Solar power station and method for judging local cloud of heliostat field of solar power station

Abstract

The invention discloses a solar power station and a heliostat field local cloud judgment method thereof, and belongs to the technical field of photo-thermal power station power generation, and the method comprises the following steps: S1, determining a heliostat region corresponding to each heated unit of a heat absorber by adopting an equal angle method; s2, according to the effective absorption power coefficient of the heated unit of the heat absorber in the S1, whether local cloud appears in a heliostat area corresponding to the heated unit or not is judged; s3, if the local cloud appears in the heliostat area corresponding to the heated unit in the S2, judging whether the local cloud in the heliostat area corresponding to the heated unit disappears or not, and turning to a sunny day; and S4, when the local cloud of the heliostat area corresponding to the heated unit calculated by the heat absorber disappears and turns into a sunny day, cooling the corresponding heated unit. According to the invention, the damage to the heat absorber caused by the existence of a measurement dead zone in a point measurement type heliostat can be effectively avoided, so that the safe operation of the heat absorber in the presence of any local cloud is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation in a solar thermal power station, and in particular to a method for determining a local cloud in a heliostat field of a solar power station. Background Art

[0002] In the field of solar energy, "mirror field" usually refers to an array composed of a large number of mirrors (such as heliostats) to concentrate sunlight for efficient use of solar energy. A heliostat field is an optical device that uses an array of mirrors made of special materials to concentrate sunlight. It focuses sunlight into a small area by adjusting the curvature and angle of the mirror, thereby improving the efficiency of solar energy utilization. Heliostat fields are widely used in solar power generation, solar thermal utilization, solar thermal power generation, and solar pyrolysis. Based on the optical focusing effect, a heliostat field uses mirrors made of materials with high reflectivity and low absorption to focus sunlight into a specific area at a certain angle, such as a solar cell, a collector tube, or a collector, to achieve purposes such as photoelectric conversion, thermal energy utilization, or chemical reactions.

[0003] With the growing demand for renewable energy, heliostats are gradually being widely used as an important technical means of utilizing solar energy. They can not only improve the utilization efficiency of solar energy, but also reduce the cost of power generation and promote the popularization and promotion of solar power generation.

[0004] At present, most solar power stations use a number of point-measurement direct radiation meters set up in different areas of the heliostat field to directly measure the DNI value. According to the deviation between the DNI theoretical value and the measured value, it is judged whether there are clouds in the mirror field.

[0005] Since the direct solar radiation meter is a point-measurement instrument, its measurement range cannot cover the entire mirror field. Therefore, a considerable area in the mirror field is in the measurement dead zone. When local clouds appear in the measurement dead zone, the control system does not take protective measures for the absorber. After the local clouds move away from the mirror field, the direct consequence is that the absorber overheats, causing its absorber tube to deform, causing considerable losses to the power station. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for calculating the effective coefficient of power absorbed by a heat absorber intermittently directly by a power station control system. Because the calculation method is an overall calculation of the area of ​​the corresponding region, there is no measurement dead zone that exists in the use of conventional point-measurement type pyranometers, and the harm to the heat absorber caused by the existence of measurement dead zones by the use of point-measurement type pyranometers is effectively avoided, thereby ensuring the safe operation of the heat absorber in the presence of any local cloud.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A solar power station comprises a cylindrical heat absorption tower, a heat absorber evenly distributed at the upper end of the heat absorption tower and a heliostat field arranged at the lower end of the heat absorption tower; the heat absorber comprises N heating surfaces arranged in parallel in an annular manner; every two adjacent heating surfaces constitute a heating unit; the molten salt inlet mother pipe of the heat absorber is connected to a cold molten salt storage tank, and the molten salt outlet mother pipe of the heat absorber is connected to a hot molten salt storage tank; the molten salt inlet mother pipe of the heat absorber is provided with a molten salt flowmeter FT and a pressure transmitter PT; a temperature meter TE is provided at the inlet and outlet of each of the heating units; the heliostats are arranged in a circle to form a heliostat field, and the center of the heliostat field coincides with the center of the annular heat absorber; each heating unit is heated by the heliostats in the corresponding area.

