After the development of the PV pre-project, it will enter the design and implementation phase. With the changes in national policies, subsidies for medium and large-scale ground power stations will gradually decrease, and they will enter the stage of low-cost Internet access or low-cost Internet access. The design of photovoltaic systems requires higher control of costs. At present, there are two routes for cost and efficiency control of photovoltaic systems. One is efficient component routing, which uses high-power components to reduce the cost of brackets and labor. The second is the component over-provisioning route, which increases the ratio of components and inverters. The transformer is as full as possible, reducing the cost of the inverter and AC cable, power distribution cabinet, and booster. Both options have their own advantages, but they are not absolute. They need to be comprehensively considered and carefully calculated to find an economic balance point.
Efficient component route
Components of the same power, if the other conditions are the same, the amount of power generated is similar. However, if the same area is installed with the same number of components, using an inefficient 250W or an efficient 320W, the initial cost of the bracket, foundation, cable, and labor in the system is the same, so the single-watt investment of the high-efficiency components will be lower than the average. Inefficient components. In addition to the initial cost, efficient components can also reduce land costs.
As battery efficiency increases, the requirements for material quality, performance, equipment accuracy and process are greatly increased, which inevitably increases the cost of manufacturing. So the price of efficient components is higher than that of conventional components. In order to clarify the impact of high-efficiency component technology on the cost of electricity, we make sensitivity estimates for the effects of power gain and component cost changes on the cost of electricity. In the calculation, the basic initial investment (conventional technology) is assumed to be 5 yuan/W, and the utilization hours are 1200 hours. The calculation shows that for every 5W increase in component power, the component cost tolerance is increased by 0.03 yuan/W.
Cost-reducing logic of high-efficiency component technology: The calculation shows that the cost of BOS for each of the 60-piece components can be increased by 0.05 yuan per 15W, color steel tile roof, ordinary ground and cement roof power station, mountain power station, water surface power station, tracking support power station, etc. W, 0.09 yuan / W, 0.12 yuan / W, 0.135 yuan / W, 0.15 yuan / W. Based on this, if the power consumption of the components used in ordinary power stations increases by 5W, the system investment will decrease by 0.03 yuan/W. By superimposing, the power increase of 5~20W of high-efficiency component technology such as half-chip and MBB can reduce the system investment by 0.03~0.12 yuan/W.
In summary, if the price of the conventional grid components is about 0.1 yuan lower than that of the high-efficiency components, the initial cost of the conventional components is lower, while in the mountain power station and the surface power station, Tracking the power station, the brackets are relatively high, and the advantages of using high-efficiency components are obvious. Therefore, in all cases, the use of high-efficiency components is more profitable than the investment in conventional components. Pursuing high efficiency is not the only option to achieve parity. Consider the ratio of support cost and land cost in the system, and how to improve the single-watt power generation of the power station. Capacity, and component life are equally important to reduce costs.
Component over-provisioning route
Photovoltaic module capacity and inverter capacity ratio, used to be called the ratio of capacity. In the early days of photovoltaic applications, the system was generally designed with a 1:1 tolerance ratio. Practice has proved that the system is optimally measured by the lowest level of the Systemized Cost Of Electricity (LCOE). Under various lighting conditions and the inclination angle of the components, the optimal ratio of the system is greater than that. 1:1. That is to say, a certain degree of improvement in the capacity of the photovoltaic module is conducive to improving the overall economic efficiency of the system, which is the component over-allocation.
At present, distributed photovoltaic and ground power stations are rarely designed according to 1:1 tolerance ratio. Most of them have been over-matched, but reasonable capacity ratio design needs to be combined with specific projects. The main influencing factors include irradiance, system loss, and component mounting angle.
In the case of over-matching, due to the influence of the rated power of the inverter, the system will work at the rated power of the inverter during the period when the actual power of the component is higher than the rated power of the inverter; the actual power of the component is less than the inverter During the rated power period, the system will operate at the actual power of the component. The design of the active over-provisioning scheme, the system will be in a limited state for a certain period of time, and there will be power loss at this time.
How to find this balance point, let us first take a 10MW power station in the second-class illumination area as an example. If the ratio is over-equalized by 1.4:1, it is necessary to estimate the power loss of the time-limited period. In the second-class area, When the weather is fine, the photovoltaic output power can reach 80~90% of the component power. For the convenience and convenience of estimation, the highest power of the average power station is 11.9MW. Since the maximum power of the inverter is only 10MW, there will be 1.9MW at this time. Loss of electricity.
As shown in the above figure, there is a 7-hour limit from 9:00 to 16:00, and it is estimated that the electricity loss is about 5000 kWh per day. If there is 100 days of such weather every year, then the annual loss of electricity is about There are 500,000 kWh of electricity. If the price per kilowatt is 0.5 yuan, the annual electricity cost loss is 250,000 yuan. Inverter should be equipped with 12MW according to the normal over-matching, 1.4 super-matching can save 2MW inverter and booster station, etc. According to the current price, the price of 2MW inverter and combiner box is about 500,000 yuan, 2MW boost The station and its cable supporting equipment is about 1 million yuan, and the money saved by the over-match is equivalent to the 6-year limit of electricity cost loss.
Therefore, if not comprehensively considered, too much over-matching, in fact, can not achieve the original intention of reducing the average cost of the system. The function of the inverter has already exceeded the initial current inverter function. The leading inverter company in China has added a power plant technology research and development department. The main research direction is how the inverter can better integrate with other components, power stations and power grids. Support the grid. The inverter will be transferred from the adaptive grid to the supporting grid. Through the application of information technology, Internet + big data, optimize the system operation and maintenance mode, support the detailed operation and maintenance management of the power station in an all-round and multi-channel, maximize the power generation of the power station and reduce the power generation. Operation and maintenance costs. It is uneconomical to reduce the cost of the inverter by excessive over-distribution.
Starting from the characteristics of the inverter and reducing the over-allocation loss, it is recommended that the components and inverters be equipped as follows: in a type of illumination area, according to 1:1 configuration, in the second-class illumination area, according to 1.1:1 configuration, in three The area with an average sunshine duration of 3.5 hours is configured in a 1.2:1 configuration and is arranged in a 1.3:1 range in three areas with an average sunshine duration of less than 3 hours.
to sum up
The decline in photovoltaic power costs consists of two parts: reducing the cost of BOS and increasing the total power generation for 25 years. One-sided emphasis on one aspect will certainly result in losses, on the other hand, often it is not worth the candle. When using high-efficiency components, consider the component spread and the balance between the brackets; if it is a cluster overmatch, calculate the balance between the loss of electricity and save equipment.