Both excellent questions.
1. We suspect the main reason piezoelectric technology is not yet widely used is because the technology is comparatively much more obscure than traditional power generation techniques. As such, not many have attempted to implement this technology in a form practical for this application. However, there have in fact been schools and other facilities that have already started using this technology to aid in power generation, such as the Simon Langton Grammar School in Cantebury, England. (http://news.nationalgeographic.com/news/energy/...)
The main challenge to implementing this technology on a larger scale is the cost. Our concept utilizes two sheets of copper, one sheet of glass, and one layer of a chemical called barium titanate. Glass is costly to produce in large sheets, and barium titanate is costly to purchase in large quantities. Because of that, the cost of covering an entire facility in these transducers would likely be an impractical cost for some.
However, many different variations of the piezoelectric transducer exist, some with lower costs than others. We’re sure if an effort is made, an alternative design utilizing the same principle that is more cost efficient and could be mass produced more easily would be found.
2. We found through various sources that using our form of the technology, a 60KG person, assuming every footstep could be captured, could generate 9 W on transducers consistently. We assumed a student would walk around and move on the floor of their school for approximately 2 hours per day (as time spent sitting in a seat cannot be used to generate energy), so a student would generate 9 W-hr per hour for 2 hours per day, or 18 W-hr per day total. Assuming an average school body of 2000 students, the total generated by a student body over a single day would be 36 kW-hr per day.
The main issue with this calculation is that it assumes every single footstep by every student will be captured, including the ones taken outside of the school building. A more realistic number would be lower, though we expect not by much.

Both are very plausible ideas.
1. We in fact did do research on this possibility. However, for us, it became an issue of how useful it was rather than how much money it could save. Embedding piezoelectric transducers into shoes would also require a battery placed inside the shoe itself, and a standard nickle or lithium battery that size would not be able to store much power. Beyond a certain point, all power generated through the footsteps would be wasted. In addition, it’s likely that power generated from piezoelectric sensors in shoes would only power phones, tablets, and other small mobile devices, which draw a minimal amount of electricity in the first place. By placing transducers into floor tiles instead, despite the higher initial cost, more energy could be generated and overall the positive impact on the environment could be greater.

2. A standard induction generator requires rotational motion of a rotor, which we do not know how we would implement. In addition, the parts required would likely add up to a larger cost than the parts of a standard piezoelectric transducer. Because of this, we believe that even though power generation through electromagnetic induction may result in more power, ultimately, utilizing the piezoelectric effect is a much more practical and cost efficient method.

Of course, such an approach could be very possible, given the right circumstances. We aren’t disregarding the idea entirely.

Implementing piezoelectric transducers into stairways is definitely a good way to demonstrate our approach to creating energy. We aim to place the transducers in areas of high foot traffic and busy subway stations are an example. As we further develop the idea, we can create empowering visuals and service announcements that encourage the audience to take part in reducing carbon emissions. Our idea solely depends on the participation of the people, so it is important that they understand the impact that could result from their simple actions.

Ms. Luff, thanks for your comment! We agree, installing the transducers in any major city would definitely be a great idea. There is so much energy we could gather with the great deal of foot traffic that cities experience. We wanted to begin closer to home, which is why we suggested implementing the transducers in D.C. first, but this idea could certainly be applied in any other city. Though there will inevitably be an initial cost and energy needed to install the transducers, the energy we could generate with the many footsteps taken in the cities would vastly reduce the amount of fossil fuels we need to use in the future. Within a short amount of time, that energy would make up for the fossil fuels we used to execute this and after that point, this would be a source of clean energy. And in the long-run, this could be used to counteract our effect on climate change.

Excellent question. The cost is in fact prohibitive for a large amount of schools. Indeed, if implemented properly, the school would need to have its existing tile and carpet removed before the transducers could be placed. However, the ultimate goal of this idea is to utilize them in much more heavily traversed areas such as crowded city subway stations or possibly even roads or highways. Installing them in schools would help, but would mainly show the potential for much greater impact once installed in the other areas mentioned. Because of that, we don’t see it as critical that every school has these installed; even if just a few relatively well funded schools have these installed, if it’s demonstrated to be effective, we’d consider it a success.

If a few schools implemented this technology it has the potential to create a ripple effect throughout schools across the country. I could really see this design being recognized by influential critics to increase its popularity.
This would work well in crowded areas indeed. However it may be tricky to shut down busy areas to install this. How long does it take to install?

You are right that piezo-electricity is very popular in this competition. I knew almost nothing about piezo-electricity before. It was interesting to learn about it and see all the ways it could potentially be used!