تجزیه و تحلیل عملکرد از متمرکز کننده انعکاس کاملا داخلی متقارن ضدبرق آینه ای برای سیستم های فتوولتائیک یکپارچه ساختمان

This paper presents a mirror symmetrical dielectric totally internally reflecting concentrator (MSDTIRC). Here, its electrical and optical performances are investigated for building integrated photovoltaic applications. This concentrator is designed to tackle two issues: (i) providing sufficient gain in order to increase the electrical output of a solar photovoltaic (PV) system and (ii) reducing the size of the PV cell needed, hence minimising the cost of the system. These experiments carried out had the objective of investigating the characteristics of the cell with the concentrator, the angular performance of the structure, and the effect of temperature on the cell. In each case, the current–voltage (I–V) characteristics and the power–voltage (P–V) characteristics are plotted and analysed. An outdoor experiment was also conducted to verify the results obtained from the indoor experiments. The MSDTIRC-PV structure is capable of providing a maximum power concentration of 4.2× when compared to a similar cell without the concentrator. The deviation of the concentration factor from the geometrical concentration gain (4.9×), is mainly due to manufacturing errors, mismatch losses and thermal losses.

Solar energy is one of the renewable energy sources that has greatest potential. It has been reported that, by 2011, solar photovoltaic (PV) had been introduced in more than 80 countries and was considered the fastest growing power generation technology [1]. In 2011 alone, a staggering 30 GW was installed globally making the global total reach 70 GW – an increase of 79% when compared with the installation carried out in 2010 [1]. The European Union (EU), at the time, dominated the solar PV market (see Fig. 1), led by Germany and Italy, amounting to about 37.8 GW of the total installed PV [1]. The installed PV capacity is dominated by grid-connected installations, mainly due to the introduction of feed-in tariff schemes [2]. The off-grid sector on the other hand has experienced a declining share each year [1]. Full-size image (48 K) Fig. 1. Top 10 global PV market in 2011. Adapted from [1]. Figure options Recently, solar PV started to gain popularity in building integration applications [3]. It was estimated that between 20% and 40% of the world’s energy consumption is consumed in commercial and residential buildings [4]. This figure is projected to experience an upward trend with an increase in the world population, a growth in building services and comfort levels as well as a rise in time spent in a building [4]. For this reason, governments worldwide are looking to design green buildings that can be energy efficient and independently generate energy [5]. Especially in urban environments, solar PV has potential not only for roof mounting, but also for integration in any building parts; i.e. the roof, facades and curtain walls, depending on the location and design of the building [6]. With an improved awareness on renewable energy, substantial financial incentives from governments and the downward trend of solar PV cost, the penetration of building integrated photovoltaic (BIPV) systems is expected to rise sharply globally. China for example started the largest BIPV project in July 2010, with a capacity of 6.68 MW [7]. To further reduce the cost of the BIPV system, an application of PV devices is being introduced, known as the concentrating photovoltaic (CPV) system [8]. The CPV system utilises inexpensive optical device to concentrate light from a large entrance aperture into a smaller exit aperture where a solar cell is attached [8]. Some of the benefits of the CPV systems include: a reduction in total cost of the system due to minimal usage of expensive PV material and a higher electrical output due to the increase in solar flux intensities at the solar cell [8], [9] and [10]. Since 1970s, there are various CPV designs proposed by researchers worldwide. Sellami et al. [9] proposed a CPV system called the Square Elliptical Hyperboloid (SEH) which has the potential to be integrated in double glazed windows. With a concentration value of 4× and acceptance angle of 120° (±60°), an optical efficiency of 40% was recorded. Mammo et al. [11] investigated a reflective 3D crossed compound parabolic-based photovoltaic module (3D CCPC PV). This design is capable of generating a maximum power concentration of 3.0× when compared to similar type of non-concentrating module. Sarmah et al. [12] constructed a CPV system known as the Asymmetric Compound Parabolic Concentrator (ACPC) which generates a maximum power of 1.6 W, 2.1 times the power generated by the non-concentrating counterpart. With a recent downwards trend of solar module price worldwide, the CPV system could still offer some added advantages; namely illumination, hot water and space heating generation, and ventilation. Illumination is achieved by implementing transparent/semi-transparent solar concentrators which allows the daylight to penetrate into the building hence reducing the energy requirement of the building [13]. Among the applications include sky lighting, windows and glass facades [3]. To ensure that the CPV system is working at an optimum level, it is cooled either by water or air. Cooling using water is carried out by attaching a pipe at the bottom of the PV cell, where the heated water is collected and could be used as hot water and for space heating [14]. Cooling by air is achieved by combining the laminar flow effect and the chimney effect, creating good air ventilation for the building [14]. These processes allows the CPV system not only to generate electricity, but also the capability of producing hot water, space heating, ventilation and illumination, which further reduces the electricity requirement in a building, making it more desirable [14], [15], [16] and [17]. This paper proposes a new type of solar concentrator, known as a mirror symmetrical dielectric totally internally reflecting concentrator (MSDTIRC), for use in BIPV systems. Section 2 describes the fabrication process of an MSDTIRC, followed by the experimental setup, which is explained in Section 3. The experimental results are presented and discussed in Section 4. Finally, conclusions are presented in Section

One particular design of an MSDTIRC has been chosen to undergo a series of test. The fabrication process of this concentrator has been discussed thoroughly. Based on the prototype, a series of indoor experiments have been conducted to investigate the electrical performance of the MSDTIRC. The I–V and the P–V characteristics of the MSDTIRC have been evaluated and compared with a typical flat solar cell of a same dimension. An MSDTIRC manages to provide a maximum opto-electronic gain of 4.2× when compared with a flat solar cell. The angular response of the MSDTIRC was investigated and the results from the experiment show good agreement with the ZEMAX® simulation results. The thermal performance of the MSDTIRC has also been evaluated and it has been found that the maximum steady state temperature of the MSDTIRC for the experimental setup used was 58 °C. The calculated value of the maximum current coefficient, voltage coefficient, and power coefficient is 0.000 mA/°C, 2.1212 mV/°C and 0.2727 mW/°C respectively. For the outdoor tests, the electrical performance of the MSDTIRC was observed for a period of 6.5 h. A maximum opto-electronic gain of 3.86 was recorded during a sunny day with a 0° inclination angle with respect to the sun elevation. It has been observed that the gain reduces when the tilt angle of the MSDTIRC with respect to the sun elevation angle increases. It can be concluded that the MSDTIRC has the capability to increase the electrical output of a solar panel when compared with a traditional solar cell. Within its acceptance angle, the gain of an MSDTIRC is much higher than that of a traditional solar cell. However, when the MSDTIRC concentrates the light on the cell, the temperature of the cell also increases. This affects the performance of the cell (attached to the MSDTIRC) where the power is reduced by about 13% when exposed under the sun simulator for a long period of time. Therefore it is necessary to cool the solar cell in order to obtain the maximum electrical output performance.