Photovoltaic power stations are developing worldwide as they emit no greenhouse gases while producing electricity. In France, industries such as Total plan to install such stations in fields surrounding their chemical and refining plants. The risk analyses performed for these plants often highlighted Unconfined Vapor Cloud Explosions scenarios, related to heavy gases releases, for which characteristic overpressure effect distances were computed The present work aims at quantifying the impact of the presence of a photovoltaic power station in a potential flammable cloud. It is nevertheless limited to a station geometry provided by Total. The problem is not straightforward as two main physical trends appear: flame acceleration due to panels obstruction and flame extinction when the flame reaches the top of the flammable cloud. It has first to be determined if explosion runaway is possible, this one due to the obstacles repetition on the flame path. Then, characteristic overpressure effects distances can be computed for photovoltaic power plants of any size. To this goal, a CFD-based method is proposed and detailed. The open-source CFD code OpenFoam is used as well as phenomenological considerations for computing characteristic overpressure effects distances.