Fan Wensheng 1 Zhang Yu 2
(1. Zibo City Planning and Design Institute, Zibo, Shandong 255000, China
2. Ankerui Electric Co., Ltd., Shanghai 201801)
Abstract: As a representative of new energy, photovoltaic power generation project is China's sustainable energy strategy planning. The integration of photovoltaic building has a very important demonstration significance for promoting the development of solar energy utilization and photovoltaic cell module industry, which can fully promote the photovoltaic industry. Development, large-scale employment, its economy, environmental protection and other benefits are significant. Taking the actual project as an example, the system composition of the whole photovoltaic power station is briefly introduced. The power generation and economic benefits of the photovoltaic power station are analyzed, and the project risks are analyzed.
Key words: photovoltaic power generation; photovoltaic system; project power generation; project revenue analysis
1. Introduction Photovoltaic building integration is a new concept for the application of solar power. In short, solar photovoltaic grids are installed on the outer surface of the building's enclosure to provide electricity. The photovoltaic cell module is perfectly integrated with the building, the power generation can be integrated into the power grid, saving resources and obtaining economic benefits, and the PV power plant investment is saved, the effect is fast, the running cost is low, and the capital risk is small.
This design project is to build a rooftop solar photovoltaic building project using the idle roof of a factory building in Jiangyin. The solar power plant is perfectly integrated with the building itself, based on the most advanced photovoltaic building integration technology.
The total installed capacity of the project is 66.3kWp (the peak power of the photovoltaic power plant battery components), using high-efficiency polysilicon module panels with a service life of more than 25 years; all the electricity generated by the photovoltaic system is incorporated into the nearest 400V substation. Used in parallel connection (configure two-way metering meter).
The actual installed capacity of the project is 66.3kWp, and the average annual power generation capacity is 63,300 kWh. The average annual saving of standard coal is 24.64 tons, and the annual CO2 section is 8.84 tons.
2. Project Overview
2.1 Geographical location Jiangyin City is located at 31° north latitude and 120° east longitude. It belongs to the north subtropical monsoon humid climate with an annual average temperature of 16.7 °C and annual rainfall of 1040.7 mm. The terrain is flat and the average elevation is about 6 meters. The total annual solar radiation is 115.7 kcal/cm 2 . The total amount of solar radiation in a year is the highest in July and August, respectively 13.5 kcal/cm 2 and 13.7 kcal/cm 2 ; the lowest in December and January, both 6.3 kcal/cm 2 .
2.2 Building type and power station scale The office building of this design project is oriented from north to south. The roof of the building is made of concrete cement roof. The east, west and south sides are not covered by obvious high-rise buildings. The roof load meets the requirements. Solar photovoltaic modules are erected on the roof.
According to the relevant drawings and on-site surveys provided by customers, the total installed capacity of distributed photovoltaic power plants on the roof of the plant is 66.3kWp.
3. Technical solution design
3.1 system composition
Figure 1 Principle structure of grid-connected photovoltaic power station system
3.2 Component installation method The assembly installation angle is different, the radiance per square meter will be different, and the on-site PV module is installed on the cement roof at an inclination angle of about 25 degrees.
3.3 System main components Photovoltaic grid-connected power generation system consists of solar cell components, string-type photovoltaic grid-connected inverters, AC combiner boxes, AC grid-connected cabinets and system communication monitoring devices.
The main components of the 66.3kWp grid-connected photovoltaic power station are as follows: 260 HR-255Wp crystalline silicon components for solar modules; anodized aluminum alloy materials for brackets; 3 inverters for photovoltaic grid-connected inverters; One AZX-H combiner box; the AC grid-connected cabinet adopts one AZG-B grid-connected cabinet; the system communication monitoring device is designed to adopt the photovoltaic power station integrated monitoring system.
3.3.1 According to the total installed capacity and the actual situation of each district roof, the PV power plant in this period is 66.3kWp, and 260 255WP components should be selected. The solar cell module should have very good weather resistance and can operate stably and reliably for a long time under harsh outdoor conditions, and should have high conversion efficiency and low cost at the same time. Choosing high-quality and efficient solar modules is one of the keys to reliable operation of grid-connected photovoltaic power plants and increase power generation.
The components of this project adopt HR-255Wp series: this component has a uniform appearance, light and sturdy structure, and good wind and snow resistance. The frame has a water tank to prevent water from accumulating in the components and to prevent the frame from bursting. The border oxide film is thicker and can meet the requirements of use under harsh conditions, especially the salt fog climate.
3.3.2 The inverter adopts ASI series photovoltaic grid-connected inverter. The ASI Series is designed to be safer and more reliable with a high efficiency, small form factor low frequency isolation transformer design and high performance low power power devices.
The parameters of ASI series photovoltaic grid-connected inverter are shown in Table 1.
3.3.3 AC combiner box In the photovoltaic power generation system, a large number of photovoltaic cell modules are serially combined to achieve the required voltage and current values ​​to optimize power generation efficiency. The main function of AZX-H series intelligent photovoltaic combiner box is to make the first-level convergence of the input of the photovoltaic cell array, to reduce the connection of the photocell array to the inverter, optimize the system structure, and improve reliability and maintainability.
