Can Highway Harvesting be Practical, Profitable?

The tooth fairy can do even better - she gets double the amount this concept can.

Or I guess 0 * 0 = 0 so I would have to say she gets the same amount.

How practical would this concept be and what are the possible pitfalls and/or benefits?

What concept? Is it this?

Speedbumps?

Solar?

How can anyone here erupt in conversation, when some of these blogs don't even offer a clue as to what, specifically, they're referring to?

I don't know....................maybe a link would help.

"... about 44 megawatts of electrical energy per year, enough to power 30,000 homes."

Hmmm. Really? Really? 30,000 homes for about an hour.

44 megawatts, so 44 million watts. That is 440,000 one-hundred watt bulbs for one hour. 24 hours in a day, so 18,333 one-hundred watt bulbs for one day. 365 days in a year, so 50 one-hundred watt bulbs for one year.

Is this being oversold a little bit?

I usually don't reply to religious posts but this one takes the cake.

44 megawatts, 30,000 homes, pitfalls and/or benefits? From what?

Shock, Vibration and noise! I only get the noisy bit.

Where's all this energy coming from? What's the capitalization cost? Is it thermal, piezoelectric, hydraulic? Garbage, I think. If you pull energy from vehicles, they get worse gas mileage. 1=-(-1) as the man said.

Now if you could slow down non-regeneratively braked vehicles on a downgrade, you could save their brakes and make power.

(-1) = i or "Imaginary number".

LOL what a freaking joke....going "Green" going afoul!

That's what this concept is....imaginary!

Thanks Cap'n. Your analysis is valuable in these days of energy stress. Thanks for bringing a balance thoughtful engineering and multiple solutions to the table! It's refreshing. I almost thought you were one of those morons who wanted to promote the current status quo. But I can see you are not. So there is no reason to delete this post. Because it is not a personal attack.

Where to start?

"..Israeli government was able to generate 2,000 watt-hours.." Well at least they got the units right. Over a full year that's an average rate of about 0.23 watt (which seems reasonable). We'd have to know the real cost to see if that's sensible or stupid.

".. half mile of highway into about 44 megawatts.." If 10m give 2kW-hr the 800m would give 160kw-hr about 18W continuous.

The old bunch used to come up with better topics - a lot of topics now seem like either someone is bored or doesn't have any idea what they are looking at.

There really is key data missing even from the linked report. Rereading it I dont think we can assume they generated 2000 W hr in ine year although I think you are right that 0.23W from 10m of road continuously doesnt seem unreasonable but if it was a 3 month test and the figure was 1W continuously again seems right sort of order.

Someone above was suggesting it would take more power from cars. I am thinkng that this isnt the case. Is the idea that moving cars induce vibrations in the road surface and it is these vibrations that are used by piezos to generate power?

This seems a great idea and I also like the point made that you would just install them when the road is being resurfaced - someone in the green world has looked at the practcality of implementation and worked it into the normal operation which is key for uptake. I would imagine that it will only geenrate power for road side lighting etc but that may be worhtwhile depending on th cost of the piezos.

30000 homes from 0.5 mile of highway even if its 8 lanes grindlocked doing 50mph seems unlikely

This is an old thing I saw on a green blog a couple of years back - maybe they are looking for suckers for new money.

Even using piezo electric transducers, to absorb the energy from the passing cars, the road has to be somewhat softer than on a concrete base. This mean that the cars will consume more gas to drive there.

The energy has to come from somewhere.

If you use the asphalt as a large solar heat panel, things are different as the road surface can stay stiff since no movement is needed. Keeping the road cooler could actually reduce gas consumption (harder tires). This would be an interesting concept where it might be a win/win situation. Unfortunately, it doesn't work in the winter when we could really use the heat directly and the summer's temperature is not really high enough to produce quality heat for electrical production or absorbtion chillers.

Shock, Vibration and then Noise from the suspension system. Who is going to pay for repairs of my car?

This is fantasy!!

no

slow down, killers. 44 mega watts of panels (that's how solar arrays are quantified) will indeed fit in a one/half mile median area 100 feet wide. That total annual output would indeed power that many homes. I'm not saying it is any more feasible than a solar array in another place, except it probably has good transmission line connectivity, the real estate is already publicly owned, (so it could be leased) and it is likely to be well manicured.

Not to mention dirty.

and that makes it a non starter, huh? Guess that coal plant is a cleaner option.

If this is for solar panels, I suspect that the issue is that dirt from the traffic will soon coat the panels, reducing their already low efficiency, rather than equating "dirt" with "pollution". Highways will be dirtier than open land, in general.

Pollution will include what is already being generated due to traffic, plus what the additional load imposed upon the cars causes (adjusted for conversion losses) if the system uses piezo or other vibration-powered devices, as implied by the choice of publication carrying the article we can't see. I'd be surprised if the overall efficiency came near matching a well-run coal-fired plant, and the varying availability of power from such a source is yet another drawback, as it is highly unlikely to match the needs of a region. If efficiency is equal, controlling the pollution for a single point source should be easier and cheaper than doing the same for tens of thousands - especially when they're not yours!

