Improved construction materials and design are making greenhouses more efficient and cheaper to operate, says a provincial horticulture specialist.
“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,” said Dustin Morton.
For example, research by Silke Hemming of Wageningen University in the Netherlands has shown how to make greenhouses more energy efficient by maximizing the sunlight absorbed and 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,” said Morton. “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.”
For winterlight greenhouses, Hemming set a goal of capturing 10 per cent more sunlight while boosting a crop’s 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,” said Morton.
Innovative use of angled energy curtains in the winterlight greenhouse yielded additional energy savings, he said.
“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 to 12 per cent over conventional construction.”
That energy efficiency works well even on a commercial scale, said Morton.
“Two more Dutch designs — the VenLowEnergykas and 2SaveEnergykas — began with the goal of combining high levels of energy savings with high levels of production.”
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 anti-reflective coatings and a dehumidification system, these two approaches showed energy savings of 50 per cent in research trials,” he said.
The more affordable 2SaveEnergykas system has since been adopted into commercial production and reduced gas consumption by what Morton called an “astounding” 50 per cent.
Building a state-of-the-art greenhouse may not be an option, but Hemming’s research shows smaller steps make a difference, he added.
“This includes relatively simple things like applying anti-reflective 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.”