how turn off Energy solver in PEM fuel cell
 

I'v use PEM fuel cell module and disable Joule and reaction heating , because I want to model a Isothermal PEM fuel cell And when in the model section I disabled energy I received two errors
1- One about density method.
(When I changed density of mixture in material section to " compressed ideal gas" The error disappears )
2- And the other about improper list (fatal error due to initiation #F)
So I cant run the program,
how can I solve the problem in isothermal condition ?

thanks