How can a do a greenhouse temperature simulation?

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An interesting problem.

OpenStudio doesn't have a way of specifying indoor vegetation. The green roof model reference may have some helpful equations for calculating the evapotranspiration rate.

You'll need to do a calculation to get the latent load from your plants, and then create an Other Equipment object with latent fraction set to 1, following a schedule you make.

This won't work if your space is unconditioned and the temperature of the space and evpotranspiration rate are dependent on each other. In that case, you may need to make a functional mockup unit and specify an equation linking the variables there. See this question for how to make these.

There are enough open questions (how much infiltraiton is the space? how frequently do you water the plants? etc.) that you may be better off doing a rough calculation in a spreadsheet before trying out a heavier tool like OpenStudio/EnergyPlus.