CN114936813A - Method for evaluating energy-saving performance of building after energy-saving modification of building outer wall - Google Patents
Method for evaluating energy-saving performance of building after energy-saving modification of building outer wall Download PDFInfo
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Abstract
The invention provides a method for evaluating the energy-saving performance of a building after the energy-saving reconstruction of an external wall of the building, which comprises the following steps: calculating the temperature coefficient delta tempi (ii) a Step two: calculating the sunshine coefficient delta j (ii) a Step three: taking a wall sample, performing energy-saving reconstruction on the wall sample, and calculating a solar spectrum reflectivity difference R before reconstruction; step four: calculating the radiation refrigerating efficiency difference P before and after the wall sample is reconstructed under the condition of no sunlight nd (ii) a Step five:calculating the extra reduced electric quantity E per month after each wall is transformed ij (ii) a Step six: and calculating the annual energy saving E of the building. The evaluation method can specifically and accurately analyze the energy-saving effect of the building after energy-saving reconstruction according to the influences of various factors such as the geographical position of the building, local sunshine conditions, weather and weather conditions, the position of a floor wall, the sunshine conditions, the energy-saving effect before and after single-side wall reconstruction and the like.
Description
Technical Field
The invention belongs to the field of building energy conservation, and particularly relates to a method for evaluating the energy-saving performance of a building after the energy-saving reconstruction of an external wall of the building.
Background
In the field of residential buildings, the energy consumption of the residential buildings at present is mainly required to be used by cooling equipment such as air conditioners, fans and the like, and in cities in the south of China, the energy consumption of an air conditioning system is even up to 40% -60% of the overall energy consumption of the residential buildings, so that the reduction of the energy consumption of the residential buildings is of great significance to the reduction of carbon dioxide emission.
Improving the heat-insulating property of residential building materials, particularly wall body structure materials of external walls, is one of the methods for reducing the energy consumption of buildings. For newly built and in-building houses, the heat insulation performance of building walls can be effectively improved by the scheme that the national state passes a mandatory standard at present and adopts a new material and a new technology and the like. However, in a large number of existing residential houses, energy-saving modification is required to improve the heat insulation performance of the residential houses, thereby reducing the carbon emission of the whole building.
For residential houses with high storage capacity, the main method at present is to paint a coating material which has ultraviolet, visible and near-infrared reflection functions and specific wave band far-infrared radiation functions on the surface of an outer wall body. On one hand, the solar radiation energy is mainly concentrated in ultraviolet light, visible light and near infrared regions, so that the blocking performance of the wall body on the solar radiation can be improved by improving the reflection effect of the wall body on the radiation energy of the part of the wavelength, and the indoor temperature rise caused by the solar radiation is reduced. On the other hand, the atmosphere has low absorption and high transmittance for infrared rays with certain specific wavelengths, and when the surface of an object is irradiated with infrared energy in the wavelength band, the infrared energy can penetrate the atmosphere until the object enters space, so that the infrared rays with the specific wavelength band are also called as an "atmospheric window". The radiation performance of the wall surface at the infrared rays of the waveband can be improved, the radiation refrigeration performance of the wall surface can be improved, and the heat transmitted to the indoor space is reduced, so that the heat insulation performance of the wall surface is further improved.
GB/T25261 and 2018 reflective thermal insulation coating for buildings provide test methods and qualified requirements for parameters such as solar reflectance, near infrared reflectance, hemispherical emissivity, thermal insulation temperature difference and the like of a coating. The standard aims at a performance test method of the coating, and the overall energy-saving effect of the building is not characterized. The heat insulation performance of the coating is not equal to the energy-saving effect of the modified building. In the actual building energy-saving transformation process, after the energy-saving transformation, the building energy-saving effect has no calculation standard and specification and can be recycled.
After the whole building is transformed in an energy-saving way, the improvement condition of the energy-saving performance of the building is influenced by various factors, which comprise: the geographical position of the building, the influence of local sunshine conditions, the influence of weather and meteorological conditions, the influence of sunshine conditions of the position of the wall body of the floor, the influence of wall surface sunlight reflectivity, radiation refrigeration efficiency and other factors. Therefore, a method for more accurately measuring and evaluating the energy-saving performance of the building before and after the energy-saving modification is needed. However, as can be seen from the foregoing analysis, the prior art lacks such a solution that can systematically analyze the energy saving effect of the building.
