# Even the New York Times withholds the address

Brett Frankenberger rbf at rbfnet.com
Tue Nov 19 14:58:08 UTC 2002

```On Tue, Nov 19, 2002 at 08:37:33AM -0500, Johannes Ullrich wrote:
>
> How about using water power for backup? Store a big tank of water on the
> top floor and use a water turbine to generate power in an emergency...
> Wonder how much water it would take... but for sure this would do well
> in case of fire.

Have you done the math?  Let's say it's a 100 meter high building.  A
kilogram of water 100 meters off the ground has:
1kg * 100m * 9.8m/s^2 = 9800 J of energy.
Let's say we want to be able to run for one day without power.  So
9800J is enough to provide 9800J/(24*3600)s = 0.113W for a day.

So, roughly speaking, you need 10 kilograms of water for every watt.
One milliliter of water weighs one gram.  So that 10 kilograms is
10000ml, or 10000cm^3, or .01m^3.  One cubic meter, then weighs 1000kg,
and, thus, can provide about 100W (for a day).

Now, figure out how many kw you need to run a telecom hotel, and you'll
know just how large your tank needs to be (and how much weight the
building structure is going to have to support).  Even if you assume
100% efficiency, the tank is still going to me, um, rather largish.

-- Brett

```