A method for acquiring accurate DNI data in a tower mirror field

Abstract

The present invention belongs to the technical field of DNI data processing, and specifically relates to a method for obtaining accurate DNI data for a tower mirror field. The method comprises: S1: quality judgment of direct radiation data: obtaining extraterrestrial normal direct radiation, normal direct radiation on the earth's surface, total horizontal global radiation on the earth's surface, and scattered horizontal radiation on the earth's surface from a meteorological station, and calculating the direct beam transmittance, effective global horizontal transmittance, and effective scattered horizontal transmittance in combination with the solar zenith angle; dividing the direct radiation DNI into three levels based on the direct beam transmittance, effective global horizontal transmittance, and effective scattered horizontal transmittance; S2: obtaining accurate DNI data according to the classification of direct radiation DNI. The method provided by the present invention can obtain accurate DNI data, and provide help for more accurately determining the number of heliostat projections and calculating more accurate thermal energy.

Description

Technical Field

[0001] The invention belongs to the technical field of DNI data processing, and in particular relates to a method for acquiring accurate DNI data of a tower mirror field. Background Art

[0002] The number of heliostats currently required for a tower CSP field is determined by weather station irradiance data, and irradiance measurement equipment may contain error elements, whether due to variability in the calibration process, imperfect measurement accuracy, inaccurate solar tracking, or the result of cleanliness and obstructions. The irradiance value calculated by the weather station is critical to the operation of the CSP power plant, because the number of heliostats that must be activated to meet the flux demand of the receiver is determined by the currently available solar flux.

[0003] In a CSP system, the level of DNI directly affects the heat collection effect and power generation of the mirror field. DNI represents the direct solar radiation power received per unit area on a plane perpendicular to the sun's rays. Therefore, obtaining accurate DNI data is crucial for the development of CSP projects. Accurate DNI data can be used to optimize the design and operation of the mirror field and improve the efficiency and performance of the CSP system.

[0004] DNI is a key parameter when designing and planning a tower field. Since DNI represents the direct solar radiation power received per unit area on a plane perpendicular to the sun's rays, it directly determines how many heliostats are needed to achieve the desired collection effect. In areas with higher DNI, fewer heliostats may be needed to meet demand, while in areas with lower DNI, more heliostats are needed to compensate for energy losses.

[0005] At present, most large-scale ground power stations in China are still equipped with domestic irradiation equipment, which has low equipment stability. The photovoltaic system efficiency PR of the power station calculated from the real-time irradiation data obtained can often be greater than 100%.

[0006] During the operation of a weather station, even if advanced equipment is used, data may be lost on one or several days due to power outages or equipment calibration problems, resulting in a large deviation in the data for an entire month or year and making it unusable, and the resulting irradiation data quality is inaccurate.

[0007] In summary, the current problems with DNI measurement include:

[0008] (1) The lack of advanced measurement technology: Traditional measurement methods may lack advanced technology and equipment, resulting in low measurement efficiency and low accuracy. Especially in the determination of DNI data of CSP power plants, more complex and accurate technology is needed to capture the energy of direct solar radiation.

[0009] (2) During the DNI measurement process, various technical difficulties and problems may be encountered. If there is a lack of necessary technical support, these problems may not be effectively solved, thus affecting the accuracy and reliability of the measurement. Summary of the invention

[0010] In view of the above technical problems, the present invention provides a method for judging the quality of radiation data of a meteorological station; the irradiation data uses the values ​​obtained by GHI and Diff to check the quality of all values ​​of the average DNI, divides the data into three levels according to the quality, and distributes the data according to the levels.

[0011] The present invention is achieved through the following technical solutions:

[0012] A method for acquiring accurate DNI data of a tower mirror field, the method comprising:

[0013] S1: Quality judgment of direct radiation data: obtain the extraterrestrial normal direct radiation, the normal direct radiation of the earth's surface, the total horizontal global radiation of the earth's surface, and the scattered horizontal radiation of the earth's surface from the meteorological station, and calculate the direct beam transmittance, effective global horizontal transmittance, and effective scattered horizontal transmittance in combination with the solar zenith angle; divide the direct radiation DNI into three levels based on the direct beam transmittance, effective global horizontal transmittance, and effective scattered horizontal transmittance;

[0014] S2: Obtain accurate DNI data based on the grading of direct radiation DNI.

