Saturated Water

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HintLightbulb.png Hint: For exciting work in this direction, take a look at the only company that we know of in the space of off-grid energy - Terrajoule


  • This page explores the concept of Saturated Water, as well as its various applications towards OSE's goals
  • It is liquid water at above its boiling point by being compressed under low pressure, providing heat storage that appears to be superior to any known thermal or electrochemical energy storage method, outside of chemical storage (fuels like Gasoline or Hydrogen)


To 2 significant figures:

  • Definition of Saturated Water - "saturated liquid, noun in Thermodynamics -a liquid whose temperature and pressure are such that any decrease in pressure without change in temperature causes it to boil.
  • Water boiling temperature depends on pressure.
  • If you increase pressure, water will boil above 212F.
  • Calculator - give it pressure - and it tells you what temperature water boils at and its energy content at that temperature - [1]
  • 18 bar water is at 209C and 900kJ/kg, at 1 bar it is 100C and 420kJ/kg. At 18 bar, density is 860 kg/m3
  • The difference beween the two is 460 kJ/kg that can be released as steam energy. This appears to be the stored energy that can be extracted by a steam engine
  • Thus, a 10,000 gallon (38 cubic meter) tank at 18 bar contains 38*860 kg or 33,000 kg
  • Energy releasable from this is 33,000*480kJ = 16 GJ.
  • 1 GJ = 280 kWhr
  • Thus 4400 kWhr. This paper [2]
shows 20-30 kWhr/m3 (about 1000 kWhr for 38 cubic meters) storage capacity which considers the pressure drop or about 1/4 of the theoretical value. Examine if this pressure drop applies to high pressure turbine calculations or to low pressure systems like a 1/4 HP Steam Engine.
  • Extracted at 15% efficiency via a steam engine, that is 590 kWhr. But 1/4 the value for effective extraction due to pressure loss through discharge - and have 150 kWhr. Examine this for a system under OSE conditions of 1000 gallon tank + 1/4 HP steam engine.
  • Acceptable.
  • This means that a 1000 gallon propane tank gets you about 15 kWhr of storage when extracted with a steam engine. At $2500 tank cost - this is $170/kwHr. 2x cheaper than Lithium Ion batteries, and about same as lead acid batteries. But longer life for propane tank.
  • This may be revolution and end of battery storage on a path to ecological means of storage via solar-heated saturated water, wherever available.
  • DiY weld of 5x10 steel yields more favorable results. At $5/sf or $250/sheet - that comes to 35 cubic feet of storage - or about 250 gallons. So $1/gallon volume costs. $1000 per 1000 gallon tank, which is 1/2 or less the cost of industry standards for energy storage. Once we consider lifetime design of properly sealed metal - cost is 10x less compared to battery storage.


  • "The volume specific thermal energy density depends strongly on the variation of the saturation temperature resulting from the pressure drop during discharge, characteristic values are in the range of 20–30 kW h/m3" - [3]
  • Saturated water temperature and pressure tables - [4]

See Also

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