Greenhouse CO2 Enrichment Rate and Cost
Computes the initial charge and the makeup rate from house volume, the concentration lift, and the air change rate.
Example
You enter
- House volume (cu ft) 43200
- Ambient CO2 (ppm) 400
- Target CO2 (ppm) 1000
- Air changes per hour, closed 1
- Gas price ($/lb) 0.1
- Air changes per hour, venting 30
- Floor area (sq ft) 2880
- Enrichment hours per day 10
You get
- Initial charge 25.9 cu ft (2.95 lb), a one-time fill
- Makeup, closed house 25.9 cu ft/h = 2.95 lb/h
- Makeup lb per hour 2.9497
- Cost, closed house 0.29497
- Makeup while venting 778 cu ft/h = 88.5 lb/h
- Vented lb per hour 88.4909
- Cost while venting 8.84909
- Closed-house rate 1.0242
Checked against published worked examples from: Cannabis Business Times (GIE Media), article by John W. Bartok Jr., UConn emeritus...
Details, formula, and sources
ScopeComputes the initial charge and the makeup rate from house volume, the concentration lift, and the air change rate, closed and venting. The worked house costs $0.30 an hour closed and $8.85 venting for the same 1,000 ppm, which makes interlocking the injector to vent position the whole control strategy.
Formula or tableinitial charge = house volume x concentration lift; makeup = volume x air changes per hour x the lift + the crop's own CO2 use; mass at 0.1138 lb per cubic foot of carbon dioxide.
Source and editionAmbient is about 400 ppm and 1,000 to 1,500 ppm the customary target. The crop's uptake, the supplier's data, and any combustion safety requirements govern.
Free accessPublic mass balance; supplier sizing tables are quoted per 1,000 square feet.
What governsEstimate. AHJ and licensed professional govern.
API field nameshouse_volume_ft3, ambient_ppm, target_ppm, air_changes_per_hour, gas_price_per_lb, vented_air_changes_per_hour, floor_area_sqft, enrichment_hours_per_day, initial_charge_ft3, makeup_ft3_per_hour, makeup_lb_per_hour, hourly_cost, vented_makeup_ft3_per_hour, vented_lb_per_hour, vented_hourly_cost, lb_per_1000_sqft_per_hour
- Mixing a well-mixed house at steady state is assumed; the crop's own CO2 use is entered separately and ADDED to the leak makeup (Bartok: about 11.5 cu ft per hour for a 30 x 128 ft house)spec-v1755 scope
- Combustion an unvented burner adds water and combustion products; its own safety requirements applyequipment listing