RO133284A0 - Solar concentrator with multiple focal points and stirling motor - Google Patents

Abstract

The invention relates to a solar concentrator with multiple focal points and a Stirling motor belonging to the systems of energy production from alternative renewable sources, which are in accordance with the environmental standards. According to the invention, the concentrator comprises an automated solar tracking support (1) on which there are several solar concentrators (2) which focus the solar energy on some thermal receivers (41), a system (5) for mixing, distributing, entraining and controlling the flow rate of a gaseous thermal medium (43) coupled to the thermal receivers (41), a Stirling motor (31) coupled with an electric generator (33) supplied by means of an automatic system (6) for mixing and proportionally controlling the flow rate of a hydrogen-enriched gaseous fuel, a heat exchanger (7) connected within the common cooling system of the Stirling motor (31) and of the thermoelectric elements of an economizer (35), an inverter (8) coupled with an electric generator (33), some secondary batteries (9) and an electrolyser (10), the solar concentrators (2) being grouped matricially on n rows and k columns, resulting in a system with n*k multiple focal points with n*k thermal receivers (41) which are interconnected parallely by means of a distribution system (54) and coupled to a combustion chamber (32) of the Stirling motor (31), and each receiver (41), independently connected and parallely connected with the other receivers (41), is provided with some valves (53) for isolating the flow rate of thermal medium (43) which can be independently actuated, the thermal energy resulting by the conversion of the concentrated solar energy (44) being stored in a gaseous thermal medium (43) which is transferred by the thermally insulated distribution system (54), under the pressure ensured by a compressor (51), into the combustion chamber (32) of the Stirling motor (31) and used directly in the combustion process of the Stirling motor (31).

Description

Description of the invention

a) title: Solar concentrator with multiple focus and Stirling engine

b) specifying the technical field in which the invention can be used;

BACKGROUND OF THE INVENTION The present invention relates to a hybrid assembly of cogeneration of electric and thermal energy from mixed sources, consisting of a system of solar concentrators (2) with multiple foci, receiving elements (4) and transfer of thermal energy to a coupled Stirling motor (31) with an electric generator (33). The assembly is mounted on a tracking system (1), with two axes, which allows solar tracking throughout the day.

As the mixed energy sources used include in addition to solar energy, biogas or natural gas, the technical scope of the invention can be to provide electrical and thermal energy especially in biogas producing farms but also in homes, SMEs, etc.

c) indicating the prior state of the art and indicating the documents underlying it;

Finding the best solar concentrators for the use of concentrated solar energy in various applications is a long studied field. One of the applications is the Stirling solar-motor concentrator systems. Most of them use parabolic mirrors for the concentration of solar radiation, having a Stirling engine [1-4]. There are also systems that use, besides the solar concentrator, optical reflectors to redirect the concentrated sunlight [3, 5, 6].

Stirling motor solar concentrators also include hybrid systems that use both concentrated solar energy and thermal energy from combustion fuels to replace times when solar energy is low or lacking [4, 7-10].

d) exposing the invention in terms that allow the understanding of the technical problem (even if the technical problem is not explicitly mentioned) and of the solution as

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• technical problem;

Stirling solar-motor concentrator systems are part of the alternative energy generation systems, which are in compliance with environmental standards.

The major disadvantage of these alternative energy sources is that they are not permanent. Thus, the idea of hybrid systems using an auxiliary energy source appeared to compensate for the times when the primary energy source disappears or is reduced in intensity.

Most Stirling solar-concentrator systems use large parabolic mirrors to concentrate solar radiation. Making these large mirrors is not a negligible problem and the production prices are high. Even in the case of their modular realization, a malfunction in one of the components makes it impossible to replace only the respective component. Moreover, they have disadvantages by the shading brought by the positioning of the Stirling engine and by the length of its supporting arm which removes the center of gravity of the system from the central axis. Using a secondary reflector in the focus of the main receiver [3] to be able to place the Stirling motor at the base of the main receiver (parabolic mirror) removes this drawback but does not solve the problem of shading and high costs due to the use of large parabolic mirrors. On the other hand, the use of several Fresnel lenses, instead of the large parabolic mirror, as main concentrators coupled with secondary reflectors to concentrate solar energy at the same focal point [5] solves some of the problems presented above but reduces the efficiency of the system due to losses. induced by multiple reflections / refractions.

