Environmental Engineering Reference
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Figure 6.15 Solar fraction as a function of collector surface area for a 15 kW solar cooling system
with constant generator temperatures (Case 1)
The storage tank volume only becomes important for high solar fractions of 80%and
higher. At constant generator temperatures and a collector mass flow of 30 kgm 2 h 1
the solar fraction drops by a maximum of 10 percentage points, if the specific storage
volume is reduced from 50 to 25 l m 2 . For specific storage volumes above 0.06
m 3 m 2 , the solar fraction hardly changes (see Figure 6.15).
As usual, the specific collector yield is highest for low solar fractions, that is for
small collector surface areas. For the location in Madrid, it varies between 230 and
880 kWhm 2 a 1 (see Figure 6.16).
In the following, the influence of storage tank volume, insulation thickness and heat
exchanger size is evaluated for Case 2 conditions, that is improved control with varying
generator temperatures. The solar fraction to the total heat demand is reduced by
Figure 6.16 Collector yield as a function of collector surface area for constant generator temperature
(Case 1). The storage volume is varied from 1 to 5m 3
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