[0009] A method for determining local cloud in a heliostat field of a solar power station comprises the following steps:

[0010] S1, using the equal angle method to determine the area of ​​the heliostat corresponding to each heating unit of the heat absorber;

[0011] S2, judging whether local clouds appear in the heliostat area corresponding to the heating unit according to the effective coefficient of power absorption of the heating unit of the heat absorber in S1;

[0012] S3, if local clouds appear in the heliostat area corresponding to the heated unit in S2, determine whether the local clouds in the heliostat area corresponding to the heated unit disappear and the weather turns sunny;

[0013] S4. When the local clouds in the heliostat area corresponding to the heat receiving unit calculated by the heat absorber disappear and the weather turns sunny, the corresponding heat receiving unit is cooled down.

[0014] The further improvement of the technical solution of the present invention is that: in S1, the effective coefficient of absorbed power of each heat receiving unit of the heat absorber is calculated:

[0015]

[0016] Among them, EF (t,t+1) is the effective coefficient of power absorption of the heating unit composed of adjacent heating surfaces t and t+1 at the current moment, t<N; P THEOR is the theoretical absorbed power of the heating unit composed of adjacent heating surfaces t and t+1 at the current moment, and its value is calculated by the control system based on the heliostat field efficiency model provided by the heliostat manufacturer, the absorber heating model and efficiency model provided by the absorber manufacturer and the corresponding calculation formula; P(t, t+1) is the actual absorbed power of the heating unit composed of adjacent heating surfaces t and t+1 at the current moment calculated by enthalpy difference, and its calculation formula is shown in the formula:

[0017]

[0018] Among them, FT is the molten salt flow rate through the absorber inlet main pipe kg / s, that is, the flow rate through the heating unit composed of adjacent heating surfaces t and t+1; Tm is the molten salt outlet temperature of the heating unit composed of adjacent heating surfaces t and t+1; Tn is the molten salt inlet temperature of the heating unit composed of adjacent heating surfaces t and t+1.

[0019] A further improvement of the technical solution of the present invention is that in S2, when one of the following conditions occurs, the control system determines that a local cloud appears in the heliostat area corresponding to the heating unit:

[0020] S21 One or more effective coefficients of absorbed power of the heat receiving units of the heat absorber are lower than the threshold value TH of the heat receiving unit;

[0021] TH=MX

[0022] Among them, M is the average value of the effective coefficient of absorption power of the heating unit when the threshold value is a typical sunny day, and is the effective coefficient of absorption power of the heat absorber on a typical sunny day; X is the dead zone value;

[0023] S22 When one or more effective coefficients of absorbed power of the heat receiving units of the heat absorber decrease by more than 0.3 within 1 minute;

[0024] When the effective coefficients of power absorption of the heat receiving units (22) of all the heat absorbers (2) have been reduced in the same manner, the control system is locked to trigger the partial cloudy mode due to the sunset process.

[0025] A further improvement of the technical solution of the present invention is that in S3, when one of the following conditions occurs, the control system determines that the local cloud in the heliostat area corresponding to the calculated heating unit of the heat absorber disappears and the weather turns sunny:

[0026] S31 One or more effective coefficients of absorbed power of the heat receiving units of the heat absorber are not less than the threshold value TH of the heat receiving unit;

[0027] TH=MX

[0028] Among them, M is the average value of the effective coefficient of absorption power of the heating unit when the threshold value is a typical sunny day, and is the effective coefficient of absorption power of the heat absorber on a typical sunny day; X is the dead zone value;

[0029] S32 During the continuous 5 minutes, the effective coefficient of absorbed power of any of the heat receiving units of the heat absorber does not drop by more than 0.3 within 1 minute.

[0030] A further improvement of the technical solution of the present invention is that M is 0.9.

[0031] A further improvement of the technical solution of the present invention is that: X is 0.1.

[0032] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0033] The present invention adopts a method for directly and intermittently calculating the effective coefficient of absorbed power of the heat absorber by the power station control system. Since the calculation method is to perform an overall calculation on the area of ​​the corresponding region, there is no measurement dead zone existing in the conventional point-measurement type solar radiation meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic diagram of a solar power station in the present invention;

[0035] Figure 2 It is a schematic diagram of the heating surface in the present invention;

[0036] Figure 3 It is a connection diagram of the heating unit in the present invention;

[0037] Among them, 1. heat absorption tower, 2. heat absorber, 21. heating surface, 22. heating unit, 3. heliostat. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below with reference to the accompanying drawings and embodiments:

