Method for controlling the pressure in an anode of a fuel cell, and a fuel cell

A method for controlling the feedback of hydrogen from a reservoir to an anode of a fuel cell, comprising the following steps:

• feeding hydrogen to the anode via a feed-pressure control unit;
• feeding oxygen or air to a cathode;
• periodically discharging a mixture which consists of a gas portion and a condensate, from the anode in a discharge cycle via a discharge line and a discharge-pressure control unit to a reservoir by periodically opening the discharge pressure control unit when the pressure prevailing in the reservoir is lower than the pressure in a feed means of hydrogen, the discharge cycle comprising the following steps:
• (d) increasing the pressure prevailing in the feed means of hydrogen above a desired value,
• (e) opening the discharge-pressure control unit for discharging the mixture to the reservoir when the increased pressure is achieved,
• (f) maintaining the increased pressure prevailing in the feed means of hydrogen during discharging of the mixture to the reservoir so that the pressure in the reservoir is increased,
• collecting and separating the mixture in the reservoir into a gas portion and a condensate;
• feeding the gas portion back to the anode without the use of a hydrogen pump, the step of feeding the gas portion back comprising the following steps:
• i. closing the discharge-pressure control unit and the feed-pressure control unit when a difference between the pressure in the anode and the pressure in the reservoir reaches a preset minimum level;
• ii. opening the discharge-pressure control unit when the pressure in the anode drops to a pre-set threshold level, whereupon hydrogen in the reservoir is fed back to the anode without the use of a hydrogen pump, due to the pressure difference between the reservoir and the anode;
• and
• iii. closing the discharge pressure control unit and opening the feed pressure control unit when the pressure in the reservoir drops to a desired value.

A fuel cell comprising:

• at least one cell with one anode and one cathode each,
• a hydrogen-feed means connected with the anode, said hydrogen-feed means comprising a feed-pressure means,
• an oxygen-feed or air-feed means connected to the cathode;
• a discharge line connected to the anode, said discharge line comprising a discharge-pressure control unit, for discharging a mixture consisting of a gas portion and a condensate,
• a reservoir connected with the discharge line and with the anode via a feedback line for feeding back hydrogen separated from the reservoir;
• a feedback-pressure control unit arranged in the feedback line;
• and
• a control means connected to the feedback-pressure control unit, the feed-pressure control unit and the discharge-pressure control unit, so that the control means opens the discharge-pressure control unit for periodically discharging the mixture, and the mixture is conveyed into the reservoir via the discharge line when the pressure prevailing in the reservoir is lower than that in the feed means of hydrogen,
• wherein the control means is configured to control the pressure prevailing in the reservoir based on the pressure in the feed means of hydrogen,
• wherein during discharge, the control means is configured to increase the pressure in the feed means and maintain the increased pressure until the pressure difference between the feed means of hydrogen and the reservoir reaches a preset minimum level,
• wherein during feedback, the control means is configured to close the feed-pressure control unit and discharge-pressure control unit when the pressure difference reaches the preset minimum level, which then reduces the pressure in the anode to a threshold value that substantially corresponds to the desired value of the pressure prevailing in the reservoir, and opens the feedback pressure control unit after the threshold value in the anode is reached to supply the anode with hydrogen from the gas portion in the reservoir via the feedback line without the use of a hydrogen pump,
• wherein when the pressure in the reservoir reaches the desired level, the control means is configured to close feedback-pressure control unit and opens the feed-pressure control unit to finish the discharge cycle.