Put it on the water! Floating PV Systems: A new energy outlook
The floating photovoltaic system is a new concept in energy technology to meet the needs of our time. The system integrates existing land based photovoltaic technology with a newly developed floating photovoltaic technology. In this research, the generation efficiency of floating and land photovoltaic systems were compared and analyzed. Floating PV has shown greater generation efficiency by over 10% compared with the general PV systems installed overland.The floating PV system is a new method of solar-energy generation utilizing water surface available on dams, reservoirs, and other bodies of water. This method has an advantage that allows efficient use of the nation’s soil without bringing damages to the environment, which the pre-existing PV systems cause when it is installed in farmlands or forests.
Concept of floating PV system:
A developed PV floating power generation results from the combination of PV plant technology and floating technology. This fusion is a new concept for technology development. As a new generation technology, it can replace the existing PV plants that are installed on top of woodland, farmland and buildings. The PV floating plant consists of a floating system, mooring system, PV system and underwater cables.
a. Floating System: A floating body (Structure + Floater) that allows the installation of the PV module.
b. Mooring System: Can adjust to water level fluctuations while maintaining its position in a southward direction.c. PV System: PV generation equipment, similar to electrical junction boxes, that are installed on top of the floating system.
d. Underwater Cable: Transfers the generated power from land to the PV system.
K-water 100kW, 500kW floating PV systems:
K-water has installed a 100kW floating PV system on the water surface of Hapcheon dam reservoir in October 2011 for operation. After successfully installing the 100kW floating PV system, K-water additionally installed a 500kW floating PV system on another location nearby in July 2012. The electricity generated by the two floating PV systems installed in Hapcheon dam reservoir are generating profits by being sold to the national power grid. Figure 2 displays the view of the 100kW and 500kW floating PV systems.
Empirical research on the efficiency of floating PV systems compared with overland PV systems:
The 100kW floating PV system in Hapcheon is forming a 33° tilt and its installed capacity is 99.36kW, composed of 414 240W modules. The figure represents the generation quantity and capacity factor of the Hapcheon 100kW floating PV system based on the data acquired between January 2012 to December 2012. The standards for generation quantity was the amount read on the meters at VCB (Voltage Collector Base), and the capacity factor was calculated under the following equation.
Monthly average generated quantity during January 2012 to December 2012 was 10,853kWh, and the average capacity factor was 14.9%. The maximum monthly generated quantity was 13,792kWh in October and the minimum was 8,224kWh in December. For capacity factor, The maximum capacity factor was 18.7% in October and the minimum was 11.1% in December.
The 500kW floating PV system in Hapcheon is forming a 33° tilt and its installed capacity is 496.8kW, composed of 2070 240W modules. The figure displays the generation quantity and capacity factor of the Hapcheon 500kW floating PV system based on the data acquired from October 2012 to March 2013. The standards for generation quantity was the amount read on the meters at VCB (Voltage Collector Base), and the capacity factor was calculated under the above same equation.
Monthly average generated quantity during October 2012 to March 2013 was 55,028kWh, and the average capacity factor was 15.2%. The maximum monthly generated quantity was 76,748kWh in March and the minimum was 41,684kWh in November. The maximum capacity factor was 20.8% in March and the minimum was 11.7% in November.
Comparison of generation performance between floating PV systems and overland PV systems:
For a comparative analysis of the generation performance of Hapcheon floating PV system, the system was compared with a 1MW overland PV system installed in Haman-gun. Haman was chosen as the comparison target as the Haman 1MW overland PV system is installed 60 kilometers southeast from Hapcheon, where the solar radiation and temperature is similar, and also has similar date of installation (2012). Haman 1MW overland PV system forms a fixed 30° tilt and its installed capacity is 935.9MW, while composed of 4,000 250W modules.
First of all, for a more accurate comparison analysis between the 100kW floating PV system and the 1MW overland PV system, days with blackouts, maintenance, and data-error were excluded from comparison. The analysis period consisted of one year starting from February 2012 to January 2013, while data from 185 days of the period were used for analysis. Hapcheon 100kW and Haman 1MW’s daily generation quantity was 421kWh/day and 3,486kWh/day each.
To compare the two power plants with different capacity, “Daily average generation quantity of Haman 935.9kW overland PV system when converted into 99.36kW” was calculated and compared with the “Daily average generation capacity of Hapcheon 99.36kW floating PV system.” As the result, the coefficient of utilization of the 100kW and 1MW were 17.6% and 15.5% respectively, which means that Hapcheon 100kW floating PV system’s value is 13.5% higher than that of Haman 1MW system. Figure compares the daily generation capacity of the 100kW and 1MW system(converted into 100kW system).
Secondly, we analyzed performance of 500kW and 1MW with same method.
The analysis period was six months starting from October 2012 to March 2013, while data from 122 days were used for analysis. Hapcheon 500kW and Haman 1MW’s daily generation quantity was 2,044kWh/day and 3,491kWh/day each.
To compare the two power plants with different capacity, “Daily average generation quantity of Haman 935.9kW overland PV system when converted into 496.8kW” was calculated and was compared with the “Daily average generation capacity of Hapcheon 496.8kW floating PV system.” As the result, the coefficient of utilization of the 500kW and 1MW shown 17.1% and 15.5% respectively, presenting that Hapcheon 500kW floating PV system’s value is 10.3% higher than that of Haman 1MW system. Figure compares the daily generation capacity of the 500kW and 1MW system(converted into 500kW system).
Conclusion:
This research compares and analyzes the empirical data of the floating PV system, which K-water has installed, with that of the existing overland PV and has verified that the generating efficiency of floating PV system is superior by 11% and more. During analysis, data acquired when the floating PV system was rotated and moved by wind was not used. Research on a mooring system that can completely fix the buoyant structure of the floating PV system on the water surface is continually needed. Also, in order to enlarge the generating efficiency, development of a solar-tracking floating PV system that can change its azimuth and tilt angles is required. Currently, K-water is researching and developing a 100kW solar-tracking floating PV system, which has superior generating efficiency compared to the stationary floating PV system, and it is expected that development of such system will open a new chapter in the solar-energy market.
Reference: M. Abdolzadeh and M. Ameri, “Improving the effectiveness of a photovoltaic water pumping system by spraying water over the front of photovoltaic cells”, Proceedings of ISES World Congress 2007.
