Bifacial Breakdown: Know when and how to use these dual-sided PV panels

mission solar

Mission Solar Energy N 72 Bifacial Module with Power Boost. Class Leading 330-W power output, up to 400 W with bifacial boost.

Bifacial modules are like the sports cars of solar modules; they boast industry-leading efficiency breakthroughs while upholding unsurpassed aesthetic standards. Frameless bifacial modules showcase some of the highest power efficiency outputs in the solar industry because they absorb light from both sides to increase energy yield.

Residential Applications

For residential solar projects, frameless modules are popular when space is limited. For example, many residential customers supplement their backyard pergola with bifacial modules to provide energy to their homes. This provides energy production from a watertight awning that provides partial shade to cool the space underneath in the summer. Tempered double glass and rugged frameless modules require no additional grounding which further reduces the cost of installation and hides backsheets and grounding hardware.

Commercial Applications

While bifacial frameless module aesthetics play a role in commercial solar, the driving force behind their design selection is set apart by their 10-20 percent energy boost. For example, a reflective white Thermoplastic polyolefin roofing membrane (TPO) reflects light to the backside of the module to generate up to 20 percent more electricity as a framed module. Furthermore, when paired with DC Tigo or Solaredge optimizers, these modules maximize usable surface area with custom length strings and shade mitigation.

Racking

One of the most common questions from solar integrators who are new to frameless modules is how to rack them. Luckily, there are options. One example is racking manufacturer IronRidge’s collaboration with Sunpreme, one of the leading manufacturers of frameless bifacial modules, to produce the Ironridge Frameless Clamps. These clamps can rack modules in perpendicular and parallel orientation. The rubber fitting located on the inside of the clamps protects the double glass framed module.

For solar designers prioritizing clean aesthetics and top power density, frameless bifacial modules offer a combination of form and function.

Mission solar bifacial module

Since August 2015, Mission Solar has been operating an R&D test-bed at its San Antonio headquarters. Testing conditions are designed to mimic traditional utility-scale installation with dual-axis trackers and no modification to ground conditions. One year of results have shown a bifacial output increase of 7-17 percent over monofacial installed with identical conditions. MSE is currently also gathering data using single-axis and fixed-tilt trackers, as well as experimenting with various ground materials. Research has shown that with optimized conditions bifacial increase can be up to 30 percent or greater.

Charlie Saginaw is an account manager for Civic Solar.

— Solar Builder magazine

Tilt in Action: Meet the Fourth Generation Tracker from AllEarth Renewables 

Not all tracking systems need acres of land. All Earth Renewables offers an alternative to rooftops for those doing residential and small C&I work. Now on its Generation 4 Solar Tracker, AllEarth is building on the strengths and history of the first three generations. Here is what’s changed:

Structure

Made from a single-piece steel tubular axle for a sleeker look and lower part count, the biggest change is in the move from hydraulics to electrical motion actuators for tilt and yaw. “This eliminates dealing with hydraulic fluid,” according to mechanical engineer Tim Hoopes. “The electrically driven Planetary Gear Motors have a helical first stage to minimize noise for smooth and quiet operation.”

For yaw, power to the motor is ramped up and down by a pulse width modulation (PWM) algorithm in the control system to minimize impact loading for smooth operation and long life. Hoopes says this is also more energy efficient with all controls and operation using less than 1 percent of the energy production.

A custom linear actuator is used to achieve the tilt motion. The actuator design uses a large diameter ACME threaded rod for column strength.

RELATED: Why solar is a ray of hope for struggling retail industry

“We have married the strength of the hydraulic cylinder with the reliability of electric drives,” Hoopes says. “The motor is the same as the yaw system for a low part count, and a tilt feedback sensor allows for greater positional accuracy.”

Gen 4 also has continuous operation during a grid power outage. It will always go into wind hold (high wind speed shutdown where the tracker goes flat to survive hurricane force winds) since all controls are run off the 24-volt DC battery backup. The batteries are charged from the tracker PV modules with redundant chargers on two PV strings.

The inverter is mounted lower down on the mast for improved accessibility and wiring. Gen 4 also allows installation of the inverter in locations away from the tracker, which is cool when using a larger three-phase string inverter for combining two to three trackers.

