Page 176 - Design of Solar Thermal Power Plants

3.3 THERMAL PERFORMANCE OF PARABOLIC TROUGH COLLECTOR 161

TABLE 3.4 Requirements on Measurement Parameters Within the Steady State Test
Period

Parameter Value Parameter Value
G bp 32 W/m 2 Inlet temperature of 2% of set value
heat-transfer fluid
within the collector

Ambient air 1.5 C Outlet temperature 0.05 C per
temperature of heat-transfer minute
fluid within the
collector
Volume flow of heat- 2% of set Mean ambient wind 2w4 m/s
transfer fluid value speed

and these measurement parameters shall also satisfy the allowable
deviation specified in Table 3.4.
Parabolic trough solar collectors operate while tracking the movement
of the Sun in the axial direction. However, the rotation test platform is
capable of enabling the near-vertical incidence of solar radiation at the
aperture of receiver of parabolic trough collector within the test period,
which means, in order to make sure that the steady state test model is able
to conduct the long-term prediction on the thermal performance of
parabolic trough collectors, IAM shall be completed in another inde-
pendent testing process in order to determine the variation of thermal
efficiencies of parabolic trough collectors under different incidence
angles. For testing the incidence angle correction factor, the inlet tem-
perature of heat-transfer fluid within the parabolic trough collector shall

be within 1 C of the ambient air temperature. In case of not being able to
satisfy such requirement, IAM K sa shall be calculated in accordance
with Eq. (3.35).

h þ F R U L ðT fi T a Þ=G bp
a
K sa ¼ (3.35)
F R ðsaÞ rg n
e
in which h a refers to the intercept efficiency of collector.
The steady state test method has been the most widely recognized
performance test method all over the world for parabolic trough solar
collectors. Many tests have been completed in accordance with this
method (e.g., the test for LS-2 parabolic trough collectors of the first
commercial CSP plant (SEGS) in the world, and the test for LS-2
parabolic trough collectors mounted with PTR70 vacuum evacuated
tubes, the test for parabolic trough collectors applied in the industrial
field and the test for a type of fiberglass-reinforced parabolic trough
collectors).