The effect of operating conditions and climate change on the performance of the photopholtaic Trombe

Abstract

Keywords: Building Energy Consumption; Dusty Weather; Electrical and Thermal Efficiency; PV/Trombe Wall

Introduction

Finite fossil fuel supplies are being depleted faster than the rate at which our economy and standards of life are rising, and the fact that we are heavily dependent on fossil fuels due to climate change poses serious concerns.

Therefore, it becomes crucial to research into renewable energy sources with low carbon emissions in order to alleviate carbon emissions and energy scarcity [1]. In the fight against climate change and the expansion of sustainable renewable energy sources, solar energy is becoming more

*Corresponding author. *E-mail address: omerkalil@yahoo.com This paper was recommended for publication in revised form by Associate Editor Tolga Taner Published by Yıldız Technical University Press, İstanbul, Turkey Copyright 2021, Yıldız Technical University. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).

and more significant. As a result, research and development on solar energy is currently focused on a number of construction applications, including as photovoltaics, hot water delivery, heating, and cooling [2]. It is projected that using solar energy on building rooftops and facades will drastically lower energy consumption [3]. Due to its ease of construction, low cost, and excellent efficiency, the Trombe wall has been used as a solar heating system for a while [4]. The TW is made of a large black wall, a clear glass cover, and an air channel between them [5]. In a thermal wall made of materials with a high thermal capacity, such stone, brick, concrete, or sand, heat is produced by the absorption of sunlight. Additionally, the Trombe wall has apertures at the top that allow heat from the air duct to be sent into the building, and openings at the bottom that allow cold air from the building to be transferred to the air duct so that it can be heated again [6]. Also, the Trombe wall was improved by the addition of DC fans. As illustrated in Figure 1, a wall with fans is referred to as a ventilated Trombe wall, and a wall without fans is referred to as a non-ventilated Trombe wall. Heat is transmitted either by conduction and convection or by forced convection (fans) [7]. By removing the generated heat and using it to warm the building on cool days, adding fans boosts the solar panels’ production capacity [8]. In order to lessen the building’s reliance on fossil fuels, enhance its aesthetics, produce energy, and utilize the heat produced by the solar panels to heat the structure, the Trombe wall was additionally upgraded by utilizing solar panels and covering them with a glass covering [9]. One of the most significant problems with solar panels is that they are less effective due to dust accumulation on their surface or excessive heat [10]. This

is because the dust accumulation stops solar radiation (SR) from reaching the silicon photovoltaic (SP). Consequently, dust accumulation alters the thermal balance of the system and raises the temperature over the normal rate, necessitating the cleaning of solar panels in order to maximize their electrical capacity [11]. As a result, numerous studies have concentrated on enhancing the photovoltaic Trombe wall’s performance. Xiao et al. [12] simulated the low-ventilation glass Trombe wall system and compared it with the traditional wall using the Energy Plus tool. The findings demonstrated that the low-ventilation glass Trombe wall system may reduce heating by 11.1 percent in comparison to the classic wall and by 61.4 percent in comparison to the typical wall when paired with air conditioning. Wang et al. [13] investigated how adding heat pipes, which cool the PV Trombe wall with air and refrigerant gas, would affect its performance. The impact of elements influencing the system during the winter was also investigated. The system’s electrical and thermal efficiency increased as a result of these techniques, as evidenced by the average daily thermal efficiency of 56.76 percent. The maximum internal system temperature was 21.46°C, and the average daily electrical efficiency was 13.52 percent. Additionally, 3.12 MJ of total power were generated. On chilly days, a comparison was made by Yadav et al. [14] between an opaque photovoltaic Trombe wall and a semi-transparent one. The findings demonstrated that air flow and wall thickness affect comfort levels. Additionally, the semi-transparent Trombe wall outperformed the opaque wall in terms of effectiveness, as evidenced by the fact that the semi-transparent system’s temperature boost by 15 degrees Celsius over the opaque

