Severe drought! No rain! Is it all caused by floating photovoltaics?

In recent years, as the available land resources for photovoltaic power generation have become increasingly scarce, water-based photovoltaic power generation has attracted widespread attention due to its various advantages, and has been successfully applied in various scenarios such as lakes, rivers, tidal flats, and offshore areas.
Relevant data show that as of now, more than 60 countries and regions around the world are actively promoting the development of water-based photovoltaic Power Stations, of which more than 35 countries and regions have more than 350 floating photovoltaic power stations. As a major photovoltaic country, my country's coastal provinces such as Shandong, Jiangsu, Zhejiang, Liaoning, and Guangdong are also actively deploying water-based photovoltaic power generation and carrying out their ownwater-based photovoltaic projects.
However, with the rapid development of water-based photovoltaic power generation, the remarks about its "hidden dangers" have never stopped in recent years-what impact does water-based photovoltaic power generation have on the ecological and climate environment? And, does the fish-light complementary model really have no impact on fishery farming?

Impact of water-based photovoltaic power generation on water ecology
The paper "Analysis and Countermeasures of the Impact of Water-based Photovoltaic Power Stations on the Ecological Environment of Waters" published by the Three Gorges Ecological Environment Monitoring in 2018 pointed out that the main objects of the impact of water-based photovoltaic power stations on the ecological environment during operation are plankton and fish.
For plankton, the main impact of water-surface photovoltaic power stations is the long-term blocking of sunlight, which weakens the photosynthesis ability of phytoplankton and hinders its growth and reproduction to a certain extent; and the reduction in the number of phytoplankton will lead to a decrease in the number of zooplankton that feed on phytoplankton.
For fish, the long-term operation of water-surface photovoltaic power stations will not have a direct impact on fish, but may lead to a decrease in fish bait organisms, that is, a decrease in the number of zooplankton.
However, with the continuous innovation and development of water-surface photovoltaic technology, the awareness of protecting the water ecological environment in the engineering design stage of the project is also increasing. When developing large lakes, reservoirs and other water bodies with relatively mature ecosystems, from the proportion of the area covered by water-surface Photovoltaic Modules to the specific layout method, they are moving towards maintaining the healthy and sustainable direction of the water ecosystem.

At the beginning of 2021, the International Journal of Low Carbon Technology also published a related report. By setting up water surface photovoltaic modules with different coverage and tilt angles and monitoring the water quality parameters of the water bodies below, the results showed that there was no adverse effect on water quality; on the contrary, the data showed that the concentrations of nitrate and chlorophyll in the water bodies also improved, with the highest nitrate concentration falling by 14%, and the average chlorophyll concentration in surface water falling by 17.5%. This is because the photovoltaic modules cover the water surface, reducing the evaporation of the water surface and lowering the water temperature, thereby inhibiting the reproduction of algae.
A study in the UK found that surface Solar Power Stations can in turn improve the water quality of rivers and lakes. This is based on the discovery that when the water body is heated by sunlight and divided into two layers with different temperatures, the bottom water body will be deoxygenated and the water quality will be reduced. After the photovoltaic array is set up on the surface, the duration of the "stratification" of the water body will be shortened, which can play a role in protecting the water quality to a certain extent. This finding points to at least two aspects of the value of water-based photovoltaics:
1. Mitigating the impact of global warming on water bodies in the coming months and years;
2. Protecting the quality of drinking water sources.

Impact of floating photovoltaics on the climate
Beginning in 2020, BayWa r.e., Europe's leading provider of floating photovoltaic solutions, conducted an environmental impact survey of a 27.4MW floating photovoltaic power station located in a quarry in the Netherlands for more than a year with the help of Hanze University of Applied Sciences, University of Groningen and research institute Buro Bakker / ATKB.
According to the report, the oxygen content in the water under the photovoltaic modules changed very little over the year, wind and sunlight still easily reached the water surface under the modules, and the measured deviations were mainly caused by changes in weather conditions. The water quality under the floating system is still at the same level as the adjacent waters.

