Floating Solar Photovoltaic Mooring System Design and Analysis

The global Floating Solar Photovoltaic (FSPV) industry has grown at a rapid rate and countries around the world are investing greatly towards increasing the renewable energy share in their power generation portfolio. The floating solar photovoltaic system is gaining popularity due to its non-predatory nature of land allocation and due to the increased efficiency that it provides owing to the cooling effects of water. The FSPV arrays can be installed in lakes, inland reservoirs, dams, and even offshore. Since Floating Solar is a fairly new industry that utilizes new technology (and expertise) related to floatation systems, mooring, and anchoring, etc, such kind of expertise is not readily available in the global scenario. The mooring and anchoring of the floatation system are one of the most challenging aspects of this new technology. A mooring system is essential to keep the FSPV array in place with minimum movement based on project tolerances and to maintain sufficient clearance between neighboring arrays or between an array and other assets (such as pipelines, transformer barges, cables, etc.). Depending upon the project location, the FSPV mooring system needs to be designed to withstand worse storms and weather conditions for a design life of at least 25 years. Based on Inventocean Technologies' experience, each FSPV site has a unique set of challenges, and mooring and anchoring systems are very location-specific. In some sites the anchors may not be installed on the sea bed, others have a largely uneven seabed profile with unreliable bathymetric survey information. Engineered mooring design with carefully determined mooring line lengths is essential to ensure balanced load sharing. A small variation in line lengths may result in variation in line stiffnesses leading to uneven load distribution and therefore the mooring and anchoring installation tolerances in FSPV arrays are much tighter. In addition, to these challenges, the mooring system must cope with varying water levels and mechanisms and engineering design should be able to accommodate these water level variations throughout the system design life. Since floating solar is a recent technology and therefore not much literature and guidelines are available for the design and analysis of its mooring system. In this paper, we have drawn upon Inventocean Technologies' experience in the design and analysis of FSPV's mooring system for different site conditions. A typical FSPV array is considered and its mooring system is engineered to cope with the varying water level at the site. The mooring analysis has been performed for different environmental conditions including wind, waves, and currents, and three water levels (minimum, maximum, and intermediate water level). Analytical methods, in-house developed codes, and numerical tools are used to estimate the global environmental loads on the floating solar array. The mooring analysis is performed for intact and one-line damage conditions in the Bentley System's MOSES software program. Maximum mooring tensions for intact and damage cases and the associated safety factors for the design of mooring components have been presented. The variation in anchor uplift and drag due to the varying water level is also presented. The global array motions due to worse case environment headings are studied. A basic methodology for analyzing mooring systems for Floating Solar Photovoltaic islands has been presented. The results and conclusions are quite significant for the Floating Solar industry and will be useful for the owners, project developers, and other contractors at the early stages of the project conception, initiation, and planning.