St Lawrence College Project

The goal was to facilitate the comparison of snow-shedding rates between tilt angles and study the bifacial advantage.

Photo(s): provided by Sustainable Energy Applied research Centre – St. Lawrence College.

Location: Kingston, Ontario

Type of installation: Roof installation.

What type of modules were used: SLA-X 270

PROPOSAL

The test proposed to install 12 panels each to be installed at three different angles – 20°, 30° and 40°. The goal was to facilitate the comparison of snow-shedding rates between tilt angles for different panel types.

The 20° tilt array was southernmost on the roof, the 30° tilt array was set 3.5 metres back from the 20°, and the 40° tilt array was set 7 metres back from the 30°. Efforts were made to minimize the impact of direct inter-row shading. For the higher-profile landscape-mounted 20° panels, their installation was at the far west of the row, with no test modules directly behind them. Similarly, the higher-profile landscape- mounted 30° panels were mounted at the far east of the row, with no test modules directly behind them.

The test proposed to mount half of the modules at each tilt angle to be mounted in portrait with the other half mounted in landscape.  The variables mounting orientations was to determine if panel orientation played any noticeable role in accelerated snow-shedding.

SUMMARY

The entire research took approximately 10 months.  They installed 22 PV modules to determine the degree of real-world snow-shedding performance.

Each panel was connected to a dedicated channel on an APSystems YC-1000 micro-inverter. The test array was also monitored remotely via two pole-mounted web-enabled cameras . Still images were recorded every twenty seconds and saved to a secure drive on the St. Lawrence College server. These images were to be used to identify and highlight snow-shedding behaviour of the modules.

The study finds that bifacial panels do shed snow more  quickly and that the greatest potential for bifacial gain related to snow-shedding comes at low tilt angles of between twenty and thirty degrees.

Additionally, the study finds that the bifacial gains from the panels tested are greatest, in all conditions, when the full bifaciality factor – that is, the power output of the rear side of a bifacial cell, shown as a ratio of its front side – of the cell is evidenced in the rear-side flash-test rating. 

 

THE RESULTS

During the summer months, for which the data collected is most reliable, a minimum bifacial gain of 10% is seen at the 20° tilt angle for the framed bifacial panels. The winter period’s relative bifacial gains gradually increase, with the two highest relative gains coming during the solar year’s typically worst period overall (Dec. 2016 and Jan.-Feb. 2017). Bifacial gain is slightly less at the 30° tilt angle. Bifacial gain is higher from the frameless panels than the framed typed.

Overall the study’s bifacial panels overall performed better than their monofacial counterparts throughout the year, at all tilt angles. The higher albedo factor of snowfall accumulation underneath the panels can be considered the primary driver of an increasing rate of bifacial gain from December through mid-February.  

The study also found that there is no appreciable negative impact on the performance of bifacial panels mounted conventionally with rail running behind the rear side of the panel.  Secondly, PV panels capable of self-shedding of major snowfall accumulations at low tilt angles should offer a greater energy production in winter than standard modules in locations with high snowfall patterns. The bifacial panels tested in this study shed snow at a 20° tilt angle faster than monofacial panels shed snow at 40°, and showed lower snow-related production losses at all angles than monofacial panels in the same conditions.

OBSERVATIONS 

10% Higher Specific Yield from Bifacial Panels is a reasonable expectation even on unfavourable conditions.  

In general, even given the unfavourable conditions, the bifacial panels tested in this study performed at least 10% better than the baseline monofacial panels in the study at a 20° tilt angle, and at least 9.5% better at a 30° tilt angle. It is reasonable to present these values as conservative representations of the potential of the technology in the field, given the overall unfavourable installation conditions for bifacial panels at the test site.

Snow sheds appreciably quicker from bifacial panels, particularly at lower tilt angles.

PV panels capable of self-shedding of major snowfall accumulations at low tilt angles should offer a greater energy production in winter than standard modules in locations with high snowfall patterns. The bifacial panels tested in this study shed snow at a 20° tilt angle faster than monofacial panels shed snow at 40°, and showed lower snow-related production losses at all angles than monofacial panels in the same conditions. Kingston during the winter period of this study was not particularly snowy, but locations with more frequent snowfall events could expect to see greater increases in production related to snow- 24 shedding. Moreover, the potential for a reduced cost and risk frequency for snow removal maintenance may be more valuable than the actual amount of energy gained.

Snow covered ground area is better for bifacial panels.

Losses to snowfall can be turned to gains from snowfall in locations where snowfall accumulates and remains under bifacial panels. This study showed 18-25% bifacial gains at a 20° tilt angle over monofacial panels during a typically-snowy winter period, in a location that is not notably snowy in the Canadian context, on a rooftop that was less snowy than the surrounding ground.

Conventional mounting methods are acceptable for bifacial panels.

If bifacial panels are suitable for conventional mounting – i.e. if they have a frame – they can be installed in the same manner as conventional monofacial panels without concern for loss of potential bifacial gain.

Bifacial gain is higher year-round when panel design avoids cell shading.

From the panels installed at a 20° tilt angle, bifacial gains averaged 14% over the course of the study period from panels that did not have a junction box shading the cells on the rear side. If this design feature could be combined with the mounting advantage offered by a framed panel, it would presumably be a more marketable product.

INTERVIEW 

The bifacial panels tested in this study performed at least 10% better than the baseline monofacial panels in the study at a 20° tilt angle, and at least 9.5% better at a 30° tilt angle.

PV panels capable of self-shedding of major snowfall accumulations at low tilt angles should offer a greater energy production in winter than standard modules in locations with high snowfall patterns. The bifacial panels tested in this study shed snow at a 20° tilt angle faster than monofacial panels shed snow at 40°, and showed lower snow-related production losses at all angles than monofacial panels in the same conditions.

If bifacial panels are suitable for conventional mounting – i.e. if they have a frame – they can be installed in the same manner as conventional monofacial panels without concern for loss of potential bifacial gain.

ABOUT SILFAB BIFACIAL

Our ultra-high-efficiency bifacial modules are optimized with premium N-Type bifacial cells up to 21.5% front efficiency (22.7% module efficiency with up to 30% back side contribution). Designed to be architecturally distinct and delivering low-degradation and maximum power density.

Learn more about our Bifacial Products> 

Silfab Solar is the North American manufacturing leader in the development of ultra-high efficient and premium quality 60 and 72 cell monocrystalline PV modules. Located in Toronto, Ontario, Canada, Silfab Solar leverages over 35 years solar experience. As the largest  and most advance manufacturer in North America, Silfab’s fully automated facility utilizes precision engineering  to produce superior reliability and performance with the lowest defect rate in US.

The SLA series is Silfab’s most Powerful, and durable module. Silfab’s Bifacial is ideal for installations where maximum output is required.

ABOUT APPLIED RESEARCH

SEARC’s mission is to provide applied research services to small and medium-sized enterprises in the renewable energy industry within the Eastern Ontario region. Research activities such as new product development, product improvement, prototype development, field testing, process improvement and commercialization of new products are within the scope of our work at SEARC. The research centre leverages the resources of St. Lawrence College: faculties, staff, students and equipments to assist SMEs to become more profitable.

Over the long term, SEARC aims to increase the economic development of the Eastern Ontario region and create new quality jobs based on know-how and technological innovation. This will be achieved by increasing the capacity of St. Lawrence College to transform the results of research and development (R&D) into economic activities easier and faster.

This project was made possible by Sustainable Energy Applied Research Center, the Government of Ontario, through Ontario Centres of Excellence (OCE)  and the Natural Sciences and Engineering Research Council of Canada (NSERC).