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Hi
I am doing a simulation on PV farm output
I realise that the energy output for using polycrystalline module will be higher than that of monocrystalline module. In the software, i tested with 13048 of LG230 P1C-G2 Si- Poly with modules and the simulation yield 3154kWh whereas for 11664 LG 230 M1-G2 and the simulation yield 3152 kWh, next I simulate with 37170 module of FS-280 Thin film module and found out that the yield was 3615kWh. Why is the plant yield for thin film module higher than the polycrstalline and mono crystalline despite it having the lowest efficiency at modular and cell level? Next is why is the plant yield for polycrstalline higher abeit with small differences than monocrystalline despite it having lower efficiency at modular and cell level? Your help will be greatly appreciated

Sorry, I don't understand your numbers.
For the yield, you are probably speaking of Specific production, expressed in [kWh/kWp]. But such a high productivity is completely out of standards.

However the Specific production doesn't depend on the Efficiency of the modules at STC.
When you install 1000 kWp of modules, the production will be related to the Nominal power, not the efficiency.
With lower efficiency, you will have a greater area, but still 1000 kWp installed ...

Now the differences in yield may arise due to the temperature behaviour and low-light sensitivities of the modules.
And this is dependent on specific model parameters (namely Rserie), which are not always known with accuracy.
See our FAQ What explains the difference in Yield between different modules?

PVsimulator,

Module efficiency shows up in the amount of W/area you can get. If you compare the W/area rating of similar size mono, poly, and thin film modules with equivalent cell active area you will find that mono will have the highest, poly the next highest, and thin film the lowest. High efficiency, for the most part, gets you more power per unit area.

My guess would be that you are basing your project on a given system size in kW and allowing the number of modules to fluctuate which reduces the effect of the differences in efficiency between the different module types. If you have for instance 10kW of mono, poly, and thin film they are all going to have a 10kW array rating but there will be many fewer mono modules than thin film. This is why thin film is favored for large ground mount systems and mono or poly for space constrained roof mounted systems, as long as thin film is much cheaper.

As André said some modules have an advantage in lower light performance. Looking at equivalent sized arrays this effect is going to be what stands out. But there is still some disagreement over how to model the modules to allow for these differences so the model files you are using might have unrealistically high low light performance.