# Simulation of a Low Concentrator Photovoltaic System Using COMSOL
## 1 Introduction  
Photovoltaic cells (PV) are one of the techniques that use sunlight to produce clean and renewable energy by converting solar radiation to electricity [1]. PV cells have high public acceptance due to their safety level since there are no emissions during the production of power. Moreover, the source of fuel (sunlight) needed is vast and unlimited, which makes the cost of operation relatively low. Despite these attractive properties, PV cells at this time cannot be a substitute for fossil fuels. This is due to its low power-conversion efficiency. In addition, PV cells have high industrial manufacturing and installation costs [2]. Since the early days of terrestrial PVs, the attractiveness of focusing sunlight to dramatically decrease the price of PV systems has been foreseen. Much effort has been made to develop cost-effective systems for concentration [3, 4]. The main concept of a concentrator photovoltaic (CPV) is to utilize optical components to concentrate sunlight on a small receiving PV cell; hence the concentration ratio (CR) can reduce the cell area to the focus area provided by the concentrator. Simultaneously, the irradiance on the PV cell can also be increased by the optical components' CR [4]. There are different varieties and classes of CPV, one of which depends on its CR, which is also alternatively defined as the number of suns. According to this, the system can be classified as low (<10 suns), medium (10-100 suns), and high CPV (100-2000 suns) [5, 6, 7]. The main concern in this work is the low-concentration photovoltaic (LCPV) systems. These systems have the prospect to decrease the cost per kWh of electricity in comparison to standard flat-plate PV [8]. The concentrating reflectors employed in LCPV systems are simpler in design and cheaper in manufacturing than high-concentration photovoltaic (HCPV). These static concentrators possess a high acceptance angle and can focus direct and diffuse radiation without the requirement of a tracking system [9; 10]. Different designs have been suggested for LCPV, one of which is a V-trough concentrator that utilizes flat-plate mirrors [8] as shown in Figure 1. For example, [PERSON] and [PERSON] [11] developed and simplified a conceptual description of the optical performance of a V-trough concentrator. They found that the optical performance of diffuse radiation is strongly dependent on the CR and slightly on the vertex angle of the trough. Therefore, a cost-benefit analysis would favor large trough angles when constructing V-trough cavities. In addition, geometric modelling of LCPV and the numerical simulations were done by [PERSON] et al. [12] to find optimized parameters that can lead to maximum incident radiation on the PV cell with a small system size. The authors concluded the CR growth with increasing incident angle. However, the radiation did not depend on the tracking step. More recently, [PERSON] et al. [13] also investigated two cases of the geometrical design of a V-trough based on the width of the mirrors that are attached to a PV panel with an equatorial tracking system. They described the relation between the width of the mirrors and the incident angle of the rays that fall on the system in addition to the inclination angle of the mirrors. They found that the optimum mirror inclination angle was 65\({}^{\circ}\) and that the CR was 2.2x when the reflected rays doubly covered the whole PV surface. Furthermore, CR was 1.6x when minimizing the width of both mirrors and the reflected rays partially swept the PV surface. As a comparison between the effect of a tracking mechanism to a fixed mirror concentrator on PV arrays, [PERSON] et al. [14] studied a practical in-field method conducted in Serdang, Selangor, Malaysia, by installing, monitoring, recording, and analyzing the data for each system separately. They concluded that the contribution of the mirror was high compared to the tracking system with an increase of 14% per day.