[TRNSYS-users] problem with collector type 1b - TRNSYS 18

[-- Fed --]

Hi everyone,

I have set up a very simple solar project: just 2 components:

  *   a weather processor type 15

  *   a solar collect or type 1b (with 1 m2 area).

The collector tracks the sun (mode 3) with rotation axis N-S and makes use only of the beam radiation.
Efficiency as function of mean temperature (mode 2).

I get weird results that make me doubt that Type 1b works as it should.

The model is exactly the same every time, but I change the heat loss coefficients (a1 and a2) of the collector.

When both a1 and a2 are 0.0001, the useful output (as returned by type 1) is 4.43E+06 kJ/m2/year.

When a1 is 0.0001, and a2 is 0, the useful output drops unrealistically to to 3.99E+06 kJ/m2/year.

The second results is in agreement (just 0.04% off) with the yearly sum of the quantity
Gb * IAM * eta0
where
Gb is the beam radiation on the surface (i only consider beam component)
IAM is the incidence angle modifier
eta0 is the peak collector efficiency.

However, when i set the heat loss coefficients to their actual values,  the yearly energy output from type 1b is not the sum over the year of the quantity:

Gb * IAM * eta0 - a1*DT - a2*DT^2

but it is about 11% off...

If someone has also had problems with type 1 and got to make it work, it would be great to hear 🙂

Thanks in advance and best regards,

Federico
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