SUMMARY
The sun is the main source of energy that reaches the surface of the earth in the form of electromagnetic radiation called solar radiation and when it reaches the outer surface of the glass hood of the solar distillation, the process of energy transferring as the heat begins. the energy transfer process between parts of solar distillates greatly controls its performance, so the greater amount of energy gained and the less energy lost, leads to higher productivity and efficiency of the solar distillery. in this paper, a mathematical model was constructed to calculate the amount of thermal energy in each part of a monoclinic solar distiller equipped with an additional capacitor during its operation. as a result of this model showed that the temperature, after a series of heat energy exchanges between the glass cover and all the internal parts of the distillate, with the absorbent part at the base of the distillate, exhibited the same behavior, which is increasing in its temperature steadily during the first hours of the day from (32.5-41.7 ) at (08:30 am) in the morning down to its top value (61.4-76.7 ) at (02:30 pm) and decline after this hour in the same bullish pattern. this is due to the greater difference between the amount of energy lost and acquired by the absorbent portion during the same daylight hours, as the amount of energy gained increases and the amount of lost energy decreases, leading to the highest energy gain and the least energy lost by the absorbent part at (02:30 pm), except the outer part of the additional condenser, which followed a similar behavior of air temperature, with its temperature gradually increasing slightly during the first hours of the day from (27 ) at (08:30 am) until it reached its peak (36.2 ) at (01:30 pm), then it decreases after this time slightly. this slight rise and slight decrease are due to the constant state of thermal balance between the two ends of the additional condenser by the heat exchange process between the outer part of the additional condenser and the cooling water.