The Roper Solar Greenhouse
Operations
215 Maywood Street, Blacksburg, Virginia
Located in the Hale-YMCA Community Gardens

Back to the main YMCA Solar Greenhouse web page

Regular Procedures

There are regular procedures that need to be done to keep the YMCA Solar Greenhouse in good operating condition.

• Check that the fans are all in good operating condition.
  • Heat-sink fan
  • West-vent-window fan
  • Two ceiling fans
• Check that the temperatures of the two heat-sink thermostats are properly set (70° down to 61° for the cooling thermostat and 50° up to 59° for the heating thermostat).
• Checking that the electric window openers are in good operating condition and that they open at a temperature lower than the temperature that turns on the vent fan.
• Check that the water pump in the cistern is in good operating condition.
• Clean out the screens at the top of the two gutter down spouts and at the end of the cistern overflow pipe.
• Put silicon putty in any cracks that might be letting air infiltrate.
• Change light bulbs that are not working.

Carbon Dioxide Level

There is a CO₂ meter on the back of the center pole of the YSGH. The outside CO₂ concentration is about 387 ppmv (parts per million volume). A tight solar greenhouse can cause the carbon-dioxide (CO₂) level to become low, resulting in slow growth of plants. ("...plants will stop growing when the CO2 level decreases below 150 ppm. Even at 220 ppm, a slow-down in plant growth is significantly noticeable.") The door should be left open as much as possible when the weather is not cold to let fresh air with higher CO₂ in; I suggest leaving it open when the Sun is shining and someone is working in the greenhouse. (Some commercial greenhouses use CO₂ generators to increase the CO₂ to 1000 ppmv or higher. "...increasing the CO₂ level to 1,000 ppm will increase the photosynthesis by about 50% over ambient CO₂ levels")

There needs to be turbulence to move fresh air with CO₂ to the leaves. The YSGH has two features which create such turbulence:

• The ceiling fans should be turned on whenever work is being done in the greenhouse and perhaps turned off otherwise. They can be left on at night.
• The west-vent-window fan will come on at a certain high temperature (after the two vent windows are opened at a slightly lower temperature). This not only creates turbulence but also brings in fresh air from the outside with a higher level of CO₂.

Links

• Factors effecting photosynthesis
• Carbon dioxide in the Earth's atmosphere
  
• Photosynthesis versus carbon dioxide concentration
  
• Photosynthesis versus temperature
  (20° C = 68 ° F, 30° C = 86 ° F)