A lighting device (100) has a support structure having lighting elements (422) arranged thereon. The support structure has an internal cooling duct having a duct wall. At least a part of duct wall is in thermal contact with the lighting elements. The cooling duct is configured to allow a natural air flow absorbing heat generated by the lighting elements from the duct wall. The cooling duct extends through the support structure from a first opening having a first cross-sectional area to a second opening having a second cross-sectional area. The cooling duct contains a filler body (412) having a substantially bi-conical shape. The filler body and the duct wall form a cooling duct portion with a third cross-sectional area greater than the first cross-sectional area and/or the second cross-sectional area. The lighting device is part of a lighting system. The system comprises a control unit (700) coupled to the lighting device.