• exposing the invention;

The system presented in this invention is a hybrid one, for cogeneration of electric and thermal energy from mixed sources, consisting of a system of solar concentrators (2) with multiple foci, elements (41) for receiving and transferring the thermal energy to the combustion chamber.

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11/23/2018 (32) of a Stirling engine (31) coupled with an electric generator (33). The assembly is mounted on a two-axis tracking system (1) that allows solar tracking throughout the day. The thermal energy resulting from the concentrated solar energy (44), is taken from the thermal receiver (41) by the heat agent (43) gas (oxygen enriched air) and reaches through the distribution system (54) directly into the combustion chamber (32). ) of the Stirling engine (31) where it is used in the combustion process. The gaseous thermal agent (43) is preheated in the thermal recuperator (34) on the exhaust pipe of the Stirling engine's flue gas (31), before reaching the thermal receiver (41). Depending on the temperature at which the thermal agent (43) reaches the gas in the combustion chamber, the assembly is provided with an automated system (6) of proportional control and control of the flow rate of hydrogen gas fuel mixture to compensate for the moments with reduced sun / absent and keep the hot part of the Stirling engine (31) at a constant temperature regardless of the sunny conditions. The second thermal recuperator (35) on the exhaust path of the Stirling engine's exhaust gases (31) is provided with cooled thermoelectric elements for the conversion of heat energy into electricity. Their cooling system is connected to that of the Stirling engine (31) and includes a heat exchanger (7) for the recovery of thermal energy in the form of hot water. The assembly also comprises an inverter (8), batteries (9) for the conversion and storage of the electricity produced and an electrolyser (10) which uses the surplus of electricity in the process of electrolysis of the water thus obtaining the oxygen and hydrogen used for the enrichment of air and respectively gas fuel.

• benefits;

Compared to the prior art, the proposed solution has the following advantages cumulated and integrated in the same system:

- uses a system of solar concentrators (2) with multiple foci removing the classical concentrator with parabolic mirrors of large dimensions and focal length which has the following advantages: low cost, reduced focal length allowing a compact assembly whose center of gravity is closer by the central axis thus reducing the constructive dimensions of the support system, of 2018 00849

23/11/2018 implicitly the overall size and of the system, is a modular system with independent lenses that allows the rapid replacement of an element in case of failure;

- due to the hybrid system (mixed sources) it can work at low irradiation (cloudy sky) or at night; this is possible thanks to its own automated system for controlling and controlling the flow rate of hydrogen gas fuel, so that the temperature of the Stirling engine heat exchanger does not fall below the minimum operating value regardless of the sunny conditions;

- uses the surplus of electricity in the process of electrolysis of the water, thus obtaining the oxygen and hydrogen used to enrich the air and the gas fuel respectively;

- produces both electric and thermal energy;

- has a system of recovery (34, 35), in two stages, of the thermal energy from the flue gases;

- the heat receivers (41) from the outbreak of the solar concentrators (2) are interconnected in parallel with the flow distribution system (54) and have isolation valves (53) which, in the event of a possible failure, allow the isolation of the route in question, which is not necessary stopping the whole assembly.

e) brief presentation of explanatory drawings

Figure 1. In this figure is presented the principle diagram of hybrid assembly of cogeneration electric and thermal energy from mixed sources.

Figure 2. In this figure is shown a front view of the subassembly 12. Figure 3. In this figure is shown a section through the thermal receiver system (4) from the focus of the solar concentrator (2).

Figure 4. A diagram of the entire energy process is shown in this figure. Figure 5. In this figure an embodiment of 12 solar concentrators and a Stirling motor with a 3 kW electric generator is shown.

