Xinyue Han1, Yiping Wang1,2, Qunwu Huang1*and Li Zhu2

1 School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China 2School of Architecture, Tianjin University, Tianjin 300072, China Corresponding Author, hanxinyue123456@163.com

Abstract

In order to further decrease costs of solar electricity, even higher concentrations are needed for photovoltaic concentrating systems. But under high luminous flux, effective cooling is indispensable for concentrator photovoltaic solar cells to keep them operate in high efficiency. In this paper, a high concentrated photovoltaic system with solar cells immersed in a dielectric liquid is designed. The dish is used to provide high concentration and silicon oil is considered as the dielectric liquid to effectively cool the solar cells. The advantages of solar cells immersed in a dielectric liquid and high solar concentration technologies are combined into a CPV system to increase the solar energy conversion efficiency. An analytical model to simulate the thermal behavior of the CPV receiver is proposed. Theoretical analysis shows that concentration ratio, fluid volume flow rate and fluid inlet temperature have great effect on solar cells temperature, and solar cells temperature has little change with environment variables including ambient temperature and wind speed.

Keywords: photovoltaic, high concentration, dish, dielectric liquid, model

1. Introduction

PV power generation systems are attracting considerable attention as sources of electrical power that can replace or complement the current power generation systems that utilize fossil and nuclear fuels. So far, the costs for the solar PV systems are not competitive with other power generation systems. But photovoltaic concentrating systems are a promising path to reduce the cost of solar electricity [1]. In order to further decrease costs, even higher concentrations are needed. However, when concentration of sunlight gets onto solar cells, only a fraction of concentrated sunlight striking the cell is converted into electrical energy (a typical efficiency value for concentrator cells is 27.3% [2]). The larger fraction of concentrated sunlight is converted into thermal energy in the cells which may lead solar cells to high temperature with no cooling aids. It is well known that the efficiency of solar cells decrease with increasing temperature [3]. So cooling of photovoltaic cells is one of the main concerns when designing concentrating photovoltaic systems. Design considerations for cooling systems include low and uniform cell temperatures, system reliability, sufficient capacity for dealing with ‘worst case scenarios’, and minimal power consumption by the system.

Many researchers have attempted to develop HCPV systems and their cooling systems [4,5]. But their costs and reliability for large scale production are yet to be confirmed.

In this work, parabolic dish concentrator was used to provide high-concentration. It is well known that for densely packed cells under high concentrations (> 150 suns), an active cooling system is

necessary. In our HCPV system, solar cells were immersed in a circulated liquid. Solar cells immersed in a dielectric liquid under certain conditions have an increased operating efficiency, and the liquid can provide an effective cooling to the solar cells. Instead, the advantages of solar cells immersed in a dielectric liquid and high solar concentration technologies are combined into a CPV system to increase the solar energy conversion efficiency. The aims of the present paper are: firstly, to preliminarily design a HCPV system and, secondly, to propose and analyze an analytical model that simulated the thermal behavior of receiver.