Spread Sheet showing how to calculate eficiency.
It is not based on any actual data.
It shows calculations for two solar cookers of areas of 2.5 Sq Mts and 10 Sq Mts.
Physical constants







Specific Heat of water

 1
 Calories/gm




Specific Heat of Aluminium

 0.21
 Calories/gm




Solar Constant

 1.94
 cal per min per sq cm




Latent heat of Vaporisation of water

 540
 Calories/gm











Constants Assumed







Ambient Temperature

 20
 20
 20
 Centigrade


Area of Reflector Sq Meters

 2.5
 2.5
 10
 Sq. Mts.
















Variables Assumed







Weight of Water

 1000
 10000
 50000
 gms


Weight of Al. Vessel

 250
 2000
 5000
 gms


Time required to evaporate above quantity of water

 45
 480
 540
 minutes









Input Given







Energy received from Sun in time required to evaporate
 Area * Solar Constant* Time
 2182500
 23280000
 104760000
 Calories









Or in Kilo Calories

 2182.5
 23280
 104760
 K Cal
















Output Obtained







Calories required to:







Raise Water to Boiling point
 'Weight of Water * Specific heat * Temp Difference
 80000
 800000
 4000000
 Calories
















For Evaporation
 Weight of Water * Latent Heat of Evaporation
 540000
 5400000
 27000000
 Calories
 Notice that Latent Heat of Evaporation is about 7 times the Heat required to reach the boiling point








Sub Total ( Water)

 620000
 6200000
 31000000
 Calories









Raise Aluminium to 100 C
 Weight of Aluminium * Specific Heat of Aluminium * Temp Difference
 4200
 33600
 84000
 Calories
 This is usually an insignificant amount








Sub Total ( Al)

 4200
 33600
 84000
 Calories









Grand Total (Water + Al)

 624200
 6233600
 31084000
 Calories


Or in Kilo Calories

 624.2
 6233.6
 31084
 K Cal









Efficiency (GT( Water+Al) / Input %

 28.60%
 26.78%
 29.67%
 Percent






































Efficiency (GT( Water+Al) / Input %
