Radiative cooling amount prediction method based on aerosol optical depth correction

Abstract

The application discloses a prediction method for radiation refrigeration capacity by using aerosol optical thickness and precipitable water amount, comprising the following steps: S10, obtaining corresponding hourly weather data according to weather data; S20, judging whether the local latitude is greater than 33°, if yes, entering step S30, S30, calculating the local precipitable water amount (PWV H ) by using a high-latitude calculation method; if no, entering S40, S40, calculating the local precipitable water amount (PWV L ) by using a low-latitude calculation method; S50, calculating atmospheric radiation according to the calculated precipitable water amount (PWV H or PWV L ); S60, correcting the atmospheric radiation calculated in S50 according to the aerosol optical thickness in the weather data; and S70, calculating the radiation refrigeration capacity according to the atmospheric radiation corrected in S60.

Description

Technical Field

[0001] This invention relates to a method for predicting radiative cooling capacity based on aerosol optical thickness correction, belonging to the field of passive energy utilization technology. Background Technology

[0002] Radiative cooling refers to a passive cooling technology where heat from the surface of a radiative cooling material is exchanged with outer space (approximately 2.7K) through an atmospheric window (8-13μm band) via infrared radiation, thereby lowering the surface temperature of the radiative cooling material below ambient temperature. In today's advocacy for clean energy, radiative cooling technology undoubtedly has broad application prospects. In recent years, radiative cooling technology has developed rapidly, with achievements mainly focused on the preparation of radiative materials and the analysis of their cooling potential (radiative cooling capacity). However, radiative cooling capacity is affected by many factors, including geography and weather (relative humidity, aerosol optical thickness, cloud cover, atmospheric radiation, etc.), with atmospheric radiation calculation playing a crucial role in predicting radiative cooling capacity. Currently, atmospheric radiation is mostly predicted using empirical formulas, and most are only applicable to specific climate zones, lacking universality. That is, when the climate zone (or meteorological conditions) changes, the same radiation calculation (prediction) method will produce significant errors. Therefore, a more accurate and universally applicable method for calculating radiative cooling capacity will help advance the development and application of radiative cooling technology.

[0003] Calculating radiative cooling capacity requires calculating solar radiation, atmospheric radiation, the net radiative power of the radiatively cooled surface, and the non-radiative heat transfer between the surface and the environment. The atmosphere is composed of various components, including nitrogen, oxygen, carbon dioxide, water vapor, and ozone, with significant differences in emissivity and absorptivity among these components. Furthermore, solar radiation and long-wave radiation emitted from the Earth's surface undergo various physical processes in the atmosphere, such as reflection, scattering, and absorption. Therefore, atmospheric radiation is the most challenging part of the entire radiation process to calculate when predicting radiative cooling capacity. In existing publicly available technologies, Brunt et al. have explored methods for calculating atmospheric radiation. 1 Using surface water vapor partial pressure as a variable, an equivalent atmospheric emissivity calculation model was obtained under clear weather conditions, thus enabling the prediction of atmospheric radiation. (Swinbank et al.) 2Based on measured data (atmospheric radiation and ambient temperature), an empirical formula for calculating the equivalent atmospheric emissivity under clear weather conditions using ambient temperature was derived, thus enabling the prediction of atmospheric radiation. While using this empirical formula to calculate equivalent emissivity and subsequently atmospheric radiation is simple and quick, it is based on clear weather conditions. However, real-world weather conditions are not always sunny; cloudy and overcast skies also exist. When comparing the radiative cooling capacity measured under actual weather conditions with the radiative cooling capacity predicted by the empirical formula under clear weather conditions, a difference will occur. This difference is mainly due to the influence of cloud cover in the atmosphere. The composition of clouds in the actual atmosphere also plays a crucial role in the calculation of atmospheric radiation. To simplify the influence of clouds on atmospheric radiation, a cloud correction factor is typically used. 3 (Cloud Modified Factor, CMF) reflects the impact of cloud cover. Martin et al. 4 Based on cloud parameters and the equivalent emissivity under clear weather conditions, a calculation method applicable to all weather conditions was obtained. Although this method considers the impact of cloud cover on atmospheric radiation, its limitations stem from the fact that the CMF calculation method is only applicable to daytime, resulting in a higher predicted atmospheric radiation value compared to actual measurements. To obtain a more universal and accurate prediction method, this invention analyzes the properties of aerosols in clouds, revealing that aerosols have a significant impact on air quality, local hydrological conditions, and atmospheric radiation balance. The main impact on atmospheric radiation balance is through influencing the composition of clouds, thereby lowering atmospheric temperature. This explains why the predicted value is higher than the actual value. Furthermore, this calculation method has no time or spatial limitations, possessing universality and enabling large-scale prediction of radiative cooling capacity.

