A shadow detection method performed by a luminous smart package consisting of a product package incorporating a shadow detection system, the shadow detection system integrates: - light sources (6,6a) powered by Organic Photovoltaic Devices OPVs, - a small dimension electronic circuit which comprises a capacitor, a microprocessor and a load control circuit, - a printed circuit board with pressure terminals connected through printed conductive electrodes with a flexible plastic substrate carrying an OPV device and light sources (6,6a) such as Light Emitting Diodes (LEDs), Organic Light Emitting Diodes (OLEDs) and electrochromic (LECs), characterized in that the luminous smart package performs the flow chart of the microprocessor program of its electronic circuit based on four operating modes: a) starting mode, b) sleep mode, c) ready mode and d) flashing mode and is performed by the following steps: a) The luminous smart packaging is set to starting mode when is placed in indoor lighting conditions; b) as the microprocessor of the shadow detection system is at a low power output of less than 2.7 Volts, the light sources (6,6a) remain in sleep mode; c) when the capacitor voltage exceeds the minimum required operating voltage of 2.7 Volts, then the first light source is activated every 10 seconds to light up for 3 msec, being in ready mode, during which, the PCB electronic circuit shortens the OPV every 1 sec to measure the short circuit current Isc, the maximum value that can be measured being 1 mA; d) if the current is higher than the measurement, it will be saturated at 1 mA and if the value of the Isc is measured 20% less than the previous one due to shading, then the luminous smart packaging goes into flashing mode, where the light sources and are flashing; finally, in both operation modes, ready mode and flashing, if the capacitor voltage drops down the 2.7 Volts, the luminous smart package returns to the sleep mode. - light sources (6,6a) powered by Organic Photovoltaic Devices OPVs, - a small dimension electronic circuit which comprises a capacitor, a microprocessor and a load control circuit, - a printed circuit board with pressure terminals connected through printed conductive electrodes with a flexible plastic substrate carrying an OPV device and light sources (6,6a) such as Light Emitting Diodes (LEDs), Organic Light Emitting Diodes (OLEDs) and electrochromic (LECs), the luminous smart package performs the flow chart of the microprocessor program of its electronic circuit based on four operating modes: a) starting mode, b) sleep mode, c) ready mode and d) flashing mode and is performed by the following steps: a) The luminous smart packaging is set to starting mode when is placed in indoor lighting conditions; b) as the microprocessor of the shadow detection system is at a low power output of less than 2.7 Volts, the light sources (6,6a) remain in sleep mode; c) when the capacitor voltage exceeds the minimum required operating voltage of 2.7 Volts, then the first light source is activated every 10 seconds to light up for 3 msec, being in ready mode, during which, the PCB electronic circuit shortens the OPV every 1 sec to measure the short circuit current Isc, the maximum value that can be measured being 1 mA; d) if the current is higher than the measurement, it will be saturated at 1 mA and if the value of the Isc is measured 20% less than the previous one due to shading, then the luminous smart packaging goes into flashing mode, where the light sources and are flashing; a) starting mode, b) sleep mode, c) ready mode and d) flashing mode and is performed by the following steps: a) The luminous smart packaging is set to starting mode when is placed in indoor lighting conditions; b) as the microprocessor of the shadow detection system is at a low power output of less than 2.7 Volts, the light sources (6,6a) remain in sleep mode; c) when the capacitor voltage exceeds the minimum required operating voltage of 2.7 Volts, then the first light source is activated every 10 seconds to light up for 3 msec, being in ready mode, during which, the PCB electronic circuit shortens the OPV every 1 sec to measure the short circuit current Isc, the maximum value that can be measured being 1 mA; d) if the current is higher than the measurement, it will be saturated at 1 mA and if the value of the Isc is measured 20% less than the previous one due to shading, then the luminous smart packaging goes into flashing mode, where the light sources and are flashing; a) The luminous smart packaging is set to starting mode when is placed in indoor lighting conditions; b) as the microprocessor of the shadow detection system is at a low power output of less than 2.7 Volts, the light sources (6,6a) remain in sleep mode; c) when the capacitor voltage exceeds the minimum required operating voltage of 2.7 Volts, then the first light source is activated every 10 seconds to light up for 3 msec, being in ready mode, during which, the PCB electronic circuit shortens the OPV every 1 sec to measure the short circuit current Isc, the maximum value that can be measured being 1 mA; d) if the current is higher than the measurement, it will be saturated at 1 mA and if the value of the Isc is measured 20% less than the previous one due to shading, then the luminous smart packaging goes into flashing mode, where the light sources and are flashing; finally, in both operation modes, ready mode and flashing, if the capacitor voltage drops down the 2.7 Volts, the luminous smart package returns to the sleep mode.