[0015] Furthermore, step S1 is specifically as follows:

[0016] (1) Obtain the value of the normal direct radiation on the earth's surface through the meteorological station, that is, obtain the value of the direct radiation DNI on the earth's surface. If the data is empty, wait until there is data;

[0017] (2) Obtain the values ​​of the total horizontal global radiation GHI and the scattered horizontal radiation DHI of the earth's surface, and initialize the level of direct radiation DNI to 0;

[0018] (3) Determine whether the effective scattering level transmittance kd is greater than 0;

[0019] When kd is greater than 0, the level of direct radiation DNI is changed to 1 and the process goes to step (4); when kd is not greater than 0, the process directly returns to the current level, that is, the level of direct radiation DNI remains unchanged at 0 and the process goes to step (6);

[0020] Among them, K d =I d / (I 0 cosZ); Kd is the effective scattering horizontal transmittance; I d is the scattered horizontal radiation from the earth's surface; I 0 is the direct normal radiation outside the Earth; Z is the solar zenith angle; I 0 cosZ is the extraterrestrial radiation in a plane parallel to the Earth’s surface;

[0021] (4) Compare the effective global horizontal transmittance kt and the direct beam transmittance kn. If kt>kn, change the level of direct radiation DNI to 3 and proceed to step (5); when kt is not greater than kn, return to the current Level directly; that is, keep the level of direct radiation DNI unchanged at 1 and proceed to step (6);

[0022] Among them, K n =I n / I 0 ; K t =I t / (I 0 cosz);I 0 I is the extraterrestrial normal direct radiation; n is the normal direct radiation on the earth’s surface; I t is the total horizontal global radiation at the Earth's surface; I 0 cosz is the extraterrestrial radiation in a plane parallel to the Earth's surface;

[0023] (5) Calculate the error threshold and average value;

[0024] Error threshold = maximum DNI value * empirical DNI error tolerance coefficient;

[0025] Value = |kt-kn-kd|;

[0026] The maximum DNI value refers to the maximum value of the direct radiation DNI data obtained from the meteorological station; compare the value with the error threshold, if the value is less than or equal to the error threshold, change the level of the direct radiation DNI to 6 and go to step (6);

[0027] If the value is greater than the error threshold, the current Level is returned, that is, the level of direct radiation DNI remains unchanged, and the Level is still 3, and the process goes to step (6);

[0028] (6) Obtain the levels corresponding to all direct radiation DNIs. When the level is less than or equal to 0, output the quality label of the corresponding direct radiation DNI as bad;

[0029] When the level is greater than zero and less than or equal to 3, the quality label of the corresponding direct radiation DNI is output as uncertain;

[0030] When the level is greater than 3, the quality label of the corresponding direct radiation DNI is output as good.

[0031] Furthermore, in step (5), the empirical DNI error tolerance coefficient is set to 0.05.

[0032] Furthermore, step S2 is specifically as follows:

[0033] (1) Determine the number of direct radiation DNIs with quality labels of good and uncertain output in step S1;

[0034] When the quantity is 0, the clear sky DNI is calculated as the final direct radiation DNI value, the quality label assigned to the final DNI value is good, and the direct radiation DNI and the quality label are output;

[0035] When the quantity is equal to 1, the value and quality label of the corresponding direct radiation DNI are obtained and output;

[0036] When the number is greater than or equal to 2, the quality level of the direct radiation DNI value is determined. When the number of direct radiation DNI values ​​of level 6 is greater than or equal to 1, step (2) is entered; when the number of direct radiation DNI values ​​of level 6 is equal to 0, step (3) is entered;

[0037] (2) Count the values ​​and quantity of direct radiation DNI of level 6, add up the values ​​of all direct radiation DNI of level 6 and divide by the corresponding quantity to obtain the average value of direct radiation DNI of level 6, and the quality label corresponding to the average value is good; output the average value and quality label of direct radiation DNI.

[0038] (3) Count the values ​​and quantity of direct radiation DNI of level 3, add up the values ​​of all direct radiation DNI of level 3 and divide by the corresponding quantity to obtain the average value of direct radiation DNI of level 3, and the quality label corresponding to the average value is uncertain; output the average value and quality label of direct radiation DNI.