Software

For Generation 3, AllEarth Renewables used a modular approach on the circuit board designs for easier installation and removal in the unlikely event of a board failure. According to Seth Maciejowski, embedded systems engineer, on the internet gateway they use a “call in only” architecture that makes installation on most customers’ networks simple and avoids complicated TCP/IP configuration.

“The fourth generation tracker integrates the communications functions into the tracker using cellular and WiFi technology to put more performance and debugging information into the hands of customers and dealers, and it more closely ties systems to our BRIGHT solar monitoring solution,” Maciejowski says. “We’ve moved to a quieter electric drive system for both yaw and tilt actuators to provide variable speed operation and battery backup for grid outages and off grid applications. Through proprietary hardware, we are able to measure DC string power directly, which will be included in the data stream provided to the BRIGHT solar monitoring solution.”

— Solar Builder magazine

Shave and a rate cut: How solar + storage solutions are shaving peaks, saving big bucks

shave and a rate cut

Shaving the peaks off commercial and industrial (C&I) electric bills is the top revenue stream for energy storage systems, and given the trend in increasing utility charges for time-of-use consumption, peak shaving can pay for a system in as little as three years, system providers say.

Just how high the peaks need to be in order to justify the investment in an energy storage system varies with geography and jurisdiction, but in general, demand charges of $15 to $20/kW or more are clear candidates, says John Merritt, the director of applications engineering at Ideal Power.

“The vast majority of converters we sold for storage systems in the past year went to California, with eight out of 10 used in applications for peak shaving,” Merritt says. “With the California incentives and the federal tax break, C&I customers can get a payback in as little as three years and in other cases in four or five years.”

A $15/kW demand charge threshold for economic feasibility also necessitates a 50-kW monthly usage level within the peak charge range, suggests Ellen Howe, VP of marketing and corporate development at JLM Energy, based in Rocklin, Calif. Her colleague, Nate Newsom, VP of enterprise sales, says, “Commercial entities that spend 3 percent or more of their monthly budget on electricity and/or experience 40 percent to 50 percent [higher than normal] demand charges typically are a good fit for energy storage.”

The C&I market is virtually untapped

Analyzing the C&I market for energy storage usefulness, the National Renewable Energy Laboratory in Golden, Colo., started with the assumption that demand charges of $15/kW or higher typically result in favorable economics for energy storage projects. Then, counting rooftops, NREL determined that “Of the nearly 18 million commercial utility customers in the United States, almost 5 million of them are exposed to, or could be exposed to demand charges of $15/kW or higher that would indicate cost-effective opportunities for energy storage.”

While not every potential C&I customer will bite the bullet for a stand-alone energy storage system, aggregation through community solar projects, or virtual power plants (VPP), is increasingly an opportunity.

Tesla is among the storage providers that is now active in community solar, with a high-profile October rollout of its commercial-scale Powerpack system at Puerto Rico’s Hospital del Niño, a children’s hospital in San Juan. As of April, Tesla had provided commercial Powerpacks and residential-scale Powerwalls to over 600 locations, with the count rising daily. The company has been quoted stating a goal of providing up to 40 percent of the island’s power storage needs via community solar system build-outs.

One new provider of VPP services is solar converter maker SolarEdge Technologies, which in May announced a solution for grid services and virtual power plants, thanks to its recent acquisition of Gamatronic Electronic Industries. The solution includes grid services of aggregative control and data reporting that enable the pooling of PV and storage in the cloud for the creation of VPPs.

demand charge example

Fig 1. Example of the steep savings achieved just through shaving peak demand.

Storage + trackers (plus pumps, plus…)

A relatively new storage configuration for C&I customers is the use of storage with solar trackers, like the 1.1-MW project at the Maharishi University of Management in Fairfield, Iowa. This project will use the NEXTracker NX Flow integrated solar-plus-storage system, in combination with an Ideal Power SunDial Plus converter and a Vanadium flow battery. The project is NEXTracker’s first large-scale installation of the NX Flow solution.

Another budding C&I application for storage is with water authorities, which can typically generate energy from solar for less than it costs to pump water uphill for a discharge to a generator turbine. The San Diego County Water Authority, for example, won $1 million from the California Public Utilities Commission to install intelligent energy storage that will tap the energy from solar panels already installed at the SDWA’s Twin Oaks Valley Water Treatment Plant.

