficient density that will not be overly penetrated by the reaction injection polyurethane during RIM process.
  • the fibrous rockwool matt is also a good thermal insulator.
  • the elastomer precut sheet 31 forms a wrapping around the heat absorber assembly 25 serving as a cushion with respect to the molded body 30.
  • the electrical connections from the laminated PV panel 10 are extended by wires 22 to the exterior of the molded body 30 for ease of electrical interconnection.
  • the fluid inlet 20 and outlet 21 connections can be extended outside the molded body 30 by flexible pipe 45 for ease of pipes connection and therefore plumbing installation.
  • the integrated photovoltaic solar thermal panel 1 can be used singly or plurality interconnected to form a large array of similar units. These units are supported by mounting structures 41, hold in place by mounting clips 42. Fluid is brought to the array by inlet pipe 43, and distributed to various photovoltaic solar thermal panels 1 via flexible pipe 45 and fluid inlet 20. After absorbing the heat from the laminated PV panel 10, the fluid flows out through the fluid outlet 21, flexible pipe 45 and subsequently the outlet pipe 44. Whether it is used singly or plurality, the electrical connections are independent from the fluid connections and therefore allows for greater flexibility to achieve higher efficiency.
  • the orientation of the integrated photovoltaic solar thermal panel 1 is such that it is to maximize solar gain where most solar radiation is received.
  • the integrated photovoltaic solar thermal panel 1 either singly or plurality can be mounted on solar tracker to track the sun for maximizing energy output of both electricity and heat collection.
  • a typical mold used by the RIM process has a bottom mold, known as cavity, and a top mold also known as core.
  • the top cover of the laminated photovoltaic panel 10 is faced downward exposing its backsheet 11 for ease of attachment of the heat absorber assembly 25.
  • the laminated photovoltaic panel 10 together with the attached heat absorber assembly 25 is placed inside the bottom mold.
  • the heat absorber assembly 25 is held in place on the laminated photovoltaic panel 10 by applying elastic adhesive at certain location but not too much to cause poor thermal conduction. All accessories such as electrical wiring 22 are pre-assembled and placed in the bottom mold.
  • a layer of elastomer sheet 31 cut to the size and shape is placed onto the heat absorber assembly 25.
  • the elastomer sheet 31 is held in place with respect to the heat absorber assembly 25 by double sided tape or adhesive.
  • the elastomer sheet 31 is to wrap around the heat pipes 23 of the heat absorber assembly 25 before closing the top mold.
  • the well mixed two components polyurethane is then injected through the bottom mold when the top mold is securely closed.
  • the RIM process is an established industrial process and will not be further elaborated in this invention.

Abstract

The integrated photovoltaic solar thermal panel converts solar radiation to electricity and thermal collection within a single unit. This results in high conversion efficiency as both electricity and heat are produced. The overall energy conversion cost is low due to lower production and installation cost. The integrated photovoltaic solar thermal panel can be used individually or as an array consisting of multiple units to increase the overall energy generation. The present invention also solves the problems of high temperature associated with photovoltaic panel and the thermal insulation for solar thermal system.

Description

Integrated Photovoltaic Solar Thermal Panel
BACKGROUND OF THE INVENTION
Field of Invention
The present invention relates to an improvement in solar energy conversion using photovoltaic and solar thermal collection, and in particular to an apparatus in which solar energy is collected by an integrated photovoltaic solar thermal panel. This apparatus reduces the overall cost including production and installation cost.
DESCRIPTION
Conventionally, converting solar energy into electricity and solar heat collection are carried by two separate apparatus. Photovoltaic, or PV in short, is used to convert solar radiation into electricity. On the other hand, solar thermal collectors are used to harness solar radiation for heating up water or air. These two types of apparatus, namely PV and solar thermal collector, are usually installed independently, and therefore occupying larger area and involving double installation effort.
PV collects solar energy and converts it to electrical energy. PV panel and PV module are used interchangeably in the disclosure of this invention. The PV panel is heated up when exposed to the sun since only a small fraction of the solar radiation is converted to electricity by photovoltaic effect. When the PV panel is heated up, its temperature rises and the conversion efficiency declines. In other words, the conversion efficiency is inversely proportional to the photovoltaic panel temperature. This is commonly known as the negative temperature coefficient of a photovoltaic panel indicating how much a solar panel power output is reduced with the increase in temperature.
