The cold season is winding down for the year. But what a cold season it was.  We had record breaking cold this winter curtesy of the wonky Jet stream.  The extremely warm pacific ocean seems to have pushed warm air into the arctic and the jet stream pushed the cold air abnormally south into Toronto.  So the North-East in Canada and the USA was the one place on the globe that had a very cold winter.  A perfect year to test the passive solar prototype.  Every morning when our colleagues were complaining about the extreme cold we were given rather scathing looks when we were excited to run up to the greenhouse and see how it was doing.

 

While we had repeated cold nights down to -25°C (-13°F) we didn’t lose a single plant to frost in the greenhouse. We never added any supplemental heat even on the coldest days.  All the heat provided from the winter sun.

These are the official data from Environment Canada

Month

# frost days

Minimum Nighttime temp

Average Nighttime Temp

Average Daytime Max

January

31

-21.2C (-6.2°F)

-12.3°C (9.9°F)

-2.8°C (27.0°F)

February

28 (of 28)

-25.5°C (-13.9°F)

-17°C (1.4°F)

-12.6°C (9.3F)

March

30

-18.9°C (-2.0°F)

-6.6°C (20°F)

-1.9°C (28.6°F)

April

7

-3.7°C (25.3°F)

2.0°C (35.6°F)

7.5°C (45.5°F)

 

We had a lot of interest from numerous sectors to tour the greenhouse and the number of tours spiked as the cold temperature set in.  Possibly the thought of a chance to go into a greenhouse when the days were so cold helped the interest.  However, all were amazed that our little Passive Solar Greenhaus could work so well up on a windy exposed urban rooftop. We did have days where the wind chill temperature equivalent approached -45°C (-49°F) and we had to shovel a path through the roof snow.

 

One exciting event here at the university was on March 19th when we did a major harvest of greens from the greenhouse to be used for a big salad at our Student Union free lunch.  The students loved the fact that they were eating a salad grown on the university roof during a record cold winter, all with passive solar heating.  I think we made some converts.

The longer sunny days at the end of March and early April held their own challenges.  So much sun meant that on some days in the middle of April the plants hit 30°C (86°F). The plants were loving the sun and really took off with the longer days.  However, this is a bit hot for our growing purposes, although nice for the humans after a long winter.  We upgraded the ventilation fan and system to solve this issue.  We now have a 800cfm gable fan driven by a small solar panel (see photos).  This fan is more than capable of cooling the 100ft2 greenhouse and is even quieter than the old fan.  The vents still open passively and the fan is on a thermostat set at 25°C and is working beautifully.

Creator: 
Sponsor(s): 
Image of green plants growing indoors
Image of green plants growing indoors
Image of green plants growing indoors
Image of green plants growing indoors
Image of green plants growing indoors
Image of ventilation equipment
Image of a solar panel on a roof
Tuesday, May 5, 2015 - 7:15pm
Lab Member: 
Ian D. Clarke

Overview

Tuesday May 5th, 2015
Image of green plants growing indoors

The cold season is winding down for the year. But what a cold season it was.  We had record breaking cold this winter curtesy of the wonky Jet stream.  The extremely warm pacific ocean seems to have pushed warm air into the arctic and the jet stream pushed the cold air abnormally south into Toronto.  So the North-East in Canada and the USA was the one place on the globe that had a very cold winter.  A perfect year to test the passive solar prototype.  Every morning when our colleagues were complaining about the extreme cold we were given rather scathing looks when we were excited to run up to the greenhouse and see how it was doing.

 

While we had repeated cold nights down to -25°C (-13°F) we didn’t lose a single plant to frost in the greenhouse. We never added any supplemental heat even on the coldest days.  All the heat provided from the winter sun.

These are the official data from Environment Canada

Month

# frost days

Minimum Nighttime temp

Average Nighttime Temp

Average Daytime Max

January

31

-21.2C (-6.2°F)

-12.3°C (9.9°F)

-2.8°C (27.0°F)

February

28 (of 28)

-25.5°C (-13.9°F)

-17°C (1.4°F)

-12.6°C (9.3F)

March

30

-18.9°C (-2.0°F)

-6.6°C (20°F)

-1.9°C (28.6°F)

April

7

-3.7°C (25.3°F)

2.0°C (35.6°F)

7.5°C (45.5°F)

 

We had a lot of interest from numerous sectors to tour the greenhouse and the number of tours spiked as the cold temperature set in.  Possibly the thought of a chance to go into a greenhouse when the days were so cold helped the interest.  However, all were amazed that our little Passive Solar Greenhaus could work so well up on a windy exposed urban rooftop. We did have days where the wind chill temperature equivalent approached -45°C (-49°F) and we had to shovel a path through the roof snow.

 

One exciting event here at the university was on March 19th when we did a major harvest of greens from the greenhouse to be used for a big salad at our Student Union free lunch.  The students loved the fact that they were eating a salad grown on the university roof during a record cold winter, all with passive solar heating.  I think we made some converts.

The longer sunny days at the end of March and early April held their own challenges.  So much sun meant that on some days in the middle of April the plants hit 30°C (86°F). The plants were loving the sun and really took off with the longer days.  However, this is a bit hot for our growing purposes, although nice for the humans after a long winter.  We upgraded the ventilation fan and system to solve this issue.  We now have a 800cfm gable fan driven by a small solar panel (see photos).  This fan is more than capable of cooling the 100ft2 greenhouse and is even quieter than the old fan.  The vents still open passively and the fan is on a thermostat set at 25°C and is working beautifully.

Image of green plants growing indoorsImage of green plants growing indoorsImage of green plants growing indoorsImage of green plants growing indoorsImage of ventilation equipmentImage of a solar panel on a roof

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