Citation: Sobolewski, K.; Sobieska, E. Lightning Protection of Floating Photovoltaic Power Plants—Simulation Analysis of Sample Solutions. Energies 2023, 16, 4222. https:// doi.org/10.3390/en16104222 Academic Editors: Zbigniew Nadolny and Krzysztof Lowczowski Received: 26 April 2023 Revised: 11 May 2023 Accepted: 18 May 2023 Published: 20 May 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Lightning Protection of Floating Photovoltaic Power Plants—Simulation Analysis of Sample Solutions † Konrad Sobolewski * and Emilia Sobieska Faculty of Electrical Engineering, Warsaw University of Technology, 00-661 Warsaw, Poland; emilia.sobieska.dokt@pw.edu.pl * Correspondence: konrad.sobolewski@pw.edu.pl † This paper is an extended version of our article published in the 2022 36th International Conference on Lightning Protection (ICLP), Cape Town, South Africa, 2–7 October 2022; pp. 1–6. Abstract: Photovoltaic power plants are gaining in popularity and availability every year, resulting in a massive increase in their number and size. However, each such investment involves allocating large land areas, the cost of which may be high. For this reason, there has been an increasing interest in the use of post-industrial wastelands in the form of artificial water reservoirs which often occupy large areas. Because their use as places of recreation can be dangerous for people, it is a cheap alternative for the foundation of a floating photovoltaic power plant. In addition, it has an advantage over the land version in that it is possible to produce a more significant amount of energy by using the sun’s rays reflected from the water’s surface. Despite these undeniable advantages, such a structure poses several technological challenges. This article focuses on the aspect of lightning protection, which is particularly important due to the structure’s location in the open, and also a specific ground type with noticeably different mechanical and electrical characteristics than typical soil. Aspects such as the lightning hazard, arrangement of lightning rods, down conductors, lightning equipotential bonding, and various earthing configurations are discussed. The presented analysis is based on geometric models and simulations made in the Ansys/Maxwell 3D environment and is supplemented with calculations in Matlab/Simulink. Keywords: lightning protection; overvoltage protection; floating photovoltaic power plant; grounding; modeling; simulations; Ansys; Matlab; earthing; sustainable energy 1. Introduction Technological progress continues yearly, consuming more electricity and making it necessary to increase energy production. The conservative approach based on the use of fossil fuels is becoming less and less appropriate due to the rapid depletion of their reserves. Political pressures also emphasize the use of so-called green energy based on renewable sources such as the sun or wind. From a practical point of view, a perfect example of this is the successive increase in the number of photovoltaic power plants. Until recently, they were built on a small scale for individual use. However, decreased production costs and their increasingly widespread availability have meant that their areas are noticeably more extensive today, and the peak power generated reaches hundreds of megawatts. Unfortunately, the current problem is the requirement for a sufficiently large area of land, which may affect production, maintenance, and the return on investment costs. A way to solve this problem may be to use artificial water reservoirs which are often created as wastelands for industrial or mining activities. As a remnant of industrial processes, such a reservoir may be excluded from recreational use for many years and considered a landscape nuisance. Therefore, the cost of renting such unusable land for constructing a floating photovoltaic power plant may be significantly lower than that typical for usable land. In addition, this type of investment can contribute to the energy Energies 2023, 16, 4222. https://doi.org/10.3390/en16104222 https://www.mdpi.com/journal/energies