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oemof / oemof-solph

A model generator for energy system modelling and optimisation (LP/MILP).
https://oemof.org
MIT License
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"GenericCHP" with back-pressure characteristic use always the conversion losses of the maximum input flow value #783

Open c-franz opened 3 years ago

c-franz commented 3 years ago

Hi,

I use the class “GenericCHP” with the “back_pressure” parameter setting to create a fixed linear relationship between the input and the two outputs.

When the chp component produces the minimum output power, the ratio between the minimum input flow value and the two minimum output flow values are not correct. --> The conversion losses of the maximum input flow value (H_L_FG_max) are used instead of the minimum input flow value (H_L_FG_min)

fixed_chp_input_outputs

When it produces the maximum output power, the ratio is correct because it used the conversion losses of the maximum input flow value (H_L_FG_max) every time.

Is that a bug or it cannot be implemented in any other (mathematical) way?

fixed_chp_example.zip

fwitte commented 2 years ago

Hi,

sorry for the very late answer. H_L_FG_max and H_L_FG_min are only used for the internal combustion engine. They refer to the flue gas losses at the right (max heat extraction) and left (min heat extraction) side of the PQ diagram. For the backpressure turbine the H_L_FG_share_min values do nothing, as there is no possibility to change the heat output given the power output (it is always at maximum possible heat extraction).

Appart from that, I am unsure, how and if it is possible to implement a gradient in the flue gas losses within the backpressure ramp...

Best regards

Francesco