Updating Mark Valentine's Steam Battery Research

Electrical engineer Mark Valentine's article "The Steam Battery: A Low-Cost Science Experiment Performed with Ordinary Materials" appeared in The Citizen Scientist two years ago (07 October 2005). Recently Brian Lowis, an upper level physics student at Northern Michigan University, wrote TCS to ask about Mark's experiment. Brian was unable to find any similar research while doing a literature search on the steam battery, and he suggested that the steam battery might be a one-of-a-kind device.

Mark Valentine responded with a newsy report about his steam battery project that appears below following the first two paragraphs of his 2005 article in TCS. Of special interest are the serendipitous circumstances surrounding this project that many amateur scientists will no doubt appreciate.

The Steam Battery: A Low-Cost Science Experiment Performed with Ordinary Materials and an Update

Mark Valentine

Most semiconductor components are vulnerable to static electricity, also referred to as electrostatic discharge (ESD). These components are usually packaged with a piece of black, electrically conductive foam (referred to hereafter as “ESD foam”) placed over their electrical pins or leads as a form of protection from ESD. Because ESD foam has a large internal surface area within a relatively small volume, it is plausible to assume that certain changes in the environment surrounding a sample of ESD foam might cause observable changes in the electrical resistance of the sample.

Initial investigations revealed that a sudden change in humidity from my breath did indeed result in a change in resistance for several ESD foam samples. However, the resistance readings appeared erratic and occasionally read as negative on the digital multimeter (DMM) used for the measurements. I soon found that the ESD foam samples were producing a DC voltage, which led to the formulation of a new hypothesis and experiment to address the means by which humidity could be generating the observed DC voltage in an apparently uniform ESD foam sample. Specifically, the experiment was designed to determine whether the DC voltage in the ESD foam settles into a steady state with the continuous localized application of humid air. It was also designed to determine the relationship between the polarity of the DC voltage across the sample and the relative position of the region on the sample directly exposed to the high-humidity airflow. (Continued here.)

Figure 1. Mark Valentine holds some ESD foam with a surprising property. Photograph by Cyndi Valentine.

Yes, the "Steam Battery" experiment is original. Here's the story, with some human interest added:

I moved back home to Kansas over three years ago to get married and to be close to my father, who was dying from cancer. It was the last wedding my father, an Episcopal priest, performed.

Because of his condition, we invited our friends to a separate reception four months later in July. I invited my friend, Dr. Christopher M. Sorensen of Kansas State University, who was my engineering physics professor. He brought my wife and me a vase for our wedding present. He also gave me something else.

It was his latest sample of carbon aerosol gel, formed by a unique process in which larger molecules are decomposed into carbon that gel into a very light fractal structure. It's truly amazing stuff,
and more information can be obtained here.

With a dark cloud of sadness hovering over our my family, I was glad to have this sample to experiment with. The only thing I could think to do was test its resistance, which I did with my own personal
multimeter I've had since high school.

What I discovered is that the carbon aerosol gel's resistance would drop when I breathed on it, and then would slowly increase back to a few thousand ohms. I soon established that this was due to humidity, not heat (verifying the old saying!).

Because carbon aerosol gel was visually similar to black foam used for ESD protection in ICs and other static sensitive parts, I performed similar tests on samples I had of ESD foam. To my surprise, it behaved the same way.

My father died soon thereafter on August 5th, 2004. While grieving over losing him, I continued with these delightful experiments.

Shortly before I moved back to Kansas, I had the great fortune of finding an interesting job close to where I would be moving. It was a fuel cell company called TVN Systems. They had decent electrical equipment, and I took the foam samples into work to show my colleagues the peculiar sensitivity to humidity. Everyone was interested, but nobody had an explanation.

One day, I was trying out a foam sample, and trying to understand why the resistance fluctuated in the ESD foam, but not the carbon aerosol gel. I was using one of TVN's good meters from Extech. This was the moment of discovery: when I breathed on the sample, the meter was reading a negative resistance. It could mean only one thing: the little foam sample was acting like a battery.

I quickly switched the meter to read voltage. I could not believe what I was seeing. The meter went to 0.8 volt DC! Again, I showed the boss and my colleagues this new phenomenon of voltage generation. It was amazing, but we didn't know why this was happening.

Nearly a year later, I developed these findings into a project article for the The Citizen Scientist, but with one more crucial bit of insight. I discovered that the polarity of the DC voltage depended on the direction of flow of humid air through the sample. Specifically, the side that that my breath entered was the side that was negative.

Since the article was published, I've shown this phenomenon to several people, including an engineer from Honeywell (along with the carbon aerosol gel sample) for possible use as humidity sensors. However, it really does not seem to have attracted too much attention.

I've also dreamed up some energy harvesting configurations. For example, several foam samples could be wired together in parallel and series. They could be then be placed in appropriately sized holes
in a transparent dome whose lower edge is immersed in water. Solar radiation would create a 100% relative humidity in the dome, which would then flow through the samples and into the surrounding air, and possibly generate an ever so tiny bit of electricity. At most you might be able to power a calculator, or, using a pulsed power circuit, other types of loads (see www.aldinc.com; they make a unique energy harvester device).

As to what might be happening, I think it is this: humidity enters the sample, condenses at the point of entry, and transfers heat to the conductive fibers. This heat might be raising the energy levels of the
electrons at those condensation sites. Since these energy states are higher than those on the other side of the sample, a voltage is produced.

Of course, since the foam is conductive, there must be an internal current flow. Also, the moisture that condenses on the one side of the sample must also be flowing in the same direction, and then it should be evaporating at the other end of the sample into relatively dryer air. That's what I think at present, anyway.

Figure 2. Prototype steam battery constructed by the author. Photograph by Mark Valentine.

So again, as far as I know, this phenomenon has not been documented or observed previously. While it's hard to be sure, because the world is so large, and human technological history so long, there is another point to consider.

Because my father, who played an indirect role in this project, was an Episcopal priest, he might have compared the ESD foam to the story about how the stone rejected by others became the chief cornerstone. In a similar way ESD foam is not really seen for the truly remarkable component it actually is, perhaps because it is often thrown away once the IC it is attached to is removed from its package.

It's a mystery, like my favorite physics mystery, sonoluminescence. I can't explain either, but I've seen them both with my own eyes. One thing is for certain: Experimentalists can have more fun than
theoreticians!