[0039] Beneficial technical effects of the present invention:

[0040] The method provided by the present invention can obtain accurate DNI data, and provide assistance for more accurately determining the amount of illumination of the heliostat and calculating more accurate thermal energy. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.

[0043] A method for acquiring accurate DNI data of a tower mirror field, the method comprising:

[0044] S1: Quality judgment of direct radiation data: Obtain the extraterrestrial normal direct radiation (I 0 ), the normal direct radiation of the earth's surface (i.e., the earth's surface DNI), the total horizontal global radiation of the earth's surface (GHI), the diffuse horizontal radiation of the earth's surface (DHI), combined with the solar zenith angle (Z), calculate the direct beam transmittance, effective global horizontal transmittance and effective diffuse horizontal transmittance; based on the direct beam transmittance, effective global horizontal transmittance and effective diffuse horizontal transmittance, the direct radiation DNI is divided into three levels;

[0045] S2: Obtain accurate DNI data based on the grading of direct radiation DNI.

[0046] In this embodiment, step S1 is specifically as follows:

[0047] (1) Obtain the value of the normal direct radiation on the earth's surface through the meteorological station, that is, obtain the value of the direct radiation DNI on the earth's surface. If the data is empty, wait until there is data;

[0048] (2) Obtain the values ​​of the total horizontal global radiation GHI and the scattered horizontal radiation DHI of the earth's surface, and initialize the level of direct radiation DNI to 0;

[0049] (3) Determine whether the effective scattering level transmittance kd is greater than 0;

[0050] When kd is greater than 0, the level of direct radiation DNI is changed to 1 and the process goes to step (4); when kd is not greater than 0, the process directly returns to the current level, that is, the level of direct radiation DNI remains unchanged at 0 and the process goes to step (6);

[0051] Among them, K d =I d / (I0 cosZ); K d is the effective scattering horizontal transmittance; I d is the diffuse horizontal radiation of the earth's surface (i.e. DHI); I 0 is the extraterrestrial normal direct radiation (i.e. extraterrestrial DNI); Z is the solar zenith angle; I 0 cosZ is the extraterrestrial radiation in a plane parallel to the Earth’s surface;

[0052] (4) Compare the effective global horizontal transmittance kt and the direct beam transmittance kn. If kt>kn, change the level of direct radiation DNI to 3 and proceed to step (5); when kt is not greater than kn, return to the current Level directly; that is, keep the level of direct radiation DNI unchanged at 1 and proceed to step (6);

[0053] Among them, K n =I n / I 0 ; K t =I t / (I 0 cosz);I 0 I is the extraterrestrial normal direct radiation; n is the normal direct radiation of the earth's surface (i.e., the earth's surface DNI); I t is the total horizontal global radiation at the Earth's surface (i.e., GHI); I 0 cosz is the extraterrestrial radiation in a plane parallel to the Earth's surface;

[0054] (5) Calculate the error threshold and average value;

[0055] Error threshold = maximum DNI value * empirical DNI error tolerance coefficient;

[0056] Value = |kt-kn-kd|;

[0057] The maximum DNI value refers to the maximum value of the direct radiation DNI data obtained from the meteorological station; compare the value with the error threshold, if the value is less than or equal to the error threshold, change the level of the direct radiation DNI to 6 and go to step (6);

[0058] If the value is greater than the error threshold, the current Level is returned, that is, the level of direct radiation DNI remains unchanged, and the Level is still 3, and the process goes to step (6);

[0059] (6) Obtain the levels corresponding to all direct radiation DNIs. When the level is less than or equal to 0, output the quality label of the corresponding direct radiation DNI as bad;

[0060] When the level is greater than zero and less than or equal to 3, the quality label of the corresponding direct radiation DNI is output as uncertain;

[0061] When the level is greater than 3, the quality label of the corresponding direct radiation DNI is output as good.

[0062] After this step, the direct radiation DNI values ​​obtained from the meteorological station are divided into three levels, and the larger the value, the better the quality of the corresponding irradiance data.

