Here is a research on power generation performance of FPV systems.

The floating photovoltaic power generation technology is one of the future application directions of photovoltaic power generation. A 6.3+kW floating photovoltaic power generation system and a 6.3+kW onshore photovoltaic power generation system were established in the same location. Their power generation performance data were collected and analyzed. The test shows that the total power generation of the floating photovoltaic system is 2% higher than that of the onshore photovoltaic system. The overall power generation efficiency is higher. The floating photovoltaic power generation system reduces the temperature loss on the power generation of the system is more obvious.

Since we entered the 21st century, people have become keen on the development and utilization of new energy affected by the fossil energy crisis and energy-saving emission reduction policies.  Photovoltaic power generation has become the focus of new energy development and utilization. At present, the development and application of photovoltaic systems are mainly concentrated on the land. With the development of photovoltaic technology, floating photovoltaic power generation technology has attracted the attention of research institutions and new energy development enterprises all over the world because of its advantages of saving land resources, improving power generation and reducing evaporation on the water surface. It has become the future development direction of photovoltaic power generation applications.

The floating photovoltaic system generates electricity by fixing the photovoltaic power generation module on the floating block to receive sunlight. Floating photovoltaic system is the perfect combination of photovoltaic power generation and floating technology, effectively breaking through the constraints of land resources on the application of photovoltaic power generation. It can be installed in lakes, reservoirs, fish ponds and water treatment plants and other water surface, which is especially important for countries and regions with scarce land resources like water bodies.

Floating photovoltaic power generation system has the following advantages: saving land resources, making full use of lakes, reservoirs, fish ponds and other areas to develop solar energy. The light reflection effect of the water surface and the water cooling effect can improve the power generation efficiency compared with the onshore photovoltaic power station. It can reduce the evaporation of water, inhibit the propagation of harmful algae in water, and facilitate cleaning. The construction is convenient and the construction period is short.

In recent years, Japan, the United States, Italy, France, South Korea, Canada and other countries have established demonstration research projects of floating photovoltaic power generation systems on water, to study the indicators and related parameters of floating photovoltaic power generation systems on water. At the same time, China has also built a number of demonstration projects, such as the Three Gorges New Energy Anhui Huainan 150MW floating photovoltaic project and the new set of 100MW floating panda photovoltaic power stations.

1. Test platform construction

A 6.3kW floating photovoltaic power generation system and a 6.3kW onshore photovoltaic power generation system were constructed at the same location in Guangdong Province. Their power generation performance data were collected, processed and analyzed respectively to verify the performance characteristics of the floating photovoltaic power generation system with higher power generation efficiency due to water cooling. According to the actual situation of the project site selection, the test system adopts an integrated structure of floating body and support (referred to as integrated). The floating body provides buoyancy at the same time and fixes photovoltaic modules. By connecting the floating body of support and the floating body of maintenance road, an integrated photovoltaic power generation system is formed. Compared with other floating-support structures, its biggest advantage is the simplicity of transportation, installation, maintenance and cleaning.

In the test, the onshore photovoltaic power generation system is built on the roof. It is laid in the way of 8 blocks (north-south direction) ×3 blocks (east-west direction), and the long edge of the component is in the east-west direction. The floating photovoltaic system is built in the reservoir area, about 25m from the shore, and is laid in the way of 6 blocks (North-South direction) ×4 blocks (east-west direction), with the long edge of the component along the east-west direction. The floating body is anchored by 8 anchor chains. One end of the anchor chain is fixed to the floating body and the other end is fixed to the bottom of the warehouse. Each anchor chain is set with 10 anchor blocks, and the fixed anchor position of each anchor chain is determined by calculation to ensure that the stress of each anchor rope is basically the same in the process of large changes in water level, and to maintain the stability of the position and orientation of the floating power generation system. The power generated by the photovoltaic modules is connected to the 10kW inverter on the roof through the photovoltaic special cable (set of cable protection tube). Then it connected to the existing 380V distribution system of the power station management after inverter. The test system was completed and commissioned in April 2017. 

2. Analysis of test results

2.1 Analysis of total power generation

The test system built a 6.3kW floating photovoltaic system and a 6.3kW onshore photovoltaic system, with a total installed capacity of 12.6kW. According to statistics, the total power generation of the system was 24,892kW·h from May 4, 2017 to December 31, 2018, of which the floating photovoltaic system generated 12,566 kW·h. The onshore photovoltaic power generation system generated 12,326kW·h. The power generation of floating photovoltaic power generation system is 2% higher than that of onshore photovoltaic power generation system. The overall power generation efficiency is higher.

2.2 Analysis of monthly power generation efficiency of floating photovoltaic system

Monthly power generation data from June 2017 to December 2018 were temporarily selected as the basis for analysis. 

It can be concluded from the test data that during the period from June 2017 to December 2018, there were 11 months in which the floating photovoltaic system had higher power generation efficiency than the onshore photovoltaic system. The power generation ratio between the two was between 0.22% and 9.63%. For 8 months, the power generation efficiency of the floating photovoltaic system has not been significantly improved compared with that of the onshore photovoltaic system. Even it appears lower than that of the roof PV system, and the power generation ratio of the floating photovoltaic system and the onshore photovoltaic system is -1.48% to -0.08%. The efficiency of floating photovoltaic system varies seasonally.

2.3 Analysis of daily active power value

1d with high power generation efficiency of floating photovoltaic system was selected to analyze the change of active power of two photovoltaic systems. The 5min active power of the onshore and floating photovoltaic system on December 18, 2017 was selected.

It can be seen from the test data that the active power of floating photovoltaic power generation system in 1d is generally higher than that of onshore photovoltaic power stations, and the changing trend is basically the same as the power generation trend. Among them, the active power difference between 10:35 to 14:30 is obvious. Because the working temperature of photovoltaic modules increases during this period. The floating photovoltaic power generation system reduces the temperature loss on the system power generation power is more obvious.

3. Summary

The test system built a 6.3kW floating photovoltaic power generation system and a 6.3kW onshore photovoltaic power generation system, with a total installed capacity of 12.6kW. According to the data analysis, since the operation of the test system, the total power generation of the floating photovoltaic power generation system is 2% higher than that of the onshore photovoltaic power generation system, and the overall power generation efficiency is higher, which is consistent with the theory, and the power generation efficiency of the floating photovoltaic power generation system shows seasonal changes. Finally, the active power changes of the two power generation systems on the same day are compared. It can be concluded that the active power of the floating photovoltaic power generation system is generally higher than that of the onshore photovoltaic power generation system, and the changing trend is basically the same as the power generation trend. The power difference between the time period before and after noon is obvious. Because the working temperature of photovoltaic modules increases during this time period, it is more obvious that the floating photovoltaic power generation system reduces the temperature loss on the power generation of the system.