Feasibility of Solar Tracking System for PV Panel in Sunbelt Region

In the study of the feasibility of solar tracking systems for crystalline silicon photovoltaic(PV)panels in hot and cold regions,it is argued recently that a tracking system is not necessary for sunbelt countries owing to the overheating that results from excessive exposure to solar irradiance.This conclusion has been formulated based on a mathematical model,which in turn is based on the assumption that the PV module temperature can be calculated using an empirical relation of this temperature to ambient temperature,available solar irradiance,and nominal operation cell temperature(NOCT).To support this conclusion,it is claimed that the mathematical model is validated experimentally.However,this assumption is vague and widely used in the literature.The objective of the present work is to reevaluate the above-mentioned assumption and to discuss the results deriving from it.It is shown experimentally in the present work that the above-mentioned assumption overestimates the PV module temperature.At a solar irradiance of 900 W/m2,ambient temperature of 25℃,and wind speed of 5 m/s,the measured PV module temperature is lower than the value calculated based on the mentioned assumption by 29.26%.

A novel porous channel to optimize the cooling performance of PV modules

This paper dealt with a series of numerical investigations on a new porous cooling channel applied to PV/T systems in order to improve the insufficient heat transfer in the conventional channel.The proposed porous cooling channel based on field synergy theory had a higher overall heat transfer coefficient,which enhanced the total efficiency of the PV/T system.The numerical model was validated with experimental data.The results showed that holes distributed non-uniformly near the outlet of the cooling water led to a better cooling effect,and a hole diameter of 0.005 m led to an optimal performance.The total efficiency of the PV module with the new cooling channel was 4.17%higher than the conventional one at a solar irradiance of 1000 W/m^(2)and an inlet mass flow rate of 0.006 kg/s.In addition,as the solar irradiance increased from 300 to 1200 W/m^(2),the total efficiency of the new PV/T system dropped by 5.07%,which included reductions in both the electrical and thermal efficiency.The total efficiency was improved by 18.04%as the inlet mass flow rate of cooling water increased from 0.002 to 0.02 kg/s.

An Experimental Study on a Microclimatic Layer of a Bionic Facade Inspired by Vertical Greenery

A microclimatic layer of the green facade is proven to have specific temperature and flow conditions on the building en- velope. Lower temperatures and wind velocities, and higher relative humidity in the microclimatic layer are the characteristics of vertical greenery systems, which cause lower energy consumption for the cooling and heating of buildings. Despite innova- tive architectural solutions, there are some drawbacks to applying vertical greenery on building envelopes. In this study, a bionic facade that mimics the positive effects and eliminates the disadvantages of green facades is presented. The bionic fagade consists of bionic leaves, which are made ofphotovoltaic cells and evaporative matrices. A real scale experiment was carried out in the summer to evaluate the potential of the cooling efficiency of the microclimatic layer and a new photovoltaic cooling technique. The results show a good agreement of the thermal performance between the bionic and the green facade and up to 20.8 K lower surface temperatures of photovoltaic cells, which increase the daily electricity yield by 6.6%.