The SDWA energy storage project, being operated by Santa Clara-based ENGIE, is expected to save an estimated $100,000 per year by storing low-cost power for later use during high-demand periods for peak shaving. The storage will help the plant cope with its highest energy use period, during peak afternoon hours. ENGIE acquired majority control of energy storage management software leader Green Charge in 2016.

RELATED: Solar + Sharing: Connect groups of homeowners, renters via one solar + storage network 

The backbone of storage: data crunching

It is tricky enough to coordinate a community solar or VPP operation, providing power on demand to participants and storing the rest until the utility calls for help. But knowing precisely what times, and advising customers as to when it is most optimal to use grid energy, or substitute with storage, is another matter, thanks to U.S. utility rate mayhem.

NREL notes that “There are almost 3,500 electricity providers in the United States, and each one has their own set of tariff sheets, rate structures and pathways for compensating non-utility-owned energy generation.” Add a dynamic dimension of rate evolution arising from rate cases, and it becomes a bit difficult to keep up with when it is most economic to use how much power.

Here the data crunchers enter the fray. Stem, for example, recently launched its Athena analysis product, which uses artificial intelligence to learn, predict and optimize energy in real time. Athena collects data at a rate of 400 megabytes per minute to continually fine-tune its algorithms. The system also has learned from operating systems for over 5 million hours, from processing nearly 200 million data intervals and from running over 35 million project simulations. As a result, the system decides and tells the battery when to store and to discharge power, responds to demand response opportunities and methodically shaves peak utility rates.

Stem has working relationships with eight utilities thus far and expects that number to grow significantly as the company helps shave peak demand, which is costly on both sides of the transformer. Stem has been dispatching batteries into California’s wholesale energy markets where it responded to more than 600 calls from state grid operator CAISO last year, according to the company.

On top of new legislative challenges, the industry has faced high and growing customer acquisition costs over the past few years. According to GTM Research, customer acquisition costs on average now represent a disproportionate 17 percent of the total system cost. This is where a new service from Urjanet, a global leader in utility data aggregation, comes into play. Its new Utility Data for Solar, a data-as-a-service solution that provides on-demand access to residential and commercial energy usage, cost and location data from more than 900 electric utilities in over 15 countries. Urjanet Utility Data for Solar enables a more cost-effective, customized approach to selling solar systems that allows vendors to effectively focus on the needs, requirements and situation of each residential or commercial buyer.

map of demand charges

Fig 2. Here’s where the harshest demand charges are across the U.S., courtesy of NREL.

Storage as a service emerges

When solar leasing became popular, the common knowledge about actual savings from such arrangements was about 15 percent of a residential utility bill, if that. With C&I customers, the savings opportunities are as high as the sky or at least whatever the utility bill looks like pre-storage.

JLM Energy is one of the latest energy storage solution providers that offers financing for energy storage customers through a $25 million project financing fund. The company uses a lease structure to achieve shared savings on a monthly basis for 20 years, with no upfront cost. JLM owns, maintains and guarantees system performance.

Stem has long been financing storage solutions, and now has a $500 million investment pool from which it can draw to finance a project, thanks to a host of private sector investors, including the Ontario Teachers’ Pension Plan.

Wall Street may not have climbed onto the PV wagon when the industry began to mature, but the storage peak-shaving proposition apparently seems as clear and understandable to such investors as the bottom line of the utility bill.

Charles W. Thurston is a freelance writer covering solar energy from Northern California.

— Solar Builder magazine

Tracking Trackers: We look at what’s new with these seven solar trackers

What are you looking for in a tracker? Longer rows with fewer spans? A two-up bifacial module setup? A simple central drive configuration with reliable bearings? More self-powered options? There are a lot of trackers in the segment, and we wanted to highlight some of the cool, innovative features outside of the market share leaders that reduce costs, ease installation or improve reliability.

Arctech

arctech

Three tracker styles to match every solar site

Arctech offers three tracker designs: The Arctracker Pro is its centralized tracker with push-pull design that is the best for flat land. The SkySmart is a single-row design with two modules in portrait that has fewer posts and is perfect for bifacial modules, and the SkyLine is a single-row design with one module in portrait.
Arctech makes the majority of its products with the support of two enormous factories, with a third on the way in 2019, to better control costs and quality.

