Natural influence factors of floating PV systems on the sea

The natural factors affecting floating PV systems on the sea mainly include the terrain, wave and natural disaster.

From the perspective of topography, the Bohai Sea and the Yellow Sea coast height difference is small. The continental shelf is relatively flat, and the coastal tidal flat area that can be developed is wider. On the southeast coast and in some areas of Bohai Bay, there are many mountains and small reef islands. The overall elevation difference is large, so the developable coastal tidal flat area will be limited. However, the existence of mountains and reef islands is conducive to the weakening of sea waves. Therefore, we can pay attention to such areas.

According to the data analysis of offshore sea waves in China, the sea wave height of our offshore sea is mostly within 3 meters. The sea wave on the southeast coast is higher than that in the north of Jiangsu. The sea area near the Yellow Sea and the Bohai Sea is more suitable for the construction of large-scale photovoltaic projects on the sea.

As for natural disasters, according to the 2021 China Marine Disaster Bulletin, the major Marine disasters in China will be storm surges, sea wave and sea ice disasters in 2021, which will also have a great impact on photovoltaic construction on the sea. Through the statistical analysis of storm surges, sea wave and sea ice, it can be seen that the economic losses caused by typhoons are the biggest in the coastal provinces. Zhejiang Province, a frequent landing area of typhoons, is the most affected. The loss caused by sea waves was the largest in Shandong Province. The East China Sea and the Yellow Sea were affected by sea waves. Sea ice disasters mainly affect the Bohai Sea and the Yellow Sea.
 
Chinese floating photovoltaic technology index on the sea

The Ministry of Science and Technology clearly listed "Key technologies and core components of offshore floating photovoltaic power generation" as the key research and development plan of "Renewable Energy Technology" in the "14th Five-Year National Key Research and Development Plan" issued by the Ministry of Science and Technology in March this year. The specific assessment indicators are as follows.

(1) Sea conditions for normal operation: wave height is not more than 2.5 meters. The flow rate is not more than 1m/s. The water depth is not more than 25 meters.

(2) The ultimate wind and wave resistance of the anchorage system (design value): the wave height is not more than 5 meters, and the wind speed is not more than 30m/s, which is about level 12 typhoon).

The applications cases of Chinese floating photovoltaic systems on the sea

1. Yantai floating photovoltaic pilot project in Shandong province

Norwegian company Ocean Sun's floating scheme is currently being applied by domestic companies in the Yantai sea area, which has been under construction with an installed capacity of 1MW. Ocean Sun's floating PV system consists of a set of buoyancy rings anchored to the seabed by a mooring system. The PV modules are mounted on a blue plastic film supported by buoyancy rings. The plastic molds rise and fall with the waves, greatly reducing wind resistance and buffering the waves. It makes it easier for the PV system to operate stably in wind, wave and current environments, and to withstand stronger typhoons.

Project details are as follows.

(1) The unit size has three diameters of 50m, 68m and 72m.

(2) Applicable components need to be customized. The size is 1700*1000m. The component power is 335Wp. The unit installed capacity is 300kWp, 500kWp and 640kWp respectively.

(3) Assembly rail on the long side of the component. The film is configured with the corresponding flexible fastening device, and the spacing between the components is 70mm.

(4) The maximum wave height under design conditions is 10m. The effective wave height is 5m. It is designed to resist typhoons at 275km/h, which is about level 17 typhoons. There are no special restrictions on ocean currents. There is no special requirement for water depth and water level change.

2. Putuo Baisha Island floating photovoltaic project

The first batch of test phalanx of the 2022 key science and technology project of National Energy Investment Group Co., Ltd. is in the sea area near Putuo Baisha Island, where a large floating body composed of hundreds of photovoltaic panels floats on the sea surface. Upon completion of the project, it will become the first floating photovoltaic power generation project on the sea in China.