Greenhouse Crop Transpiration and Water Use
Runs an energy balance to daily transpiration, irrigation volume including the leaching fraction, the peak-hour demand.
Example
You enter
- Floor or canopy area (sq ft) 2880
- Daily solar through glazing (Btu/sq ft/day) 1500
- Crop latent fraction 0.5
- Leaching fraction 0.2
- Peak solar intensity (Btu/h per sq ft) 188
- Irrigation hours per day 12
You get
- Transpiration lb per (day) 2057.14
- Crop transpiration 247 gal/day (2057 lb/day)
- Per square foot 0.0855945
- Irrigation to apply 308 gal/day including 62 gal of leachate
- Peak lb per hour 257.829
- Peak hour demand 30.8962
- Peak to average ratio 1.504
- Moisture into the house air 1972.1
Details, formula, and sources
Runs an energy balance to daily transpiration, irrigation volume including the leaching fraction, the peak-hour demand, and the moisture entering the house air. The worked house uses 247 gal/day and releases 1,972 pints, which a sealed house has to remove.
transpiration = solar energy through the glazing x the crop's latent fraction / 1,050 Btu per pound of water; applied = transpiration / (1 - leaching fraction).
An energy balance. The crop's own stage and the irrigation designer govern; 0.05 to 0.15 gal per square foot per day is the band growers quote.
Public energy balance; the grower band is widely published.
Estimate. AHJ and licensed professional govern.
Field names used by the API: floor_area_sqft, daily_solar_btu_per_sqft, latent_fraction, leaching_fraction, peak_solar_btuh_per_sqft, irrigation_hours_per_day, transpiration_lb_per_day, transpiration_gal_per_day, gal_per_sqft_per_day, applied_gal_per_day, peak_lb_per_hour, peak_gal_per_hour, peak_to_average_ratio, moisture_pints_per_day
- Latent fraction entered; roughly half for a well-watered crop and much lower for a sparse or stressed onegrower observation
- Check the 0.05 to 0.15 gal/sq ft/day band is the sanity check on the energy routeindustry practice