Patent Application
20110308576
The invention relates generally to a hybrid system, and more specifically to a hybrid system having a photovoltaic system and a device coupled to a cooling system of the photovoltaic system.
Solar energy is considered as an alternate source of energy relative to conventional forms of energy. Solar energy conversion systems are used to convert solar energy into electrical energy. The solar energy conversion system typically includes photovoltaic modules, photoelectric cells, or solar cells that convert solar energy into electrical energy for immediate use or for storage and subsequent use. Conversion of solar energy into electrical energy includes reception of light, such as sunlight, at a solar cell, absorption of sunlight into the solar cell, generation and separation of positive and negative charges creating a voltage in the solar cell, and collection and transfer of electrical charges through a terminal coupled to the solar cell.
Solar modules are primarily used in residential and commercial areas i.e. in areas served by a grid of an electric utility company. The amount of electrical energy generated by the solar module is directly related to the amount of solar energy the cells within a module absorb, which in turn is impacted by the cell efficiency, surface area of cell coverage, and the intensity or brightness of the sunlight that is incident on the cells. Cost of a photovoltaic module increases with increased surface area coverage by the photovoltaic cells. One approach for reducing the cost associated with photovoltaic modules is via optical concentration techniques. By employing optical concentration, the cell coverage area within the laminate is reduced.
The concentrated photovoltaic modules with higher efficiency photovoltaic cells can achieve higher power densities than non-concentrated silicon modules by focusing sunlight to the photovoltaic modules using optical concentration techniques. In other words, higher concentration of sunlight together with the high efficiency photovoltaic cells leads to higher power density. However, increased solar energy concentration leads to heating of the photovoltaic module, resulting in increase of temperature of the photovoltaic material. The increase in temperature of the photovoltaic module decreases efficiency of the photovoltaic module, leading to reduced performance of the photovoltaic module. As a result, effective power generated from the photovoltaic module is limited.
There is a need for an improved system that overcomes the drawbacks discussed herein.
In accordance with one exemplary embodiment of the present invention, a hybrid system is disclosed. The hybrid system includes a photovoltaic system configured to receive solar energy and convert the solar energy into electrical energy. A cooling system is coupled to the photovoltaic system and configured to circulate a cooling fluid through the cooling system so as to remove heat from the photovoltaic system to cool the photovoltaic system. A first device is coupled to the cooling system and configured to receive the heated cooling fluid from the cooling system. The first device includes a waste heat recovery system configured to generate electric power, a vapor absorption machine configured to cool a second device, a hot water supply unit, a water distillation unit, a water desalination unit, or combinations thereof.
In accordance with another exemplary embodiment of the present invention, a method of operation of the hybrid system is disclosed.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
As discussed herein below with reference to embodiments of
Referring to
The photovoltaic module 16 can achieve higher power densities by focusing sunlight to the photovoltaic module 16 using the solar concentrator 14. In other words, higher concentration of sunlight leads to higher power density. However, increased solar energy concentration leads to heating of the photovoltaic module 16, resulting in increase of temperature of the photovoltaic material. An active cooling system 18 is coupled to the photovoltaic module 16 and configured to circulate a cooling fluid through the cooling system 18 so as to remove heat from the photovoltaic module 16 to cool the photovoltaic module 16. In one embodiment, the cooling fluid includes water. In another embodiment, the cooling fluid includes water mixed with glycol. In certain other embodiments, cooling fluid may include oil or gas.
A first device 20 is coupled to the cooling system 18 via a temperature booster 22, for example, a solar vacuum tube collector. The first device 20 is configured to receive the heated cooling fluid from the cooling system 18 via the temperature booster 22. In one embodiment, the first device 20 includes a waste heat recovery system 24 configured to generate electric power. The waste heat recovery system 24 is configured to remove heat from the heated cooling fluid and generate electric power. In another embodiment, the first device 20 includes a vapor absorption machine 26 configured to remove heat from the cooling fluid and cool a second device 28. The second device 28 may be any application having cooling requirements. In yet another embodiment, the first device 20 includes a hot water supply unit 30. In yet another embodiment, the first device 20 includes a water distillation unit 32 configured to remove heat from the cooling fluid and distill water. In yet another embodiment, the first device 20 includes a water desalination unit 34 configured to remove heat from the cooling fluid and desalinate water. In certain embodiments, the first device 20 includes a combinations thereof of the devices discussed herein.
