Netherlands: Refrigeration and diffuse glass in roses earned back in 5 years

Extra investments in diffuse glass and refrigeration (together €50/m2), can be recovered in five full production years, as shown by research and calculations from Wageningen UR Greenhouse Horticulture and DLV Plant.

In a 1000 m² greenhouse at GreenQ Improvement Centre, with diffuse glass, refrigeration through OPACs, LED intermediate lighting, active ventilation below the crops, and three screens, a two-year study has been conducted into growing high-quality roses in an energy-efficient manner. Among the conclusions from the study are:
  • Following two years of research with Red Naomi, roses were produced that met the required quality criteria. The production goal in a full production year was 275 roses/m2 and 15 kg per m2. This was realized in the second year. For practical circumstances, this is a high but attainable goal.
  • The reduction in electricity on illumination is 6% in the second year compared to the reference. This is less than the target. The CO2 reduction, with a dosage of 67.9 kg/m2, is over 50%, thus meeting the target. The heat input was lowered to 911 MJ/m2 in the second year, which can be fully fulfilled by using the heat obtained from sunlight during refrigeration.
  • For the control of mildew and botrytis, it is necessary to keep humidity below 85%. This is hard to achieve with an energy-efficient way of production. In the project, it was found that the crop protection hasn't improved with the cultivation technology used.
  • Cutting and bending inwards is essential for the entire development of the bush, and thus for achieving a good production of high quality.
  • The forced ventilation (AVS) with air below the cultivation system, works to keep the crops dry at the bottom, if the absolute humidity outside is lower than the absolute humidity at the bottom of the greenhouse. In the crop, the air absorbs humidity quickly, so that the air humid again at bud level.
  • The intermediate lighting with LED didn't cause improved light utilization efficiency in g/mol light.
  • The OPAC can be used for heating, refrigeration or dehumidification. For each of the three functions, different control of ventilator, flow temperature and pump capacity is necessary for the water flow.
source: Kas als Energiebron

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