Key hardware

  • All of Arctech’s trackers have its new D-shaped torque tube that adds stability and saves material.
  • Single-row trackers are powered from the string rather than from the batteries.
  • A beefy bearing was recently added that can handle a 20 percent N-S slope and stop the translation of weight.

Software

“Most of what we are doing is ensuring interfaces to client’s SCADA systems,” says Guy Rong, president of Arctech Solar. “We have a number of alarms in the rare case something happens to the system. Beyond this we are building software to create more accuracy on a row-by-row basis. We will announce when this is available.”

Case study

A 172-MW project in Telangana, India, had three main challenges that were solved by the design of the Arctracker Pro.

Challenge 1: Rough terrain and uneven slope. Solution: Arctech took advantage of special linkage and different post lengths to offset land contour variations and, at the same time, keep the high density of PV modules in available land and maintain high energy yield. Moreover, tracker sizes were specially designed to make best use of corner areas of land.

Challenge 2: High wind. Solution: Arctech Solar reinforced the tracking system by adding 25 percent more dampers to ensure stability and reliability of general operation and avoid damages caused by strong wind.

Challenge 3: Installation within timeline. Solutions: Installing 172 MW at a single site within the timeline was a challenging task for the EPC. In India, it’s not always easy to find skilled man power in remote areas. To solve these issues, the Arctech engineering team collaborated with the EPC to finalize installation phases well before shipping. Posts were shipped first to make sure the civil work started early while Arctech’s project managers gave tutorials on demo tracker installation so that all teams could start work simultaneously.

Nclave

nclave

Recently acquired by TrinaSolar, this international tracker has beefed up its design

Spain-based Nclave keeps on expanding. Founded 12 years ago by the Clavijo Family, it integrated with MFV in 2017. Nclave has installed over 2.5 GW worldwide. Earlier this year, the company teamed up with Trina Solar, a Chinese supplier of global solutions for the solar sector, to be a part of its TrinaPro utility-scale solution, which eventually led Trina to acquire a controlling interest in Nclave.

Structure

Nclave has developed and patented a module mounting design, the Nclave Clamp, that reduces assembly time of modules by more than 75 percent with as low as 50 manhours per MW. It also lessens the weight of the material by more than 30 percent. It includes UL-compliant integrated grounding features and has been load tested to UL and IEC standards.

Nclave separates the tracker assembly from the module assembly process to ease installation. The registered purlin allows the system to be pre-assembled on the tracker so modules can be installed with only a nut driver. Installers get rid of dedicated hardware for module installation (no more clips, bolts or rivets) as the U-bolt brackets secure module, purlin and clamp all together with just two nuts: a sandwich-like concept.

Software

The Nclave tracker controller is part of smart PV solution TrinaPro. The tracker controller is connected with the inverter in order to boost energy yield production: the optimized matching among components and the “Edge Computing” algorithm integration of TrinaPro can improve system stability with higher power generation.
The controller is empowered with a smart O&M system on a cloud platform that analyzes and processes data to optimize the system’s operation model and ensure the system runs smoothly and efficiently.

Solar FlexRack

solar flexrack

We featured this in more detail right here.

Tough, reliable, and cost-competitive, Solar FlexRack introduces their new, advanced TDP 2.0 Solar Tracker for commercial and utility-scale ground mount solar installations. The TDP 2.0 Tracker’s new BalanceTrac design offers more modules per row (up to 90), a rotational range of up to 110° and is compatible with 1,000V and 1,500V crystalline and thin film modules. This solution allows for shorter piles and lower per-unit fixed costs for balance of system savings. The combination of complete project support services and this next-generation technology enables solar power plants to increase energy yield while significantly reducing project risks. The results are cost savings across your solar project budget.

Soltec

soltec

Smartly designed structure offers slick wire management

Soltec, a manufacturer and supplier of single-axis solar trackers and related services, has installed its trackers all over the globe for more than a decade now, but the company says 2017 was its best year so far, showing over 200 percent revenue growth. The strategic move to the United States in 2015 has coincided with additional market share in 2017, amid market uncertainties and strong competition.

