Wave response modelling and innovative cooling technologies for offshore photovoltaics

Abstract

Solar energy is becoming increasingly popular, especially with countries racing to meet renewable energy share targets and achieve energy independence. However, inefficiencies in solar cells result in most absorbed energy being converted into heat, with only a small fraction being used to generate electrical energy. While onshore solar installations have been predominant, offshore photovoltaics (PV) are emerging as a promising technology with vast untapped potential. Offshore photovoltaics refer to installing solar panels on floating structures or platforms in bodies of water, such as oceans, seas, and lakes. This approach offers several advantages over traditional onshore solar installations. Firstly, offshore photovoltaics can overcome the limitations posed by land availability, especially in densely populated areas or regions with limited suitable land for solar installations. Additionally, offshore photovoltaics can help to mitigate visual impacts and landuse conflicts associated with onshore installations, as they are located away from populated areas. Moreover, floating solar platforms open up possibilities for location sharing with other marine-based activities, such as aquaculture or water treatment, creating opportunities for integrated and sustainable use of marine resources. However, it is essential to address challenges related to technology development, installation logistics, environmental impacts, and cost-effectiveness to fully realise offshore photovoltaics' potential. This thesis analyses the different parameters that could negatively affect the efficiency of offshore PV panels and focuses primarily on the incident solar radiation and the effect of temperature. A decrease in the insolation on PV panels directly results in a reduction in energy generation. Furthermore, an increase in solar cell temperatures results in a decreased conversion efficiency and, as a result, a decreased energy yield. Since no long-term offshore photovoltaic installation exists, various research and technology gaps still need to be addressed. For instance, floating structures will have some response to incoming waves. This response is highly dependent on the design of the floating structure and will have some effect on the insolation on offshore photovoltaic systems. However, there are currently no tools available that an offshore system designer can use to quantify this effect and optimise their design. This research presents a new simulation tool termed Offshore Solar Irradiance Calculator (OSIC) that can quantify this effect. The development of this tool is outlined in this thesis, and parametric analyses are presented, showing the impact of wave response motion on fixed and tracking offshore PV installations. The findings of this research show that wave responses can affect incident radiation, ranging from a slight increase of 0.26% to a decrease of more than 12% for high amplitude wave responses. These findings could have significant impact on the design of offshore PV systems. Moreover, this thesis also presents a patented Innovative Photovoltaic Cooling System (IPCoSy) that addresses limitations in existing PV cooling technologies. The cooling system involves the addition of a water chamber at the back of a conventional PV module, resulting in uniform cooling and a decreased pump switching frequency. The findings of this research showed that the positive effects of this cooling technology range from more than 10% increase in PV electrical energy yield, and thermal efficiencies of up to 56%. The development, testing and future recommendations of this technology are all presented in this research. Therefore, this research contributes new knowledge toward optimising offshore photovoltaic installations through wave response modelling and innovative cooling technologies. Furthermore, this thesis contributes knowledge to improve the PV industry and presents technology that could also change the current concept of a PV module and revolutionise the integration of renewable energy in buildings and industry.