3.3.4 Metering device The metering device has a special metering provided by the power supply bureau, with communication function, and needs data uploading. The metering device is installed in the AC power distribution cabinet. Leave the installation location and secondary wiring and communication line in the AC power distribution cabinet.
3.3.5 System Communication Monitoring Device The grid-connected photovoltaic power generation system monitoring software is the remote monitoring software for grid-connected photovoltaic power generation of Ankerui Electric Co., Ltd., which uses fieldbus technology, Ethernet technology, wireless communication technology and computer technology. Based on the monitoring, control and management system developed by advanced technology, it has configuration function, control function, alarm function, debugging diagnosis, report and curve function, and the system is easy to expand. The software integrates the photovoltaic power generation system and the power management system monitoring function, and performs remote real-time monitoring, statistical analysis, and historical event recording on the photovoltaic power generation system. At the same time, the power distribution monitoring system can be directly connected for centralized monitoring.
This project can install a background monitoring system in the office. Monitoring, control and management of solar power systems through photovoltaic power generation system monitoring software.
4. Before installing and designing the PV module, mark the position of the base preform and place the base preform. The photovoltaic bracket is mounted and fixed on the base preform. The photovoltaic support is designed according to the requirements of Class 10 typhoon and 50 years of snow load. In combination with local solar radiation conditions, solar energy is utilized to the maximum extent. The installation angle of PV modules in this project is 25 degrees. The project uses 20 255W components to form a string, a total of 13 strings of PV strings, of which 2 20KW inverters are connected to 4 strings of components. One 25KW inverter is connected to 5 strings of PV modules. After all the strings are connected to the inverter, the cable from the output of the inverter is connected to the AC combiner box.
The solar panel metal holder is connected to the original lightning protection net on the roof for protection. Prevent direct lightning strikes on the solar panel array equipment. The solar cell array is connected to the string inverter through a cable, and the inverter adopts a pressure sensitive protection device to effectively avoid damage caused by lightning strikes.
The power distribution room mainly realizes various protection and metering, access transformers, and is connected to the grid through the AC power distribution cabinet in the low-voltage room. The power distribution room should be kept clean and tidy, and the ventilation and heat dissipation environment should be cleaned. The dust and dirt on the equipment should be cleaned up in time. Increase the AC and network cabinets at the side of the transformer low voltage cabinet. The busbar of the AC grid-connected cabinet is spliced ​​with the busbar of the transformer low-voltage cabinet, and an incoming circuit breaker is installed in the cabinet for line protection.
5. Analysis of project power generation and social benefits
5.1 System efficiency The efficiency of photovoltaic power generation system is affected by many factors, including: local temperature, pollution, PV module installation inclination, azimuth, annual utilization of photovoltaic power generation system, solar cell module conversion efficiency, surrounding obstacle shading, inverter loss And photovoltaic power line losses. After simplifying the calculation method, the total efficiency of the photovoltaic power generation grid-connected system is composed of the following parts.
1) Photovoltaic power plant covers a large area, the DC side voltage is high, the current is small, and the wire has a certain loss. According to the specification, the loss value here is designed according to 2%.
2) There are certain characteristic differences between a large number of solar cell modules, and the coefficient of inconsistency loss is 3%.
3) Considering that the surface of the solar cell module still has a certain amount of dust accumulation even after cleaning, the occlusion loss coefficient is 4%.
4) Photovoltaic grid-connected inverter conversion efficiency: the ratio of the AC power output of the PV grid-connected inverter to the DC input power, and the efficiency is calculated as 96%.
5) The solar radiation loss coefficient cannot be used in the morning and evening at 4%.
6) The temperature influence factor of the photovoltaic cell is considered at 1.8%.
7) Considering the impact of local climate change and various unfavorable factors, according to experience, the unforeseen factor loss factor is 6.8198%.
8) The total system efficiency is: η total = η1 × η2 × η3 × η4 × η5 × η6 × η7,
= (1-2%) × (1-3%) × (1-4%) × 96% × (1-4%) × (1-1.8%) × (1-6.8198%)
≈77%
5.2 Calculation of power generation
5.2.1 Solar Moon Radiation According to the information provided in the China Meteorological Radiation Data Book, the monthly solar radiation data in Jiangsu Province is shown in Table 2:
5.2.2 Annual power generation calculation Power generation in the first year = installed capacity X Irradiance X System efficiency Estimate the amount of electricity generated by the amount of solar radiation.
a, photovoltaic array efficiency η1:
The ratio of the actual DC output power to the nominal power of the PV array at 1000 W/m2 solar radiation intensity.
The loss of PV arrays during energy conversion and transmission includes: 1 Component matching loss: about 4% loss for carefully designed and carefully constructed systems;
2 Solar radiation loss: including low and weak solar radiation loss on the surface of the component and unusable, 5%;
3 Deviation from maximum power point loss: such as temperature influence, maximum power point tracking (MPPT) accuracy, etc. Value 2-4%;
4 DC line loss: According to relevant regulations, it should be less than 1-3%.
Take: η1=96%×95%×98%×98%=87.6%
b, the conversion efficiency of the inverter η2:
The efficiency of the general grid-connected inverter is above 94%, taking 94%; the ratio of the AC power output by the inverter to the DC input power.
