Climate under Cover
Digital Dynamic Simulation in Plant Bio-Engineering

Greenhouse Models

Greenhouse with Pad and Fan, Double-Poly Greenhouse

This page converts CUC35 and CUC50 into browser-based tools for greenhouse climate, humidity ratio, and layered energy balance.

These MATLAB models track temperature, humidity ratio, and multi-layer energy exchange, so the web version preserves the original state variables.

MATLAB sources for cuc35.m and cuc50.m are preserved in matlab-source/cuc20-50 for reference.

CUC35

Greenhouse with Pad and Fan

Tracks the cover, soil floor, three air temperatures, three humidity ratios, and four soil layers under pad-and-fan cooling.

Pad and fan greenhouse diagram
Pad-and-fan greenhouse layout used for the CUC35 explanation

CUC50

Double-Poly Greenhouse

Extends the model to an outer cover, inner screen, inside air, plant surface, floor, soil layers, and humidity ratio.

Double-poly greenhouse diagram
Double-poly greenhouse layout used for the CUC50 explanation

Implementation

Model translation

  • The original MATLAB files call Pad and fan for CUC20, CUC30, and CUC50, and Double poly for CUC35.
  • Default parameters follow the original example settings for direct comparison.
  • When the equations become numerically unstable, the status line reports it rather than silently drawing empty charts.

Formula Notes

Key greenhouse relations

  • FWS(T) = 0.622 * PWS(T) / (Patm - PWS(T)) gives saturation humidity ratio, where T is temperature in °C and FWS is in kg/kg.
  • ITI = [HI(TS - TI) + CA*QH(TO - TI) + 2*HI*ARTO*LAI(TP - TI) + HI(TF - TI)] / (CA*AH) is the indoor-air temperature rate used in CUC50.
  • IWI = [RHO*QH(WO - WI) + KM(GSI*WSTF - WI) + 2*LAI*ARTO*RHO/GAM*(WSTP - WI)] / (RHO*AH) is the indoor humidity-ratio rate, including plant and floor vapor exchange.
  • TC, TS, TI, TP, and TF are temperatures in °C; WI and WO are humidity ratios in kg/kg; QH is airflow in m³/m²/hr; ARTO and LAI are dimensionless.
  • HI is convection coefficient in W m-2 °C-1, CA is volumetric heat capacity of air in kJ m-3 °C-1, AH is greenhouse air depth in m, RHO is air density in kg/m³, KM is mass-transfer coefficient in m/hr, GSI is soil evaporation efficiency, WSTF and WSTP are saturated humidity ratios in kg/kg, and GAM is the psychrometric constant.