In order to maximize the output from the photovoltaic panel, it is important to reduce the increase in temperature during operation. Presently there is no active means of reducing the PV panel temperature by removing the heat away. Most of the present PV installation relies on natural air movement to dissipate heat. The bottom side of the PV panel is hotter than the front side and therefore the removable of heat from the bottom side is more effective. The backsheet which forms the bottom side of a PV panel besides having the role of support, isolation and protection, its heat dissipation factor needs to be considered too. Glass backsheet is effective in support, isolation and protection, it however does not have good heat conductivity and therefore the heat absorb by the solar cells are largely trapped within the laminated PV panel. Besides glass, multi-layered laminated polymers (such as TPT and TPE) are widely used as backsheet. Due to their smaller thickness than glass, they dissipated heat better. The perimeter of the PV panel is usually enclosed by a frame of aluminum, steel or molded polymer. The most common one being aluminum profile. The frame serves the purpose of sealing the photovoltaic panel as well as providing mechanical support and protection. The frame also provides means for mounting to other structures in an installation. For the sake of clarity, the PV panel and laminated PV panel has to be differentiated. Hereinafter the PV panel is referred to laminated PV panel with frame and ready to be installed. The laminated PV panel is one without frame. A typical laminated PV panel is a treated multilayer structure with a top transparent cover of glass or clear polymer, follow by a layer of encapsulant such as EVA (Ethylene Vinyl Acetate), interconnection solar cells, another layer of encapsulant (usually EVA) and backsheet of glass or composite laminate. The laminated PV panel is an integral unit as the multilayer structure encasing the solar cells are adhered together by the encapsulants and protected by the front cover and backsheet. Electrical connections from the interconnection solar cells are brought outside of the laminated PV panel.
There are a number of different solar thermal collectors available commercially. They are broadly categorized into unglazed, glazed and evacuated tubes. The glazed solar thermal collectors are usually arranged within a glass cover with flat plate heat absorber and therefore commonly known as flat plate collector. Metal pipes of copper or aluminum or their alloy are attached to the flat plate heat absorber to transfer the heat to the circulating fluid. The fluid in the solar thermal collector can circulate with or without the aid of pumps or controls. When the fluid is circulating through the pipes without aided by pumps, they are referred to as passive system in which the thermosiphon principle is used. It relies on the natural convection where higher temperature fluid is lighter and rises above cooler fluid. The inlet of the fluid must come from the lower side of the passive flat plate solar thermal collector and exit on the higher end. In order for the thermosiphon principle to take effect, the flat plate solar thermal collector has to be installed at an inclined angle with cold fluid inlet at the bottom side and heated fluid outlet on the top side.
The active solar thermal system uses pumps, sensors and controller to monitor the temperature of the fluid and activate the pumps accordingly to bring the heated fluid from the flat plate solar thermal collector to a heat exchanger or buffer tank. The active system means that the solar thermal collectors need not be installed at an inclined angle but additional energy is required to drive the pumps.
There are many drawbacks when separate PV panel and solar thermal collector are purchased and installed as in the convention approach. Firstly, installation has to be carried out twice and occupy large area.
Secondly, PV panel converts solar energy to electricity but also gains heat and increases its temperature; the result is reduction in efficiency as PV panel has negative power temperature coefficient.
Thirdly, conventional solar thermal collector is heavy and expensive. Installation is difficult and cost is high.
This invention sets to overcome the above limitations and drawbacks by integrating both PV and solar thermal panels together to improve the overall effectiveness in harnessing solar energy. The invention also discloses the method to overcome the challenges in fabricating the integrated panel with dual purposes. Reaction Injection Molding (RIM) is known for a very long time for molding of large automobile parts such as bumpers and windscreen. For example, "Reaction Injection Molding in the Automotive Industry", Journal of Cell. Plastics, Vol. II. No. 2, 1975; Knipp: "Plastics for Automobile Safety Bumpers", Journal of Cell. Plastics, No. 2, 1973.
