System Evaluation

Only in the middle of March 2008 the system was totally uncovered, the pumps fixed and the pressure reset. From that time on, the monitoring process has been more conclusive in the diagnosis of the performance of the STS.

Because the East-facing collector field is hydraulically unbalanced, it reaches a constant value of temperature at least 60° C higher than the totalizing channel. As an example, Fig. 3 shows this behaviour.

The West-facing collector field is well balanced and shows no sign of abnormal behaviour thus the temperature read in the temperature probe is real and representative of the whole west facing collectors.

In April 2008 the STS presented its highest performance level (52%). Since then and because of the leakages previously referred the performance has been steadily decreasing at a pace of around 6% per month (see Fig.4).

Temperature Profile in a Typical Day

—West Col. Output —Inlet Temperature —East Col. Output —Outlet

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

7/06/2008

Fig. 3. Typical temperature profile for the STS

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Fig. 4. Evolution of the performance.

But the system is operating satisfactorily with the right behaviour regarding the two azimuthal blocks of collectors. Fig 5 shows the time operation of both blocks through time of pump operation in a typical day of this last monitoring period. East sector begins first in the morning, then there is a period in the central part of the day with both sectors operating simultaneously and finally, in the last period of the day, only West sector is in operation.

Fig 5. Pump relays vs Flow