There is actually no experimental data to support the statement that "water photovoltaics cause drought". In fact, water photovoltaics do have the characteristics of suppressing evaporation, but they are a kind of protection of water resources.
Recently, Professor Ma Chao and others from the State Key Laboratory of Water Conservancy Engineering Simulation and Safety of Tianjin University published an article titled "Optimal Configuration of Water Savings Corresponding to the Evaporation Suppression Effect of Water Surface Photovoltaics - Taking the Water Replenishment of Baiyangdian Wetland as an Example" in the South-to-North Water Diversion and Water Conservancy Technology (Chinese and English) Journal. Through scenario simulation and optimization calculation, the article reveals the competitive relationship between multiple objectives and puts forward water resource allocation suggestions for wetland ecological water replenishment.
The research results show that water saving by suppressing evaporation by water surface photovoltaics can effectively improve the economic value and water resource guarantee capacity of reeds in Baiyangdian Wetland, but it will have an adverse impact on the power generation of Danjiangkou Reservoir. Under low, medium and high water replenishment demands of Baiyangdian, the economic value of reeds increased by 50 million, 260 million and 550 million yuan respectively, and the water resource guarantee capacity increased by 61%, 42% and 28% respectively. In summary, this study shows that water-saving by suppressing evaporation with water-surface photovoltaics can effectively improve the wetland ecological environment and reduce the risk of wetland drying. Optimizing the allocation of water-saving by suppressing evaporation with water-surface photovoltaics can maximize the benefits of both wetlands and water sources.

There is great potential for fishery-photovoltaic complementarity
The most widely used application of water-surface photovoltaics is "fishery-photovoltaic complementarity". Let's take a look at some actual cases.
The Jinshan 100MW fishery-photovoltaic complementarity project of Huadian Zhaoqing Company, located in Gaoyao District, Zhaoqing City, Guangdong Province, has a fish pond of about 1,200 acres, with rows of four or five-meter-high Photovoltaic Panels neatly arranged. Photovoltaic power generation can be used on the top, and fish and ducks can be raised on the bottom.
It is understood that this project was not recognized by the villagers at first, and everyone was worried that the installation of photovoltaic panels on the fish pond would affect breeding. But after the first batch of fish and ducks were put into breeding, the advantages of "fishery-photovoltaic complementarity" soon emerged. In previous summers, due to the continuous high temperature, farmers often suffered heavy losses in fish and duck fry, and there was no good solution. But now, the more than 4-meter-high photovoltaic "umbrella" in the fish pond brings a shade. Whether it is the fish in the water or the ducks on the water, the survival rate has increased, which has become the most direct benefit brought by the "fish-light complementarity" model.
This is the Jinshan 100MW fish-light complementarity project of Huadian Zhaoqing Company located in Gaoyao District, Zhaoqing City, Guangdong Province. The fish pond of the entire project is about 1,200 acres, and rows of four- to five-meter-high photovoltaic panels are neatly arranged. Photovoltaic power generation can be used on the top, and fish and ducks can be raised on the bottom.
It is understood that this project was not recognized by the villagers at first, and everyone was worried that the installation of photovoltaic panels on the fish pond would affect breeding. But after the first batch of fish and ducks were put into breeding, the advantages of "fish-light complementarity" soon emerged. Every summer in previous years, due to the continuous high temperature, the fish and duck fry of farmers often suffered heavy losses, and there was no good solution. But now, the more than 4-meter-high photovoltaic "umbrella" in the fish pond brings a shade. Whether it is the fish in the water or the ducks on the water, the survival rate has increased, which has become the most direct benefit brought by the "fish-light complementarity" model.
Fish and shrimp continue to be raised under the photovoltaic panels. With the help of photovoltaic brackets, the base has equipped each breeding pond with a steel greenhouse, which is covered with insulation boards and waterproof films. The water temperature reaches about 25℃, which truly realizes the photovoltaic greenhouse shrimp farming "cooling in summer and keeping warm in winter". By adopting a stepped factory-based breeding model, the temperature and humidity of the breeding pond can be effectively adjusted to create a good growth environment for shrimp. Among them, the breeding output of white shrimp in South America has reached more than 10 times that of traditional earth pond breeding.
Looking around the world, there are extremely rich resources such as oceans, rivers, lakes, and reservoirs. Water surface photovoltaic power stations are undoubtedly the third front to remove land resource constraints and broaden photovoltaic power generation. However, as the scale of water photovoltaics expands, its impact on the ecological environment still needs to be taken seriously. How to maintain the healthy development of the water surface photovoltaic industry with more ecological and environmentally friendly design solutions and materials will be an important "test question" in the industry.