Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Using high-frequency ultrasound waves and nanofluid for increasing the efficiency and cooling performance of a PV module Zakie Rostami a , Masoud Rahimi a,b, ⁎ , Neda Azimi a a Department of Chemical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran b Department of Chemical Engineering, Razi University, Kermanshah, Iran ARTICLE INFO Keywords: Photovoltaic module Ultrasound Cooling Heat transfer Nanofluid ABSTRACT In this paper, the potential of using high frequency ultrasound for improving cooling performance of a PV module has been investigated experimentally. Atomized CuO nanofluid (0.01–0.8 (w/v)) as well as atomized pure water have been used as coolant fluids. The various parameters such as module surface temperature, maximum power increase and cooling efficiency of PV module using atomized nanofluid have been compared with those of pure water. It has been observed that atomizing the working fluid by ultrasound energy sig- nificantly enhance the cooling performance of the studied PV module. Results depict that cooling by atomized nanofluid was more efficient than cooling by atomized pure water. In addition, increasing the nanofluid con- centration has positive effect on the cooling efficiency and maximum generated power of PV module. Results show that by atomizing 0.8 (w/v) nanofluid, module average surface temperature decreased up to 57.25% and increase in maximum power reached to 51.1% than the layout with no cooling system. 1. Introduction In recent years, due to environmental concern more research focus on diversify away from non-renewable energy sources and develop renewable energy technologies [1,2]. Solar energy is a clean and in- exhaustible renewable energy resource with zero waste generation and no carbon dioxide emissions [3]. Photovoltaic (PV) technology is one of the common methods of direct converting the solar radiation into electricity [4,5]. Only around 15–20% of the incident solar radiation that absorb by the PV module can be converted into electricity and the rest is dissipated as heat [6]. When the ambient temperature during the exposing PV cell in the front of sunlight is high, the surface temperature of PV module increased, which results in decreasing the electrical ef- ficiency [7,8]. Therefore, it is necessary to find efficient cooling methods to achieve higher heat dissipation rates from PV modules. Many innovative active and passive techniques had been used to en- hance the cooling performance of PV modules. In active cooling tech- niques, use of an external driving force is required for the cooling process such as using water spraying [9] and hybrid jet impingement [10], which both methods need a driver to flow the water. Active cooling techniques have high efficiency and result in high generated power and accessible thermal energy. Passive cooling methods divided into three main groups including air passive cooling, water passive cooling and conductive cooling. A special type of passive conductive cooling in PV modules is using a phase change material (PCM), which it had been considered by many authors [11–16]. Sargunanathan et al. [17] performed a comprehensive review of the effective cooling methods of PV modules. Several of these important effective techniques for PV cooling are illustrated in Table 1. Recently, using nanofluids owing to the significant heat transfer characteristics for the cooling performance enhancement of PV modules has been gains more atten- tion [30–36]. Karami et al. [24] used the water-based nanofluid con- taining nanoparticles of Boehmite to enhance the cooling performance of a PV module. Their results show that using nanofluid as working fluid results in higher decrease in the average PV module temperature and have positive effect on cooling performance. In another work conducted by Karami et al. [26], the cooling performance of water- based Boehmite nanofluid in a hybrid photovoltaic (PV) module was evaluated. Cooling performances of water and three different con- centrations of nanofluid were compared. Their results show significant enhancement in the electrical efficiency about 27% for 0.01 wt% con- centration of the nanofluid. In addition, the influence of using nanofluid in a water-cooled PVT system numerically was elucidated by Khanjari et al. [35] and higher electrical efficiency and cooling performance were reported for using nanofluid rather than pure water. Sardarabadi et al. [30] used silica/water nanofluid as a coolant to enhance the performance of a PV/T and reported that the thermal efficiency was increased by adding silica nanoparticles to the working fluid. Hussien https://doi.org/10.1016/j.enconman.2018.01.028 Received 17 November 2017; Received in revised form 27 December 2017; Accepted 13 January 2018 ⁎ Corresponding author at: Chemical Engineering Department, Razi University, Taghe Bostan, Kermanshah, Iran. E-mail address: m.rahimi@razi.ac.ir (M. Rahimi). Energy Conversion and Management 160 (2018) 141–149 0196-8904/ © 2018 Elsevier Ltd. All rights reserved. T