[0004] In summary, while existing calculation methods consider the influence of cloud cover on atmospheric radiation, they still rely on empirical formulas for equivalent atmospheric emissivity to calculate atmospheric radiation. Because these empirical formulas have temporal and spatial limitations, they can lead to significant errors in predictions across different regions. To address this issue, this invention calculates local precipitable water volume (PWV) using high- and low-latitude calculation methods. H or PWV L Then, the atmospheric emissivity of the entire atmospheric window band is calculated using precipitable water. The influence of aerosols on atmospheric radiation is also incorporated into the calculation process, making the calculation method more universal and improving the accuracy of radiative cooling prediction.

[0005] References

[0006] [1]Brunt,D.Notes on radiation in the atmosphere.I.Quarterly Journal of the Royal Meteorological Society 1932,58,389-420.

[0007] [2]Swinbank, WCLong-wave radiation from clear skies. QuarterlyJournal of the Royal Meteorological Society 1964,90,488-493.

[0008] [3]Crawford,TM;Duchon,CEAn Improved Parameterization for Estimating Effective Atmospheric Emissivity for Use in Calculating DaytimeDownwelling Longwave Radiation.Journal of Applied Meteorology 1999,38,474-480.

[0009] [4]Martin, M.; Berdahl, P. Characteristics of infrared sky radiation in the United States. Solar Energy 1984, 33, 321-336. Summary of the Invention

[0010] The purpose of this invention is to propose a highly accurate and universally applicable method for predicting radiative cooling capacity. Specifically, it involves analyzing the influence of aerosol optical thickness (AOD) on atmospheric radiation and then correcting the calculation of atmospheric radiation to improve the accuracy and applicability of radiative cooling capacity prediction.

[0011] To achieve the objectives of this invention, the following technical solution is adopted:

[0012] S10 obtains hourly weather data for the predicted area;

[0013] S20 determines whether the latitude of the region is greater than 33° based on the required prediction.

[0014] S30 If the latitude of the predicted region is higher than 33°, the local precipitable water volume (PWV) is calculated using the high-latitude calculation method (S301).H );

[0015] S40 If the latitude of the predicted region is below 33°, the local precipitable water volume (PWV) is calculated using the low-latitude calculation method (S401). L );

[0016] S50 is based on the calculated precipitation (PWV) H or PWV L ) Calculate and predict regional atmospheric radiation;

[0017] S60 corrects the atmospheric radiation calculated by S50 based on the aerosol optical thickness in the weather data.

[0018] S70 calculates radiative cooling capacity based on atmospheric radiation corrected by S60.

[0019] As a preferred example, step S30 specifically includes:

[0020] The high-latitude calculation method (S301) is based on the dew point temperature (T) in the hourly weather data obtained in step S10. d The formula for calculating precipitable water at latitudes (γ) above 33° is as follows: (The formula is incomplete and requires further context to be fully translated.)

[0021] PWV H =exp(A 0H +A 1H T d )

[0022]

[0023] r 1H =exp(-0.918H) 2 -3.107H+0.711)

[0024] A 1H =0.062exp(0.094H 2 -0.194H+0.120)

[0025] Wherein: T d Here, H is the dew point temperature, H is the altitude, γ is the latitude, and r is the latitude. 1H and A 1H A is a function of altitude. 0H It is a function of latitude and altitude.

