Department of Energy awards funds to large-scale DNV GL study of bifacial solar module performance

mission solar

Bifacial PV modules have the potential to increase energy output by 5-10 percent annually in many locations. To achieve commercial viability, the products need to demonstrate their bankability. Common testing models, have begun to incorporate bifacial models. However currently only little validation data for bifacial PV modules exists, which also often lacks third-party evaluation. This is why the U.S. Department of Energy (DoE) Solar Energy Technologies Office (SETO) is awarding DNV GL, the world’s largest resource of independent energy experts and certification body, $200,000 for a research study of bifacial PV technology. The project will validate energy models created for bifacial PV modules by commissioning a large-scale comparative energy yield analysis and creation of energy simulations in PVsyst software, based on the collected field data.

“This study represents the most comprehensive comparative energy yield analysis for bifacial PV modules to date,” said Richard S. Barnes, Executive Vice President, DNV GL – Energy, North America. “Because the solar industry is projected to grow rapidly, it is necessary to understand how new technologies, like bifacial PV modules, will perform.”

“The aim of the study is to accelerate commercial deployment of bifacial PV modules at scale,” said Tara Doyle, head of business development for DNV GL’s PV module testing lab. “If proven viable through extensive performance and reliability testing, bifacial PV modules have the potential to become the preferred technology for ground-mounted PV installations around the world.”

RELATED: Bifacial Gains: How much will bifacial modules add to solar tracker value? We are about to find out

Methodology

The project will entail collection of field data over the course of one year at DNV GL’s outdoor solar test facility in Davis, California. It will include bifacial and monofacial 1500 V PV modules provided by LONGi Solar, Astronergy Solar, Hanwha Q CELLS and Trina Solar, tested on single-axis trackers provided by solar tracking company NEXTracker, and two albedo ground types. Data acquisition will be highly granular, using actively calibrated equipment. The collected measurements will be used to generate PAN files and subsequent energy simulations in PVsyst.

The validation study was awarded as part of the U.S. Department of Energy’s allocation of $27.7 million for photovoltaics research and development, issued in conjunction with $25.1 million to projects that address other aspects of solar development. Along with other awarded projects that address bifacial PV technology, this study aims to accelerate the commercial adoption of reliable, high-performance PV systems by providing comprehensive field data, data analysis, and PVsyst models that will validate the relevant work that has been done to date.

“Energy modelling validation for bifacial PV modules and systems is needed to provide assurance to owners and financiers that PV systems using this technology will yield expected energy gains,” said Frank Faller, vice president, technology at 8Minutenergy, one of the largest utility scale developers in the U.S. “DNV GL Labs’ study is an important step toward addressing the lack of commercially representative, high-quality field data that’s required to validate contemporary energy models and thus accelerate the bankability of this technology.”

DNV GL was selected as a part of the Energy Department’s FY2018 SETO funding program, an effort to invest in new projects that will lower solar electricity costs and support a growing solar workforce. DNV GL is one of several photovoltaics research projects that will focus on improving the performance and reliability of PV cells, modules, and systems and reducing materials and processing costs.

— Solar Builder magazine

Canadian Solar ships 10 MW of its new bifacial solar modules to Neighborhood Power

Canadian Solar BiHiKu

Canadian Solar Inc. has delivered 10 MW of its bifacial PV modules, the BiKu CS3U-PB-AG that made its debut at Solar Power International in Anaheim this year, to Neighborhood Power for four solar power projects near Portland, Ore. This represents the first significant delivery of bifacial solar PV modules into the United States.

Bifacial solar modules can generate energy not only from the front side, but from the back side as well. With Canadian Solar’s Biku bifacial modules, the sunlight on the ground is reflected to the glass-covered back side of the module, producing extra solar energy in a solar system, significantly reducing the solar system’s levelized cost of electricity (LCOE), hence higher return on investment (ROI). Depending on the albedo (reflectivity) of the ground and other site conditions, daily energy yield for projects with bifacial modules can be 5-20% higher than with conventional polymer backsheet modules. This improved yield can dramatically enhance the economics of solar system deployments.

Canadian Solar is a leader in bifacial polycrystalline PERC (passivated emitter and rear contact) solar technology. By innovatively integrating bifacial and Ku (dual cell) technologies, the BiKu module can reach up to 370W on the front side, using poly PERC in a 144 cell format. Canadian Solar’s bifacial module comes with a 30mm frame for easy handling, saving significant installation costs.

RELATED: Bifacial Gains: How much will bifacial modules add to solar tracker value? We are about to find out

Neighborhood Power chose Canadian Solar bifacial modules because the additional energy gain is significant enough to compensate for the new tariffs on solar modules and steel mounting equipment, and the extra power gain made their solar projects economical again.

“When the solar industry was hit with tariffs on solar modules and steel, it seemed that rising landed costs had priced these projects out of the market,” said Stephen Gates, President, Neighborhood Power Corporation. “But with the additional power generated by Canadian Solar’s bifacial modules, delivered in the quantities and in the timeframe we needed, we were able to make the project economics work and bring these projects online by the end of 2018 as planned.”

