SP0163: Solar Greenhouse Heating

Status: COMPLETED February 2017 - 2018

The Solar Greenhouse Heating Project seeks to improve the heating system of the Macdonald Campus Horticultural Centre by replacing the current heating method with a solar thermal heating system. The solar thermal heating system for the greenhouse system will collect heat through a heat absorber placed outside the greenhouse. The overall goal is to lengthen the growing season of the Horticultural Centre's greenhouse through the construction of a sustainable and efficient seed bed heating system.

Read the full project description

While most crop seeding begins in April, certain crops – such as onions, must be seeded as early as late-February, at which time the average greenhouse temperature without supplemental heat is too low for effective germination and plant growth. Thus, onions must be first seeded indoors, and then moved to the greenhouse when temperatures are more favourable. Indoor seeding poses many inconveniences; the seeds do not receive adequate sunlight resulting in slower and less successful plant growth, watering the seeded trays is more difficult as building drainage must always be considered, physically moving the seedlings from the indoor building to the greenhouse is time consuming and may stress the young plants, and finally the indoor building must be heated for the plants when it would otherwise not be used, thus posing an economic strain. Therefore, in consultation with Michael Bleho, the chief technician at the Horticultural Centre, an improved heating system to extend the growing season in the greenhouse would be beneficial. 

The solar heating system addresses the aforementioned issues by allowing the seeded trays to be placed directly in the greenhouse for germination, rather than indoors. This will reduce energy consumption as the indoor building will not have to be heated. Environmentally, the system promotes sustainability through the use of renewable energy sources. Furthermore, it will promote economic sustainability as we will be using the solar thermal heaters from SOLCAN, a local Canadian company. Finally, from a social dimension, the improved heating system will act as an educational tool for both students and community members who tour the farm, and conduct research projects.

A solar thermal heating system for the greenhouse system will collect heat through a heat absorber placed outisde the greenhouse. Two Solcan 3001 Liquid Finned Tube Collectors are currently available for this use at the Horticultural Centre. Heat will then dissipate to a water-glycol mixture moving through the absorber to an insulated collector. One Solcan storage tank is available. After the heated liquid is stored in the collector, it will be pumped through insulated PEX cross-linked polyethylene piping to into the greenhouse, where the tubing will run directly under the tables where the seed beds are placed. This will allow the heat from the tubes to be dissipated to the seed beds and assist in germination.

The project will continue after funding and construction with significantly lower running costs compared to the current system. The system also allows for easy modification and expansion, should the greenhouse be upgraded in the future. The design also serves as a model for sustainable heating, which can be used to inspire modified designs for heating other sectors of McGill in the future.

Funds from the SPF will be used to compensate a student overseeing the construction of the Heating system. Resources from the SPF will also be used to purchase a pump and various construction materials. 

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ryan.hendry [at] mail.mcgill.ca (Ryan Hendry)

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