[0026] The above formula can be simplified to:

[0027]

[0028] As a preferred example, step S40 specifically includes:

[0029] The low-latitude calculation method (S401) is based on the dew point temperature (T) in the hourly weather data obtained in step S10. d The formula for calculating precipitable water at latitudes (γ) below 33° is as follows: (The formula is incomplete and requires further context.)

[0030] PWV L =exp(A 0L +A 1L T d )

[0031]

[0032] r 1L =exp(-0.975H) 2 -3.894H+0.400)

[0033]

[0034] Wherein: T d Here, H is the dew point temperature, H is the altitude, γ is the latitude, and r is the latitude. 1L and A 1L A is a function of altitude. 0L It is a function of latitude and altitude.

[0035] The above formula can be simplified to:

[0036]

[0037] As a preferred example, step S50 specifically includes:

[0038] In step S50, the precipitable water volume (PWV) calculated based on (S30 or S40) is... H or PWV L The formula for calculating atmospheric radiation is as follows:

[0039] ε atm,λ =1-exp(a 0λ +a 1λ +a 2λ PWV 2 +a 3λ PWV 3 )

[0040] p atm =∫cosθdΩ∫I bb (λ,T amb )ε sur (Ω,λ)ε atm,λ (Ω,λ,PWV)dλ

[0041] Where: a0λ a 1λ a 2λ a 3λ ε is the fitting coefficient. sur Let I be the spectral emissivity of the radiating surface, θ be the zenith angle, and I be the spectral emissivity of the radiating surface. bb This is the spectral radiative power of a blackbody, calculated using Planck's law of blackbody radiation, with the following formula:

[0042]

[0043] Where: Planck's constant h = 6.626 × 10 -34 J·s, Boltzmann constant k = 1.381 × 10 -23 J / K, speed of light c = 2.998 × 10 8 m / s, λ is the wavelength, T amb It refers to the ambient temperature.

[0044] As a preferred example, step S60 specifically includes:

[0045] The presence of aerosols in the atmosphere lowers the temperature at the top of the atmosphere because aerosol optical thickness (AOD) represents the type of aerosol, its surface condition, and its impact on atmospheric composition. Therefore, by comparing the atmospheric radiation when the aerosol optical thickness (AOD) is zero with the atmospheric radiation when the AOD is its actual value, we can understand the influence of AOD on atmospheric radiation. For both land and sea areas, there is a strong linear relationship between aerosol optical thickness (AOD) and its effect on atmospheric radiation. For inland areas, this can be further demonstrated by:

[0046] S601 calculates the aerosol radiation effect (SWARE) based on the aerosol optical thickness (AOD) in the S10 weather data, using the following formula:

[0047] SWARE = ​​-4.3 - 20.285 × AOD

[0048] S602 calculates atmospheric radiation based on the atmospheric emissivity obtained in (S50), and corrects the atmospheric radiation based on the aerosol radiation effect obtained in (S601). The calculation formula is as follows:

[0049] p atm =∫cosθdΩ∫I bb (λ,T amb )ε sur (Ω,λ)ε atm,λ (Ω,λ,PWV)dλ

[0050] p atm.f =p atm-SWARE

[0051] Where: ε atm，λ The atmospheric emissivity ε is calculated based on (S50). sur To determine the spectral emissivity of the radiative surface, an ideal selective radiative cooling surface is used when predicting radiative cooling capacity, i.e., the emissivity in the atmospheric window (8-13 μm) band is 1, I bb This is the spectral radiative power of a blackbody, calculated using Planck's law of blackbody radiation, with the following formula:

[0052]

[0053] Where: Planck's constant h = 6.626 × 10 -34 J·s, Boltzmann constant k = 1.381 × 10 -23 J / K, speed of light c = 2.998 × 10 8 m / s, λ is the wavelength, T amb It refers to the ambient temperature.

