measurement and comparison of solar radiation estimation models ...

CHAPTER 3
EXPERIMENTAL SOLAR RADIATION DATA AND
3.1. Experimental Data
STATISTICAL METHODS
The experimental set-up is located at the Mechanical Engineering Department in
Izmir Institute of Technology. Its latitude and longitude are 38°42’N, 27°12’E,
respectively.
Pyranometers are used for measuring global radiation data. Through these
instruments most of the available data on solar radiation are obtained. A pyranometer
produces voltages from the thermopile detectors that are a function of the incident
radiation. It is necessary to use a potentiometer to detect and record this output.
Radiation data usually must be integrated over some period of time, such as an hour or a
day.
Two additional kinds of measurements are made with pyranometers;
measurements of diffuse radiation on horizontal surfaces and measurements of solar
radiation on inclined surfaces.
In this study, the global radiation on a horizontal surface was measured at an
interval of 10 minute by using a Kipp-Zonen pyranometer (Model CM11) during the
experiments. The CM11 (Figure 2) pyranometer is intended for high accuracy global
solar radiation measurement research on a plane/level surface.
The CM11 houses a second built-in complimentary sensing element
(temperature compensation element), in addition to the black receiving detector.
Calibrated to identical sensitivity as the receiving detector, the compensation element is
connected in anti-series to the receiving detector. Instrument output signal is measured
across the entire anti-series circuit. Any change in body temperature, due to thermal
shock or temperature gradient effect, is quickly detected by the built-in compensation
element, and an offset correction signal is applied to the instrument output signal.
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