Concentrating photovoltaic technology is one of the fastest growing solar energy technologies achieving electrical conversion efficiency in excess of 43%. The operating temperature of a solar cell strongly influences the performance of a photovoltaic system reducing its efficiency with a negative temperature coefficient. Thus, cooling systems represent a very important aspect in concentrating photovoltaic applications. This work presents an overview of micro- and nano-technologies applicable to passive CPV cooling and associated manufacturing technologies (such as monolithic applications). Among the different technologies, carbon nano-tubes and high-conductive coating are the most promising technologies to offer the best CPV cooling performance. A critical assessment of the technological review has also been made.

http://biocpv.ex.ac.uk/Opportunities%20and%20challenges%20in%20micro-%20and%20nano-technologies%20for%20concentrating%20photovoltaic%20cooling%20A%20review.pdf

Opportunities and challenges in micro- and nano-technologies for concentrating photovoltaic cooling: A review

Heat transfer—A review of 2005 literature

Forced convection in micro-channels filled with porous media in local thermal non-equilibrium conditions

Study on the convective heat transfer and pressure drop in the micro-channel heat sink

Microchannels enhanced by porous materials: Heat transfer enhancement or pressure drop increment?

The developing hydrodynamic and thermal behaviors of free convection gas flow in a vertical open-ended parallel-plate microchannel filled with porous media are investigated numerically. The extended Darcy-Brinkman-Forchheimer model is used to model the flow in porous medium and the solid and fluid media are not assumed in local thermal equilibrium. The microflow regime considered is the slip flow regime. The slip in velocity and jump in temperature are found to decrease in the axial direction of the flow. The friction factor is found to decrease as Knudsen number, Forchheimer number and Grashof number are increased. However, the friction factor is found to increase as Darcy number increased. On the other hand, Nusselt number is found to decrease as Knudsen number, Darcy number and thermal conductivity ratio are increased, whereas it increased as Forchheimer number, Grashof number and Biot number are increased.

Developing Free-Convection Gas Flow in a Vertical Open-Ended Microchannel Filled with Porous Media

The effect of frequency of fluctuation of the driving force on velocity slip and temperature jump at the wall(s) is theoretically investigated in four cases of basic gas micro-flow problems. The cases considered are the transient Couette flow, the pulsating Poiseuille flow, the Stoke's second problem flow and the transient natural convection flow. The formulation of the problem revealed that the controlling parameter of the problem is a combination of Knudsen number (Kn) and frequency of fluctuation (ω) in the form of an effective Knudsen number, that replaced the usual Knudsen number (Kn), and consequently the slip flow regime is found to be valid when 10-3≤ Kneff≤ 10-1. It is found that when the frequency is small the velocity and temperature profiles are similar to the corresponding classical macro-flow profiles at zero frequency. Also, the slip in velocity and the jump in temperature increase as the Knudsen number and/or the frequency of the driving force increases. In addition, the slip in velocity and the jump in temperature are found to be negligible when the frequency and/or Kn are sufficiently small.

M. M. Abuzaid

Papers

Developing Free-Convection Gas Flow in a Vertical Open-Ended Microchannel Filled with Porous Media

The effect of frequency of fluctuating driving force on basic gaseous micro-flows