More specifically, how much energy does it take to boil 25 liters of water in a system to produce steam at 15 PSI?
I know it takes 1 calorie to raise 1 gram of water 1 degree so 25,000 calories to raise 25 liters of water 1 degree.
If I assume 23C ambient temperature I need to raise the water another 77 degrees (Celsius) or 1,925,000 calories.
Searching around I find 1 calorie = 0.003969 BTU
So, you need 7,640 BTU = 2.24 Kilowatt hours of energy.
However, some clever friend of mine said that you need more energy to boil water than you need to get it to boiling (they cited ~80 calories/gram to go from a liquid at 100C to a gas at 100C). Add to that I know raising the pressure raises the boiling point of water but I have no idea how much.
Any ideas? (And no…this is not a homework question…a friend is looking for an alternate power source for a rotary steam engine and is trying to get a sense of how much energy is needed to make it run).