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Floating Solar Systems: Potential Promise and Challenges

Solar radiation incident on the surface of earth is rather weak. Commercially available solar cells - convert typically between 16 and 20% of this incident energy, under Standard Condition into electrical energy. The low efficiency of conversion in conjunction with multiple losses (cable, temperature, dust and DC-AC conversion) till the point of actual use, calls for large tracts of land for utility scale power generation. Converting fertile agricultural and other productive land to set up solar farms would not be wise. Also in many cases lands have to be cleared of thick vegetation that provide lung space. In island nations like Singapore, Philippines, Korea and Japan, land is scarce. An attractive alternative to the land based solar generation is to utilize the surface of water bodies like lakes, ponds, reservoirs, dams which come at no cost.

While considering water bodies it is worthwhile to note the fact that demand for clean water is growing rapidly even while evaporation losses in water bodies are increasing with rising summer temperatures. It was reported in March 2017 that in Jayakwadi dam, in the state of Maharashtra, the daily evaporation loss of water in monsoon season was 0.4-0.5 million cubic meter and 1.3 mcum per day during peak summer. In the month of March alone the reservoir lost 36.01 mcum which is equivalent to one month’s water supply for the city of Pune. Several Evapro-retardation methods are being tried without much success. PV systems floating on the water surface would be an effective method to reduce evaporation losses as they would reduce substantially the sunrays from reaching the water below. One of the leading suppliers of Floating PV systems has claimed that water losses could be reduced to as much as 70% and makes a good case for these systems.

Besides preventing water losses, the modules and the floats anchoring them reduce photo-synthesis process that promotes algae and other organic growth. This is particularly of interest to water utility companies as it reduces the water treatment and labor costs. Also as large power consumers, utilizing the water surface to generate electricity help them save on their energy cost.

Community Floating Solar PV System, Japan

Source: Ciel & Terre

World’s largest floating system with tracker

Source: Yonhap/Korea Biz Wire

The modules in floating systems operate under much cooler environment and this would reduce thermal losses and also the long term heat induced degradation. Additionally the dust collection issues would be minimum leading to enhanced generation and reduced cleaning frequency. The Water Resources Corporation in Korea in their study found that Floating PV systems generate 11% more energy than an equivalent land based system. There are other studies which report even higher energy generation, closer to 20%. Besides the enhancement in generation, there is no cost of acquiring water for module cleaning.

Floating PV Systems also named as Floatovoltaics come with its own set of challenges. Module racking systems are to be designed for fixing on to pontoons / HDPE plastic floats. All metallic components have to be kept above water level with floats alone in contact with water to prevent corrosion. The float material should not inject any toxic material in the water they float. The floats are to be anchored / moored properly to withstand high velocity winds and rapid flow of water during floods. Floating PV systems that can withstand wind speeds up to 190 kmph and waves of 2 meter height are now commercially available.

Floating solar is picking up in the US, China, Japan, the UK, India and elsewhere. In India the first floating PV plant of 10 KW was installed in a lake in Kolkata in 2014. Recently a 100 KW floating solar power plant was installed in NTPC Kayamkulam in Kerala which is the largest such system in India. The floating platform was indigenously developed by NTPC’s Energy Technology Research Alliance and the Central Institute of Plastic Engineering and Technology.

India’s Largest 100 KW System, Kerala

Source: Mathrubhumi, English

World’s Largest (40 MW) System in China

Source: Sungrow Power Supply

In May this year China installed the largest floating solar system of capacity 40 MW in Huainan.

NB Institute of Rural Technology headed by Mr. Gon Chaudhuri reported that around 300 GW of solar power could be generated by tapping around 10-15% of water bodies in India, particularly in the most potential states of Bengal, Bihar, Kerala, Odisha and Assam.

Despite being land neutral, the cost of the floating systems including anchoring, installation, maintenance and transmission renders the overall cost of the floating solar systems are much higher than the land based systems at this initial stage of development.

Floating solar with just a few years of evolution has to address several technical issues. Besides the two major issues of corrosion and instability, other issues like the long term impact of moist environment on modules, cables, safe transmission of power through the floats to the nearest feeder point, the environmental impact on the water body and the marine life etc needs to be addressed and - make the system cost effective.

Research and Industry professionals are confident that rising demand for floating PV systems and technical advancements would soon bring greater parity in cost with the land based systems.

Many institutions and industries are already engaged in developing simpler design, stronger and longer lasting materials for floating structures, PV specific anchoring/mooring systems and others. International funding agencies are also supporting the development of alternative PV technologies. World Bank is supporting, under its Clean Technology Fund, the development of projects totaling 10 MW of floating solar projects in India. The German Development Bank KfW is funding the development of two projects of total capacity 40 MW to demonstrate the technical feasibility of such projects, to assess the potential and the economic feasibility of setting up floating solar parks in India.

The Solar Energy Research Institute of Singapore (SERIS) is setting up side-by-side, eight large floating systems of 100 KW to make long term comparative study. This would help develop reliable and lower cost floating PV technologies.

In the Intersolar India 2017 conference, we have a session on Floating PV Systems organized by none other than SERIS who are conducting pioneering research.

Join the Intersolar Conference and Exhibition starting on 5th December at the Bombay Exhibition Centre to meet and interact with knowledge and industry leaders, policy makers and other key stake holders in the industry and to know more on the emerging PV Market and Technology Trends and to see the wide range of products and solutions offered by leading manufacturers and solutions providers from India and other leading solar nations of the world.

For more details on the conference please visit our website here.