"32% energy savings achievable without problems"

Since October 2016 the research "Maximum utilization of daylight to minimize exposure Phalaenopsis" is ongoing. It is carried out by Plant Lighting. Last year it was demonstrated in climate chambers that a 32% saving on electricity could be achieved without loss of production. The goal of this research is twofold: (1) research into even further electricity savings in the growth chambers of Plant Lighting and (2) to show that the 32% savings in a greenhouse is feasible without any problems. The latter part takes place in two research greenhouses of Ter Laak Orchids.

State of affairs of climate chamber test at Plant Lighting

The plants in the climate chambers undergo three different treatments, wherein the electricity saving rises up to 43% in comparison with normal practice. Per treatment, two climate-units of net 2 m² are each filled with 100 plants of the 'Sacramento' variety (200 plants per treatment). The daylight in winter is simulated with artificial sunlight and complemented with different strategies SON-T lighting. At the start (week 42) the plants were 14 weeks old and are moved to the cooling section in week 4. Shortly thereafter the effects are measured of the different exposure treatments, CO2 uptake per 24 hours and light utilization. In late May the number of flower stems, flowers and overall plant quality are assessed.

State of affairs of greenhouse trial at Ter Laak Orchids

The greenhouse experiment at Ter Laak Orchids started in week 42 and is conducted in two experimental greenhouses of 80m² each (43m² net). Four orchid varieties are used: Sacramento, Danube, Las Palmas and Jewel. The plants were 8-10 weeks old at that time. The control greenhouse was fully illuminated with SON-T (1:00 to 17:00) for 16 hours a day. In the 'experimental greenhouse' SON-T is dimmed to 30 mmol/m2/s during early morning and in the afternoon. Also lighting is started 2 hours later and lighting is continued 2 hours longer (dimmed). This is done because last year 'Sacramento' showed that the production of CO2 assimilate from malate starts only more than one hour after illumination and then continues for only 9 to 10 hours. This means that in that period the ‘light sum' must be achieved. By starting the exposure later and by continuing a bit longer a better use is made of the free daylight during the hours that count. After all, by early exposure start at 1.00 am, the malate has been used up around noon, even before the sun has reached the highest point.

An exciting question is whether the rhythm of light utilization has the same effect on different varieties. That is a condition for the practical application of the dim-light strategy for the cultivation with so many varieties together. Photosynthesis measurements performed during propagation show that this more or less the case for the four varieties of the trial. In both greenhouses the plants are growing well and after 13 weeks of cultivation (week 3) not very much difference can be seen. So that is good news. In week 9, the plants are moved to the cooling section and in summer we will see whether the light saving results in equally good quality.

Source: Kas als Energiebron / Sander Hogewoning (Plant Lighting B.V.)