[0054] As a preferred example, step S70 specifically includes:

[0055] S701 calculates the radiative cooling capacity (p) of the radiative cooling surface based on the weather data in S10. sur The calculation formula is as follows:

[0056] p sur =∫cosθdΩ∫I bb (λ,T sur )ε sur (Ω,λ)dλ

[0057] Where: ε sur The spectral emissivity of the radiative surface is used to predict the radiative cooling capacity. An ideal selective radiative cooling surface is used, with an emissivity of 1 at the atmospheric window (8-13 μm). bb It is the spectral radiative power of a blackbody, calculated using Planck's blackbody radiation law, as shown in the following formula.

[0058]

[0059] Where: Planck's constant h = 6.626 × 10 -34 J·s, Boltzmann constant k = 1.381 × 10 -23 J / K, speed of light c = 2.998 × 10 8 m / s, λ is the wavelength, T sur It is the surface temperature of radiation.

[0060] S702 calculates the non-radiative heat transfer (p) of the radiative cooling surface based on the weather data in S10.non-rad The calculation formula is as follows:

[0061] p non-rad =h non-rad (T amb -T sur )

[0062] h non-rad =8.3 + 2.5V wind

[0063] Among them, h non-rad It is the convective heat transfer coefficient between the surrounding environment and the radiative cooling surface, T amb and T sur These represent the ambient temperature and the surface temperature of the radiative cooling material, respectively, V wind The wind speed is at the radiating surface.

[0064] S703 The radiative cooling capacity (p) of the radiative cooling surface derived from S701. sur The non-radiative heat transfer (p) obtained from S702 non-rad S602 yields the corrected atmospheric radiation (p) atm,f ), and solar thermal radiation (p) calculated based on weather data. solar ), calculate the total radiative cooling capacity, where the formulas for calculating solar radiation and the total radiative cooling capacity are as follows:

[0065] p solar =cosθ∫I solar (λ)ε' sur (θ,λ)dλ

[0066] p net =p sur -p solar -p atm.f -p non-rad

[0067] Among them: I solar Solar spectral irradiance, θ is the zenith angle, ε' sur P is the solar radiation absorptivity. net This represents the total radiative cooling capacity.

[0068] The present invention has the following advantages and beneficial effects:

[0069] This invention incorporates the influence of aerosol optical thickness (AOD) on atmospheric radiation into the calculation of radiative cooling capacity, thereby correcting atmospheric radiation and improving the accuracy of radiative cooling capacity prediction. At the same time, the prediction method proposed in this invention has universality and can be used to predict radiative cooling capacity in different regions. Attached Figure Description

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the following accompanying drawings provide a further detailed description of the invention, wherein:

[0071] Figure 1 This is a flowchart of the present invention.

[0072] Figure 2 The precipitation potential (PWV) of Beijing in Embodiment 1 of this invention H );

[0073] Figure 3 The atmospheric radiation value of Beijing in Embodiment 1 of the present invention;

[0074] Figure 4 The aerosol radiation effect value in Beijing in Embodiment 1 of the present invention;

[0075] Figure 5 This refers to the predicted radiative cooling capacity of Beijing in Embodiment 1 of the present invention.

[0076] Figure 6 The precipitation potential (PWV) of Shanghai in Embodiment 2 of this invention L Predicted value;

[0077] Figure 7 This refers to the predicted atmospheric radiation value of Shanghai in Embodiment 2 of the present invention;

[0078] Figure 8 This refers to the aerosol radiation effect value in Shanghai in Embodiment 2 of the present invention;

[0079] Figure 9 This refers to the predicted radiative cooling capacity of Shanghai in Embodiment 2 of the present invention. Detailed Implementation

[0080] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0081] Example 1: Taking the prediction of the background area as an example.

[0082] First, hourly weather data for Beijing was obtained, including ambient temperature, dew point temperature, aerosol optical thickness, and relative humidity. Second, based on Beijing's geographical location, the background latitude is 39.8° and the altitude is 31.3 meters.

[0083] Based on Beijing's latitude, altitude, and dew point temperature, the hourly precipitation potential (PWV) is calculated using high-latitude calculation methods. H The calculation formula is as follows:

[0084] PWV H =exp(A 0H +A 1H T d)

[0085]

[0086] r 1H =exp(-0.918H) 2 -3.107H+0.711)

[0087] A 1H =0.062exp(0.094H 2 -0.194H+0.120)

[0088] Where: H is the altitude of Beijing (0.031 km), r 1H and A 1H A is a function of altitude. 0H γ is a function of latitude and altitude. γ represents the latitude of Beijing, which is 39.8°. The final calculation result is as follows: Figure 2 The figure shows the annual precipitation (PWV) for 8760 hours in Beijing. H Predicted value.

