U of Guelph researchers test more efficient energy-use models

In Essex County, Ont., the nighttime sky glows orange and greenhouses dominate the landscape. It’s the result of the rapidly growing greenhouse industry in Ontario, one that paid close to $194 million for energy in 2021, according to Statistics Canada.

But energy is still in short supply.

“There are growers who want more greenhouses,” said Dr. William David Lubitz, a professor in the School of Engineering at the University of Guelph’s College of Engineering and Physical Sciences. “Right now, however, there are limits on hooking up large electricity users because the local grid is maxed out at its peak.

“They’re trying to expand the capacity for gas and electricity there, but frankly, it’s stretched.” So how can this growing industry optimize its energy use? That’s the question behind Lubitz’s research and latest project development: a model programmed to simulate greenhouse energy use and growing conditions in order to help producers save energy and money.

The model was recently published in the conference proceedings of the Symposium on Responsible Engineering and Living. This research was funded by the Ontario Agri-Food Innovation Alliance, a collaboration between the Ontario Ministry of Agriculture, Food and Rural Affairs and the University of Guelph.

Dr. Lubitz describes greenhouses as sensitive buildings, responsive to wind and outside temperatures amid an array of meteorological conditions.

The model, developed by

Lubitz’s former master’s student Alex Nauta, considers those properties and others to help growers reduce energy costs without jeopardizing yields. It also helps in identifying ideal design parameters for future greenhouses. The model was tested on six greenhouses in southwestern Ontario, mostly in Essex County.

“The really neat thing was it worked,” said Lubitz. “Over and over, Alex’s model predicted what should be happening in the greenhouse. If a temperature that actually happened in the greenhouse was a certain temperature, the model predicted that same temperature.”

The model’s success means Lubitz and his team can help growers identify ways to reduce energy use. They can also virtually test various scenarios growers wouldn’t chance taking, such as changing the temperature or not running fans to circulate air because it may hurt their crop.

“We can try all these different things and see the results. If we find good ones, we can go back to the grower, and say, ‘Look, not only do we think this would work, but we have this model that we’ve checked, and we have confidence that it says this will work,’” explained Lubitz.

Novel technologies reduce costs

The next step is to help growers determine whether adapting new technologies to balance their energy costs and greenhouse climates is feasible. The model, he says, will help growers identify how to save costs. For example, if growers are constantly running fans to cool their greenhouse during the day, they might invest in encapsulated

Milstop foliar fungicide now labeled for powdery mildew on greenhouse cucurbits

Apply at a rate of 0.28 to 0.56 kilograms per 1000 sq. m. or 1/10 hectare. Use a sufficient volume of spray solution to obtain complete coverage of foliage and stems. Uniform and complete coverage of the foliage is essential for the most effective results. Spray volume per unit of treated area can vary depending upon plant type and stage of development. Number of applications will depend upon disease pressure. Do not exceed a use rate of 0.56 kilograms of MilStop Foliar Fungicide per 1000 sq. m. or 1/10 hectare, per application. Do not store unused spray solution. Dispose of unused solution on site.

For a copy of the new minor use label contact your local extension specialist, regional supply outlet, or visit the PMRA label site www.hc-sc.gc.ca/cpsspc/pest/registrant-titulaire/toolsoutils/label-etiq-eng.php phase-change materials, such as coconut oil, that trap heat as they melt and release it as they cool. The model could be used to help growers see if this change would reduce electricity costs.

Other technologies are being employed, too, such as dehumidifiers to remove excess moisture and ceiling curtains to reduce heat loss and prevent nighttime light pollution – the focus of work by another student of Lubitz’s. Curtain use to reduce light pollution is now mandated in several jurisdictions.

“Anything we can do to reduce the carbon footprint of the industry reduces costs,” says Lubitz. “If you reduce the costs to grow, you reduce the costs of food and get more locally grown food with less of an environmental impact.”

Source: University of Guelph January 26, 2023 news release

Josh Mosiondz

The Pest Management Regulatory Agency (PMRA) recently announced the approval of a minor use label expansion registration for Milstop foliar fungicide for suppression of powdery mildew on greenhouse grown cucurbits (CG 9) in Canada. Milstop foliar fungicide was already labeled for powdery mildew on a wide range of crops in Canada. This minor use proposal was submitted by the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec as a result of minor use priorities established by growers and extension personnel.

The following is provided as an abbreviated, general outline only. Users should be making disease management decisions within a robust integrated disease management program and should consult the complete label before using Milstop foliar fungicide.

To reduce runoff from treated areas into aquatic habitats avoid application to areas with a moderate to steep slope, compacted soil, or clay. Avoid application when heavy rain is forecast. Contamination of aquatic areas as a result of runoff may be reduced by including a vegetative filter strip between the treated area and the edge of the water body.

Follow all other precautions, restrictions, and directions for use on the Milstop foliar fungicide label carefully.