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The Future of Solar Energy

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The Future of Solar Energy considers only the two widely recognized classes of technologies for converting solar energy into electricity — photovoltaics (PV) and concentrated solar power (CSP), sometimes called solar thermal) — in their current and plausible future forms. Because energy supply facilities typically last several decades, technologies in these classes will dominate solar-powered generation between now and 2050, and we do not attempt to look beyond that date. In contrast to some earlier Future of studies, we also present no forecasts — for two reasons. First, expanding the solar industry dramatically from its relatively tiny current scale may produce changes we do not pretend to be able to foresee today. Second, we recognize that future solar deployment will depend heavily on uncertain future market conditions and public policies — including but not limited to policies aimed at mitigating global climate change.

As in other studies in this series, our primary aim is to inform decision-makers in the developed world, particularly the United States. We concentrate on the use of grid-connected solar-powered generators to replace conventional sources of electricity. For the more than one billion people in the developing world who lack access to a reliable electric grid, the cost of small-scale PV generation is often outweighed by the very high value of access to electricity for lighting and charging mobile telephone and radio batteries. In addition, in some developing nations it may be economic to use solar generation to reduce reliance on imported oil, particularly if that oil must be moved by truck to remote generator sites. A companion working paper discusses both these valuable roles for solar energy in the developing world.

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Article Contents

1 introduction, 2 materials and methods, 3 experiment setup, 4 results and discussion, 5 conclusions and recommendations, author contributions, appendix a: comprehensive analysis of daily power profiles, monthly, and annual energy yield, b. appendix (b): the specifications of the pyranometer, c. appendix (c): data acquisition system.

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Evaluating the real-world performance of vertically installed bifacial photovoltaic panels in residential settings: empirical findings and implications

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Omar H AL-Zoubi, Hamza Al-Tahaineh, Rebhi A Damseh, A H AL-Zubi, S Odat, B Shbool, Evaluating the real-world performance of vertically installed bifacial photovoltaic panels in residential settings: empirical findings and implications, International Journal of Low-Carbon Technologies , Volume 19, 2024, Pages 386–442, https://doi.org/10.1093/ijlct/ctad138

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This research examines the extended performance of vertically positioned bifacial photovoltaic (BiPV) panels in actual environmental settings, considering various factors such as solar irradiance and the random surrounding structures. Two bifacial photovoltaic panel systems connected to the grid are set up on the roof of a residential structure. The first system consisted of seven panels installed at a tilt angle of 27 o , facing south. The second system comprises seven vertically installed panels facing west. A data acquisition system was employed to continuously monitor and record the electrical parameters of both systems. To quantify the performance of the systems, specific metric parameters, like the yearly energy output and the specific yield of the systems, are computed. The findings reveal that the vertically installed BiPV panels can achieve an energy yield as high as 100% compared with the tilted installation in certain months. Furthermore, the vertical installation demonstrated inherent anti-soiling properties akin to self-cleaning. Additionally, the vertical installation exhibited a multiple peak phenomenon, which could potentially alleviate the peak load issues on the electrical grid. The vertical installation also exhibited an exceptional ground coverage ratio, making it an attractive solution for space-constrained applications. The vertical installation exhibited a ~ 1678 kWh/kWp performance ratio, retaining ~82% of the tilted installation energy yield. The results underscore the feasibility and advantages of employing vertically installed bifacial photovoltaic panels in residential settings, particularly in limited areas. Moreover, the study provides insights into the viability and potential of this technology for small-scale residential applications.

The rising need for eco-friendly and renewable energy solutions has amplified the focus on photovoltaic (PV) systems. Bifacial PV (BiPV) panels, among these technologies, have garnered considerable interest due to their capability to capture sunlight from both surfaces, enhance energy output, and lower the average cost of electricity [ 1 ].

Numerous nations have extensively implemented BiPV panels of late. Some instances include [ 2 ]: China [ 3 ], the United States [ 4 ], Japan [ 5 ], Spain [ 6 ], Qatar [ 7 , 8 ], the United Arab Emirates, and other countries in the Middle East [ 9 ]. Other countries, including Australia, Brazil, India, and several European countries, are deploying BiPV panels on a smaller scale.

However, even though large-scale BiPV use is growing significantly, the deployment of BiPV systems in residential buildings or small-scale facilities faces resistance owing to a variety of factors, such as economic constraints, spatial limitations, maintenance challenges, technological complexity, regulatory obstacles, and the lack of mature knowledge in utilizing BiPV to benefit from their optimal potential. Despite this, bifacial implementation for small-scale residential house applications is becoming increasingly popular in Jordan.

Various studies have employed software tools such as Psys to gauge the performance of BiPV systems [ 10 , 11 ]. In addition, some research efforts have turned to mathematical models to predict the energy output of BiPV systems [ 12 ]. Several studies have conducted practical experiments on the performance of BiPV systems in meticulously designed field experiments [ 13–15 ]. However, many factors, including the surrounding environment, albedo effect, and rear-side shading, influence the performance and energy yield of the BiPV panels. In light of this, our study adopts an experimental approach that evaluates BiPV systems under real-world conditions. This contrasts with studies set in controlled field experiments. We aim to assess the performance and suitability of BiPV systems for residential applications. It’s noteworthy that the majority of research on BiPV panels centers on horizontally installed configurations. This leaves the advantages of vertically installed panels and their potential benefits relatively unexplored [ 16 ].

Vertically installed BiPV (VI-BiPV) panels offer several advantages, such as reduced soiling, better self-cleaning, and lower wind loads [ 17 , 18 ]. Moreover, they can be installed in areas with limited space, which makes them suitable for urban and industrial environments [ 19 ]. Despite these advantages, little research has been conducted on VI-BiPV panels for domestic houses and small-scale applications under realistic operating conditions. This may vary significantly from the idealized conditions often assumed in laboratory settings and mathematical and numerical models [ 20 ].

Despite increasing interest in VI-BiPV panels, a comprehensive understanding of the long-term factors that affect their performance under realistic conditions remains limited. Factors like fluctuating solar radiation, dirt accumulation, shadowing, and ground reflection can impact the energy output of bifacial PV panels [ 5 ].

Calculating the energy production gain is essential for evaluating bifacial PV systems’ profitability [ 21 ]. However, bifacial modules are more complex in simulations due to variations in the illumination of the rear surface [ 22 ]. In addition, compared to monofacial PV modules, the rear side of BiPV modules is more dependent on ground-reflected light [ 23 , 24 ].

Numerous research efforts have delved into the performance of BiPV panels and systems [ 12 , 25–31 ]. These studies have investigated different aspects of BiPV performance, such as energy yield, installation configuration, and shading loss.

In addition to our research on photovoltaic (PV) systems in Jordan [ 32 ], this article comprehensively analyzes the performance of VI-BiPV panels under authentic conditions. It takes into account factors such as varying solar radiation and shadowing effects. Through observations and findings, we aimed to elucidate the advantages of VI-BiPV panels and provide valuable insights for future applications and research. The findings from this research enhance our comprehension of the capabilities of VI-BiPV panels in actual situations, further promoting the embrace of more efficient energy alternatives.

Considering these factors, this work aims to present the long-term performance of VI-BiPV panels under realistic conditions. By analyzing our observations and results, we aim to offer meaningful perspectives on the benefits, constraints, and possible uses of VI-BiPV panels. This provides a better understanding of the practical implications of VI-BiPV panels in real-world scenarios, ultimately supporting the adoption of efficient and sustainable energy solutions.

Our research focuses on key findings from our current long-term experimental project. Instead, we mainly concentrated on the impact of soiling, energy yield, economic considerations, and the feasibility of BiPV systems. Consequently, our core findings and insights are disseminated across the following sections: Introduction, Theoretical Background and Methodology, System Installation Configurations, Results and Discussions, and Conclusions.

BiPV panels are uniquely designed to capture solar power from both their front and rear sides, producing more energy than traditional monofacial panels. The installation orientation of the BiPV panels play a vital role in their performance. In this study, we investigate the performance of two installation configurations of BiPV panel systems by conducting practical experiments and measurements. Multiple factors, such as the tilt angle (β), elevation from the ground (H), and the azimuth angle (γ) of the panels, are taken into account to assess and compare the performance of the two PV systems, with emphasis on vertically installed VI-BiPVs. For this purpose, two solar PV configurations are established in real-world operational settings:

I. A bifacial PV system inclined towards the south.

II. A bifacial PV system vertically installed with east–west orientation.

This section outlines the experimental design, equipment, and methodologies employed to assess the performance of VI-BiPV panels. This exposition provides readers with an understanding of the practical aspects and considerations underpinning this study’s findings.

2.1 Theoretical background

Energy production is influenced by the total solar radiation absorbed by the front and back sides of the BiPV panels. While one side typically captures direct and diffused irradiance, the opposite captures reflected and diffused irradiance. As a result, to gauge the energy output of the BiPV panel, one must calculate the combined solar radiation striking both sides of the panels. Nonetheless, solar radiation can be divided into different elements. Figure 1 represents a simplified depiction of the different possible components of solar irradiance incidents on the BiPV sides.

Schematic depiction of the solar irradiance components incident on the sides of the BiPV panel.

Contrary to monofacial PV panels, albedo, and diffused irradiance significantly affect the overall energy production of BiPV panels. To analyze the energy output of the BiPV panels, it is essential to compute the cumulative solar radiation received by both faces of the BiPV panels. As depicted in Figure 1 , various forms of solar radiation are crucial for examining the energy production of BiPV panels. These are outlined briefly below:

b. Direct normal irradiance (DNI): this is the solar radiation incident per unit of surface area consistently oriented to the sun’s rays at a right angle. This light originates directly from the sun’s present location in the sky along a linear trajectory.

c . Diffuse horizontal irradiance (DHI): the solar irradiance, per unit area, that incident on a consistently horizontal surface, accounting for the solar radiation dispersed by the atmosphere.

While these equations serve as a solid predictive model that predicts the performance and, hence, the energy yield of BiPV panels based on their installation angles, they fall short in complex settings where BiPV panels are placed in non-standard environments with multiple reflections and varying albedos. Therefore, an extended study in actual operational conditions, like ours, is essential.

