Making a lettuce greenhouse more sustainable using water-cooled LED fixtures

In 1994, Peter and Christel Verschaeren of the Flemish company Hydroponic bvba started growing lettuce directly in the ground in almost 12,000 m2 (approx. 129,000 sq ft). Now they're growing their lettuce on a mobile gutter system under glass, HPS lamps have been installed, and the greenhouse has been automated further. Persistently high energy prices have led them to look for a new, more efficient lighting technology that allows them to install more lights using less energy.

 

The current 750 W HPS lights in the lettuce greenhouse will be replaced 1 for 1 by Oreon’s 650 W Empress fixtures, using the same wiring. The section that is used to raise the young plants is equipped with LED fixtures with a special “lettuce spectrum,” with far-red light (based on a study done at the Research Station for Vegetable Production in Belgium). The remaining sections are equipped with LED fixtures with a spectral ratio of red, blue and white. This allows the company to aim for good crop formation and less tip burn.

The active water cooling of the LED fixtures contributes to greater sustainability in the cultivation strategy; the crop is illuminated more efficiently and the excessive heat can be reused in the greenhouse. Peter and Christel's greenhouse will soon be equipped with an underbench heating system. Here, the heat released from the LED lamps will be reused through underbench heating, to heat the crop from below. This achieves considerable savings in cubic meters of gas.