Evaporation

Opposite is a map of the annual pan rates of evaporation in (inches) across the United States, which as can be seen from the map of the world's deserts lies within approximately the same latitudes as the major deserts of the world.

In a desert region like Tuscon, Arizona, which lies within the Sonoran Desert, the average annual evaporation is roughly 100 inches or 2.5 m, which is the amount of annually evaporation that is used in this invention for comparative purposes for all deserts.

Evaporation is the changing of water from a liquid state to a gas. It is usually used to indicate a state change below the boiling point of water. The evaporation rate can be measured by noting the change in the depth of water in a glass, a pail, a puddle or a swimming pool over a given time period (usually a day). Placing a ruler in any of these gives a scale one can use to read the drop in the surface elevation in a day or more.

The 8 largest hot deserts encompass an area of 15,559,000 km2. If 2.5 m of water evaporated from each of these deserts this would make 15,559,000 km2 X .0025 km or 38897.5 km3 of water that would evaporate annually.

Latent heat is the amount of energy in the form of heat released or absorbed by a chemical substance during a change of state (i.e. solid, liquid, or gas), or a phase transition.

38897.5 km3 of water evaporated annually = 38897.5 km3 /(365days X 24 hours X 60 minutes X 60 seconds) or .001233 km3/s

1000c.c of water = 1 kilogram

.001233 km3 of water  = .001233 X 100,000 cm X 100,000 cm X 100,000 cm or .001233X1015 c.c. or 1.233 E+12 c.c. of water.

1.233 E+12 c.c of water = 1.233 E+12 / 1000 = 1.233E+9 kilograms of water. Therefore 1.233E+9 kg/s could typically be evaporated from the surface of the world’s irrigated hot deserts.

The heat required to evaporate this water would be taken up from the desert and this heat can be calculated using the formula q = hwe g, where q = heat supplied (kJ/s, kW) and hwe = 2270 (kJ/kg) is the evaporation heat of water and g = amount of water evaporated.

Therefore the amount of energy that would be taken up evaporating water from the irrigated hot deserts (q) = (2270 kJ/kg) (1.233 E+9 kg/s) = 2.7989 E+12 kW

1 terra watt = 1 E+9 kw therefore roughly 2.7989 E+3 terra watts of energy would be taken up evaporating water from the 10 largest irrigated hot deserts of the world.

The purpose of an embodiment of the current invention is to increase the surface area of the Earth subject to significant evaporation, which in turn would contribute to cooling a warming planet. As explained above the average annual evaporation in deserts is roughly 2.5 m of water. Approximately this amount of the water pumped into the desert for irrigation purposes would therefore evaporate and would produce an added cooling influence on a warming planet. As stated above deserts typically receive an average annual precipitation of less than .25 m therefore the cooling influence due to desert evaporation as a consequence of the implementation of an embodiment of this invention would be at least 10 times greater than the status quo.