Saving Energy – One Ice Cube at a Time
Walk in any restaurant and ask for a glass of water. Chances are you will get a glass of ice with gaps filled in with water. Most of the time you will drink a sip or two. When you are done, the waitress picks up the glass and empties it in sink.
There goes almost 200g of ice.
Assume about 0.5 cal/g latent heat of ice, 1 cal/g latent heat of water and 80 cal/g latent heat of melting.
It means that ice represents almost 20 KCal energy pumped out of water.
To do that much work, some freezer somewhere consumed almost 6.67 KCal energy, assuming a a pump with COP = 3. (Look wikipedia for COP or Coefficient of performance for further explanation.)
This much energy at destination means almost 7.5 KCal energy at electricity production site (assuming 10% transmission losses). At 4.18 J / Cal this comes to almost 32 KJ.
This is consumption by per person per day. So 32 KJ/24 hours = 1.33 KWH per person.
For 300 Million Americans, this amounts to 400 Million KWH energy.
That comes to Whooping 400,000 MW energy, or 400 GigaWatts energy going straight in drain per day.
And at what cost?
At approximately 0.1$ per KWH, that amounts to national saving of $40 Milliong per day, that is 14.6 billion $ per year. That means shutting down one coal fired power plant in every state.
Also in environmental terms, that amounts to almost reduction of 58 million tonnes of emissions per hour.
That means little more cleaner skies, greener fields and sane weather.
While writing this article, I also came across a good similar article,