wall’s duration. Abdullah et al. [8] investigated the effects of cooling techniques on the PV Trombe wall system’s performance using DC fans and a heat exchanger. The results show that the system with the heat exchanger and DC fans for cooling had the best electrical competence (11.69%), while the system’s thermal efficiency was 39.81%. Siddique et al. [15] created two experimental models, one of which was a photovoltaic Trombe wall system and the other a photovoltaic wall system facing south. Each wall’s performance was assessed in relation to a reference room. The heat gain of the photovoltaic Trombe wall system was 3.2 times greater than that of the south-facing photovoltaic wall system, and the average daily efficiency of the two systems was

Methodology

One of the most common uses is investing in solar energy to generate electricity in poor nations. Nonetheless, a significant factor lowering efficiency is the reduction in solar radiation intensity brought on by climatic variations

and the accumulation of dust on solar panels. Consequently, periodic cleaning of the panels to keep dust from collecting on them increases their effectiveness by allowing more solar energy to be absorbed by the panels. The study site and the experimental work arrangement are described in Section 3. The computations used to estimate competence and performance are described in Section 4. In Section 5, the findings are analyzed and clarified. Conclusions and suggestions are presented in Section 6. Experimental Work Setup The experiments were out at the Hawija Technical Institute in northern Iraq over four days in April (35.19°N, 43.46°E). Figure 2 illustrates two models of the PV Trombe wall system that were created to demonstrate how operational factors and meteorological conditions affect system performance. The two designs consist of a SP, a duct, and a building wall. Additionally, the two designs have lower apertures that draw cold air from the building and transfer it into the duct, as well as upper holes that allow air from the duct to enter the structure. DC fans were incorporated into the top and bottom apertures of one of the experimental designs. In contrast, the second design has no fans because heat is transmitted via the vents naturally by convection. In order to minimize heat loss, the experimental models were constructed and developed using insulated panels in a closed configuration. According to Figure 3. To increase the radiation intensity on the SP, the solar panels were mounted on the southern face, as seen in Figure 4. Polycrystalline SP were employed as the absorbent surface in this investigation. Table 1 displays the photovoltaic panels’ specifications

(1). The airflow channel’s measurements in the designed models are as follows: (width 72 cm, depth 14 cm, height 152 cm).

Figure 3. Diagram showing the dimensions of the insulating panels and the location of the sensors.

An essential component of competency evaluation is temperature measurement. As seen in Figure 3, eleven sensors were used in each model to detect the temperature. Two sensors were positioned on the top openings and two on the lower openings of each of the four sensors that were placed within the test room and the air channel. Additionally, three sensors were installed on the SP’s front face. In addition, I used a Davis Vantage Pro 2 weather station to gauge temperature, wind speed, and sun radiation.

Each embodiment measures the SP voltage and current using a sensor. Additionally, the power generated by the photovoltaic panels was stored in a battery. The electrical output can be used as the control by using an MPPT device. A water pump capable of producing 0.18 liters of water per hour was used, along with an external water tank. The DC fan and water pump specifications are listed in Table 2. The accuracy of the computation tools used in the test is shown in Table 3.

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Formulation of Performance In order to estimate the energy performance of the Trombe wall system under different operating conditions, the electrical and thermic competence of the system will be calculated. The following formula represents the heat gain of the air [28]. (1) The system’s thermal competence in the case of natural convection is the ratio between the amount of heat transferred, the cross-sectional area of the solar panel, and the intensity of solar radiation, which is given by the following equation [29, 30]. (2) The mass flow rate is the amount of mass flowing during a cross-section of the flow system in one unit of time and is denoted by . Air flows inside the channel, and the mass flow rate of the air flowing in a duct is proportional to the air velocity and the duct’s cross-sectional area and density. It can be expressed by the following equation. (3) There are two ways to calculate the air velocity inside the duct: the first is natural convection, which happens when buoyant forces cause the air to move due to differences in density brought on by temperature differences in the air. The velocity is determined using the following equation [31]. (4)