Structure

The DC Harness StringRunner wire management solution is a proprietary standardized component of Soltec’s SF7 tracker. It performs the functions of combining fused PV source circuits and cabling a homerun trunk circuit, all enclosed within the tracker torque tube, to a DC power switch for off-take. It eliminates the traditional fused combiner box and other cable management materials and controls the power output of eight trackers typically around 240 kW.

Soltec says the cost benefits come from the reduction of materials and related operations in manufacturing, power plant design, purchasing, supply and installation. The net cost benefit is a 30 to 35 percent reduction of installed first-cost compared to the traditional exposed installation of bundled copper wire circuits with a traditional combiner box. Installation labor is reduced by 75 percent thanks to less material and fewer manual operations including wire connections.

There are yield-gain benefits too with a reduction of IR cable losses, reliable low-resistance connections and factory dimensioned trunk cable sizing. The elimination of cable-management backside shading increases tracker compatibility with bifacial module technology.

Software

Comparative tracker yield-gain elements are both standard and site-dependent. Principal to site-dependence is asymmetric backtracking control to modify tracking position in the case that terrain irregularities cause inter-row shading in morning and afternoon hours, a case that is avoidable on flat terrain.

Soltec’s TeamTrack asymmetric backtracking control solution achieves both yield-gain and cost reduction benefits in tracker technology, achieving up to 6 percent yield-gain over the alternative of standard tracking on irregular terrain, and enabling cost reduction of earth-grading on contours and steps. The TeamTrack differs from other backtracking solutions that incorporate an auxiliary PV module and feedback response mechanisms that can add cost and vulnerability by instead performing the task straightforward with programmed operation and robust tracker position control.

The TeamTrack control algorithm works with NREL sun position data versus programmed constants of local irregularities (that never change) to calculate and execute backtracking movements and avoid inter-row shading. TeamTrack is part of comprehensive tracker positioning control that includes sensing and response to cloud cover, snow cover, standing water level and wind regime.

Schletter

schletter

New tracker product with self-locking mechanism now available

Although the U.S. arm of Schletter filed for bankruptcy, the Germany-based headquarters is still chugging along. At this year’s Intersolar Europe, Schletter Group presented its new tracking system.

Hardware

The core feature of the new Schletter tracker is that it combines the stability of a fixed mounting system with the additional yields of a tracking system. This is achieved by the drive concept: While most other tracking systems use hydraulic dampers or similar supporting structures to mitigate the vibrations and torsional forces caused by the wind, this Schletter system features a drive system with a self-locking mechanism. Each post locks as soon as the row has stopped moving. This newly-developed and soon to be patented drive system fully eliminates vibrations over the entire row which can be caused by wind. Therefore the system, while at rest, has the properties and durability of a fixed mounting system and is designed to withstand wind speeds of up to 161 mph. It thus completely avoids the dangerous galloping effect.

The second feature that stands out is its efficiency, achieved through its large wing-span and ground cover ratio. Each row can be up to 393-ft long and is driven by one centrally located motor. At 13 ft in width, each row is wide enough to hold either two panels oriented vertically or four horizontally, thus up to 574 sq yds of solar array can be installed per row and motor. This allows operators to make optimal use of the available land and a ground cover ratio of more than 50 percent can be achieved.

Software

The tracker has a rotational range of 60 degrees and is controlled through wireless technology, which completely obviates expensive wiring for both power supply and communication. The motor and the control systems are selfpowered by a dedicated PV panel in each row with a battery pack. To make O&M easier, mechanical connections between the rows have been deliberately avoided. This allows unhampered vehicle access between the rows, for instance during servicing and maintenance work.

GP JOULE

gp joule

GP JOULE’s single-axis tracker passes 20-year reliability test

The PHLEGON single-axis tracker from GP JOULE Canada Corp. passed a series of accelerated life-cycle tests conducted by the Southern Alberta Institute of Technology (SAIT) in Calgary. The Institute’s Green Building Technology Lab and Demonstration Centre confirmed PHLEGON’s long-term reliability within a wide range of environmental conditions and proved its performance in extreme northern climates. SAIT’s Accelerated Life Test Report shows that GP JOULE’s active tracking technology provides proven results in the Northern Canadian and U.S. markets where fixed-tilt PV has been dominant.