The temperature booster 22 is configured to substantially increase the temperature of the heated cooling fluid fed from the cooling system 18 to the first device 20 from a first temperature (for example, 70 degrees Celsius) to a second temperature (for example, 110 degrees Celsius). Conventionally, a photovoltaic system is cooled to a relatively low temperature, for example 70 degrees Celsius. However, a cooling fluid at such a lower temperature may not offer other application possibilities. In the illustrated embodiment, the usage of solar booster 22 facilitates to operate the photovoltaic system 12 at low temperature and also boost the temperature of the cooling fluid required for other application possibilities.
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In the illustrated embodiment, the first device 20 includes the waste heat recovery system 24 in accordance with an exemplary embodiment of the present invention. The illustrated waste heat recovery system 24 is an organic rankine cycle system. It should be noted herein that the waste heat recovery system 24 may be alternatively referred to as the organic rankine cycle system. An organic working fluid is circulated through the organic rankine cycle system 24. The organic working fluid may include cyclohexane, cyclopentane, thiophene, ketones, aromatics, or combinations thereof. The organic rankine cycle system 24 includes an evaporator 42 coupled to the temperature booster 22. The evaporator 42 receives heat from the heated cooling fluid and generates an organic working fluid vapor. The organic working fluid vapor is passed through an expander 44 (which in one example comprises a radial type expander) to drive a generator unit 46 for generating electric power. In certain other exemplary embodiments, the expander 44 may be axial type expander, impulse type expander, or high temperature screw type expander. After passing through the expander 44, the organic working fluid vapor at a relatively lower pressure and lower temperature is passed through a condenser 48. The organic working fluid vapor is condensed into a liquid, which is then pumped via a pump 50 to the evaporator 42. The cycle may then be repeated.
Referring to
Also, in the illustrated embodiment, a heat exchanger 58 is disposed between the expander 44 and the condenser 48 exchanger configured to remove heat from the expanded vaporized working fluid and heat water. The hot water may be used for various hot water supply requirements. With reference to embodiments discussed above, the hybrid system 10 has a thermodynamic cycle coupled to a photovoltaic system to extract electric power from thermal energy. Therefore, the power density from the photovoltaic system 12 can be increased substantially by converting the solar energy to electricity using photovoltaic conversion and converting the excess heat to electrical power using a thermodynamic cycle for waste heat recovery instead of dissipating to the environment. The addition of the thermodynamic cycle for waste heat recovery facilitates cooling of the photovoltaic system 12 and generating additional carbon-dioxide-free electricity.
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As discussed above, the power output from the photovoltaic system decreases with increase in temperature. The power output from the waste heat recovery system increases with increase in temperature. The combined power output from the hybrid system increases with respect to temperature. In certain embodiments, the hybrid system may have a power density of 700 watts per meter squared.
Referring to
The embodiments of
The waste heat recovery system 24, the vapor absorption machine 26, the hot water supply unit 30, the water distillation unit 32, and the water desalination unit 34 are selectively activated and deactivated based on a plurality of parameters temperature and pressure of the cooling fluid, solar irradiance on the photovoltaic system 12, efficiency of the waste heat recovery system 24 versus temperature of a working fluid distributed through the waste heat recovery system 24, coefficient of performance of the vapor absorption machine 26 versus temperature of a fluid circulated through the vapor absorption machine 26, cost of electric power, cooling load of the photovoltaic system 12, requirement of hot water through the hot water supply unit 30, cost of thermal energy of the heated cooling fluid, or combinations thereof. A control system (not shown) embedded with a decision making algorithm may be used to determine whether the thermal energy or heat of the cooling fluid may be used for electricity generation, hot water, cooling purpose, or the like. The algorithm is used to determine the optimal use of the thermal energy of the cooling fluid based on the plurality of parameters mentioned above. With reference to the embodiments discussed above, the hybrid system 10 provides substantially higher power density, lower cost per unit of power, multi-power generation i.e. electricity, heat, cooling purposes.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
