A reader of this blog, Burt B. has sent in some concerns that water vapor from hydrogen cars may contribute to greenhouse gases.
Burt B: “I saw the BMW Hydrogen 7 advertised on CNN this morning. It looks like the technology is maturing. I have questions about the water emissions. The water that is made by hydrogen fuel combustion, and I guess fuel cells, probably shares characteristics of distilled water. I understand that distilled water is more corrosive than natural water. Might it become a waste disposal problem?
How will the water be handled? There are three methods that I can think of: misting it into the air, allowing condensed water to drip onto the road and storing it in onboard tanks for draining at a convenient time and place, probably when fueling … can you please explain what happens to the water created by using hydrogen fuel?”
Hydro Kevin: “Thanks for your questions about hydrogen. I’ve talked about water vapor from hydrogen fuel cells and greenhouse gases before. But, I also want to add some new information as well.
For instance, many people make the assumption that hydrogen internal combustion engine and fuel cell cars give off water vapor from the tailpipe but gasoline-powered cars don’t and this is not accurate.
Here is a quote from the MadSci network about the chemical makeup of gasoline, ‘Although gasoline contains many different chemical compounds, it is made up mostly of hydrocarbons, and all hydrocarbons form the same products when they are burned (just in different amounts). When a hydrocarbon is burned (that is, reacted with oxygen), it forms carbon dioxide (CO2) and water (H2O). For our average gasoline of C8H18, the reaction is 2 molecules of octane reacting with 25 molecules of oxygen (O2) to form 18 molecules of water and 16 molecules of carbon dioxide.’
So, the point is that gasoline-powered vehicles are already putting out tailpipe emissions that contain a noticeable amount of water vapor into the air. It’s the carbon dioxide, carbon monoxide and nitrous oxide emissions that we need to stay focused on cleaning up above and beyond the water vapor, which is the natural ingredient in clouds.
As to distilled water being more corrosive that natural water, here is a quote about distilled water from the Wise Geek website, ‘Natural water usually contains a number of microscopic contaminants, along with dissolved minerals such as calcium and iron. One way to remove these elements from water is to boil it until it changes to steam, a process known as distillation. When this steam is allowed to cool down and condense into liquid form again, the result is a purified form called distilled water. Distilled water should ideally be nothing but hydrogen and oxygen molecules, with a PH level of 7 and no additional gases, minerals or contaminants.’
Storing the water onboard a hydrogen vehicle rather than letting it drip from the tailpipe is another solution some manufacturers are working on. Of course, this water will need to be kept warm for cold weather climates. This water may also be recycled via electrolysis and run through the fuel cell again. These are just some solutions to the question of what happens to the water in hydrogen cars.”