Fuel Cell Model in TESPy Issue

[Barandier]

Hello everyone,

I've bee working in model of a Fuel Cell and I tried to create a model from the code available in TESPy website, nevertheless, it arises the following issue when it runs:

"The solver does not seem to make any progress, aborting calculation. Residual value is 2.63e+02. This frequently happens, if the solver pushes the fluid properties out of their feasible range.

Process finished with exit code 0"

As you can see, my code is very similar to the one available in the website as it follows:

from tespy.components import (Sink, Source, FuelCell)
from tespy.connections import Connection
from tespy.networks import Network
from tespy.tools import ComponentCharacteristics as dc_cc


nw = Network(T_unit='C', p_unit='bar', v_unit='l / s', iterinfo=False)

fc = FuelCell('fuel_cell')
fc.component()
# Primary Circuit
oxygen_source = Source('oxygen_source')
hydrogen_source = Source('hydrogen_source')
water_sink = Sink('water_sink')

# Secondary Circuit
air_inlet = Source('air_outlet')
air_outlet = Sink('air_inlet')

oxygen_in = Connection(oxygen_source, 'out1', fc, 'in2')
hydrogen_in = Connection(hydrogen_source, 'out1', fc, 'in3')
water_out = Connection(fc, 'out2', water_sink, 'in1')

air_in = Connection(air_inlet, 'out1', fc, 'in1')
air_out = Connection(fc, 'out1', air_outlet, 'in1')


nw.add_conns(air_in, air_out, oxygen_in, hydrogen_in, water_out)

fc.set_attr(eta=0.45, P=-200, Q=-200, pr=0.9) 

air_in.set_attr(T=25, p=1, m=1, fluid={'air': 1})
oxygen_in.set_attr(T=25, fluid={'O2': 1}) 
hydrogen_in.set_attr(T=25, p=0.5, fluid={'H2': 1})


nw.solve('design')
P_design = fc.P.val
round(P_design, 0)
round(fc.eta.val, 2)
nw.print_results()

Additionally, even when testing the code available in the website, the same issue arises, but with a larger residual value.

Could someone help me with that please?

Lastly, I know that the "dc_cc" stands for direct current, nevertheless, how is it applied to the code later?

[fwitte]

Hi @Barandier,

thank you for reaching out! The underlying issue is the specification of both heat and power output. With the heat output your are essentially setting the temperature of the outlet water. The larger the heat output is, the lower the temperature. In your case, for the small mass flow of the gases the water temperature exceeds the limits of the fluid property database because the heat output is quite small. You can change by setting the water outlet temperature instead of the heat production and then play with the values to see how it is affected. For example

fc.set_attr(eta=0.45, P=-200, pr=0.9) 
water_out.set_attr(T=50)

will result in a converged solution.

Best

Francesco

[fwitte]

code available in TESPy website

Ah, oh and thank you for pointing this out! I will fix it, it is actually an issue, which was not caught by mistake!