C. Riordan

Bio: C. Riordan is an academic researcher. The author has contributed to research in topics: Solar energy & Irradiance. The author has an hindex of 8, co-authored 13 publications receiving 1218 citations.

Simple Solar Spectral Model for Direct and Diffuse Irradiance on Horizontal and Tilted Planes at the Earth's Surface for Cloudless Atmospheres

Abstract: In a previous work, we described a simple model for calculating direct normal and diffuse horizontal spectral solar irradiance for cloudless sky conditions. In this paper, we present a new simple model (SPCTRAL2) that incorporates improvements to the simple model approach and an algorithm for calculating spectral irradiance on tilted surfaces. The model was developed using comparisons with rigorous radiative transfer codes and limited outdoor measurements. SPCTRAL2 produces terrestrial spectra between 0.3 and 4.0 μm with a resolution of approximately 10 nm. Inputs to the model include the solar zenith angle, the collector tilt angle, atmospheric turbidity, the amount of precipitable water vapor and ozone, surface pressure, and ground albedo. A major goal of this work is to provide researchers with the capability to calculate spectral irradiance for different atmospheric conditions and different solar collector geometries using microcomputers.

Simple solar spectral model for direct and diffuse irradiance on horizontal and tilted planes at the earth's surface for cloudless atmospheres

Abstract: In a previous work, we described a simple model for calculating direct normal and diffuse horizontal spectral solar irradiance for cloudless sky conditions. In this paper, we present a new simple model (SPCTRAL2) that incorporates improvements to the simple model approach and an algorithm for calculating spectral irradiance on tilted surfaces. The model was developed using comparisons with rigorous radiative transfer codes and limited outdoor measurements. SPCTRAL2 produces terrestrial spectra between 0.3 and 4.0 μm with a resolution of approximately 10 nm. Inputs to the model include the solar zenith angle, the collector tilt angle, atmospheric turbidity, the amount of precipitable water vapor and ozone, surface pressure, and ground albedo. A major goal of this work is to provide researchers with the capability to calculate spectral irradiance for different atmospheric conditions and different solar collector geometries using microcomputers.

Spectral solar irradiance data sets for selected terrestrial conditions

Abstract: Direct normal and global spectral solar irradiance data sets are presented for selected terrestrial conditions, along with a brief review of previous data sets. The new data sets presented cover the 0.305 μm to 4.045 μm region and were generated with the rigorous BRITE Monte Carlo radiative transfer code, the revised Neckel and Labs extraterrestrial solar spectrum, the U.S. standard atmosphere model, and a rural aerosol model. The data for the 2.45 μm to 4.045 μm region were taken from existing ASTM standards (E891-82 and E892-82). Tabular and graphical data presentations include irradiance versus wavelength, photon flux density versus wavelength, and photon flux density versus photon energy.

Light trapping properties of pyramidally textured surfaces

Abstract: The light trapping properties of textured optical sheets have become of recent interest in photovoltaic energy conversion since light trapping allows a significant reduction in the thickness of active solar cell material. Previous analyses have concentrated on sheets with randomly textured (Lambertian) surfaces. The texturing of crystalline silicon substrates with anisotropic etches to give surfaces covered by square based pyramids defined by intersecting (111) crystallographic planes is a widely used technique for reflection control in silicon solar cells. This paper analyzes the light trapping properties of substrates with such pyramidally textured surfaces. Important differences are found from the case of Lambertian surfaces with practical consequences for the design of high efficiency silicon solar cells.

Photonic crystals cause active colour change in chameleons

Abstract: Many chameleons, and panther chameleons in particular, have the remarkable ability to exhibit complex and rapid colour changes during social interactions such as male contests or courtship. It is generally interpreted that these changes are due to dispersion/aggregation of pigment-containing organelles within dermal chromatophores. Here, combining microscopy, photometric videography and photonic band-gap modelling, we show that chameleons shift colour through active tuning of a lattice of guanine nanocrystals within a superficial thick layer of dermal iridophores. In addition, we show that a deeper population of iridophores with larger crystals reflects a substantial proportion of sunlight especially in the near-infrared range. The organization of iridophores into two superposed layers constitutes an evolutionary novelty for chameleons, which allows some species to combine efficient camouflage with spectacular display, while potentially providing passive thermal protection.