Disclosure of Invention
In view of the above, the invention provides a method for evaluating the energy-saving performance of a building after the energy-saving modification of an external wall of the building, aiming at overcoming the defects in the prior art.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a method for evaluating the energy-saving performance of a building after the energy-saving reconstruction of an external wall of the building comprises the following steps:
the method comprises the following steps: counting the number of days that the average air temperature of the current day of the year in the area of the monthly buildings is higher than the opening threshold temperature of the cold air, and calculating the temperature coefficient delta tempi ；
Step two: carrying out sunshine modeling analysis on the building to be reconstructed and surrounding buildings, and calculating a sunshine coefficient delta j ，δ j Representing the actual sunshine proportion of each wall body in the standard model of sunshine for 8 hours;
step three: taking a wall sample, carrying out energy-saving transformation on the wall sample, respectively testing the solar spectrum reflectivity R before and after the transformation of the wall sample, and calculating the solar spectrum reflectivity difference R before and after the transformation;
step four: respectively calculating radiation refrigeration efficiency P before and after modification of wall sample under no-sunlight condition nd And the radiation refrigerating efficiency difference P before and after reconstruction nd ；
Step five: the extra reduced electric quantity E of each month after each external wall is transformed is calculated according to the following formula ij (ii) a The unit is kW.h, and the unit is,
in the formula, SSr (x,y,i) The monthly average short wave radiation data is obtained according to longitude and latitude coordinates (x, y) of the area where the building is positioned, and the unit is W/m 2 (ii) a The step R is the solar spectrum reflectivity difference obtained by the energy-saving reconstruction of the wall body; Δ P nd Calculating the difference value of the radiation refrigeration efficiency of the wall before and after energy-saving modification under the condition of no sunlight; sd (x,y,i) The standard sunshine duration of the area where the building is located is the unit of h; s j The area of each wall body is determined by sunshine modeling analysis of the building and the surrounding buildings, and the unit is m 2 ；δ j Calculating the sunshine coefficient obtained in the step two; i is the number of months; j is the number of wall surfaces;
step six: the annual energy saving E of the building is calculated according to the following formula, wherein the unit is kilowatt-hour:
Preferably, the solar spectrum reflectivity R in the third step is tested according to the GB/T25261-2018 reflective thermal insulation coating for buildings.
Preferably, in the third step, the solar spectrum reflectivity R is measured by an ultraviolet-visible spectrophotometer at the reflectivity of 250-2500nm of the wall sample, which is expressed as
(λ), and then expressed as I according to the standard solar spectral intensity of ASTM G173-03 Reference Spectra solar (λ), performing integral calculation, wherein the calculation process is shown as formula 3:
respectively calculating the solar spectrum reflectivity R before the modification of the wall sample according to the formula Before transformation And the modified solar spectrum reflectivity R After transformation Calculating R After transformation And R Before transformation The margin of the value is R.
Preferably, the wall sample in the fourth step has radiation refrigeration efficiency P under no sunlight condition nd The calculation method of (2) is shown in formula 4:
wherein, P rad The calculation method for the radiant energy efficiency of the coating surface from inside to outside is shown as the formula 5:
wherein epsilon is the hemispherical emissivity of the coating, the test method can be tested according to the standard of GB/T25261-2018 reflective thermal insulation coating for buildings, I bb (λ,T coating ) For coating the surface at T coating The blackbody radiation intensity at temperature and the Planck blackbody radiation formula at temperature T are shown in formula 6.
wherein c is the speed of light, h is the Planck constant, T is the black body temperature, k is the Boltzmann constant,
is the wavelength;
thermal efficiency P of atmospheric radiation to wall sky The calculation method of (d) is shown in equation 7:
wherein epsilon atm The calculation method of the emissivity of the atmosphere is shown as the formula 8:
wherein t (lambda) is the transmittance of the atmosphere to infrared rays with different wavelengths;
the heat efficiency P of the atmosphere transferred to the wall body by the heat conduction and heat convection normal The calculation method is shown as formula 9:
wherein h is c Is the non-radiative heat transfer coefficient; t is atm Is the average value of three months with the highest average temperature in the middle of one year in the place of the building, T coating For measuring wall samples at T atm Temperature and surface temperature of the coating under a dark condition;
respectively calculating radiation refrigeration efficiency P before wall sample reconstruction according to formulas 4-9 Before nd transformation And improved radiation refrigeration efficiency P After nd is transformed Calculate P After nd is transformed And P Before nd transformation Δ P nd 。
Preferably, the first step is to determine the cold air opening threshold temperature T according to the self-regulation of the building 0 The unit is that the average temperature per day is higher than T in each month according to the average temperature Temp per day of the last year of the region where the building is located and the unit is that 0 Days of (1), n i And calculating the temperature coefficient delta from the equation 10 tempi ：
In formula 10, n 0i Is the total number of days per month.