[0089] Based on the previous step, Beijing's annual precipitation is estimated at 8760 hours (PWV). H Calculate the atmospheric emissivity per hour, and then calculate the atmospheric radiation value. The calculation formula is as follows:

[0090] ε atm,λ =1-exp(a 0λ +a 1λ +a 2λ PWV 2 +a 3λ PWV 3 )

[0091] p atm =∫cosθdΩ∫I bb (λ,T amb )ε sur (Ω,λ)ε atm,λ (Ω,λ,PWV)dλ

[0092] Where: a 0λ a 1λ a 2λ a 3λ ε is the fitting coefficient. sur Let I be the spectral emissivity of the radiating surface (the spectral emissivity of an ideal selective surface is 1), θ be the zenith angle, and I be the spectral emissivity of the radiating surface. bb This is the spectral radiative power of a blackbody, calculated using Planck's law of blackbody radiation, with the following formula:

[0093]

[0094] Where: Planck's constant h = 6.626 × 10 -34 J·s, Boltzmann constant k = 1.381 × 10 -23 J / K, speed of light c = 2.998 × 10 8 m / s, λ is the wavelength, T amb This is the ambient temperature. The final calculation result is as follows: Figure 3 The figure shows the predicted atmospheric radiation for 8760 hours throughout the year in Beijing.

[0095] The aerosol impact on Beijing over 8760 hours was calculated based on aerosol optical depth (AOD) data from Beijing's weather data. The calculation formula is as follows:

[0096] SWARE = ​​-4.3 - 20.285 × AOD

[0097] Where: AOD is the aerosol optical thickness. The final calculation result of SWARE is as follows: Figure 4 The figure shows the aerosol impact effect value for Beijing over 8760 hours throughout the year. Finally, the radiative cooling capacity for 8760 hours throughout the year was calculated based on Beijing weather data, and the final result is shown below. Figure 5 As shown.

[0098] Example 2: Taking the forecast in Shanghai as an example.

[0099] First, hourly weather data for Shanghai was obtained, including ambient temperature, dew point temperature, aerosol optical thickness, and relative humidity. Second, based on Shanghai's geographical location, its latitude is 31.17° and its altitude is 7 meters.

[0100] Based on Shanghai's latitude, altitude, and dew point temperature, the hourly precipitation potential (PWV) is calculated using low-latitude calculation methods. L The calculation formula is as follows:

[0101] PWV L =exp(A 0L +A 1L T d )

[0102]

[0103] r 1L =exp(-0.975H) 2 -3.894H+0.400)

[0104]

[0105] Where: H represents the local altitude, calculated using Shanghai's altitude as 0.007 km, r 1L and A1L A is a function of altitude. 0H γ is a function of latitude and altitude. γ represents the latitude of Shanghai, which is 31.17°. The final calculation result is as follows: Figure 6 The figure shows the annual precipitation (PWV) of Shanghai for 8760 hours. L Predicted value.

[0106] Based on the previous step, Shanghai's annual precipitation is estimated at 8760 hours (PWV). L Calculate the atmospheric emissivity per hour, and then calculate the atmospheric radiation value. The calculation formula is as follows:

[0107] ε atm,λ =1-exp(a 0λ +a 1λ +a 2λ PWV 2 +a 3λ PWV 3 )

[0108] p atm =∫cosθdΩ∫I bb (λ,T amb )ε sur (Ω,λ)ε atm,λ (Ω,λ,PWV)dλ

[0109] Where: a 0λ a 1λ a 2λ a 3λ ε is the fitting coefficient. sur Let I be the spectral emissivity of the radiating surface (the spectral emissivity of an ideal selective surface is 1), θ be the zenith angle, and I be the spectral emissivity of the radiating surface. bb This is the spectral radiative power of a blackbody, calculated using Planck's law of blackbody radiation, with the following formula:

[0110]

[0111] Where: Planck's constant h = 6.626 × 10 -34 J·s, Boltzmann constant k = 1.381 × 10 -23 J / K, speed of light c = 2.998 × 10 8 m / s, λ is the wavelength, T amb This is the ambient temperature. The final calculation result is as follows: Figure 7 The figure shows the predicted atmospheric radiation for 8760 hours throughout the year in Shanghai.

