Meet Ragini  

Name: Ragini Kalapatapu
Research interest: Concentrated Solar Power
Email: rkalapatapu@masdar.ac.ae

Research Summary

CSP generation is site specific and for this reason specific local conditions need to be investigated for the industry to flourish. In most CSP plants, an overestimation of power output takes place because all the power is assumed to fall within the solar disk. The radial energy profile (sunshape) can play a significant role in determining the overall flux distribution in the focal plane of concentrating systems inferring that as the solar profile changes, so does the flux distribution.

The purpose of my research is to develop a model for quantifying the effect of sunshapes based on the circumsolar ratio and measure the profiles at specific sites in the UAE. I intend to use the Solar Aureole Measurement radiometer for this purpose and also describe the potential of a small, low-cost field instrument called the Sunshape Rotating Shadowband Radiometer that can be used in the measurement of sunshapes for hundreds of times in a day automatically and unattended. The goal is to have a low-cost, reliable instrument for routine use in solar resource assessment and atmospheric aerosol investigations. This may lead to a new design guideline and have huge implications for the profitability of various concentrating solar technologies which are designed with an assumption of uniform spatial energy distribution.

Concentrating solar collectors are designed with angular acceptance angles which are relatively close to the angular size of the solar disk 0.266°. The reason behind this lies in a careful maximization of the capture radiation and minimization of the thermal radiation from the receiver. The solar profile in the UAE has never been investigated, but due to the high aerosols concentration characterizing the climate in the UAE, a high CSR (see Fig) can be expected that will lead to a high effect on the overall performances of the concentrating technology as shown in the above literature.

This is the major motivation which drives me towards modeling and measuring the sunshapes. The modeling effort has been an ongoing effort at the LENS in collaboration with DLR and I aim to evaluate the effect of solar profile on the intercept factor of different concentrating technologies.

The LENS lab will also be using the SAM-Solar Aureole Measurement radiometer which would capture the picture of the disk and the circumsolar aureole with two cameras.

Ragini’s Work

Left: Rotating Shadowband photometer by Michalsky et al.

Right: Sunshape Rotating Shadowband Radiometer.

Fig. Solar disk surrounded by aureole.