Preferably, step two is determining the number of daily sunshine hours t j The unit is h, and then the sunshine coefficient delta is calculated according to the formula 11 j ：
δ j =t j And/8 formula 11.
Preferably, the evaluation method may further calculate a carbon emission reduction amount, and the calculation formula of the carbon emission reduction amount is shown in formula 12:
The invention also provides a terminal which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor executes the computer program to realize the steps of the building energy-saving performance evaluation method after the energy-saving modification of the building outer wall.
Compared with the prior art, the invention has the following advantages:
(1) the invention can specifically analyze problems, and can specifically and accurately analyze the energy-saving effect of the building after energy-saving transformation according to the influences of various factors such as the geographical position of the building, local sunshine conditions, weather meteorological conditions, the position of a floor wall body, the sunshine conditions, the energy-saving effect before and after single-side wall body transformation and the like;
(2) the invention can intuitively relate the economic benefit brought by saving electric energy of the building, the environmental benefit brought by saving carbon emission and the cost required by energy-saving modification, thereby intuitively guiding the consumer to make a decision on whether to carry out energy-saving modification;
(3) the evaluation method is simple to operate, convenient for non-professional persons to analyze and easy to popularize and apply.
Drawings
FIG. 1 is a simulation of a residential district and surrounding buildings according to an embodiment;
FIG. 2 is a sample of the wall body before modification in the example I bb (λ,T coating ) And epsilon atm (λ) I bb (λ,T atm ) Data results;
FIG. 3 is a drawing showing the P value of a wall sample before modification of a black area in the example rad－ P sky The result is;
FIG. 4 is the wall sample I after modification in the example bb (λ,T coating ) And epsilon atm (λ) I bb (λ,T atm ) Data results;
FIG. 5 is a graph showing the wall sample P after the black region is modified in the example rad－ P sky The result is;
fig. 6 is a graph of monthly power savings in the example.
Detailed Description
The following provides a specific implementation process of the building energy saving performance evaluation method after the energy saving reconstruction of the building outer wall, and the detailed description is given in combination with the accompanying drawings.
The invention will be described in detail with reference to the following examples.
The invention relates to a method for evaluating the energy-saving performance of a building after the energy-saving reconstruction of an external wall of the building, which specifically comprises the following steps:
the first step is to inquire the following weather information by a conventional method, which comprises the following steps:
longitude and latitude coordinates (x, y) of the area where the building is located;
monthly average shortwave radiation data for the area of the building: SSr (x,y,i) In the unit of W/m 2 . The physical meaning of this parameter is the amount of solar radiation reaching the earth's surface at latitude and longitude coordinates (x, y).
Daily average air temperature data of the last year of the area where the building is located: temp, in units of o C. This temperature is the temperature of the air 2 m above the surface.
Standard length of day per month of the area where the building is located: sd (x,y,i) The unit is h. This parameter, also called the peak sunshine duration, is converted to the standard test condition for the cumulative total amount of solar irradiance during said periodLower (irradiance of 1000W/m) 2 ) The length of time of duration. This parameter is usually used to characterize the local climate and to describe past weather conditions.
Step two: according to the building's own specific provisions, the cold air opening threshold temperature is determined: t is 0 In the unit of o C, i.e. when the daily average temperature (Temp) is above the threshold temperature (T) 0 ) In time, the air conditioner is started to cool in the building according to the threshold temperature (T) 0 ) And the average temperature (Temp) data of the current day and the day of the last year, counting the number of days that the temperature is higher than the threshold temperature per month, n i Wherein i represents month and takes a value of 1 to 12 months, whereby the temperature coefficient δ is calculated according to equation 1 tempi Comprises the following steps:
Wherein n is i Number of days per month the temperature is above the threshold temperature, n 0i Is the total number of days per month. As described above, the essence of energy saving modification is to reduce the cooling demand of the air conditioner by reducing the energy transferred to the indoor space from the outdoor space, thereby reducing the energy consumption of the whole building. When the temperature of the day is lower than the threshold temperature and the outdoor temperature is lower, refrigeration equipment does not need to be started, and refrigeration requirements and energy conservation are not involved. The meaning of this temperature coefficient is therefore the proportion of days per month that really have an energy saving requirement.