US4218543 discloses an invention of a process for the production of elastomeric moldings having a compact surface from polyurethane-polyurea elastomers.
US 4830038 and US5008062 disclose method of fabricating photovoltaic module by using reaction injection molding. These two interrelated patents focus on photovoltaic for electricity generation only.
US2002148496 is an invention relates to solar modules having a transparent polyurethane front side and to a process for producing such modules. This invention is also directed to photovoltaic components for the direct generation of electric power from sunlight. It does not include any form of solar thermal components.
SUMMARY OF THE INVENTION
It is an object of the present invention to integrate both solar electricity generation and solar thermal collection into a single unit to optimize overall solar energy conversion. The integration of both solar electricity generation by photovoltaic and heat collection by solar thermal absorption reduces production cost and installation cost and thereby making renewable energy means affordable.
The solar thermal absorption means transfers the heat gain by the photovoltaic elements to the circulating fluid and thereby reducing the photovoltaic elements temperature with a result of increasing conversion efficiency. The photovoltaic panel serves the purpose of producing electricity as well as radiation heat absorption for the solar thermal collection means. The photovoltaic panel further serves as glazing to the solar thermal collection to reduce convection and conduction loss from the top side.
Yet another object of the invention is the use of polymer to mold and encapsulate the integrated photovoltaic and solar thermal components into a single unit. The molded body is preferred to be fabricated by Reaction Injection Molding using polyurethane formulation that can withstand outdoor applications. The molded body ensures that the integrated photovoltaic and solar thermal panel is durable, light weight, strong, sealed, isolated and yet cost effective. The molded body is a good thermal insulation to reduce heat loss from the solar thermal components to the surrounding. A further object is to provide means for accommodating the thermal expansion between the different materials encapsulated within the molded body. BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 Appearance of the integrated photovoltaic solar thermal panel. Figure 2 Exploded view of the integrated photovoltaic solar thermal panel. Figure 3 Heat absorber assembly with parallel pipes and manifolds 24. Figure 4 Heat absorber assembly with meander pipe. Figure 5 Cross sectional view of a typical laminated photovoltaic panel. Figure 6 Cross sectional view of the integrated photovoltaic solar thermal panel.
Figure 7 Multiple units of the invention forming an array with separate electrical and solar thermal connections.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiment describes an apparatus and the method of fabricating the integrated photovoltaic solar thermal panel 1.
The integrated photovoltaic solar thermal panel 1 is an apparatus comprises laminated photovoltaic panel 10, heat absorber assembly 25, polymeric molded body 30 and elastomer layer 31 between the heat absorber assembly 25 and molded body 30. It has two types of connection to the outside world namely electrical and fluid. The electrical connection 22 refers to the output from the photovoltaic cells from the laminated photovoltaic panel 10. The fluid connections have at least one inlet 20 and one outlet 21 for fluid to be circulated through the heat absorber assembly 25.
A typical laminated photovoltaic panel 10, as shown in figure 5, typically consists of a piece of glass 13, an encapsulant 14, solar cells 12, electrical connection 15, another encapsulant 14 and a backsheet 11.
In a conventional flat plate solar hot water unit, glazing make of large panel of glass is used to reduce heat loss from the absorber to the ambient. The glazing glass is heavy and adds cost to the conventional flat plate solar hot water unit. The present embodiment uses the laminated PV panel 10 as the glazing for reducing heat loss especially conduction and convection. The laminated PV panel 10 is also the solar radiation thermal collector as only a small amount of the total radiation energy is converted into electricity while majority of the rest is converted to heat. A very small amount is reflected back to the surrounding. Heat absorber assembly 25 consists of at least one heat collection pipe 23 preferably with extended heat absorbing fin 26 to enable collected heat to be transferred to the fluid passing within the pipe. The heat collection pipe 23 and the heat absorbing fin 26 are made of copper or aluminum with excellent heat conducting property. The fluid in the form of water or thermal fluid circulating in the heat collection pipe 23 carries the heat away from the heat absorber assembly 25. The fluid for heat collection can either be water or other liquid. When water is used as the thermal fluid, it is added with antifreeze agent such as ethylene glycol to prevent freezing in the winter. The heat absorbing fin 26 is attached to the backsheet 11 of the laminated PV panel 10 to absorb the heat away from the laminated PV panel 10. In the case where heat absorbing fin 26 is not in use, the heat collection pipe 23 can also be attached directly to the backsheet 11 of the laminated PV panel 10 with a reduced effect of heat transfer due to the reduction of contact area.
