@classmethod
def get_suitable_heating_agent(cls, T_pinch):
    """
        Return a heating agent that works at the pinch temperature.
        
        Parameters
        ----------
        T_pinch : float
            Pinch temperature [K].
        
        """
    for agent in cls.heating_agents:
        if T_pinch < agent.T:
            return agent
    raise RuntimeError(f'no heating agent that can heat over {T_pinch} K')
