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Snooth User: John Andrews

Is this for real?

Posted by John Andrews, Jun 25, 2008.

Man-made waterfalls for Manhattan ... artistically impressive but practically confusing? Isn't this going to piss off locals now that they are going to get a constant water spray?


Reply by Philip James, Jun 25, 2008.

Yup! Its an art exhibit basically. Just in place for a few weeks (kind of like the weird orange Gates that were in Central Park for a while). RBoulanger and I will do a cycle around to see them in a few weeks - I'll post some pics so you can see if they are as grand when they are actually running.

Reply by Mark Angelillo, Jun 25, 2008.

I'm pretty excited for this.

Reply by Rodolphe Boulanger, Jun 25, 2008.

On Sunday I went to Governor's island (the new National Park in the center of NY harbor) and it took a while for me to figure out what the huge metal frame tower that will serve as the waterfall was. They have some pretty massive pumps and put floating rubber pontoons (like they use to contain an oil slick) around the whole area so that they don't suck some poor kayaker into the system!

I think they throw the switch tomorrow.

I am waiting for Philip's once in a lifetime Manhattan-henge with waterfall photo!

Reply by Chris Carpita, Jun 26, 2008.

I thought it would be fun to calculate the carbon footprint of this waterfall project using available figures from the WSJ site, as well as some conservative assumptions regarding pump efficiencies.

The considered energy used by the waterfalls is the gravitational potential energy (GPE) of moving 8000 gallons of water per minute (per waterfall). There are no other energy concerns. The GPE is one of those universal physical constants that cannot be avoided, so at LEAST this much energy is used in the project, and I use conservative estimates whenever possible.

The results may surprise you :)


Assumption: "runs daily" = 12 hours/day
Assumption: pump efficiency = 70% (high estimate)

CO2 emmission factory for electricity: 0.527 kg / kWh

dGPE = mass*g*height

heights = 110 + 110 + 120 + 90 (feet)
total = 430ft. avg height = 107.5 ft = 32.76600 m

Low estimate of 8000 gal/min = 30.2832943 m**3/min

g = 9.80665 m/s**2
height = 32.766 m

density = 1000kg/m**3

mass = den * vol = 1000kg/m**3 * 30.2832943 m**3 = 30238.29 kg

dGPE/min = 30238.29 kg * 9.80665m/s**2 * 32.766m
= 9716309.2783094309 Joules/minute
= 161938.48797182384 Watts
= 161.9385 kW (per waterfall)

Project runs from June 26 to October 13
13+30+31+31+5 = 110 days total = 1320 hours

Total kWh = 168.9385 * 1320 * 4 waterfalls = 855,035,216.5 kWh
Actual kWH = Total / 0.70 efficiency = 1,221,478,880.7 kWh

Total carbon produced = 1.221 billion kWh * 0.527kg/kWh
= 643,719,370.12982595 kg CO2
= 644,719 metric tonnes of CO2

In other units:

= 1,419,401,211 = 1.4 billion pounds of CO2
= 709,700 (English) short tons of CO2

I like the billion-pounds figure for an American audience. Anyway, this is just a portion of what our non-permanent art exhibit is costing us, in environmental terms. I'll leave the migratory fish study to someone else.

Reply by Rodolphe Boulanger, Jun 26, 2008.

To put that in perspective and test your assumptions, here are some comps from a recent Wired article. I can't believe these things use 8x more energy than the British Virgin Islands.

"We did some digging around to put that number in perspective, and here's what we came up with: A round trip flight between New York and Los Angeles produces 2.4 tons of C02, driving 12,000 miles in a 2006 Ford Explorer, 7.83 tons. The British Virgin Islands emit 84,000 tons of C02 per year, the European Union 3.1 billion, and the United States 6 billion. A 250-guest wedding, assuming that 125 attendees spend the night at a high-end hotel, will produce 9 tons of C02."

Reply by Mark Angelillo, Jun 26, 2008.

Holy crap! I don't suppose they could be lobbied to install some turbines at the base to help generate some energy?

Reply by Chris Carpita, Jun 26, 2008.

Well, compared to the wedding figure, not all that crazy. I thought 644 kilotonnes wasn't all that huge of a figure, in environmental terms.

My assumptions are correctly challenged. I think maybe 0.527kg/kWh may be off? Do I need to consider capillary action? I would prefer to know what part of my logic/math was actually wrong.

RB: I am having trouble finding an actual source of figures for U.S. Virgin Islands, in terms of both carbon emissions and power usage. I wouldn't throw my math out in favor of a figure from a Wired article.

Reply by Chris Carpita, Jun 26, 2008.

RB: oh sorry, you said British Virgin Islands. There are about 22,000 people living on BVI, the equivalent of a small-to-medium sized town, or perhaps a neighborhood in Brooklyn, and they are not using fossil fuels to lift (waterfalls combined) 120 tonnes of water 33 meters with every passing minute.

I believe they have a much lower carbon footprint per capita as well, and this is largely due to their prolific use of hydroelectric and nuclear energy

So, 8 times the carbon footprint of the British Virgin Islands? Yes we can, NYC!

Reply by Chris Carpita, Jun 26, 2008.

Ok, I actually have a hard figure for the daily runtime: 7:00am - 10:00pm, for a total of 15 hours per day, 25% longer than I anticipated. And, for the updated figures, (until someone finds my logical gaffe):

1.53 billion kWh
806,000 tonnes of CO2 = 1.75 billion pounds of CO2.

Reply by hipergas, Jun 26, 2008.

ccarpita: you rock.
Geeks of the wold: Unite!

Reply by Philip James, Jul 3, 2008.

OK, the 'falls are in place now - RBoulanger and I will make a tour of them soon. Anyone else in NYC going to see them?

Reply by Philip James, Jul 3, 2008.

PS> Notice i didnt get involved in the maths above - i realized i was totally outclasses (i'm a big ol geek, but Chris kicked it)

Reply by Chris Carpita, Jul 3, 2008.

I went over the Brooklyn Bridge last week, and the falls are pretty cool, worth checking out for sure.

Reply by Callie Exas, Jul 3, 2008.

I did the twilight ferry ride around the waterfalls (did your carbon footprint math include the ferry tours Chris??) the falls were cool...I expected the lights to be on and they weren't. I don't know if these waterfalls are completely worth the cool $15 million it took to build though. I really enjoyed the ferry ride. That was fun.

Reply by Philip James, Jul 3, 2008.

I totally stole this from Dr Vino, but it follows the carbon footprint discussion well

"In the name of reducing his carbon footprint, Prince Charles has retrofitted his 1970 Aston martin convertible to run on ethanol-made from “surplus” English wine."

however, "It takes about 500 liters of wine to distill into a tank of fuel."

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