The University of Manitoba solar greenhouse is 22x100 feet. (Photo courtesy Manitoba Hydro)

Dig In: Proof is growing for Chinese greenhouses

When I first saw the Chinese greenhouses on the internet I didn’t know I’d see one this summer.

By Mary Lowther

When I first saw the innovative Chinese greenhouses on the internet I didn’t know I’d have the opportunity to see one this summer.

These amazing, unheated greenhouses work so well that they supply the bulk of vegetables consumed in northeast China. Professor Zhang of Biosystems Engineering at the University of Manitoba, offered to show me a life-sized experimental greenhouse upon which he is still conducting research using alternative energy sources (e.g., biomass and solar) for supplemental heating and LED lighting, on campus. A few days ago I took him up on his offer when we were in Winnipeg and learned that he freely gives of his time to teach others how to make one themselves.

Professor Zhang has supervised many projects, “But”, he says, “Of all the projects I have worked on, this greenhouse is the one most people ask about.” I’m not surprised. He brought these innovative, low tech and low cost plans from China and has overseen the creation and testing of several of the greenhouses. For example, his studies have shown that when the outside temperature reaches a low of -16 C, the greenhouse remains at 9 C, while a conventional greenhouse falls to -11 C. This is 20 degrees warmer and makes a tremendous difference in plant survival, especially considering that this greenhouse is unheated.

The secret to its success lies in combining passive solar energy storage with affordable, locally sourced materials in much of its construction.

When sunlight penetrates the clear plastic cover facing the south, it warms up the interior back wall on the south side.

This wall absorbs and retains heat during daytime and radiates it into the greenhouse at night.

Insulation in this wall and in the east and west walls and a blanket that rolls over (or under) the clear plastic south cover also help to retain heat.

The greenhouse design allows for many adaptations: the north wall can be made of a frame filled with sand, gravel, rammed earth, straw bales or it can abut a building. Some greenhouses in China are dug down three or four feet deep and this soil gets piled up behind the north wall, creating a berm that insulates as well as provides access to the roof. A reflecting, narrow half-ceiling adjoins the upright north wall at an angle facing inward, augmenting winter sunlight coming through the plastic.

The heat-radiating capacity of the opaque northern wall outperforms the clear one on conventional greenhouses.

But how well do they perform under real life conditions in Manitoba? I visited farmer Rene Regnier who had two of these greenhouses built 10 years ago and figured I’d find out from the horse’s mouth. He took me inside one of them, showed me the nine-foot high tomato plants groaning with ripe fruit, walked with me under canopies of cucumbers hanging from wires strung across the inside of the greenhouse, smiled and said, “I love them.”

Please contact mary_lowther@yahoo.ca with questions and suggestions since I need all the help I can get.

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Comments are closed

Just Posted

Provincial success stands out at Cowichan Secondary awards

Wrestling, basketball and field hockey teams earn recognition in shortened year

One piper piping during the pandemic

Tribute to health care workers reaches the 100th performance

Don’t feed the bears, BCCOS warns, after incidents in Cowichan

People have been spotted trying to feed bear near Youbou

The pandemic is widening Canada’s workplace gender gap

Gender pay gap is incentivizing fathers to work while mothers watch children, a new B.C. study has found

Ex-Okanagan Mountie forfeits 20 days’ pay after sexual misconduct review

A former Vernon RCMP constable made sexual comments, grabbed genitals of male officer in two incidents 10 years ago

Man found dead on Okanagan trail identified as Hollywood actor

GoFundMe campaign launched for man found dead at summit of Spion Kop

3 people dead in Prince George motel fire

Fire personnel believe the blaze was suspicious although investigation in early stages

B.C. sets terms to review police, mental health, race relations

MLAs to recommend Police Act changes by May 2021

Feds announce $8.3M to deal with ‘ghost’ fishing gear in B.C. waters

Ghost gear accounts for up to 70 per cent of all macro-plastics in the ocean by weight

Almost 99% less land in B.C. burned this year compared to 2018

2018 was the worst year on record for wildfires

B.C. orders Coastal GasLink to stop pipeline construction near protected wetlands

The 670-kilometre pipeline is planned to transport natural gas from northeast B.C. to Kitimat

Most Read