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f) detailed description of the invention for which protection is requested; In this exposition, one or more examples of embodiment and operation with reference to the drawings must be presented; the exposure is made clear, complete and correct so that a skilled person can achieve it without inventive activity;

- if the production or use of the object of the invention does not result explicitly from the description or the nature of the invention, it is necessary to describe how the object of the invention is used, exploited or manufactured;

- formulas, models, algorithms can be presented in the description without presenting the object of the invention in the embodiment exclusively based on them

The present invention relates to a hybrid assembly of cogeneration of electric and thermal energy from mixed sources, consisting of a system of solar concentrators (2), with multiple foci, elements (41) for receiving and transferring the thermal energy to the thermal agent (43) gas which in turn is transferred through the flow distribution system (54) to a Stirling motor (3) coupled with an electric generator. The assembly is mounted on a two-axis tracking system (1) that allows solar tracking throughout the day. The principle diagram is shown in Figure 1. The dimensions of the system (1) depend on the number of solar concentrators (2) installed and the dimensions of the Stirling engine (31) installed. The system (1) is composed of a support frame (11) which also allows the azimuthal movement of the whole assembly, to which the frame (12) which allows the elevation movement is connected and on which the Stirling motor assembly (3) are mounted, the concentrators solar (2), the flow distribution system (54) of the heat agent (43) gas and the support (13) on which the receiving elements (41) are mounted. The bracket (13) includes a 3-axis position adjustment system that allows the positioning of the elements (41) in the focus of the solar concentrators (2). The assembly (1) also includes motors and reducers that ensure the movement of the assembly on the two axes, some angular position readers, and a GPS system for identifying the geographical coordinates, date and time, necessary for positioning.

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The solar energy is concentrated (44) with the help of solar concentrators (2), Fresnel lens type, on the thermal receivers (41) which also act as heat exchangers, transferring the thermal energy, received from the concentrated solar radiation (44), to the thermal agent. (43) gases. The solar concentrators (2) are grouped matrix by n rows and k columns, resulting, as can be seen in figure 2, a system with multiple n * k foci that are interconnected (54) parallel and coupled with the combustion chamber (34). of a Stirling engine (31). The use of identical Fresnel lenses instead of parabolic mirrors brings a number of advantages that have been described above. The thermal receiver (41) from the Fresnel lens focal point is designed and optimized for the type of lens presented in the embodiment, so that it has a high efficiency in capturing and transferring heat to the thermal agent (43). The focal receiver (41) is placed in a refractory-insulating brick (42) to minimize heat loss. A section through the receiver (41) is shown in Figure 3. The shape of the receiver (41) is of the lamellar type. The air enters the receiver (41) at the bottom, gradually warms up on the route and leaves it in the upper area that has the highest temperature being positioned in the focus area of the solar concentrator (2).

Before reaching the focal receiver (41), the heat agent (43) is preheated in the heat recovery unit (34), which is a heat exchanger by which part of the heat energy from the combustion gases of the Stirling engine is recovered ( 31) and transferred to the thermal agent (43). Upon exiting the recuperator (34), the heat agent (43) is distributed to the thermal receivers (41) from the Fresnel lens outbreak and then reaches the combustion chamber using a thermally insulated distribution system (54) to minimize energy losses. The heating, distribution and control system (5) of the thermal agent flow (43) includes a flow source (51) which can be a compressor, fan, etc., a system for regulating the flow and the proportion of oxygen enriched air. (52), flow pipes and distributors (54) and flow isolation valves (53). A schematic of the entire energy process is shown in Figure 4.

The heat exchanger of the Stirling engine (31), located in the combustion chamber (32), must be maintained at a constant temperature, necessary for continuous operation. To compensate for the periods with low sun or without sun, the combustion chamber (32) is provided with burners of gas mixture (biogas, methane gas, etc.) with hydrogen as an auxiliary source of 2018 00849

11/23/2018 of energy. The combustion process is controlled by an automated system (6) of proportional control of the flow and of the fuel mixture.