Step three: performing sunshine modeling analysis on the building to be reconstructed and the surrounding buildings, and determining the area (S) of each wall body j Unit m of 2 ) And the number of daily sunshine hours (t) j In the unit h), and further calculating the sunshine coefficient delta j =t j /8。
Wherein, delta j The actual sunshine proportion of each wall body in the standard model of sunshine of 8 hours is shown, and the parameters reflect the orientation of the building, and whether the floor and the surrounding buildings can block the lighting influence of the building.
Step four: taking a wall sample before modification, performing energy-saving modification on the sample, and respectively testing the wall sample before modification and the wall sample after modificationImproved solar spectrum reflectivity R Before transformation And R After transformation Calculating the solar spectrum reflectivity difference of the wall sample before and after the energy-saving reconstruction, wherein R is expressed as: Δ R = R After transformation -R Before transformation 。
Specifically, there are two methods for measuring the solar spectrum reflectivity:
the first method is to carry out the test according to the GB/T25261-2018 reflective thermal insulation coating for buildings.
The second method is to adopt an ultraviolet-visible spectrophotometer to measure the reflectivity of the wall sample at 250-2500nm
(lambda), and then the standard solar spectrum intensity according to ASTM G173-03 Reference Spectra is I solar (lambda) integral calculation is carried out, and the calculation process is shown as a formula 2.
Step five: calculating the radiation refrigeration efficiency P before and after the modification of the wall sample under the condition of no sunlight nd Δ P nd 。
Specifically, the method for calculating the radiation refrigeration efficiency under the no-sunlight condition comprises the following steps:
under the condition of no sunlight, on the one hand, the surface of the coating radiates energy from inside to outside, which is expressed as P rad . On the other hand, the atmosphere on the surface of the coating can radiate heat to the wall body at the same time, and the heat is expressed as P sky . In addition, when the surface temperature of the coating is lower than the temperature of the outside air, the heat in the air can also transfer heat to the wall body in a heat conduction and heat convection mode, and the heat is represented as P normal . Therefore, the radiation refrigeration efficiency P of the wall sample is realized without a solar kit nd The calculation method of (b) is shown in formula 3.
The radiation energy of the coating surface from the inside to the outside is as follows:
Here, epsilon is the hemispherical emissivity of the coating, and the hemispherical emissivity test method can be used for testing according to the GB/T25261-2018 reflective thermal insulation coating for buildings standard;
for coating the surface at T coating Black body radiation intensity at temperature. The Planck blackbody radiation formula at the temperature T is shown in equation 5.
Where c is the speed of light, h is the Planckian constant, T is the black body temperature, k is the Boltzmann constant,
is the wavelength.
The heat radiated to the wall by the atmosphere is as follows:
Wherein the content of the first and second substances,
the emissivity of the atmosphere is given by the following values:
Here, t (λ) is the transmittance of the atmosphere for infrared rays of different wavelengths.
The heat transferred to the wall body by the atmosphere through heat conduction and heat convection is as follows:
In the formula 8, h c Is the non-radiative heat transfer coefficient; t is atm Is the average value of three months with the highest average temperature in the middle of one year in the place of the building, T coating For measuring wall samples at T atm Temperature and surface temperature of the coating under the condition of keeping out of the sun;
respectively calculating radiation refrigeration efficiency P before wall sample reconstruction according to formulas 3-8 Before nd transformation And improved radiation refrigeration efficiency P After nd is transformed Calculate P After nd is transformed And P Before nd transformation Δ P nd 。
Step six, evaluating and determining the refrigeration efficiency and EER of the air conditioner in the building, calculating the electric quantity difference value which can be saved by each wall body every month before and after modification, and calculating the electric quantity difference value E ij It is shown that where i is the month and j is the jth wall. As described above, the energy-saving transformation can simultaneously realize two energy-saving effects, on one hand, the energy-saving transformation can improve the reflection efficiency of the wall body to sunlight, which can reduce the energy incident into the wall body; on the other hand, the energy-saving modification can improve the radiation refrigeration efficiency of the wall surface and further reduce the energy entering the wall body. Thus, E ij Can be expressed as:
By the method, when the external temperature is higher than the threshold temperature, under the consideration of the influences of various factors such as the geographical position of the building, the influence of local sunshine conditions, the influence of weather and weather conditions, the influence of sunshine conditions of the positions of doors and windows of the floor, the improvement condition of the reflectivity of the wall surface after energy-saving transformation, the improvement condition of the heat dissipation effect of the wall surface and the like, the reduction of the energy actually incident to the room can be calculated. If the air conditioner has good refrigeration efficiency and the equipment can normally work, the refrigerating capacity of the air conditioner to be output to the indoor in equal amount can be reduced when the indoor temperature is constant, and therefore the electric energy saved by the building every month after energy-saving transformation can be calculated.
