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# Air-based BIPV/T and transpired solar collector

Hi

I am going to model an air-based BIPV/T system integrated with a transpired solar collector. My problem is that I can not assign the outlet air node of BIPVT as an input for transpired collector. This system is going to be monitored after construction and its really important for me, to use the full capacity of E+ to simulate the system and the building as accurate as possible.

thx

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The way to think of this is that the surface of the transpired collector is the PV. The two are integrated together as one thing. EnergyPlus can do this and it is demonstrated in the example file called TranspiredCollector.idf.

It doesn't really make sense for a transpired collector to have an inlet from another device like PVT. The whole idea with transpired collect is to have a diffuse set of holes that draw in ambient air to eliminate convection off the face of the collector.

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Thanks I think I am totally confused with different ways available in E+. First, My Model is a PVT system, but I am really looking for a way to model the thermal energy absorbed by the system. The PVT model available, asks for a thermal coefficient which doesn't seem accurate to me and also I do not know its value. What I am looking for is a BIPV, with just one opening at the bottom and an outlet node. Is there any way to accurately find the temperature of that outlet air node using purely the natural convection between the PV and the roof?

( 2015-10-17 13:03:38 -0500 )edit

Another way is using external vented cavity, but again, in the external vented cavity model, the air temperature is well mixed in the cavity. My ultimate goal is after modeling this PVT system, use the outlet node for an air solar collector (Transpired) inlet. In this stage, I don’t really care about the electricity, so is there any way to model that cavity accurately if I am not using the PV. I mean using the characteristic of the PV surface just to model the thermal part accurately

( 2015-10-17 13:03:49 -0500 )edit

SolarCollector:UnglazedTranspired is very similar to the external vented cavity. In fact the generic external vented cavity (SurfaceProperty:ExteriorNaturalVentedCavity) originally came from the need to model times when the transpired collector is sitting idle with no air drawn in. The outlet node from the transpired collector can go into an air handler. It sounds like you don't really need to also use SolarCollector:FlatPlate:PhotovoltaicThermal, that is for a more generic model of PVT.

( 2015-10-17 13:31:44 -0500 )edit

Thank you. As I got from your answers and also reading the Engineering Reference, current version of E+, is not able to model what I am looking for. because if I use the SolarCollector:FlatPlate:PhotovoltaicThermal, All the thermal energy of the cavity, is calculated based on the " value for thermal conversion Efficiency input" that I enter and which doesn't seem accurate to me. And If I use the Transpired Solar collectors as you mentioned, I can not model just one opening in the bottom of the system.

( 2015-10-18 07:16:08 -0500 )edit