The second status is forced convection, which happens when DC fans are operating and causes air flowI nside the room. The velocity is determined using the formula below [32]. (7) Whereas

A portion of the power production by the SP is consumed by the load and fans, Therefore, the following formula is used to calculate the electrical power [33]. (8) Pconsumed Represents the amount of power used by the fans and load. I, V describe the current and voltage that the solar panels are producing. Using the following formula, the electrical efficiency is calculated [34]. (9) Using the following formula, the total efficiency is calculated. (10)

Results And Discussion

The System’s Temperature The experimental findings from the test days were compared between the fan-containing model and the fan-free second model, taking into account the varying weather conditions on dusty and non-dusty test days. Through the use of DC fans, which assist in cooling the SP and improving the building’s interior comfort, the heat generated by the solar panels is removed. Figure 5 illustrates how climate change and DC fans impact photovoltaics’ temperature. On a day without dust, the temperature of the solar panels was lower when DC fans were used. Without DC fans, the system temperature increased to 54.5oC at 11 a.m. However, the system with DC fans registered a maximum temperature of 51.5oC at noon on the SP. At 12 p.m. on a dusty (cloudy) day, the non-ventilated model without DC fans reached its maximum temperature of 48.7 oC. On a dusty (cloudy) day, the SP temperature decreased when the DC fans were on, with the highest temperature recorded at 34.6oC at 11 a.m. Dust accumulation affects the PV/ TW’s performance. A substantial amount of solar radiation is reflected by dust particles that build up on the surface of photovoltaic panels. As a result, the net SR of the panels is reduced. As a result, the system’s overall competence declines. The implementation of dust-gathering systems on solar panels can mitigate the problem. and clean the photovoltaic cells on a regular basis to avoid this decline and ensure that the solar radiation is at its peak. The temperature variations in the photovoltaic panels are caused by variations in solar radiation intensity; similar behavior was observed in a previous article [35].

Figure 5. The change in the temperature of photovoltaic panels according to operating circumstances. Figure 6 shows how the airway temperature changed. On a day with no dust, at 2:00 pm, the air duct’s maximum temperature was measured to be 50.8°C when the air flow was without fans, that is, under natural convection. At 2:00 PM, the airflow temperature was recorded at 44.5°C on a non-dusty day when forced air flow—the presence of fans—was present. According to the results, the system’s maximum temperature was recorded at 46oC at 1 p.m. and 33oC at 2 p.m. on a dusty day, respectively, under changing weather circumstances and operating circumstances.

Overall, the air duct temperature was lowered by the fans’ presence, which enhanced interior comfort levels. The effects of dusty weather and DC fans on the experimental room temperature are shown in Figure 7. When the DC fans were not operating at 2:00 p.m on a non-dusty day, the room’s temperature registered 39.7°C. When the DC fans are used on a non-dusty (clear) day, the room temperature rises. This is because, around 2 p.m., the maximum temperature in the room was recorded at 40.8°C, thanks to the fans’ efforts to transport the heat generated by the solar panel inside. The

Figure 6. Temperature variation in the ducts based on operating circumstances.

Figure 7. Variation in room temperature according to operating conditions. highest temperature recorded in the room at 2 p.m. on a dusty day without the DC fans running was 34.6°C. At 2 p.m., the experimental system’s highest temperature hit 32.3°C on a dusty day with DC fans running. Note that this time, the experiment room’s temperature is lower than it was in the previous results. The reason for this is that during the day, the high dust in the building caused the interior temperature to drop for different system modes. By transporting heat from a high-temperature air duct to its lower-temperature interior, fans also improve interior thermal comfort [36].

