A critical component for any solar power project is solar radiation monitoring and measurement. Although this equipment presents a negligible fraction of total project cost (less than 0.1% of total project cost), it is the component most overlooked and over shadowed over other more capital intensive components. However, in this more mature phase of the Indian solar power industry, we are starting to see a shift in market needs when it comes to solar radiation measurements. What’s driving the shift? The focus on plant performance where the premise of performance depends on the amount of solar radiation incident on panels and how well the plant is able to convert and harness that radiation into energy.
This sounds simple, but unfortunately conversations around performance tend to focus on the best way of evaluating it. The bottom line is this: plant performance must be bench marked against the incoming irradiation. If there is an error in measurement of incoming radiation, calculations and estimates of losses are meaningless.
PV Module Performance varies from Standard Test Conditions:
Extrapolation of performance ratios based on Standard Test Conditions specified for PV panels is prone to error. As Standard Test Conditions (1000 W/m² of solar radiation, 25 °C, Air Mass 1.5 and no wind) vary widely from real world field conditions, additional measurements using Pyranometer and/or reference cells are required to monitor PV performance.
Monitoring solar radiation under field conditions is not only is critical for evaluating performance, but also gives important inputs for maintenance and operational decisions. For example, Pyranometer mounted at the tilt angle of the panel array can be used to calculate the array’s efficiency. While a gradual decline of efficiency may indicate a need for cleaning panels, a sudden drop of efficiency could signal failing panels.
Installation, Maintenance and Calibration are Important:
It is not sufficient to procure good quality instrumentation. Installation becomes key. We encounter situations in the field where an incorrectly mounted Pyranometer, poor cabling, or poor site selection, shading with change of seasons, leads to nonsensical values of performance ratios as the input radiation parameters for calculation of performance is incorrect. Seemingly minor things purling mounting for a Pyranometer should preferably be powder coated in light color, as darker colors like red absorb the heat which radiates and can affect the output of the radiometer.
Routine maintenance such as cleaning dust from the dome of a Pyranometer, and changing desiccant where applicable also becomes critical. Furthermore, all radiation measurement equipment requires calibration after certain years of use in the field.
We routinely get requests for assessing currently installed solar radiation monitoring equipment and our recommendations have a large bearing on the accuracy of measurements and consequently, on the evaluating performance of a plant.
Article Source: https://www.bharatbhasha.com
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Article Added on Tuesday, July 8, 2014
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