Structures & Equipment
Greenhouse design to help reduce costs
By Alberta Agriculture and Forestry
By Alberta Agriculture and Forestry
An Alberta Agriculture and Forestry specialist says commercial greenhouses in Alberta should be able to benefit from some new research into construction materials and greenhouse design. “Greenhouses have traditionally been energy intensive operations, but with increasing scrutiny and slowly shrinking margins, producers need to find ways of trimming costs wherever possible,” says Dustin Morton, commercial horticulture specialist with Alberta Agriculture and Forestry.
Dr. Silke Hemming of Wageningen University in the Netherlands has done research on making greenhouses more energy efficient by maximizing the sunlight absorbed by the greenhouse and increasing the total amount of energy captured.
“In the daylight greenhouse designed by Dr. Hemming, sunlight shining through the roof is focused onto a Fresnel lens. This lens allows the sunlight to be directed to collectors that then generate heat or electricity for the greenhouse. The light filtering down to the crop is diffused for better canopy penetration and, in this case, is best used for pot plant production. A leading orchid producer in the Netherlands has constructed a production facility using this method with expected energy savings nearing 50 per cent.”
Hemming’s winterlight greenhouse aims to increase sunlight in the greenhouse by 10 per cent during the winter while also increasing crop light use efficiency by 10 per cent. “While an initial analysis of roof shape and angle netted no new results, ultimately a combination of glazing and structure coating, use of diffuse glass, installation of energy curtains and crop management were used to achieve this goal.”
Morton points out that the innovative use of angled energy curtains in the winterlight greenhouse has yielded additional energy savings. “Rather than staying horizontal (flat along the greenhouse eaves), the new curtains follow the angle of the greenhouse peak to maximize light penetration through the material, and minimize the impact of the curtain. This design has shown an increase in light of 10-12 per cent over conventional construction.”
Morton points out that energy efficiency works well even on a commercial scale. “Two more Dutch designs, the VenLowEnergykas and 2SaveEnergykas, began with the goal of combining high levels of energy savings with high levels of production. Where these two differ from each other is in the materials used in their glazing. 2SaveEnergykas uses a layer of glass and a layer of rigid poly, whereas VenLowEnergykas uses a much more expensive double layer of glass in order to realize the highest level of energy savings. When coupled with antireflective (AR) coatings and a dehumidification system, these two approaches showed energy savings of 50 per cent in research trials.”
Morton says 2SaveEnergykas’ more affordable approach has since been adopted into commercial production and has reduced gas consumption by what he says is an “astounding” 50 per cent.
“Commercial greenhouses use tremendous amounts of power, including heating, fans and lights. While building a state of the art greenhouse may not be an option, Dr. Hemming’s research suggests that even smaller steps can make a difference. This includes relatively simple things like applying antireflective coatings on your glazing material, painting structural materials to increase reflection, and installing an energy curtain. Any step you take to increase the energy efficiency of your greenhouse will benefit your bottom line and ultimately contribute to the success of your business.”