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Calculation and Analysis Method of Sunpower Solar Energy Saving Rate

Views: 6     Author: Site Editor     Publish Time: 2019-06-22      Origin: Site

Taking the solar energy air source coupled hot water system as a sub-project of the Guangxi Environmental Protection Department's dilapidated housing reform project, the annual energy saving rate of solar energy was analyzed and calculated in detail. From the calculation process and calculation basis, this calculation method is more scientific and reliable, and has important reference significance for the analysis and calculation of energy saving and emission reduction using solar thermal system.


Guangxi belongs to the south subtropical monsoon climate with a mild climate. The average annual sunshine duration is 1600 h. The average annual solar radiation dose is about 4578 MJ/m2. The solar energy resources are very rich, and the potential for solar energy is huge. At present, the society is promoting and popularizing the centralized supply of solar air source coupled hot water system. However, the solar air source coupled hot water system must first calculate and analyze the energy saving amount in the design and project declaration, in the solar thermal application system. There is no scientific and reliable calculation method for calculation and calculation of energy saving. Therefore, this paper takes the solar energy source coupled hot water system as a sub-project of the renovation project of the renovation of the old house of Guangxi Environmental Protection Department. As an example, practice a new method of computational analysis.


1 Overview of the project

The Guangxi Environmental Protection Department's dilapidated housing reform project is to demolish the original low, short and old staff residential building, and build a 33-storey high-rise building on the original land. The project address is No. 78, Minzu Avenue, Nanning, Guangxi. In response to the national call for energy conservation and emission reduction, the project uses a form of renewable energy building application, solar air source coupled hot water system, the centralized hot water system provides a total of 186 households with about 651 people daily hot water demand. The daily per capita hot water quota is designed to be 80 L, the service time is 24 h, and the total daily hot water consumption in the maximum hot water season is 52 m3. The hot water project has installed a total of 2,600 solar vacuum heat collecting tubes, with a total of 60 air source heat pumps, and the energy saving effect is extremely remarkable.

2 Calculation and analysis of annual energy saving rate of solar collector system in hot water system

2.1 The working process of the hot water system

The solar air source coupled hot water system is fully automated controlled by the control of the automatic control module. When there is sufficient solar radiation, the hot water system preferentially uses solar energy to obtain domestic hot water. When the rainy weather or solar radiation is insufficient, the air source heat pump is activated to use as an auxiliary heat source to obtain domestic hot water.

2.2 Definition of energy saving rate

The annual energy saving rate of the solar water heating system refers to the solar water heating system in the annual operation, compared with the conventional hot water heating mode, the electricity saved by the solar heat collecting system (excluding the electricity saved by other auxiliary heat sources) accounts for the conventional hot water. The ratio of the amount of electricity consumed by the heating method.

2.3 Calculation of thermal efficiency

2.3.1 Thermal efficiency of solar collector systems

The thermal efficiency calculation method of the solar heat collecting system is exemplified by a centralized solar heat collecting system equipped with a circulating water pump. Generally, the solar heat collecting system heats the hot water from the initial temperature to the set temperature under the solar irradiation, and the solar heat collecting system only The circulating water pump consumes a small amount of electric energy, and no other equipment consumes electric energy. The rated input power of the circulating water pump equipped with this system is 0.265 kW, and the time required for circulating 1000 kg of water that has risen by 35 °C is 0.128 h. 0.034 degrees. Therefore, the actual heat value of the centralized solar collector system equipped with a circulating water pump is:

35000/0.034=1029411.76 kCal/degree;

The comprehensive thermal efficiency is: 1029411.76/860=119699%

2.3.2 Thermal efficiency of electric water heaters

The conventional heating equipment for domestic residents' hot water in the area is an electric water heater installed independently by each household. The working principle of the electric water heater is actually resistance heating. The thermal efficiency of the electric water heater is 95%, that is, the energy efficiency ratio is 0.95.

2.4 Energy saving rate calculation

2.4.1 Uniform condition setting for hot water calorie calculation

Nanning is located to the south of the Tropic of Cancer. Its geographical coordinates are 108°22′ east longitude and 22°48′ north latitude. It has plenty of sunshine, abundant rainfall, little frost and no snow, mild climate, short summer and long winter, and the annual average temperature is 21.6 °C. The coldest January in winter averages 12.8 °C, and the hottest summer in July and August averages 28.2 °C. The average annual rainfall is 1304.2 mm and the average relative humidity is 79%. It is ideal for sightseeing all year round. Subtropical monsoon climate.


According to the climate characteristics of Nanning, the demand for domestic hot water is divided according to summer, winter and transitional seasons. Summer is from May to September, totaling 153 days, the hot water demand coefficient is 0.6; winter is 1, 2, and December, totaling 90 days, the hot water demand coefficient is 1; the transition season is 3, 4, 10, and November. For a total of 122 days, the hot water demand factor is 0.8.

2.4.2 Calculation of annual heating demand and energy consumption of ordinary electric water heaters

According to this method, the heat collection of each ¢58×1800 solar vacuum heat collecting tube in each month is compiled into a table.


It is calculated that the total heat collection of each ¢58×1800 solar vacuum heat collecting tube is 91.313 kW?h. In this energy-saving project, a total of 2,600 solar vacuum heat collecting tubes of this specification were installed in the entire community, and the total heat collection for the whole year was 237,138 kWh?h.

To collect this heat, the energy consumed by the solar collector system is:

2374138÷119699%=198.34(kW?h)

That is, the annual energy saving of the solar collector system of this project is:

2374138-198.34=237215.46(kW?h)

The annual energy saving rate of the solar collector system of this project is:

Annual energy consumption of solar collector system 年 annual electricity consumption of conventional hot water heating mode × 100%

=237215.46÷563980.5×100%

=42.1%

The annual energy saving rate of the solar collector system of this project is 42.1%.

2.5 Error Analysis

From the calculation process and calculation basis, the calculation method of the annual energy saving rate of the solar collector system of this project can be called “daily calculation method”. The error of the calculation analysis result of the daily calculation method exists, and the magnitude of the error is mainly related to several parameters.

(1) The solar radiation quantity data is obtained by reference to the “China Meteorological Radiation Data Yearbook (2001)”. The annual climate will change more or less with that of 2001, but usually the amount is not large.


(2) The solar collector heat collecting tube collects 92% of the heat efficiency, which is the experimental data provided by the manufacturer of the solar vacuum collecting tube. This parameter can also be measured by experiments;


(3) The heat loss rate of pipelines and water tanks. In actual engineering, if the insulation measures are done well, the heat loss rate can be directly reduced.


(4) The total amount of actual heat used by users each year. The actual heat used per year is related to the season and climate, so the heat coefficient is different for each season.

2.6 General calculation analysis method

The conventional calculation and analysis methods are described in the literature [1].

3 Conclusion

Under the pressure of the energy crisis, the state vigorously promotes the development and utilization of renewable clean energy. Among them, solar thermal application technology is one of the most mature and widely used technologies in the development and application of renewable clean energy. Using the “daily calculation method” to calculate and analyze the annual energy saving rate of solar thermal application system, compared with the conventional method, from the calculation process and calculation basis, this calculation method is scientific and reliable, and has strong persuasive power. It has important reference significance for the analysis and calculation of energy saving and emission reduction using solar thermal application system.


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