[0039] like Figure 1 As shown, a solar power station includes a cylindrical heat absorption tower 1, a heat absorber 2 evenly distributed at the upper end of the heat absorption tower 1, and a heliostat field 3 arranged at the lower end of the heat absorption tower 1; Figure 2 As shown, the heat absorber 2 includes N heating surfaces 21 arranged in parallel in an annular manner; every two adjacent heating surfaces 21 form a heating unit 22; Figure 3 As shown, the molten salt inlet mother pipe of the heat absorber 2 is connected to the cold molten salt storage tank, and the molten salt outlet mother pipe of the heat absorber 2 is connected to the hot molten salt storage tank; the molten salt inlet mother pipe of the heat absorber 2 is provided with a molten salt flowmeter FT and a pressure transmitter PT; a temperature instrument TE is provided at the inlet and outlet of each of the heating units 22; the heliostats 3 are arranged in a circle to form a heliostat field, and the center of the heliostat field coincides with the center of the annular heat absorber 2; each heating unit 22 is heated by the heliostats 3 in the corresponding area;

[0040] A method for determining local cloud in a heliostat field of a solar power station comprises the following steps:

[0041] S1. Since the X and Y coordinates of the center of the absorber 2 and the heliostat field are the same, the equal angle method is used to determine the area of ​​the heliostat 3 corresponding to each heating unit 22 of the absorber 2, such as Figure 1 The shaded area A is the heliostat 3 area corresponding to the heat receiving surfaces 1 and 2 of the heat absorber;

[0042] Calculate the effective coefficient of power absorption of each heat receiving unit 22 of the heat absorber 2:

[0043]

[0044] Among them, EF (t,t+1) is the effective coefficient of power absorption of the heating unit 22 composed of adjacent heating surfaces t and t+1 at the current moment, t<N; P THEOR is the theoretical absorbed power (MW) of the heating unit 22 composed of adjacent heating surfaces t and t+1 at the current moment, and its value is calculated by the control system according to the heliostat field efficiency model provided by the heliostat manufacturer, the absorber heating model and efficiency model provided by the absorber manufacturer, and the corresponding calculation formula, and can be regarded as a known value; P(t, t+1) is the actual absorbed power MW of the heating unit 22 composed of adjacent heating surfaces t and t+1 at the current moment calculated by enthalpy difference, and its calculation formula is shown in Formula 2:

[0045]

[0046] Among them, FT is the molten salt flow rate flowing through the absorber inlet mother pipe kg / s, that is, the flow rate flowing through the heating unit 22 composed of adjacent heating surfaces t and t+1; Tm is the outlet molten salt temperature of the heating unit 22 composed of adjacent heating surfaces 21t and t+1 ℃; Tn is the inlet molten salt temperature of the heating unit 22 composed of adjacent heating surfaces t and t+1 ℃;

[0047] S2, judging whether local clouds appear in the heliostat 3 area corresponding to the heating unit 22 according to the effective coefficient of power absorption of the heating unit 22 of the heat absorber 2 in S1;

[0048] When one of the following conditions occurs, the control system determines that local clouds appear in the heliostat 3 area corresponding to the heating unit 22:

[0049] S21 The effective coefficient of absorbed power of the heat receiving unit 22 of the heat absorber 2 is lower than the threshold value TH of the heat receiving unit 22;

[0050] TH=MX

[0051] Wherein, M is the average effective coefficient of the absorption power of the heat receiving unit 22 when the threshold is a typical sunny day, is the effective coefficient of the absorption power of the heat absorber on a typical sunny day, is a known value, and can be taken as M=0.9; X is the dead zone value, which can be adjusted according to the actual conditions of the mirror field, and can be taken as X=0.1;

[0052] S22 When one or more effective coefficients of absorbed power of the heat receiving units 22 of the heat absorber 2 decrease by more than 0.3 within 1 minute;

[0053] When all absorbed power effectiveness factors calculated by the above formula 1 have decreased in the same manner, the control system is locked to trigger the partial cloudy mode due to the sunset process.

[0054] S3, if local clouds appear in the heliostat 3 area corresponding to the heating unit 22 in S2, determine whether the local clouds in the heliostat 3 area corresponding to the heating unit 22 disappear and the weather turns sunny;

[0055] When one of the following conditions occurs, the control system determines that the local cloud in the heliostat 3 area corresponding to the calculated heating unit 22 of the heat absorber disappears and the weather turns sunny:

[0056] S31 one or more effective coefficients of absorbed power of the heat receiving units 22 of the heat absorber 2 are not lower than the threshold value TH of the heat receiving unit 22;

[0057] TH=MX

[0058] Wherein, M is the average effective coefficient of the absorption power of the heat receiving unit 22 when the threshold is a typical sunny day, is the effective coefficient of the absorption power of the heat absorber on a typical sunny day, is a known value, and can be taken as M=0.9; X is the dead zone value, which can be adjusted according to the actual conditions of the mirror field, and can be taken as X=0.1;

[0059] S32: During the continuous 5 minutes, the effective coefficient of absorbed power of any of the heat receiving units 22 of the heat absorber 2 does not drop by more than 0.3 within 1 minute.

