When a Fuel Cell operates it produces electrical power and by-products — Water and Heat.
It prompts the question then — can one drink the water produced by a Fuel Cell?
Think of an IC engine first, such as one in your car. When an IC engine operates it produces mechanical power and by-products — CO2 and Water (which comes out as hot water vapour). This mixture would normally not be poisonous to humans. CO2 dissolves easily in water and is non-poisonous to humans. In fact, water charged with high pressure CO2 is sold as soft drinks eg colas anyway. Yet, visualizing yourself drinking a glass full of IC engine exhaust is a repulsive and a nauseating thought. This is because with inefficiencies in combustion, the by-product is loaded with exhaust gases like NOx, CO, soot, unburnt hydrocarbons, aldehydes ketones, polyaromatics and nitro-olefins. This cocktail of gases is poisonous.
So how much Water is produced by a Fuel Cell?
This is the Fuel Cell equation:
So for every kg of Hydrogen spent, 9 kgs of Water — clear H2O — is produced, that is 9 litres.
Example — Toyota Mirai on a 100km road trip
Now consider a real-life example to see whether a useful quantity of water is produced when a Fuel Cell is operated.
With the push towards Net-Zero an increasing number of auto manufacturers have announced Hydrogen-based Fuel Cell cars (or FCEVs). Pioneers amongst them is Toyota with its hallmark Toyota Mirai.
Recently Toyota Mirai set a new world mileage record in France, traveling 1,003 kms on a single tank (5.6 kg of Hydrogen), with no special driving technique other than common person driving.
Now Toyota’s own website claims a mileage of ~400 miles (650 kms) on a full tank (5.6 kg). Between these two mileage figures, the equivalent quantity of Hydrogen spent per 100 km = 0.55 kg to 0.85 kg of Hydrogen.
This would produce between ~5 to 7½ litres of water for every 100km trip, or 50–75 ml per km, (a cup every 5 kms) and overall a full tank will produce 50 litres of water (5.6kg x 9 ltrs/kg).
How to catch the Fuel Cell Water?
Before one can access this water, it needs to be caught. In this instance, Toyota Mirai solves the problem easily. It catches the water till its on-board water tank is full and any further water produced is let off while driving. On the dashboard is a button “H2O” which when pressed will empty or purge the on-board water tank.
Is the Fuel Cell Water clean enough to drink?
This is the fundamental question. The fuel-cell water is pure as seen in the equation above, so the fuel cell process itself will not pollute the water. If any impurities get into this water it will be due to the storage tank or during its discharge if the tailpipe is not clean, which is possible if it collects dust on the rim as the car travels on dirty roads.
The dirt problem could easily be solved by attaching to the rim a sieve curved backwards to prevent any dirt entering the hole.
There have been many instances now with several YouTubers [Browning, CNN, McLeod] capturing and reacting as they drink water from the tailpipe. There is even a Drinking Water Challenge now running. By all accounts the reports are the water is warm but totally drinkable.
How about Water produced from Hydrogen-batteries at home?
Cars or FCEVs are not the only applications of Fuel Cells. Fuel Cells are now serving as energy sources to complement or supplement or even completely replace home batteries that are usually charged with Solar energy.
When such a home battery is operated, water will be produced. Can a home- owner use this water? Of course, the answer would be “YES” as it is expected to be clean. Around the house there is any number of uses for such water — whether for drinking, gardening, cleaning, etc.
It is also possible that this water can be re-used within the battery unit by strapping an Electrolyzer and using Solar energy to produce Hydrogen by splitting this water. This way one can re-cycle the water and generate Hydrogen in on-going manner with energy difference filled in by Solar!
Fuel Cell — let’s drink to it! Cheers x 3!