The body is one integral element formed by molding or casting in which Reaction Injection Molding (RIM) method is preferred to form a structurally strong, weather resistant and good thermal insulation polyurethane molded body 30 that encapsulates the laminated PV panel 10 with the tightly coupled heat absorber assembly 25. RIM is well known in the industry for making large automobile parts such as bumper, door lining, sun roof and a range of other complex components. The surface finishing of using RIM can be controlled to achieve water resistant and of the desired aesthetic. The size of the present invention varies between 0.5 sq m to 2 sq m with typical size of about 1.2 to 1.5 sq. m. This means that RIM is highly cost effective to carry out the molding process to form the molded body 30.
The RIM molded body 30 forms the frame of the laminated PV panel 10 that enhances its resistant to moisture and water. The molded body 30 also forms the thermal and electrical insulation to the laminated PV panel 10 and the heat absorber assembly 25. Mounting holes and brackets can be easily incorporated into the molded body 30 to facilitate installation. With suitable selection of polyurethane formulation, the molded body 30 is sufficiently elastics to cater for the differences in thermal expansion between the different materials encapsulated within. For example, the top cover of the laminated PV panel 10 is usually glass with lower thermal expansion. For rather small size integrated photovoltaic solar thermal panel 1, the relative change in size due to temperature change can be accommodated by the elasticity of the molded body 30 and therefore not inducing mechanical stress and deformation. Commercially polyurethane formulations are available to produce light weight, durable and strong molded body 30 for extended period of outdoor use.
In the case of large panel with linear dimension of more than 0.5m, the change in dimension due to thermal expansion of different materials can be significant whereby the molded body 30 cannot accommodate. The large difference in thermal expansion is expected between the molded body 30 and the heat absorber assembly 25 of copper, copper alloy, aluminum or aluminum alloy. The typical coefficient of thermal expansion of copper and brass pipes is in the range of 0.017 to 0.019 mm per m per degree C. The typical coefficient of thermal expansion of commercially available polyurethane is about 0.1mm per m per degree C. With a 50 degree C temperature change, a im length pipe and the enclosed polyurethane molded body 30 can experience dimension difference of more than 3mm. This change in dimension has to be accommodated which is insufficient by the polyurethane molded body 30 alone. A layer of elastomer material 31 that wraps around the pipes 23 of the heat absorber assembly 25 is used to absorb the relative change in dimension with respect to the molded body 30. The elastomer material 31 is preferably precut into size and shape sufficiently covering the heat absorber assembly 25. A wide range of elastomer precut sheet 31 such as rubber, silicone, EPDM, foamed PU, or fibrous matt can be used to serve the purpose of accommodating the thermal expansion. The most cost effective and light weight elastomer precut sheet 31 being fibrous rockwool matt of thickness in the range of 5 to 10mm. The fibrous rockwool matt has sufficient density that will not be overly penetrated by the reaction injection polyurethane during RIM process. The fibrous rockwool matt is also a good thermal insulator. After the RIM process, the elastomer precut sheet 31 forms a wrapping around the heat absorber assembly 25 serving as a cushion with respect to the molded body 30.
The electrical connections from the laminated PV panel 10 are extended by wires 22 to the exterior of the molded body 30 for ease of electrical interconnection. The fluid inlet 20 and outlet 21 connections can be extended outside the molded body 30 by flexible pipe 45 for ease of pipes connection and therefore plumbing installation.
The integrated photovoltaic solar thermal panel 1 can be used singly or plurality interconnected to form a large array of similar units. These units are supported by mounting structures 41, hold in place by mounting clips 42. Fluid is brought to the array by inlet pipe 43, and distributed to various photovoltaic solar thermal panels 1 via flexible pipe 45 and fluid inlet 20. After absorbing the heat from the laminated PV panel 10, the fluid flows out through the fluid outlet 21, flexible pipe 45 and subsequently the outlet pipe 44. Whether it is used singly or plurality, the electrical connections are independent from the fluid connections and therefore allows for greater flexibility to achieve higher efficiency.
