A wind turbine, comprising: a) a nacelle supported by a tower; b) at least one rotor blade to capture wind energy; c) a light intensity detection system (100, 200, 300, 301, 400, 500, 600, 800), the light intensity detection system (100, 200, 300, 400, 500, 600, 800) comprising: i) a single light sensor (304, 504, 604) adapted to measure the intensity of light; ii a housing (302, 502, 602, 802) for protecting the single light sensor from environmental influences; and iii) a driving mechanism (503, 603, 803) configured to allow the single light sensor to receive light from a first direction at a first time and from a second direction at a second time; and d) a control system for operating the wind turbine, wherein the control system is operatively connected with the light intensity detection system; wherein the control system is adapted to change the operating state of the wind turbine based on the following measurements when a predetermined light intensity condition is exceeded: a first intensity of light from said first direction at said first time measured with the single light sensor and a second intensity of light from said second direction at said second time measured with the single light sensor; the wind turbine further comprising: a guiding device arranged around the tower of the wind turbine, wherein the light intensity detection system (100, 200, 300, 301, 400, 500, 600, 800) is arranged such that it can be displaced along the guiding device from a first position to a second position, and wherein optionally the guiding device includes a first rail system attached around the tower wall in a horizontal orientation, and wherein the driving mechanism is adapted to displace the light intensity detection system along the first rail system. a) a nacelle supported by a tower; b) at least one rotor blade to capture wind energy; c) a light intensity detection system (100, 200, 300, 301, 400, 500, 600, 800), the light intensity detection system (100, 200, 300, 400, 500, 600, 800) comprising: i) a single light sensor (304, 504, 604) adapted to measure the intensity of light; ii a housing (302, 502, 602, 802) for protecting the single light sensor from environmental influences; and iii) a driving mechanism (503, 603, 803) configured to allow the single light sensor to receive light from a first direction at a first time and from a second direction at a second time; and i) a single light sensor (304, 504, 604) adapted to measure the intensity of light; ii a housing (302, 502, 602, 802) for protecting the single light sensor from environmental influences; and iii) a driving mechanism (503, 603, 803) configured to allow the single light sensor to receive light from a first direction at a first time and from a second direction at a second time; and d) a control system for operating the wind turbine, wherein the control system is operatively connected with the light intensity detection system; a guiding device arranged around the tower of the wind turbine, wherein the light intensity detection system (100, 200, 300, 301, 400, 500, 600, 800) is arranged such that it can be displaced along the guiding device from a first position to a second position, and wherein optionally the guiding device includes a first rail system attached around the tower wall in a horizontal orientation, and wherein the driving mechanism is adapted to displace the light intensity detection system along the first rail system.