Fuel Cell Humidification
Recently, we received a new Humidifier from our longtime friends at FumaTech. Although the previous one was rated for a higher power (100kW), we have switched to a smaller but more modern humidifier, rated to fuel cells up to 70kW. The newer generation part is more efficient, because of its different architecture, and should yield better performance. In addition to this, the new part is 5kg in weight, saving us 2kg off of the old one!
As of publication, the humidifier is being mounted in its position in front of the rear right wheel, so it can be directly integrated into the exhaust system of the fuel cell. Considering the amount of technology in the car, and that the body work is designed to be aerodynamically efficient, fitting the 10 liter capacity humidifier will be a tight fit. Our engineers, however, are up to the task and have evolved quite a bit of dexterity reaching into small, cramped spaces over the course the Forze VII’s evolution!
The operation of the humidifier is as follows: dry air is brought in via the air intake, and moist air is routed in from the exhaust flow of the fuel cell. The two air streams are separated by a membrane, through which gaseous water vapor can pass. The two air streams run in opposite directions (counterflow) in order to increase the total amount of air passing through the humidifier and therefore the total amount of air being treated. This type of humidifier is a so-called “gas to gas” device because it does not use liquid to provide the humidity (a “liquid to gas” configuration). This saves weight as the humidifier does not need to be filled with water to work. The fuel cell does produce water in its exhaust, but only some of it is useful for the humidifier. The exhaust consists of water droplets that are suspended in the gaseous out flow, liquid water, and finally gaseous water vapor, which is used in the humidifier. The water droplets and liquid water are collected and removed from the exhaust using a water separator, leaving the water vapor to be used in the humidifier.
The humidifier ensures that the air entering the Fuel cell is of a high enough relative humidity. Regulating the humidity of intake airflow is vital to the efficient operation of a fuel cell because the membranes that help regulate ion flow are very sensitive to fluctuations in humidity. If the intake air is too dry, the membranes could dry out, especially when the fuel cell is being run at high performances, like during a race. Low membrane moisture means it becomes less conductive and therefore less efficient, leading to overheating and a decrease in performance.
Although it is hard to say the exact impact that the upgraded humidifier will have, its a definite improvement to the old one, and will lead to improved fuel cell performance. More testing will yield figures on the extent of the gains made with the new part.
By: Willem van der Vliet