It’s called a “Traffic Turbine.” It spins due to the wind generated by busses passing near it. The turbine spins a generator.
Some claim the energy is essentially free, since the wind from the bus is wasted energy. I don’t know anything about fluid dynamics, but something tells me that such a device would increase the drag on the bus, thus momentarily reducing its fuel efficiency. In other words, any energy produced by the turbine would really be coming from a momentary increase in fuel burned by the bus to overcome the drag. But perhaps I’m wrong. Thoughts?
There’s a lot more wind from, well, wind than there is from passing traffic, anyway. If this thing does generate energy on net, it’s from the weather, not from buses.
I get what you’re saying - there are similar schemes to generate power from people walking on paving - the difference there is that there is two-way coupling between the people and the paving - in order for the paving to extract energy from your legs, the pavement will probably feel more ‘mushy’ and require additional effort to walk on.
But the bus is barrelling along creating air movements, shedding vortices etc - the little turbine is harvesting that after the bus has passed - how does the effect of extracting energy from that moving air propagate back(forward) to the bus?
I suppose it could be argued that the wind turbines are damping the continual flow of air along the road and creating a doldrum through which the bus has to push harder, but that’s like saying in generating energy from the air moved by the first bus, it steals it from the next bus to come along, which doesn’t seem transactional at all.
I might be wrong about this, but I think the generator is just harvesting energy that would otherwise dump itself as frictional heat as the air hits other pieces of roadside furniture.
I thought of something like this when I was a teenager waiting for a bus and feeling the wind of passing cars as they whizzed by. I considered how easy it might be to harness that wind and convert it to electricity. But at the time I figured it wouldn’t work because the wind isn’t that strong, it’s not sustained (I assumed gusts aren’t that useful, you want steady wind) and the cost to lay out and maintain little windmills connected to a grid aren’t near what you get out of it. Also, if it was that easy someone would already be doing it.
I find it amusing that decades later someone actually is doing it, though I guess not the way I’d considered (rows of windmills stretching along the sides of the road).
You are correct. There may be some theoretical loss for vehicles being able to ‘draft’ behind others for a slight improvement in fuel economy, but most of that turbulence is just wasted as heat and acoustic energy. I doubt there is really enough energy being captured to make it a significant source of energy to be worth supplying to the grid, but I assume they are using it to power signals or other devices similar to the way pole-top solar panels are sometimes used for off-grid instrumentation.
OP’s video shows the turbine set up between two opposing lanes of traffic. The pressure wave from one bus would otherwise interfere with the oncoming bus, so breaking up the airflow between the two lanes and scavenging the excess energy makes sense.
You can probably accomplish the same thing more efficiently using just a solid divider, however.
“Free energy” usually means “perpetual motion machine plus it actually outputs extra power”, not something similar to sneaking an extension cord through the side yard to your neighbor’s receptical.
But this little turbine could be an example of an energy harvesting device that was useful. For example, it could be placed in a vehicle tunnel that lacked wiring, and generate a little power to provide for some sort of a warning light, say. There are little water turbines built into some bathroom appliances to generate a bit of power for the flushing mechanism or some sort of dispenser, which is useful because there isn’t a power line run to a typical plumbing fixture and you wouldn’t want a permanent line cord draped over to it.
I would guess it probably does suck some power from the bus, but so would anything else near the road, like utility poles and signs and whatever was growing there. But on the other hand it might help channel flow to stay near the bus and provide a streamlining effect.
I would say it’s just a rebranding since “perpetual motion” gained such a bad reputation. Perpetual motion pretty much always implied extra energy as a side effect. If the devices worked the way they were described (overbalance wheel, etc.), there would be an excess of power that could be harvested. Plus there’s not much point to the machine unless you get excess energy.
“Overunity devices” is another such rebranding. All the names refer to the exact same set of useless machines.
Seems like once you’ve spent the energy & materials to build this wind generator, it would be more effective to place it somewhere where there is a pretty steady flow of wind. A roadside location is only effective when there is traffic, including large trucks, and the traffic is moving at speed (not during rush-hour gridlock). Should be a lot of places where wind is more consistent than that – even just mounted on the roof of a 2-story house.
“Seems like once you’ve spent the energy & materials to build this wind generator, it would be more effective to place it somewhere where there is a pretty steady flow of wind. A roadside location is only effective when there is traffic, including large trucks, and the traffic is moving at speed (not during rush-hour gridlock). Should be a lot of places where wind is more consistent than that – even just mounted on the roof of a 2-story house.”
Exactly. Has somebody done a cost analysis of this?
The term you are looking for is energy harvesting.
I spent some time working on technology for wireless sensors (about ten years ago). There is great interest in being able to place such devices in their operating locations without any wiring whatsoever (including power wires) and without batteries needing frequent replacement. The strawman we were working towards was wireless strain gages for structural health monitoring of bridges. In this case the cost of wiring (and maintaining the wiring) of thousands of strain gages over a large structure such as a bridge dwarfed the actual cost of the sensors themselves.
Key to this (and pretty much any similar application) is energy harvesting - generating enough energy to run the sensor node from the environment. (This is a much better term to use than “free energy”, BTW.) In the case of bridge health monitoring we were harvesting energy from the naturally occurring vibrations in the bridge structure due to vehicle traffic, wind, etc.
The basic idea is that storing the tiny amounts of energy available over a long period of time would allow for periodic but infrequent sensor excitation, readout, and data transmission. Certainly not real-time vibration data, but frequent enough to catch deformation of a structural element before it becomes a problem.
There are other examples. One I can remember is a wireless light switch driven by a piezoelectric crystal. When the light switch is pushed, it stresses the piezoelectric crystal which generates enough electrical energy to power up an RF transmitter and send a message to toggle the light on or off. Another was a research team who was developing sensors for monitoring trees which were powered by a pair of electrodes, one stuck into the tree at its roots and one higher up on the trunk. They claimed there was enough potential difference to be able to harvest energy needed to power the sensor node - I guess a living potato battery?
There is a horse power loss figure that can be calculated from pushing air around a vehicle. They do it all the time in wind tunnel testing. It is wasted energy.
I also feel that energy when vehicles blast by me.
So you could capture some of that energy with a device. But you need to do a cost benefit analysis. Hopefully the folks who designed these things did an accurate one and it comes out positive.
It might be more effective to station these things at the end of tunnels or other places where vehicle traffic movement would concentrate the air movement. But not in a position as to impede the air movement directly back onto the vehicles.
I imagine the objective here is to provide a small power source to some piece of signalling or monitoring equipment that would be difficult to access regularly to change/charge batteries, and for one reason or another, is not amenable to permanent wiring in.
The potato isn’t the energy source in a potato battery-- The metal bits you poke into it are. Over time, the less electronegative one (typically zinc, with the other one copper) will become corroded, and it’s that corrosion that provides the energy. You probably could get the same effect in a tree, but you’d be much better off sticking those electrodes into a conventional battery.
It’s possible that trees themselves inherently have potential differences that can be harvested, but if so, it’s unrelated to potato batteries.
Although I suppose a tree could also support a good sized sacrificial electrode system that provides power for more years than the milliwatt / microwatt sensor is expected to survive or be technologically relevant.
Slight clarification on this:
Perpetual motion machines are typically classified as one of 3 types depending on which of the laws of thermodynamics they break (sort of): wikipedia.
So it’s not a fight over one definition; it’s a definition that encompasses several flavors.
