Design and numerical analysis of floating photovoltaic array for fjord conditions

Abstract

To reduce anthropogenic climate change and its negative consequences, renewable energy is key. Solar energy is one of the cheapest forms of renewable energy. However, it demands large land areas, which may cause conflicts. Therefore, floating photovoltaic (FPV) systems have been developed. Existing FPV systems are mainly found on calm water bodies with minimal environmental loads. These areas may also introduce conflicts, and in some regions calm water bodies are a scarcity. Therefore, developing FPV systems that can withstand harsher marine environmental conditions could give the possibility of harvesting solar power in much larger quantities, and with less conflicts related to the use of area. As this is a rather new area of innovation, only few projects exist.

This thesis aims to design and analyse an innovative FPV array that can withstand waves based on environmental loads from Norwegian fjords, with a significant wave height of 2,1 m. These conditions are much harsher than what is seen for most existing FPVs and may also serve as a step towards developing fully offshore FPV systems. The thesis analyses four different connection and mooring configurations to identify the effect on the response of the array.

The suggested design consists of modules with a 2,5 x 2,5 m platform constructed of a grid of aluminium beams, with two 2 x 1 m solar panels and a 0,5 m wide maintenance walkway that allows access to all solar panels and connections, on top of four upright cylindric floaters. The modules are meant to be connected in arrays.

The hydrostatic and hydrodynamic properties of a single module is calculated in the frequency domain using potential theory. The properties are implemented in Sima – Simo - Riflex, where a 3x3 array of modules is assembled and the behaviour is studied in a time domain analysis with irregular waves.

The results show that the design is not suitable for the given environmental conditions without improvements. The connector and mooring stiffness impact the array behaviour, and the results may be used as an inspiration for future designs. The results also indicate that small lightweight FPV systems in large waves may be prone to large motions that are outside the limits of the applied method of analysis.