Patent ID: 7982378

Claim:
Lighting device for stimulating plant growth comprising: at least one solid state light source, suitable for emitting light of at least one wavelength within a predetermined wavelength range, wherein the at least one solid state light source is adapted for connection to an electrical network; a first tube, at least part of it being transparent for light within the predetermined wavelength range, wherein the at least one solid state light source is positioned in the first tube; a metal cooling tube with a smaller diameter than the first tube and positioned such that it is enclosed by the first tube, wherein the metal cooling tube is suitable for receiving a cooling medium and is provided with a supply opening and a discharge opening for respectively supplying and discharging the cooling medium; wherein the at least one solid state light source is positioned in contact with the cooling tube between the first tube and the metal cooling tube, such that the at least one solid state light source is in contact with the cooling medium.