Physics: What does it take to put a waterfall on a skyscraper?
wired.com
wired.com
Q: Estimate how much it would cost to run this for a day (pick a price for electricity in dollars per kilowatt * hr).
Usage: 3.39 million Watts
Cost of electricity in Australia: $0.25 per kWh
Cost per hour: $847.50
Q: If the water fell with no air resistance, how fast would it be traveling when it hit the ground?
Height: 108 metres
Gravity 9.8m^2 m/s
velocity = sqrt(2 * gravity * distance) = sqrt(2 * 9.8 * 108) = 46 m/s
Q: Suppose you want to make this waterfall be human powered. How many humans would need to pump water if each human can maintain a power output of 50 Watts?
Usage: 3.39 million Watts
Human Output: 50 Watts
Humans required: 67,800
Q: Suppose you want to make this thing solar powered and only run while the sun is shinning. How big of a solar panel would you need? Assume the solar panel produces 500 Watts per square meter.
Usage: 3.39 million Watts
Solar Panel output: 500 Watts/square metre
Size required: 6,780 square metres (1.26 NFL football fields, 1/3rd of the MCG in Melbourne)
Also, from the article: ”That's fine, but that's wrong. According to this site, the waterfall has a power requirement of 185 kWatts.”
⇒ your estimates are off by a factor of about 18. It’s (ballpark) $50, 3500, 350 m².
However, that ”this site” talks about ”four 185-kilowatt pumps” (https://www.scottishconstructionnow.com/27846/and-finally-35...) ⇒ assuming all four pumps are fully active all the time, multiply the above by 4.
Finally, from the same page:
”The electricity bill for just one hour of operation is a whopping 800 yuan (£89), he added.
“That’s why we don’t switch on the waterfall every day – only for special festivities in the city,” he said.”