Canadian Solar BiKu bifacial modules are warranted for 30 years, 5 years longer than the industry standard, and have a lower degradation rate, which results in 20% additional yield over the lifetime of the solar module. When added to the additional daily bifacial yield of 5-20%, Canadian Solar BiKu bifacial modules deliver up to 44% additional lifetime value compared to conventional modules.

“Canadian Solar foresaw early on that bifacial technology had the potential to be a game changer in the economics of large-scale solar and set out to be a leader in the development and deployment of bifacial solar modules. Our early deployment with Neighborhood Power in the U.S. is one proof point of our successful execution on that strategy,” said Dr. Shawn Qu, Chairman and Chief Executive Officer of Canadian Solar. “All together, Canadian Solar has delivered and deployed over 200 MW of bifacial solar modules for customers and our own solar projects around the world. We pledge to continue innovating and delivering on the breakthrough products and services that will soon make solar PV the most cost-effective source of power generation everywhere.”

— Solar Builder magazine

NREL argues for value of ‘watts per kilogram’ in emerging thin-film, flexible solar technology

NREL lightweight CIGS

This lightweight CIGS photovoltaic cell, on flexible stainless steel, was made by Matthew Reese and his team at NREL. Photo by Dennis Schroeder / NREL

Rigid silicon solar panels dominate the utility and residential markets, but opportunity exists for thin-film photovoltaic and emerging technologies notable for being lightweight and flexible, according to scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).

Thin films such as cadmium telluride (CdTe) and copper indium gallium selenide (CIGS), along with perovskites and other new technologies, could be ideal for generating the electricity needed for unmanned drones, portable chargers, and building facades. The opportunities and challenges inherent in widespread adoption of these ideas appear in the new Nature Energy paper, “Increasing Markets and Decreasing Package Weight for High Specific Power Photovoltaics.

“We explore the limits behind power-to-weight ratios and how this can generate value for emerging players in photovoltaics to enable them to reach gigawatt scale without having to directly compete with silicon solar panels,” said Matthew Reese, an NREL researcher and lead author of the paper. The paper was co-authored by Stephen Glynn, Michael Kempe, Deborah McGott, Matthew Dabney, Teresa Barnes, Samuel Booth, David Feldman, and Nancy Haegel, all from NREL.

The market opportunity

Silicon panels constitute 95 percent of the global solar market, generating electricity for utilities, residences, and businesses, but the researchers identified applications that must consider value propositions beyond the standard value triad of cost, efficiency, and reliability used for conventional photovoltaic (PV) panels. Flexibility and portability will be important factors, with the performance of the technology quantified in terms of watts per kilogram.

The researchers identified three high-value markets, each with a potential to cumulatively generate a gigawatt (GW) of electricity—at a price above $1 a watt—over the next 10 years:

Aerospace and unmanned aerial vehicles – Powering satellites is driven by extremely high launch costs; whereas, there is an increasing desire to keep drones aloft for very long periods. For both of these applications, limited space makes efficiency and weight critical and cost secondary. A key player in this market is III-V PV, but while highly efficient it’s also too expensive for many applications.

Portable charging – Making it easy for one person to install or move a portable charger is driving the need for PV technology that’s efficient and flexible. Finding the correct balance between those requirements and cost could put millions of units into service by the military, disaster relief workers, and recreational users.

Ground transportation – The integration of PV in electric vehicles will compete with electricity coming from the grid, but the addition could extend the driving range. The PV would have to use smaller panels and be flexible enough to conform the contours of the roof.

The researchers identified these markets as smaller but significant and ones that will pay a premium for the added value of the technology being lightweight to support initial, low-scale production. As production increases, lower costs will follow.

The NREL team determined the lower limit for a lightweight PV device is between 300 and 500 grams per square meter. Below that would reduce reliability, durability, and safety. A lightweight module on the lower side of that range could generate more than a kilowatt of electricity from something that weighs as little as a six pack of soda. Conventional modules, even without the additional weight from the mounting equipment, might require 150–200 pounds to generate this much power.

— Solar Builder magazine

Stanford researchers working on rooftop PV array that also cools buildings efficiently

Stanford solar professor

Professor Shanhui Fan and postdoctoral scholar Wei Li atop the Packard Electrical Engineering building with the apparatus that is proving the efficacy of a double-layered solar panel. The top layer uses the standard semiconductor materials that go into energy-harvesting solar cells; the novel materials on the bottom layer perform the cooling task. (Image credit: L.A. Cicero)

Stanford electrical engineer Shanhui Fan wants to revolutionize energy-producing rooftop arrays.

“We’ve built the first device that one day could make energy and save energy, in the same place and at the same time, by controlling two very different properties of light,” said Fan, senior author of an article appearing Nov. 8 in Joule.

Today, such arrays do one thing – they turn sunlight into electricity. But Fan’s lab has built a device that could have a dual purpose – generating electricity and cooling buildings.

The sun-facing layer of the device is nothing new. It’s made of the same semiconductor materials that have long adorned rooftops to convert visible light into electricity. The novelty lies in the device’s bottom layer, which is based on materials that can beam heat away from the roof and into space through a process known as radiative cooling.