[0063] In this embodiment, in step (5), the empirical DNI error tolerance coefficient is set to 0.05; according to actual test experience, 0.05 is optimal.

[0064] In this embodiment, step S2 is specifically as follows:

[0065] (1) Determine the number of direct radiation DNIs with quality labels of good and uncertain output in step S1;

[0066] When the quantity is 0, the clear sky DNI is calculated as the final direct radiation DNI value, the quality label assigned to the final DNI value is good, and the direct radiation DNI and the quality label are output;

[0067] When the quantity is equal to 1, the value and quality label of the corresponding direct radiation DNI are obtained and output;

[0068] When the number is greater than or equal to 2, the quality level of the direct radiation DNI value is determined. When the number of direct radiation DNI values ​​of level 6 is greater than or equal to 1, step (2) is entered; when the number of direct radiation DNI values ​​of level 6 is equal to 0, step (3) is entered;

[0069] (2) Count the values ​​and quantity of direct radiation DNI of level 6, add up the values ​​of all direct radiation DNI of level 6 and divide by the corresponding quantity to obtain the average value of direct radiation DNI of level 6, and the quality label corresponding to the average value is good; output the average value and quality label of direct radiation DNI.

[0070] (3) Count the values ​​and quantity of direct radiation DNI of level 3, add up the values ​​of all direct radiation DNI of level 3 and divide by the corresponding quantity to obtain the average value of direct radiation DNI of level 3, and the quality label corresponding to the average value is uncertain; output the average value and quality label of direct radiation DNI.

[0071] The existing meteorological stations in the mirror field do not optimize the quality of the irradiation data, which may misjudge the irradiation data, resulting in inaccurate control systems in the mirror field. The method provided by the present invention can obtain accurate DNI data. After optimizing the irradiation quality, the amount of irradiation of the heliostat can be determined more accurately, and the calculated thermal energy is also more accurate.

[0072] Because the thermal energy of a solar thermal power plant will change according to actual conditions, more heliostats will be needed for projection when the thermal energy is large. When the thermal energy is fixed, the number of heliostats can be calculated.

[0073] In clear weather with no clouds blocking the view, the theoretical heat energy of a mirror is calculated as:

[0074] Q=DNI*A

[0075] Q is the theoretical thermal energy corresponding to the mirror at the current DNI; A is the mirror area;

[0076] The reflected heat energy needs to be multiplied by the refraction loss, and the theoretical reflected heat energy is Q 反射 =Q*0.98.

[0077] The collector cutoff efficiency reflects the efficiency of the collector in converting solar radiation energy into thermal energy and is an important indicator for evaluating the performance of the collector.

[0078] A simplified calculation method is based on the principle of heat absorption of heliostat collectors. The absorbed heat can be approximated as solar radiation energy density multiplied by collector area multiplied by collector efficiency. The collector efficiency here may include the combined influence of factors such as mirror reflectivity and tracking accuracy.

[0079] In addition, if the heliostat field in the solar tower thermal power station is considered, the collector cutoff efficiency can be calculated by a more specific formula: η = (π*D^2 / 4) / (4*F*H*cosθ),

[0080] Where η represents the collector cutoff efficiency, D represents the collector diameter, F represents the total reflecting area of ​​the heliostat field, H represents the solar altitude angle, and θ represents the solar incidence angle.

[0081] It can be seen that the more accurate the DNI value is, the more accurate the total reflection area of ​​the heliostat field will be.

