Home -> Blog -> Pavegen and futuristic cities
I recently heard about a company called Pavegen that makes pavement tiles that generate electricity when people walk across them. The company vision is that they will reduce the cost of these tiles and install them all over the place. Futuristic cities will Pavegen tiles all over the place and we will rake in free energy. Pretty cool, right?
The concept of collecting power “for free” from people walking is pretty cool, but I did some research on it/thought about it more carefully and now I’m much more terrified of a futuristic Pavegen-based city than I am excited by the prospect of a new way to collect energy. Most of my information about Pavegen comes from their keynote speech from 7 months ago, hosted on [Vimeo] 1. (I recommend youtube-dl + vlc playback at 2x speed; they talk really slowly).
Basically the way Pavegen tiles work is when you step on a tile it is slightly depressed under your weight, and the downward movement/force is used to spin up a flywheel (a very small amount). Separately, power is extracted from the flywheel at a controlled rate, trying to keep the flywheel moving at some optimal target speed.
In the keynote presentation they had several people walk across the tiles and showed some unitless numbers going up, but they never really said how much power (per person) they are extracting using the tiles. This is an important problem because it is easy for the answer to be “too much” or “too little”. “Too little” is the potential problem that everyone focuses on – if the tiles don’t extract enough power to be useful then there’s no reason for them to exist. No one ever mentions the possibility of “too much”, but at scale it’s a very real possibility. The power collected from the panels has to come from somewhere – in particular it comes from the people walking. Or should I say “climbing”? When you step on a panel it lowers slightly, so when you step on the next you need to lift your body by however much it lowered. If the panels themselves are level then you are walking uphill – that’s where the power they harvest comes from [2]. No one will notice the difference walking over a brief strip of these panels while entering a mall, but if they were installed all over a city I don’t think it would go over so well. Also, while I’m generically in favor of people exercising more, the farming -> food processing -> trucking -> stores -> cooking -> eating -> human energy output -> (high efficiency) Pavegen tiles is not the most sustainable form of “clean” energy production [3]. Pavegen talks about using this “free” energy to power nearby lights, but I get the distinct feeling that if we put this energy back into the food production process we’ll find that the small increase in food requirements of each person walking over the Pavegen tiles means that we actually lose energy on net instead of gaining it. Frankly, I’m not convinced that Pavegen tiles can produce enough energy to be worthwhile, nor am I entirely convinced that there is a sufficiently large amount of energy to be worth while (at a large scale) that would not also be “too much”
[2] No, Dad, back in your day you didn’t walk uphill both ways to get to school. But in the Pavegen cities of the future we really will do that.
[3] We all know there’s no such thing as a free lunch – how can we say that Pavegen tile power is free when it ultimately comes from your lunch?
The keynote presentation mentions a few additional features that Pavegen provides beyond harvesting power. I found several of these features noteworthy, although mainly not in a good way. They advertise “walk to light”, “footfall tracking”, “advertising”, and “digital currency”. Of these features “walk to light” is the only one I can imagine theoretically wanting in my futuristic city – it is conceivable that it would be a good thing if the floor could guide me with a trail of light to where I want to go. The others, well…
Before the keynote speaker mentioned it as an explicit feature I was already concerned about the possibility of “footfall tracking” as a means of identifying individual people and surveilling them as they travel around the city. Sure, Pavegen would have to do some processing to figure out which steps belong to which people, but identifying people by their gait is already a proven technology (and that’s just with a video camera, not a technology like Pavegen that can measure the force applied over time for the duration of each step).
As it happens, I quickly stopped worrying about this possibility when the presenter suggested that Pavegen would (also as a feature) directly connect to users’ smartphones to log their steps and let them claim some form of ownership over the power they generate. Who needs gait tracking when you have this!? The intent of this feature is that store owners will use it to give customers credits for walking around the store based on how much power they have generated, and that customers will select the stores at which they shop in part based on which stores provide this credit. Really? How much value in energy do I give a store by walking around on Pavegen tiles? [Wikipedia] 4 claims that fit adults can sustain 50-150 Watts for an hour of exercise. If we’re extremely generous and assume I spend an hour in the store producing 100W, all of which is captured by Pavegen, at ~10 cents/kWh I’ve given the store 1 cent of power. In other words, not a lot of value in energy. On the flip side, I’ve spent an hour in their store browsing their merchandise, which is worth much more than 1 cent to them. Remind me again how energy plays into this incentive scheme?
At this point I’m already pretty sure that Pavegen’s main form of revenue isn’t energy-related, but to wipe out any remaining doubt about it consider their last “side” feature: targeted advertisements. Assuming they install Pavegen tiles all over a city, they’ll know who you are, where you are, and what stores you’ve been to historically. In other words they know so much about you that they can probably guess when you’re hungry (and haven’t already eaten) and tell you to go to a particular restaurant to get food. Advertisements that carefully targeted will be more expensive than Google’s ads, and Google reads the entirety of their users’ digital correspondence!
So that’s Pavegen. Their tiles save some trivial amount of money by generating electricity and rake in quantities of money by tracking people and selling information on their habits and whereabouts to make extremely targeted advertisements. Is this the kind of futuristic city you want to live in?