In the first half of 2021, the newly installed photovoltaic capacity of 13.01GW, so far, the national installed capacity of photovoltaic power generation has reached 268GW. With the implementation of the “3060 Carbon Peak Carbon Neutrality” policy, the county-wide promotion projects will be spread across the country, and another large-scale photovoltaic construction cycle has arrived. In the following years, photovoltaics will enter the next period of rapid development.
At the same time, the photovoltaic power plants that were previously built and connected to the grid have also begun to enter a stable operation stage, and even the PV power plants built in the early stages have completed cost recovery.
The eyes of the investors have gradually changed from the early stage of investment and development and construction to the later stage of operation, and the construction thinking of photovoltaic power plants has gradually changed from the lowest cost of investment in the early stage to the lowest cost of electricity in the whole life cycle. This requires that the design of PV power stations, equipment selection, construction quality, and operational branch checks are becoming more and more important.
The levelized cost per kilowatt-hour (LCOE) of photovoltaic power plants is being paid more and more attention at this stage, especially in the current period of parity.
From the vigorous development of photovoltaics in recent years, it can be seen that the BOS cost in the development and construction costs of photovoltaic power plants has been compressed to the extreme, and the room for reduction is very limited. It can be seen from the above LCOE calculation formula that to reduce LCOE, we can only start from three aspects: reducing construction costs, increasing power generation, and reducing operating costs.
The financing cost, equipment material cost, and construction cost are the main components of the construction cost of solar PV power plants. In terms of equipment materials, the cost can be reduced by choosing aluminum pv wires and split junction boxes, this has been described in detail in previous news. In addition, it can also reduce construction costs from the perspective of reducing the use of equipment and materials.
The design scheme of high voltage, large sub-array and high capacity ratio is adopted to reduce the cost of system construction. High voltage can increase the current carrying capacity of the line and the transmission capacity of the 1500V system is 1.36 times that of the 1100V system for the cable of the same specification, which can effectively save the use of photovoltaic cables.
Adopting the design scheme of large sub-array and high-capacity ratio, reducing the number of sub-arrays in the entire project can effectively save the usage and installation of box-type substations in the photovoltaic area, thereby reducing the cost of system construction. For example, a 100MW power station compares different capacity sub-arrays and capacity ratios, as shown in the following table:
|Analysis of electrical equipment consumption in PV area of 100MW PV power station|
|Number of Sub-arrays||26||31||74||89|
|Number of Inverters in a Single Sub-array||14||14||5||5|
|3150KVA Transformer Quantity||26||31||/||/|
|Number of 1000KVA Transformers||/||/||83||100|
It can be seen from the above table that under the same capacity ratio, the large sub-array scheme makes the number of sub-arrays of the whole project smaller, and the smaller number of sub-arrays can save the use of box change and the corresponding construction and installation; Under the capacity, the high-capacity ratio scheme can also reduce the number of sub-arrays, thereby saving the number of inverters and box transformers. Therefore, in the design of photovoltaic power plants, the capacity ratio and the way of using large sub-arrays should be increased as much as possible according to factors such as light, ambient temperature, and project terrain.
In the ground power station, the mainstream models at this stage are 225Kw series inverter and 3125kw centralized inverter. The unit price of series inverter is slightly higher than that of centralized inverter. However, the optimization scheme of centralized layout of series inverter can effectively reduce the use of AC cables, and the reduced amount of AC cables can completely offset the price difference between series inverter and centralized inverter.
The centralized arrangement of string inverters can reduce the BOS cost by 0.0541 yuan/W compared with the traditional decentralized layout, and reduce the BOS cost by 0.0497 yuan/W compared with the centralized inverter solution. It can be seen that the centralized arrangement of strings can significantly reduce the BOS cost. For future 300kW+ string inverters, the cost reduction effect of centralized layout is even more obvious.
How to increase the power generation of PV power stations has become the most important link in reducing LCOE. Starting from the initial system design, the design of the photovoltaic system should be determined from the perspective of increasing the PR value, so as to increase the power generation. In the later stage, operation and maintenance are needed to ensure the healthy operation of photovoltaic power plants.
The main factors affecting the PR value of photovoltaic power generation systems are environmental factors and equipment factors. Due to the influence of environmental factors, the inclination angle of the module, the change of the temperature characteristic of the module, and the conversion efficiency of the inverter all directly affect the PR value of the photovoltaic system. Choosing low temperature coefficient components in areas with higher temperatures, and selecting high temperature coefficient components in areas with lower temperatures can increase the efficiency loss caused by component temperature rise; use string inverters with high conversion efficiency and multiple MPPT And other characteristics improve the conversion efficiency of DC/AC.
After calculating the distance between the front and rear rows using the best inclination angle, appropriately reduce the installation angle of the module by 3 to 5°, which can effectively increase the winter light duration.
Make full use of the intelligent operation and maintenance platform, regular inspections in the operation and maintenance phase, and regular equipment inspections, and use advanced big data analysis systems, IV diagnosis systems and other functions to quickly locate faulty equipment in faulty areas, improve operation and maintenance efficiency, and ensure the healthy operation of equipment.
The main costs of photovoltaic power plants in the operation stage involve the salaries of operation and maintenance personnel, equipment maintenance costs, and electricity value-added tax.
The salary expenditure control of operation and maintenance personnel can be optimized from the staffing structure to ensure the participation of 1 to 2 operation and maintenance personnel with very strong technical expertise, build a practical and reliable data analysis system, and adopt scientific methods and management systems to achieve intelligence Operation and maintenance can not only reduce the number of ordinary operation and maintenance personnel, but also improve the efficiency of operation and maintenance, reduce operation and maintenance costs, truly achieve open source and reduce expenditure, and ultimately become unattended.
To save equipment maintenance costs, we must first check the project construction period and select well-known brands (such as slocable) and easy to maintain electrical equipment products (such as GIS, series inverter and other basically maintenance free products). The electrical equipment and photovoltaic cables shall be calibrated regularly, and the potential problems shall be repaired and replaced in time. Reduce the cost of equipment overhaul or eliminate equipment replacement.
Electricity value-added tax is reasonably tax-saving, financial management is done in peacetime, and input tax during the construction period and operation and maintenance period is reasonably used to deduct, especially the scattered expenditures during the operation and maintenance period. The single amount is not large, but the total amount It is not small, it is necessary to obtain special value-added tax invoices for the deduction of value-added tax on electricity bills, and reduce the value-added tax on electricity bills reasonably from bit by bit, and save the old cost.
The reduction of operating costs design all aspects and bit by bit throughout the life cycle of the power station. Many inconspicuous places are often overlooked, and the accumulation of small gains can cause considerable losses during operation.
In short, under the current mode of parity online, there is no subsidy income, and reducing LOCE has become an important means to achieve early recovery of costs and achieve profitability. For LCOE, from the beginning of the construction to the end of operation, it is the concept of the entire life cycle of the entire photovoltaic power plant. Then, the optimal LCOE we pursue is to increase the power generation and gradually reduce the construction and operation costs.