2.2 Performance parameters

Key performance indicators are vital for assessing the efficiency of PV systems. Typically employed metrics for such evaluations include annual energy, performance ratio, specific yield, capacity utilization factor, and ground coverage ratio. A concise overview of each parameter is as follows:

Illustration comparing ground coverage ratios for (a) horizontally and (b) vertically installed BiPV panels, highlighting the spatial implications of each configuration.

The diagram delineates the spatial implications of each configuration, offering a visual understanding of how the orientation of the BiPV panels can significantly impact the area they cover on the ground. This comparison is crucial for optimizing space utilization and maximizing solar energy capture in architectural designs. Figure 2 demonstrates the importance of considering the installation orientation of BiPV panels in the early stages of building design to ensure the efficient use of space and energy resources.

2.3 PV panel selection

The types of BiPV panel selected for this experimental work are becoming popular and are among the most readily available in the local market. These panels can be considered representative of other types of BiPV modules. Table 1 provides the key specifications of the BiPV panels as follows:

The specifications of the BiPV panels, Model: PS-M72(BF)-370 .

Two different systems are installed on the rooftop. The first system consists of seven BiPV panels facing south with a tilt angle of 27°. The second system is composed of seven BiPV panels installed vertically, with a tilt angle of 90°, facing west. Figs 3 and 4 visually represent these systems, which are situated on a residential rooftop at latitudes of 32.5°N and 36.0°E in Jordan.

(a) A side perspective of the BiPV panels’ installation setup, oriented towards the south. (b) A three-dimensional representation of the south-facing BiPV panels arranged in a tilted configuration. (c) A photograph showcasing the actual installation of the panels on a rooftop.

(a) Illustration of the front-side view of the vertically installed BiPV panels. (b) Side perspective of the same installation. (c) A photograph capturing the actual system installed on the rooftop. (d) A detailed depiction of the installation process and setup.

To evaluate the performance of the vertical installations, we established an experimental system incorporating multiple BiPV panels in a vertical layout. This framework facilitates long-term monitoring of panel performance under various realistic conditions. Moreover, our system’s meticulous design and implementation offer an accurate assessment of the energy yield and the other performance indicators of the BiPV panels when installed vertically.

3.1 Horizontally installed configuration

Figure 3 depicts that the horizontally oriented system consists of seven BiPV panels installed with a southern-facing tilt angle of 27°. The base of these panels is elevated to a height of 1.2 meters, a design choice that significantly enhances the reflected irradiance on the rear side [ 12 ]. To maximize the benefits of bifaciality, the support framework is thoughtfully designed and constructed to avoid any hindrance to solar radiation on the backside of the panels. This strategic design ensures optimal exposure and maximizes the potential benefits of bifacial panel technology.

It is essential to highlight that the conventional approach of installing BiPV panels in a horizontal configuration using a standard support structure often fails to fully exploit the advantages of bifaciality. Such an installation method typically results in a marginal enhancement of the BiPV performance over its monofacial counterpart, with an increase of less than ~5%. This figure is derived from a comprehensive statistical analysis of systems within the local area, not included in this study. Consequently, the unique structure provided in this study for horizontally installed BiPV (HI-BiPV) panels ensures the complete utilization of bifacial benefits, thereby optimizing the performance of the BiPV system.

3.2 Vertical installation configurations

The system comprises seven BiPV panels installed vertically and facing —east–west, 90° tilt angle, and 270° azimuth angle, as demonstrated in Figure 4 . The panels are installed on the rooftop at the height of 1.2 m above the roof surface, as shown in Figure 4(a) . The seven panels are connected as a string to one of the inverters’ maximum power-point tracking ports. The holding structure is composed of stainless steel, designed to ensure minimum shading to the panels. It is worth mentioning that the holding structure, in terms of mass and cost, is less than that of the typical horizontally installed structure. Stainless steel balustrades were added to provide high stability under wind burst loads. A gap is created between the vertical PV panels to provide a lower wind load, as shown in Figure 4(c) . In a concurrent study not presented within this manuscript, we have ascertained that the gaps mentioned above are superfluous when incorporating stainless steel balustrades.

In this arrangement, solar irradiance can be regarded as direct exposure impacting both the rear and front facets of the panels, contingent upon the time of day. Conversely, with HI-BiPV panels, the front side predominantly receives direct solar irradiance throughout the day and year, except during the early morning and late afternoon hours on summer days.

Acknowledging that the environmental conditions depicted in Figure 1 represent an idealized scenario is crucial. As demonstrated in Figure 4 , the terrain and surroundings can be highly irregular and exhibit varying albedo values. Consequently, the approximations made in the mathematical models may not precisely capture the behavior of BiPV panels in such intricate environments. This underscores the necessity for empirical in-field studies, which is the focus of this study.

3.3 Data collection

In this study, data are collected using various measurement devices. This section briefly describes the data collection instruments used along with their specifications.

3.3.1 Irradiance measurements

The pyranometer measures global horizontal irradiance (GHI), which includes direct and diffuse sunlight falling on a surface. The pyranometer logs the data to National Instruments’ CompactRIO, a rugged, high-performance control and automation system for applications requiring high performance and reliability [ 39 ]. CompactRIO logs these data, stores them onboard, and sends them to another system for further processing, analysis, or storage. LabVIEW software analyzes the data, looks for patterns or trends, and controls other systems based on incoming solar irradiance data. The supplementary material in Appendix (C) shows the CompactRIO and a sample of the LabVIEW code used to monitor and analyze the logged data. The frequency of the irradiance measurements is flexible, thanks to the CompactRIO capabilities, and is selected as a sample every minute. The pyranometer specifications are presented in Appendix (B).

3.3.2 Electrical input/output measurements

A Fronius inverter with an integrated data logging system facilitates electrical output measurements. This mechanism is configured to secure readings at consistent five-minute intervals, contributing to forming a comprehensive dataset that promises regularity and detail.

The data logging feature of the inverter is engineered to document all measurements using a dual-modality data-storage approach. The merits of local data storage include ensuring data integrity and safeguarding against potential losses that may arise during Internet disruptions. Concurrently, online storage provides the benefit of remote data access and creates the potential for real-time monitoring, thereby enhancing the overall accessibility and versatility of data usage. The Fronius inverter can measure various parameters, including the DC voltage and current inputs, AC voltage and current, and generated power. These values are logged every five minutes and stored locally and via the Internet.

Continuous biennial performance outcomes have been documented, encapsulating the energy yield and solar irradiance data points. The subsequent subsections represent and discuss these measurements, illustrating daily, monthly, and yearly performance under varying conditions and presenting samples of these measurements. The supplemental resources, Appendix (B), contain the daily, monthly, and yearly energy yield throughout the experimental timeframe.

4.1 Energy yield and performance

In the subsequent sections, we present the energy yield and the performance of Bi-PV panels, focusing on daily and monthly variations and examining trends over extended periods.

4.1.1 Daily energy yield and performance

The unique multi-peak characteristic of vertically installed bifacial photovoltaic (VI-BiPV) panels has been a focal point in numerous theoretical analyses, predicting a symmetrical power profile for such vertically oriented BiPV modules [ 24 , 40 ]. Through the defined mathematical framework (Equations 1–3), we modeled the power output profile of BiPV panels, enabling the creation of a power profile that correlates power output with daily time. Figure 5 illustrates the power profile of BiPV systems under two distinct orientations: horizontally with a southern inclination and vertically oriented in an east–west direction, providing a normalized power profile that allows a comparative view of the performance dynamics of BiPV installations in these configurations.

Normalized power profile of BiPV panel installations. The power performance of BiPV systems in two orientations: horizontal (tilted south) and vertical (east–west). The analysis assumes a bifaciality factor of 100% under clear sky conditions on a specific day in the year and location on Earth.

However, despite our practical observations revealing a similar trend, we noticed an asymmetrical profile, as shown in Figure 6 . The asymmetrical profile can be attributed to two key factors: the bifaciality factor (BF), which was 75% in our case, as defined in Equation (1), and the shading caused by the module’s frame. Multiple peaks in the power profile of VI-BiPV modules offer significant advantages in load distribution and peak power management. This can help to avoid the power concentration typically observed in HI-BiPV panels, which has important implications for grid stability.

Samples of the measured daily power profile of the Hi-BiPV and VI-BiPV systems under different weather conditions several times a year.

Figure 6 illustrates the measured daily performance of the BiPV panels installed in horizontal and vertical orientations across different seasons. This representation provides insight into how environmental conditions and seasonal variations significantly influence the energy yield of both configurations. The plot legend in Figure 6 shows each system’s daily energy yield, allowing a day-to-day performance comparison. The inset in the graphs shows the total daily energy yield for both systems, indicating the overall performance in terms of energy yield. The subfigures in Figure 6 represent the performance from sample days in various seasons under various conditions. The complete data gathered during this long-term experimental work are presented in the figures in Appendix (A).

The measured GHI is superimposed on the graph, highlighting the correlation between solar irradiance and energy yield. Notably, the power profile of the vertically installed BiPV modules exhibited a distinct pattern characterized by multiple peaks. This contrasts with the power profile of the horizontally installed modules, which typically concentrate power at peak times, usually at noon.

On sunny days, the power profile became more pronounced, revealing the impact of sunlight intensity on energy yield. The total energy yields of the VI-BiPV and HI-BiPV modules varied depending on the season. For instance, the energy yield from HI-BiPV modules on sunny winter days surpasses that of VI-BiPV modules despite the overall lower energy availability in winter than in summer. Conversely, during the summer months (May, June, and July), the VI-BiPV modules yielded more energy than the HI-BiPV modules.

Similar trends in the power generation performance of both systems are observed on partially cloudy days, with both systems producing comparable energy yields, as depicted in Figure 6 (d). For the HI-BiPV, there is a notable utilization of solar irradiation during the mornings and afternoons on summer days, which could be highly beneficial for specific applications.

