With more than 80% of the world’s PV production capacity, China has become the country with the fastest growing PV industry, the largest production capacity and the highest technology level in the world. And it has an ambitious installation capacity target to exceed 95GW in 2023 and the cumulative installed capacity is expected to reach 487.60GW, but where will these solar power plants be located due to limited land resources?
China’s PV industry is shifting its attention from land to sea. With the support of the government, marine renewables are expected to make a significant contribution to the future energy mix. A few days ago, China’s Ministry of Natural Resources issued a “Notice on the Promotion of Three-Dimensional Rights in the Ocean (Draft for Comment)” to promote the use of marine photovoltaic and other rights, bringing the prospects for the development of offshore photovoltaic back into the spotlight. And the coastal provinces are in succession to focus on the development of marine photovoltaic industry.
Offshore photovoltaics show great potential in China
According to research by the Marine Energy Development Centre of the National Marine Technology Centre, China’s mainland coastline is 18,000 kilometres long. The total offshore area, including the Bohai Sea, the Yellow Sea, the East Sea and the South China Sea, is more than 4.7 million square kilometres, and theoretically, the scale of installed offshore PV is estimated to be more than 71GW at a ratio of one thousandth, as the sea area where offshore PV can be installed is about 710,000 square kilometres.
Cui Lin, deputy director of the Marine Energy Development Centre of the National Marine Technology Centre of the Ministry of Natural Resources, introduced that “the global potential capacity of offshore photovoltaic is about 4,000GW, the theoretical volume of offshore photovoltaic that can be installed, including pile-based and floating both of which can be combined with the aquaculture industry, will exceed 70GW and with China’s long coastline”.
Marine solar energy resources and direct normal irradiance are high enough for solar power. And the electricity generated by offshore photovoltaic power plant could be 5%-10% higher than that of land-based photovoltaic power plant, coupled with the sunlight reflected from the sea surface. Relevant institutions predict that the scale of offshore photovoltaic installation in China will exceed 100GW in a very short time, and it is a promising solution to mitigate many challenges that come with the demand for renewable energy.
Why not ground-mount PV systems
Global demand for energy continues to rise, driven mainly by economic growth and daily consumption, which relies heavily on traditional sources such as oil, gas and coal for electricity generation. And these are known to emit carbon dioxide, which has a negative impact on the environment. Solar power is essential as an alternative and more sustainable source of electricity.
In recent years, falling costs, increasing investment and technological innovation have led to unprecedented growth in solar power, both globally and in China. The use of PV energy can be seen in a wide range of applications, from road signs to coastal monitoring buoys, from distributed rooftop systems to hundreds of megawatts of ground-mounted systems and building-integrated PV. Commercial utility-scale PV systems have already achieved grid parity with conventional power plants in many regions of the world.
Solar energy is expected to grow rapidly in the coming years. According to the International Energy Agency (IEA) in June 2023, 630 GW of new solar PV installations are expected per year by 2030, and by 2050, solar energy will become the largest source of energy, accounting for a fifth of total energy supply, meaning that 20 times more solar PV and 11 times more wind power will be installed than is needed today to meet the global goal of zero carbon emissions. However, the installation of large-scale PV systems has a major impact on land use, requiring approximately 0.016 square kilometres of land for each megawatt installed.
There are several facts that limit ground-mounted PV. Assuming that 80% of the 630 GW of new solar PV installations will be achieved through ground-mounted PV systems, this would imply a land demand of nearly 8,064 square kilometres per year. Most of the attractive sites for ground-mounted solar have already been developed in the last decade. And there will be challenges in acquiring land for PV projects as land is used for multiple purposes such as agriculture, forestry, transport, construction or tourism, animal welfare, etc. The lack of available land will contribute to an increase in acquisition costs, which will negatively affect the economic viability of solar projects. For remote areas, far from consumers, higher costs are unfavourable due to lack of access to transmission infrastructure and long distances to deliver electricity. In addition, in difficult areas such as hilly or unstable terrain, the cost of increased site earthworks is also high.
Benefits of offshore PV plants
With the development of floating photovoltaics in recent years, offshore PV is seen as an important alternative solution for both increasing solar power installations and reducing greenhouse gas emissions. And a lot of pioneering research has been done on offshore PV systems. The installed capacity of floating PV was 132 MW in 2016, and then a total cumulative installed capacity of 1.1 GW in 2018. Meanwhile, in addition to overcoming the problem of lack of land costs, there are a number of other advantages to building at sea, similar to the large-scale offshore wind projects developed in recent years.
Firstly, there is more sunshine at sea, as light can be reflected off the water surface onto double-sided modules, and the high atmospheric cleanliness, generally lower ambient temperatures and higher wind speeds on open water than on land result in an evaporative cooling effect that can increase power output by up to 15%, with the added benefit of a cooling system for the panels.
Evaporation is a major cause of water loss, and overwater PV panels can reduce this by providing shade and limiting wind interaction with the water surface. In addition, in some areas, overwater PV can reduce the risk of algal blooms.
Unlike inland environments such as deserts and hilly areas, water can be harvested on site in the ocean, making it easier to clean, cool and maintain the modules, as dust build-up and temperature rise account for most of the losses in PV power generation. Meanwhile, the entire process of water use, recovery, sedimentation and recycling can be economically achieved in water-based PV systems, thereby increasing revenue.