The orientation of the integrated photovoltaic solar thermal panel 1 is such that it is to maximize solar gain where most solar radiation is received. Not limited to roof installation, the integrated photovoltaic solar thermal panel 1 either singly or plurality can be mounted on solar tracker to track the sun for maximizing energy output of both electricity and heat collection. A typical mold used by the RIM process has a bottom mold, known as cavity, and a top mold also known as core. In order to facilitate the assembly and molding process, the top cover of the laminated photovoltaic panel 10 is faced downward exposing its backsheet 11 for ease of attachment of the heat absorber assembly 25.
Assembly of the photovoltaic cell to form a laminated photovoltaic panel 10 is a well established process and hence will not be described in the scope of this invention. The laminated photovoltaic panel 10 together with the attached heat absorber assembly 25 is placed inside the bottom mold. The heat absorber assembly 25 is held in place on the laminated photovoltaic panel 10 by applying elastic adhesive at certain location but not too much to cause poor thermal conduction. All accessories such as electrical wiring 22 are pre-assembled and placed in the bottom mold. A layer of elastomer sheet 31 cut to the size and shape is placed onto the heat absorber assembly 25. The elastomer sheet 31 is held in place with respect to the heat absorber assembly 25 by double sided tape or adhesive. The elastomer sheet 31 is to wrap around the heat pipes 23 of the heat absorber assembly 25 before closing the top mold. The well mixed two components polyurethane is then injected through the bottom mold when the top mold is securely closed. The RIM process is an established industrial process and will not be further elaborated in this invention.

Claims

Integrated Photovoltaic Solar Thermal PanelClaims
1. An integrated photovoltaic solar thermal panel comprises of a heat absorber assembly attached to the bottom side of a laminated photovoltaic panel and encapsulated by a molded body on the perimeter of the photovoltaic panel and completely on the heat absorber assembly; a layer of elastomer wraps around the heat absorber assembly between the molded body; electrical connections from the laminated photovoltaic panel and the fluid inlet and outlet from the heat absorber assembly are provided on the molded body;
2. The integrated photovoltaic solar thermal panel as claimed in claim 1, the heat absorber assembly comprises of at least one pipe with optimum contact with the bottom side of the laminated photovoltaic panel; The pipes have at least one inlet and one outlet to allow fluid to be circulated through the pipes.
3. The integrated photovoltaic solar thermal panel as claimed in claim 2, the pipes are arranged largely in parallel connected by manifolds on both ends for fluid inlet and outlet;
4. The integrated photovoltaic solar thermal panel as claimed in claim 2, the pipes are arranged in a meander form with multiple bends with one inlet and one outlet on both ends to allow fluid to flow through.
5. The integrated photovoltaic solar thermal panel as claimed in claim 2, the pipes have extended surface in the form of welded fins to form large contact with the bottom side of the photovoltaic panel.
6. The integrated photovoltaic solar thermal panel as claimed in claim 1, the laminated photovoltaic panel has a transparent top cover and a laminated composite polymer backsheet on the bottom side.
7. The integrated photovoltaic solar thermal panel as claimed in claim 1, wherein the molded body encapsulates the perimeter of the laminated photovoltaic panel exposing the transparent top cover and encapsulates the heat absorber assembly forming the underside of the integrated photovoltaic solar thermal panel.
8. The integrated photovoltaic solar thermal panel as claimed in claim 7, the molded body is polyurethane polymer.
9. The integrated photovoltaic solar thermal panel as claimed in claim 8, the polyurethane molded body is fabricated by the Reaction Injection Molding method.
PCT/SG2006/000118 2006-05-08 2006-05-08 Integrated photovoltaic solar thermal panel WO2007129985A1 (en)

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ITMI20101708A1 (en) * 2010-09-20 2012-03-21 Enecom Italia S R L SOLAR MODULE FOR THE CONVERSION OF SOLAR RADIATION IN ELECTRIC AND THERMAL ENERGY
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CN112378124A (en) * 2020-11-04 2021-02-19 上海交通大学 Solar photovoltaic/photothermal heat collection/evaporator with double-effect cogeneration

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