The VI-BiPV system displays a noticeably superior performance during numerous days in May, June, and July. This enhanced efficiency is explicitly illustrated in the power profile samples, as indicated in Figure 6 . Further details regarding the daily performance can be found in Appendix (A.1) of the supplementary material. However, during winter, the horizontally installed BiPV (HI-BiPV) system proves more effective than the VI-BiPV system. This superior winter performance of the HI-BiPV system is well-demonstrated in Figs 6 (e) and (f). Therefore, even though the VI-BiPV system can outperform the HI-BiPV during certain months, the overall performance is contingent on seasonal changes. As expected, the daily performance varies from fully sunny to partially cloudy days. Moreover, as expected, the performance on sunny days also varied between the seasons. A critical aspect to consider is the differential energy yield of the Vi-BiPV and HI-BiPV panels during the summer and winter. As indicated in Figure 6 and Appendix (A), the energy yield of the VI-BiPV panels is equivalent to or sometimes surpasses that of the HI-BiPV panels during the summer.

Conversely, during winter, the energy yield of the VI-BiPV panels is lower than that of the HI-BiPV panels. Although it might at first seem like a performance shortfall, it is crucial to recognize that the increased energy output in the summer is due to particular reasons, detailed in the subsequent section.

The incident angle of light, frame shading, and bifaciality factor emerge as pivotal physical determinants that render VI-BiPV systems inferior to HI-BiPV in wintertime. The VI-BiPV’s susceptibility to suboptimal light angles and potential shading, coupled with the nuanced implications of BF on energy yield, collectively compromise its comparative performance, especially in contexts where optimal, direct sunlight exposure is paramount for maximizing photovoltaic efficiency.

Despite these factors, in winter, shorter daylight hours, lower solar irradiance, and frequent overcast skies can distort the energy yield percentage, making it an unreliable overall performance measure. Therefore, a comprehensive understanding of these seasonal variations is crucial to assess the performance of the BiPV systems.

4.1.2 Monthly energy yield and performance

The cumulative monthly energy output is depicted in Figure 7 below. The legend in the graph shows the total energy yield over the whole month in kWh. In late spring, summer, and early autumn, the energy yield of the VI-BiPV panels is close to that of the HI-BiPV panels, and sometimes it surpasses it. This is due to the VI-BiPV panels harnessing the direct solar rays more effectively during the early morning and late afternoon. After all, the early morning and late afternoon solar irradiance is directly incident on one of the panel surfaces. On summer days, the HI-BiPV can capture direct sunlight on its rear side in the early morning and late afternoon. However, this solar irradiance would be less effective than that in the VI-BiPV panels because of the low solar irradiance and the far normal incidence angle on the rear side of the panel. This phenomenon can be seen in May and June, as shown in Figure 7 , where samples of the monthly energy yield for the winter, spring, summer, and autumn are shown. The total energy yield over each month is inserted as an inset in the plot with a vertical-to-horizontal yield percentage. Appendix (A.2) of the supplementary material contains the monthly performance over the experiment period.

Comparative analysis of seasonal energy yield: this figure illustrates the energy output during summer and winter months across various years, providing a representative sample of seasonal variations in energy production.

Table 2 compares the monthly and specific energy yields of two installed systems. It reveals that both systems perform comparably, with the HI-BiPV exhibiting performance nearly equivalent to that of the VI-BiPV from May through September. The energy yield of the VI-BiPV is remarkably high, reaching up to 100% of the HI-BiPV’s daily yield in May through October. However, during winter, the VI-BiPV’s yield declines to as low as 62% compared to the HI-BiPV. This decrease is anticipated and can be attributed primarily to the shading of the frame panels on the rear side. Additionally, the sun’s lower elevation and azimuth angles during winter in the experiment’s region exacerbates the shading effect on the VI-BiPV panel. Notably, the panels’ frame also contributes to shading, even in summer, but with a less pronounced impact on the VI-BiPV’s overall performance.

Comparison between the performance of the vertical and horizontal BiPV systems.

4.1.3 Yearly energy yield

Figure (9) presents the energy yield accumulated over a two-year experimental period. The energy generation profile throughout the year is consistent with expected patterns. The data, spanning July 2021 to July 2023, offers definitive insights into the system’s long-term performance.

The VI-BiPV panels generate higher energy yields during summer than the HI-BiPV panels, as depicted in Figure 8 . Specifically, in May, June, and July, the energy yield of VI-BiPV panels exceeds that of HI-BiPV panels. In contrast, VI-BiPV panels yield less energy than HI-BiPV panels during winter.

Monthly energy yield analysis of HI-BiPV and VI-BiPPV systems: this figure presents a month-by-month breakdown of the energy yields for both the HI-BiPV and VI-BiPPV systems, spanning the duration of the experimental period, 24 months.

Over the 24 months, the VI-BiPV panels achieved a relative energy yield of approximately 82% compared to HI-BiPV panels. This yield is comparable to, or even surpasses, monofacial PV panels. The lower energy yield of VI-BiPV relative to HI-BiPV is attributed to bifacial factors and self-shading from the panel frames.

This in-depth analysis provides a basis for making informed decisions on deploying bifacial PV panels. It emphasizes the significance of installation configurations in optimizing energy yields.

The VI-BiPV panels exhibit an annual specific yield of ~1673 kWh/kWp, which is on par with the typical yield of monofacial PV panels in Jordan [ 36 ]. Notably, in this study, the optimally installed HI-BiPV panels achieve an annual specific yield of ~2000 kWh/kWp, marking a 20% improvement over the VI-BiPV. This enhancement, relative to VI-BiPV panels, is ascribed to the self-shading caused by the panel frames and a bifacial factor of 75%, as previously discussed. Based on Equations (6 and 8), PR and CUF for the VI-BiPV were determined to be approximately 81% and 19%, respectively. These values are derived from two years of long-term experimental data.

4.2 Inverter loading

The inverter loading ratio (ILR), also called the DC/AC ratio, indicates the relationship between a PV system’s DC nameplate capacity and its associated inverter’s AC nameplate capacity. Implementing bifacial modules can increase energy yield, which elevates the DC/AC ratio due to more significant DC power generation per module compared to their monofacial counterparts possessing equivalent nameplate power ratings.

However, it is critical to note the downside of this enhanced efficiency, which includes increased clipping losses or potential wasted energy during peak production periods. In most instances, the benefits of the additional yield from bifacial production offset these losses, validating the shift to bifacial technology.

Peak clipping in PV power profiles denotes a phenomenon that transpires when the power generated by a PV system surpasses the inverter’s capacity. Inverters are engineered to convert the DC power produced by solar panels into AC power appropriate for grid or domestic consumption. However, each inverter possesses a maximum power threshold it can manage. If the PV system’s power output exceeds this threshold, the inverter will limit or ‘clip’ the output power to its maximum capacity. This creates a flat peak on the power output curve, hence the term ‘peak clipping’. The power generated by the PV system that is not transformed by the inverter is effectively wasted, which can diminish the total efficiency of the PV system.

Therefore, the potential increase in energy output from HI-BIPV panels may be limited due to the operational characteristics of the inverter, which can result in power clipping, especially during peak energy production periods. Figure (9) visually depicts the increased energy yield from bifacial modules contrasted with clipping losses. The total energy clipped is represented by the area under each respective curve. Fundamentally, a bifacial system with a lower DC/AC ratio could achieve equivalent performance to a monofacial system with a higher DC/AC ratio, implying that bifacial modules provide a superior return on investment.

Comparative analysis of power profiles in bifacial and monofacial PV systems over time. This figure illustrates the normalized power outputs from (a) inclined bifacial and equivalent tilted monofacial systems and (b) inclined and vertically positioned bifacial systems, highlighting the occurrence of clipping loss in each setup.

In the case of the VI-BiPV panels, inverter overloading and peak clipping are circumvented, as multiple peaks manifest below the clipping threshold. This is evident in Figure 9 and is further corroborated by empirical testing, which shows no peak clipping for VI-BiPV panels throughout the study, especially during summer.

4.3 Anti-soiling property

An exciting and significant feature of the VI-BiPV is the anti-soiling property. Figure 10 presents images captured for the VI-BiPV and the HI-BiPV panels at the exact location six months post-installation. The unambiguous contrast in soiling accumulation between the two systems is a striking observation from the images. The VI-BiPV panels exhibit remarkable resilience to soiling, appearing almost pristine, whereas the HI-BiPV panels are visibly marred by heavy soiling.

Photographic depiction of panel soiling in both systems: (a) displays the soiling on the HI-BiPV system with tilted panels oriented southward; (b) showcases the soiling on the VI-BiPV system (right side of the image) alongside the tilted panels (left side of the image).

The implications of this observation are profound within the realm of photovoltaic energy generation. Soiling, which refers to the accumulation of dirt and debris on the surface of photovoltaic panels, is a well-documented impediment to optimal energy yield. It attenuates the incident solar radiation, thereby curtailing the panels’ electrical output. Consequently, frequent cleaning interventions are necessitated to sustain the projected energy yield. However, these cleaning processes are not without cost and contribute to the overall levelized cost of electricity of a photovoltaic system, which is a critical metric for evaluating the economic feasibility of solar installations.

In light of these considerations, the inherent resistance of VI-BiPV panels to soiling emerges as a highly advantageous attribute. By substantially reducing, if not altogether eliminating, the need for regular cleaning, the adoption of vertically installed configurations can yield significant operational efficiencies. This can positively influence the levelized cost of electricity, enhancing the economic feasibility of solar setups. Moreover, it alleviates the logistical challenges associated with maintenance, particularly in regions where accessibility is a constraint.

In conclusion, the implementation of VI-BiPV panels represents a promising avenue for mitigating the detrimental effects of soiling on photovoltaic systems and warrants further investigation and consideration in the design and deployment of future solar installations.

4.4 Implications for BiPV panel installation

Bifacial photovoltaic (PV) panels represent a significant advancement in solar technology, primarily due to their ability to capture sunlight on both their front and back sides, leading to increased energy production compared to traditional monofacial panels. Nevertheless, the way these BiPV panels are installed plays a crucial role in tapping into these benefits.

It's crucial to understand that if not installed correctly, the dual-sided nature of these panels might not offer the expected advantages. Thus, careful planning and design are essential when setting up BiPV panels to make the most out of bifacial technology. One effective approach is mounting the panels vertically. This setup helps avoid the problem of shadowing from the structure itself, which can significantly reduce energy generation, thereby making the most of the bifacial panels' capabilities.

