GES

Greenhouse Energy Simulation

Introduction

This code simulates heat, mass and CO₂ exchange in an unheated, ventilated single-zone greenhouse for a simple test case. The heat transfer processes simulated include convection, conduction and radiation, together with plant transpiration for simulation of heat and mass exchange due to evaporation of water from the leaf surface. Simple models of photosynthesis and crop growth for tomatoes are included in order to simulate CO₂ exchange. The model is based on the GDGCM (Pieters, J. and Deltour, J., 'The Gembloux Dynamic Greenhouse Climate Model - GDGCM', 2000 ) and on the thesis by Vanthoor (Vanthoor, B.H.,'A model-based greenhouse design method', PhD Thesis, Wageningen University, 2011).

How to run model

There are two versions included here, written in MATLAB and python3.

For the MATLAB version, the files included here are as follows:

• GESModel.m

  This is the main MATLAB file which initialises and calls the differential equation solver ode15s with derivatives.m. Using parameters.m and the weather data in SampleWeather.csv, running GESModel.m provides time histories of temperature, air moisture content and CO₂ concentration.

• derivatives.m

  Contains the governing heat, mass and CO₂ balance equations for solution at each timestep

• parameters.m

  Contains parameters for greenhouse and plant geometry and material properties

• climterp_linear.m

  Sub-routine called by GESModel.m to interpolate weather data according to the timestep specified in parameters.m

• lamorturb.m

  Sub-routine called by derivatives.m in order to calculate whether flow is laminar or turbulent for convection calculation

• sat_conc.m

  Sub-routine which converts relative humidity into air moisture content.

• PlotResults.m

  Routine for plotting time histories of temperature, moisture content, relative humidity and CO₂ concentration output by GESModel.m

• SampleWeather.csv

  Hourly input weather data, in the format 'Hour, Ambient Temperature (^oC), Sky Temperature (^oC), Windspeed (m/s), Relative Humidity (%), Direct Solar Radiation (order NE wall, NE Roof, SE Wall, SE Roof, SW Wall, SW Roof, NW Wall, NW Roof) (W/m²), Diffuse Solar Radiation (order as for Direct)(W/m²)

The model has been run with MATLAB R2018a https://uk.mathworks.com/products/matlab.html

The python version is similar except that the functions are all contained within the file functions.py, with parameter values in parameters.py which is called by the main file, GES_Example.py.

Sample data

The example given is a single zone unheated greenhouse, dimensions 10 x 25 x 5m with no artificial lighting or supplemental CO₂, as illustrated.

The heat, mass and CO₂ exchanges are modelled as indicated.

Project status

This code is under development and has been modified for use in multi-zone, rooftop and underground greenhouses. More information can be found under the University of Cambridge Engineering Department Energy Efficient Cities initative website here: https://www.eeci.cam.ac.uk/research/greenhouse-energy-simulation

Citation

If using this code for development or research please cite as: