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Solar Tracking Systems Gain Ground

It sounds obvious: put solar panels on a movable mount to follow the sun and catch as much sunlight as possible. But applying solar trackers to a project is not clear cut. Developers not only have to consider cost and location but the type of tracker that best suits the project. Yet as innovations in technology continue, trackers are starting to play a larger role in the industry.

Fixed, Single or Dual

Solar panels are typically mounted at a fixed angle. Such systems have few parts, so are less costly than those with trackers and have fewer operations and maintenance (O&M) considerations.

Single-axis systems track the sun east to west as it moves across the sky, allowing them to increase system performance by 20 percent or more over fixed systems in areas of high insolation. Dual-axis trackers angle through both the x and y axes, typically generating about 8 percent-10 percent more energy than single-axis types, depending on location.

A major consideration when using trackers is land use. They generally take up much more land than fixed systems because their movement can create shadows which can affect neighbouring panels, so they must be spaced appropriately. According to MJ Shaio, senior analyst at GTM Research and co-author of the report Solar PV Balance of System (BOS) Markets: Technologies, Costs and Leading Companies, a typical fixed-tilt system usually uses about 1.6 to 2.4 ha of land per MW, while a single-axis tracker can use anywhere between 1.8 and 3.0 ha/MW.

Tracking systems maximise potential output but they also come with higher capex and opex considerations. Increased land requirements together with more sophisticated technology hike initial development costs while the requirement to maintain motors and control systems also pushes up O&M expenditure.

"The pros of trackers are more energy harvest for the same amount of panel," explains Shaio. "Per panel you get more kilowatt hours, which is great. However, there is a little bit of a trade-off. Trackers are more expensive because now you have moving parts. Instead of something that is just sitting on the ground you now have a motor that moves the panels. O&M costs will be higher, as well. The motor needs to be maintained throughout the life of the tracker."

Scott Dailey, tracker project manager at First Solar, agrees. Dailey argues that dual axis trackers are generally only seen deployed in markets with high feed-in tariffs (FiTs), where increased revenues derived by maximising a site's KWh output can offset these higher O&M outgoings.

Reliability Concerns

When tracker technology first started to hit the mainstream in solar development, some systems suffered from reliability issues. Because of the moving parts and general lack of long-term, tested experience, the solar industry tended to shy away from trackers.

According to Dailey, during the FiT boom in Europe many projects utilised dual-axis trackers with poor reliability, which led to high O&M costs. Sometimes these systems can have compounding or cascading failure modes, which can be difficult to troubleshoot and require heavy equipment to repair, he says. Shaio notes that, as recently as even just a few years ago, the only people willing to use trackers were those that were also willing to take on a lot more risk. However, trackers are starting to become the norm, especially in places with high solar insolation.

"There are always going to be bankability and viability concerns," says Shaio, "especially for new vendors, even if they have a track record in Europe. But now if you are siting a project anywhere with high irradiation, you're definitely going to think about and consider trackers," says Shaio.

A Blossoming Market

In the past several years, tracking technology has made some drastic improvements. Equipment and O&M costs have come down and standards are higher. And now that there are a lot more projects in the field that use tracker technology, it has become a much more bankable aspect of a solar project, and developers are more comfortable using it. A clear indicator of these progressive changes is First Solar's 2011 acquisition of RayTracker.

According to Shaio, the acquisition was perplexing at the time because thin-film projects typically wouldn't use tracker technology. Due to its lower efficiency, thin-film needs more land area to reach a certain capacity target, and when you add trackers to the mix, you start to eat up even more land. But in hindsight, Shaio thinks, First Solar made a smart move that fits well in its project portfolio.

"[First Solar] typically [develops projects] in wide areas where space constraint is not a concern, so in retrospect it was a pretty good move by them," explains Shaio. "They have started to roll out the tracker technology fairly aggressively."