However, opting for a vertical layout comes with its own set of challenges, such as ensuring the panels can withstand wind and maintain structural stability. Addressing these issues requires detailed technical advice and the creation of thorough guidelines for installation, maintenance, and safety. When planning the installation, factors like local wind conditions, structural strength, and maintenance ease should be carefully considered.

Beyond performance enhancements, vertically mounted BiPV panels can also improve the visual appeal of the site. Their sleek, contemporary look can be seamlessly integrated into architectural designs or used in practical applications like fencing. This aspect is especially useful in areas where maximizing land use is crucial, and blending functionality with design appeal is greatly appreciated.

In summary, although bifacial PV panels promise higher energy outputs, achieving these gains largely depends on how they're installed. Vertical mounting stands out as a feasible strategy, but it demands careful attention to details such as wind resistance, structural stability, and upkeep. Moreover, the aesthetic and functional flexibility of vertically installed panels offers additional benefits, enhancing their value beyond just energy efficiency.

4.5 Future research

While bifacial PV panels and their vertical installation present promising opportunities for enhancing energy yield, certain limitations and areas warrant further research.

One of the primary limitations is the absence of mature technical guidelines for installation companies. There is a noticeable lack of clarity regarding the dos and don’ts of installing bifacial PV panels, particularly in vertical configurations. This lack of standardized instructions can lead to inconsistencies and inefficiencies in installation practices.

A specific area that requires attention is the study of wind loading on the VI-BiPV panels and the design of appropriate support structures. While this study does not delve into the intricacies of wind loading, future research must develop comprehensive guidelines and formulas that can aid installers in designing robust and reliable support structures.

Another limitation pertains to regulatory constraints, especially concerning the height of vertically installed panels on the rooftops of residential apartments. Vertical installation is an attractive solution for deploying solar PV systems in apartments with limited space. However, in some jurisdictions, regulations may restrict such installations due to aesthetic considerations, particularly in urban areas. Understanding local regulations clearly and working towards regulatory frameworks that balance aesthetic concerns with the benefits of renewable energy deployment is essential.

Vertical installation is more feasible for individual residential houses as it is less likely to be constrained by stringent regulations or aesthetic considerations.

In conclusion, while the VI-BiPV panels hold promise, addressing the technical and regulatory limitations through rigorous research and collaboration with stakeholders is essential. Future research should focus on developing technical guidelines, studying wind loads, and engaging with regulatory bodies to create an enabling environment for the widespread adoption of this technology.

The energy yield from VI-BiPV panels is presently less than that of HI-BiPV panels. To enhance energy yield, two primary methods can be employed: first, by using frameless BiPV panels, which eliminates the shading from frames and thereby increases energy output, and second, by adopting a higher BF, a change that can notably boost the energy yield, as inferred from Figure 7 .

The exploration of building-integrated photovoltaic (BiPV) panels, specifically focusing on vertical integration (VI-BiPV) and horizontal integration (HI-BiPV) configurations, has unveiled a spectrum of findings that not only underscores the potential of these technologies but also illuminates pathways for their optimized deployment in various operational settings. This study, spanning a period of two years, meticulously analyzes the performance, energy yield, and additional properties of the two BiPV systems, one vertically aligned and the other horizontally inclined to the south, in real-world operational settings. The findings and observations derived from this study are pivotal, providing practical solutions to prevalent challenges in deploying PV systems, such as peak loading, soiling, and applications in limited-space scenarios.

5.1 Key findings

The findings of this study illuminate the multifaceted performance and additional properties of VI-BiPV and HI-BiPV panels, providing a comprehensive understanding of their respective efficiencies, anti-soiling characteristics, and installation prerequisites. The key findings are as follows:

Energy yield and performance:

VI-BiPV panels exhibit multiple peak power profiles, enhancing load distribution and grid stability.

VI-BiPV panels demonstrate superior performance in the summer, while HI-BiPV panels prevail in winter.

Seasonal changes and weather conditions influence the overall performance of both systems.

VI-BiPV panels mitigate inverter overloading and peak clipping, particularly during summer.

Anti-soiling property: VI-BiPV panels demonstrate notable resistance to soiling, thereby minimizing maintenance requirements.

Proper installation: the efficacy of BiPV panels is significantly influenced by their installation, emphasizing the necessity of adherence to optimal installation practices.

Vertical installation: vertical installation offers benefits such as reduced holding structure shading but necessitates mechanical stability and wind tolerance considerations.

In summary, VI-BiPV panels, characterized by their anti-soiling property and distinctive power profile, emerge as a promising frontier in solar energy generation.

5.2 Limitations and future research

Despite the promising findings, the study acknowledges several limitations and areas warranting future research:

The absence of technical guidelines for installing VI-BiPV panels poses a significant challenge.

Regulatory constraints in certain regions may impede the widespread adoption of BiPV technologies.

Future research avenues may explore potential enhancements, such as using frameless BiPV panels and augmenting the bifaciality factor.

5.3 Recommendations

In light of the findings and acknowledged limitations, the following recommendations are proposed:

The performance of BiPV panels can potentially be enhanced by using frameless panels coupled with a high bifaciality factor.

There is a palpable need to develop comprehensive technical guidelines and robust stakeholder engagement to foster the adoption and optimized deployment of BiPV technologies.

In conclusion, the insights derived from this study pave the way for not only harnessing the potential of VI-BiPV panels but also for navigating the challenges and limitations inherent in their deployment, thereby contributing to the advancement of sustainable energy solutions.

Omar AL-Zoubi (Conceptualization [Lead], Data curation [Lead], Formal analysis [Lead], Funding acquisition [Lead], Investigation [Lead], Methodology [Lead], Project administration [Lead], Resources [Equal], Software [Lead], Supervision [Lead], Validation [Equal], Visualization [Equal], Writing—original draft [Lead], Writing—review & editing [Lead]), A.H. AL-Zoubi (Data curation [Equal], Software [Equal], Validation [Equal]), Hamza Al-Tahaineh (Supervision [Supporting], Validation [Equal], Visualization [Equal], Writing—original draft [Equal]), Rebhi Damseh (Validation [Equal], Visualization [Equal], Writing—original draft [Equal]), S. Odat (Visualization [Supporting], Writing—original draft [Supporting]), and B. Shbool (Visualization [Supporting], Writing–original draft [Supporting])

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A.1. The daily power profile, with daily energy yield for both systems as inset in the plot

A.2. The monthly energy yields

A.3. The yearly energy yield

Appendix (B): the specifications of the pyranometer

The pyranometer specifications .

Appendix (C): data acquisition system

C.1. image of the national-instrument compact roi data logging system.

C.2. Sample of the LabVIEW program code implemented for data logging, saving, and monitoring

C.3. Image of the front panels showing the real-time monitoring of system parameters

Supplementary data

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Solar photovoltaic technology: A review of different types of solar cells and its future trends

Mugdha V Dambhare 1 , Bhavana Butey 1 and S V Moharil 2

Published under licence by IOP Publishing Ltd Journal of Physics: Conference Series , Volume 1913 , International Conference on Research Frontiers in Sciences (ICRFS 2021) 5th-6th February 2021, Nagpur, India Citation Mugdha V Dambhare et al 2021 J. Phys.: Conf. Ser. 1913 012053 DOI 10.1088/1742-6596/1913/1/012053

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1 G H Raisoni College of Engineering, Nagpur, India

2 Department of Physics, PGTD, Nagpur

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The Sun is source of abundant energy. We are getting large amount of energy from the Sun out of which only a small portion is utilized. Sunlight reaching to Earth's surface has potential to fulfill all our ever increasing energy demands. Solar Photovoltaic technology deals with conversion of incident sunlight energy into electrical energy. Solar cells fabricated from Silicon aie the first generation solar cells. It was studied that more improvement is needed for large absorption of incident sunlight and increase in efficiency of solar cells. Thin film technology and amorphous Silicon solar cells were further developed to meet these conditions. In this review, we have studied a progressive advancement in Solar cell technology from first generation solar cells to Dye sensitized solar cells, Quantum dot solar cells and some recent technologies. This article also discuss about future trends of these different generation solar cell technologies and their scope to establish Solar cell technology.

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Researchers find benefits of solar photovoltaics outweigh costs

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Over the past decade, the cost of solar photovoltaic (PV) arrays has fallen rapidly. But at the same time, the value of PV power has declined in areas that have installed significant PV generating capacity. Operators of utility-scale PV systems have seen electricity prices drop as more PV generators come online. Over the same time period, many coal-fired power plants were required to install emissions-control systems, resulting in declines in air pollution nationally and regionally. The result has been improved public health — but also a decrease in the potential health benefits from offsetting coal generation with PV generation.

Given those competing trends, do the benefits of PV generation outweigh the costs? Answering that question requires balancing the up-front capital costs against the lifetime benefits of a PV system. Determining the former is fairly straightforward. But assessing the latter is challenging because the benefits differ across time and place. “The differences aren’t just due to variation in the amount of sunlight a given location receives throughout the year,” says  Patrick R. Brown PhD ’16, a postdoc at the MIT Energy Initiative. “They’re also due to variability in electricity prices and pollutant emissions.”

The drop in the price paid for utility-scale PV power stems in part from how electricity is bought and sold on wholesale electricity markets. On the “day-ahead” market, generators and customers submit bids specifying how much they’ll sell or buy at various price levels at a given hour on the following day. The lowest-cost generators are chosen first. Since the variable operating cost of PV systems is near zero, they’re almost always chosen, taking the place of the most expensive generator then in the lineup. The price paid to every selected generator is set by the highest-cost operator on the system, so as more PV power comes on, more high-cost generators come off, and the price drops for everyone. As a result, in the middle of the day, when solar is generating the most, prices paid to electricity generators are at their lowest.

Brown notes that some generators may even bid negative prices. “They’re effectively paying consumers to take their power to ensure that they are dispatched,” he explains. For example, inflexible coal and nuclear plants may bid negative prices to avoid frequent shutdown and startup events that would result in extra fuel and maintenance costs. Renewable generators may also bid negative prices to obtain larger subsidies that are rewarded based on production. 