[0060] S4. When the local clouds in the heliostat 3 area corresponding to the heat receiving unit 22 calculated by the heat absorber 2 disappear and the weather turns sunny, the corresponding heat receiving unit 22 is cooled down.

[0061] After the local cloud moves away from the mirror field, the direct consequence is that the heating unit 22 is overheated, so that its heat absorption tube is deformed, causing considerable losses to the power station, so the heating unit 22 is cooled.

[0062] Example

[0063] 1) For a cylindrical heat absorber, the heat absorber consists of N heating surfaces, where N is an even number and a known number. Its value is determined by the heat absorber manufacturer based on the unit capacity and the scale of the mirror field, and can be 24, 26, 28, 30, 32, etc. Figure 2 As shown;

[0064] 2) Every two adjacent heating surfaces 21 form a heating unit 22. A molten salt flow meter FT and a pressure transmitter are installed at the molten salt inlet main pipe of the heat absorber. A temperature instrument TE is installed at the inlet and outlet of each heating unit 22. Figure 3 As shown;

[0065] 3) For the cylindrical heat absorber 2, the heliostats 3 are arranged in a circular shape as a heliostat field. Each heat receiving unit 22 is heated by the heliostats 3 in the corresponding area. Since the center X and Y coordinates of the heat absorber and the heliostat field are the same, the equal angle method is used to determine the area of ​​the heliostat 3 corresponding to each heat receiving unit 22 of the heat absorber 2, such as Figure 1 The shaded area A is the heliostat area corresponding to the heat receiving surfaces 1 and 2 of the heat absorber;

[0066] 4) Calculate the effective coefficient EF of absorbed power of each heating unit 22:

[0067]

[0068] When one of the following conditions occurs, the control system may determine that a local cloud appears in the heliostat 3 area corresponding to the heat receiving unit 22 calculated by the heat absorber:

[0069] (1) One or more EF values ​​are less than the EF average value M at this moment on a typical sunny day minus the dead zone value X, where M is the effective coefficient of the heat absorber absorption power on a typical sunny day, M = 0.9; X is the dead zone value, X = 0.1;

[0070] (2) When one or more EF values ​​decrease by more than 0.3 within 1 minute;

[0071] When all EF values ​​calculated by the above formula (1) have decreased in the same way, the control system is locked to trigger the local cloudy mode due to the sunset process;

[0072] When one of the following conditions occurs, the control system can determine that the local cloud in the heliostat 3 area corresponding to the heat receiving unit 22 calculated by the heat absorber disappears and the weather turns sunny:

[0073] (1) One or more EF values ​​are not less than the EF average value M at this moment on a typical sunny day minus the dead zone value X, where M is the effective coefficient of the heat absorber absorption power on a typical sunny day, M = 0.9; X is the dead zone value, X = 0.1;

[0074] (2) During the 5-minute period, none of the EF values ​​calculated by the above formula (1) decreased by more than 0.3 within 1 minute.

[0075] In summary, the present invention effectively avoids the damage to the heat absorber caused by the existence of a measurement dead zone in a point-measurement type pyranometer, thereby ensuring the safe operation of the heat absorber in the presence of any local cloud.

Claims

1. A solar power station, characterized in that: The invention comprises a cylindrical heat absorption tower (1), a heat absorber (2) evenly distributed at the upper end of the heat absorption tower (1), and a heliostat field (3) arranged at the lower end of the heat absorption tower (1); the heat absorber (2) comprises N heating surfaces (21) arranged in parallel in an annular manner; every two adjacent heating surfaces (21) form a heating unit (22); the molten salt inlet mother pipe of the heat absorber (2) is connected to a cold molten salt storage tank, and the molten salt outlet mother pipe of the heat absorber (2) is connected to a hot molten salt storage tank; the molten salt inlet mother pipe of the heat absorber (2) is provided with a molten salt flowmeter FT and a pressure transmitter PT; a temperature meter TE is provided at the inlet and outlet of each of the heating units (22); the heliostats (3) are arranged in a circular shape to form a heliostat field, and the center of the heliostat field coincides with the center of the annular heat absorber (2); and each heating unit (22) is heated by the heliostats (3) in the corresponding area.