And step seven, calculating the annual energy saving (E, unit kilowatt-hour) of the building according to the condition of each wall body every month, and further calculating the reduction of carbon emission caused by electricity saving. The annual electricity saving quantity of the building can be obtained by accumulating and calculating wall bodies in each month, and a calculation formula is shown as a formula 10.
The reduction of carbon emissions is mainly obtained by converting the equivalent saving of electric energy, and is calculated by reducing the carbon dioxide emission by 0.785 kg per 1 degree of electricity saving. Therefore, after the energy-saving reconstruction of the building, the carbon emission amount can be reduced due to the reduction of the electric energy consumption
。
Examples
Taking a certain residential district in Heizhou city as an example, the calculation process of the method is specifically explained as follows:
step one, the longitude and latitude coordinates of the area are 33 o N，120 o E, 2020 sun intensity data, monthly standard sun duration data, and daily average temperature data are shown in tables 1 and 2.
TABLE 1 Table of 2020 sunshine radiation data and standard sunshine duration data of Changzhou city
| Month of the year | Monthly average short-wave radiation intensity (SSr, W/m) 2 ) | Standard duration of the sun (Sd, h) |
| 1 | 81.89 | 69.65 |
| 2 | 128.65 | 103.22 |
| 3 | 152.91 | 129.95 |
| 4 | 205.3 | 169.15 |
| 5 | 219.38 | 186.73 |
| 6 | 197.83 | 163.09 |
| 7 | 159.41 | 136.13 |
| 8 | 183.35 | 156.52 |
| 9 | 181.6 | 150.07 |
| 10 | 155.29 | 132.17 |
| 11 | 109.23 | 90.01 |
| 12 | 102.56 | 87.87 |
TABLE 2 data sheet of mean temperature in 2020 year in Changzhou city
Step two, the most comfortable temperature for people is 20-24 ℃, so the temperature in the building is set to be higher than 25 DEG C o When C, the air conditioner will be turned on to cool, so setting T 0 =25 o C, the number of days above the temperature threshold per month and the temperature coefficient were calculated from these, and the results are shown in table 3.
TABLE 3 monthly T>T 0 Number of days and temperature coefficient
| Month of the year | T>T 0 Days (sky) | Temperature coefficient (delta) temp ） |
| 1 | 0 | 0.00 |
| 2 | 0 | 0.00 |
| 3 | 2 | 0.06 |
| 4 | 6 | 0.20 |
| 5 | 26 | 0.84 |
| 6 | 28 | 0.93 |
| 7 | 28 | 0.90 |
| 8 | 31 | 1.00 |
| 9 | 26 | 0.87 |
| 10 | 3 | 0.10 |
| 11 | 1 | 0.03 |
| 12 | 0 | 0.00 |
And step three, analyzing the sunshine condition of the building of the residential area floor by utilizing modeling simulation software according to the actual position of the local building, specifically, a large number of high-rise buildings are arranged around the residential area, and the lighting is influenced by the shielding among the buildings, so that the whole residential area and the surrounding buildings need to be analyzed together, and the result is shown in fig. 1. The cell to be modified is a No. 10 building, and the sunshine coefficients of the wall bodies at different floors are calculated according to the simulation result, as shown in Table 4.
TABLE 4 sunshine coefficient and wall surface area
| Window face ID | Solar factor (delta) j ） | Wall surface area (S) j ，m 2 ） |
| 1 (North) | 0.94 | 5287.00 |
| 2 (east) | 0.31 | 1465.00 |
| 3 (south) | 0.06 | 5310 |
| 4 (xi) | 0.19 | 1340.00 |
| 5 (Top) | 0.69 | 1200.00 |
And step four, according to field sampling, the original paint layer on the surface of the building is partially aged and delaminated. A part of paint surface samples are obtained on site and tested to obtain the solar spectrum reflectivity of 0.53 and the hemispherical emissivity of 0.61. The pre-reforming mode of the building is to re-brush the surface of the old wall with commercially available EASYTO metal thermal barrier coating products. After the original paint surface is coated again, the solar spectrum reflectivity is measured to be 0.9, and the hemispherical emissivity is measured to be 0.88.