In radiative cooling, objects – including our own bodies – shed heat by radiating infrared light. That’s the invisible light night-vision goggles detect. Normally this form of cooling doesn’t work well for something like a building because Earth’s atmosphere acts like a thick blanket and traps the majority of the heat near the building rather allowing it to escape, ultimately into the vast coldness of space.

Check out the 2018 Solar Builder Projects of the Year!

Holes in the blanket

Fan’s cooling technology takes advantage of the fact that this thick atmospheric blanket essentially has holes in it that allow a particular wavelength of infrared light to pass directly into space. In previous work, Fan had developed materials that can convert heat radiating off a building into the particular infrared wavelength that can pass directly through the atmosphere. These materials release heat into space and could save energy that would have been needed to air-condition a building’s interior. That same material is what Fan placed under the standard solar layer in his new device.

Zhen Chen, who led the experiments as a postdoctoral scholar in Fan’s lab, said the researchers built a prototype about the diameter of a pie plate and mounted their device on the rooftop of a Stanford building. Then they compared the temperature of the ambient air on the rooftop with the temperatures of the top and bottom layers of the device. The top layer device was hotter than the rooftop air, which made sense because it was absorbing sunlight. But, as the researchers hoped, the bottom layer of the device was significant cooler than the air on the rooftop.

“This shows that heat radiated up from the bottom, through the top layer and into space,” said Chen, who is now a professor at the Southeast University of China.

What they weren’t able to test is whether the device also produced electricity. The upper layer in this experiment lacked the metal foil, normally found in solar cells, that would have blocked the infrared light from escaping. The team is now designing solar cells that work without metal liners to couple with the radiative cooling layer.

“We think we can build a practical device that does both things,” Fan said.

Shanhui Fan is the director of the Edward L. Ginzton Laboratory, a professor of electrical engineering, a senior fellow at the Precourt Institute for Energy and a professor, by courtesy, of applied physics. Postdoctoral scholars Wei Li of Stanford and Linxiao Zhu of the University of Michigan, Ann Arbor, also co-authored the paper.

The research was supported by the Stanford University Global Climate and Energy Project, the National Science Foundation and the National Natural Science Foundation of China.

— Solar Builder magazine

Caterpillar to start selling Cat-branded SunPower solar panels through its distribution network

Cat Hybrid Energy Solutions - Shingled Cell Solar Panels
SunPower is now providing high-efficiency SunPower Performance Series (P-Series) solar panels under the Caterpillar brand. Offered as part of the Cat Hybrid Energy Solutions suite, the monocrystalline, shingled-cell Cat PVC395 MP solar panels are currently available through the Cat dealer network in Southeast Asia, Africa, South America, and the Middle East.

Providing efficiency, performance and dependability, Cat PVC395 MP solar panels are rated at 395 watts per panel and achieve efficiencies of over 19 percent through an innovative shingled-cell design with multiple redundant paths for electricity flow. This eliminates many of the reliability challenges of traditional front-contact solar panels. Additionally, the panels use a unique parallel circuit architecture that significantly limits power loss from shade and soiling.

“Backed by SunPower’s product and power warranty, the P-Series solar panel technology offered through our relationship with Caterpillar can generate up to 32 percent more energy than conventional panels in the same space over 25 years,” said Peter Aschenbrenner, executive vice president for SunPower. “Our technology is the most sold shingled-cell solar panel in the world, maximizing production and delivering long-term value. We’re pleased to collaborate with Caterpillar, an exceptional brand with a strong commitment to sustainability.”

Check out the 2018 Solar Builder Projects of the Year!

Cat PVC395 MP solar panels are the latest addition to the Cat Hybrid Energy Solutions suite, an innovative lineup of power systems that combines environmentally friendly solar panels, state-of-the-art energy conversion and storage technologies, and advanced monitoring and control systems with Caterpillar’s traditional line of reliable power generation equipment.

“SunPower shares Caterpillar’s commitment to developing an impressive portfolio of technologies with proven durability and performance in the field,” said Joel Feucht, general manager in Caterpillar’s Global Power Solutions Division. “By expanding our global solar offering, the world-class Cat dealer network can better serve the growing customer demand for cost-effective solar energy, backed by the reliable power of Cat standby- or prime-rated generator sets.”

The Cat Hybrid Energy Solutions technology suite is designed to reduce fuel expenses, lower utility bills, decrease emissions, and reduce the total cost of ownership while increasing energy resiliency in even the most challenging environments. Key offerings in the Cat Hybrid Energy Solutions suite include:

• The Cat Master Microgrid Controller (MMC), which keeps loads continuously energized with high-quality power at the lowest cost by managing the flow of power from every source in the system;

• Cat Connect Remote Asset Monitoring, which offers real-time collection and remote monitoring of site performance data in Cat Microgrid applications; and

• Cat Bi-Directional Power (BDP) inverters, which provide real and reactive power with grid-forming and grid-following capabilities.

— Solar Builder magazine