Thought-experiment: if vibration can be utilized to produce electricity, why not save the cost of balancing the generators, turbines, etc. in the coal-fired plant, and build the harvesting devices into the mounting bases? Convenient location for sending the power out to the world, and available at the same times as the generator is needed.... Yes, that's sarcasm.

The arrays could act as a roof to prevent snow accumulation. The savings on snow removal (at least up north) could help pay for the array's maintenance cost.

But if they're snow-covered, they're not producing electricity. If they're made with sufficiently steep tilts to have it slide off, that function could be better served by an actual roof optimized for the purpose (though we might need to use artificial lighting in the resulting "tunnel": open sides will not work if wind-driven snow conditions occur).

In any case, the original article was unlikely to involve solar panels, given its publishing venue.

Sure, if the highway consists of speed bumps every five feet or so....

Build it--and they won't come.

The bottom line...

How much does it cost?

We can harness the power of a potato.. but hat does not mean it's efficient?

10 meters gave 2KW.??.. in '09 .. so why aren't there more already?

How Much!? Assemblyman don't care..

The article said 2000 watt-hours. How long did it take--and then what, did it quit? (Another "science" article with incorrect units.)

But, assuming they meant 2000 watts per 10 meters of roadway, then in 0.5 miles (~0.8 km), it would get 160,000 watts = 0.16 megawatts. This is a far cry from 44 MW, so maybe they are relying on some unspecified other mechanism.

At 44 Megawatts from a half a mile of road I have a lot of trouble with the math here.

If it was taken from the vehicles on the road you would need a 6 lane or larger highway with 1000 vehicles donating around 60 HP a piece! As far as I know not too many vehicles have that to spare and none will supply that much added parasitic losses without a substantial loss of fuel mileage.

So rationally the vehicle source concept is out.

Solar at around 120 watts per square yard would only yield about 460 kilowatts at ideal working conditions so thats not likely it either.

Lastly if 30,000 homes use the same average power as me at nearly 1000 KWh a month that works out to a base load of about 1.33 KWH per house per hour which means that a base output of around 41,666 KWH per hour 24 hours a day needs to be maintained.

Nope! Still cant make that math work either.

I think someone else is having trouble with the math!

Here's the math for PV.

2500 feet (approx 1/2 mile) by 100 feet (median width) = ribbon of solar panels (array)

250.000 square feet x 13 watts (ave panel production) =2.750.000 watts or 2.75 mega watts of production x 80 percent (derate for dirt, inverters, wire loss etc) = 2.2 MW.

4.5(average full sun hours where I live) x 2.2 MW = 9.9 MW Hours per day.

This array would produce 9.9 MWH x 365 (days) 3.613 GWHours per year. It would cost about 10-12 million dollars. + land lease costs

If you follow kramarats link above and dig down you find some stuff on the origianl Israeli test

This gives a generation of 400 kWhr on 1km of dual carriageway assuming 600 vehicles pass through the km

There is still not enough data but say this was the peak hourly generation.

If the speed on the dual carriageway was 50km/hr (~30mph), and we just looked at the two lanes going in one direction that would give a vehicle spacing of 166m(550ft). Based on 2 lanes at 50km/h for one hour ie 100 km of inital road length for the 600 vehicles - which isnt that busy to be honest so they arent over egging the loading.

Over the measured km say they took 400kW from 600 vehicles this is 0.66kW per car (0.9 HP per car). So how efficient are these piezos? I can't imagine they can capture more than say 10% of the vibration energy that is transmitted to the road surface by passing traffic so that means that we need 6.6kW per car (9HP per car) to be transmitted to the road. How much of the vehicles power is wasted in road vibration - I have no idea but does 10% seem fair? we are up to 66kW (90HP) per car. Even if the piezos were 50% efficient its 13kW 18HP and thats a fair bit a car power to lose.

So the orignal thought of less than 1kW/HP per car that seemed ok turns out to be not plausible (I think)

So perhaps the 400kWhr was the 24 generation which gets the power loss down to less than 4HP and suddenly we are in a possible operation.

This though gives a generating power of 17 kW/km ie 2650 km (1650 miles) for the 44MW the politician was predicting! Whilst there are many miles of multilane in cities I suspect most of the highways in Ca are dual carriageways.

Overall I think there is something here especially as I mentioned above that as road surfaces are continually replaced and these piezos can go in as part of scheduled maintenance there is a use - but I thin its only likely to be for the road furnitire - signage, street lamps etc but that isnt to be sneered at

<...44 megawatts of electrical energy per year...>

Damn! Missed April 1^st!

Perhaps the better idea is to bury coils and treat it as a linear generator. Slow down the traffic at the same time?