C, AC grid-connected efficiency η3:
If it is not transmitted through the high voltage grid, the efficiency may be η3=1
The total system efficiency η = η1 × η2 × η3 = 87.6% × 94% × 1 = 82.3%
The first year of power generation (EP) of the system = PAS × HA × η × 365
PAS: Solar PV array capacity
HA: local average solar radiation (kwh/m2/day)
η: Total system efficiency The photovoltaic power plant components of this project are installed at 25 degrees south of the cement roof. Calculated according to the 25-year calculation of photovoltaic panels, taking into account the loss of photovoltaic panels and related components, the remaining 24 years are calculated according to the annual 0.8% decrement. The average annual power generation of this project is 63,300 kWh, and the total power generation in 25 years is about 1,582,800 kWh.
5.2.3 Economic Benefits and System Environmental Benefits According to the above-mentioned power generation, combined with the company's industrial electricity prices and state subsidies, the project has considerable economic benefits during the 25-year life cycle, specifically: the total project The investment is about 8 yuan / W, and the total investment amount is about 530,000 yuan. According to 90% of photovoltaic power generation, 10% of the Internet. The annual total annual income is 86,100 yuan. The annual investment yield is 16.24%.
Economic benefits: Based on the power generation and the construction cost of the input combined with the actual power consumption, without considering the factors such as the increase in electricity costs and equipment maintenance and replacement, it is estimated that the investment cost will be recovered around 6.16 years, and the economic benefit generated in 25 years is about 2.0383 million. yuan.
Environmental benefits: According to the current China's power generation coal consumption is calculated at an average of 390 grams of standard coal / degree. It is estimated that the total standard coal saved in 25 years: 1,582,500 degrees × 390 grams / kW = 616 tons of standard coal. It is estimated that 25 years of emission reduction CO2: 1582500kWh × 1.4kg CO2 / kWh = 221 tons, reducing emissions of SO2 by about 12.37 tons, reducing emissions of NOx by about 4.29 tons, with greater environmental and social benefits.
5.3 Social Benefits The solar energy reserves in Jiangyin are abundant, and the development of solar energy has significant social benefits. Not only can it improve the irrationality of the energy structure, but also increase the share of new energy in the power grid. At the same time, it can alleviate the tension of local power supply and demand, and promote local labor and employment, which has far-reaching significance for the development of the local economy.
6. Project risk analysis The main equipment of the photovoltaic system is of good quality, in which the life of the solar panel is more than 25 years, and the life of the controller and inverter is more than 10 years. Grid-connected inverters and power distribution systems, with a comprehensive range of fault and accident protection functions to ensure the safety of personal and power grid and photovoltaic system equipment. The equipment of the system can be connected by welding and special bolts. Only professional tools can be opened, which can play a certain role in safety and anti-theft. For electrical safety, because the live parts are sealed, the cables are dark, and the critical parts are marked with warning signs. Therefore, as long as the installation manual is used, there will be no other safety problems.
The solar photovoltaic roof system is jointly optimized by professional power system professional organizations, with high reliability and cost performance. Therefore, the photovoltaic roof system is stable and reliable, and does not pose any danger to the person and the house, and is safe and reliable. Specifically, there are the following points:
1) The roof is installed with solar photovoltaic system, the supporting members and foundation are effectively installed on the load-bearing wall, and the photovoltaic system has less load-bearing capacity for the roof. Since the load of the photovoltaic module and the supporting system is ≤25kg/m2, the building roof is laid with photovoltaic The components are fully capable of meeting the original design load bearing requirements of the roof.
2) Considering that when the solar photovoltaic system is installed on the roof, the support members and foundation are effectively installed on the load-bearing wall, and the waterproof layer of the roof is treated as necessary to ensure that the solar photovoltaic system is installed on the roof, and the roof does not seep. Leakage and other issues.
3) When installing PV modules on the roof, fully consider the safety distance with the eaves to ensure the impact of installation, construction and windy weather, and take effective protective measures to install the structure to prevent the components from falling off.
4) Consider the overall architectural appearance requirements of the building and achieve an effective combination with the building so that it does not affect the overall appearance of the building.
7. Conclusion The project will use the roof of the existing office building at the selected address to install the total installed capacity of the polycrystalline silicon battery module at a gradient of 25 degrees to 66.3 kWp. The total investment of the project dynamics is about 530,000 yuan. The annual average annual on-grid electricity consumption during the 25-year economic life is about 63,300 kW2h.
The construction of this project has a very positive demonstration significance for optimizing energy structure, protecting the environment, reducing greenhouse gas emissions, promoting solar energy utilization and promoting the development of the photovoltaic industry, and also has good social and environmental benefits.
Source: Green Building, 2017, issue 3.
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