Health benefits also differ over time and place. The health effects of deploying PV power are greater in a heavily populated area that relies on coal power than in a less-populated region that has access to plenty of clean hydropower or wind. And the local health benefits of PV power can be higher when there’s congestion on transmission lines that leaves a region stuck with whatever high-polluting sources are available nearby. The social costs of air pollution are largely “externalized,” that is, they are mostly unaccounted for in electricity markets. But they can be quantified using statistical methods, so health benefits resulting from reduced emissions can be incorporated when assessing the cost-competitiveness of PV generation.

The contribution of fossil-fueled generators to climate change is another externality not accounted for by most electricity markets. Some U.S. markets, particularly in California and the Northeast, have implemented cap-and-trade programs, but the carbon dioxide (CO 2 ) prices in those markets are much lower than estimates of the social cost of CO 2 , and other markets don’t price carbon at all. A full accounting of the benefits of PV power thus requires determining the CO 2  emissions displaced by PV generation and then multiplying that value by a uniform carbon price representing the damage that those emissions would have caused.

Calculating PV costs and benefits

To examine the changing value of solar power, Brown and his colleague Francis M. O’Sullivan, the senior vice president of strategy at Ørsted Onshore North America and a senior lecturer at the MIT Sloan School of Management, developed a methodology to assess the costs and benefits of PV power across the U.S. power grid annually from 2010 to 2017. 

The researchers focused on six “independent system operators” (ISOs) in California, Texas, the Midwest, the Mid-Atlantic, New York, and New England. Each ISO sets electricity prices at hundreds of “pricing nodes” along the transmission network in their region. The researchers performed analyses at more than 10,000 of those pricing nodes.

For each node, they simulated the operation of a utility-scale PV array that tilts to follow the sun throughout the day. They calculated how much electricity it would generate and the benefits that each kilowatt would provide, factoring in energy and “capacity” revenues as well as avoided health and climate change costs associated with the displacement of fossil fuel emissions. (Capacity revenues are paid to generators for being available to deliver electricity at times of peak demand.) They focused on emissions of CO 2 , which contributes to climate change, and of nitrogen oxides (NO x ), sulfur dioxide (SO 2 ), and particulate matter called PM 2.5 — fine particles that can cause serious health problems and can be emitted or formed in the atmosphere from NO x  and SO 2 .

The results of the analysis showed that the wholesale energy value of PV generation varied significantly from place to place, even within the region of a given ISO. For example, in New York City and Long Island, where population density is high and adding transmission lines is difficult, the market value of solar was at times 50 percent higher than across the state as a whole. 

The public health benefits associated with SO 2 , NO x , and PM 2.5  emissions reductions declined over the study period but were still substantial in 2017. Monetizing the health benefits of PV generation in 2017 would add almost 75 percent to energy revenues in the Midwest and New York and fully 100 percent in the Mid-Atlantic, thanks to the large amount of coal generation in the Midwest and Mid-Atlantic and the high population density on the Eastern Seaboard. 

Based on the calculated energy and capacity revenues and health and climate benefits for 2017, the researchers asked: Given that combination of private and public benefits, what upfront PV system cost would be needed to make the PV installation “break even” over its lifetime, assuming that grid conditions in that year persist for the life of the installation? In other words, says Brown, “At what capital cost would an investment in a PV system be paid back in benefits over the lifetime of the array?” 

Assuming 2017 values for energy and capacity market revenues alone, an unsubsidized PV investment at 2017 costs doesn’t break even. Add in the health benefit, and PV breaks even at 30 percent of the pricing nodes modeled. Assuming a carbon price of $50 per ton, the investment breaks even at about 70 percent of the nodes, and with a carbon price of $100 per ton (which is still less than the price estimated to be needed to limit global temperature rise to under 2 degrees Celsius), PV breaks even at all of the modeled nodes. 

That wasn’t the case just two years earlier: At 2015 PV costs, PV would only have broken even in 2017 at about 65 percent of the nodes counting market revenues, health benefits, and a $100 per ton carbon price. “Since 2010, solar has gone from one of the most expensive sources of electricity to one of the cheapest, and it now breaks even across the majority of the U.S. when considering the full slate of values that it provides,” says Brown. 

Based on their findings, the researchers conclude that the decline in PV costs over the studied period outpaced the decline in value, such that in 2017 the market, health, and climate benefits outweighed the cost of PV systems at the majority of locations modeled. “So the amount of solar that’s competitive is still increasing year by year,” says Brown. 

The findings underscore the importance of considering health and climate benefits as well as market revenues. “If you’re going to add another megawatt of PV power, it’s best to put it where it’ll make the most difference, not only in terms of revenues but also health and CO 2 ,” says Brown. 

Unfortunately, today’s policies don’t reward that behavior. Some states do provide renewable energy subsidies for solar investments, but they reward generation equally everywhere. Yet in states such as New York, the public health benefits would have been far higher at some nodes than at others. State-level or regional reward mechanisms could be tailored to reflect such variation in node-to-node benefits of PV generation, providing incentives for installing PV systems where they’ll be most valuable. Providing time-varying price signals (including the cost of emissions) not only to utility-scale generators, but also to residential and commercial electricity generators and customers, would similarly guide PV investment to areas where it provides the most benefit. 

Time-shifting PV output to maximize revenues 

The analysis provides some guidance that might help would-be PV installers maximize their revenues. For example, it identifies certain “hot spots” where PV generation is especially valuable. At some high-electricity-demand nodes along the East Coast, for instance, persistent grid congestion has meant that the projected revenue of a PV generator has been high for more than a decade. The analysis also shows that the sunniest site may not always be the most profitable choice. A PV system in Texas would generate about 20 percent more power than one in the Northeast, yet energy revenues were greater at nodes in the Northeast than in Texas in some of the years analyzed. 

To help potential PV owners maximize their future revenues, Brown and O’Sullivan performed a follow-on study focusing on ways to shift the output of PV arrays to align with times of higher prices on the wholesale market. For this analysis, they considered the value of solar on the day-ahead market and also on the “real-time market,” which dispatches generators to correct for discrepancies between supply and demand. They explored three options for shaping the output of PV generators, with a focus on the California real-time market in 2017, when high PV penetration led to a large reduction in midday prices compared to morning and evening prices.

• Curtailing output when prices are negative: During negative-price hours, a PV operator can simply turn off generation. In California in 2017, curtailment would have increased revenues by 9 percent on the real-time market compared to “must-run” operation.
• Changing the orientation of “fixed-tilt” (stationary) solar panels: The general rule of thumb in the Northern Hemisphere is to orient solar panels toward the south, maximizing production over the year. But peak production then occurs at about noon, when electricity prices in markets with high solar penetration are at their lowest. Pointing panels toward the west moves generation further into the afternoon. On the California real-time market in 2017, optimizing the orientation would have increased revenues by 13 percent, or 20 percent in conjunction with curtailment.
• Using 1-axis tracking: For larger utility-scale installations, solar panels are frequently installed on automatic solar trackers, rotating throughout the day from east in the morning to west in the evening. Using such 1-axis tracking on the California system in 2017 would have increased revenues by 32 percent over a fixed-tilt installation, and using tracking plus curtailment would have increased revenues by 42 percent.

The researchers were surprised to see how much the optimal orientation changed in California over the period of their study. “In 2010, the best orientation for a fixed array was about 10 degrees west of south,” says Brown. “In 2017, it’s about 55 degrees west of south.” That adjustment is due to changes in market prices that accompany significant growth in PV generation — changes that will occur in other regions as they start to ramp up their solar generation.

The researchers stress that conditions are constantly changing on power grids and electricity markets. With that in mind, they made their database and computer code openly available so that others can readily use them to calculate updated estimates of the net benefits of PV power and other distributed energy resources.

They also emphasize the importance of getting time-varying prices to all market participants and of adapting installation and dispatch strategies to changing power system conditions. A law set to take effect in California in 2020 will require all new homes to have solar panels. Installing the usual south-facing panels with uncurtailable output could further saturate the electricity market at times when other PV installations are already generating.

“If new rooftop arrays instead use west-facing panels that can be switched off during negative price times, it’s better for the whole system,” says Brown. “Rather than just adding more solar at times when the price is already low and the electricity mix is already clean, the new PV installations would displace expensive and dirty gas generators in the evening. Enabling that outcome is a win all around.”

Patrick Brown and this research were supported by a U.S. Department of Energy Office of Energy Efficiency and Renewable Energy (EERE) Postdoctoral Research Award through the EERE Solar Energy Technologies Office. The computer code and data repositories are available here and here .

This article appears in the  Spring 2020  issue of  Energy Futures, the magazine of the MIT Energy Initiative. 

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• Paper: “Shaping photovoltaic array output to align with changing wholesale electricity price profiles.”
• Paper: “Spatial and temporal variation in the value of solar power across United States electricity markets.”
• Report: “The Future of Solar Energy”
• Patrick Brown
• MIT Energy Initiative
• Energy Futures magazine

Related Topics

• MIT Sloan School of Management
• Climate change
• Photovoltaics
• Environment
• Sustainability
• Renewable energy

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Brief research report article, a research study to increase usage of pvs in residential areas.

• Energy Management Program, Vistula University, Warsaw, Poland

Self-generation of energy by residential houses has been met with many obstacles. When PV Solar energy technology is considered, the barriers manifest in problems related to the location, slope, strength, and shade exposure of house roofs are the most common. Therefore, it is not possible to meet daily energy needs from PV panels placed on the existing roofs of many houses. Solar Tracking Systems keep PV panels perpendicular to the Sun throughout the day, providing a significant increase in their efficiency. But the application of these systems on the roofs or houses is not suitable for many reasons, especially in terms of aesthetic appearance. This article is aimed at effectively showing how the slope and direction inconsistencies in the existing roofs of houses in residential areas cause great losses in the performance of PVs; also a research and design study is presented to find a solution to the application of Sun tracking systems in residential areas without creating aesthetic appearance problem. As a solution, combining a dual axis Sun tracking system with an aesthetic looking Gazebo has been considered. A design study was carried out for the targeted system, and the dimensions of a movable platform/roof such a system should have in order to meet the electricity needs of a house from the Sun throughout the year was investigated. How much energy the PV panels can collect annually is determined by a simulation program called “PV performance tool”.