[0082] The data acquisition method for accurate DNI of a tower mirror field provided by the present invention was implemented and verified in the Hami solar thermal project in Xinjiang Uygur Autonomous Region. The Hami project is a hydraulic system. Different powers are required for heating water temperature in different water temperature ranges. The number of heliostats calculated according to the power and DNI values ​​is projected onto the heat absorbing tower to transfer the temperature to the water temperature. It has been verified that the heating effect of the project is very good. The number of heliostats is determined by the DNI data provided by the present invention, and the determined number of heliostats can meet the water temperature requirements at different time periods.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for acquiring accurate DNI data of a tower mirror field, characterized in that: The method comprises: S1: Quality judgment of direct radiation data: obtain the extraterrestrial normal direct radiation, the normal direct radiation of the earth's surface, the total horizontal global radiation of the earth's surface, and the scattered horizontal radiation of the earth's surface from the meteorological station, and calculate the direct beam transmittance, effective global horizontal transmittance, and effective scattered horizontal transmittance in combination with the solar zenith angle; divide the direct radiation DNI into three levels based on the direct beam transmittance, effective global horizontal transmittance, and effective scattered horizontal transmittance; S2: Obtain accurate DNI data based on the grading of direct radiation DNI; Step S1 is specifically as follows: (1) Obtain the value of the normal direct radiation on the earth's surface through the meteorological station, that is, obtain the value of the direct radiation DNI on the earth's surface. If the data is empty, wait until there is data; (2) Obtain the values ​​of the total horizontal global radiation GHI and the scattered horizontal radiation DHI of the earth's surface, and initialize the level of direct radiation DNI to 0; (3) Determine whether the effective scattering horizontal transmittance kd is greater than 0; When kd is greater than 0, the level of direct radiation DNI is changed to 1 and the process goes to step (4); when kd is not greater than 0, the process directly returns to the current level, that is, the level of direct radiation DNI remains unchanged at 0 and the process goes to step (6); in, ; kd is the effective scattering horizontal transmittance; is the diffuse horizontal radiation from the Earth’s surface; is the extraterrestrial normal direct radiation; Z is the solar zenith angle; is the extraterrestrial radiation in a plane parallel to the Earth's surface; (4) Compare the effective global horizontal transmittance kt and the direct beam transmittance kn. If kt>kn, change the level of direct radiation DNI to 3 and proceed to step (5). If kt is not greater than kn, return to the current level; that is, keep the level of direct radiation DNI unchanged at 1 and proceed to step (6). in, ; ; is the extraterrestrial normal direct radiation; is the normal direct radiation on the earth's surface; is the total horizontal global radiation at the Earth's surface; is the extraterrestrial radiation in a plane parallel to the Earth's surface; (5) Calculate the error threshold and average value; Error threshold = maximum DNI value * empirical DNI error tolerance coefficient; value=|kt-kn-kd|; The maximum DNI value refers to the maximum value of the direct radiation DNI data obtained from the meteorological station; compare the value with the error threshold, if the value is less than or equal to the error threshold, change the level of the direct radiation DNI to 6 and go to step (6); If the value is greater than the error threshold, the current Level is returned, that is, the level of direct radiation DNI remains unchanged, and the Level is still 3, and the process goes to step (6); (6) Obtain the level corresponding to all direct radiation DNIs. When the level is less than or equal to 0, output the quality label of the corresponding direct radiation DNI as bad; When the level is greater than zero and less than or equal to 3, the quality label of the corresponding direct radiation DNI is output as uncertain; When the level is greater than 3, the quality label of the corresponding direct radiation DNI is output as good; Step S2 is specifically as follows: (1) Determine the number of direct radiation DNI with quality labels of good and uncertain output in step S1; When the quantity is 0, the clear sky DNI is calculated as the final direct radiation DNI value, the quality label assigned to the final DNI value is good, and the direct radiation DNI and the quality label are output; When the quantity is equal to 1, the value and quality label of the corresponding direct radiation DNI are obtained and output; When the number is greater than or equal to 2, the quality level of the direct radiation DNI value is determined. When the number of direct radiation DNI values ​​of level 6 is greater than or equal to 1, step (2) is entered; when the number of direct radiation DNI values ​​of level 6 is equal to 0, step (3) is entered. (2) Count the values ​​and quantity of direct radiation DNI of level 6, add up the values ​​of all direct radiation DNI of level 6 and divide by the corresponding quantity to obtain the average value of direct radiation DNI of level 6, and the quality label corresponding to the average value is good; output the average value and quality label of direct radiation DNI; (3) Count the values ​​and quantity of direct radiation DNI of level 3, add up the values ​​of all direct radiation DNI of level 3 and divide by the corresponding quantity to obtain the average value of direct radiation DNI of level 3, and the quality label corresponding to the average value is uncertain; output the average value and quality label of direct radiation DNI.

2. According to the method for obtaining accurate DNI data of a tower mirror field according to claim 1, it is characterized in that: In step (5), the empirical DNI error tolerance coefficient is set to 0.05.