[0112] The aerosol impact on Shanghai over 8760 hours was calculated based on aerosol optical depth (AOD) data from Shanghai's weather data. The calculation formula is as follows:

[0113] SWARE = ​​-4.3 - 20.285 × AOD

[0114] Where: AOD is the aerosol optical thickness, and the final result calculated by SWARE is as follows: Figure 8 The figure shows the aerosol impact effect value for Shanghai over 8760 hours throughout the year. Finally, the radiative cooling capacity for 8760 hours throughout the year was calculated based on Shanghai weather data, and the final result is shown below. Figure 9 As shown.

[0115] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting radiative cooling capacity based on aerosol optical thickness correction, characterized in that: Includes the following steps: S10 obtains hourly weather data for the predicted area; S20 determines whether the latitude of the region is greater than 33° based on the required prediction. If the predicted latitude of the region is higher than 33°, the local precipitable water volume (PWV) is calculated using high-latitude calculation methods. H ; The high-latitude calculation method described above is based on the dew point temperature T in the hourly weather data obtained in step S10. d The formula for calculating the precipitable water at latitude γ above 33°, based on altitude H, is as follows: If the latitude of the predicted region is below 33°, the local precipitable water volume (PWV) is calculated using low-latitude calculation methods. L ; The aforementioned low-latitude calculation method uses the dew point temperature T from the hourly weather data obtained in step S10. d The formula for calculating the precipitable water at latitude γ below 33°, based on altitude H, is as follows: S50 is based on the calculated precipitable water volume (PWV). H or PWV L Calculate and predict regional atmospheric radiation; S60 corrects the atmospheric radiation calculated by S50 based on the aerosol optical thickness in the weather data. S70 calculates radiative cooling capacity based on atmospheric radiation corrected by S60.

2. The method for predicting radiative cooling capacity based on aerosol optical thickness correction according to claim 1, characterized in that: In step S50, based on the calculated precipitable water volume (PWV)... H or PWV L And the zenith angle θ, the spectral radiance I of the blackbody bb Wavelength λ, ambient temperature T amb Spectral emissivity ε of the radiating surface sur Atmospheric emissivity ε atm，λ Calculate atmospheric radiation P atm The calculation formula is as follows: p atm =∫cosθdΩ∫I bb (λ,T amb )e sur (Oh,l)e atm,λ (Ω,λ,PWV)dλ.

3. The method for predicting radiative cooling capacity based on aerosol optical thickness correction according to claim 2, characterized in that, Step S60 specifically includes the following steps: S601 calculates the aerosol radiation effect SWARE based on the aerosol optical thickness (AOD) in the S10 weather data. The calculation formula is as follows: SWARE = ​​-4.3 - 20.285 × AOD; S602 corrects atmospheric radiation based on the aerosol radiation effect SWARE calculated in S601, using the following formula: p atm.f =p atm -SWARE。 4. The method for predicting radiative cooling capacity based on aerosol optical thickness correction according to claim 3, characterized in that, Step S70 specifically includes the following steps: S701 calculates the radiative cooling capacity p of the radiative cooling surface based on the weather data in S10. sur ; Based on the weather data in S10, S702 calculates the non-radiative heat transfer p of the radiative cooling surface. non-rad ; S703 The radiative cooling capacity p of the radiatively cooled surface derived from S701 sur The nonradiative heat transfer p obtained from S702 non-rad S602 yields the corrected atmospheric radiation p atm,f And solar thermal radiation p calculated based on weather data solar The total radiative cooling capacity is calculated using the following formula: p net =p sur -p solar -p atm.f -p non-rad 。

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