Introduction

Extending the use of renewable energy sources can be considered a very important development towards a cleaner world, but an even better solution can only be achieved by obtaining energy from renewable energy sources while also consuming this same energy straight from the point of production. Because in this solution, many losses and problems associated with energy transmission and distribution lines can also be eliminated.

A significant part of energy consumption takes place in residential areas. In the evenings, especially, this consumption increases considerably ( Anderson et al., 2017 ; Validzic, 2017 ). The fact that people produce the electricity they need in their own homes as much as possible provides many benefits in terms of the energy network. Some of this benefits include reduction in the need for centrally-operated large power plants, increase in the usage of renewable energy sources, ease of the burden on energy transmission and distribution lines, and reduction in both losses and maintenance-breakdown expenses ( Zahedi, 2011 ). Efforts to increase these benefits also contribute to the protection of nature as well as a slow-down in the spate of global warming ( Panwar et al., 2011 ; Rabaia et al., 2021 ).

However, houses in residential areas face many obstacles in generating their own energy. When these obstacles are considered with focus on PV Solar energy, the most common problems that arise include the direction, slope, strength, and shadow exposure of house roofs ( Kouhestani et al., 2019 ). Likewise, some other similar problems are: the lack of sufficient space for the use of PV panels in the gardens, shadow problems, distortion of the aesthetic appearance of the gardens, or the PV panels creating anxiety in people due to electric phobia. However, even if all the mentioned problems are solved, deeper considerations of the total roof areas of the city residences reveals that the total that can be produced from roof-mounted solar PV will be insufficient to meet the energy needs of those cities even if all available roof areas are used ( Jurasz et al., 2020 ). In this case, attention must be pointed to solar energy systems that enable us to obtain higher performance from a limited area. Besides, studies in Active Building which have experienced significant developments in recent years also show the importance of this subject. One of the important targets of Active Building works is that a building should generate and manage all the energy it needs ( Bulut et al., 2016 ; Fosas et al., 2020 ; Strbac et al., 2020 ).

For houses that cannot meet the energy they need from the Sun, the increase in the performance of PVs depending on the developments in the material structure can produce an effective solution in the long term. For instance, it is hoped that the performance of PV panels can be doubled with GaNP-based photovoltaic device integrated on Si substrate ( Dvoretckaia et al., 2020 ). Similarly, it is hoped that the performance of solar cells can be increased to 42.5% with GaAsP/Si tandem technology. ( Kim et al., 2018 ). Or, due to the very cheap price of PVs, another solution may be placing the PV panels not only on the roofs but also on the walls and thus ignoring the losses due to unsuitable positions or shadow problems. For instance, it is hoped that the Perovskite solar cell technology will make PV prices considerably cheaper. ( Huckaba, 2016 ; Fagiolari and Bella, 2019 ).

However, in this study, a research has been made to produce a solution under today’s conditions and it is aimed to benefit from the performance increase of around 30% provided by Sun Tracking Systems (STS). There has been a lot of research for a long time into the performance improvement provided by STSs. For instance, Nadia AL-Rousan and her colleagues from University Sains Malaysia examined many Sun Tracking systems in their article named “Advances in solar photovoltaic tracking systems: A review” and showed that the efficiency gains of these systems compared to Fix position PV panels can vary between 20 and 50%. ( Nadia et al., 2018 ).

The most important roadblock to the use of STS on roofs is the problem of aesthetic appearance. In addition, if there is a shadow problem on a roof caused by adjacent buildings or trees, it will not be beneficial to use STS there. Within the scope of this study, which has been going on for several years, it was aimed to combine an STS with a Gazebo in an aesthetic fashion, and a single axes novel design STS-Gazebo system was presented at a conference in 2019 ( Kiray, 2019 ). The developed system was named as Rotating Roof Gazebo System (RRGS).

In this phase of the research, it was shown how effective the losses due to slope and direction on roofs and how large these losses are compared to the performance provided by STS systems. In addition, a design study was presented to prove that the aesthetic image problem can be solved by combining an STS with a Gazebo. The width of the mobile platform that will follow the Sun and the power of the PVs that can be placed on this platform were determined by the design study.

The performance calculations were made for the determined total PV power by using the “PV performance tool” offered by the science and information service on the European Commission’s website. Cities in Warsaw and Madrid were selected for performance tests and the data obtained were presented under a separate heading. RRGS performance, and whether this performance can meet the annual energy of a normal home, are discussed in the Discussion section.

In the literature study for the research and design study presented, it was first investigated whether the dual axis novel STS has similar electromechanical equivalents. Then, scientific studies that take solar energy systems or materials in an aesthetic concept have been examined.

A review of the literature reveals two studies that can be considered the closest to RRGS, which use the logic of creating Sun Tracking using a rotating platform. The first of these studies is seen in a Patent Application named “Rotating lattice solar tracking platform”. However, in this study, the use of a Gazebo was not considered, and a design was not made to eliminate the shadow problem that occurs when the Sun rays are not vertical, and its mechanical system is completely different from the RRGS ( Bill, 2010 ). The other close study involves single-axis solar tracking platforms placed on a very wide platform that rotates in a horizontal plane. This study differs from RRGS both in terms of its mechanical system and the fact that it does not use a single-piece platform ( Lim et al., 2020 ).

When the literature is examined, many scientific studies related to solar tracking systems were found to have been consucted ( Hafez et al., 2018a ; Hafez et al., 2018b ; Nsengiyumva et al., 2018 ; Singh et al., 2018 ; Awasthi et al., 2020 ), but since the RRGS has a novel design that combines a Gazebo with a Solar Tracking System, there is no similar study in the literature yet. However, since the Sun Tracking Logic is handled with an aesthetic understanding in RRGS design, the research and design study presented has gained a different dimension. When the literature is viewed from this point of view, the flower-looking Smart Flower design, which deals with the use of PV panels in an aesthetic manner, stands out ( Mulyana et al., 2018 ). Besides, the Tesla Roof, consisting of Solar tiles, can be considered as another design study that deals with the use of solar energy in an aesthetic outlook ( Choi et al., 2018 ; Hire et al., 2020 ).

Slope and Direction Problems Depending on the Structure and Position of the Roofs

It is very difficult to change the roofs of houses built years ago in favour of solar energy systems. However, depending on the slope (tilt) and direction (azimuth) of the roofs, significant changes occur in the performance of PV Solar Energy systems. The effect of tilt and azimuth factors can be understood from the formulas given below. Solar energy to be harvested from a PV panel is generally expressed in the following formula ( Suthar et al., 2013 ; Hailu and Fung, 2019 ).

The monthly average daily total radiation on a tilted surface (HT) is obtained from the direct beam (HB), diffuse (HD), and reflected components (HR) of the radiation on a tilted surface ( Suthar et al., 2013 ; Hailu and Fung, 2019 ).

Tilt and Azimuth factors are effective over (HB) in this formula.

where Hg, Hd, and Rb are the monthly mean daily global, the monthly mean daily diffuse radiation on a horizontal surface, and the ratio of the beam radiation on a tilted surface to that on a horizontal surface, respectively. Rb , the ratio of the beam radiation on the tilted surface to that on a horizontal surface.

where Φ is the latitude of location, β is PV module surface slope from horizontal called tilt angle, γ is the surface azimuth angle, w is the angle from the local solar noon called hour angle and δ is the declination angle ( Suthar et al., 2013 ; Hailu and Fung, 2019 ).

In addition, it is possible to see the effect of tilt and azimuth angles on the performance of PV panels by using various simulation programs. The simulation results of this research study are presented in Discussion Section. When the results are examined, it is seen that the slope and direction problems of the roofs have considerable impact on the performance of the PV Solar energy systems.

An Alternative Solution to Roofs in Term OF PV Panel Placement

For houses whose roofs are not suitable for the placement of PV panels, the use of gardens, if any, and the use of solar tracking systems for higher efficiency is the most practical solution that comes to mind. Gardens can be considered as more advantageous areas than roofs for the deployment of PV panels. However, the lack of sufficient space in the gardens, the disruption of the garden aesthetics by fixed PV panels or solar tracking systems and the concerns of people with electric shock phobia also constitute different problems.

The fact that Solar Photovoltaics (PV) show the sharpest cost decline over 2010–2019 at 82% also reduces the attractiveness of solar tracking systems (Irena Report, 2019) 1 . However, in today’s conditions, solar tracking systems maintain their importance for situations where high performance from a limited area is aimed. However, solar tracking systems are not aesthetically suitable either for roofs or for gardens. The use of solar energy in a certain aesthetic level in residential areas is an issue that maintains a high degree of importance. Smart flower design ( Hafez et al., 2018a ) and Tesla roof also support the studies in this concept ( Mulyana et al., 2018 ; Hire et al., 2020 ).

Considering all these, it was thought that converting a Gazebo into an STS can minimize the mentioned problems. Within the scope of the research, a single axis STS was obtained by rotating the roof of the gazebo in the first plan and a real-size prototype application was realized. Two important problems were identified in this application ( Kiray, 2019 ). First, the roof material creates a significant weight and the motors selected to rotate the roof had to have high power and thus high energy consumption. Second, because only the sun-facing side of the roof is used and the roof angle is constant, there is a significant performance loss. In this research phase, it was thought that the roof would be completely canceled, a wide-area platform following the Sun would be used instead of the roof, and the loss of aesthetic appearance would be minimized with a symmetrical system. In addition, again in relation to the aesthetic appearance, the body structure of the Gazebo was prepared in a structure like a cylinder.

Electro-Mechanic Structure of RRGS

Unlike other STSs, the RRGS is designed by using a second platform that makes angular motion on the vertical plane on a main platform that makes circular rotation on the horizontal plane.

The main platform is supported by three carriers connected to each other with iron profiles ( Figure 1A ). The platform moves on a disc placed on top of side walls of the Gazebo. The platform is rotated with motors placed at the end points instead of rotating from the center ( Figure 1B ), but thanks to the unique design, the platform makes a circular rotation movement as if it is rotated from the center point ( Figure 1C ). While the main wheels of the carriers move on the disc, the other wheels of the carriers also move under the disc and on the side wall of the disc to prevent the platform from tipping or shaking in windy weather ( Figure 1B ).