SAIT cycled PHLEGON’s mechanical components continuously 7,305 times over a 19-day period to simulate two decades of functionality. PHLEGON initially underwent the tests without environmental factors, and then went through another round that simulated extreme conditions including grit, freezing rain and sleet. The test included a deep freeze below -20C, confirming sensitive components function under extreme temperatures. “Freeze-thaw” tests mimicked the effects of spring and fall on the tracker, flooding moving parts with water before immediately exposing them to below-zero temperatures. The actuator, responsible for controlling and rotating the solar panels, completed both the mechanical and environmental rounds of testing — essentially 40 years without failure.

“GP JOULE wanted SAIT to test two things. First, how the system will operate in Alberta’s climate and second, what the cost of operating and maintaining the PHLEGON over a 20-year lifespan will be,” says Tom Jackman, SAIT’s principal investigator. “Our testing protocol introduced freezing conditions that were not considered in their original test plan, resulting in substantial ice buildup and additional weight. All components tested without failure.”

SunLink

SunLink Tracker

Updates strengthen the TechTrack design

SunLink’s single-axis tracker TechTrack is one of the quickest mounting systems to install, largely due to the simplicity of every component designed to eliminate inefficiencies and optimize energy production. The company is responding to the current environment, with customers looking for faster installation to keep up with their volume of solar projects and ultimately reduce field labor and associated installation costs, with some tweaks to its tracker design.

Hardware

One change is a new bearing and pivot design that arrives on site preassembled. The new and improved bearing design provides enough room in the stabilizer stroke (SunLink active damper) so that the system no longer needs to be rotated. Instead, the stabilizer mount position can be set from a measurement, saving substantial installation time. And with the preassembled bearings, installation crews can immediately install the component, saving valuable time in avoiding additional assembly of multiple parts in the field.

An additional design benefit enables drop-in torque tubes, eliminating the requirement for specialized jack equipment. SunLink also improved the durability of its pivot and bearing to withstand the rigors of construction crew handling on the project site.

“Another way we’re is reducing installation time is by revisiting our slew arm,” says Kate Trono, SVP of product, SunLink. “With a more streamlined design, we’ve eliminated the need for multiple or expensive custom tools and install kits that can sometimes add another $10,000 to a project. Our redesigned slew arm can be installed with standard tools, reducing the number of components, labor time and additional expenses.”

Feature enhancements like these may seem like small improvements, but the pay-off is big when you consider the reduction in labor, installation time and reducing your overall solar project cost.

— Solar Builder magazine

Submit your projects to our Project of the Year awards

 

Solar Builder Project of the Year awards

I started to sum up our July/August issue by saying “it’s all about innovation!” and nearly barfed. Ugh. Innovation. You know what I mean? For one, it’s a word overused to the point of being meaningless. But my gag reflex is caused more by the aura around it. Everyone wants to innovate. It is an overly sought-after objective, in my book. So much time is spent trying to innovate that we don’t invest enough time and energy perfecting what’s already working and maintaining what we all actually need. Like, endless funds and brainpower get pumped into building a car that drives itself while the plan for maintaining and improving the infrastructure underneath is left to rot.

Solar innovation is different though. It’s not just innovation for innovation’s sake. Much of the new technology and concepts have the possibility to evolve and strengthen our existing infrastructure.

The most prime example of solar’s practical innovation (SEGUE) is our Project of the Year awards. Past winners have included a large craft brewery trying to be eco-friendly, a school looking for a shading solution, a utility-scale project that provided clean power on tribal land. All of them a refreshing blend of practical problem-solving led by, well, you know what.

Submit your project this year

Any PV project, big or small — we want to hear about it. Was the installation innovative in some way? Did it help a community? Does it just look really awesome? If it stands out, it’ll qualify for our Project of the Year awards. To nominate a project (construction completion date must fall between Oct. 1, 2017 and July 31, 2018):

Step one: Click here.

Step two: Fill out the form by Aug. 31, 2018.

That’s it. From there we compile the entries and put them up for an online vote in the following categories:

  • Residential (pending enough submissions)
  • Commercial & Industrial
  • Utility-scale
  • Solar + Storage

Projects with the most votes win each category, but ALL nominees are also eligible for Editor’s Choice awards. All winners are then featured in our year-end magazine and on the site. Head here for more details and to enter.

— Solar Builder magazine