The temperature in 6, 7 and 8 march every year in Changzhou city is highest, the requirement for heat insulation in march is also highest, the average value of the temperature is about 30 ℃, therefore, T is set here atm =30 ℃. Measured at this temperature to give T coating 25.2 ℃ and the temperature difference reaches 4.8 ℃.
Step five, before and after the transformation according to the parameters,
the difference value of the sunlight reflectivity of the wall sample is 0.37; wall sample before reconstruction I bb (λ, T coating )
And e atm (λ) I bb (λ, T atm ) Data results are shown in FIG. 2, P rad -P sky The results are shown in FIG. 3. Modified wall sample I bb (λ, T coating ) And epsilon atm (λ) I bb (λ, T atm ) Data results are shown in FIG. 4, P rad -P sky The results are shown in FIG. 5. From this, P of the modified wall sample can be finally calculated nd Can be made up by 98.1W/m 2 Lifting to 155.3W/m 2 The difference value before and after the transformation reaches 57.2W/m 2 。
And step six, the local air conditioner has primary energy consumption, the EER is 3.6 according to the national standard, and the electricity charge which can be saved each month after the energy-saving transformation of the whole building is calculated. Considering the factors of dissatisfaction of residents in the building, air conditioning and cooling of not all residents in summer, etc., conservative estimation is performed according to 50% usage rate, and monthly energy saving effect is shown in table 5 and fig. 6.
TABLE 5 saving of electricity monthly
| Month of the year | Saving electricity (kW.h) |
| 1 | 0 |
| 2 | 0 |
| 3 | 904.2 |
| 4 | 4270.3 |
| 5 | 20542.2 |
| 6 | 18815.3 |
| 7 | 13541.5 |
| 8 | 18552.2 |
| 9 | 15336.2 |
| 10 | 1390.2 |
| 11 | 277.6 |
| 12 | 0 |
Step seven, if the whole building is subjected to energy-saving reconstruction, calculating the annual energy saving of the building:
the energy-saving and energy-saving method is characterized in that the energy-saving and energy-saving method is used for =93629.7 kW.h, namely, about 94000 degrees of electricity can be saved each year, the direct economic benefit brought by electricity saving can reach 9 ten thousand yuan each year, about 7.4 tons of carbon dioxide emission can be reduced each year, and one tree can absorb about 18.3 kilograms of carbon dioxide each year, so that about 4030 trees are planted in addition after the energy-saving and energy-saving modification of buildings.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the invention, and any modifications, equivalents, improvements and the like that are made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. A method for evaluating the energy-saving performance of a building after the energy-saving reconstruction of an external wall of the building is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: counting the number of days that the average air temperature of the building per month on the same day of the last year in the region where the building is located is higher than the cold air opening threshold temperature, and calculating the temperature coefficient delta tempi ；
Step two: carrying out sunshine modeling analysis on the building to be reconstructed and surrounding buildings, and calculating a sunshine coefficient delta j ，δ j Each wall is shown inThe actual sunshine proportion received in the 8-hour sunshine standard model;
step three: taking a wall sample, carrying out energy-saving transformation on the wall sample, respectively testing the solar spectrum reflectivity R before and after the transformation of the wall sample, and calculating the solar spectrum reflectivity difference R before and after the transformation;
step four: respectively calculating radiation refrigeration efficiency P before and after modification of wall sample under no-sunlight condition nd And the radiation refrigerating efficiency difference P before and after reconstruction nd ；
Step five: calculating the extra reduced electric quantity E per month after each wall body is transformed according to the following formula ij (ii) a Unit is kW.h:
in the formula, SSr (x,y,i) The monthly average short wave radiation data is obtained according to longitude and latitude coordinates (x, y) of the area where the building is positioned, and the unit is W/m 2 (ii) a The red light is the solar spectrum reflectivity difference obtained by the energy-saving reconstruction of the wall body in the step three; Δ P nd Calculating the difference value of the radiation refrigeration efficiency of the wall before and after energy-saving modification under the condition of no sunlight; sd (x,y,i) The standard sunshine duration of the area where the building is located is the unit of h; s j The area of each wall body is determined by sunshine modeling analysis of the building and the surrounding buildings, and the unit is m 2 ；δ j Calculating the sunshine coefficient obtained in the step two; i is the number of months; j is the number of wall surfaces;
step six: the annual energy saving E of the building is calculated according to the following formula, wherein the unit is kilowatt-hour:
2. The method for evaluating the energy-saving performance of the building after the energy-saving reconstruction of the outer wall of the building according to claim 1 is characterized in that: and in the third step, the solar spectral reflectivity R is tested according to the standard of GB/T25261-2018 reflective thermal insulation coating for buildings.