FIGURE 1 . Electro-mechanic structure of RRGS. (A) Disc and Movable triangular carrier. (B) Disc and one of the carrier’s motor. (C) Main platform on moving carrier. (D) Main and Second platform.

Movement on the vertical plane is provided by the angular movement of the platform carrying the PV panels. Therefore, when the whole system is considered, a unique dual-axis Solar tracking system is obtained ( Figure 1D ).

In the framework of this research presented, two design studies were made for the optimal placement of the second platform on the RRGS. In the first design, it was thought that the platform, which should be perpendicular to the Sun, should be divided into two parts in order not to spoil the aesthetic appearance of the system and not be affected by the wind, but it was seen that there would be a huge loss of efficiency in the calculations. Because, in the case of using platforms consisting of two rows, a large gap must be left in order not to affect the rear platform from the shadow created by the front platform ( Figure 2A ). Therefore, this design option was not chosen.

FIGURE 2 . Two different design studies of RRGS. (A) First design with low efficiency. (B) Second design with high efficiency.

In the second design study, the platform moving in a vertical plane is designed as a single piece ( Figure 2B ). It was thought that this platform could be larger than the platform that rotates in the horizontal plane to make the area where the PV panels will be placed as wide as possible. In this design, three important problems were encountered: Aesthetic appearance, Wind effect, and the necessity of a special electromechanical system. At this study some changes have been made to the design to minimize these problems.

Aesthetic appearance: To partially restore the roof image that our eyes are accustomed to, a back platform made of light material, which will create symmetry to the mentioned platform, is added to the design. In addition, the symmetrical image is strengthened with the two arms extending from the rear platform.

Wind Effect: To reduce the wind effect, it is used not only to create symmetry from the rear platform, but also to increase its mechanical stability. In addition, it is thought that the position of the platform in windy weather could be adjusted to a zone with the least wind effect with the aid of a wind sensor.

Electromechanical system: Depending on the problems in question, a special Electromechanical system was added to the design: In the developed design, both platforms are articulated at their lower ends. The rear platform with two arms has channels in these arms. While the main platform arranges its position to the Sun, the protrusions of the front (main) platform moving in these channels allow the rear platform to move symmetrically ( Figure 2B ).

Both platforms are articulated at their lower ends. The rear platform has two arms each of which has channels. The protrusions of the front platform moving in these channels allow the rear platform to move symmetrically ( Figure 2 ). In addition to creating an aesthetic appearance, the rear platform also contributes to the strengthening of the system and to the reduction of negative wind effect.

The electro-mechanical system design presented in this study is modelled quite realistically as it was based on a previously made prototype study.

Sizes of Platforms

The Gazebo, whose structure resembles a cylinder, has a diameter of 4 m. The platform, which rotates in the horizontal plane and completely covers the top of the gazebo and protects it from rain, is set to 5 m in diameter and an area of approximately 20 m 2 is obtained. The area of the platform following the Sun is expanded a little more and determined as 23.66 m 2 . It is not possible to cover the entire area with PV panels because PV panels come in fixed dimensions predetermined by the manufacturer.

Types of the PV’s and Optimal Placement of the PV Panels

Half-cut cell PV module technology is a good alternative for RRGS, as the RRGS aims to get high performance from limited space.

Half-cut cell PV module technology makes it possible to harvest more energy from the same area ( Akram et al., 2020 ). It seems possible to obtain 250 Wp energy from one m2 with commodified products that are produced using this technology existing as of 2021 ( www.Cleanenergyreviews.info/ ). For this reason, it is decided to use PV panels with 78 cells (156 HC) with dimensions of 2.2 m × 1.1 m for RRGS. The average peak power (Wp) of these panels varies between 450 and 600 Wp. So, it seems possible to obtain an average power of 2,700–3600 Wp by placing six high-performance PV panels with a power of 450–600 Wp and dimensions of 2.2 m × 1.1 m in this area. ( Figure 3 ). Under ideal conditions, it seems possible to obtain 5,750 Wp energy from an area of 23 m 2 , but depending on the standard PV panel sizes, the usable active area is limited to 14.52 m 2 and so, the average total peak power is limited to 3,300 Wp.

FIGURE 3 . Placement of PV panels on the platform.

The PV Performance Tool and Simulation Results

The “PV performance tool” offered by The European Commission’s science and knowledge service on its website ( https://re.jrc.ec.europa.eu/pvg_tools/ ) is used in the performance calculations of RRGS.

“PV performance tool” is a simulation program that calculates the monthly and annual possible energy harvest performance of fixed position PVs or those PVs mounted on single axis/dual axis STS. The location where the PVs will be deployed is determined on the map. The energy harvest performance of PVs placed on the roof of a house can be simulated by entering Slope and Azimuth angle values for fixed position panels.

The total power of the PVs placed on the RRGS is specified as 3,300 Wp. Since RRGS has a dual-axis STS feature, simulation results are first obtained for a 3,300 Wp STS. The performance of this value is accepted %100.

The “PV performance tool” program also takes into account the PV module efficiency in the calculations. Accordingly, the efficiency loss for PV modules was determined to be 14%. The factors taken into account in efficiency calculations and the formulas used are presented in the documentation section of the relevant website ( ec.europa.eu/.../methodes ).

At first glance, the values obtained with the PV performance tool can be perceived as comparing Fixed PVs with PVs placed on STS. However, the 3,300 Wp power value obtained was obtained at the end of a design study. The performance values given in Table 1 show how the performance decreases as the unconformity increases and the importance of the RRGS increases for the houses with slope and direction problems on their roofs.

The simulation program used can calculate the optimal slope and Azimuth values. According to these values, even if the slope and Azimuth angles of the roof of a house in Warsaw are at the optimum level and the power of the PV panels installed on it is equal to the total power of the panels above RRGS, its performance will be on average 27% lower than the performance of the RRGS. In similar manner, if a comparison is made for Madrid, the estimated performance loss would be 32%. However, it is very unlikely that the slope and azimuth angles on the roof of a house built years ago are at an optimal level.

To see more realistic results, if the roof slopes of the house in question are assumed to be 20 degrees different in both cities, there is a possible loss of efficiency of 30% in the house in Warsaw and 34% in the house in Madrid. If there is a small deflection of 30 degrees in the direction of the roofs, not in the slopes of the roof, 35% loss occurs in Warsaw and 39% in Madrid. If there is a 20-degree slope deflection and a 30-degree deflection in the direction on the roof, this time there is a 40% loss of efficiency in the house in Warsaw and 42% in the house in Madrid.

An exaggerated scenario has been added to the simulations to show the losses caused by the slope and direction problems of the roofs more effectively. Although this scenario did not make much change in the slopes of the roof, it was assumed that the direction of the house was facing east or west rather than south. In this case, it has been shown that the efficiency can fall below 50%.

Is the Performance Achieved Sufficient?

When the annual energy amount of 7,515 kWh obtained for Madrid is divided into 356 days in a rough calculation, it is seen that daily energy of 20.58 kWh can be obtained. This amount obtained shows that a house with a daily energy need of 15 kWh can be met all year round with a small battery bank supplement. For countries that have a good energy infrastructure and can buy all the energy produced by the end user, the need for a battery bank can be eliminated by using grid energy when needed and then making an offset. Even with a 3,300 Wp PV power RRGS, it may be possible to earn income from energy sales.

If the same calculation is made for Warsaw, it is seen that an average of 12.21 kWh of energy can be obtained per day. From a rough calculation, 80% of 15 kWh daily energy need of a house can be met.

Rough Economic Analysis

The economic analysis of the RRGS will be discussed in the next study. However, the following can be said to give a general idea.

Since the Gazebo part of the RRGS will also be used as a Gazebo, there is no need for the gazebo cost to be included in the economic analysis. However, a significant modification is needed to make the upper part of the gazebo follow the Sun, and the cost of this modification can be assumed to be equal to the cost of a dual-axis STS.

In this case, the cost of PV panels, on-grid inverter/Charger cost (new generation inverters include MPPT function), dual-axis STS cost and 20% miscellaneous expenses cost can roughly determine the overall cost of the system. In the market research conducted within the scope of this idea, the cost of PV panels is 1,200 USD (hot-china-products/PV), 3.3 kWp invertor/charger cost 2,000 USD (hot-china-products/Inverter) and Dual-axis STS price 3,300 USD (hot-china-products/tracker) and in this case, the total investment cost of the system is 5,500 USD and the total investment cost of the system can be considered as 6,600 USD, together with the cost of miscellaneous expenses of 20%.

The price of electricity for 2020 in Poland is seen as 0.199 USD and for Spain as 0.244 USD ( www.globalpetrolprices.com ). If it is assumed that all the electricity produced is purchased by the state, the annual production of 4,450 kWh in Poland saves 885.55 USD and the RRGS itself is amortized in 7.45 years. Likewise, in Spain, annual electricity production of 7,515 kWh saves 1833.66 USD and RRGS amortizes itself in 3.59 years.

Why Gazebo?

First of all, Gazebos are aesthetic and useful structures that add beauty to gardens. Gazebos can be turned into a STS with a special electro-mechanic system design on the roof parts. Thus, the Novel system obtained can be used both as a Gazebo and as an STS. And Because Gazebos can be moved to the desired location of the gardens, the shadow problems can be minimized.

The direct use of STSs on roofs or in gardens is not aesthetically appropriate, but it seems possible to overcome this problem with an STS integrated into a Gazebo. The fact that the PVs are mounted on the gazebo offers a distinct advantage for those with electric phobia besides the advantage of aesthetic appearance.

Author’s Note

VK received his Ph.D. degree from the Electrical and Electronics Engineering department of the Institute of Science, Sakarya University, Turkey 2003. He completed his Post-doctoral experience in the Technopark research office of Hochschule fur Technik, Zurich, 2006. His current research interests include Renewables, Smart Grid, Micro-Grid, and energy management systems. He has got also experiences and publications on FPGA-based Digital Design. He has been on the executive board of IEEE-ICECCO conferences since 2013. He is currently working as a researcher and academic staff at the Vistula University, Energy Management program, Warsaw, Poland.

Data Availability Statement

The raw data supporting the conclusion of this article will be made available by the author, without undue reservation.