2. A method for determining local cloud in a heliostat field of a solar power station, characterized in that: The following steps are involved: S1, using an equal angle method to determine the area of ​​the heliostat (3) corresponding to each heating unit (22) of the heat absorber (2); S2, judging whether a local cloud appears in the heliostat (3) region corresponding to the heating unit (22) according to the effective coefficient of power absorption of the heating unit (22) of the heat absorber (2) in S1; S3, if local clouds appear in the heliostat (3) region corresponding to the heating unit (22) in S2, determine whether the local clouds in the heliostat (3) region corresponding to the heating unit (22) disappear and the weather turns sunny; S4. When the local cloud in the heliostat (3) region corresponding to the heat receiving unit (22) calculated by the heat absorber (2) disappears and the weather turns sunny, the corresponding heat receiving unit (22) is cooled down.

3. The method for determining local cloud in a heliostat field of a solar power station according to claim 2, characterized in that: In S1, the effective coefficient of power absorption of each heat receiving unit (22) of the heat absorber (2) is calculated: Among them, EF (t,t+1) is the effective coefficient of power absorption of the heating unit (22) composed of adjacent heating surfaces t and t+1 at the current moment, t<N; P THEOR is the theoretical absorbed power of the heating unit (22) composed of adjacent heating surfaces t and t+1 at the current moment, and its value is calculated by the control system according to the heliostat field efficiency model provided by the heliostat manufacturer, the absorber heating model and efficiency model provided by the absorber manufacturer and the corresponding calculation formula; P(t, t+1) is the actual absorbed power of the heating unit (22) composed of adjacent heating surfaces t and t+1 at the current moment calculated by the enthalpy difference, and its calculation formula is shown in formula (2): Wherein, FT is the molten salt flow rate kg / s flowing through the absorber inlet main pipe, that is, the flow rate flowing through the heating unit (22) composed of adjacent heating surfaces t and t+1; Tm is the outlet molten salt temperature of the heating unit (22) composed of adjacent heating surfaces (21) t and t+1; Tn is the inlet molten salt temperature of the heating unit (22) composed of adjacent heating surfaces t and t+1.

4. The method for determining local cloud in a heliostat field of a solar power station according to claim 2, characterized in that: In S2, when one of the following conditions occurs, the control system determines that a local cloud appears in the heliostat (3) area corresponding to the heating unit (22): S21: one or more of the effective coefficients of absorbed power of the heat receiving units (22) of the heat absorber (2) is lower than a threshold value TH of the heat receiving unit (22); TH=MX Wherein, M is the average value of the effective coefficient of absorption power of the heat receiving unit (22) at the moment when the threshold value is a typical sunny day, and is the effective coefficient of absorption power of the heat absorber on a typical sunny day; X is the dead zone value; S22 When the effective coefficient of absorbed power of the heat receiving unit (22) of the heat absorber (2) decreases by more than 0.3 within 1 minute; When the effective coefficients of power absorption of the heat receiving units (22) of all the heat absorbers (2) have been reduced in the same manner, the control system is locked to trigger the partial cloudy mode due to the sunset process.

5. The method for determining local cloud in a heliostat field of a solar power station according to claim 2, characterized in that: In S3, when one of the following conditions occurs, the control system determines that the local cloud in the heliostat (3) area corresponding to the calculated heating unit (22) calculated by the heat absorber disappears and the weather turns sunny: S31: one or more effective coefficients of absorbed power of the heat receiving units (22) of the heat absorber (2) are not less than a threshold value TH of the heat receiving unit (22); TH=MX Wherein, M is the average value of the effective coefficient of absorption power of the heat receiving unit (22) at the moment when the threshold value is a typical sunny day, and is the effective coefficient of absorption power of the heat absorber on a typical sunny day; X is the dead zone value; S32: During a continuous period of 5 minutes, the effective coefficient of absorbed power of any of the heat receiving units (22) of the heat absorber (2) does not drop by more than 0.3 within 1 minute.

6. The method for determining local cloud in a heliostat field of a solar power station according to any one of claims 4 or 5, characterized in that: M is 0.

9.

7. The method for determining local cloud in a heliostat field of a solar power station according to any one of claims 4 or 5, characterized in that: X is 0.1.

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