The second thermal recuperator (35) on the exhaust path of the Stirling engine's exhaust gases (31) is provided with cooled thermoelectric elements for the conversion of heat energy into electricity. Their cooling system is connected to that of the Stirling engine (31) and includes a heat exchanger (7) for the recovery of thermal energy in the form of hot water. The assembly also comprises an inverter (8), batteries (9) for the conversion and storage of the electricity produced and an electrolyser (10) which uses the surplus of electricity in the process of electrolysis of the water thus obtaining the oxygen and hydrogen used for the enrichment of air and respectively gas fuel.

Embodiment examples

The assembly can be dimensioned and configured so that it corresponds to both the local irradiance characteristics and the consumer's electrical and thermal energy requirements.

One embodiment is shown in Figure 5. It is composed of: 12 5 mm thick PMMA Fresnel lens concentrators (2), with an active surface of approximately 0.92 m ² , 1.3 m focal length, and a transmittance of 90%. The Stirling motor (31) installed is a prototype, with a 3kW power generator (33). The solar tracking system (1) is sized to be able to take over the loading forces of the entire system as well as the external forces (wind, snow, etc.).

Bibliography

1. Roelf J. Meijer, Solar powered Stirling engine, US4707990A

2. Glendon M. Benson, Solar powered free-piston Stirling engine, US4642988A

3. Cristina Naranjo Sosa, Felix Gilabert Munoz, Isaac Garaway, Erez Harel, David

Klein, Stirling engine solar concentrator system, WO 2011/053895 A to 2018 00849

11/23/2018 'ζ /

4. Mark Mehos, Kenneth Anselmo, James Moreno, Charles Andraka, K. Rawlinson, John Corey, Mark Bohn, Dish / stirling hybrid-receiver, US20020059798A1

5. Gilbert Cohen, Roland Winston, Multiple reflector solar concentrators and systems, US20040140000A1

6. Multiple-focus matching Fresnel lens system, CN103885165A

7. John F. W. Parry, Hot air solar engine, US4414812A

8. Edgar English, Jr., Solar energy conversion device provided with an automatic cut-in heat-supplying standby device, US4398391A

9. Worth H. Percival, David N. Wells, Hybrid solar / combustion powered receiver, US4602614A

10. Yilong Chen, Qingping Yang, Yanfeng Zhang, Disc-type solarstirling engine power generation device capable of continuously operating day and night, EP2716910A4 to 2018 00849

11/23/2018 V *

g) Claims

Claims (5)

1. Multi-focus solar concentrator and Stirling engine, characterized in that it consists of an automated solar tracking support (1) on which are mounted: several solar concentrators (2) that focus solar energy on thermal receivers (41) , a system (5) for mixing, distributing, driving and controlling the flow of the thermal agent (43) gas coupled to the thermal receivers (41), a Stirling motor assembly (31) - electric generator (33), powered by an automated system of mixing and proportional control of the gas fuel flow (6) enriched with hydrogen, a heat exchanger (7) connected in the common cooling system of the Stirling engine (31) and the thermoelectric elements of the recuperator (35), an inverter (8 ) coupled with the electric generator (43), some batteries (9) and an electrolyzer (10). 2. Stirling motor with multiple foci and motor, according to claim 1, characterized in that the solar concentrators (2) are grouped matrix in n rows and k columns, resulting in a system with n * k multiple foci which are interconnected ( 54) parallel and coupled to the combustion chamber (32) of a Stirling engine (31); 3. Multi-focus solar concentrator and Stirling motor according to claims 1, 2, characterized in that each receiver (41), connected independently and in parallel with the rest of the receivers (41), has flow isolation valves (53). of heat agent (43) which can be operated independently; 4. Multi-focus solar concentrator and Stirling motor according to claims 1, 2, 3, characterized in that the heat energy resulting from the conversion of the concentrated solar energy (44) is stored in a gas thermal agent (43) which is transferred through thermally insulated pipes (54), under the pressure provided by a compressor (51) in the chamber combustion (32) of the Stirling engine (31) and used directly in the combustion process of the Stirling engine (31); Thermal receiver (41) according to claim 1, characterized in that it has a thermally insulated, lamellar structure (42), which captures the concentrated solar energy (44) and transfers it to a gas thermal agent (43).