Author Contributions

The author confirms being the sole contributor of this work and has approved it for publication.

Conflict of Interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Supplementary Material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fenrg.2021.680304/full#supplementary-material

https://www.irena.org/publications/2020/Jun/Renewable-Power-Costs-in-2019 (Visited at 08/04/2021, 10:55) https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP (Visited at 08/04/2021, 10:57) https://www.cleanenergyreviews.info/blog/most-efficient-solar-panels (Visited at 08/04/2021, 10:57) https://ec.europa.eu/jrc/en/PVGIS/docs/methods (Visited at 16/05/2021, 10:50) https://www.globalpetrolprices.com/Spain/electricity_prices/ (Visited at 16/05/2021, 10:53) https://www.made-in-china.com/products-search/hot-china-products/Solar_Panel.html?gclid=EAIaIQobChMI4-r8nfrO8AIVVgWRCh2MNAGbEAAYAyAAEgLCofD_BwE (Visited at 16/05/2021, 10:57) https://www.made-in-china.com/productdirectory.do?word=power+inverter+charger&file=&subaction=hunt&style=b&mode=and&code=0&comProvince=nolimit&order=0&isOpenCorrection=1 (Visited at 16/05/2021, 11:11) https://www.made-in-china.com/productdirectory.do?word=dual+axis+tracking&file=&subaction=hunt&style=b&mode=and&code=0&comProvince=nolimit&order=0&isOpenCorrection=1&log_from=1 (Visited at 16/05/2021, 11:23).

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Keywords: solar energy, PV, sun tracking system, active building, energy efficiency

Citation: Kiray V (2021) A Research Study to Increase Usage of PVs in Residential Areas. Front. Energy Res. 9:680304. doi: 10.3389/fenrg.2021.680304

Received: 14 March 2021; Accepted: 21 May 2021; Published: 10 June 2021.

Reviewed by:

Copyright © 2021 Kiray. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Vedat Kiray, [email protected]

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Germany’s Solar Panel Industry, Once a Leader, Is Getting Squeezed

Domestic manufacturers are caught between China’s low prices and U.S. protectionist policies, even as demand increases.

By Melissa Eddy

Reporting from Berlin

Before China came to dominate the solar panel industry, Germany led the way. It was the world’s largest producer of solar panels, with several start-ups clustered in the former East Germany, until about a decade ago when China ramped up production and undercut just about everyone on price.

Now as Germany and the rest of Europe try to reach ambitious goals to cut greenhouse gas emissions, the demand for solar panels has only increased.

Some of the last remaining manufacturers in Germany’s solar industry are not ready to give up.

They are demanding that the government in Berlin offer incentives to protect producers that have survived by catering to niche markets and expanding beyond making panels. They argue that Europe’s high standards for the origin of materials and shorter supply chains make production in Germany more environmentally friendly and reliable.

Not everyone is convinced protectionism is the way to go. Some critics note that the European Union’s tariffs on Chinese solar panels from 2013 to 2018 failed to save the domestic industry. Others argue that affordable, widely available solar panels are desperately needed regardless of their origin.

Because Europe relies “to a very important degree” on imported solar panels, any measure to restrict imports “needs to be weighed against the objectives we have set ourselves when it comes to the energy transition,” Mairead McGuinness, the European commissioner for financial stability, told the European Parliament last month.

But for European solar manufacturers, the problem has gotten worse in the past year. Not only have the Chinese increased their production of solar panels, but the United States tightened its tariffs to include Chinese panels shipped to Southeast Asian countries for final assembly. That has caused a flood of Chinese panels to reach Europe at below-market prices, government officials and company executives say, crushing any chance at fair competition.

Last year, more than 97 percent of the solar panels installed on roofs and in fields across Europe were made abroad, the vast majority in China, where cheap energy and government support keep prices low.

“Chinese competitors are currently giving away their products in unimaginable quantities in Europe at far below their own production costs,” said an open letter to the government written by Gunter Erfurt, the chief executive of Meyer Burger, a Swiss solar energy company that has two factories and a research center in Germany.

“We are fighting for fair market conditions, which have not existed for just under a year,” Mr. Erfurt wrote.

Mr. Erfurt’s appeal cited several other German companies involved in solar production that all want the government to help shore up the industry in the face of the fierce competition from China.

The German Solar Association is calling on the government to push through a proposed incentive, called a “resilience bonus,” that would pay solar panel owners a higher rate for electricity that is fed into the grid from domestically produced panels.

“While other countries such as the United States and China are strongly promoting the establishment and scaling up of solar gigafactories, the German government has yet to take concrete action,” the group warned in January.

To meet its ambitious climate goals, Germany needs to generate an additional 80 gigawatts of solar power annually. But last year, the country installed enough to generate just 9 gigawatts — and domestic photovoltaic companies say they have the capacity to produce only about 1 gigawatt of solar power per year.

That reality has led to a bitter dispute within the German solar industry, where some believe subsidies will do more harm than good.

Philipp Schröder, a former Tesla executive who runs 1Komma5, a solar company he co-founded, said it got its components mainly from Europe and the United States and successfully competed against low-cost Chinese panels by bundling panels with heat pumps, batteries and software to run the complete system. He is against any form of government support.

“The resilience bonus being discussed in Germany right now might be beneficial for a few profiteers in the short term, but in the medium term it acts like an addictive drug that suppresses innovation and fragments the E.U. market,” Mr. Schröder said in a post on LinkedIn.

This month, Meyer Burger deepened the dispute when it halted production at a facility in Freiberg in the eastern German state of Saxony and said it would shift the company’s focus to expanding production in Arizona and Colorado. There, it can take advantage of U.S. tariffs imposed on Chinese panels and incentives offered through the U.S. Inflation Reduction Act.

“Due to a lack of European protection against unfair competition from China, nearly four years of hard work by great employees in Europe is at risk,” the board of Sentis Capital Cell 3 PC, the largest shareholder in Meyer Burger, said in a statement. In a slap at German lawmakers, the board cited “strong bipartisan commitment” in Washington “to protect U.S.-based companies against unfair competition.”

Further stoking anger in the solar industry are the billions in subsidies that the government has pledged to attract other companies, including the battery producer Northvolt and the microchip manufacturers Intel and TSMC, as it appears stymied over the question of how to handle solar.

Sven Giegold, an under secretary in the Economy Ministry, told reporters this month that Germany would propose measures to help “support the local production of solar technology,” but quickly added: “Trade defense measures are not helpful.”

Germany has been here before. In the early 2000s, a combination of government incentives, scientific research and cutting-edge technology helped make its solar industry the world’s leading producer of photovoltaic panels and technology.

Then manufacturers from abroad, especially China, caught on and sold solar panels at prices well below what the Germans were offering. The impact was swift and brutal. Companies such as Q-Cells, Solon and SolarWorld declared bankruptcy and disappeared. But some businesses held on by focusing on assembling, installing and integrating solar panels in comprehensive green power systems.

Simone Tagliapietra, a senior fellow at Bruegel, the Brussels-based think tank, said he agreed that new tariffs would not make sense. To achieve a secure supply of panels, as well as support the green transition and economic growth, he suggested that Europe instead support development of new solar technologies.

“Go for the new generation of solar panels, products that are still at the forefront of innovation,” Mr. Tagliapietra said. “If we cannot beat the Chinese on quantity, we need to try to beat them on quality.”

Solarwatt, based in the former East Germany, said it might also have to close one of its solar panel plants. But making panels is only one part of the company; it also creates systems that connect the power generated by solar panels to wall boxes that can charge cars and heat pumps to warm homes.

“The future of our company is not a risk, even if production had to be shut down,” the company said in a statement, adding that other divisions could absorb the roughly 120 people whose jobs would be at stake.

Meyer Burger’s decision to shut its plant in Freiberg has left as many as 500 jobs in limbo. The company’s chief executive, Mr. Erfurt, said the factory’s future depended on political leaders in Berlin. “But we don’t see a bridge being built from the government at the moment,” he said.

At the same time, the company is contemplating other alternatives, he said, adding that “one option is simply to dismantle and rebuild it in U.S.”

Melissa Eddy is based in Berlin and reports on Germany’s politics, businesses and its economy. More about Melissa Eddy

Scientists use powerful supercomputer to enhance efficiency of solar technology: 'A different way to go'

S cientists around the world are working on ways to make solar cells — the technology that captures energy from the sun and converts it into electricity — work more efficiently in an attempt to hasten the transition away from dirty, polluting energy sources such as gas and oil. 

Now, researchers in Germany ha ve used a powerful supercomputer to design a new way of improving efficiency.

Professor Wolf Gero Schmidt and postdoctoral researcher Dr. Marvin Krenz, of the University of Paderborn, used the High Performance Computing Center Stuttgart's Hawk supercomputer to simulate how excitons — bound pairings of an electron and an electron hole — could be controlled and moved within solar cells. In the process, they discovered that certain defects strategically inserted into the system could improve efficiency.

"Exciton transfers are ubiquitous and extremely important processes, but often poorly understood," the scientists wrote in the abstract of their study , published in Physical Review Letters . "Dangling bonds, intuitively expected to hinder the exciton transfer, actually foster it. This suggests that defects and structural imperfections at interfaces may be exploited for excitation transfer."

From there, Schmidt, Krenz, and their team focused on designing solar cells with a molecule-thin layer of tetracene, an organic semiconductor material, to help capture some of the excess energy that the commonly used silicon cannot.

While much of the research around maximizing efficiency in solar cells focuses on combining silicon with perovskite, dubbed a " miracle material " for solar energy capture, the research from the University of Paderborn team shows that there may be more than one way to skin a cat.

Watch now: Alex Honnold test drives his new Rivian

"Our paper might be interesting for the larger research community because it points out a different way to go when it comes to designing these systems," Krenz said .

However the next most efficient solar cell is designed, more research from scientists can only be a good thing, as each new discovery builds on the previous one. 

For people who install rooftop solar panels , more efficient panels would mean that they could harvest more clean, renewable energy themselves and rely less on the dirty energy from gas and oil provided by power companies — reducing energy bills in the long run and helping the planet at the same time.

Scientists use powerful supercomputer to enhance efficiency of solar technology: 'A different way to go' first appeared on The Cool Down .