For our midterm assignment, we were asked to extend and play with the phenomenological science fair projects brought in at the start of the semester; I had originally toyed with extending lemon batteries to use other substances such as pee and ice melting salt (calcium chloride).
Two ideas were in the running:
Ultimately I was intrigued by developing a sustainable street lighting system powered by reusable waste. The general vision was to produce something reminiscent of the following:
From my initial tests and research on batteries, there were certain design requirements that had to be met in order to produce a working and viable battery:
So I built some forms and poured some concrete. Found a 20 lb. bag of premixed cement/sand (need to mention that if you like hardware stores, Chinatown Building Supply is an awesome resource), poured in a bucket of water, stirred the mixture and filled the forms. Once full, a smaller block of wood was pressed into the top of the form in order to leave a hollow space for the battery and lighting circuitry.
Two days to set and the pavers were ready to demold.
Individual holes were drilled for each battery cell in addition to a central housing for the circuitry.
Once set in the concrete, the battery turned out to be a bit of a disappointment. A dry circuit revealed an odd standing voltage of 0.56 V. Presumably there was still some moisture in the paver that was wicking into the cotton and providing a small charge.
With a few squirts of lemon juice (i.e. pee), the voltage quickly jumped up to around 3.0 V (2.76 V pictured) and then slowly tapered with time. Subsequent soaking resulted in less and less voltage, making this battery increasingly less viable as, well, a battery.
Future versions will attempt to waterproof the interior of each cell, as it seems that the concrete was too porous to keep the solutions of each cell in isolation. Even a few drops of liquid seemed to establish a bridge across cells. Original tests revealed up to 5 V and a well lit super-bright LED with the same circuit, so there should be a way to get this working more reliably.
To cap the circuitry, a piece of frosted plexiglass outfitted with an embedded drain was fixed atop the paver. It served to both let in a slow drip of liquid and diffuse the light for a more ambient lighting effect.
Future versions will forego acrylic in favor of directly molding the grill into the concrete form or via a more durable metal casing. In its current form however, it’s held up favorably nestled in the tree pit outside my home.
I really think there’s a potential for something like this, whether it be used in this context or in situations where there are waste facilities on location paired with the need for cheap renewable energy.
The following catalog potential sources of urban pee, examples of public urinals in existence across the globe, and an art project by Spanish artists collective Luzinterruptus.com which attempts to draw attention to public urinating with hope to remind people to abstain from this anti social behavior.
And below is the presentation given in class: