
472 Principles of Sustainable Energy Systems
© 2008 Taylor & Francis Group, LLC
For equator-facing fat-plate collectors with tilt equal to latitude, the average beam radia-
tion at normal incidence, I
bn
, is related to the average annual clearness index, K, by the
empirical correlation
(8.41)
where I
bn
is in kW/m
2
. For this type of fat-plate collector, Q
CY
is given by the following
empirical relation:
QAF
IIL
CY CR n
bn bn
×
++−+ +−
5 215 6 973 5 412 4 293 1 403 08..)( ..)(..
999
18 596 5 931 15 498 18 845
2
IL
IIL
bn
bn bn
)
(. .)(. .)(
+− −+++−00 164 35 510
14 601 3 570 13 675 15
2
..)
(. .)(. .
−
+− +− −
ILI
I
bn C
bn
5549 1 620 30 564
22