Electrical, Thermal and Total Efficiency Efficiency, which is impacted by operating circumstances and meteorological factors during the experiment, is the fundamental criterion for assessing the efficacy of the planned system. Figure 8 shows how the PV Trombe wall system’s electrical competence is affected by the operating and meteorological variables during the experiment. The increase in solar radiation intensity results in an increase in electrical efficiency all day long, with peak efficiency occurring around midday. Following this point, the SR declines and the electrical efficiency drops as a result. By removing the

Figure 8. The electrical competence of the system varies under different operating circumstances.

Figure 9. Variation in the thermic competence of the system under different operating circumstances. heat produced by the solar panels, DC fans help to cool them down and increase electrical efficiency. In the first status, the top electrical competence recorded 8.2 percent at 11 a.m. when there was no dust and no air cooling, i.e., no fans to cool the solar panel. Nevertheless, around 12 p.m., the peak electrical competency recorded 10.2 percent when the photovoltaic panel was cooled with fans. In the second instance, at 11 a.m., the top electrical competence recorded 3.5 percent in the presence of dust and regular air flow—that is, without fans. At 11 a.m., the highest electrical competence recorded 6.6 percent when air-cooling (via

fans) was applied. The findings showed that when DC fans were installed and the solar panels were being cooled by air, the electrical efficiency rose on non-dusty days. This is in line with earlier research [37]. The system’s thermic competency is shown in Figure 9. Temperature variations and operational conditions affect thermal competency. During the day, the thermal competence increased; in the event of natural convection (without fans), it peaked at 40.1 percent at 11 a.m., but in the case of forced convection (with fans), it reached 17.6 percent at 12 p.m. These results applied to a day without dust. At 12

Figure 10. The aggregate competence of the system under different operating circumstances.

p.m., in the natural convection state, the maximum thermal competence of 34.1 percent was recorded in the presence of dust. At 12 p.m., the maximum thermal competency of

Conclusion

The current article examined how operational conditions and climatic variations affect the photovoltaic Trombe wall’s performance. The primary findings of the experimental investigation were as follows: 1. Due to the effects of dusty weather, both the temperature inside the building and the temperature of the photovoltaic panels drop; the difference between the two recorded a 12 percent drop.

2. The PV Trombe wall system’s electrical competence is

reduced by dusty weather conditions; on a non-dusty day, the average daily in electrical competence was 2.4% higher than on a dusty day.

3. The highest electrical competency was attained on a day

without dust; under forced load conditions (with fans), the competency was 10.2 percent, and under natural load conditions (without fans), it was 8.4 percent.

4. The system’s maximum thermal competence of 17.6

percent was attained on a non-dusty day when the DC fans were operating. While the model without DC fans was, the efficiency was 40.1 percent.

Nomenclatures APV

Photovoltaic panel area [m2] Area of duct [m2] Top slot area [m2] Bottom slot area [m2] The thermal capacity of air [J/kg.K] Loss modulus of the upper vent Loss modulus of the Bottom vent Friction factor along the channel Hydraulic diameter [m] Direct current [A] Height [m] Current [A] Voltage [V]

SP SR g . mair Pelectrical Pconsumed PV Toutair Tinair TW Isolar Vair Qair β ρair ηtotal ηelectrical ηthermal

Solar panel Solar Radiation [W/m2] Gravitational [m/s2] Air mass flow rate [kg/s] net power [W] Consumed energy [W] Photovoltaic The air temperature at the duct exit [K]. The air temperature at the duct inlet [K]. Trombe wall Solar radiation [W/m2] Air velocity [m/s] Gain of heat [W] Coefficient of stretching [1/K] The air’s density [kg/m3] Total efficiency [%] Electrical efficiency [%] Thermal efficiency [%]

Data Availability Statement

The authors confirm that the data that supports the findings of this study are available within the article. Raw data that support the finding of this study are available from the corresponding author, upon reasonable request.

Conflict Of Interest

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethics

There are no ethical issues with the publication of this manuscript.

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