The acquisition also had lasting effects on the overall tracker market. When RayTracker was acquired, there was a relatively small number of companies in the field, so very few options were left for third-party developers. "It was great for companies like Array Technologies because they had less competition, but not so great if you were a developer trying to diversify for your vendors or get better pricing through competition," says Shaio.

Recently a few European companies – DEGERenergie and Mecasolar – have tried to enter the North American tracker market and take advantage of the low competition and growing demand.

Finding a Niche

Although single-axis trackers seem to be dominating the market, some dual-axis companies have found their niche.

"The issue with dual axis at this point is basically that the added generation from upgrading from single to dual-axis doesn't economically pan out in terms of the extra materials and costs," says Shaio. "There are certainly players in the market that are still doing dual axis – AllEarth Renewables has one – and most CPV companies still in the game are typically using dual-axis tracking, but single-axis are more preferred."

Dual-axis players have found success in smaller-scale markets. Dailey says much of that success comes from consumers that may not be as economically driven, such as corporates that have a goal to offset as much consumption as possible, or those that favour energy output rather than the lowest levelised cost of energy.

Andrew Savage, director of communications and public affairs at AllEarth Renewables, says his company focuses its dual-axis trackers on everything from residential to 2.2 MW farms and has built its following in the northeastern US, not an ideal location for tracking systems. "The nice thing is that our trackers have been tested and proven in some harsh conditions, and that is helpful for financiers," he says.

Dual-axis systems are more attractive in areas with production-based incentives, like FiTs, according to Savage. And now AllEarth has its eye on the blossoming solar leasing market. Many potential leasing customers are unable to take advantage of support programmes because their roofs are not viable for solar. Savage says that AllEarth provides an attractive option for these customers with its ground-mount system, and, since the majority of its existing customers are residential, leasing would be a natural fit.

"Considering the amount of solar that is sold through leases, it's a market that you can't not be in," he adds.

Changing the Game

Another dual-axis tracker manufacturer is making waves with an entirely new concept. Wasiq Bokhari, CEO and founder of QBotix, believes his new technology can significantly increase margins and allow for easier installation and increased deployment.

The QBotix system consists of 200 trackers, which total about 300 kW, and two robots, one primary and one backup, which travel on a steel monorail to each tracker. The monorails also contain two charging points for the robots. A robot travels along the rail every 40 minutes to adjust each tracker individually throughout the day. The rail also carries the system's wiring, eliminating the need for trenching.

The QBotix system uses less steel – a major price driver for tracking systems. According to Bokhari, the system is roughly half the cost of dual-axis trackers and the same cost as single-axis. "Because of that price parity, we are able to achieve an LCOE reduction of up to 20 percent compared with fixed systems," he adds.

Bokhari says the robot is made of water- and dust-resistant components, and the system is also weather-resistant. It can withstand high wind loads for the project's 20-25 year life, while the robot can withstand temperatures from -30°C to 60°C.

The robot collects performance and reliability data that allows it to optimise the performance of each tracker, and ultimately the entire system. It also contains built-in GPS sensors, memory capabilities and wireless communications. If the robot malfunctions, the backup immediately takes its place, which means there is no tracking loss. The robots are also easily replaceable.

The system comes preassembled and can be used with any standard foundation and solar panel. And because it is much lower to the ground, heavy machinery is not necessary for installation.

Shaio thinks Qbotix offers a promising technology but its biggest hurdle to get to market will be convincing engineers and financiers that it is reliable and will be around long-term.

"It's a brand new technology, and that tends to make a lot of financiers really nervous," says Shaio. "Banks aren't risk takers, they want something that has been installed out in the field in gigawatt scales. Convincing the market that the product – and the company – is going to be around for 20 years will be their biggest challenge."

But innovations like QBotix may be exactly what the solar industry needs to prosper. Since balance-of-systems costs account for roughly half of the entire system, trackers may play a large role in cutting costs.

Lead image courtesy QBotix

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