3. The method for evaluating the energy-saving performance of the building after the energy-saving reconstruction of the outer wall of the building according to claim 1 is characterized in that: in the third step, the solar spectrum reflectivity R is measured by an ultraviolet-visible spectrophotometer at the reflectivity of 250-2500nm of the wall sample, which is expressed as
And then expressed as the standard solar spectral intensity according to ASTM G173-03 Reference Spectra
And performing integral calculation, wherein the calculation process is shown as formula 3:
respectively calculating the solar spectrum reflectivity R before the modification of the wall sample according to the formula Before transformation And the modified solar spectrum reflectivity R After transformation Calculating R After transformation And R Before transformation The margin of the value is R.
4. The method for evaluating the energy-saving performance of the building after the energy-saving reconstruction of the outer wall of the building according to claim 1 is characterized in that: the wall sample in the fourth step has radiation refrigeration efficiency under the condition of no sunshine
The calculation method of (2) is shown in formula 4:
wherein, P rad The calculation method for the efficiency of the energy radiated from the coating surface from the inside to the outside is shown in formula 5：
wherein epsilon is the hemispherical emissivity of the coating, the test method can be used for testing according to the standard of GB/T25261-2018 reflective thermal insulation coating for buildings,
for coating the surface at T coating Blackbody radiation intensity at temperature, planck blackbody radiation formula at temperature T is shown as formula 6:
wherein c is the speed of light, h is the Planck constant, T is the black body temperature, k is the Boltzmann constant,
is the wavelength;
thermal efficiency P of atmospheric radiation to wall sky The calculation method of (2) is shown in formula 7:
wherein epsilon atm The calculation method of the emissivity of the atmosphere is shown as the formula 8:
wherein the content of the first and second substances,
the transmittance of the atmosphere to infrared rays with different wavelengths;
heat transfer effect of atmosphere to wall body in heat conduction and heat convection modesRate P normal The calculation method is shown as formula 9:
wherein h is c Is the non-radiative heat transfer coefficient; t is atm Is the average value of three months with the highest average temperature in the middle of one year in the place of the building, T coating For measuring wall samples at T atm Temperature and surface temperature of the coating under a dark condition;
respectively calculating the radiation refrigeration efficiency of the wall sample before modification according to the formulas 4 to 9
Before transformation And improved radiation refrigeration efficiency
After transformation Calculating
After transformation And
before transformation Δ of
。
5. The method for evaluating the energy-saving performance of the building after the energy-saving reconstruction of the outer wall of the building according to claim 1 is characterized in that: step one, determining the opening threshold temperature T of the cold air according to the self regulation of the building 0 The unit is that the average temperature of the day of the month is higher than T according to the average temperature Temp of the day of the year in the area where the building is located and the unit is that 0 Days n i And calculating the temperature coefficient delta from the equation 10 tempi ：
in formula 10, n 0i Is the total number of days per month.
6. The method for evaluating the energy-saving performance of the building after the energy-saving reconstruction of the outer wall of the building according to claim 1 is characterized in that: step two, determining the daily sunshine duration t j The unit is h, and the sunshine coefficient delta is calculated according to the formula 11 j ：
δ j =t j /8 formula 11.
7. The method for evaluating the energy-saving performance of the building after the energy-saving reconstruction of the outer wall of the building according to claim 1 is characterized in that: the evaluation method further comprises the step of calculating the reduction amount of the carbon emission, wherein the calculation formula of the reduction amount of the carbon emission is shown as a formula 12:
8. A terminal, characterized by: the method comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor executes the computer program to realize the steps of the method for evaluating the energy-saving performance of the building after the energy-saving modification of the outer wall of the building according to any one of claims 1 to 7.
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