Aquaculture and solar can be hybridised offshore for the benefit of all. The shiny blue PV panels pointing towards the sun provide a roof for the fish and shrimps in the sea, as well as green electricity for households. A solar power project can breathe new life into the area, which needs support for green aquaculture. Huawei had provided a smart PV solution for Zhanhua District of Binzhou City in northern Shandong Province, China, to turn a salt field into one of the largest fishery solar projects in China in June 2020. It produces seafood below the water surface and generates green electricity above the water surface, representing a holistic development model that uses the Internet and smart energy to modernise aquaculture.
In some cases, hydro and PV can share facilities, such as proximity to grid connections and existing facilities and transmission lines. The potential for co-location of offshore PV with offshore wind is cost savings and increased energy production. Solar and wind can provide a better ability to meet peak demand, especially during periods of high and low water, when the two resources are highly complementary. This means that there is little or no siting cost. The location of wind turbines can be chosen.
This keeps the solar panels cooler in the sea and increases conversion efficiency. In addition, installation costs can be minimised because the generation can be built in modular units on land and delivered to the site ready to plug and play, making the development of marine solar energy an important alternative for reducing greenhouse gas emissions.
Offshore PV installations in China
By mid-2022, China’s installed floating PV capacity is 1.33GW, accounting for 44% of the world’s total installed capacity, making it the country with the largest installed floating offshore PV capacity in the world. By the end of May 2022, there were 28 offshore PV projects in China, including 18 in Jiangsu Province, 4 in Shandong Province, 3 in Zhejiang Province, 2 in Liaoning Province and 1 in Guangdong Province, with a total area of 16.5833 square kilometres (1,658.33 hectares).
On 31 October 2022, China’s 500 kW demonstration project, part of the 20 MW deep-sea floating PV system at Shandong Peninsula South No. 3 Offshore Wind Farm, successfully generated electricity, making it the world’s first deep-sea wind-solar project to be put into operation. The project tested the wind, wave and weather resistance of the floating body, mooring and power generation components in the marine environment, and verified the technical feasibility of wind and solar co-location in the same facility.
On 10 May 2023, the world’s first fixed long pile offshore PV research project, the Shandong Wendeng HG32 Offshore PV Demonstration Base, successfully started generating electricity and officially entered the trial operation period. Located approximately 9.2km from the coast, the project consists of three typical structural units of the offshore PV technology being promoted, with a total installed capacity of 0.5MW on the DC side, of which the 670W n-type modules were supplied by Trina Solar. The PV plant is similar to the State Power Investment Peninsula South No. 3, will promote the comprehensive use of offshore photovoltaic offshore wind power, and marine ranching.
The temperature of seawater near China is around 0-29 degrees Celsius, which is within the normal operating range of PV modules. However, waves, sea winds and natural disasters pose a risk of deformation, breakage and other damage to the modules. In addition, marine life, salt spray and seawater have a significant impact on the power generation of the modules, reducing the passivation effect on the surface of the cells and causing them to degrade. Other challenges for marine PV systems include the difficulty of stacking and laying cables for water-based operations, high temperatures and humidity that exacerbate the potential induced degradation (PID) effect, time-consuming and costly operation and maintenance in vast expanses of water, and high requirements for fisheries-solar integration.
Although there are many challenges in developing offshore PV systems, both in terms of construction and maintenance, many major PV manufacturers in China have changed their approach to offshore PV solutions. LONGi, Huawei, Trina Solar and other institutions are working on related technologies and solutions to deal with the temperature and humidity, which aggravate the potential induced degradation effect and the efficiency and reliability of modules.
According to Trina Solar, the company has fully considered the requirements of all scenarios in the development of the n-type module. Trina Solar’s success in supplying modules for floating solar systems proves that its Vertex Series modules are suitable for the marine environment. LONGi stressed that safety and reliability are key factors for offshore PV modules, and that a turnkey solution for offshore PV systems, including technical support and services from development, design, construction, operation and maintenance, is available to provide LONGi’s customers with long-term value and returns beyond expectations.
To promote the development of China’s offshore photovoltaic power plants, various regions have introduced favourable policies. Shandong leads all provinces in both subsidies and planning support for two offshore PV projects near the Bohai Sea and along the Yellow Sea, each with GW-level installed capacity. In addition, the Shandong Provincial Energy Administration has issued a tender for the deployment of 11.25 GW of floating PV in 2022. In addition to PV leaders LONGi and Trina Solar, wind energy giants Ming Yang Intelligence, Envision Energy and Dongfang Electric (DEC) are among the winning bids. The balance between technological breakthroughs and cost control is testing the capabilities of the pioneers.
A number of Chinese companies have already invested in offshore photovoltaic construction. CHN Energy, Guoneng (Shandong) Energy & Environment Co., Huaneng, Chint, Jinneng Science and Technology have started to invest in the construction of offshore PV power plants to explore integrated solutions for efficient energy use, environmental protection, innovative energy conservation and sustainable development of ocean PV systems. The market for floating and anchored offshore PV power plants in China is estimated to be 27.2 billion yuan and 1.9 billion yuan respectively in an optimistic scenario. If other coastal provinces and cities follow that, such as Jiangsu Province’s recent promotion of 43 offshore PV projects with an installed capacity of 12.65 GW, China’s offshore PV market will be larger than expected.
（Picture: Veer）
