Harvesting Efficiency : Energy Optimization in Quebec’s Greenhouse Sector

In Quebec, greenhouse heating can account for up to 30% of horticultural and market gardeners’ operating costs. Energy efficiency is a concrete way for these facilities to reduce their energy bills and GHG emissions. In this article, we provide an overview of the main measures applicable to this sector, supported by a real-life case study, as well as an overview of the grants offered by Énergir to help you implement these measures effectively.

How an insulating wall can reduce heat loss

For new greenhouses, building a concrete insulating wall approximately one metre high around the perimeter of the greenhouse reduces natural gas consumption while improving the greenhouse climate, particularly in winter. This eliminates the risk of snow buildup around the glass walls and reduces the risk of breakage at the bottom of the walls. In addition, it makes it easier to install greenhouse walls by optimizing the working height and providing a solid foundation for the glass walls.

Automated climate management: Data intelligence for productivity

Automated climate management systems use a computer connected to a network of sensors and probes to adjust humidity, ventilation, air flow and irrigation levels in real time based on the needs in different areas of the greenhouse. They also provide accurate and practical data for production-related decisions. By automatically managing energy, the system also eliminates the risk of oversights or errors that could lead to energy or production losses. It is estimated that this type of system can increase crop yields by 20% to more than 30%.^4,5

Automation to increase greenhouse production density

Automating cultivation using commercially available technologies makes it possible to significantly increase greenhouse production density while reducing human intervention. For example, the amount of lettuce produced on one acre with this type of system is equivalent to that produced on over 50 acres of open field farming and is several times higher than the yield of a traditional greenhouse system.⁶ In addition, an automated system can compensate for labour shortages and optimize space and energy use.

Heat recovery + CO₂ injection: Nothing is lost, everything is transformed

Heat recovery from boiler stacks using thermal storage and CO₂ injection presents multiple advantages. For a greenhouse heated with hot water, capturing heat from boiler flue gases using a heating water return exchanger makes it possible to recover thermal energy by condensing the moisture contained in the combustion products. This system not only increases the thermal efficiency of gas boilers by 10%, but also recovers CO₂ (the other combustion product) to stimulate plant growth. For hot water systems, in the middle of the season, a buffer water reserve is used to heat the greenhouse at a lower cost at night, while during the day, CO₂ is injected at the plant roots to promote growth and vigour.

For example, in most greenhouse crops, the photosynthetic yield increases by 50% when the CO₂ concentration rises from 340 ppm to 1,000 ppm.⁷

Effective measures, backed by the numbers

These various measures can be implemented gradually, depending on a business’s needs and financial capabilities. However, they have all demonstrated their ability to significantly reduce energy use and GHG emissions and foster better crop yields.

For example, Vegpro, Canada’s largest producer of fresh salads and vegetables, has combined different energy efficiency measures in its new greenhouse in Sherrington, Quebec, and is expected to save close to 5 million m³ of natural gas and reduce its GHG emissions by over 9,000 tonnes per year (see box below for details).

Grants that make your job easier

To make it easier to implement energy efficiency measures and accelerate their return on investment, Énergir offers a number of financial incentives for greenhouse farming under its energy efficiency grants program. For program conditions and eligibility criteria, click the links below:

• Up to $4,500 for the purchase of a condensing unit heater
• Up to $50,000 for a feasibility study on implementing energy efficiency measures
• Up to $1,000,000 for the implementation of energy efficiency measures ($1 per m³ of gas saved)

We are here to advise and support you

Do you currently or are you planning to operate a greenhouse and want to learn more about energy efficiency measures that could reduce your energy bill and improve crop productivity? Contact our experts at DATECH, a team dedicated to the success of your projects.

Cimon Desforges, P. eng.
Senior Advisor, Energy Expertise

Pierre-Olivier Nadeau, P. eng.
Senior Advisor, Energy Expertise

DATECH Group